Method of roll grinding

ABRASIVE ARTICLES WITH NEW STRUCTURES AND GRINDING PROCESS

Related Applications

This application is a continuation in part of US Serial No. 10/120 969 recorded April 11, 2002 and a partial continuation of Serial No. 10/328 802, registered on 24 December 2002. The entire contents of US Serial No. 969 ° 10/120 and 10/328 Serial No. 802 are hereby incorporated by reference.

Background of the Invention The invention relates to articles or bonded abrasive tools such as grinding wheels, grinding segments, discs and hones, having novel composition of structures, methods of manufacture of such tools to create the new tool structures, and to methods of grinding, polishing or surface finishing using such tools.

Bonded abrasive tools consist of rigid composites, and typically monolithic, three-dimensional, in the form of wheels, discs, segments, set points, stones and other forms of tool, having a central hole or other mounting means on a particular type of device or machine grinding, polishing or grinding. These composites comprise three structural elements or phases: abrasive grain, binder and porosity.

The bonded abrasive tools have been manufactured in a variety of "quality" and "structures" that have been defined according to practice the art by the relative hardness and density of abrasive composite (quality) and the volume percentage of abrasive grain , binder and pores within the composite (structure).

For almost 70 years, the quality and structure of the tools were considered the most reliable indicators of the hardness of the bonded abrasive tool, the wear rate of the tool, the power requirements of rectification, and consistency of manufacture. The quality and structure were initially established as reliable manufacturing guidelines in U.S. Patent No. -A-1 983 082, allocated Howe et al. Hove describes a volumetric manufacturing method useful for overcoming the then persistent difficulties with inconsistent quality of the abrasive composites and the irregular performance of rectification. In this method, one selects the relative volumetric percentages of the three structural constituents to yield a tool with a quality referred hardness and other desired physical characteristics. Knowing the desired volume of the finished tool, the weight of the abrasive grains of batch components and binders needed to make the tool are calculated from the volume of the tool, the volumetric percentages and the material densities of the abrasive grain and binder components. In this way it was possible to create a standard structure chart for defined binder composition and in subsequent passages manufacturing, read the volumetric relative percentages from the standard diagram of the structure to manufacture bonded abrasive tools having uniform hardness of quality for a given volume percentage of abrasive grain, binder and pores. It was observed that the grinding performance was consistent from one manufacturing batch to another when the quality and structure were held constant.

For many grinding operations, controlling the amount and type of porosity in the composite, particularly the nature of permeable porosity, or interconnected, has been shown to improve the efficiency of rectification and as protecting the quality of the workpiece to machine that is ground thermal or mechanical damage.

Any three-dimensional abrasive composite consists of the sum of percentages by volume of its three constituents: abrasive grain, binder and porosity. The sum of the volume percentages of these constituents must equal 100 volume%; therefore, tools having a high percentage of porosity must have proportionally lower percentages of binder and / or abrasive grain. In manufacturing bonded abrasive tools, one can more easily achieve the percentages by relatively high volume of porosity (e.g., 40 to 70 volume%) in precision grinding tools, made with rigid binder materials, inorganic materials (for example, vitrified or ceramic binders) and relatively small grain size (e.g., particle sizes Norton grain 46 to 220) in the coarse grinding tools made with organic binding materials and relatively large grain size (e.g., Norton grit sizes 12-120 grit). Very porous abrasive composites made with larger grain sizes, and larger volume percentages of grain and organic binding materials, softer, have a tendency to sag or stratify during the intermediate stages of molding and curing of manufacturing the grinding tool. For these reasons, commercially available bonded abrasive tools made with organic binding materials are often molded to contain no porosity, and typically contain no more than 30% by volume porosity. They seldom exceed 50 volume% porosity.

Natural porosity arising from packing of the abrasive grains and binder particles during pressure molding usually is insufficient for achieving a high porosity in bonded abrasive tools. Porosity inducers, such as a ventilated alumina and naphthalene, may be added to abrasive composite mixtures of binder and to enable pressure molding and handling of an untreated porous abrasive article and producing a percentage in adequate volume of porosity in the final tool. Some pore inducers (e.g., ventilated alumina and glass spheres) will create closed cell porosity within the tool. The pore inducers of the closed cell to be added to achieve high porosity percentages prevent the formation of open channels or interconnected porosity, thus preventing or reducing fluid flow through the body of the tool, hence tending to raise the grinding forces and risk of thermal damage. Inducers of open cell pores must be removed by burning of the abrasive matrix (e.g., walnut shells and naphthalene), resulting in many manufacturing difficulties.

In addition, the densities of pore inducers, binder materials and abrasive grains vary significantly, making it difficult to control stratification of the abrasive mix during handling and molding, often resulting in a loss of homogeneity in the three-dimensional structure of the finished abrasive article. A uniform distribution, homogeneous three constituents of the abrasive composite has been considered a key aspect of consistent tool quality and, for grinding wheels, important in the safe operation of wheels at the high rotational speeds needed for grinding ( for example, surface speed of over 4,000 feet per minute (SFPM)).

The percentage by volume interconnected porosity, or fluid permeability, has been found to represent a significant determinant of more abrasive articles grinding performance than just the percentage porosity volume (see U.S. Patent No. A-5738 696 issued to Wu. The interconnected porosity allows removal of grinding waste (swarf) and passage of cooling fluid within the wheel during grinding. The existence of interconnected porosity may be confirmed by measuring the permeability of the wheel to the flow of air under controlled conditions. US Patent No. -A-5 738 697 issued to Wu mentioned high permeability grinding wheels having a significant amount of interconnected porosity (40 to 80% . by volume) to these wheels are manufactured from a mixture of fibrous particles having an aspect ratio of at least 5: 1. The fibrous particles may be filamentary abrasive grain or ordinary abrasive grains mixed with nonfibrous various fibrous filler materials such as ceramic fiber, polyester fiber and glass fiber and mats and agglomerates constructed with the fiber particles.

It has now been discovered that bonded abrasive tools can be manufactured with a relatively high percentage of porosity and a relatively low percentage of abrasive grain without sacrificing mechanical strength of the tool to wear, even if the quality of hardness tool would lead to predict relatively poor mechanical strength. For organic bonded abrasive tools it is now possible to manufacture tools at relative percentages of abrasive grain, binder and porosity that form structures unknown among commercial bonded abrasives tools. These new structures include organic bonded abrasive tools wherein the continuous phase of the abrasive composite consists of the porosity constituent. In a preferred method of creation of these new structures, a majority of the abrasive grain has been agglomerated with a binder material prior to mixing, molding and thermally processing the bonded abrasive tool.

Agglomerated abrasive grains have been reported as improving the efficiency of rectification through mechanisms unrelated to the amount or character of the porosity of the bonded abrasive tool. The abrasive grain has been agglomerated for various purposes, the most important among them allow the use of an abrasive grain particle size smaller ("grain") to achieve the same grinding efficiency as a larger abrasive grain, or to produce a more smooth surface film over the workpiece is corrected. In many instances abrasive grain has been agglomerated to achieve a less porous structure and a denser grinding tool, having more strongly bonded abrasive grains.

Grindstones of gears, very low porosity (for example less than about 5 volume% porosity) were made from vitrified bonded abrasive composites, crushed, regenerated by agglomeration of composites in an epoxy resin. These wheels of "mixing" Grinding the gears have been commercially available for many years (from Saint-Gobain Abrasive, GmbH, previously Efesis Schleiftecnik GmbH, Gerolzhofen, Germany).

US Patent No. -A-2,216,728 issued to Benner mentions abrasive grain aggregate / binder made from any type of binder. The reason for the use of the aggregates is to achieve very dense wheel structures for retaining diamond or CBN grain during grinding operations. If the aggregates are made with a porous structure, then the purpose is to enable inter-aggregate binder materials to flow within the pores of the aggregates and to make fully dense structure during firing. The aggregates allow the use of abrasive grain expenses otherwise lost in production.

U.S. Patent No. -A-3 982 359 issued to Elbel teaches the formation of resin binder and abrasive grain aggregates having hardness values ​​greater than those of the resin binder used to agglomerate the aggregates inside of an abrasive tool. Larger grinding speed and a longer life of the tool are achieved in rubber bonded wheels containing the aggregates in.

U.S. Patent No. -A-4 799 939 issued to Wetshcer refers to abrasive grain agglomerates may be eroded, hollow bodies and organic binder and the use of these agglomerates in coated abrasives and bonded abrasives. Similar agglomerates are set forth in U.S. Patent No. -A-5-039 311 issued to Bloecher, and US Patent No. -A-4 652 275 issued to Bloecher et al.

U.S. Patent No. -A-5-129 189 issued to Wetshcer mentioned abrasive tools having a resin binder matrix containing conglomerates having 5 to 90 volume% porosity, of abrasive grain, resin and filler material as the chryolite.

U.S. Patent No. -A-5 651 729 issued to Benguerel teaches a grinding wheel having a core and a discrete abrasive rim made from a resin binder and crushed agglomerates of abrasive grain of diamond or CBN with a binder metal or ceramic. The benefits of the wheels made reported with the agglomerates include high chip dead spaces, high wear resistance, the self-sharpening characteristics, high mechanical resistance of the wheel and the ability to directly bond the abrasive rim to the core of the wheel. In one embodiment, the edges used for rectification, agglomerates of diamond or CBN, is crushed to a size of 0.2 to 3 mm to form the agglomerates.

GB Patent No. -A-1,228,219 issued to Lippert mentioned grain conglomerates and binder added to a resilient binder matrix rubber. The binder now the grain within the conglomerate can be ceramic or resin materials, but it must be more rigid than the elastic bond matrix.

U.S. Patent No. A-4 541 842 issued to Rostoker refers to coated abrasives and abrasive wheels made with aggregates of abrasive grain and a foamed mixture of vitrified binder materials with other raw materials, such as carbon black or carbonates, suitable for foaming during firing of the aggregates. The "pellet" aggregated contain a greater percentage of binder than grain on a volume percentage basis. Pellets used to make abrasive wheels are sintered at 900 ° C (to a density of 70 lb / ft2; 1.134 g / cc) and the vitrified bond used to make the wheel is fired at 880 ° C. The wheels made with 16 volume% pellets were evidence in the rectification of a similar level of efficiency than that of comparative wheels made with 46 volume% abrasive grain. The pellets containing open cells to I within the vitrified bond matrix, with the relative smaller abrasive grains clustered around the perimeter of the open cells. A rotary kiln is mentioned for pre-cook raw aggregates that are bonded by the foamed and sintered subsequently to manufacture pellets.

US Patent No. -A-6,086,467 issued to Imai et al., Mentioned grinding wheels containing abrasive grain and grain grain groups with a smaller load than the abrasive grain size. The vitrified bond may be used and the filler grain may be chromium oxide. The grain size of groups is one-third or more of the abrasive grain size. The benefits include the controlled erosion of the binder and abrasive grain retention in low-power grinding operations using the super abrasive grain in which the super abrasive grain must be diluted to minimize grinding forces. Load grain groups can be formed with wax. No sintering of the groups are listed.

WO 01/85393 A1 patent issued to Adefris mentions a three-dimensional abrasive article made from abrasive composites, either carved or irregular configured to have more than one monolayer of abrasive composites. The article may contain inter-composite porosity and intra-composite porosity. The composites include abrasive grains bonded in an inorganic or organic first matrix and the abrasive article is agglomerated with a second inorganic binder material (metal or vitrified or ceramic) or organic, to form an abrasive article having about 20 to 80% by volume porosity. The preferred article contains fine diamond abrasive grain held in a first and a second glass binder and the article is used to grind the glass until a mirror finish.

Many publications have described coated abrasive tools made with bonded abrasive grain. They include US Patent -A-2,194,472 issued to Jackson mentions that coated abrasive tools made with agglomerates of a plurality of relatively fine abrasive grain and any binders normally used in coated or bonded abrasive tools. It has been reported that inorganic composite of abrasive grains of diamond, CBN and other thermally degradable abrasive grains in a fine grain metal oxide matrix are useful in coated abrasive tools (U.S. Patent No. -A-3 916 584 issued to Howard, et al.) U.S. Patent No. -A-3 048 482 issued to Hurst mentioned abrasive micro-segments of agglomerated abrasive grains cut and organic binder materials in the form of pyramids or other cut. Mitered abrasive micro-segments adhere to a fibrous substrate and used to make coated abrasives and to line the surface of thin grinding wheels. The US Patent -A- 4,311,489 issued to Kressner mentions agglomerates of abrasive fine-grained (<200 microns) and cryolite, optionally with a silicate binder, and their use in the manufacture of coated abrasives. U.S. Patent No. -A- 5 500 273 issued to Holmes mentions particles or abrasive grain composite cut precisely and a binder polymer formed by radical polymerization. Composite cut in a similar manner are disclosed in US Patent No. -A-5 851 247 issued to Stoetzel, et al. ; U.S. Patent No. -A-5 714 259 issued to Holmes, et al. ; and U.S. Patent No. -A-5 342 419 issued to Hibbard, et al., US-5 975 988, US-6 217 413 B1 and WO96 / 10471, all issued to Christianson, mention coated abrasive articles including a support and an organic agglomerated abrasive layer where the abrasive is present as shaped agglomerates in the form of cut truncated pyramid with four sides or cube.

US-A-6,056,794 issued to Stoetzel, et al. refers to coated abrasive articles having a backing, an organic binder containing hard inorganic particles dispersed within, and abrasive particle agglomerates bound to the support. The abrasive particles in the agglomerates and the hard inorganic particles in the organic binder are substantially the same size. Agglomerates may be randomly or trimmed accurately and are made with an organic binder. The hard inorganic particles may be any particles chosen from many particles of abrasive grain.

US 6 319 108 B1 issued to Adefris, et al., Refers to an abrasive article comprising a rigid backing and ceramic abrasive composites made of abrasive particles in a porous ceramic matrix. The composites are held to the backing with a metal coating, such an electroplated metal. WO 01/831666 A1 patent issued Mujumdar, et al. mentions of abrasive tools glass, rectification comprising composite diamond kept to a support with a binder resin.

Numerous patents mentioned abrasive tools comprising composite resin or other organic binder, abrasive grain. Most of these tools are coated abrasive tools wherein a resin binder is used to adhere the abrasive grain composites to a flexible backing. Occasionally metal binders or particles being eroded are used in conjunction with the abrasive composites. Representative patents in this group include US Patent No. -A-5 078 753 granted to Broberg, et al. ; U.S. Patent No. -A-5 578 098 issued to Gagliardi, et al. ; U.S. Patent No. -A-5 127 197 issued to Brukvoort, et al. ; U.S. Patent No. -A- 5 318 604 issued to Gorsuch, et al. ; U.S. Patent No. -A-5 910 471 issued to Christianson, et al. ; US Patent No. -A-6217413 issued Christianson, et al.

US Patent No. -A-4 355 489 issued to Heyer discloses a coated abrasive article (wheel, disc, belt, sheet, block and the like) fabricated from a matrix of undulated filaments bonded together at points of manual contact and abrasive agglomerates, having a void volume of about 70 to 97%. The agglomerates may be made with vitrified or resin binders and any abrasive grain. U.S. Patent No. -A-4 364 746 issued to Bitzer mentioned abrasive tools comprising different abrasive agglomerates having different strengths. The agglomerates are made from abrasive grain and resin binders, and may contain other materials, such as fiber piece, to add strength or hardness. U.S. Patent No. -A-4 393 021 issued to Eisenberg, et al., Discloses a process of making abrasive agglomerates from abrasive grain and a resin binder utilizing a sieve belt and rolling a paste grain and binder through the web to make to shape the extrusions. The extrusions are hardened by heating and then crushed to form agglomerates.

Regardless of this vast body of knowledge regarding how to make abrasive articles with agglomerated grain and to eliminate or create tool porosity, until now, no successful way to change the basic structure the composite of a monolithic agglomerate abrasive tool in three dimensions with agglomerated grain such that the quality and structure of the tool no longer dictate the performance of the correction. Nobody used the agglomerated grain to make percentage volume structure tools that were difficult to impossible to manufacture with ordinary abrasive grain in organic binders. In particular, without sacrificing mechanical strength, service life or tool performance, it has been found that relatively high volume percentages of porosity (e.g., above 30 volume%) can be achieved in bonded abrasive tools made with organic binders. Significant alterations in elastic modulus and other physical properties of both inorganic and organic bonded tools now can be achieved in the tools of the invention.

In abrasive agglomerates made ​​with organic binding materials, the binder materials have been considered as the most important factor in the quality of the structural alteration to attain a resistance or an appropriate or sufficient mechanical rigidity. Rather surprisingly, the invention allows low-grit tools to be made ​​on a range of binder contents and used in grinding operations that require high mechanical strength tools having resistance premature wear (defined as a structural tool wear that is more rapid than abrasive grain wear) In grinding operations on a large contact surface, the tools of the invention actually perform in a superior manner to tools Conventional manufactured with higher levels of binder and abrasive grain.

None of the prior art developments in agglomerated abrasive grain suggest the benefits in bonded abrasive tools of using certain agglomerated abrasive grains within an organic or inorganic bond matrix to control the three-dimensional structure of Abrasive tool chipboard. In particular, it is unexpected that these agglomerates could be adapted to adjust and to control the location and type of porosity and bond matrix within the structure of the tools of the invention.

Summary of the Invention The invention is a bonded-abrasive tool, comprising a three-dimensional composite of (a) a first phase comprising 24-48 vol% abrasive grains bonded with 10 to 38% by volume of organic binder material and less than 10 volume% porosity; and (b) a second phase consisting of 38 to 54 volume% porosity; wherein the second phase is a continuous phase within the composite, and the agglomerate abrasive tool has a minimum burst speed of 4000 SFPM (20.32 m / s).

