Composite polycrystalline substance cutting tool and manufacture thereof

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a composite polycrystalline cutting tool composed of cubic boron nitride (CBN) and polycrystalline diamond synthetically grown by a low-pressure vapor phase method, and a method for producing the same.

【0002】

[Conventional technology]

The CBN sintered body has the second highest hardness after diamond and has low reactivity with iron-based metals. In addition, cubic boron nitride (CBN) has the second highest thermal conductivity after diamond, and the CBN sintered body also has high thermal conductivity and excellent high-temperature strength. For this reason, CBN sintered bodies are widely used for cutting tools of cutting tools using various iron-based high-hardness materials.

【0003】

The structure of the tool cutting edge using the conventional CBN sintered body is classified into the following three types. Type 1: A structure in which a base metal (usually WC-Co cemented carbide) sintered integrally with CBN powder during sintering and a tool support are joined by brazing to form a tool cutting edge.

【0004】

Type 2: A structure in which a CBN sintered body is brazed directly to a tool support to form a tool cutting edge.

【0005】

Type 3: A structure in which the entire tool edge is a CBN sintered body. The tool cutting edge having these three types of CBN sintered bodies is used properly according to the characteristics of each material and structure.

【0006】

[Problems to be Solved by the Invention]

As described above, the CBN sintered body has excellent performance and is widely used as a tool cutting tool for cutting tools made of various iron-based high-hardness materials.

【0007】

However, in recent years, it has been desired to increase the cutting speed for the purpose of improving production efficiency. In addition, due to consideration for the global environment, dry cutting that does not use cutting fluid is becoming mainstream. In order to meet these two demands, it is necessary to perform machining under conditions where the cutting temperature is higher than before, and the requirements for the thermal characteristics of the material used for the tool cutting edge are also becoming stricter.

【0008】

The requirement for the thermal properties of the material used for the tool cutting edge cannot be satisfied even with the conventional CBN sintered body, and conventionally, there has been no tool material having a practical tool life.

【0009】

Therefore, an object of the present invention is to provide a composite polycrystal cutting tool having excellent thermal properties such as high thermal conductivity with respect to a conventional tool material even in high-speed cutting and having a remarkably long tool life, and a method for manufacturing the same. There is.

【0010】

[Means for solving problems]

In view of the above problems, we have developed and studied to obtain a cutting tool that can suppress the rise in tool cutting edge temperature by having excellent thermal characteristics and can suppress the wear promoted by the thermal influence. As a result, the following invention was achieved.

【0011】

That is, a composite polycrystalline material of a CBN sintered layer and a polycrystalline diamond layer obtained by synthetically growing polycrystalline diamond on a CBN sintered body using a low-pressure vapor phase method is formed, and this composite polycrystalline material is formed. It has been found that the temperature of the tool cutting edge can be reduced by brazing the polycrystalline diamond layer side of the material to the tool support and using it as the tool cutting edge. (Structure) In the composite polycrystalline cutting tool and its manufacturing method based on the present invention, the CBN sintered layer is used as a base material, and the polycrystalline is synthetically grown on the CBN sintered layer by the low pressure vapor phase method. A diamond layer is provided, and the polycrystalline diamond layer is bonded to the tool support using a brazing layer.

【0012】

The formation of the polycrystalline diamond layer on the CBN sintered body layer can be easily synthesized and grown by the CVD (chemical vapor deposition) method currently widely used, and the CBN sintered body layer and polycrystalline by a known technique. It is possible to produce a diamond layer having sufficient bonding strength for practical use.

【0013】

When a composite polycrystalline material based on the present invention is used for the tool cutting edge, it is necessary to have a shape suitable for the tool cutting edge. As this means, a method of cutting a CBN sintered body into a shape suitable for the tool cutting edge shape in advance by a discharge processing machine and then growing a polycrystalline diamond on the CBN sintered body by a CVD method, on a large-area CBN sintered body. There are two methods, first, the polycrystalline diamond is grown by the CVD method and then cut by the laser. Regardless of which method is used, the functional difference as the composite polycrystalline material of the present invention is. Absent. (Action) According to the composite polycrystalline cutting tool and the manufacturing method thereof based on the present invention, it is possible to dramatically extend the life of the tool cutting edge even in high-speed cutting because the rise in the tool cutting edge temperature can be suppressed. The inventors of this patent application have very high thermal conductivity in a composite polycrystalline material obtained by combining a CBN sintered body and polycrystalline diamond, and extremely suppress the temperature rise of the tool cutting edge. It has been found that it can be used as a material for tool cutting edges with excellent thermal properties. The operation of the composite polycrystalline cutting tool based on the present invention and the method for producing the same will be described in detail below. In the composite polycrystalline cutting tool based on the present invention, the work material uses a CBN sintered body portion that exhibits excellent cutting performance with respect to the iron-based work material. On the other hand, since polycrystalline diamond has extremely high thermal conductivity, it acts as a heat sink that dissipates heat generated between a tool cutting edge made of a CBN sintered body and a work material during processing.

