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US20110129380A1 - Method and device for producing a workpiece, particularly a shaping tool or a part of a shaping tool - Google Patents

Method and device for producing a workpiece, particularly a shaping tool or a part of a shaping tool Download PDF

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Publication number
US20110129380A1
US20110129380A1 US12/994,345 US99434509A US2011129380A1 US 20110129380 A1 US20110129380 A1 US 20110129380A1 US 99434509 A US99434509 A US 99434509A US 2011129380 A1 US2011129380 A1 US 2011129380A1
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United States
Prior art keywords
metal
mold
heat
containing material
resistant mold
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
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US12/994,345
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English (en)
Inventor
Isaac Valls Angles
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Rovalma SA
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Rovalma SA
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Publication of US20110129380A1 publication Critical patent/US20110129380A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
    • B22F5/007—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of moulds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
    • B22D27/13—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure making use of gas pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/15—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using vacuum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D31/00—Cutting-off surplus material, e.g. gates; Cleaning and working on castings
    • B22D31/002—Cleaning, working on castings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the present invention relates to a method for producing a workpiece, particularly a shaping tool or a part of a shaping tool. Furthermore, the present invention relates to a device for producing a workpiece, particularly a shaping tool or a part of a shaping tool.
  • an alloy having the desired composition is first of all melted.
  • the melt is then cast into a casting mold, the shape of which is already close to the desired final shape of the shaping tool or part of a shaping tool.
  • the alloy melt in the casting mold has solidified, it is first of all roughly machined, then heat-treated and subsequently finely finished.
  • the liquid melt is first of all cast to form a bar.
  • said bar is extracted, then heated up again and subsequently—customarily in a plurality of steps—forged to form rods or blocks.
  • the rods or blocks obtained in this manner are then heated up again in order to initiate a curing process which simplifies the subsequent finishing operation.
  • the rods When the rods have cured, they are customarily cut into blocks having the desired dimensions. Said blocks are then brought in a rough machining step into a shape which is already close to the final shape of the shaping tool or of the part of a shaping tool.
  • shaping tools or parts of shaping tools are produced from forged blocks at all.
  • casting methods for producing shaping tools or parts of shaping tools appear to be more expedient at first sight, since said casting methods are considerably more cost-effective than the machining of forged blocks.
  • the mechanical properties of the shaping tools or parts of shaping tools obtained by the two above-described methods differ greatly. It is the resulting toughness/ductility of the shaping tools or parts of shaping tools which makes the considerably more complex in terms of method and therefore substantially more expensive machining of forged blocks advantageous.
  • the steel containers are then evacuated in order to obtain a certain amount of vacuum and inserted into a hot isostatic pressing device in which high temperatures and pressures are generated in order to deform the steel containers and to compact the metal powder such that a bar is obtained.
  • a bar remains, which bar can be forged and can be subjected to all the machining steps which have been explained in more detail above in the description of the method “machining of forged blocks”.
  • this production method increases the production costs, the toughness/ductility which can be achieved is much higher than blocks which have been melted and forged in a conventional manner. This can be achieved in particular if the alloy has a relatively high content of a brittle ceramic phase.
  • the forging increases the toughness/ductility of the shaping tool or part of a shaping tool
  • a number of undesirable properties, of which the most important is anisotropy are induced. This is because the forging creates a material structure which leads to different properties in the forging direction in comparison to the directions running transversely with respect to the forging direction.
  • Said anisotropy can be disadvantageous in particular during the heat treatment of the shaping tool or part of a shaping tool, since said anisotropy results in a distortion of the workpiece, and therefore more material has to be left over for the final machining operation.
  • a further method for producing a shaping tool or a part of a shaping tool is the sintering of a metal powder.
  • a metal powder or, alternatively, a mixture of a plurality of metal powders is pressed in order to obtain a body having the desired geometrical shape and having a suitable structure such that it can subsequently be further machined.
  • a body of this type is frequently also referred to as a “green body”.
  • the green body is then sintered at a high temperature for a sufficiently long period of time in order to promote diffusion bonding. If a high density is desired, a final, hot-isostatic pressing step is carried out.