The invention further include bonded abrasive tools comprising a three-dimensional composite of (a) 22 to 46 volume% agglomerates of abrasive grain with 4 to 20 vol% inorganic binder material; and (b) 40 to 68% by volume interconnected porosity; wherein a majority of the abrasive grains are present in the form of patterned irregular spacing within the three-dimensional composite; bonded abrasive tools have elastic modulus value that is at least 10% lower than elastic modulus values ​​for otherwise identical conventional tool a having regularly spaced abrasive grains within a three-dimensional composite ; and bonded abrasive tool demonstrated a minimum speed burst of 4000 SFPM (20.32 m / s).

The invention further includes a method for disc grinding, comprising the steps of: (a) providing an agglomerated abrasive wheel, comprising a three-dimensional composite of (i) a first phase comprising 24 to 48% by volume Agglomerate abrasive grain having from 10 to 38% by volume of organic binder material and less than 10 volume% porosity; and (ii) a second phase consisting of 38 to 54 volume% porosity; wherein the second phase is a continuous phase inside of the composite, and the agglomerate abrasive tool has a minimum speed of 4000 SFPM éclatementde (20.32 m / s); (b) mounting the grinding wheel agglomerated on a surface grinding machine; (c) rotating the grinding wheel; and (d) contacting a grinding surface of the grinding wheel with a workpiece for a sufficient time to grind the workpiece; whereby the wheel removes workpiece material to work on an effective material removal rate, the grinding wheel surface remains substantially free of grinding debris and, after grinding is completed, the workpiece is substantially free of thermal damage.

The invention further includes a deep cut in grinding method comprising the steps of: (a) providing an abrasive wheel comprising a sintered three-dimensional composite of (i) 22 to 46 volume% agglomerates of abrasive grain with 4 to 20% by volume of inorganic binding material; and (ii) 40 to 68 volume% interconnected porosity; and wherein a majority of the abrasive grains are present in the form of patterned irregular spacing within the three-dimensional composite; The bonded-abrasive tool has an elastic modulus value that is at least 10% lower than the elastic modulus value of an otherwise identical conventional tool having regularly spaced abrasive grains within a three-dimensional composite; and the bonded abrasive tool has a minimum burst speed of 4000 SFPM (20.32 m / s); (b) mounting the abrasive wheel agglomerated on deep passes grinding machine; (c) rotating the grinding wheel; and (d) contacting a grinding surface of the grinding wheel with a workpiece for a sufficient time to grind the workpiece; whereby the wheel removes material from the work piece at an effective rate of material removal and after grinding, the workpiece is substantially free of thermal damage.

Description of the Drawings

Figure 1 is a ternary diagram by contrasting the volumetric percentages of compositions of related structures, organic bonded abrasive tools standards with respect to those of organic bonded abrasive tools of the invention.

Figure 2 is a ternary diagram by contrasting volumetric percentage composition structures related, organic bonded abrasive tools standards compared to those of organic bonded abrasive tools of the invention made with abrasive grain agglomerates containing binder materials inorganic binders.

Figure 3 is a ternary diagram illustrating the range of volumetric percentage composition structures of standard inorganic bonded abrasives tools wherein those of inorganic bonded abrasive tools of the invention made with abrasive grain agglomerates containing inorganic materials and a caking inorganic binder are characterized by modulus of elasticity significantly lower values, but equivalent burst speed values ​​of the grinding wheel relative to the standard tools.

Figure 4 is a photomicrograph of the surface of an abrasive tool manufactured standard agglomerated with an organic binder, illustrating a uniform distribution of the three constituents of the abrasive composite.

Figure 5 is a photomicrograph of the surface of a bonded-abrasive tool of the invention made with an organic binder, illustrating a non-uniform distribution of the three constituents of the abrasive composite, porosity (darker areas) as a continuous phase within the composite and a reticulated network of abrasive grain anchored within the organic binder material.

Description of preferred embodiments bonded abrasives Tools

The bonded abrasive tools of the invention (grinding wheels, grinding segments, grinding discs, à.rectifier stones and sharpening stones, which is made collectively by reference tools or wheels) are characterized by a previously unknown combination of structure tool or grinding wheel and physical properties. As used herein, the term "wheel structure" refers to the volume percentage of abrasive grain, binder and porosity contained in the grinding wheel. The "quality" of hardness of the wheel means the letter designation given to the behavior of the grinding wheel in a grinding operation. For a given type of binder, the quality is a function of the porosity of the wheel, of the grain content and certain physical properties, such as density in the cured state, the elastic modulus and the jet penetration sand (the latter is more typical of vitrified grinding wheels linked). The "quality" of the wheel predicts the level of resistance to wear of the grinding wheel during the grinding and the level at which the grinding wheel perform the correction, that is to say, the power level may be necessary to use the wheel in a given grinding operation. The appointment letter for the quality of grinding wheel is assigned according to a quality scale of the Norton Company known in the trade, in which the softest grades are designated A and the hardest grades are designated Z. See, example, US Patent No. -A-1,983,082, Howe et al. By matching wheel grades, one skilled in the art can commonly substitute a new description for a known wheel and predict that the wheel new wheel will perform in a manner similar to the known wheel.

By deviating significantly and unexpectedly from these practices, the tools of the invention are characterized by changes in their monolithic composite structures, in three dimensions, in particular, in the amount and character of the component porosity, so that the quality and structure of the tool can no longer predict grinding performance.

When made with an organic binder, the tools of the invention should be formulated to produce in volume percentages of structures (e.g., porosity of above 30% by volume) which was difficult or impossible to manufacture according to the methods of the prior art. These new structures can be made without sacrificing mechanical strength, service life or performance of the tool. In a preferred method, these structures are manufactured with an abrasive grain mixture wherein a majority of the abrasive grain is in the form of abrasive grain agglomerates with organic bond material, an inorganic bonding material, or a mixture of both.

When made with an inorganic binder, the tools of the invention may be formulated to produce the same volume percentages of the structures (see Figure 3) compared to conventional tools, but of significantly lower way, that is ie, at least 10% lower for the value of the modulus of elasticity and often as much as 50% less for the value of the modulus of elasticity, without actual loss of strength. Notwithstanding this drop in hardness, the tools of the invention show speed peak values ​​commercially acceptable and significantly better material removal rates in certain grinding operations. In a preferred method, these structures are manufactured with an abrasive grain mixture wherein a majority of the abrasive grain is in the form of agglomerates of abrasive grain with an inorganic binder material.

Figures 1 to 5 illustrate the new structures of the tools of the invention. Figure 1 is a ternary diagram marked with two zones defining two sets of wheels (prior art wheels and the experimental wheels of the invention) made with organic binder material. The wheels of the prior art and the inventive wheels are equally suitable for commercial use in grinding operations, precision, surface or line, high contact, such as by grinding disc or cylinder. The conventional wheels have volume percentages of structures located in a zone bounded by 38 to 52 vol% grain, 12 to 38% by volume binder and 15 to 37 volume% porosity. In contrast, the wheels of the invention have structures located in a zone bounded by 24 to 48 vol% grain, 10 to 38% by volume binder and 38 to 54 volume% porosity. It can be observed that the inventive wheels are made with significantly less abrasive grain than the conventional wheels and contain relatively small amounts of binder and of relatively large amounts of porosity. Which can not be observed in the diagram is that the inventive wheels lie on the ternary diagram in a region where prior art manufacturing methods could not be used to make grinding wheels. The techniques of the prior art failed if the three-dimensional composite structure sagged during thermal processing, by collapsing the areas of porosity, or when the wheels of the prior art lacked sufficient mechanical strength for use safe in grinding operations.

Figure 2 is a ternary diagram illustrating two sets of wheels (prior art wheels and the experimental wheels of the invention) designed for commercial use in grinding operations in continuous line contact area, such as the rectification per cylinder. The wheels of the prior art are made of organic binder material and the wheels of the invention are made of organic binder material and abrasive grain agglomerates containing inorganic binders materials. The wheels of the invention are far superior to conventional grinding wheels on all the operating parameters of grinding operations per cylinder. The conventional wheels again have structures located in a zone bounded by 38 to 53 vol% grain, 12 to 38% by volume binder and 15 to 37 volume% porosity. In contrast, the wheels of the invention have structures located in a zone bounded by 28 to 48 vol% grain, 10 to 33% by volume of binder (the amount of the organic binder in the grinding wheel and the bonding material inorganic in the agglomerates) and 38 to 53 volume% porosity. It can be seen that the inventive wheels can be made with significantly less abrasive grain and significantly more porosity than the conventional wheels. Which can not be observed from the diagram is that the inventive wheels are characterized by much softer grades than the conventional wheels and elastic modulus values ​​lower than those of conventional wheels (when compared to volume percentages equivalent of binder material), but they exhibit significantly better grinding efficiency in terms of life of the grinding wheel removal rate of material and resistance to vibration or chatter of the grinding wheel.

Figure 3 is a ternary diagram illustrating two sets of wheels (prior art wheels and the experimental wheels of the invention) made with inorganic binding material both appropriate for commercial use in grinding operations on surface high contact, such as deep passes rectification. The wheels of the prior art and the inventive wheels both have structures located in a zone bounded by 22 to 46 vol% grain, 4 to 21% by volume binder and 35 to 77 volume% porosity. Which can not be observed from the diagram is that, in a volume percentage of identical structure, the inventive wheels have a softer grade and a modulus value less than the conventional wheels, yet the inventive wheels making demonstrated a significantly better grinding performance in terms of removal rate of material and quality of the workpiece.

Figures 4-5 illustrate the change in the amount and character of the porosity of the inventive tools relative to conventional tools. It can be seen from Figures 4 (prior art) and 5 (inventive) that the porosity (darker areas) in the abrasive composite of the inventive wheel is a continuous phase of interconnected channels. The abrasive grain and the binder appear as a reticulated network in which abrasive grain is anchored in the organic binder materials. In contrast, the conventional wheels have a substantially uniform structure wherein porosity is hardly visible and clearly present as a discontinuous phase.

Similarly, it has been observed for inorganic bonded tools of the invention that the porosity in the abrasive composite comprises interconnected porosity. The abrasive grains of the inventive wheels are clustered and spaced in an irregular manner, in contrast to the regular and uniform grain spacing in comparable prior art wheels of the manufactured with the same type of inorganic binder and grain materials. All constituents of the prior art wheels appear to be spaced in a uniform and evenly across the surface of the wheel, whereas all constituents of the inventive wheel are irregularly spaced and the structure is not homogeneous. As might be expected from an inorganic agglomerate tool (e.g., vitrified bond) and relatively small size of abrasive grains commonly used in such a tool, compared with the organic binder and larger grain sizes illustrated in Figures 5, the channels of the porosity and of the abrasive grain and the binder system are visually less distinct in the inorganic bonded tools in organic bonded tools.

Various essential properties of the bonded abrasive tools have been identified as being associated with the new composite structures mentioned in this document, including mechanical strength, elastic modulus and density.

Mechanical strength properties determine whether a composite can be used to serve as a bonded-abrasive tool in a commercial grinding operation. Because most bonded abrasive tools are used in the form of abrasive grinding wheels, mechanical strength is calculated by means of the test of the speed of the wheel burst wherein the wheel is mounted on a shaft to the within a protective chamber and then rotated at increasing speeds until the composite fails and either the grinding wheel breaks. The burst speed may be converted into a point of failure of the tensile stress according to known equations (e.g., Formulas for Stress and Strain, Raymond J. Roark, McGraw-Hill, 1965). For example, if one assumes a rotating disk with a center hole, failure occurs at the hole where the tensile stress is at a maximum.

σ = tensile stress or burst strength (psi) R = radius of the wheel (in) p = density of the grinding wheel (lb / in3) r = radius of the hole (in) ta = angular velocity (rad / sec ) k = constant (386.4) υ = Poisson's ratio (0.2) σ = 1 x [px è {^ jj (3 + υ) x R2 + (1 - ") x r2)

Hkj

Applying these relationships to a grinding wheel example, for a grinding wheel cylinder 36 X 4 X 12 inch (91.4 X 10.2 X 30.5 cm) with a density of 0.053 lb / in3 (1.46 g / cc) (containing 30% abrasive + 22% binder 48% by volume pores), if the wheel had a measured burst speed of 4000 SFPM (20.32 m / s), then:

Angular velocity = 4000 ft / min = 44.4 radians / sec = σ ^ -χ ° '° '42 ^ 386 ^) ^ 0.2 Χ 36' + ~ 0,2Χ 122)) = 2UpSÎ

If speed burst was twice as high (8000 SFPM (40.64 m / s) or 88.8 radians / sec), while the tensile stress σ = 1153 psi at the point where the composite undergoes mechanical failure.

Thus, the "strength" is defined herein as the speed of the wheel burst in feet per minute (or meters per second) for grinding wheels and, if the bonded abrasive tool is not a wheel, as the tensile stress measured at the point where the composite undergoes complete mechanical failure.

Another relevant physical property regarding bonded abrasive tools of the invention is the density of the tool. The organic bonded tools of the invention, which can be expected from the volume percentages of compositions, their new structures, are less dense than comparable conventional tools typically used in any given grinding operation. The organic bonded tools are characterized with a density of less than 2.2 g / cc, most preferably less than 2.0 g / cc, and most preferably less than 1.8 g / cc. As such, for a given grinding operation (e.g., grinding steel cylinders per disk) are about 20 to 35% less dense, and on average about 30% less dense than comparable conventional tools used in the same operation. Inorganic agglomerates tools of the invention are characterized by comparable or slightly lower densities relative to the densities of comparable conventional tools. For example, grinding wheels of the internal diameter of a conventional type generally have a density of about 1.97 to 2.22 g / cc, while comparable tools of the invention range from about 1, 8 to 2.2 g / cc. The densities of the deep pass through the grinding wheels of the invention and comparable conventional wheels extend all about 1.63 to 1.99 g / cc.

However, for the inorganic bonded tools of the invention, the elastic modulus values ​​are significantly lower, at least 10%, preferably at least 25% and most preferably 50% lower than values ​​for comparable conventional tools . For inner diameter grinding wheels, the elastic modulus of the tools of the invention ranges from 25 to 50 GPa (values ​​were determined with a Grindosonic ™ machine, according to the method described in J. Peters "Sonic Testing of Grinding Wheels "Advances in Machine Tool Design and Research, Pergamon Press, 1968) in contrast with elastic modulus values ​​of comparative tools which typically extend from 28 to 55 GPa. Similarly for deep pass through the grinding wheels, the elastic modulus values ​​for the tools of the invention range from 12 to 36 GPa, in contrast with elastic modulus values ​​of comparative tools which usually range from 16 to 38 GPa. Similarly, for tool grinders (the hard metal tool surface grinding) the modulus of elasticity of tools of the invention ranges from 12 to 30 GPa, in contrast to the modulus values ​​of elasticity of comparative tools which typically extend from 16 to 35 GPa. In general, for a given operation of correction, the more the quality of comparable conventional tool needed for this process is high, the greater the downward shift in elastic modulus value of the inorganic agglomerate tool of invention which offers equal or better performance in this operation. It follows that for a given grinding operation, the higher the volume percentage of abrasive grain in a comparable conventional tool needed for this operation is, the greater the downward shift of the value of the modulus of elasticity inorganic agglomerate tool of invention that delivers equal or better performance in this operation.

Bonded abrasive tools of the invention have an unusually porous structure of interconnected porosity of, making the tool permeable to fluid flow and the porosity, in effect, becoming a continuous phase within the abrasive composite. The amount of interconnected porosity is determined by measuring the permeability of the tool according to the process fluid of US Patent No. -A-5 738 696. As used herein, Q / P = the permeability flowing an abrasive tool, where Q means flow rate expressed as cc of air flow, and P means differential pressure. The term Q / P represents the pressure differential measured between the abrasive tool structure and the atmosphere at a given flow rate of a fluid (e.g. air). This relative permeability Q / P is proportional to the product of the pore volume and the square of the pore size. Larger pore sizes are preferred. The pore geometry and abrasive grain size are other factors affecting Q / P, with larger grit size produces a higher relative permeability.

The abrasive tools useful in the invention are characterized by higher fluid permeability values ​​than those of comparable prior art tools. As used herein, the "comparable prior art tools" are those tools made with the same abrasive grain and binding materials with the same volume percentages of porosity, grain and binder as those of the invention. In general, abrasive tools of the invention have fluid permeability values ​​of about 25 to 100% higher than the comparable values ​​abrasive tools of the prior art. The abrasive tools preferably are characterized by fluid permeability values ​​to at least 10% higher, more preferably at least 30% better than those of comparable prior art tools.

The exact parameters of the fluid relative permeability to specific sizes and shapes of agglomerates, binder types and porosity levels may be determined by the practitioner through the operation of the D'Arcy Law to empirical data for a given type of abrasive tool.

The porosity within the abrasive wheel arises from the open space provided by the natural packing density of the tool components, particularly the abrasive agglomerates, and, optionally, by the addition of a minor amount of conventional media pore induction. Suitable pore inducing media include, but are not limited to, hollow glass spheres, the spheres or hollow spheres of plastic material or organic compounds, foamed glass particles to, the ventilated mullite and alumina ventilated and combinations thereof. The tools may be manufactured with porosity open cell inducers, such as beads of naphthalene, walnut shells, or other organic granules that burn during firing of the tool to leave void spaces within of the matrix of the tool, or they may be manufactured with hollow pore inducing media, closed cell (for example hollow glass spheres). Preferred abrasive tools either do not contain added pore inducing media, or contain a minor amount (that is to say, less than 50% by volume, preferably less than 20% by volume and most preferably between all less than 10% by volume of the porosity of the tool) of added pore inducing media. The amount and type of added pore induction medium should be effective to produce an abrasive tool with a porosity level at least 30% by volume is interconnected porosity.

