EP1563931B1 - Process for joining inorganic part produced by injection moulding with inorganic parts produced by another process - Google Patents

Process for joining inorganic part produced by injection moulding with inorganic parts produced by another process Download PDF

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Publication number
EP1563931B1
EP1563931B1 EP05002766A EP05002766A EP1563931B1 EP 1563931 B1 EP1563931 B1 EP 1563931B1 EP 05002766 A EP05002766 A EP 05002766A EP 05002766 A EP05002766 A EP 05002766A EP 1563931 B1 EP1563931 B1 EP 1563931B1
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Prior art keywords
inorganic
injection molding
molding
powder
parts
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EP05002766A
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German (de)
French (fr)
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EP1563931A1 (en
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Hans Dr. Wohlfromm
Arnd D.I. Thom
Johan D.I. Ter Maat
Martin Blömacher
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BASF SE
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BASF SE
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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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
    • B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
    • 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
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/1017—Multiple heating or additional steps
    • 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
    • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
    • B22F7/06—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools
    • B22F7/062—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of composite workpieces or articles from parts, e.g. to form tipped tools involving the connection or repairing of preformed parts
    • 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
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

  • the present invention relates to a method for joining at least one first inorganic molded article produced by injection molding from powder injection molding compositions with at least one second inorganic molded article produced by a method other than injection molding and the use of this method.
  • the molded articles produced by the known method have the advantages over other production methods, among others, that there is a wide range of available materials, that complex geometries can be produced and that close tolerances can be achieved without post-processing (accuracy approx. +/- 0.3% ) and good surfaces can be achieved.
  • DE-A-101 27 626 discloses a method of joining two elements, wherein the first element is made by injection molding.
  • the object of the present invention is to provide an improved method for permanently connecting inorganic moldings produced by injection molding of powder injection molding materials with inorganic moldings produced by methods other than injection molding.
  • an inexpensively feasible cohesive connection of these moldings is to be made possible while reducing manufacturing costs.
  • first a first inorganic molded body is produced by injection molding from powder injection molding compounds.
  • the first inorganic shaped body may be a metal body.
  • the powder injection molding compounds are, for example, in the form of injection-moldable granules containing both an inorganic powder (for example metal powder) and a binder.
  • the preferred injection molding compound used is a product from the Catamold® product range from BASF AG, Ludwigshafen, Germany.
  • Such injection molding compounds are known, for example, from DE 197 00 277 A1 or DE 40 21 739 A1.
  • standard machines for thermoplastic injection molding can be used. If necessary, the injection molding machine to the Material properties of the powder injection molding material of the first inorganic shaped body to be adjusted, for example, by special screw geometries or nozzles, by installing a return flow block or by increasing the wear protection.
  • the first inorganic shaped body is debindered.
  • Debinding is understood as meaning the removal of the binder from the first inorganic molding (green body) produced by injection molding.
  • the debinding method depends on the binder contained in the powder injection molding compound.
  • binder systems with thermally decomposable binders in particular waxes. These are removed from the first inorganic shaped body by a thermal debinding method (melting out or decomposing via the gas phase).
  • thermal debinding method melting out or decomposing via the gas phase.
  • solvent extraction removes the binder with solvents such as water or acetone.
  • the most common method is catalytic debinding, which allows for short debinding times.
  • the Catamold® powder injection molding compounds from BASF AG contain polyacetal as a binder.
  • polyacetal can be depolymerized in non-molten state in gaseous components and thus remove without residue from the injection molded part. This is made possible by the special chemical structure of the polyacetal.
  • Polyacetal unlike polyethylene, is characterized by recurrent carbon-oxygen bonds. At the oxygen atom of this group, acids can attack and split the macromolecule into the basic building blocks CH 2 O (formaldehyde).
  • the catalyst used is preferably gaseous nitric acid (> 99%).
  • the particular suitability of this chemical reaction for debindering in powder injection molding is to be seen in the conditions under which it takes place.
  • the polymer has a melting temperature of about 165 ° C. Debindering takes place well below the melting point at 110 to 140 ° C.
  • the reaction proceeds in the form of a front from outside to inside through the part to be debinded. In the reaction, the polymer goes directly from the solid to the gas state. The reaction gas can thus easily escape through the already porous shaped body zones. A pressure build-up and the resulting destruction of the molding can be avoided.
  • the resulting monomer has a boiling point of -21 ° C and is thus under degassing conditions in any case gaseous. In principle, a 100% debinding could be achieved in this way.
  • the debindered first inorganic shaped body is called a Braunling.
  • step c) of the process according to the invention a sintering process is performed with the assembled first and second inorganic moldings.
  • the second inorganic molded article is an inorganic molded article produced by a method other than injection molding, for example, a molded article produced by press-sintering, casting, forging, milling or turning.
  • Sintering is a heat treatment process in which the loose powder structure of the debindered first inorganic shaped body (Braunling) is compacted into the finished component and simultaneously bonded to the second inorganic shaped body.
  • a thermally activated material transport takes place, which leads to a decrease in the specific surface area of the inorganic powder particles.
  • the first inorganic shaped body shrinks during sintering in step c) of the method according to the invention.
  • particle contacts between the particles of the first inorganic shaped body and of the second inorganic shaped body are produced by the sintering process at contact surfaces of the molded bodies assembled before the sintering process is carried out. The result is a cohesive bond between the two moldings.
  • the inventive method thus allows the cost-effective combination of inorganic injection molded articles with inorganic non-injection molded articles in large quantities.