【0014】

Therefore, since the heat generated during cutting is dissipated by the polycrystalline diamond layer, the temperature rise of the tool cutting edge made of the CBN sintered body is suppressed, the thermal wear is suppressed even in high-speed cutting, and the life of the CBN sintered body is suppressed. Will improve dramatically.

【0015】

In the composite polycrystalline material of the present invention, the thickness of the CBN sintered body is 500 μm or more and 2.5 mm or less, preferably 800 μm or more and 2 mm or less, and more preferably 800 μm or more and 1.2 mm or less.

【0016】

If the thickness of the polycrystalline diamond layer is 10 μm or more and 2 mm or less, and the thickness ratio of the CBN sintered body layer to the polycrystalline diamond layer is in the range of 0.3 CBN sintered body layer / polycrystalline diamond layer 50. The heat dissipation effect of the polycrystalline diamond layer is exhibited.

【0017】

Further, the thickness of the polycrystalline diamond layer is preferably 100 μm or more and 2 mm or less, and the thickness ratio of the CBN sintered body layer to the polycrystalline diamond layer is in the range of 0.4 CBN sintered body layer / polycrystalline diamond layer 20. Preferably, the thickness of the polycrystalline diamond layer is 100 μm or more and 1 mm or less, and if the thickness ratio of the CBN sintered body layer to the polycrystalline diamond layer is in the range of 0.8 CBN sintered body layer / polycrystalline diamond layer 12, there are many. The heat dissipation effect of the crystalline diamond layer is fully exhibited.

【0018】

In the present invention, the thicker the polycrystalline diamond layer, the greater the heat dissipation effect, but the effect corresponding to the high cost due to the thick growth of the polycrystalline diamond was not recognized. Therefore, when considering the balance between cost and performance, the above range is a suitable range.

【0019】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments based on the present invention will be described with reference to FIG. FIG. 1 is a conceptual diagram showing a cross-sectional structure of a composite polycrystalline cutting tool according to an embodiment based on the present invention. However, the technical scope of the present invention is not limited to the structure shown in FIG.

【0020】

In FIG. 1, the composite polycrystalline cutting tool according to the present embodiment has a tool support 4, and a composite polycrystalline material is formed on the tool support 4 with a brazing material 3 interposed therebetween. There is. This composite polycrystalline material has a polycrystalline diamond layer 2 and a CBN sintered body 1 synthetically grown by a vapor phase synthesis method, and the polycrystalline diamond layer 2 is arranged on the tool support 4 side.

【0021】

The growth of the polycrystalline diamond layer 2 on the CBN sintered body layer 1 can be easily realized by the CVD (chemical vapor deposition) method currently widely used, and the CBN sintered body layer 1 and the CBN sintered body layer 1 are grown by a known technique. It is possible to produce a polycrystalline diamond layer 2 having sufficient bonding strength for practical use.

【0022】

As shown in FIG. 1, when a composite polycrystalline material is used for the tool cutting edge, it is necessary to have a shape suitable for the tool cutting edge. As this means, a method of cutting a CBN sintered body into a shape suitable for the tool cutting edge shape in advance by a discharge processing machine and then growing a polycrystalline diamond on the CBN sintered body by a CVD method, a large-area CBN sintering method. There are two methods of first growing polycrystalline diamond on the body layer by the CVD method and then cutting it with a laser. Regardless of which method is used, the function of the composite polycrystal of the present embodiment is used. There is no difference above.