The agglomerated abrasive tools of the invention having these physical properties and these structural features are preferably manufactured by a process wherein a majority of the abrasive grain has been agglomerated with a binder material before the tool components are mixed molded and heat treated to form an abrasive composite. These abrasive grain agglomerates may be made with inorganic materials or caking with organic caking materials.

Abrasive agglomerates made with organic materials caking

The agglomerates made with organic caking materials which are useful in the invention are three-dimensional structures or granules, including composites treated abrasive grain and bond material. All materials caking polymers, thermosets, commonly used in the abrasive tool industry as binders for organic bonded abrasives, coated abrasives, and the like are preferred. Such materials include phenolic resin materials, epoxy resin materials, phenol formaldehyde resin materials, urea formaldehyde resin materials, resin materials melamine formaldehyde, acrylic resin materials, modified resin rubber compositions, compositions added a filler and combinations thereof. The agglomerates made with organic bond material have a loose packing density (LPD) <1.5 g / cc, preferably less than 1.3 gg / cc, an average dimension of about 2 to 10 times the average size of abrasive grain, or from about 200 to 3000 microns and a porosity level of from about 1 to 50%, preferably 5 45% and most preferably 10 to 40% by volume.

A major proportion (that is to say, at least 50% by volume) of the porosity within the agglomerates is present as porosity permeable to the flow of organic binder material in liquid phase inside the agglomerates during heat treatment of the molded abrasive tools, agglomerates of the invention.

The abrasive grain useful in agglomerates made either with the organic materials or inorganic binders may include one or more abrasive grains known for use in abrasive tools, such as the alumina grains, including fused aluminum oxide, alumina sintered and sol gel sintered alumina, sintered bauxite, and the like, silicon carbide, alumina-zirconia, aluminoxynitrure, ceria, boron suboxide, garnet, flint, diamond, including natural and synthetic diamond, cubic boron nitride (CBN), and combinations thereof. Any size or shape of abrasive grain may be used. For example, the grain may include some alumina grains elongated sintered sol gel (eg, less than 10% by volume of total abrasive grain in the tool) with a high aspect ratio of the type mentioned in US No. 5 129 919. Suitable particle sizes for use in the present invention extend normal abrasive grain (e.g., greater than 60 and up to 7000 microns) to microabrasifs grains (for example, 0.5 to 60 microns), and mixtures of these sizes. For a given abrasive grinding operation, it may be desirable to agglomerate an abrasive grain with a smaller grain size of a grain size of abrasive grain (non-agglomerated) normally selected for this abrasive grinding operation. For example, the abrasive grain agglomerate size of 80 may be substituted for the abrasive grain 54, grain 100 substituted for the agglomerated abrasive grain 60 and the 120 grit agglomerate substituted for the abrasive grain 80. As used herein, the size of "grain" refers to abrasive grain size on the scale of grains of the Norton Company.

Abrasive agglomerates made with inorganic materials caking

Agglomerates made with inorganic caking materials which are useful in the invention are three-dimensional structures or granules, including sintered porous composites of abrasive grain and binder material or vitrified ceramic. The agglomerates have a loose packing density (LPD) <1.6 g / cc, an average dimension of about 2 and 20 times the average abrasive grit size, and a porosity of about 30 to 88%, preferably 30 to 60% by volume. The abrasive grain agglomerates preferably have a minimum crush strength of 0.2 MPa.

The preferred sintered agglomerate size for typical abrasive grains ranges from about 200 to 3000, more preferably 350 to 2000, preferably from 425 to 1000 microns in internal diameter. For microabrasive grain, preferred sintered agglomerate size ranges from 5 to 180, more preferably from 20 to 150, preferably from 70 to 120 μιτι average diameter.

The abrasive grain is present at about 10 to 65% by volume, more preferably 35 to 55% by volume, and preferably 48 to 52 volume% agglomerates.

The agglomerating materials useful in making the agglomerates preferably include ceramic and vitrified materials, preferably of the kind used to provide a binder system for vitrified bonded abrasive tools. These vitrified bonding materials may be a pre-fired glass that has been ground into a powder (a frit), or a mixture of various raw materials such as clay, feldspar, calcium hydroxide, borax, and soda, or a combination of fritted and raw materials. Such materials fuse and form a liquid glass phase at temperatures ranging from about 500 to 1400 ° C and the wet surface of the abrasive grain to create binding rods cooling, thus holding the abrasive grain within of a composite structure. Examples of suitable agglomerating materials for use in the agglomerates are given in Table 2 below. Preferred agglomerating materials are characterized by a viscosity of about 345 poises at 55 300 to 1 180 ° C, and a melting temperature of about 800 to 1300 ° C. However, depending on the posts referred tools and desired properties, the agglomerates may be made with one or more inorganic materials selected from the group consisting of vitrified binder materials, ceramic binder materials, binder materials in glass-ceramics, inorganic salt materials and metallic binder materials, and combinations thereof.

In a preferred embodiment, the binder material is a vitrified binder composition comprising an oxide cured composition to 71% by weight of B2O3 and S1O2, 14% by weight of AfeOa, less than 0.5 wt% oxide alkaline earth and 13% by weight of alkali oxides.

In yet another preferred embodiment, the bonding material can be a ceramic material, including, but not limited to, silica, alkali, alkaline-earth, mixed silicates of alkali and alkaline earth silicates aluminum, zirconium silicates, hydrated silicates, aluminates, oxides, nitrides, oxynitrides, carbides, oxycarbides and combinations and derivatives thereof. In general, ceramic materials differ from glassy or vitrified materials in that the ceramic materials comprise crystalline structures. Some glassy phases may be present in combination with the crystalline structures, particularly in ceramic materials in an unrefined state. Some ceramic materials in a raw state, such as clays, cements and minerals, may be used in the present invention. Examples of specific ceramic materials suitable for use herein include, but are not limited to silica, sodium silicates, mullite and other alumino silicates, zirconia-mullite, magnesium aluminate, magnesium silicate, silicates zirconium, feldspar and other alkali-alumino-silicates, spinels, calcium aluminate, magnesium aluminate and other alkali aluminates, zirconia, zirconia stabilized with yttria, magnesia, calcium oxide, cerium oxide, titanium, or other rare earth additives, talc, iron oxide, aluminum oxide, bohemite, boron oxide, cerium oxide, alumina-oxynitride, boron nitride, silicon nitride, graphite and combinations of these ceramic materials.

Some of these binders ceramic materials (e.g., sodium silicate) do not require thermal processing to form abrasive grain agglomerates. A bonding material solution can be added to the abrasive grain and the resulting mixture dried to bond the grains together to serve agglomerates.

The inorganic bonding material is used in the form of powder and can be added to a liquid vehicle to insure a uniform, homogeneous mixture of binder material with abrasive grain during manufacture of the agglomerates.

A dispersion of organic binders is preferably added to the inorganic binder material powder components to serve as an auxiliary to the molding or processing. These binders may include dextrins, starch, animal protein glue, and other types of glue; a liquid component, such as water, solvent, modifying agents of the viscosity or of pH; and mixing aids. Use of organic binders improves agglomerate uniformity, particularly the uniformity of the dispersion of the bonding material on the grain, and the structural quality of the pre-cooked or raw agglomerates, and that of the cured abrasive tool containing the agglomerates. Because the binders burn during firing of the agglomerates, they do not become part of the finished agglomerate nor of the finished abrasive tool.

An inorganic adhesion promoter may be added to the mixture to improve adhesion of agglomerating abrasive grain materials as required to improve the mixing quality. The inorganic adhesion promoter may be used with or without an organic binder in preparing the agglomerates.

The inorganic bonding material is present at about 0.5 to 15% by volume, more preferably 1 to 10% by volume, and most preferably 2 to 8% by volume of the agglomerate.

The density of the inorganic bonding material agglomerates may be expressed in many ways. The bulk density of the agglomerates may be expressed as the LPD. The relative density of the agglomerates may be expressed as a percentage of initial relative density, or as a ratio of the relative density of the agglomerates to the components used to make the agglomerates, taking into account the volume of interconnected porosity in the agglomerates.

The initial average relative density, expressed as a percentage, may be calculated by dividing the LPD (p) by a theoretical density of the agglomerates (p0), assuming a zero porosity. The theoretical density may be calculated according to the volumetric rule of mixtures method from the weight percentage and density of the bonding material and the abrasive grain contained in the agglomerates. For the inorganic sintered agglomerates of the invention, a maximum percent relative density is 50 volume%, with a maximum relative density of 30% by volume being more preferred.

The density can be measured by a volumetric fluid displacement technique to include interconnected porosity and exclude closed cell porosity. Density is the ratio of the volume of the sintered inorganic agglomerates measured by fluid displacement to the volume of the materials used to make the sintered inorganic agglomerates. The volume of the materials used to make the agglomerate is a measure of the apparent volume based on quantities and packing densities of the abrasive grain and binder material used to make the agglomerates. For the inorganic sintered agglomerates, a maximum relative density of the agglomerates preferably is 0.7, with a maximum relative density of 0.5 being more preferred.

A method of manufacture of abrasive agglomerates

The agglomerates may be formed by a variety of techniques into numerous sizes and shapes. These techniques may be conducted before, during or after firing the initial mixture in step ("raw") of grain and bond material. The preferred step of heating the mixture to cause the melting and flow of bonding material, thereby adhering the bonding material to the grain and fixing the grain in an agglomerated form may be referred to in this document processing, baking, roasting or sintering. Any method known in the art of agglomeration of mixtures of particles may be used to prepare the abrasive agglomerates.

In a first embodiment of method used in the present invention to manufacture agglomerates with organic agglomerating materials, initial grain mixture and bond material is agglomerated before firing the mixture so as to create a relatively weak mechanical structure referred to as " raw agglomerates. "

To drive the first embodiment, the abrasive grain and the caking materials may be agglomerated in the green state by many different techniques, for example, in a plate granulator, and then fed into an oven at 140 to 200 ° C for heat treatment. Raw agglomerates may be placed onto a tray or rack and bake them, with or without rotating, in a continuous or batch process. A heat treatment may be conducted in a fluidized bed apparatus by feeding the agglomerate grain raw inside the bed An infrared or UV treatment can be carried on a vibrating table. Combinations of these methods may be employed.

The abrasive grain may be conveyed from a mixture of tea, mixed with organic binders materials, then wetted with a solvent to adhere the bonding material to the grain, screened for agglomerate size, and then fired in a kiln or a rotary drying device.

Tray in the granulation may be carried out by adding grain to a mixer bowl, and measuring a liquid component containing the binder material (e.g., water, or organic binder and water) onto the grain, with mixing, to agglomerate together.

A solvent can be sprayed onto a mixture of grain and bond material to coat the grain with the bonding material while mixing, and then the coated grain may be recovered to form agglomerates.

A low-pressure extrusion apparatus may be used to extrude a paste of grain and bond material into sizes and shapes which are dried to form agglomerates. A paste may be made from the agglomerating materials and grain with an organic binder solution and extruded into elongated particles with the apparatus and method mentioned in the patent US-A-4 393 021.

In a dry granulation process, a sheet or block made of abrasive grain embedded in a dispersion or a bonding material paste can be dried (e) and then a roll compactor may be used to break the composite of grain and bonding material.

In another method of manufacture of raw or precursor agglomerates, the mixture of organic bond material and grain may be added to a molding device and the mixture molded into shapes and precise sizes, for example, as mentioned in US Patent No. 6 217 413 B1.

In a second embodiment of the process useful herein for making agglomerates, a simple mixture of grain and organic bond material is fed into a rotary calcination apparatus. The mixture was rotated a rev / min predetermined, along a predetermined incline with the application of heat. Agglomerates are formed as and as the mixture of binder material is heated, melts, flows and adheres to the grain. The steps of baking and sintering are carried out simultaneously at speeds and feed and heat activation controlled volumes. In a preferred method, the agglomeration process is conducted according to the methods described in the related priority patent application, US serial number 10/120 969, recorded April 11, 2002.

When agglomeration of the abrasive grain with caking cooking materials at lower temperatures (e.g., about 145 to about 500 ° C), an alternative embodiment of this rotary kiln apparatus may be used. The alternative embodiment, a rotary dryer, is equipped to supply heated air to the discharge end of the tube to heat the abrasive grain mixture believed to agglomerate and firing the bond material in the binder to the grain. As used herein, the term "rotary calcination kiln" includes such rotary dryer devices.

Abrasive grain agglomerates with inorganic agglomerating materials can be conducted according to the methods described in related priority patent application, serial number US 10/120 969, registered on April 11, 2002, and according to the methods described in the following examples included.

Abrasive tools made of abrasive agglomerates

The bonded abrasive tools made with agglomerates include abrasive grinding wheels, segmented wheels, discs, hones, stones and other abrasive composites hewn monolithic or segmented. The abrasive tools of the invention preferably comprise about 5 to 70% by volume, more preferably 10 to 60% by volume, preferably 20 to 52 volume% abrasive grain agglomerates based on the total volume of abrasive composite. 10 to 100% by volume, preferably 30 to 100% by volume, and at least 50% by volume of the abrasive grain in the tool is positioned as a plurality (e.g., 2 to 40 grains) of grains Abrasive compacts together with the bonding material.

The tools of the invention may optionally contain added secondary abrasive grains of, fillers, grinding aids and pore inducing media, and combinations of these materials. The total volume percentage of abrasive grain in the tools (agglomerated and non-agglomerated grain) may range from about 22 to about 48% by volume, more preferably from about 26 to about 44% by volume, and most preferably from about 30 to about 40% by volume of the tool.

The density and hardness of the abrasive tools are determined by the selection of the agglomerates, type of binder and other components of the tool, the level of porosity, together with the size and type of mold and selected pressing process . Bonded abrasive tools preferably have a density less than 2.2 g / cc, more preferably less than 2.0 g / cc, and most preferably less than 1.8 g / cc.

When a secondary abrasive grain is used in combination with the abrasive agglomerates, the secondary abrasive grains preferably provide from about 0.1 to about 90% by volume of the total abrasive grain of the tool, and more preferably about 0 , 1 to about 70% by volume, preferably 0.1 to 50% by volume. Suitable secondary abrasive grains include, but are not limited to, various aluminum oxides, sol gel alumina, sintered bauxite to, silicon carbide, to the alumina-zirconia, in aluminonitrure, in ceria, boron suboxide, cubic boron nitride, diamond, flint and garnet grains, and combinations thereof.

Preferred abrasive tools of the present invention are bonded with an organic binder. Any different binders known in the art of making abrasive tools may be selected for use herein. Examples of suitable binders and binder materials may be added load detected or found in US Patent No. A-6 015 338; A-5,912,216 and 5,611,827, the contents of which are incorporated herein by reference. Suitable binders include phenolic resins of various types, optionally with a crosslinking agent such as hexamethylene tetramine, epoxy resin materials, polyimide resin materials, phenol formaldehyde, urea formaldehyde and melamine formaldehyde materials, acrylic resin materials and combinations thereof. Other thermosetting resin compositions also may be used herein.

Binders or organic solvents may be added to powdered binder components, such as auxiliary molding or processing. These binders may include furfural, water, modifiers of the viscosity or of pH and mixing aids. Use of binders often improves wheel uniformity and the structural quality of the pressed raw or precooked wheel and the fired wheel. Because most of the binders are evaporated during curing, they do not become part of the binder or of the finished abrasive tool.

The organic bonded abrasive tools of the invention may comprise about 10 to 50% by volume, more preferably 12 to 40% by volume, and preferably 14 to 30% by volume of binder. The binder is located inside the three-dimensional abrasive composite such that a first phase of abrasive grains and binder comprises less than 10 volume% porosity, and preferably less than 5 volume% porosity. The first phase appears within the composite matrix of the organic agglomerated abrasive tool in the form of a reticulated network of abrasive grain anchored within the organic binder material. In general, it is desirable to have a first phase within the three-dimensional composite that as fully dense may be that this can be achieved while remaining within the limitations of the materials and manufacturing processes.

Together with agglomerates of abrasive grain and binder, these tools comprise about 38 to 54 volume% porosity, this porosity being a continuous phase including at least 30 volume% interconnected porosity. Preferred organic bonded abrasive tools may comprise 24-48 vol% abrasive grain, 10-38% by volume of organic binder and 38-54% porosity volume.

These organic bonded tools have a minimum speed burst of 4000 SFPM (20.32 m / s), preferably 6000 SFPM (30.48 put).

In a preferred embodiment, organic bonded abrasive tools may comprise 26 to 40 vol% of agglomerated abrasive grains with 10 to 22% by volume of organic binder material and less than 10 volume% porosity, and a second phase consists of 38 to 50 volume% porosity.

When made with agglomerates of grain and organic caking materials, organic bonded abrasive tools may include, as a first phase, 24-42 vol% abrasive grains bonded with 18-38 vol% organic binder material less than 10 vol% porosity, and a second phase consisting of 38 to 54 volume% porosity.

When made with agglomerates of grain and inorganic binders binding materials, the organic bonded abrasive tools may include, as a first phase, 28-48% by volume of grain bonded with 10-33 vol% of binder (the sum of the organic binder in the wheel and inorganic bonding material in the agglomerates) and a second phase consisting of 38 to 53 volume% porosity. The tool preferably comprises a minimum of 1 vol% inorganic binder material, and comprises preferably 2 to 12 vol% inorganic binder material. Such tools preferably have a maximum value of 10GPa elastic modulus and a minimum burst speed of 6000 SFPM (30.48 m / s). When evaluated on the scale of quality of the Norton Company, these abrasive tools have a hardness grade between A and H, and that hardness grade is at least one grade softer than that of a conventional tool otherwise identical made with abrasive grains that have not been agglomerated together with an inorganic binder material.

Optionally, the organic bonded abrasive tool includes a mixture of a plurality of grains agglomerated together with an inorganic binder material and a plurality of grains agglomerated together with an organic binder material.