  • the first inorganic shaped body and the second inorganic shaped body can be combined in the present invention before step b) of the method according to the invention or before step c) of the method according to the invention. If the shaped bodies are assembled before step b), they jointly pass through the debinding step b).
  • the process steps b) and c) according to the invention are carried out in two different furnaces (debinding and sintering furnace) or successively in a single furnace.
  • the joining of the shaped bodies before step b) has the advantage that the brittle brown compact (the debinded first molded body) no longer has to be moved individually before carrying out the sintering process and thus avoiding possible breakage of the brown compact.
  • the inorganic sinterable powder A can be selected from any known suitable inorganic sinterable powders. Preferably, it is selected from metal powders, metal alloy powders, metal carbonyl powders, and mixtures thereof.
  • metals which may be present in powder form are iron, cobalt, nickel and silicon. Alloys are, for example, light alloys based on aluminum and titanium and alloys of copper or bronze. Hard metals such as tungsten carbide, boron carbide or titanium nitride are also suitable in combination with metals such as cobalt and nickel. Suitable powders are described, for example, in EP-A 0 465 940, EP-A 0 710 516, DE-A 39 36 869, DE-A 40 00 278 and EP-A 0 114 746 and the literature cited therein.
  • the particle sizes of the powders are preferably 0.1 to 50 ⁇ m, more preferably 0.2 to 8 ⁇ m.
  • the metal powder, metal alloy powder, Metallcarbonylpulver can also be used in a mixture.
  • component C dispersing aid may be selected from known dispersing aids.
  • examples are oligomeric polyethylene oxide having an average molecular weight of 200 to 600, stearic acid, stearic acid amide, hydroxystearic acid, fatty alcohols, fatty alcohol sulfonates and block copolymers of ethylene and propylene oxide, as well as particularly preferred polyisobutylene.
  • Polyisobutylene is particularly preferably used in an amount of 1 to 6% by volume, based on the components A, B and C.
  • thermoplastic compositions may also contain conventional additives and processing aids which favorably influence the rheological properties of the mixtures during the shaping.
  • the at least one second inorganic shaped body contains at least one material from the group of low-alloyed steels, stainless steels, tool steel, soft magnetic alloys, light metals, heavy metals, copper base materials or precious metals.
  • This sintering process is particularly suitable for powder injection molding compounds from the Catamold® product range from BASF AG.
  • the sintering process must be adapted to the respective material to be sintered.
  • the temperature program mentioned above it is taken into account that, after debindering in step b), there is still a small proportion of residual binder in the first inorganic shaped body.
  • the maximum sintering temperature to be achieved depends on the material of the first and second inorganic shaped bodies.
  • the sintering process preferably takes place in inert gas or in a vacuum.
  • the protective gas atmosphere or the vacuum are necessary to prevent unwanted chemical reactions during sintering. When selecting the atmosphere, all should be possible between the gas, the sintered material and the furnace Reactions are considered.
  • Possible shielding gases are hydrogen, argon or nitrogen or a mixture thereof.
  • a lubricant is applied to at least portions of the mating surfaces of the assembled first and second inorganic moldings prior to step c).
  • the lubricant is used to ensure the shrinkage of the first inorganic shaped body during the sintering process without hindrance and without an undesirable at certain points cohesive connection of the moldings.
  • the lubricant is therefore applied before the sintering step on surface portions of the moldings, which touch after their joining, but should not be firmly connected by the sintering, but on which the first inorganic molded body slides by the shrinkage during sintering.
  • a necessary property of the slip aid is therefore its sliding action at the maximum sintering temperature (second holding temperature).
  • Preferred lubricity aids for the process according to the invention are boron nitride, molybdenum sulfide or molybdenum disulfide.
  • a polymer film is interposed between certain surfaces to be sintered together.
  • the polymer film can fulfill various functions. It can provide a better bond between the first inorganic molded article and the second inorganic molded article because it has a melting point lower than the maximum sintering temperature and thus exhibits an adhesive effect between the molded articles during the sintering process. It can also release carbon, which diffuses into the surfaces of both moldings, reduces the melting temperature there and thus enables sintering closer to the melting temperature.
  • the polymer film can be selected from any known suitable polymer film. Preferably, it contains a polymer from the group polyethylene (PE), polypropylene (PP) or polyvinyl chloride (PVC).
  • the present invention further includes the use of the inventive method for the production of transmission parts, gears, jewelry, levers, nozzles, covers, pump parts, electric motor parts, ball bearings, valves, weapon parts, sports equipment, household appliances, medical equipment, tools or parts thereof.
  • the use of the method according to the invention is not limited to the production of said workpieces.
  • Figure 1 shows in Figure i a section through two moldings, which are to be firmly connected to each other by means of the method according to the invention.
  • the first inorganic shaped body 1 is an annular workpiece, which is present in FIG. 1 as a green compact, that is to say produced by injection molding from a powder injection molding compound, or which is present as a brown compact, that is to say already debinded.
  • the powder injection molding material was, for example, an injection-moldable granulate for the production of sintered moldings from a low-alloy, case-hardenable steel of the type 8620.
  • the second inorganic molded part is, for example, a forging of high alloy steel. It has a cylindrical section 3 whose radius is smaller than the radius of the first inorganic molded part 1.
  • the two moldings 1 and 2 are joined together.
  • the annular first molded body 1 surrounds the cylindrical portion 3 of the second molded body 2, the symmetry lines 4 of the two molded bodies 1, 2 coinciding. If the first molded body 1 is still a binder-containing green compact, the binder removal is carried out according to the method according to the invention in the assembled state of the two molded bodies 1, 2 according to FIG. 2 of FIG. 1 before the sintering process begins.
  • the sintering process can be carried out next after the two shaped bodies 1, 2 have been assembled.
  • a (not shown) polymer film is preferably applied before sintering, which is consequently located between the sixteenzusinternden surfaces 6 and 7 of the two moldings 2 and 1 respectively.
  • FIG. 1 shows the molded bodies 1, 2 connected according to the method according to the invention after the sintering process has been carried out.
  • Shaped body 1 is "shrunk" onto the cylindrical section 3 of the second molded body 2 during sintering and sintered together with it on the surfaces 6, 7.
  • the thus manufactured workpiece 8 is for example a gear part.