  • DE 195 089 59 C2 discloses a molded body made of a ceramic, powder-metallurgical or composite material. Furthermore, a method for producing a molded body of this type is disclosed in the abovementioned reference. The material composition and/or the structure are/is changed within the molded body in one, two or all three directions in space. The changes may be continuous or discontinuous.
  • one or more starting powders are processed to form one or more moldable compounds. Said moldable compound/compounds is/are processed continuously or discontinuously in one, two or all three directions in space to form a molded body and is/are subsequently cured, wherein the moldable compound or compounds is or are applied in relation to the graduation of properties to be obtained at the end.
  • the international patent application WO 2006/056621 A2 describes a method for producing a shaping tool by superplastic deformation or by hot compaction of a metallic powder in a cement mold.
  • the shaping tool properties obtained by the hot compaction of the powder are not particularly good with particular regard to the strength and toughness/ductility. The reason for this resides in particular in the surface oxidation of the metallic powder, the surface oxidation preventing the optimum compaction of said powder.
  • the present invention is based on the object of providing a method for producing a workpiece, particularly a shaping tool or a part of a shaping tool, which method permits production of a workpiece in a manner close to the final shape, the workpiece having an advantageous combination of high strength and at the same time favorable toughness and ductility properties. Furthermore, the present invention is based on the object of providing a device for producing a corresponding workpiece, particularly a shaping tool or a part of a shaping tool.
  • a method according to the invention for producing a workpiece comprises the following steps:
  • the workpieces such as, for example, shaping tools or parts of shaping tools
  • the workpieces are produced in a heat-resistant mold under vacuum conditions by compaction of the heated, metal-containing material which may be present, for example, as a solid, metal-containing body.
  • the workpiece is produced in an evacuable chamber in which the vacuum can be generated and in which, if appropriate, an inert gas atmosphere and/or a reduction gas atmosphere can also be generated.
  • the method according to the invention permits the production in a particularly advantageous manner of locally isotropic workpieces (for example, shaping tools or parts of shaping tools) which are close to the final shape, as can be obtained by the casting methods known from the prior art, with mechanical properties, as can be obtained by the known powder metallurgy methods.
  • the oxygen content in the residual gas within the evacuable chamber can be reduced such that oxygen contamination of the surface of the metal-containing material is substantially prevented, but can be at least considerably reduced, and therefore workpieces, such as, for example, shaping tools or parts of shaping tools, of particularly high quality can be produced.
  • a number of flushings of the evacuable chamber with a reduction gas and/or an inert gas is carried out before the vacuum is generated in the evacuable chamber.
  • a vacuum can advantageously be generated in the evacuable chamber (at least temporarily) between two flushings with the inert gas or reduction gas. The vacuum does not need to be a high vacuum. The residual gas level within the evacuable chamber is relatively low because of the vacuum generation following the flushings.
  • a high vacuum is generated in the evacuable chamber and the hot pressing of the heated metal-containing material is carried out under high vacuum conditions.
  • the pressure range of the high vacuum which is generated within the evacuable chamber advantageously lies within an order of magnitude of between approximately 10 ⁇ 3 and approximately 10 ⁇ 7 mbar.
  • the production of a high vacuum enables in particular the oxygen content in the residual gas within the vacuum chamber to be further reduced such that oxygen contamination of the surface of the metal-containing material can be further reduced.
  • an alternative method according to the invention for producing a workpiece, shaping tool or a part of a shaping tool comprises the following steps:
  • the compaction of the heated, metal-containing material in the heat-resistant mold by means of hot pressing is therefore not carried out under vacuum conditions but rather in an inert gas atmosphere or reduction gas atmosphere.
  • oxygen contamination of the metal-containing material can likewise be effectively prevented.
  • This method according to the invention likewise permits in a particularly advantageous manner the production of locally isotropic shaping tools or parts of shaping tools close to the final shape, as can be obtained by the casting method, with strength properties, as can be obtained by a powder metallurgy method.
  • a workpiece (shaping tool or part of a shaping tool) produced by the methods presented here preferably has an impact value of more than 50 J/cm 2 while the degree of hardness is preferably greater than 58 HRC.