When made with an organic binder and agglomerates of grain and inorganic binders materials, the bonded abrasive tools may comprise a three-dimensional composite of (a) 22 to 46 volume% agglomerates of abrasive grain with 4 to 20% by volume of inorganic binding material; and (b) 40 to 68% by volume interconnected porosity; wherein a majority of the abrasive grains are present in the form of irregular spacing group within the composite. These bonded abrasive tools have elastic modulus values ​​that are at least 10% lower than elastic modulus values ​​for all other identical conventional tools having regularly spaced abrasive grains within a three-dimensional composite and they show a minimum speed burst of 4000 SFPM (20.32 m / s), preferably 6000 (30.48 m / s). The inorganic bonded abrasive tools comprise 22-40 vol% abrasive grains bonded with 8-20 vol% inorganic binder material, and 40 to 68 volume% interconnected porosity.

In a preferred embodiment, the inorganic bonded abrasive tools comprise 34-42 vol% abrasive grains bonded with 6-12 vol% inorganic binder material, and 46 to 58 volume% interconnected porosity. These tools are made with a vitrified bond material, are substantially free of abrasive grains and fillers of high aspect ratio, and the tools are molded and fired without the addition of pore inducing materials during manufacturing. The preferred vitrified bonded abrasive tools are wheels with a hardness grade between A and M on the scale of quality of Norton Company, and the quality of hardness is at least a softer quality than conventional if not identical with tool regularly spaced abrasive grains within a three-dimensional composite. The preferred vitrified bonded abrasive tools are characterized through an elastic modulus value that is at least 25% lower, preferably at least 40% lower, the modulus value of an otherwise identical conventional tool having grains abrasive regularly spaced within a three-dimensional composite and a minimum burst speed of 6000 SFPM (30.48 m / s).

The preferred vitrified bonded abrasive tools made with agglomerates of grain in inorganic agglomerating materials include inner diameter grinding wheels containing 40 to 52% by volume of abrasive grain and having an elastic modulus value of 25 to 50 GPa. Also included are surface grinding wheels for tooling operations containing 39 to 52% by volume of abrasive grain and a value of elastic modulus of 15 to 36 GPa, and deep cut in grinding wheels containing 30 to 40 volume% abrasive grain and having an elastic modulus value of 8 to 25 GPa.

To produce a suitable mechanical strength in the organic bonded abrasive tool during manufacturing of the tool and during use of the tool in grinding operations, at least 10% by volume of the total binder component must consist of organic binder added and can not be the bonding material used in the agglomerates.

Abrasive wheels may be molded and pressed by any means known in the art, including hot pressing techniques, hot and cold. A treatment may be given to the choice of molding pressure to form flood wheels either to avoid crushing agglomerates, or to crush a controlled amount of agglomerates (that is to say, 0-75% in weight, of the agglomerates) and preserve the three-dimensional structure of the remaining agglomerates. The appropriate applied pressure for making the wheels of the invention depends on the shape, size, thickness and the binder component of the abrasive wheel, and the molding temperature. In current manufacturing processes, the maximum pressure may extend from about 500 to 10,000 lbs / in2 (35 to 704 Kg / cm2). Molding and pressing are preferably conducted at about 53 to 422 kg / cm2, more preferably 42 to 352 kg / cm2. The agglomerates of the invention have sufficient mechanical strength to withstand the molding and pressing steps carried out in typical commercial manufacturing processes for making abrasive tools.

The abrasive wheels may be fired by methods known to those skilled in the art. Baking conditions are primarily determined by the actual binder and abrasives used, and by the type of binder material contained in the abrasive grain agglomerate. Depending on the chemical composition of the selected binder, an organic binder can be fired at 150 to 250 ° C, preferably 160 to 200 ° C to provide the necessary mechanical properties for commercial use in grinding operations.

The choice of a suitable organic binder will depend on the agglomeration process used and the desire to avoid the flow of the heated organic binder within the intra-agglomerate pores.

The organic bonded tools may be mixed, molded and cooked according to various processing methods, and with various proportions of abrasive grain or agglomerate, binder and porosity components as are known in the art. Suitable manufacturing techniques for making organic bonded abrasive tools are described in U.S. Patent No. A-6 015 338; A-5912216; and 5 611 827.

Suitable manufacturing techniques for making vitrified bonded abrasive tools (or other inorganic binders) of the invention are described in related priority patent application, US Serial No. No. 10/120 969, recorded April 11, 2002, in Examples herein and, for example, in patents US-A-5 738 696 and US-A-5 738 697.

Grinding applications

The abrasive tools of the invention are particularly effective in grinding applications having large surface area contact or prolonged continuous contact between the abrasive tool and the workpiece during grinding. Such grinding operations include, but are not limited to the rectification cylinder and disk, to deep grinding pass, the inner diameter grinding, tool room to rectification and other operations precision grinding. Grinding or polishing operations using a fine abrasive grain size of micron or sub micron benefit from use of tools made with the agglomerates of the invention. Compared with conventional systems and tools superfinishing or polishing tools of the invention made with such abrasive agglomerates will erode at grained grinding forces below with little or no surface damage to the workpiece during precision finishing operations (e.g., to produce finished components mirrors on glass and ceramic). The life of the tool remains satisfactory due to the agglomerated structures within the three- dimensional matrix of the tool body.

Due to the interconnected porosity of the tools, in rectifying cylinder and disk, the coolant supply and debris removal are enhanced, resulting in cooler grinding operations, less frequent scrub a tool , to less thermal damage to the workpiece and to a lesser wear of the grinding machine. Because the lower grain size of the abrasive grains in agglomerated form give the grinding efficiency of a size of a grain size of larger grain, but leave a smoother surface finish, the base quality the workpiece often improves significantly.

In a preferred method of rectification disk, organic bonded abrasive tools comprising agglomerates of grain agglomerates with organic agglomerating materials are mounted on a surface grinding machine, rotated, for example at 4000 to 6500 SFPM (20 , 32 to 33.02 m / s), and brought into contact with a workpiece for a sufficient time to grind the workpiece. With this method the wheel removes material of the workpiece at an effective material removal rate, the grinding wheel surface remains substantially free of grinding debris and, after grinding is completed, the workpiece machined is substantially free of thermal damage.

In a preferred method of grinding deep pass, vitrified bonded abrasive wheels include grain agglomerates agglomerated with inorganic agglomerating materials having a modulus value at least 10% lower than the elastic modulus value of an otherwise identical conventional tool having regularly spaced abrasive grains within a composite three dimensions, and having a minimum burst speed of 4000 SFPM (20.32 m / s) and mounted on a grinding machine deep passes. The vitrified grinding wheel is rotated at a speed of 5500 to 8500 SFPM (27,94 to 43.18 m / s) and brought into contact with a workpiece for a sufficient time to grind the workpiece. By this method the wheel removes material of the workpiece at an effective material removal rate and, after grinding, the workpiece is substantially free of thermal damage.

The following examples are offered for purposes of illustration of the invention, and in no way limiting.

Example 1

A series of agglomerated abrasive grain samples containing inorganic binder material into a rotary calcination apparatus was prepared (electrical ceramic model) # HOU-5D34-RT-28, 1 200 ° C maximum temperature, 30 kW inlet, equipped with a refractory metal tube of 72 "(183 cm) long, 5.5" (14 cm) internal diameter, manufactured by Harper International, Buffalo, New York). Was replaced refractory metal tube by a tube of the same dimensions silicon carbide, and modified the device to operate at a maximum temperature of 1 550 ° C. The agglomeration process under atmospheric conditions to a temperature control set point of the hot zone of 1180 ° C with a rotation speed of the camera tube 9 rev / min was carried out, a angle of inclination of from 2.5 to 3 ° tube, and a feed rate of 6-10 kg / hour of material. The yield of usable free-flowing granules (defined as -12 strands to the plate) was 60 to 90% of the total weight of the feedstock prior calcination.

Were made the samples of agglomerate from a unique blend of abrasive grain, bond material and water mixtures described in Table 1-1. The material compositions vitrified binder used to prepare the samples are listed in Table 2. Samples were prepared from three types of abrasive grains: fused alumina 38A, fused alumina 32A and Norton SG grain of alpha alumina sol sintered gel, obtained from Saint-Gobain Ceramics & Plastics, Inc., Worcester, MA, USA in grain sizes listed in Table 1.

After agglomeration in the rotary calcination apparatus, the samples were screened agglomerate abrasive grain and tested for their loose packing density (LPD), size distribution and their resistance agglomerates. These results are shown in Table 1-1.

Table 1-1 Characteristics of granules agglomerated

<img img-format="tif" img-content="drawing" file="LU91110A1D00431.tif" id="idf0001" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00441.tif" id="idf0002" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00451.tif" id="idf0003" />

is the percentage by volume of bonding material is a percentage of solids within the granule (i.e., the bond material and grain) after firing, and does not include the percentage by volume of porosity.

The percentage was calculated by volume bond material agglomerates cooked using the LOI (loss of ignition - ignition loss) average in the raw materials bond material.

Was calibrated sintered agglomerates with test sieves of the EU standards mounted on a vibrating screening apparatus (Ro-Tap; Model RX-29; WS Tyler Inc. Mentor, OH). The sieve mesh sizes ranged from 18 to 140, as appropriate for different samples. We measured the bulk packing density of the sintered agglomerates (LPD) through the procedure of the American National Standard for Bulk Density of Abrasive Grains.

The initial average relative density, expressed as a percentage, was calculated by dividing the LPD (p) by a theoretical density of the agglomerates (po), assuming a zero porosity. The theoretical density was calculated according to the volumetric rule of mixing methods from the weight percentage and density of the I bonding material and the abrasive grain contained in the agglomerates.

The resistance of the agglomerates was measured by means of a compaction test. Compaction tests were performed using a lubricated die steel of one inch (2.54 cm) diameter on an Instron® universal testing machine (model MTS 1125, 20,000 lbs (9072 Kg)) with i agglomerate sample of 5 grams. The sample was poured agglomerate in the die and slightly leveled by tapping the outside of the die. A punch is inserted from the top and a crosshead lowered until a force ("initial position") was observed on the recording apparatus. The pressure at the constant rate of increase (2 mm / min) was applied to the sample up to a maximum of 180 MPa of pressure. The volume of the agglomerate sample (the compacted LPD of the sample), observed as a displacement of the crosspiece (stress) was recorded as the relative density as a function of the logarithm of the applied pressure. Then riddled the residual material to determine the percentage crushed fraction. Different pressures were measured to establish a graph of the relationship between the log of the applied pressure and the crushed fraction in percentage. The results are reported in Table 1 as the log of the pressure at the point where the milled fraction equates to 50 weight percent of the agglomerate sample. The crushed fraction is the ratio of the weight of crushed particles passing through the smaller screen based on the weight of the initial sample weight.

These agglomerates had LPD, a particle size distribution, and molding strength and retention characteristics of the granule size suitable for use in the commercial manufacture of abrasive grinding wheels. The finished agglomerates sintered had three-dimensional shapes varying among triangular shapes, spherical, cubic, rectangular and other geometric shapes. Agglomerates consisted of a plurality of individual abrasive grits (e.g., 2 to 20 grains) bonded together by vitreous bonding material at the contact points grain to grain.

The size of the agglomerates of granules increased with an increase in amount of agglomerating material in the agglomerate granule over the of range of 3 to 20% by weight of the binder material.

Was observed adequate compaction resistance for all samples 1-9, indicating that the vitreous bond material had evolved and flowed to create an effective binder among the abrasive grains within the agglomerate. Agglomerates made with 10 weight% of agglomerating material had significantly higher compaction resistance compared to those made with 2 or 6 weight% of agglomerating material.

Lower LPD values ​​were an indicator of a higher degree of agglomeration. The LPD of the agglomerates decreased with increase of the weight percent of the bonding material and with decreasing abrasive grit size. Relatively large differences between 2 and 6% by weight of binder material, compared with relatively small differences between 6 and 10% by weight of binder material indicate a weight percentage of binder material below 2% by weight may be inadequate for the formation of agglomerates. The higher weight percentages, located at above about 6% by weight, the addition of more agglomerating materials may not be beneficial to provide significantly greater or stronger agglomerates.

As suggested by the results for granule size, agglomerate samples agglomerating material C having the lowest molten glass viscosity at the agglomerating temperature, had the lowest LPD of the three among caking materials. The abrasive type did not have significant effect on the HPA.

Table 1-2: Material binder used in the agglomerates

<img img-format="tif" img-content="drawing" file="LU91110A1D00471.tif" id="idf0004" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00481.tif" id="idf0005" />

to. The variation of bond material A-1 exposed in parentheses was used for the samples of Example 2.

b. Impurities (eg, Fe203 and T1O2) are present in about 0.1 to 2%.

Example 2

Abrasive Grain / Inorganic binder material Aqqlomérats

Were used caking vitrified materials to make samples AV2 and AV3 the agglomerate abrasive grain. The agglomerates were prepared according to the rotary calcination method described in Example 1 using the materials described below. Was produced AV2 agglomerates with 3% by weight of binder material A (Table 1-2). Was set the temperature of the roaster at 1 250 ° C, the tube angle was 2.5 degrees and the rotation speed was 5 rev / min. AV3 agglomerates were made with 6 wt% of agglomerating material E (Table 1-2), at a temperature of 1200 ° C calcination apparatus, with a tube angle of 2.5 to 4 and a rotational speed of 5 rev / min. The abrasive grain was a fused alumina abrasive grain 38A, 80 grit size, obtained from Saint-Gobain Ceramics &amp; Plastics, Inc., Worcester, MA, USA.

Were tested vitrified grain agglomerates on the bulk packing density, the density and size. The test results are listed in Table 2-1 below. Agglomerates consisted of a plurality of individual abrasive grits (e.g., 2 to 40 grains) bonded together by vitrified material to grain contact points, together with visible void areas. The majority of the agglomerates were sufficiently resistant to compaction to retain a three dimensional character after being subjected to mixing and molding of the abrasive wheel.

Table 2-1 Abrasive Grain / Vitrified agglomerates

<img img-format="tif" img-content="drawing" file="LU91110A1D00491.tif" id="idf0006" />

to. The percentages are on a total solids basis, only include the vitrified binder material and abrasive grain, and exclude any porosity within the agglomerates. Temporary organic binder materials were used to adhere the vitrified bond to the abrasive grain (for AV2, 2.83 wt% of binder based on AR30 liquid protein was used, and for AV3, 3.77 wt% binder AR30 liquid protein was used). Temporary organic binder materials during sintering of the agglomerates was burned in the rotary calciner and the final percentage by weight of the bonding material does not include them.

Grinding wheels

Samples AV2 and AV3 were used to make agglomerate experimental abrasive grinding wheels (type 1) (finished size 5.0 X 0.5 X 1.250 inch) (12.7 X 1.27 X 3.18 cm). Experimental wheels were made by adding the agglomerates to a rotating paddle mixer (a Foote-Jones mixer, obtained from Illinois Gear, Chicago, IL), and blending with the agglomerates a liquid phenolic resin (V-1181 resin Honeywell International Inc., Friction Division, Troy NY) (22 wt% of resin mixture). A phenolic resin was added to the wet agglomerates in powder (Durez 29-717 Varcum® resin obtained from Durez Corporation, Dallas TX) (78 wt% of resin mixture). The percentage amounts of abrasive agglomerate weight and of binder resin used to make these wheels and the composition of the finished wheels (including volume% abrasive, a binder and a porosity in the fired wheels) are listed in the Table 2-2 below.

The materials are mixed for a time sufficient to obtain a uniform blend and minimize the amount of loose binder. After mixing, the agglomerates were screened through a sieve of 24 mesh to break up any large clumps of resin. Was placed the uniform agglomerate mixture and binder inside molds and pressure was applied to form the raw grinding stage (uncooked). It was removed from the molds of such floods wheels, we wrapped them in coated paper and it was cooked by heating to a maximum temperature of 160 ° C, calibrated them, finished, and inspected according to commercial manufacturing techniques wheels known in the art. Was measured over the grindstone elastic modulus and the results are shown in Table 2-2 below.

The modulus of elasticity was measured using a grindosonique machine according to the method described in J. Peters, "Sonic Testing of Grinding Wheels" Advances in Machine Tool Design and Research, Pergamon Press, 1968.

Table 2-2 Compositions of wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D00501.tif" id="idf0007" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00511.tif" id="idf0008" />

to. Was manufactured C-1 wheels, C-2 and C-3 with a phenolic resin binder and specifications of these grinding wheels are commercially available from Saint-Gobain Abrasives, Inc. was manufactured the C-4 and C Grinders -5 from shellac resin blended with a minor amount of phenolic resin binder. These wheels specifications are commercially available from Saint-Gobain Abrasives, Inc. was prepared these samples C-4 and C-5 in the laboratory according to these commercial specifications, and cooked them a quality final hardness grindstone J and L, respectively.

b. The C-6 and C-7 wheels were not tested in the grinding tests. These comparative specifications of comparative wheels are commercially available from National Grinding Wheel Company / Radiac, Salem, IL, and from Tyrolit NA, Inc., Westboro, MA.

c. The volume percent "total binder" is the sum of the amount of vitrified binder material used to agglomerate the grain and the amount of organic resin binder used to make the grinding wheel. The volume percent of binder "(organic)" is the portion of the total volume percentage of the binder consisting of the organic resin added to the agglomerates to make the grinding wheel.

Example 3

Experimental wheels of Example 2 were tested in a simulated roll grinding test in comparison with a grinding wheels commercially available agglomerated with phenolic resin (C-1-C-3, obtained from Saint-Gobain Abrasives , Inc., Worcester, MA). It was also tested related Shellac wheels prepared in the laboratory (C-4 and C-5) from a shellac resin blend as comparative wheels. Comparative grinding wheels because they had compositions were selected, structures and physical properties equivalent to those wheels used in the grinding operations per cylinder, commercial.

