Method for producing a metallic workpiece with at least one cavity

0001The invention relates to a method for producing a metal component with at least one recess, the recess being exposed very economically and efficiently by the method.

0002Workpieces with recesses, such as cavities, recesses, undercuts, cavities and the like can be produced not only by machining processes, but also by regenerative processes. When using a regenerative process, the area of ​​the workpiece that will later represent the recess after completion of the workpiece is provided with a carrier material, also called a support structure, which at least partially fills the future recess during the construction of the workpiece. After the work piece has been built up, the carrier material is removed. For example, teach<patcit id="pcit0001" dnum="WO2008125352A1"><text>WO 2008/125352 A1</text></patcit> and <patcit id="pcit0002" dnum="DE19716524A1"><text>DE 19716524 A1</text></patcit>that the carrier material can be detached from the recess. An aqueous medium, for example having an acidic pH, can be used in these methods. However, such methods for uncovering a recess are expensive with regard to the space requirement and the reaction time. The workpieces must not react in any way with the medium to be used. In particular, acidic media, which can cause corrosion of the metallic workpieces, are disadvantageous here.

0003<patcit id="pcit0003" dnum="EP0951579A2"><text>EP 0951579 A2</text></patcit> describes a method of fabricating hollow objects, comprising the steps of: fabricating an alloy sub-structure to provide required structural strength, the sub-structure including cavities intended to correspond to the internal dimensions of the finished object; Filling the cavities with a filler material and performing a heat treatment.

0004<patcit id="pcit0004" dnum="EP0968317A1"><text>EP 0968317 A1</text></patcit> discloses a method of making channels within an article, the method comprising the steps of:<ul id="ul0001" list-style="dash" compact="compact"><li>Providing a substrate having a substrate surface with a plurality of grooves;</li><li>Filling at least a portion of at least one of the grooves with a filler, the filler having a surface;</li><li>Forming a skin on the filler surface; and</li><li>Removing the filler from at least one of the grooves, the skin remaining substantially undamaged, whereby at least one channel is formed within the substrate so that a cooling medium can flow therethrough to remove heat from the substrate and the skin, characterized in that the step of forming a skin itself includes the following steps:<ul id="ul0002" list-style="dash" compact="compact"><li>Forming a vapor from a fuming agent; and</li><li>Condensation of the vapor on the substrate surface and the filler surface.</li></ul></li></ul>

0005<nplcit id="ncit0001" npl-type="s"><text>Hironori SUZUKI, Satoshi NISHIDA, Takayasu FUJIURA: "Newly Developed Iron-based Poweder Mixture, High Density SEGLESS, for High Density Compaction", KOBELCO TECHNOLOGY REVIEW, pages 24-29 (2011-12-30</text></nplcit>) reveals a dewaxing process. As an exemplary lubricant, KPA (a polyhydroxyamide) is disclosed, which is mixed with iron powder to test for dewaxing. A method for producing a metal component with a recess is not disclosed, even if cavities remain in the (sintered) iron due to the introduction and subsequent removal of the KPA.

0006It is therefore an object of the invention to specify a method for producing a metal component with at least one recess, which can be carried out simply, without high technical effort, with high efficiency, without the metal component being damaged in the process.

0007This problem is solved by the features of the independent claim. The dependent claims contain advantageous embodiments and developments of the invention.

0008Thus, a method for producing a metal component with at least one recess is provided, which comprises the following steps: First, a metal component is placed in a heating device. The metal component can be produced in a conventional manner, for example by an injection molding process, such as, for example, cold gas spraying, and comprises at least one carrier material which at least partially fills a recess. In the context of the present invention, a recess is understood to mean any type of cavity, that is to say cavities, recesses, undercuts, channels and the like, which are deliberately provided in the metal component. This does not include pores of the metal component itself. The recess provided in the metal component can, after completion of the metal component, represent, for example, a cooling channel, that is to say generally a channel carrying a medium, and for example for the transport of reaction educts, reaction products, cooling media, including gases and liquids, or other media, such as hydraulic oils and the like. The recess can be formed in the metal component in a conventional manner. Furthermore, a plurality of cutouts can also be provided, which are designed similarly or have different shapes, arrangements and dimensions. The recess is at least partially, preferably completely, filled with a carrier material that preserves the spatial structure of the recess during the method for producing the metal component. Here, the carrier material is a metallic carrier material and / or a ceramic carrier material, the metallic carrier material being selected from: magnesium, aluminum, zinc, antimony, mixtures or alloys thereof.