【0023】

Hereinafter, specific examples of a method for manufacturing a composite polycrystalline cutting tool having the above structure will be described. (Example 1) TiN and aluminum were mixed at a weight ratio of 4: 1 using a cemented carbide pot and a ball to obtain a binder powder. Next, the binder powder and CBN powder were mixed in a volume ratio of 3: 2 (CBN powder was 40% by volume), filled in a molybdenum container, and placed at a pressure of 50 kb and a temperature of 1400 ° C for 20 minutes. Sintered. Mo adhering to the sintered body side was scraped off to obtain a CBN sintered body layer having a thickness of 1.5 mm, which is a polycrystalline sintered body.

【0024】

The binder powder shall be at least one selected from the group consisting of nitrides, carbides, borides, oxides and solid solutions of these in Groups 4a, 5a and 6a of the Periodic Table, and aluminum and / or aluminum. It is possible to use a binder powder composed of a compound. Further, in the blending of the binder powder and the CBN powder, unavoidable impurities shall be mixed.

【0025】

Polycrystalline diamond was produced by the hot filament CVD method, which is a low-pressure vapor phase method, using the CBN sintered body layer cut into the shape of a cutting tool cutting tool by an electric discharge machine as a base material. The conditions at this time are methane 300 sccm, hydrogen 1000 sccm, substrate temperature 900 ° C, and pressure 100 Torr.

【0026】

Table 1 shows the thickness of the polycrystalline diamond layer synthetically grown on the CBN sintered body layer according to the growth time (time) of the polycrystalline diamond layer (Document No. 1-1 to 1-6). μm) and the thickness ratio of the CBN sintered body layer to the polycrystalline diamond layer (CBN sintered body layer / polycrystalline diamond layer) are shown. The thickness of the CBN sintered body layer in this example is 1500 μm.

【0027】

[table 1]

<img file="JP2000296403A_D0001.tif" />【0028】

After joining the polycrystalline diamond layer side of the composite polycrystal consisting of these CBN sintered body layers and the polycrystalline diamond layer to the tool support using an Ag-Cu-Ti-based brazing material, the cutting tool tip Processed into the shape of (SNGN120408).

【0029】

For comparison, a cutting chip having the same shape was produced from a polycrystalline material in which a polycrystalline diamond film was not grown only with the CBN sintered body layer prepared by the above method (Comparative Example 1).

【0030】

Cutting performance was evaluated using each cutting tip. As the work material, SUJ2 having a hardness of HRC63 was used. Table 2 summarizes the results of cutting the outer circumference of this work material for 20 minutes under the conditions of "cutting speed 300 m / min", "cutting speed 0.2 mm", "feed speed 0.05 mm / rev", and "dry type".

【0031】

[Table 2]

<img file="JP2000296403A_D0002.tif" />【0032】

As shown in Table 2, although the evaluation of the cutting tip in Comparative Example 1 is "x" and the evaluation of the cutting tip in Document No. 1-1 is "", Document Nos. 1-2 to 1- The evaluation of the cutting tip of 6 was "". (Example 2) Co and WC were mixed at a weight ratio of 2: 1 using a cemented carbide pot and a ball to obtain a binder powder. Next, the binder powder and CBN powder are mixed in a volume ratio of 1: 9 (CBN powder is 90% by volume), filled in a Mo container, and charged at a pressure of 55 kb and a temperature of 1400 ° C for 20 minutes. Sintered. Mo adhering to the sintered body side was scraped off to obtain a CBN sintered body layer having a thickness of 2 mm, which is a polycrystalline sintered body.

【0033】

The binder powder is not limited to the binder powder of Co and WC, but at least one of Fe, Ni, Co, and Al, their nitrides, and borides, and Group 4a, 5a, and 6a of the Periodic Table. It is possible to use a binder powder composed of at least one of the carbides of the above. Further, in the blending of the binder powder and the CBN powder, unavoidable impurities shall be mixed.

【0034】

A polycrystalline diamond film was synthetically grown by a hot filament CVD method, which is a low-pressure vapor phase method, using a CBN sintered body layer cut into a cutting tool cutting edge shape by an electric discharge machine as a base material. The conditions at this time are methane 300 sccm, hydrogen 1000 sccm, substrate temperature 900 ° C, and pressure 100 Torr.