To simulate roll grinding in a laboratory environment, it has led to a slot grinding operation, with constant contact on a surface grinding machine. We used the following conditions rectification in the tests.

A grinding machine grinding of Brown &amp; Sharpe Surface

Mode: Two corrections to single strand continuous contact, reversal at the end of the race before losing contact with the workpiece.

Coolant: Clear Trim 1:40 ratio coolant: deionized water.

Workpiece: 16 x 4 inch 4340 steel, hardness RC50 speed of the workpiece: 25 ft / min Grinding wheel speed 5730 r / min Power from above: total 0.100 inch Cutting depth: 0.0005 inch each end contact time: 10.7 minutes

Surfacing: single point diamond cross feed to 10 inches / min, correction 0.001 inches.

The vibration of the grinding wheel is measured during the grinding with a IRD Mechanalysis equipment (camera model to analyze 855 Analyzer / Balancer obtained from Entek Corporation, North Westerville, Ohio). In an initial grinding passage, vibration levels at various frequencies (as velocity in units of inches / second) were recorded, using a fast Fourier transform process (FFT), at two and eight minutes after surfacing of the wheel. After the initial grinding passage, we had made a second pass rectify the level of increase related to time vibration was recorded at a selected frequency, target (57,000 cpm, the frequency observed during the initial pass) during the 10 , 7 minutes, the whole grinding wheel remained in contact with the workpiece. The rate of wheel wear (WWR), the material removal rate (MRR) and other grinding variables were recorded as and when the grinding passes were made. These data, together with the vibration amplitude for each wheel after 9-10 minutes of continuous contact grinding in, are shown in Table 3-1, below.

Table 3-1 Results of the grinding tests

<img img-format="tif" img-content="drawing" file="LU91110A1D00541.tif" id="idf0009" />

It can be seen that the experimental wheels displayed the lowest wear rate of the grinding wheel and the lowest vibration amplitude values. Commercial grinders, comparative manufactured with phenolic resin binders (38A80-G8 B24, B24 and -08 B24 K8) had low wheel wear rates, but had unacceptably high vibration amplitude values. It could be predicted that these wheels creates a chatter vibrations in a real operation rectification cylinder. The comparative wheels made with shellac resin binders (53A80J7 Shellac Blend and 53A80L7 Shellac Blend), had high grinding wheel wear rates but low values ​​may be accepted amplitude vibration. The experimental wheels were superior to all comparative wheels over a range of power levels (amplitude almost constant vibration 10 to 23 hp and lower coherently WWR) and the experimental wheels displayed superior G ratios (rate of removing material / wear rate of the grinding wheel), highlighting efficiency and lifetime of the excellent grinding wheel.

It is believed that the relatively low elastic modulus and relatively high porosity of the experimental wheels creates a chatter resistant wheel without sacrifice of the life of the grinding wheel or of the efficiency of rectification. So rather unexpectedly, it was observed that the experimental wheels exerted a more efficient correction than wheels containing higher volume percentages of grain and having a harder wheel grade. Although the experimental wheels were constructed to yield a relatively soft grade of hardness (that is to say, as A to E in the scale of hardness of the Norton Company grinding wheel), they rectifiaient more aggressively, with less wheel wear, yielding a higher G ratio than the comparative wheels having a quality value significantly harder (that is to say, grades G to O scale hardness of the grindstone Norton Company). These results were significant and unexpected.

Example 4

Was prepared Experimental wheels containing agglomerated grain in commercial manufacturing operation and tested in a commercial operation the rectification cylinder where shellac bonded grinding wheels have been used in the past.

Grit / Agqlomérats inorganic bonding material

Were used caking vitrified material (material caking A from Table 1-2) to make the AV4 sample of bonded abrasive grain. The sample AV4 was similar to sample AV2, except that a commercial batch size was manufactured for sample AV4 the. Agglomerates according to the rotary calcination process was prepared as described in Example 1. The abrasive grain was a fused abrasive grit 38A alumina 80 grit size, obtained from Saint-Gobain Ceramics &amp; Plastics, Inc., Worcester, MA, USA, and was used 3% by weight of the binder material A (Table 1-2). Was set the temperature of the roaster at 1 250 ° C, the tube angle was 2.5 degrees and the rotation speed of 5 revs / min. Agglomerates were treated with a solution of 2% silane (obtained from Crompton Corporation, South Charleston, West Virginia).

Grinding wheels

We used the sample agglomerate AV4 to produce grinding wheels (finished size 36 "diameter X 4" wide X 20 "central hole (type 1) (91.4 X 10.2 X 50.8 cm ). The experimental abrasive wheels were made with commercial manufacturing equipment by mixing the agglomerates with liquid phenolic resin (V-1181 resin from Honeywell International Inc., Friction Division, Troy NY) (22% by weight of mixture of resin) and powdered phenolic resin (Durez 29-717 Varcum® resin obtained from Durez Corporation, Dallas TX) (78 wt% of resin mixture). The amounts in percent by weight of abrasive agglomerate and resin binder used in these wheels are listed in Table 4-1 below. The materials were blended for a sufficient time to obtain a uniform mixture. The mixture was placed in a uniform agglomerate and binder in molds and applied a pressure for forming stacks raw stage (uncooked). was removed from these raw grinding mussels, is wrapped them in coated paper and was cooked by heating to a maximum temperature of 160 ° C, calibrated, finished, and inspected according to commercial grinding wheel manufacturing techniques known in the art. Was measured modulus of elasticity of the finished wheel and the density in the cured state and the results are shown in Table 4-1, below. We measured the speed of the wheel burst and maximum operational speed was determined to be 9500 SFPM.

The composition of the wheels (including volume% abrasive, a binder and a porosity in the fired wheels) is described in Table 4-1. These wheels had a porosity structure, relatively uniform, continuous, visibly open, unknown in organic bonded grinding wheels previously made in a commercial operation.

Table 4-1 Wheel Composition

<img img-format="tif" img-content="drawing" file="LU91110A1D00571.tif" id="idf0010" />

to. The volume percent "total" of binder is the sum of the amount of vitrified binder material used to agglomerate the grain and the amount of organic binder resin used to make the grinding wheel. The volume percent of binder "(organic)" is the portion of the total volume percentage of the binder consisting of the organic resin added to the agglomerates to make the grinding wheel.

Grinding Tests

These experimental abrasive wheels were tested in two commercial grinding applications for cold mill roll finishing. After being rectified, the cylinders forged steel will be used to roll and finish the surface of metal sheet (e.g., steel). Commercial applications traditionally use shellac bonded grinding wheels business (the abrasive grain to grain alumina 80 is common) and these wheels normally operate at 6500 SFPM with a maximum speed of about 8000 SFPM. The grinding conditions are listed below and the test results are shown in Tables 4-2 and 4-3.

Terms and conditions of correction:

Grinding machine: Farrell Roll Grinder, 40 hp Substance cooling: Stuart Synthetic w / water Grinding wheel speed: 780 r / min

Workpieces: forged steel cylinder head-to-tail tandem grinding, hardness 842 Equotip, 82 X 25 inches (208 x 64 cm)

Speed ​​of the workpiece (cylinder): 32 rev / min

Cross feed: 100 inches / min

Continuous power: 0.0009 inch / min

Final supply: 0.0008 inches / min

Surface finish required: 18-30 Ra roughness, 160 peaks maximum

Conditions B correction grinding machine: Pomini Roll Grinder, 150 hp Coolant: Stuart Synthetic w / water Grinding wheel speed: 880 r / min

Workpiece: forged steel cylinder head-to-tail tandem grinding, hardness 842 Equotip, 82 X 25 inches (208 x 64 cm)

Speed ​​of the workpiece (cylinder): 32 rev / min cross-feed: 100 inch / min Continuous feed: 0.00011 inch / min Final Injection: 0.002 inch / min

Surface finish required: roughness Ra of 18 to 30, approximately 160 to 180 peaks

Table 4-2 Results of the grinding test / conditions A correction

<img img-format="tif" img-content="drawing" file="LU91110A1D00591.tif" id="idf0011" />

Under conditions A rectification, the experimental grinding wheels displayed excellent grinding performance, achieving significantly higher G ratios than those observed in past commercial applications under these grinding conditions with shellac Bonded. Based on past experience in rectification cylinder under conditions A correction, the experimental wheels 2-1,2-2 and 2-3 would have been considered too soft (B values ​​D hardness quality to Norton Company) to produce a commercially acceptable grinding efficiency, thus these results showing excellent G ratios were highly unusual. In addition, the surface finish of the cylinder was free of chatter marks and located in the specifications of surface roughness (18-30 Ra) and number of surface peaks (approx 160). The experimental wheels providing a high quality surface finish previously observed only with shellac bonded grinding wheels.

A second experimental test grinding wheel 3-3, under grinding conditions B, confirmed the surprising benefits of using the wheels of the invention in a commercial application of finish grinding by cold cylinder over an extended test period . The test results are shown below in Table 4-3.

Table 4-3 Results of the grinding test / B correction terms

<img img-format="tif" img-content="drawing" file="LU91110A1D00601.tif" id="idf0012" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00611.tif" id="idf0013" />

to. Measuring the wear of the grinding wheel

<img img-format="tif" img-content="drawing" file="LU91110A1D00621.tif" id="idf0014" />

b. Measuring the material removal

The cumulative G ratio for experimental wheel 2-4 was 2.093 after 19 cylinders rectification and undergoing wear of approximately three inches from the wheel diameter. This ratio G represents an improvement of two to three times G observed for commercial grinders reports (e.g., the shellac bonded wheels, C-6, C-7 described in Example 2) used to grind rolls under the Grinding Conditions A or B. The speed of rotation of the grinding wheel and the rate of material removal exceeded that of comparative commercial wheels used in this roll grinding operation, thus showing additionally the potential effectiveness of the unexpected grinding with the grinding method of the invention. The surface finish of the roller achieved by the experimental wheel was acceptable under commercial production standards. Cumulative results observed after grinding 19 rolls confirm the steady state operation of the experimental wheel and the beneficial resistance of the wheel to development of wheel lobes, vibration and chuckles gradually as the wheel is consumed by the grinding operation.

Example 5

Grit / inorganic binders aaalomérats

Were manufactured agglomerates samples from a simple mixture of abrasive grains, caking materials and water mixture described in Table 5-1. The composition of caking vitrified materials used to prepare the samples was the binder material C listed in Table 1-2. The abrasive grain was a 38A alumina abrasive grain, fondue, 80 grit size, obtained from Saint-Gobain Ceramics &amp; Plastics, Inc., Worcester, MA, USA.

The samples were formed of agglomerated abrasive grains to 1 150 ° C using a rotary calcination apparatus (model # HOU-6D60-RTA-28, Harper International, Buffalo, New York) equipped with a metal tube (Hastelloy ) of 120 inches (305 cm) long, 5.75 inches (15.6 cm) inner diameter, 3/8 inch (0.95 cm) thick, having a heated length of 60 inches (152 cm) with three temperature control zones. Brabender® a supply unit was used with adjustable control volumetric feed rate to measure the mixture of abrasive grains and binders materials in the heating tube of the rotary calciner. The process of agglomeration was carried out under atmospheric conditions, with a rotational speed of the camera tube of 3.5 to 4 rev / min, a tube incline angle of 2.5 to 3 degrees, and a feed speed of 6 to 10 kg / hour material.

After agglomeration in the rotary calcination apparatus, were screened samples of agglomerated abrasive grains and tested for loose packing density (LPD) and size distribution. These results are shown in Table 5-1.

Table 5-1 Characteristics of V1 agglomerated granules

<img img-format="tif" img-content="drawing" file="LU91110A1D00631.tif" id="idf0015" />

is the percentage by volume of bonding material is a percentage of the solid material included within the granule (that is to say, bonding material and grain) after firing, and does not include the volume percent of porosity.

We used the V1 sample of agglomerated grain to make grinding wheels (type 1) (finished size: 20 X 1 X 8 inch) (50.8 X 2.54 X 20.3 cm). The composition of the wheels (including volume% abrasive, binder and porosity in the fired wheels), density, and mechanical properties of the wheels are described in Table 5-2. Compositions for experimental wheels 1-4 were chosen to produce hardness F quality wheels and compositions for experimental wheels 5-8 were chosen to produce quality G. Hardness wheels

To make the abrasive wheels, the agglomerates were added to a mixer along with a liquid binder and a powdered vitrified bond composition corresponding to the agglomerating material C of Table 1-2. The structures of the agglomerates were sufficiently resistant to compaction to retain an effective amount of agglomerates having a three dimensional character after being subjected to mixing and molding of the abrasive wheel. Was then molded, dried, fired grinding wheels at a maximum temperature of 900 ° C, calibrated them, subjected to a finishing treatment, balanced and inspected according to commercial grinding wheel manufacturing technology known in the art.

The finished wheels were tested following in terms of safety a commercially practiced speed test to ensure that the wheels had sufficient mechanical strength for rotational movement when attached to a grinding machine and sufficient mechanical strength for the grinding operation. All experimental wheels survived the maximum speed test for the testing equipment (85.1 m / s) and, thus, had sufficient mechanical strength for the deep cut in grinding operations.

The composition of the wheels (including volume percent abrasive, the binder and porosity in the fired wheels), density and mechanical properties of the wheels are described in Table 5-2.

Table 5-2 Characteristics of abrasive wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D00651.tif" id="idf0016" />

to. Comparative wheel samples were commercial products obtained from Saint-Gobain Abrasives, Inc., Worcester, MA, and recorded with the commercial descriptions for each wheel indicated in Table 5-2.

b. Values ​​for volume% binder of the experimental wheels include the volume% vitrified bond material used on the grains to make the agglomerates.

c. The wheels on the modulus of rupture was tested on a mechanical testing machine Instron Model 1125 with a bending template at 4 points with a range of the support 3 ", a 1 of load bearing," and a loading rate 0.050 "per minute crosshead speed.

d. The wheels are not breaking when they were rotated at the maximum speed attained with the test machine to try the break.

The values ​​of modulus of elasticity of the experimental wheels 1-4 ranged from 34 to 43% less than the comparative wheel quality value F, and the elastic modulus values ​​of the experimental wheels 5-8 ranged from 45 to 54% less than the value of the comparative wheel quality G. The wheels having identical volume% compositions of grain, binder and porosity had rather unexpected way significantly different elastic modulus values. The experimental wheel 1 had a 34% modulus of elasticity of less than the value of the comparative wheel quality F, and experimental wheel 5 has an elastic modulus value 51% lower than the value of the comparative wheel G. In a separate experiment quality, comparative wheels made at softer qualities to be characterized by equivalent elastic modulus values, relatively low, lacked sufficient strength to pass the speed test 85 1 m / s.

The speed test values ​​for the experimental wheels were fully acceptable. Furthermore, at identical volume% compositions of grain, and binder porosity, experimental wheel 1 was demonstrated a modulus of rupture only 7% lower than the comparative wheel F of quality, while experimental wheel 5 did demonstrate a modulus of rupture only 3% lower than the quality of comparative grinding wheel G. This slight drop modulus of rupture was expected, given the slight drop in density of the experimental wheels relative to the comparative wheels. The drop in density also suggests the experimental wheels had resisted shrinkage during thermal processing relative to the comparative wheels having the composition in% by the same volume, and this represents significant potential savings in manufacturing costs, both in terms of cost of material and finishing operations.

The grinding wheels were tested in grinding operations in deep pass relative to comparative commercial wheels recommended for use in deep cut in grinding operations. The comparative wheels had the same ribs of magnitude, the same or similar compositions in% by volume, equivalent hardness grades (quality was determined on the basis of content in% by volume of grain, binder and porosity) and chemistries binder functionally equivalent, and they were otherwise suitable comparative wheels for a correction study in deep passes. But it was made the comparative wheels without agglomerated grain and pore inducer to sacrifice were needed to achieve the target volume% porosity and wheel density. Trade names wheel and compositions comparative wheels are described in Table 5-2 (commercial wheels and 38A80F19VCF2 38A80G19VCF2).

Was performed a grinding test "bevel", the workpiece being inclined at a small angle relative to the rail of the machine on which it was mounted. This geometry results in increasing depth of cut, increasing material removal rate and increasing chip thickness as and as grinding progresses from beginning to end. Thus, grinding data is gathered over a range of conditions in a single pass. The evaluation of the performance of the grinding wheel in the wedge test is further aided by the measuring and recording of power of the spindle and grinding forces. The precise determination of conditions (MRR, chip thickness, etc.) that produce unacceptable results, such as grinding burn or wheel breakage, facilitates the characterization of wheel behavior and the ranking of relative performance.

Terms correction:

Machine: Hauni-Blohm Profimat410

Mode: deep passes bevel grinding

Surface velocity of 5500 feet per minute (28 m / sec)

Table speed, varied from 5 to 17.5 inches / minute (12.7 to 44.4 cm / min) Coolant: Master Chemical Trim E210 200, at 10% concentration with deionized well water , 72 gal / min (272 L / min). Material of workpiece: Inconel 718 (42 HRc)

Fashion surfacing: rotary diamond, DC

Fixed surfacing: 20 micro-inches / rev (0.5 microns / rev)

Gear ratio: 0.8

In these passages grinding, continuous increase in the depth of cut proposed a continued increase material removal rates on the block length (8-inch (20.3 cm)). Failure was indicated by the burning of the workpiece, the wheel breakage, the rough surface finish and / or loss of the wedge shape. The Wheel wear from grinding was less than the loss correction continuous surfacing conduct during the grinding test. The specific energy of grinding and material removal rate at which failure occurred (Maximum MRR) are noted in Table 5-3.