  • the hot pressing is carried out at a constant rate of expansion.
  • the rate of expansion can be kept constant, for example, via a change in the advancing speed of a metal cylinder, by means of which a pressure is exerted on the mold and therefore on the metal-containing material.
  • the metal-containing material is placed in the form of at least one layer of a metal-containing powder or of a metal-containing powder mixture into the heat-resistant mold.
  • the method then in particular comprises the step of hot pressing the metal-containing powder or the metal-containing powder mixture in the heat-resistant mold to which preferably only a small amount of water is admixed.
  • the metal-containing powder used for producing the workpiece can consist entirely of one material.
  • the metal-containing powder may also be, for example, a mixture of a metal powder with ceramic particles, wherein the ceramic particles, for their part, may have a coating.
  • the possibility of using mixtures of different metal-containing powders or a plurality of layers or regions of different metal-containing powders and of inputting said powders or layers into the heat-resistant mold may be particularly advantageous. It is therefore proposed, in a particularly advantageous embodiment, that, when the metal-containing powder or the metal-containing powder mixture is placed in, at least two layers or regions having a different chemical composition are produced.
  • workpieces in particular shaping tools or parts of shaping tools
  • tailored mechanical and/or physical properties which may also be graduated within the volume of said workpieces. In other words, this therefore also enables the production of workpieces which have different mechanical and/or physical properties in one, two or else all three directions in space within the volume thereof.
  • the graduations of properties may be continuous or else discontinuous.
  • Some coated particles necessitate the control of certain diffusion parameters (in particular temperature and time) during the process in order to avoid a deterioration in the intrinsic properties or to obtain optimum properties, wherein the processes presented here are particularly suitable therefor.
  • certain diffusion parameters in particular temperature and time
  • the heated, metal-containing material is compacted in a superplastic state of the material.
  • the metal-containing material is preferably heated up comparatively slowly in the heat-resistant mold in order to achieve the superplastic state.
  • the superplastic state of a metal-containing material is customarily achieved (depending on the material and depending on the rate of expansion) at a temperature of approximately 800° C. to approximately 1050° C.
  • the compaction of the heated, metal-containing material in the superplastic state is advantageous in particular if the material is present in the form of a body, the geometry of which is preshaped. This is the case, for example, for a precompacted, dimensionally stable green compact. If the metal-containing material is present in powder form, the hot pressing can also be carried out in a non-superplastic state although the compaction in the superplastic state is also particularly advantageous here.
  • a particularly preferred variant of the method provides that the metal-containing material is heated up further after reaching the superplastic state to the diffusion acceleration temperature thereof.
  • Said diffusion acceleration temperature is dependent on the alloy and, for example in the case of tool steel, is of an order of magnitude of approximately 1150° C.
  • alloys made of molybdenum have a higher diffusion acceleration temperature of above 1800° C.
  • alloys made of copper have a diffusion acceleration temperature which is lower than 900° C.
  • the diffusion acceleration temperature is preferably maintained for a relatively long period of time, customarily for a period of time of more than 30 minutes. The maintaining time depends in particular on the diffusion acceleration temperature and the pressure exerted. This may be, if appropriate, a number of hours or even a number of days.
  • the metal-containing material is at least partially melted and is compacted in an at least partially liquid state.
  • the metal-containing material does not need to be completely melted. There is the possibility, for example, of only one phase of the metal-containing material being melted before the compaction. This embodiment of the method may be advantageous for a number of application purposes.
  • the pressure which is exerted on the heated, metal-containing material during the hot pressing operation is preferably greater than 20 MPa.
  • the pressure during the compaction of the metal-containing material may be in particular between approximately 20 MPa and approximately 250 MPa—depending on the load-bearing capacity of the mold material.
  • a cold pressing step can be carried out before the metal-containing material is heated up.
  • the cold pressing step enables the porosity of the metal-containing powder or of the metal-containing powder mixture to be closed so as to leave as little interconnected porosity as possible in the material.
  • the evacuable chamber can be flushed, if appropriate, with a reduction atmosphere before continuing with the other method steps.