0009Any heating device that is set up to receive the metal component together with the carrier material and to bring it to a temperature that is suitable for converting the carrier material at least partially into the gaseous state can be used as the heating device. A controllable oven is particularly suitable here.

0010In a step following the introduction or introduction of the metal component together with the carrier material into the heating device, at least a part of the carrier material is removed, exposing at least one area of ​​the recess. For this purpose, according to the invention, at least part of the carrier material is converted into the gas phase and condensed again in a condensation region whose temperature corresponds to or is below the solidus temperature of the carrier material. This procedure can be represented by the following reaction equations (reaction equilibria), where a first reaction equilibrium is numbered with a and a second reaction equilibrium with b:<chemistry id="chem0001" num="0001"><img file="EP3552756B1_D0001.tif" /></chemistry>

0011It can be seen from this that the carrier material, “M” for short, is in equilibrium, namely between its solid form, “M_s"and its gaseous form" M_G". The first reaction equilibrium a between M_s and M_G is in a warm area of ​​the heating device, so that the carrier material at least partially changes from its solid state to the gaseous state. This can be done by simple evaporation with the formation of a liquid intermediate phase, or by sublimation of the carrier material. A sublimation reaction is particularly advantageous here, since it avoids a liquid phase which is usually more voluminous and which could damage the surrounding metal component.

0012As soon as the carrier material is in the gaseous state, it is distributed in the heating device by diffusion. It is therefore removed from the recess, whereby the recess is at least partially exposed. As a result of the subsequent condensation of the gaseous carrier material by the second reaction equilibrium b, the product, namely M_G, withdrawn, so that the equilibrium is on M's side_G is moved. Further support material is thus transferred into the gas phase in order to restore the first reaction equilibrium, from which support material continues to be withdrawn by condensation.

0013The second reaction, that is to say the condensation of the gaseous carrier material, which is also present as an equilibrium reaction, takes place by condensing the gaseous carrier material in a condensation area. The condensation region has a temperature which corresponds to or is below the solidus temperature of the carrier material. The lower the temperature of the condensation area, the faster the condensation reaction takes place and the faster and more efficiently gaseous carrier material is withdrawn from the second reaction equilibrium while converting it again into the solid state, which in turn requires the removal of further gaseous carrier material from the recess (first reaction equilibrium) accelerates and entertains.

0014Thus, the carrier material is gradually removed from the recess without the addition of chemicals and thus in a very inexpensive, safe, economical and efficient manner and the recess is thus at least partially exposed.

0015These reactions of converting the carrier material into the gas phase and condensing the gaseous carrier material in a condensation area that is outside the metal component can be carried out until the recess is completely exposed. To streamline the time of the method, however, it is advantageous that only part of the carrier material is removed from the recess by the process described above, and residual constituents of the carrier material are removed, for example, by rinsing or blowing out.

0016The metal component is preferably designed as a steel component, since this gives the metal component very good mechanical properties.

0017According to an advantageous development, the condensation area is outside the heating device. This has the advantage that the recondensed carrier material is removed directly from the heating device and thus both the arrangement of the heating device and the process management are simple and easy to handle.

0018According to an alternative development, the condensation area lies within the heating device. This is possible, for example, by using a two-zone oven.

0019As a result, the heating device can be made more compact and therefore more space-saving.

0020Since most metal components are subjected to a heat treatment to improve the structure, the surface and / or the mechanical properties, the process procedure can advantageously be streamlined by converting at least part of the carrier material into the gas phase at a temperature that is simultaneously a Refinement of the metal component causes. The finishing can be carried out at different temperatures depending on the metal or alloy used for the metal component. Suitable refinement steps are, for example, hardening, solution annealing, tempering or sintering of the metal component. The suitable temperature can be found out by simple experiments. Through this process, the metal component is tempered or treated while the carrier material is being removed. refined, which saves time and costs for process management.

0021The method further advantageously comprises a step of applying a negative pressure to the heating device. The negative pressure removes the gaseous carrier material from the reaction equilibrium more quickly. In addition, the negative pressure applied acts as an insulator and reduces the heat loss through the condensation area, which is particularly advantageous if the condensation area is in the heating device.

0022As an alternative or in addition, the method for faster removal of gaseous carrier material can comprise a step of feeding a gas into the heating device. As a result, the gaseous carrier material is virtually expelled from the recess. In addition, the gas space is filled with additionally supplied gas, so that the removal of gaseous carrier material is promoted by increased convection.