Table 5-3 Results of the grinding test

<img img-format="tif" img-content="drawing" file="LU91110A1D00681.tif" id="idf0017" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00691.tif" id="idf0018" />

to. To calculate percent improvement values, experimental wheels were compared to the nearest equivalent grade in a comparative wheel. The experimental wheels 1 to 4 were compared to the F grade wheel; and experimental wheels 5-8 were compared to the G grade wheel

As can be observed the results of the grinding test in Table 5-3, before the failure occurs, the experimental grinding wheels demonstrate higher MRR values ​​of 20 to 58% compared to those of comparative wheels having identical compositions in% by volume. At identical compositions, experimental wheels were showing at least 17% reduction in the power required to correct (specific grinding energy). These grinding operations efficiencies were achieved without any significant loss of the workpiece surface quality to be machined being rectified. The result suggest the experimental wheels could be operated in commercial applications of deep grinding pass at a lower rate with a constant MRR surfacing for there to achieve at least a doubling of the lifespan.

Example 6

Grit / inorganic binder Aqqlomérats

Were manufactured agglomerated grain samples from a simple mixture of abrasive grain, bond material and water described in Table 6-1. The compositions of vitrified bond material binder used to prepare the samples were the material caking C listed in Table 1-2. The abrasive grain was a 38A alumina abrasive grain, fondue, 60 grit size, obtained from Saint-Gobain Ceramics &amp; Plastics, Inc., Worcester, MA, USA.

There were prepared samples of agglomerate abrasive grain in an industrial rotary calcination apparatus (manufactured by Bartlett Inc. Stow, Ohio; direct fire gas model) at 1250 ° C maximum temperature, equipped with a refractory tube 35 feet (10.7 m) long, 31 inches (0.78 m) inner diameter, 23 inches (0.58 m) thick. The process of agglomeration was carried under atmospheric conditions, at a set point of temperature control of the hot zone 1 250 ° C with a rotation speed of the camera tube of 2.5 rev / min , an angle of inclination of 3 ° to the tube, and a feed rate of 450 kg / hour of material.

After agglomeration in the rotary calcination apparatus, the samples were screened agglomerate abrasive grain and tested for loose packing density (LPD) and size distribution. These results are shown in Table 6-1.

Table 6-1 Characteristics of agglomerated granules V2

<img img-format="tif" img-content="drawing" file="LU91110A1D00701.tif" id="idf0019" />

. The "/ o by volume maxeriau bond is a percentage sonae material inside the granule (that is to say, bonding material and grain) after firing, and does not include the percentage by volume of porosity.

Were used agglomerate samples to make grinding wheels (type 1) (finished size: 20 X 1 X 8 inch) (50.8 X 2.54 X 20.3 cm). To make the abrasive wheels, the agglomerates were added to a mixer at the same time a liquid binder and a powdered vitrified binder composition corresponding to the agglomerating material C of Table 1-2. The structures of the agglomerates were sufficiently resistant to retain an effective amount of agglomerates having a three dimensional character after being subjected to mixing and molding of the abrasive wheel. We chose compositions for experimental wheels 9 to 11 to produce hardness quality stacks I, compositions for experimental wheels 12 to 16 were selected to produce K hardness quality wheels and compositions for experimental wheels 17 19 were chosen to produce hardness quality J. wheels were then molded, dried, fired grinding wheels at a maximum temperature of 1 030 ° C, calibrated them, subjected to a finishing treatment, balanced and inspected according to commercial manufacturing techniques grinder known in the art.

The finished wheels were tested in terms of security according to a commercially practiced speed test to ensure that the wheels had sufficient mechanical strength for rotational movement when mounted on a grinding machine and sufficient mechanical strength for the grinding operation. The results of the burst test are given in Table 6-2. All experimental wheels had sufficient mechanical strength for deep passes in grinding operations. Commercial applications for rectification deep pass traditionally work with these wheels in 6500 SFPM (33 m / s) with a maximum operating speed of approximately 8500 SFPM (43.2 m / s).

The composition of the wheels (including volume% abrasive, a binder and a porosity in the fired wheels), density, and physical properties of the wheels are described in Table 6-2.

Table 6-2 Characteristics of abrasive wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D00721.tif" id="idf0020" />

to. Comparative wheel samples were commercial products obtained from Saint-Gobain Abrasives, Ltd., Stafford, UK, and marked with the grinding wheel designations indicated for each in Table 6-2.

b. Values ​​for volume% binder of the experimental wheels include the volume% vitrified bond material used on the grains to make the agglomerates.

c. This wheel resembles comparative wheel 38A60-the K75 LCNN in terms of volume% composition, but has been manufactured with an abrasive grain of alpha-alumina, sintered sol gel, elongate, having an aspect ratio greater than 4: 1, according to US Patent 5,738,696 and US Patent 5,738,697 issued to WU. Note that it has lower density, but exhibits a modulus value very similar with respect to 38A60K75 LCNN.

The wheels having identical volume% compositions of grain, binder and porosity had rather unexpected way different values ​​of modulus of elasticity. Notably, the elastic modulus value of a comparative wheel (E13 TG2-80 VCF5) manufactured in% by volume is desired relatively high porosity and relatively low density by means of added elongated particles (abrasive grain) rather than with sacrificial pore inducers do not show drop across the elastic modulus value. In fact, the elastic modulus value was higher than the nearest equivalent comparative the wheel and much higher than the experimental wheels having equivalent volume% compositions.

Despite the reduced property of modulus of elasticity, the speed test values ​​for the experimental wheels were fully acceptable. At identical volume% compositions of grain, binder and porosity, experimental wheel 1 was only evidence of rupture modulus values ​​and slightly lower speed burst. The densities of the experimental wheels were slightly lower than those of comparative wheels that had been formulated at an identical composition in% by volume. Thus, a small drop in modulus of rupture was expected. The drop in density also suggests the experimental wheels had resisted shrinkage during thermal processing relative to the comparative wheels having an identical composition in% by volume, and this represents significant potential savings in manufacturing costs, both in terms cost of material and finishing operations.

The grinding wheels were tested in a grinding operation in deep cut in using the test grinding conditions bevel described in Example 5. The wheels were tested relative to comparative commercial wheels recommended for use in operations to Deep passes for rectification. The comparative wheels had the same odds of magnitude, similar or identical compositions in% by volume, equivalent hardness grades (it was determined the quality on the basis of in% by volume of grain content, binder and porosity) and chemistries functionally equivalent binder, and they were otherwise suitable comparative wheels for a correction study in deep passes. But was fabricated comparative wheels without agglomerated grain and sacrificial pore inducers were used to achieve the target volume% porosity and density of the grinding wheel. Trade names millstones and compositions comparative wheels are described in Table 6-2 (commercial wheels LCNN 38A60-I96, K75-38a60 LCNN and LCNN 38A60-J64). The results are given below in Table 6-3.

Table 6-3 Results of the grinding test

Wheel composition of MRR% Energy% V2% Average volume wheel for maximum improvement of specific improvement

Agglomerated abrasives binder porosity mum ration3 of rectifi- ration3 area Merant sity mm3 / s / mm pm cation J / mm3 (9) 36.5 34.1 7.5 58.4 12 ^ 6 3I 392 21 N / Ä ( TÖ) 344 324 574 ÏÖ5 ÏÖJB IO 54J 2 N / Ä (IT) 36 ~ 5 344 82 574 16 ^ 2 68 ^ 434 24 UIA "(12) 4I2 I24 53 384 7d 53/9 4I2 OJ6 24 (13) 392 364 ii2 9J 532 38 442 -19 0.80 (I4) 392 364 8J 542 124 43 40/7 ^ 28 0.80 (15) 372 354 542 9J IL3 4o 42/7 22 0.80 (16) 392 364 522 ioj IO2 25 46.5 46 0.74 (i7) 442 52 532 4I2 I3 / 29 MÂ 4o2 July 61 - (18) 424 392 62 542 I22 51 4i / 3 27 WA

(I9) 424 392 82 522 20 492 43 IO2 N / A

Ex- wheel Composition% Average MRR% Energy ples% by volume to maximum improvement of specific improvement compared agglomerated abrasives binder porosity mum ration3 of rectifi- ration3 ratifs surface and Merant sity mm3 / s / cation pm grain mm J / mm3 non-agglomerated

<img img-format="tif" img-content="drawing" file="LU91110A1D00751.tif" id="idf0021" />

to. To calculate percent improvement values ​​were compared to the experimental wheels nearest equivalent grade in a comparative wheel. Were compared with experimental wheels 9 to 11 to the quality of wheel I; experimental wheels 12-16 at the K quality wheel; and the experimental wheels 17-19 to the quality of wheel J.

As can be observed from the results of the grinding test in Table 6-3, the experimental wheels were showing higher MRR (10 to 68%) before the failure occurs, relative to comparative wheels having identical compositions in% by volume. At identical compositions, experimental wheels were evidence of a reduction in power (3 to 31%) needed for grinding (specific grinding energy). These efficiencies of grinding operations were achieved without significant loss of the workpiece surface quality to be machined being rectified. The result suggest the experimental wheels could be operated in commercial applications of deep grinding pass at a lower rate of planing with a constant MRR thence reaching at least a doubling of the life of the grinding wheel.

Example 7

Grit / aqqlomérats organic binder

We have prepared a series of agglomerated abrasive grain samples (A1 to A8) from a mixture of abrasive grain and binder phenolic resin material (resin Varcum® Durez 29-717, density 1.28 g / cc, obtained from Durez Corporation, Dallas TX), in the amounts described in Table 7-1. We have prepared all the samples with grit fused alumina 38A, silane treated, obtained from Saint-Gobain Ceramics &amp; Plastics, Inc., Worcester, MA, USA, in grain sizes (grain 80 or 46) listed in Table 7-1.

Was placed grain and binder resin material inside the bowl of a mixer (samples A5-A8 in a high shear Erich Mixer RV-02 model manufactured by the Erich Company, Gurnee, IL; the A1 sample tray in a mixer manufactured by Foote-Jones / Illinois Gear in Chicago, IL; and samples A2, A3 and A4 tray mixer is on demand by Boniface Tool and Die in Southbridge MA). The mixture was initiated at a bowl speed set at 64 rev / min and at a paddle speed set at 720 rev / min (samples A5-A8 in the Erich mixer); or a bowl speed of 35 rev / min and a stationary blade (sample A1 in the Foote / Jones mixer); or a bowl speed of 35 rev / min and a paddle speed of 75 rev / min (samples A2 to A4 in the Boniface mixer). While mixing, were sprayed with sufficient solvent (furfural) in a mist onto the mixture of grain and bond material to cause agglomeration whole grain and bond material. Was continued spraying the solvent mixture only until only the grains and bond material had formed agglomerates. In the preparation of the sample A1, manually the solvent was sprayed onto the dry components with a plastic bottle. In preparing the samples A2 to A8, the solvent was sprayed onto the dry components as a continuous mist in measured quantities using a Tool Mist in Coolant Generator, obtained from Wesco Company, Chatsworth, CA. The process of agglomeration was carried under atmospheric conditions, at room temperature.

After agglomeration in the blend was screened abrasive grain samples wet agglomerate through a sieve of 3.5 strands US and dried overnight under ambient conditions. Was again screened on a coarse sieve samples (# 8 sieve sieve standards for the US grain agglomerates 46, # 20 screen for 80 grit agglomerates) and spread them in a single layer on a baking tray coated fluoropolymer (approximately 45 x 30 cm). The agglomerates were then baked in a laboratory oven (Despatch model number VRD-1-90-1E at Despatch Industries, Minneapolis MN) under atmospheric conditions, heated to a maximum temperature of 160 ° C and maintained at this temperature for 30 minutes. We drove the agglomerates cooked under a 1.5 inch steel bar operated manually to partially crush and separate larger agglomerates into smaller agglomerates.

The agglomerates were sized cooked with test sieves to standard US mounted on a vibrating screening apparatus (Ro-Tap; Model RX-29; WS Tyler Inc. Mentor, OH). Screen of the wick sizes ranged from 10 to 45 for agglomerates made with 46 grains and 20 to 45 for agglomerates made with abrasive grains of grain size 80.

The yield of usable free-flowing agglomerates of Samples A1-A8, defined as agglomerates having a particle size distribution of the indicated mesh size (sieve size standards of USA) as a percentage of wt total weight of the grain mixture before agglomeration is presented below in Table 7-1.

The agglomerates were tested for their bulk packing density (LPD), relative density and particle size distribution, and were characterized visually before and after being used to make abrasive grinding tools. The bulk packing density of the fired agglomerates (LPD) was measured following the procedures of the American National Standard for Bulk Density of Abrasive Grains. The initial average density, expressed as a percentage, was calculated by dividing the LPD (p) by a theoretical density of the agglomerates (p0), assuming a zero porosity. The theoretical density was calculated according to the volumetric rule of mixing methods from the weight percentage and density of the bonding material and the abrasive grain contained in the agglomerates.

These agglomerates had LPD, with characteristics of density and particle size distribution suitable for use in the commercial manufacture of abrasive grinding wheels. The results of agglomerate tests are shown in Table 7-1.

Cooked agglomerates finished, had three-dimensional shapes varying among triangular shapes, spherical, cubic, rectangular, cylindrical, and other geometric shapes. The agglomerates consisted of a multiple of individual abrasive grits (e.g., 2 to 40 grains) bonded together by the resin bonding material to contact points grain to grain. On the basis of the material density and volumetric calculations, the porosity of the agglomerates in bulk was about 18 volume%. The structure of the agglomerates were sufficiently resistant to compaction to retain an effective amount of agglomerates retaining a initial three dimensional character after being subjected to mixing and molding of the abrasive wheel.

Table 7-1 Characteristics of granules agglomerated

<img img-format="tif" img-content="drawing" file="LU91110A1D00781.tif" id="idf0022" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00791.tif" id="idf0023" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00801.tif" id="idf0024" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00811.tif" id="idf0025" />

is the percentage by volume of bonding material is a percentage of the solid material within the granule (that is to say, bonding material and grain) after firing, and does not include the percentage by volume of porosity. The percentage volume of bond material cooked agglomerates was calculated assuming a null internal porosity and no mixing loss.

Grinding wheels

We used samples of agglomerates A1, A2 and A3 for manufacturing abrasive grinding wheels in Type 6 cup (finite size: 3.5 X 3.75 X 0.88 to 0.50 inch of edge) (8.9 X 9.5 X 2.2 to 1.3 cm edge). To make the experimental abrasive wheels, the agglomerates were mixed by hand in 250 gram batches with a phenolic resin binder composition until a uniform mixture is obtained. The binder resin composition was a mixture of 22 wt% liquid phenolic resin (V-1181 from Honeywell International Inc., Friction Division, Troy NY) and 78% by weight of phenolic resin powder (Durez Varcum resin ® home Durez Corporation, Dallas TX). Was placed the agglomerate mixture and a uniform binder into molds and pressure was applied to form the raw grinding stage (uncooked). Was removed from these raw grinding mussels, is wrapped them in coated paper and was cooked by heating to a maximum temperature of 160 ° C, calibrated them, they were made to undergo a finishing treatment, and inspected on commercial fabrication techniques well known in the trade wheels.

The finished wheels were tested for their level of security according to a commercially practiced speed test to ensure that the wheels had sufficient mechanical strength for rotational movement when mounted on a grinding machine and sufficient mechanical strength for grinding operation. All experimental wheels survived the test speed of 7200 rev / min and, thus, had sufficient mechanical strength for surface grinding operations.

Compositions of the wheels (including volume percent abrasive, a binder and a porosity grinding wheels cooked) are described in Table 7-2.

Table 7-2: Characteristics of abrasive wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D00831.tif" id="idf0026" />

a A 46 volume% abrasive grain, the comparative wheels contained a greater volume percentage of abrasive grain (i.e., 12 to 16 volume% more) than the experimental wheels made with either 30 or 34% by volume of abrasive grain. bThe values ​​for the volume percentage of the binder of the experimental wheels include the volume percent of resin binder material used on the grains to make the agglomerates and the binder used to make the grinding wheels. Based on the preliminary test observations, the experimental wheels were formulated (percentage parts by volume) to a hardness grade D on the scale of the Norton Company hardness grade for commercial wheels.

cThe samples of comparative wheels were commercial product formulations obtained from Saint-Gobain Abrasives, Inc., Worcester, MA, and sold under the alphanumeric designations wheels indicated for each in Table 7-2. The wheels contain phenolic resin binder, CaF2 and hollow mullite spheres, alumina abrasive grains have a hardness 38A and quality (hardness quality of the Norton Company scale) of either L or P, such that indicated.

These experimental wheels were tested in a surface grinding operation and found them to be suitable for commercial use. Experimental wheels were tested against the comparative wheels described in Table 7-2 that are recommended for commercial use in surface grinding operations. The comparative wheels had the same size dimensions, same abrasive grain and binder types and are otherwise suitable comparative wheels for evaluating the experimental wheels in a surface grinding study, but they were made without agglomerated grain. Results of these grinding tests are shown in Table 7-3.

Test rectification

We tested the wheels of the invention and the comparative wheels in a surface grinding test, to high contact area designed to mimic commercial applications grinding by grinding disc. The following conditions were used.