  • the metal-containing powder or the metal-containing powder mixture can also be input into a controlled atmosphere environment. Irrespective of which process is pursued, it is important to avoid as far as possible the presence of oxygen between powder grains.
  • the process heat is removed in a targeted manner, preferably by means of a cooling device, after the compaction of the metal-containing material.
  • a targeted removal of heat can involve accelerating the production method as a whole.
  • the microstructural properties of the workpiece can be set by the targeted removal of heat.
  • the pressure exerted on the metal-containing material is maintained during the targeted removal of the process heat (cooling phase).
  • the step of compacting the metal-containing material or of removing the process heat is followed by at least one finishing step.
  • This at least one finishing step may in particular comprise the carrying out of a fine machining process and/or hard machining process.
  • grinding processes, high speed milling processes or thermally assisted laser machining processes may be used.
  • the at least one finishing step is not carried out under vacuum conditions or under a gas atmosphere.
  • the methods presented here for producing a workpiece permit tailoring of functionalities which can be derived directly from the metallurgical and microstructural composition of the metal-containing material used (in particular tool steel).
  • a device according to the invention for producing a workpiece particularly a shaping tool or a part of a shaping tool, comprises:
  • the device according to the invention is suitable in particular for carrying out a method as claimed in one of claims 1 to 9 such that workpieces, such as, for example, shaping tools or parts of shaping tools, can be produced with the above-described advantageous properties.
  • the heat-resistant mold which is used for producing the workpiece is intended to be suitable, with respect to the mechanical configuration thereof, to withstand the pressure which is required in order to allow a metal-containing powder or a metal-containing powder mixture to flow.
  • the pressure acting on the metal-containing material during the compaction operation can be between approximately 20 MPa and approximately 250 MPa—depending on the load-bearing capacity of the mold material.
  • the device furthermore has means for generating an inert gas atmosphere and/or a reduction gas atmosphere.
  • the compaction of the metal-containing material can be carried out in an inert gas atmosphere or a reduction gas atmosphere.
  • oxygen contamination of the surface of the metal-containing material can be prevented.
  • the heat-resistant mold can be a ceramic-containing and/or graphite-containing mold.
  • the pressures acting on the mold material from which the heat-resistant mold is produced are generally greater than 20 MPa, frequently also greater than 30 MPa to 40 MPa such that concrete, mortar or cement with a small admixture of water and with a content of at least one ceramic material are particularly advantageous as materials for producing the heat-resistant mold.
  • Al 2 O 3 , zirconium oxide, silicon carbide or Si 0 2 are the preferred additional materials for producing the heat-resistant mold.
  • the concrete, cement or mortar can preferably have a content of at least 40%, preferably of at least 60%, in particular of at least 80% Al 2 O 3 . It can also be provided, for example, that the concrete, cement or mortar has a strength which is greater than 150 MPa (preferably greater than 200 MPa).
  • the means for heating the metal-containing material can comprise at least one heating element which can be embedded, for example, into the heat-resistant mold.
  • the at least one heating element preferably extends in the circumferential direction of at least one of the mold parts (preferably at a distance of approximately 10 to 20 mm from the mold cavity) such that uniform heating-up of the metal-containing material can be achieved.
  • the at least one heating element can consist, for example, of an Ni—Cr resistance wire or of an Fe—Cr—Al resistance wire. Other resistance heating wires which can consist, for example, of molybdenum or tungsten can likewise be used. An inductively operating heating element can also be used.
  • At least one cooling device can be provided, which cooling device can advantageously likewise be embedded into the heat-resistant mold and is suitable for cooling the metal-containing material within the heat-resistant mold in a targeted manner.
  • a cooling option for the metal-containing material placed into the heat-resistant mold can additionally be provided.
  • the cooling device can comprise, for example, a number of cavities which are introduced in a defined manner into the heat-resistant mold during production. A liquid or gaseous cooling fluid can flow through said cavities and can be conveyed by means of a supply device or the like in order to be able to cool the metal-containing material in the heat-resistant mold in a targeted manner after the compaction operation.