0023The gas supplied is in particular an inert gas such as nitrogen or helium, that is to say a gas that does not react either with the carrier material or with the metal at the temperature prevailing in the heating device. The gas supplied can, however, also be a forming gas, reaction gas or a mixture of the gases mentioned above. By a suitable choice of the gas, the expulsion of the gaseous carrier material can be significantly accelerated, so that the recess is exposed within a short time.

0024According to a further advantageous development, it is provided that the condensation of the gaseous carrier material takes place on a cold finger. Cold fingers are space-saving devices that can be arranged inside or outside the heating device and represent a condensation area for the gaseous carrier material. They can be arranged inexpensively and flexibly. Their temperature and thus the rate of condensation of gaseous carrier material can also be controlled very easily.

0025According to an alternative embodiment, the gaseous carrier material is condensed in a cold trap. The cold trap is usually arranged outside the heating device. It offers the advantage that the recondensed carrier material can be collected very easily locally and the amount of solidified carrier material that forms can be easily traced. This embodiment is particularly suitable with the simultaneous application of negative pressure or with a supply of a gas to expel the gaseous carrier material.

0026The cold trap is also advantageously connected upstream of a vacuum pump, since this can ensure better separation of the gaseous carrier material.

0027To improve the removal of the carrier material, provision is further advantageously made for the cold trap to be connected downstream of a gas flow emerging from the heating device.

0028The carrier material is a metallic carrier material, since metallic carrier materials transition into the gas phase in a very controllable manner at relatively low temperatures and can be recondensed in a controlled manner. The metallic carrier material is selected from: magnesium, aluminum, zinc, antimony, mixtures or alloys thereof. These materials are available at moderate prices and are easy to process. As an alternative or in addition, the carrier material can contain a ceramic carrier material. This serves to enforce the structure, especially when used in combination with a metallic carrier material. As soon as part of the metallic carrier material has been removed, the remaining structure can very easily be completely removed by mechanical action, for example by blowing out or rinsing out, exposing the recess.

0029Further details, advantages and features of the present invention emerge from the following description of exemplary embodiments with reference to the drawing. It shows:<ul id="ul0003" list-style="none"><li><figref idref="f0001">Fig. 1</figref> a scheme illustrating process steps for producing a metal component with a recess according to an embodiment,</li><li><figref idref="f0001">Fig. 2</figref> a schematic view of a device for performing the method according to a first embodiment and</li><li><figref idref="f0002">Fig. 3</figref> a schematic view of a device for performing the method according to a second embodiment.</li></ul>

0030Only the essential features of the invention are shown in the figures. All other features are omitted for the sake of clarity. Furthermore, the same reference symbols denote the same parts or components.

0031Shows in detail <figref idref="f0001">Figure 1</figref> schematizes process steps of a process for producing a metal component with at least one recess. The metal component can advantageously be designed as a steel component.

0032In a first method step 100, the metal component is introduced into a heating device. The metal component comprises at least one recess which is at least partially filled with a carrier material. The recess can be, for example, a recess, a cavity, a cavity, an undercut or the like, which in the finished metal component is used, for example, as a medium-carrying channel.

0033The heating device is designed in particular as a furnace and is used to bring the metal component together with the carrier material to a specified temperature.

0034Following the introduction of the metal component into the heating device, at least part of the carrier material is removed 200, exposing at least one area of ​​the recess.

0035For this purpose, at least part of the carrier material is converted into the gas phase, for example by sublimation or by passing through a liquid phase. By converting carrier material into the gas phase, carrier material is removed from the recess. It is distributed in the surrounding space by diffusion.

0036The carrier material present in gaseous form is condensed in a condensation area. The condensation region can be present inside the heating device or outside the heating device and has a temperature which corresponds to or is below the solidus temperature of the carrier material. Thus, the carrier material recondenses in this relatively cool condensation area and is thereby removed from the reaction equilibrium between solid carrier material in the temperature-controlled area of ​​the heating device and gaseous carrier material also in the temperature-controlled area of ​​the heating device. The above-mentioned equilibrium is thus shifted and further solid carrier material is transferred from the recess into the gas phase, which recondenses outside the metal component, for example in a cold trap or on a cold finger. The respective temperatures for converting the carrier material into the gas phase and also for condensing it can easily be found out through experimental tests, or they can be taken from corresponding tables.