Terms correction:

machine: grinding machine Okuma GI-20N, OD / ID

correction mode: surface grinding (face); simulation test disc by wheel speed: 6000 rev / min; surface velocity of 5498 feet per minute (27.9 m / sec) working speed; 10 rev / min, 20.9 SFPM / 0.106 m / sec input rate: 0.0105 inches / min (0.0044 mm / s) / 0.0210 inch (0.0089 mm / s) coolant: Trim VHPE210, 5% ratio with deionized well water Workpiece material grinding: steel 52 100 8 inch OD (20.3 cm) x 7 inch Di (17.8 cm) x 0, 50 inch (1.27 cm) board, Rc-60 hardness surfacing: Cluster Diamond: comp. 0.001 inch, 0.01 inch Correction Table 7-3: Results of the grinding test The percentage by volume fraction ratio

<img img-format="tif" img-content="drawing" file="LU91110A1D00851.tif" id="idf0027" />

G / abrasive is a measure of the grinding performance the grain in the wheel. The calculation normalizes the grinding performance to account for the significant differences in the volume percentage of abrasive grain among the experimental and comparative wheels. It can be easily seen that the abrasive grain in the experimental wheels provides significantly better grinding efficiency on a basis of the volume fraction (that is to say, less grain is needed to deliver the same level of effectiveness of rectification).

The results show that the wheels made ​​according to the invention were resistant to wheel wear, and yet capable of operating at input speeds and material removal rates (MRR) equivalent to the comparative wheels over relatives, or with durations of longer wheel life (WWR) at equivalent specific grinding energies or specific grinding energies of less than equivalent lifetimes. The experimental wheel (W4) having a higher volume percent abrasive grain (34%) was unexpectedly evidence of a higher level of wheel wear than the other experimental wheels containing less abrasive grain (30%). At an input of 0.0267, all experimental wheels were demonstrated specific energies below a given MMR relative to comparative wheels. Insofar lower specific grinding energy correlates with lower burn potential, it is anticipated that the wheels of the invention are less evidence of burning of the workpiece as the comparative wheels. In addition, compared to the comparative wheels, the experimental wheels provide significantly better grinding efficiency on a basis of the volume fraction of abrasive grain (that is to say, less grain is needed to deliver the same level of effectiveness of rectification). This result defies the conventional wisdom in bonded abrasives technology of a high-quality wheel containing more grain will resist wear and provide a better life and better grinding efficiency grinding a quality wheel lower (softer). Thus, the superior performance of the inventive wheels was significant and unexpected.

Example 8

Grinding wheels

We used samples A4 and A5 agglomerates to produce grinding wheels of grinding in Type 6 cup (finished size 5.0 X 2.0 X 0.625 - 1.5 inch rim (12.7 X 5.08 X 1.59 -. 3.81 cm rim) experimental abrasive wheels were made according to the method described in Example 7, above.

It was observed during the molding and pressing the raw using the agglomerates that some compression of the mixture was necessary to achieve a cured wheel having sufficient mechanical strength for surface grinding in use. If the mold is filled with the mixture of binder and agglomerates, and essentially no compression occurred during molding is such that the agglomerates retained their original LPD, then the resultant cooked experimental wheels showed no benefit in Under grinding versus comparative wheels. However, if one applies sufficient pressure to the molded mix of agglomerates and binder, compressing the mixture volume of at least 8% by volume, while the grinding wheels were showing improved grinding performance in surface grinding tests . It was observed that compression volume values ​​in the range of 8 to 35% by volume (based on the original LPD of the agglomerates and the volume of mix placed in the mold) produced functional wheels demonstrating the benefits of 'invention. It was observed further that crushing from 8 to 15 volume% of the agglomerates did not change the performance of the wheel made with such agglomerates.

The finished wheels were tested in terms of security according to a commercially practiced speed test to ensure that the wheels had sufficient mechanical strength for rotational movement when mounted on a grinding machine and sufficient mechanical strength for the grinding operation. All experimental wheels survived the test speed of 6308 rev / min and, thus, had sufficient mechanical strength for surface grinding operations.

The composition of the wheels (including volume percent abrasive, a binder and a porosity in the fired wheels) is described in Table 8-1.

Table 8-1: Characteristics of abrasive wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D00881.tif" id="idf0028" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00891.tif" id="idf0029" />

aA 46 volume% abrasive grain, the comparative meues contained a higher percentage of abrasive grain (that is to say 12 to 16 volume% more) than the experimental wheels made with either 30 or 34% by volume abrasive grain. b The values ​​for the volume percentage of the binder of the experimental wheels include the volume percent of resin binder material used on the grains to make the agglomerates and the volume percentages of binder used to make the grinding wheels. The wheels W5, W6 and W8 were made to a D grade on Norton's quality scale. Wheel W7 was made to an A grade and wheel W9 was made to a G grade of hardness on the hardness of the Norton Company scale for commercial wheels. c Samples of comparative wheels were commercial product formulations obtained from Saint-Gobain Abrasives, Inc., Worcester, MA, and sold under the alphanumeric designations wheels indicated for each in Table 8-1. The wheels contain phenolic resin binder, CaF2, hollow mullite spheres, 38A abrasive grains of alumina, and have a hardness grade (commercial scale of the Norton Company) of I, L, P or T, such that indicated.

The permeability of the fluid (air) is given in cc / sec / inch of water units and is measured with a 1.1 cm nozzle by the method described in U.S. Patent Nos 5 738 696 and 5 738 697.

In visual examination of cross-sections of cooked experimental wheels, the phenolic resin used to bond the agglomerates together in the wheels appeared to have been drawn towards the void areas around the surfaces of the agglomerates, filling some or all of the void areas. This was not observed in raw wheels nor in wheels made with a high viscosity resin for grinding wheels. These observations suggest that the binder was drained within the void areas of the agglomerates during the thermal treatment of cooking operation. This migration of the binder during the firing step is deemed to have effectively reduced the intra-agglomerate porosity and effectively increased the inter-agglomerate porosity relative to a theoretical distribution of porosity within and between agglomerates. The net result is that the creation of a composite structure, containing an abrasive grain matrix / binder within a continuous phase comprising porosity of an interconnected nature of.

These experimental wheels were tested in a surface grinding application and it has been found suitable in commercial use. Experimental wheels were tested against the comparative wheels described in Table 8-1 that are used commercially in surface grinding operations. The comparative wheels had the same size dimensions, the same types of abrasive grain and binder were otherwise comparable wheels for evaluating the experimental wheels in a surface grinding study, but they were made without agglomerated grain. The conditions and results of the grinding test are given below and in Table 8-2.

T is correct

The wheels of the invention were tested and the comparative wheels in a surface grinding test, to high contact area, designed to mimic commercial disc applications rectification. The following conditions were used.

Terms correction: Machine: Rail Grinder; Maximum power: 45 HP grinding mode: face grinding (disc simulation test) wheel speed: 4202 r / min; surface velocity of 5500 feet per minute (27.9 m / sec) Working speed: 3 rev / min; MPPS 37.7 / 0,192 m / is input rate: 0.0027 inch / rev (0.0686 mm / rev) and 0.0004 inch / rev (0.1016 mm / rev) Grinding time: 15 minutes appearance spark ("sparkout"): 10 seconds cooling fluid: Trim Clear, 2% ratio with deionized well water

material of the workpiece: 1070 Steel 48 inch OD

(1.22 m) x 46.5 inches Di (1.18 m) x 0.75 inches (1.91 cm) board, Brinell hardness HB 300-331; no surfacing

Table 8-2. Results of the grinding test

<img img-format="tif" img-content="drawing" file="LU91110A1D00911.tif" id="idf0030" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00921.tif" id="idf0031" />

to the fraction of volume percentage G / abrasive ratio is a measure of the grinding performance the grain in the wheel. The calculation normalizes the grinding performance to account for the significant differences in volume percentage of abrasive grain among the experimental and comparative wheels. It can be easily observed that the abrasive grain in the experimental wheels provides significantly better grinding efficiency on a volume fraction basis (ie, less grain is needed to deliver the same level of efficiency rectification).

The results show that the grinding wheels made according to the invention either have lifetimes longer wheel (WWR) at equivalent specific grinding energies or specific grinding energies of less than a life equivalent wheel. To the extent that the specific energy of grinding between correlates with lower burn potential, it is anticipated that the wheels of the invention do exhibit reduced burning of the workpiece as the comparative wheels.

In addition, compared to the comparative wheels, the experimental wheels provided significantly better grinding efficiency on a basis of the volume fraction of abrasive grain (that is to say, less grain is needed to deliver the same level of effectiveness of rectification). This result defies the conventional wisdom in bonded abrasives technology that a higher grade wheel having more grain will resist wear and provides a life and a better grinding efficiency than a lower quality wheel ( softer).

Thus, experimental grinding wheels having sufficient mechanical strength to be commercially acceptable but comparatively low measurable hardness grades and compared high amounts of interconnected porosity, existing as a continuous phase within the abrasive matrix of the wheel, may be constructed and may operate in accordance with the invention.

Example 9

Grinding wheels

Were used agglomerate samples A6 to produce grinding wheels in Type 6 cup (finished size 5.0 X 2.0 X 0.625 - 1.5 inch rim, 12,7X5,08X 1.59 -3.81 cm edge). Was manufactured experimental abrasive wheels following the procedure described in Example 7, above. We tested the finished wheels on safety following a commercially practiced speed test to ensure that the wheels have a sufficient mechanical strength for rotational movement when mounted on a grinding machine and sufficient mechanical strength for the operation rectification. All experimental wheels survived the test speed of 6308 rev / min and, thus, had sufficient mechanical strength for surface grinding operations.

The compositions of the wheels (including volume percent abrasive, a binder and a porosity grinding wheels cooked) are described in Table 9-1.

Table 9-1: Characteristics of abrasive wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D00931.tif" id="idf0032" />

a Values ​​for the volume percent of binder experimental es meu include I volume percent resin bond material used on the grains to make the agglomerates and the volume percent of binder used to make the grinding wheels.

Visual observation of the fired experimental wheels, as in the previous Example 8, demonstrated migration of the binder within the void areas at the surface or within the agglomerates. Again, the net result was the creation of a composite structure, containing an abrasive grain matrix / binder within a continuous phase comprising porosity of an interconnected in nature.

These experimental wheels in the surface grinding operation of the Example 8 and found to be suitable for commercial use was tested. We compared the results of the experimental grinding wheels to results for the four comparative wheels described in Table 8-1. The comparative wheels had the same coasts of magnitude, the same type of abrasive grit and were otherwise suitable for evaluating the experimental wheels in this surface grinding study, but they were made without agglomerated grain. Results of these grinding tests are shown in Table 9-2.

Table 9-2: Results of the grinding tests # 3924

<img img-format="tif" img-content="drawing" file="LU91110A1D00941.tif" id="idf0033" />

to the fraction of volume percentage G / abrasive ratio is a measure of the grinding performance the grain in the wheel. The calculation normalizes the grinding performance to account for the significant differences in volume percentage of abrasive grain among the experimental and comparative wheels (sample C2L, in Table 8-1). It can be easily observed that the abrasive grain in the experimental wheels provides significantly better grinding efficiency on a volume fraction basis (e.g., less grain is needed to deliver the same level of grinding efficiency).

The experimental wheels of relatively low hardness grade (A and D) were showing higher WWR but lower a power consumption relative to the passageway comparable wheels in the same grinding operation (e.g., sample C2L, a grinding wheel The quality, in Table 8-1). The wheels comparable in Table 8-1 (L grade to P grade) were more than 8 grades harder (on the scale of the Norton Company) as the experimental wheels W10 and W11. Unexpectedly, the performance of the experimental wheels (G ratio, MRR and lower consumption in terms of power) exceeded that of the comparable wheels in most test grinding passages.

In addition, compared to the comparative wheels, the experimental wheels provide significantly better grinding efficiency on a basis of volume fractions of abrasive grain (that is to say, less grain is needed to deliver the same level of effectiveness of rectification). This result defies the conventional wisdom regarding bonded abrasives technology that a higher grade wheel having more grain will resist wear and provide longer life and grinding efficiency of the grinding wheel that quality grindstone softer.

Thus, experimental grinding wheels having sufficient mechanical strength to be commercially accepted, but comparatively low measurable hardness of grades and comparatively high interconnected porosity could be manufactured and could operate in accordance with the invention.

Example 10

Grinding wheels

Were used agglomerate samples A7 and A8 to produce grinding wheels (finished size 5.0 X 2.0 X 0.625 - 1.5 inch rim (12.7 X 5.08 X 1.59 -3.81 cm rim). For wheels W12 and W13, was used agglomerate sample screened to a size distribution range of -10 / + 20mesh. For wheel W14, there was used an agglomerate sample screened to a particle size distribution range of -14 / + 20 mesh. It was made the experimental abrasive wheels following the procedure described in Example 7, above. The finished wheels were tested in terms of security according to a commercially practiced speed test to ensure that the wheels had sufficient mechanical strength for rotational movement when mounted on a grinding machine and sufficient mechanical strength for the grinding operation. All experimental wheels survived the test speed of 6308 rev / min and, thus, had sufficient mechanical strength for surface grinding operations. The composition of the wheels (including volume percentage of abrasive, a binder and a porosity in the fired wheels) is described in Table 10-1.

Table 10-1: characteristics of abrasive wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D00961.tif" id="idf0034" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00971.tif" id="idf0035" />

a 46% by vo urn abrasive grain, the comparative wheels contained a greater volume percentage of abrasive grain (that is to say, 16 volume% more) than the experimental wheels made with 30 volume% abrasive grain.

b Values ​​for the volume percent of binder experimental wheels include the volume percent of the agglomerating resin materials used on the grains to make the agglomerates and the volume percentage of the binders used to make the grinding wheels.

c Comparative wheel samples were commercial product formulations obtained from Saint-Gobain Abrasives, Inc., Worcester, MA and sold under the alphanumeric designations wheels indicated for each in Table 10-2. The wheels contained phenolic resin binder, CaF2, hollow spheres mullite abrasive grain 38A alumina and had a hardness of quality (commercial scale of the Norton Company) L as shown.

The permeability to fluid (air) is given in units of cc / sec / inch water and is measured with a 1.1 cm nozzle by the method described in U.S. Patent Nos 5 738 696 and 5 738 697.

Visual observation of the fired experimental wheels, as in the previous Examples 8 and 9, demonstrated migration of the binder in the void areas at the surface or within the agglomerates. The net result was the creation of a composite structure, containing an abrasive grain of matrix / binder within a continuous phase consisting of porosity of an interconnected nature of.

These experimental wheels were tested in a surface grinding operation and found to be suitable for commercial use. Experimental wheels were tested against comparative wheel described in Table 10-1 that is used commercially in surface grinding operations. The comparative wheel had the same size of ribs, the same abrasive grain and binder types and was otherwise appropriate for the evaluation of the experimental wheels in a surface grinding study, but it was made without agglomerates.

The conditions and results of the grinding test are given below and in Table 10-2.

Terms correction:

Machine: Rail Grinder; maximum power 45 HP correction mode: face grinding (disc simulation test) Grinding wheel speed: 4202 r / min; surface velocity of 5500 feet per minute (27.9 m / sec)

Working speed 6 rev / min (75.4 SFPM / 0.383 m / sec) Input rate: 0.0010 inch / rev (0.0254 mm / rev), 0.0014 inches / rev (0.0356 mm / rev), 0.0020 inches / rev (0.0508 mm / s) and 0.0027 inch / rev (0.0686 mm / rev)

Rectification time: 15 minutes at each feed rate; 45 hp Apparition sparks: 10 sec

Coolant: Trim Clear, 2% ratio with deionized well water.

Material of the workpiece: AISI 1070 Steel 48 inch OD (1.22 m) X46,5 DI inches (1.18 m) x 0.75 inches (1.91 cm) board, Brinell hardness HB 302 Surfacing: no

Table 10-2: Results of grinding test

<img img-format="tif" img-content="drawing" file="LU91110A1D00981.tif" id="idf0036" />

<img img-format="tif" img-content="drawing" file="LU91110A1D00991.tif" id="idf0037" />

to the fraction of volume percentage G / abrasive ratio is a measure of the grinding performance the grain in the wheel. The calculation normalizes the grinding performance to account for the significant differences in terms of volume percentage of abrasive grain among the experimental and comparative wheels. It can be easily observed that the abrasive grain in the experimental wheels provides significantly better grinding efficiency on a volume fraction basis (that is to say, less grain is needed to deliver the same level of efficiency rectification).

For the experimental wheels, the power consumed was slightly higher, but the WWR was significantly lower than for comparative wheels. It is considered that if the experimental wheels were operated at lower MRR used for comparative wheels, the experimental wheels have absorbed less energy.

Again, compared to the comparative wheels, the experimental wheels provide significantly better grinding efficiency on a basis of the volume fraction of abrasive grain (that is to say, less grain is needed to deliver the same level efficiency of rectification). This result defies the conventional wisdom in bonded abrasives technology that a higher grade wheel will resist wear and provide a service life of the grinding wheel and a better grinding efficiency than a lower quality wheel (softer) .

Example 11

Grit / organic binder agglomerates

Variety were used agglomerating materials (as described in Table 11-1, below) to make agglomerated abrasive grain samples A9-A13 (Table 7-1). As in the previous Example 7, these agglomerates were prepared from a mixture of abrasive grain, bond-containing material of the phenolic resin (Durez resin 29-717 Varcum®, density 1.28 g / cc, obtained from from Durez Corporation, Dallas, Texas), together with the filler listed in Table 11-1. We used grain and agglomerating materials in the amounts described in Table 11-1. We prepared all samples with abrasive grain 38A alumina, silane-treated, fondue, 80 grit size, obtained from Saint-Gobain Ceramics &amp; Plastics, Inc., Worcester, MA, USA.

Was placed grain and resin bond material in the bowl of a high shear Eirich mixer (model number RV-02 manufactured by the Eirich Company, Gurnee, IL). The mixture was initiated at a bowl speed set at 64tr / min and at a blade speed set at 720tr / min. While mixing were sprayed with sufficient solvent (furfural) in the form of a mist, at a controlled rate, the grain mixture and bonding material to cause the grains and the binder material to agglomerate. Was continued spraying the solvent mixture until the grains and the bonding material had formed agglomerates (that is to say, spray at a rate of 15 to 20 g / min for 7 minutes on a batch including 2.25 kg grain together with the quantity of bonding material indicated in Table 11-1). The spraying was conducted with a Tool Mist Coolant Generator, obtained from Wesco Company, Chatsworth, CA. The process of agglomeration was carried under atmospheric conditions at room temperature.