  • the cooling device may comprise, for example, at least one tube which is embedded into the heat-resistant mold and through which a liquid or gaseous cooling fluid can circulate.
  • the evacuable chamber may also be flooded with a gaseous cooling fluid (for example, with nitrogen or argon).
  • the gaseous cooling fluid can preferably flow out of a pressure tank or a pressurized gas cylinder into the cavities, the tube or the evacuable chamber, since the gas cools further upon expansion.
  • the cooling device forming a cooling circuit, within which the cooling fluid can circulate and within which, for example, a heat exchanger or a compression stage can be provided.
  • At least one temperature detection means and regulating means can be provided in order to regulate the temperature of the metal-containing material in the mold.
  • a model having the desired geometry of the workpiece for example a shaping tool or part of a shaping tool
  • Said mold model can be produced from different materials (for example, from polystyrene, polypropylene, wood or aluminum). Numerous other thermoplastics, metals or even ceramic materials can be used to produce the mold model.
  • use may be made of conventional method techniques or else of “rapid-prototyping techniques” (for example, mechanical machining, stereo-lithography, three-dimensional wax impression, casting etc.).
  • the mold can be produced, for example by casting of the heat-resistant mold material, in particular if the mold material contains a powder or powder mixture, concrete, mortar or the like. If the mold is produced in this manner, it is very simple to embed at least one heating element (in particular a resistance heating element or an induction heating element), a cooling element and, if appropriate, also temperature detection means into the mold. If the mold is produced by a three-dimensional ceramic printing technique or by a comparable technique which permits the heat-resistant mold to be obtained directly—i.e. without further intermediate steps, a corresponding mold model does not have to be produced. The same applies if the heat-resistant mold is obtained by direct mechanical machining of a solid block of a heat-resistant mold material.
  • the concrete is placed into the mold model together with a small admixture of water and preferably an admixture of a ceramic material.
  • the mold model should be filled as rapidly as possible.
  • the mold is subsequently cured at a high temperature (for example, approximately 1200° C.) such that the residual moisture can escape from the concrete.
  • a high temperature for example, approximately 1200° C.
  • vibrating the mold model as the mold material is being placed therein, for example on a vibrating table or the like. It has been shown that the porosity of the mold can be substantially reduced as a result.
  • the mold cavity can be at least partially filled with the metallic material, in particular with a metal-containing powder or with a metal-containing powder mixture. This is then followed by the remaining process steps to produce the workpiece.
  • the surface of the mold cavity of the heat-resistant mold have a ceramic layer and/or a releasing-agent and lubricating layer.
  • the ceramic layer may be, for example, an oxide layer (for example consisting of zirconium oxide) or a carbide layer (for example consisting of silicon carbide). Any other ceramic material which does not react with hot metal can likewise be used.
  • the releasing-agent and lubricating layer can consist, for example, of graphite, molybdenum disulfide, sulfur, phosphorus, boron nitride, mica or of another material which can withstand the relatively high process temperatures.
  • the mold material used is likewise highly desirable for the mold material used to have relatively low heat conductivity so that said mold material can serve as an insulator between the heating-up zone, in which the metal-containing powder or the metal-containing powder mixture is heated, and the exterior of the mold, in particular if, in an advantageous embodiment, the heat-resistant mold has a prestressed reinforcing ring made of metal.
  • a prestressed reinforcing ring of this type can produce pressure stresses in the mold in order to compensate for tensile stresses which arise during the compaction of the heated, metal-containing material.
  • At least sections of the surface of the mold cavity can have a dye layer or a dispersion layer.
  • the surface of the mold cavity can be rendered chemically more inert by the application of a dye or dispersion. Lubricants may also be used for this purpose. It may also be advantageous to increase the emissive power of the surface of the ceramic mold in order to configure the process to be more efficient in terms of energy and to keep the heat at the location where it is required.
  • the active material of the dye or of the dispersion may be, for example, zirconium oxide, boron nitride or molybdenum disulfide or may comprise other components on the basis of graphite, phosphorus or sulfide (to mention just some components).
  • the heat-resistant mold is reinforced with metal particles and/or metal rods and/or metal wires and/or metal wire fabrics.