【0035】

Table 3 shows the thickness (μm) of the polycrystalline diamond layer formed on the CBN sintered body layer according to the growth time (time) of the polycrystalline diamond layer (Document No. 2-1 to 2-4). ) And the thickness ratio of the CBN sintered body layer to the polycrystalline diamond layer (CBN sintered body layer / polycrystalline diamond layer). The thickness of the CBN sintered body layer in this example is 2000 μm.

【0036】

[Table 3]

<img file="JP2000296403A_D0003.tif" />【0037】

After joining the polycrystalline diamond layer side of the composite polycrystal consisting of these CBN sintered body layers and the polycrystalline diamond layer to the tool support using a Cu-Ni-Ti-based brazing material, the cutting tool tip Processed into the shape of (SNGN120408).

【0038】

For comparison, a cutting chip having the same shape was prepared from a polycrystalline material in which a polycrystalline diamond film was not grown only with the CBN sintered body layer prepared by the above method (Comparative Example 2).

【0039】

Cutting performance was evaluated using each cutting tip. Gray cast iron (FC250) was used as the work material. Table 4 summarizes the results of cutting the outer circumference of this work material under the conditions of "cutting speed 1000 m / min", "cutting speed 0.3 mm", "feed speed 0.25 mm / rev", and "wet". The cutting length in Table 4 indicates the cutting distance to the tool life.

【0040】

[Table 4]

<img file="JP2000296403A_D0004.tif" />【0041】

As shown in Table 4, the evaluation of the cutting tip in Comparative Example 2 is "x", and the evaluation of the cutting tip in Material No. 2-1 and Material No. 2-2 is "", but the material No. The evaluation of cutting tips of .2-3 to 2-4 was "".

【0042】

In each of the above examples, the polycrystalline diamond layer is bonded to the tool support by using at least one metal of Group 4a to 7a of the Periodic Table and Au, Ag, Cu, Pt, Pd and Ni. It was carried out in a vacuum or an inert gas atmosphere using a raw material containing at least one of them as a constituent and having a melting point of 800 ° C to 1000 ° C.

【0043】

The proportion of CBN powder in the binder powder in Example 1 is 40% by volume, and the proportion of CBN powder in the binder powder in Example 2 is 10% by volume, but the proportion of CBN powder in the binder powder is , It is possible to apply in the range of 10% by volume or more and 90% by volume or less.

【0044】

Further, the thickness of the CBN sintered body, the thickness of the polycrystalline diamond layer, and the thickness ratio of the CBN sintered body layer to the polycrystalline diamond layer in Examples 1 and 2 are examples, and the evaluation results of Tables 1 and 2 above are shown. From the viewpoint of fully exhibiting the heat dissipation effect of the polycrystalline diamond layer and the balance between cost and performance, the thickness of the polycrystalline diamond layer is 10 μm or more and 2 mm or less, and the CBN sintered body layer and the polycrystalline diamond. The thickness ratio of the layers may be in the range of 0.3 CBN sintered layer / polycrystalline diamond layer 50, preferably the thickness of the polycrystalline diamond layer is 100 μm or more and 2 mm or less, and the CBN sintered layer and polycrystalline. The thickness ratio of the diamond layer is preferably in the range of 0.4 CBN sintered layer / polycrystalline diamond layer 20, more preferably the thickness of the polycrystalline diamond layer is 100 μm or more and 1 mm or less, and the CBN sintered layer and polycrystalline. The thickness ratio of the diamond layer may be in the range of 0.8 CBN sintered body layer / polycrystalline diamond layer 12.

【0045】

As described above, the above-described embodiment disclosed this time is an example in all respects and is not limiting, and the technical scope of the present invention is defined not by the above description but by the claims. Includes scope and equal meaning and all changes within the scope.

【0046】

[Effect of the invention]

According to the composite polycrystalline cutting tool of the present invention and its manufacturing method, the excellent thermal characteristics of the CBN sintered body are further enhanced by the heat dissipation effect of the polycrystalline diamond, and it is a conventional tool material in high-speed machining. It is possible to process with an extremely long life compared to. Therefore, high-efficiency machining becomes possible and industrially useful effects are brought about.

[Simple explanation of drawings]

[Figure 1]

It is a conceptual diagram which shows the cross-sectional structure of the composite polycrystalline cutting tool in embodiment based on this invention.

[Explanation of symbols]

1: CBN sintered body layer 2: Polycrystalline diamond layer 3: Raw material 4: Tool support