After agglomeration in the mixer, the wet agglomerated abrasive samples of grain were screened through a sieve to US standards of 3.5 and dried overnight under ambient conditions. Then was again screened samples to produce a granule distribution of -20 / + 45 and distributed in a single layer on a baking tray coated fluoropolymer (approximately 45 x 30 cm). The agglomerates were then placed in an oven under atmospheric conditions, the temperature was raised to a maximum temperature of 160 ° C, and the agglomerates to the maximum temperature was maintained for 30 minutes to cure the resin bond material. We drove the agglomerates cooked under a 1.5 inch steel bar operated manually to partially crush and separate larger agglomerates into agglomerates smaller and then screened to the desired particle size distribution.

The production of agglomerates for use in free flow, defined as granules having a size distribution of -20 to +45 mesh (sieve size standards of USA) was&gt; 90% by weight of the total weight of the grain mixture before agglomeration.

The agglomerates were tested for loose the settlement density (LPD), relative density and size distribution and the visually characterized, before and after they have been used to manufacture the abrasive tools. The results are shown in Table 7-1.

These agglomerates had LPD characteristics, density and particle size distribution suitable for use in the commercial manufacture of abrasive grinding wheels. Cooked agglomerates finished had three-dimensional shapes varying among triangular shapes, spherical, cubic, rectangular, cylindrical and other geometric shapes. Agglomerates consisted of a plurality of individual abrasive grits (e.g., 2 to 40 grains) agglomerated together by the binder resin material of the contact points grain to grain. The structures of the agglomerates were sufficiently resistant to compaction to retain a three dimensional character after being subjected to mixing and molding of the abrasive wheel (that is to say, an insignificant portion (e.g., &lt;20% by weight) of the agglomerates was reduced to individual abrasive grit structures during processing of the grinding wheel). It was observed that the agglomerates made with a combination of resin and filler materials were less tacky and easier to separate than the agglomerates made with resin and no filler. In fact, slightly smaller amounts of solvent were needed when filler was added to the resin.

Thus, with minor modifications, the same methods used to make agglomerates with phenolic resin binders materials could also be used to make abrasive grain agglomerates with organic binding materials when inorganic filler materials (desired for incorporation in the grinding wheel) had been added to organic binder materials.

Table 11-1: Material used in caking agglomerates A9 to A13

<img img-format="tif" img-content="drawing" file="LU91110A1D01021.tif" id="idf0038" />

a The phenolic resin was Durez Varcum'8'29-717 the resin in Durez Corporation, Dallas, Texas.

b The filler was obtained from Min-Chem Canada, Inc., Oakville Ontario Canada in a particle size &lt;45 microns (-325 mesh) and mixed with the powdered resin component prior to the addition of grain and liquid material.

Grinding wheels

Were used agglomerate samples A9 to A13 to produce grinding wheels (finished size 5.0 X 2.0 X 0.625 inch -1.5 edge 12,7X5,08X 1.59 to 3.81 cm edge). Was manufactured experimental abrasive wheels following the procedure described in Example 7, above. The finished wheels were tested in terms of security according to a commercially practiced speed test to ensure that the wheels had sufficient mechanical strength for rotational movement when mounted on a grinding machine and sufficient mechanical strength for the grinding operation. All experimental wheels survived the test speed of 6308 rev / min and, thus, had sufficient mechanical strength for surface grinding operations. The composition of the wheels (including volume percentage of abrasive, a binder and a porosity in the fired wheels) is described in Table 11-2.

Table 11-2: Characteristics of abrasive wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D01031.tif" id="idf0039" />

<img img-format="tif" img-content="drawing" file="LU91110A1D01041.tif" id="idf0040" />

aA 46% by voume of abrasive grain, the comparative wheels contained a greater volume percentage of abrasive grain (that is to say, 16 volume% more) than the experimental wheels made with 30 volume% abrasive grain .

b The values ​​for the volume percentage of the binder of the experimental wheels include the volume percent of the agglomerating resin materials used on the grains to make the agglomerates and the volume percentage of the binders used to make the grinding wheels.

c samples C5L comparative wheel, and C5P C5T were commercial product formulations obtained from Saint-Gobain Abrasives, Inc., Worcester, MA and sold under the alphanumeric designations wheels indicated for each in Table 10-2. The wheels contained phenolic resin binder, CaF2, hollow spheres mullite abrasive grain 38A alumina and had a hardness of quality (commercial scale of the Norton Company) L, P or T, as indicated.

The permeability of the fluid (air) is given in units of cc / sec / inch water and is measured with a 1.1 cm nozzle by the method described in U.S. Patent Nos 5 738 696 and 5 738 697. e The wheel C5D sample lacked strength to pass commercial safety testing.

These experimental wheels were tested in a surface grinding operation and discovered as suitable for commercial use. Experimental wheels were tested against the comparative wheels C5L, C5P and C5T described in Table 11-2, that are commercial products sold for use in surface grinding operations. The comparative wheels had the same size coasts, abrasive grain and binder types and were otherwise suitable for evaluating the experimental wheels in a surface grinding study, but they were made without agglomerates. It was also included in this grinding test of experimental wheel W5 and comparative wheel CLP from Table 8-1.

In a later test under identical conditions of rectification, we tested two additional comparative wheels (C5D and C5J). Was manufactured comparative wheels G5d C5J and following the method described for experimental wheels of Example 7, except that the compositions shown in Table 11-2 were used instead of those set out in Example 7. It was these wheels made in softer wheel grades (D and J) and tested in order to compare the performance of the experimental wheel relative to a conventional wheel having a corresponding quality (ie, the percentage by volume of grain, binder and identical or similar porosity). An allocation qualities was carried out based on the binder composition selected for the wheel, together with the volume percentages of abrasive grain, binder and porosity in the finished wheel. Grinding test conditions and results are given below and in Table 11-2.

Terms correction:

Machine: Rail Grinder; maximum power 45 HP correction mode: face grinding (disc simulation test) Grinding wheel speed: 4202 r / min; surface velocity of 5500 feet per minute (27.9 m / sec)

Working speed: 3 rev / min; SFPM 37.7 / 0.192 m / sec input rate: 0.0020 inch / rev (0.0508 mm / s), 0.0027 inch / rev (0.0686 mm / rev) and 0.004 inch / rev (0 , 1016 mm / rev)

Duration of grinding: 15 minutes at each feed rate sparks Appearance: 10 sec

Coolant: Trim Clear, 2% ratio with deionized well water

Material of the workpiece: AISI 1070 Steel 48 inch OD

(1.22 m) X46,5 DI inches (1.18 m) x 0.75 inches (1.91 cm) board, HB hardness

302 Brinell

Surfacing: no

Table 11-2: rectification test results

<img img-format="tif" img-content="drawing" file="LU91110A1D01061.tif" id="idf0041" />

<img img-format="tif" img-content="drawing" file="LU91110A1D01071.tif" id="idf0042" />

3 fraction in volume percent G / abrasive ratio is a measure of the grinding performance the grain in the wheel. The calculation normalizes the grinding performance to account for the significant differences in terms of volume percentage of abrasive grain among the experimental and comparative wheels. It can be easily observed that the abrasive grain in the experimental wheels provides significantly better grinding efficiency on a volume fraction basis (that is to say, less grain is needed to deliver the same level of efficiency rectification).

b C5D the grinding wheels were tested and C5J at a later date in relation to the remaining samples, but under identical grinding test conditions.

The experimental wheels demonstrated slightly lower power but comparable WWR than the comparative wheels. This is a surprise given the grade differential (D versus L-T).

Once again, compared to the comparative wheels, the experimental wheels overall provided significantly better grinding efficiency on a volume fraction basis of abrasive grain (that is to say, less grain is needed to deliver the same level efficiency of rectification). The sample was C5J leads to higher MRR so that data concerning this wheel are consistent with the general trend. Samples C2P and W5D, tested in a separate grinding test, show better performance than the remaining wheels, but the differences between the experimental and comparative wheels are consistent with the general trend. These results are contrary to the conventional wisdom in bonded abrasives technology that a higher grade wheel having more grain will resist wear and provide a service life of the grinding wheel and a better grinding efficiency that a softer quality wheel.

Thus, experimental grinding wheels having sufficient mechanical strength to be commercially accepted, but comparatively low measurable hardness grades, could be manufactured by the invention and give effective grinding performance for commercial purposes.

Example 12

Abrasive Grain / Vitrified of agqlomérats

Used was a vitrified bond material (binder material A of Table 1-2) for the manufacture AV1 sample of agglomerate abrasive grain. The agglomerates were prepared from a mixture of abrasive grain and vitrified bond material by the rotary calcination method described in Example 1 except that was used 2.6 wt% of agglomerating material A for AV1 make the agglomerates and the grain of the abrasive grain was fused alumina 38A, 80 grit size, obtained from Saint-Gobain Ceramics &amp; Plastics, Inc., Worcester, MA, USA. Sintered agglomerates were wetted with an aqueous solution at 2% by weight of gamma-amino propyl triethoxysilane silane (Witco Corporation, Friendly, West Virginia) (9.2 ml / lb on grain agglomerates grain size 80) coat the agglomerates with silane, then dried at 102 ° C, and sieved to remove any clumps generated during the silane treatment.

The yield of the agglomerates used in free flowing, defined as granules having a size distribution of -20 / + 45 mesh (sieve size standards of USA) was 86% by weight of the total weight of the grain mixture before agglomeration. Were tested vitrified grain agglomerates for their loose packing density (LDP = 1.04), density (0.268) and size distribution (- 20 / + 45 mesh) and characterized visually before and after be used to manufacture abrasive tools.

These agglomerates had LPD characteristics, density and particle size distribution suitable for use in the commercial manufacture of abrasive grinding wheels. Cooked agglomerates finished had three-dimensional shapes varying among triangular shapes, spherical, cubic, rectangular, cylindrical and other geometric shapes. Agglomerates consisted of a plurality of individual abrasive grits (e.g., 2 to 40 grains) bonded together by vitrified bond material at the contact point grain to grain, together with visible void areas. The structures of the agglomerates were sufficiently resistant to compaction to retain a three dimensional character after being subjected to mixing and molding of the abrasive wheel (that is to say, an insignificant portion (e.g., &lt; 20% by weight) of the agglomerates was reduced to individual abrasive grains during the processing of the grinding wheel).

Grit / organic binder agglomerates

The abrasive grain were placed (38A grain, 80 grit size, obtained from Saint-Gobain Ceramics &amp; Plastics, Inc., Worcester, MA) and the binder resin material (material caking E, from Table 11-1 ) in the bowl of a high shear Eirich mixer (model number R07 manufactured by the Eirich Company, Gurnee, IL). The mixture was initiated at a bowl speed set at 460 rev / min (in the direction of clockwise) and set at a blade speed of 890 rev / min (in the opposite direction of the clockwise ). While mixing was sprayed in the form of a mist, sufficient solvent (furfural) at a controlled rate on the grain mixture and bonding material to cause the grains and the binder material to agglomerate. Was continued spraying solvent onto the mixture until all grains and the bonding material had formed agglomerates (that is to say, by spraying at a rate of 380 to 390 cc / min for a total 2.5 min on a batch including 49.5 kg grain together with the quantity of bonding material indicated in Table 12-1). Spraying was conducted on a Spraying Systems apparatus (model AutoJet 38660 obtained from Spraying Systems, Wheaton IL). The process of agglomeration was carried under atmospheric conditions, at room temperature.

Was passed twice through a cluster A14 six foot vibrating conveyor (Eriez Magnetics, model number HS / 115, Erie PA) to evaporate the solvent. Was then embedded with the agglomerate abrasive grain in bulk (80 grit, 38A) at an agglomerate portion and two parts loose abrasive and then placed in an oven (model number VRD-1- 90-1E home Despatch Industries, Minneapolis MN), under atmospheric conditions. The temperature was raised to a maximum temperature of 160 ° C, and the agglomerates to the maximum temperature was maintained for 30 minutes to cure the binder resin material. After cooking, it has seconded the abrasive loose agglomerates by the final sizing procedure.

Table 12-1: Characteristics of agglomerated granules

<img img-format="tif" img-content="drawing" file="LU91110A1D01101.tif" id="idf0043" />

is the percentage by volume of bonding material is a percentage of solids within the granules (that is to say, bonding material and grain) after curing, it does not include the percentage by volume of porosity. The volume percent of bonding material of the fired agglomerates was calculated by making an assumption of no internal porosity and no mix losses.

Grinding wheels

We used samples of agglomerate AV1 and A14 to make grinding wheels (finished size 5.0 X 2.0 X 0.625 - 1.5 inch rim (12.7 X 5.08 X 1.59 -3.81 cm rim). was manufactured experimental abrasive wheels following the procedure described in Example 7 were tested finished wheels in terms of security according to a commercially practiced speed test to ensure that the wheels had sufficient mechanical strength for rotational movement when attached to a grinding machine and sufficient mechanical strength for the grinding operation. All experimental wheels survived a test speed of 6308 rev / min and, thus, had sufficient mechanical strength for surface grinding operations. The composition of the wheels (including type and ratio of agglomerates, volume percent of the abrasive, the binder and porosity in the fired wheels) is described in Table 12-2.

Table 12-2: Characteristics of abrasive wheels

<img img-format="tif" img-content="drawing" file="LU91110A1D01111.tif" id="idf0044" />

<img img-format="tif" img-content="drawing" file="LU91110A1D01121.tif" id="idf0045" />

a A 46 volume% abrasive grain, the comparative wheels contained a larger volume percentage abrasive grain (that is to say, 16 volume% more) compared to the experimental wheels made with 30 volume% abrasive grain. b The values ​​for the volume percentage of the binder of the experimental wheels include the volume percent of the agglomerating resin materials used on the grains to make the agglomerates and the volume percentage of the binders used in grinding wheels. c samples C5L comparative wheel, and C5P C5T were commercial product formulations obtained from Saint-Gobain Abrasives, Inc., Worcester, MA and sold under the alphanumeric designations wheels shown in the table for each ΙΟΣ, The wheels contained phenolic resin binder, CaF2, hollow spheres mullite abrasive grain 38A alumina and have a hardness grade (commercial scale of the Norton Company) L, P or T, as indicated.

The permeability of the fluid (air) is given in units of cc / sec / inch water and is measured with a 1.1 cm nozzle by the method described in U.S. Patent Nos 5 738 696 and 5 738 697.

Visual observation of the fired experimental wheels, as in the previous Example 7, demonstrated migration of the binder within the areas of intra-agglomerate void. Photomicrographs were taken (magnification 46X) of the grinding surfaces of comparative wheel C6L and the experimental wheel W20D (Table 12-2). These images appear as Figures 4 and 5. It can be seen from Figures 4 (comparative wheel) and 5 (experimental wheel) that the porosity (darker areas) in the abrasive composite of the invention exist in the form of a continuous phase of interconnected channels. The abrasive grain and the binder appear as a reticulated network in which abrasive grain is anchored in the organic binder materials. In contrast, the comparative wheel has a substantially uniform structure wherein porosity is hardly visible and appears as a discontinuous phase.

These experimental wheels were tested in a surface grinding operation and found them suitable for commercial use. Experimental wheels were tested against the comparative wheels described in Table 12-2, that are used commercially in surface grinding operations. A quality range of from I to T was chosen on the Norton hardness qualities for the comparative wheels to confirm a quality shift observed in the experimental wheels (that is to say, a lower hardness grade in the experimental wheels could behave as well as a higher hardness quality standard wheels). The comparative wheels had the same coasts of magnitude, the same types of abrasive grit and were otherwise suitable for evaluating the experimental wheels in a surface grinding study, but they were made without agglomerates. The conditions and results of the grinding test are given below and in Table 12-3.

Terms correction:

Machine: Rail Grinder; maximum power 45 HP correction mode: face grinding (disc simulation test) Grinding wheel speed: 4202 r / min; superficial velocity of 5,500 feet per minute (27.9 M / sec)

Working speed: 3 rev / min; SFPM 37.7 / 0.192 m / sec input rate: 0.0027 inch / rev (0.0686 mm / rev) and 0.004 inch / rev (0.1016 mm / rev)

Rectification time: 15 minutes at each feed rate sparks Appearance: 10 sec

Coolant: Trim Clear, 2% ratio with deionized well water

Materials of the workpiece: AISI 1070 Steel 48 inch OD (1.22 m) x 46.5 inches DI (1.18 m) x 0.75 inches (1.91 cm) board, Brinell hardness HB 302 Surfacing : no

Table 12-3 Results of the grinding tests

<img img-format="tif" img-content="drawing" file="LU91110A1D01141.tif" id="idf0046" />

<img img-format="tif" img-content="drawing" file="LU91110A1D01151.tif" id="idf0047" />

to the fraction of volume percentage G / abrasive ratio is a measure of the grinding performance the grain in the wheel. The calculation normalizes the grinding performance to account for the significant differences in terms of volume percentage of abrasive grain among the experimental and comparative wheels. It can be easily observed that the abrasive grain in the experimental wheels provides significantly better grinding efficiency on a volume fraction basis (that is to say, less grain is needed to deliver the same level of efficiency rectification).

The test results demonstrate the experimental wheels having a D or G grade on the Norton Hardness quality scale behave in an equivalent manner to the comparative wheels having a harder grade quality P to T. The performance of wheels Experimental was particularly surprising because these wheels contained only 3% by volume of abrasive grain, whereas the comparative wheels contained 46 volume% abrasive grain. Thus, the wheels of the invention maximize the grinding performance of the individual grains, increasing the performance of the grains to a significant level.