  • Iron or steel can be used as the material.
  • heat-resistant metals such as, for example, tungsten or molybdenum and the alloys thereof and also alloys on the basis of nickel or cobalt may be more advantageous.
  • textile fibers and/or polymer fibers and/or ceramic fibers and/or glass fibers and/or long fiber fabrics of said materials may also be used.
  • the means for compacting the metal-containing material may in particular comprise a metal cylinder which is operatively connected to the second mold part of the heat-resistant mold.
  • the metal cylinder can exert a sufficiently high pressure on the heat-resistant mold or on part of the heat-resistant mold in order thereby to compact the metal-containing material in the mold.
  • a device which is suitable for carrying out a method for producing a workpiece, particularly a shaping tool or a part of a shaping tool comprises an evacuable chamber 1 with a vacuum system, by means of which a vacuum, preferably a high vacuum of an order of magnitude of between 10 ⁇ 3 and 10 ⁇ 7 mbar, can be generated in the interior of the evacuable chamber.
  • the vacuum system may comprise, for example, a vane-type rotary pump and a turbomolecular pump connected thereto.
  • the vane-type rotary pump generates a fore-vacuum for the turbomolecular pump.
  • pressure sensor means are provided so that the pressure within the evacuable chamber 1 can be measured and continuously monitored.
  • the device furthermore has a heat-resistant mold 2 which may be, for example, ceramic-containing and/or graphite-containing and comprises a first (lower) mold part 2 a with a mold cavity, and a second (upper) mold part 2 b guided movably relative to the first mold part 2 a . It is seen that the inside diameter of the first mold part 2 a is greater than the outside diameter of the second mold part 2 b , and therefore the second mold part 2 b can be inserted into the mold cavity of the first mold part 2 a .
  • the two heat-resistant mold parts 2 a , 2 b are preferably produced from concrete and a ceramic material (for example, Al 2 O 3 ) and have only a small admixture of water.
  • a heating element 3 is embedded into the first mold part 2 a so that the first mold part 2 a can be heated up as the method is being carried out.
  • the distance of the heating element 3 from the inner surface of the mold cavity of the first mold part 2 a is preferably approximately 10 to 20 mm.
  • the heating element 3 is required in order to achieve the temperature necessary for producing the workpiece. It is advantageous in this case if, as in the exemplary embodiment shown here, the heating element 3 is embedded directly into the heat-resistant mold 2 .
  • the heating element 3 may be, for example, a resistance heating element or an induction heating element, the last-mentioned variant being more advantageous because of having shorter heating-up times and better insulation, even though it is somewhat more difficult to calibrate.
  • a cooling device (not shown explicitly in FIG. 1 ) may be provided, by means of which the metal-containing workpiece in the mold 2 can also be cooled.
  • FIG. 1 shows, by way of example, one possible position of the heating element 3 within the first mold part 2 a of the heat-resistant mold 2 .
  • the first mold part 2 a may also be constructed in a modular manner and may have, for example, an inner contact layer adjoined by the heating element 3 and finally an insulation shield.
  • a temperature detection means 4 which may in particular comprise a conventional thermocouple, is embedded into the first mold part 2 a .
  • the process temperature can be continuously monitored as the method is being carried out.
  • the process temperature can be very exactly regulated as the method is being carried out.
  • the device has a metal cylinder 5 by means of which a pressure can be exerted in the arrow direction on the second (upper) mold part 2 b .
  • the surface of the mold cavity of the heat-resistant mold 2 can advantageously be coated with a ceramic layer and/or with a releasing-agent and lubricating layer.
  • the ceramic layer may be, for example, an oxide layer (for example consisting of zirconium oxide) or a carbide layer (for example consisting of silicon carbide). Any other ceramic material which does not react with the hot metal within the mold cavity can likewise be used.
  • the releasing-agent and lubricating layer may consist, for example, of graphite, molybdenum disulfide, sulfur, phosphorus, boron nitride, mica or of another material which can withstand the high process temperatures. Furthermore, there is the option of using a glass powder as the releasing agent. Glass has the advantage that, at high temperatures, it forms a glass separating layer which can effectively prevent disadvantageous surface reactions with the surrounding atmosphere.