0037The method explained above produces a metal component with a recess in a simple and very efficient manner without the need to add chemicals that dissolve the carrier material. To accelerate the conversion of the carrier material into the gas phase, however, it can be advantageous to apply a negative pressure to the heating device or to pass a gas through the heating device, by means of which the gaseous carrier material is removed from the metal component particularly quickly.

0038<figref idref="f0001">Figure 2</figref> shows a device 1 for executing a method for producing a metal component with at least one recess. The procedure can be as in<figref idref="f0001">Figure 1</figref> set out in the device 1 are executed.

0039The device comprises a furnace 2 into which a metal component 10 is introduced. The metal component 10 has a carrier material 11 which at least partially fills a recess. After the process has ended, the recess in the metal component is exposed and can serve, for example, as a channel carrying a medium, for example for transporting a coolant, a reaction product or reaction educts.

0040A cooling line 3 is connected to the furnace 2 and connects the furnace 2 to a cold finger 5 via a valve 4. The cold finger 5 corresponds to a condensation area for the condensation of the gaseous carrier material.

0041In addition, a vacuum line 6 is connected to the furnace and connects the furnace 2 to a vacuum connection 8, for example a vacuum pump, via a valve 7.

0042The furnace 2 is kept at a temperature at which the carrier material 11 changes into the gas phase. A reaction equilibrium is established in the interior of the furnace 2 between the solid support material 11 in the recess and the gaseous support material. By opening the valve 4, the furnace 2 is connected to the cold finger 5. Thus, gaseous carrier material flows to the cold finger 5. The cold finger 5 is kept at a temperature which corresponds to the solidus temperature of the carrier material 11 or is below it. As a result, the gaseous carrier material is condensed on the cold finger 5. Thus, gaseous carrier material is withdrawn from the above reaction equilibrium and is consequently reproduced from the solid carrier material 11 located in the recess. Solid carrier material 11 is thus gradually removed from the recess in metal component 10 via the gas phase and recondensed on cold finger 5. The recess is depleted of carrier material 11 and is thus at least partially exposed.

0043The removal of gaseous carrier material can be accelerated by opening the valve 7, since this allows a negative pressure, and in particular a vacuum, to be applied to the furnace 2.

0044The device is very well suited to producing a metal component with at least one recess. Any remaining stocks of solid carrier material 11 can be completely removed from the recess, for example by using compressed air or a water jet.

0045<figref idref="f0002">Figure 3</figref> shows a further device 1 for producing a metal component with at least one recess according to a further embodiment.

0046As a difference to the device 1 from <figref idref="f0001">Figure 2</figref> it can be seen that the cooling line 3 comprises a cold trap 9 in which the gaseous carrier material is condensed. In this embodiment, the cold trap 9 corresponds to the condensation area for the condensation of the gaseous carrier material. The expulsion of the gaseous carrier material is facilitated by the fact that, after opening the valve 13, a gas, for example an inert gas, a forming gas, a reaction gas or the like, is passed through the furnace 2 through the gas line 12. The gas space in the furnace 2 is thus diluted with the supplied gas and, due to the accelerated removal of the gaseous carrier material from the furnace 2 and condensation of the same in the cold trap 9, gaseous carrier material is reproduced more quickly from the solid carrier material 11 present in the recess of the metal component 10.

0047The in <figref idref="f0002">Figure 3</figref> The device 1 shown is suitable for this <figref idref="f0001">Figure 1</figref> execute illustrated methods and produce a metal component with a recess within a short time without high technical effort.

0048In addition to the above written description of the invention, for the supplementary disclosure thereof, reference is hereby made explicitly to the graphic representation of the invention in FIGS <figref idref="f0001 f0002">Figs. 1 to 3</figref> Referenced.

List of reference symbols

0049<dl id="dl0001" compact="compact"><dt>1</dt><dd>contraption</dd><dt>2</dt><dd>oven</dd><dt>3</dt><dd>Cooling pipe</dd><dt>4</dt><dd>Valve</dd><dt>5</dt><dd>Cold finger</dd><dt>6</dt><dd>Vacuum line</dd><dt>7</dt><dd>Valve</dd><dt>8</dt><dd>Vacuum connection</dd><dt>9</dt><dd>Cold trap</dd><dt>10</dt><dd>Metal component</dd><dt>11</dt><dd>Carrier material</dd><dt>12</dt><dd>Gas pipe</dd><dt>13</dt><dd>Valve</dd><dt>100-200</dt><dd>Procedural steps</dd></dl>