  • a metal-containing material in the form of a metal-containing, solid body or at least one layer or one region of a metal-containing powder or of a metal-containing powder mixture from which the workpiece is intended to be produced is placed into the mold cavity of the first mold part 2 a and heated therein, according to a first exemplary embodiment, under high vacuum conditions with the aid of the at least one heating element 3 .
  • the generation of a high vacuum in the interior of the evacuable chamber 1 during the compaction operation is particularly advantageous.
  • One option for obtaining better process conditions consists in curing the heat-resistant mold 2 in a reduction gas atmosphere in order thereby to ensure that voids within the mold material are filled with the reduction gas atmosphere.
  • the heat-resistant mold 2 can be heated up in the evacuable chamber 1 prior to the metal-containing material being placed therein, and then a vacuum can be generated and the chamber 1 can subsequently be filled with a reduction atmosphere in order to fill the voids within the mold material.
  • a vacuum can advantageously be generated, at least temporarily, in the evacuable chamber 1 between two flushings.
  • a vacuum is generated in the evacuable chamber 1 and maintained for a certain period of time t vacuum .
  • an inert gas atmosphere or reduction gas atmosphere is generated in the evacuable chamber 1 and the metal-containing material is heated.
  • the heated, metal-containing material in the heat-resistant mold 2 is then compacted by hot pressing in the inert gas atmosphere or reduction gas atmosphere.
  • the metal-containing material is heated up after being placed into the mold cavity of the first mold part 2 a of the heat-resistant mold 2 and, in the process, is optionally transferred into a superplastic state which is achieved (depending on the material) at temperatures of between approximately 800° C. and approximately 1050° C.
  • the hot pressing preferably takes place in said superplastic state.
  • the hot pressing advantageously takes place at a constant rate of expansion and a constant advancing speed of the metal cylinder 5 .
  • the pressure which is generated during the hot pressing by the metal cylinder 5 and acts via the second mold part 2 b on the metal-containing material within the first mold part 2 a can be between approximately 20 MPa and approximately 250 MPa.
  • the pressure here can act on the metal-containing material within the heat-resistant mold 2 continuously or only in phases.
  • the hot pressing can also take place under non-superplastic conditions. However, it is particularly advantageous to compact the metal-containing powder or the metal-containing powder mixture by hot pressing in the superplastic state.
  • the metal-containing powder or the metal-containing powder mixture can subsequently be heated for a certain period of time (for example, approximately two hours) to the diffusion acceleration temperature thereof.
  • the greatest possible material density can be produced in the workpiece by said measure.
  • the diffusion acceleration temperature is dependent on the alloy and, for example, in tool steel is of an order of magnitude of approximately 1150° C. In contrast thereto, alloys consisting of molybdenum have a higher diffusion acceleration temperature of above 1800° C.
  • the diffusion acceleration temperature is preferably maintained for a relatively long period of time, customarily for a period of time of more than 30 minutes.
  • the maintaining time which, if appropriate, may also be a number of days depends in particular on the diffusion acceleration temperature and the pressure exerted.
  • the metal-containing material is at least partially melted and is compacted in an at least partially liquid state. The metal-containing material does not need to be completely melted. There is, for example, the option of melting only one phase of the metal-containing material before the compaction operation. This embodiment of the method may be advantageous for a number of application purposes.
  • At least two layers or regions having different metal-containing powders or metal-containing powder mixtures to be placed into the heat-resistant mold 2 .
  • a build-up of layers with at least two layers permits the production in a particularly advantageous manner of a workpiece (for example a shaping tool or part of a shaping tool) with graduated tool properties with the aid of the method presented here. It is thus possible, for example, to produce shaping tools or parts of shaping tools having different mechanical and/or physical properties within the volume thereof.
  • a graduation of properties in the volume can be produced (continuously or discontinuously) in one, two or all three directions in space.
  • a comparatively hard and wear-resistant tool surface is frequently desired whereas a tool base body which is softer by comparison is sufficient or may even be particularly advantageous.
  • a material composition which is layered or differs in regions is likewise advantageous.
  • the optimum tool properties which are normally associated with high costs can thus be provided only where they are actually required.
  • the remaining part of a shaping tool or part of a shaping tool can be constructed from a material having sufficient properties and substantially lower material costs. It can furthermore be provided that the process heat is removed in a targeted manner with the aid of the optionally provided cooling device after the compaction of the metal-containing material.
  • One purpose of such a targeted removal of heat can consist in the overall acceleration of the production method.
  • the microstructural properties of the workpiece can be set.
  • the cooling device may comprise, for example, a number of cavities which are introduced in a defined manner into the heat-resistant mold 2 .
  • a liquid or gaseous cooling fluid can flow through the cavities and can be conveyed by means of a supply device in order to be able to cool the metal-containing material in the heat-resistant mold 2 in a targeted manner.
  • the cooling device may also comprise, for example, at least one tube which is embedded into the heat-resistant mold 2 and through which a liquid or gaseous cooling fluid can circulate.
  • the evacuable chamber 1 can furthermore also be flooded with the cooling fluid (for example, with nitrogen or argon).
  • the gaseous cooling fluid can preferably flow out of a pressure tank or a compressed gas cylinder into the cavities, the tube or the evacuable chamber 1 since the gas is additionally cooled further upon expansion.
  • the cooling device may form a cooling circuit within which the cooling fluid can circulate and within which, for example, a heat exchanger or a compression stage can be provided.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Powder Metallurgy (AREA)
  • Mounting, Exchange, And Manufacturing Of Dies (AREA)
US12/994,345 2008-05-23 2009-05-23 Method and device for producing a workpiece, particularly a shaping tool or a part of a shaping tool Abandoned US20110129380A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP08382020A EP2123377A1 (de) 2008-05-23 2008-05-23 Verfahren zur Herstellung eines Werkstücks, insbesondere eines Formgebungswerkzeugs oder eines Formgebungswerkzeugteils.
EP08382020.9 2008-05-23
PCT/EP2009/003628 WO2009141152A1 (de) 2008-05-23 2009-05-22 Verfahren und vorrichtung zur herstellung eines werkstücks, insbesondere eines formgebungswerkzeugs oder eines formgebungswerkzeugteils

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EP (1) EP2123377A1 (de)
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US20130316149A1 (en) * 2010-11-29 2013-11-28 William Brian Atkins Forming objects by infiltrating a printed matrix
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US20160279708A1 (en) * 2015-03-26 2016-09-29 Honeywell International Inc. Net-shape or near-net shape powder metal components and methods for producing the same
CN108168973A (zh) * 2017-12-27 2018-06-15 中国地质大学（武汉） 一种内部含非贯通结构面相似材料模型的制作方法及装置
WO2019101684A1 (de) * 2017-11-27 2019-05-31 Rampf Holding Gmbh & Co. Kg Formgebungsvorrichtung, formgebungswerkzeug mit einem umzuformenden teil und verfahren zum erwärmen einer formgebungsoberfläche einer formgebungshalbschale oder eines umzuformenden teils
US10399258B2 (en) 2010-11-29 2019-09-03 Halliburton Energy Services, Inc. Heat flow control for molding downhole equipment
FR3092775A1 (fr) * 2019-02-20 2020-08-21 Psa Automobiles Sa Procede de retrait d'une masselotte d'une piece moulee par refroidissement local
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US20160279708A1 (en) * 2015-03-26 2016-09-29 Honeywell International Inc. Net-shape or near-net shape powder metal components and methods for producing the same
WO2019101684A1 (de) * 2017-11-27 2019-05-31 Rampf Holding Gmbh & Co. Kg Formgebungsvorrichtung, formgebungswerkzeug mit einem umzuformenden teil und verfahren zum erwärmen einer formgebungsoberfläche einer formgebungshalbschale oder eines umzuformenden teils
CN108168973A (zh) * 2017-12-27 2018-06-15 中国地质大学（武汉） 一种内部含非贯通结构面相似材料模型的制作方法及装置
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WO2009141152A1 (de) 2009-11-26
JP2011523592A (ja) 2011-08-18

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