Abstract

Method for permanently bonding an injection-molded inorganic molding (1) with a similar second molding (2) comprises: (A) injection molding the first component from a mixture of powder and binder; (B) removing binder from it; and (C) sintering the two components after they have been placed against each other.

Description

Die vorliegende Erfindung betrifft ein Verfahren zum Verbinden mindestens eines aus Pulverspritzgussmassen durch Spritzgießen hergestellten ersten anorganischen Formkörpers mit mindestens einem nach einem anderen Verfahren als Spritzgießen hergestellten zweiten anorganischen Formkörper und die Verwendung dieses Verfahrens.The present invention relates to a method for joining at least one first inorganic molded article produced by injection molding from powder injection molding compositions with at least one second inorganic molded article produced by a method other than injection molding and the use of this method.

Es ist bekannt, Formkörper aus anorganischen Materialien dadurch herzustellen, dass Metallpulver oder Keramikpulver mit Bindemitteln zu einer spritzgießfähigen Pulverspritzgussmasse vermischt werden, diese Pulverspritzgussmasse auf Spritzgussmaschinen zu Formkörpern ("Grünlinge") verarbeitet werden, diesen Formkörpern die Bindemittel entzogen werden ("Braunlinge") und die Formkörper anschließend gesintert werden. Ein solches Verfahren ist beispielsweise in der DE 40 00 278 A1 beschrieben. Diese deutsche Offenlegungsschrift bezieht sich auf ein Verfahren zur Herstellung eines anorganischen Sinterformteils durch Verformen eines Gemisches aus einem sinterbaren anorganischen Pulver und Polyoxymethylen als Bindemittel durch Spritzgießen oder Strangpressen zu einem Grünkörper, Entfernen des Bindemittels und Sintern. Dabei wird das Polyoxymethylen durch Behandeln des Grünkörpers in einer gasförmigen Bortrifluorid enthaltenden Atmosphäre entfernt.It is known to produce molded articles from inorganic materials in that metal powder or ceramic powder are mixed with binders to form an injection-moldable powder injection molding compound, these powder injection molding compound are processed on injection molding machines into moldings ("greenware"), the moldings are removed from the binder ("brownlings") and the shaped bodies are then sintered. Such a method is described for example in DE 40 00 278 A1. This German Offenlegungsschrift relates to a process for producing an inorganic sintered compact by deforming a mixture of a sinterable inorganic powder and polyoxymethylene as a binder by injection molding or extrusion molding into a green body, removing the binder and sintering. The polyoxymethylene is removed by treating the green body in a gaseous boron trifluoride-containing atmosphere.

Die nach dem bekannten Verfahren hergestellten Formkörper weisen gegenüber anderen Fertigungsverfahren unter anderem die Vorteile auf, dass dafür eine weite Bandbreite von verfügbaren Werkstoffen vorliegt, dass komplexe Geometrien hergestellt werden können und dass enge Toleranzen ohne Nachbearbeitung (Genauigkeit ca. +/-0,3%) und gute Oberflächen erzielt werden können.The molded articles produced by the known method have the advantages over other production methods, among others, that there is a wide range of available materials, that complex geometries can be produced and that close tolerances can be achieved without post-processing (accuracy approx. +/- 0.3% ) and good surfaces can be achieved.

Im Stand der Technik werden solche aus Pulverspritzgussmassen hergestellten organischen Formkörper mit anderen mittels anderer Fertigungsverfahren hergestellten Formkörpern je nach Material unter anderem durch Schweißen, Schrauben, Kleben oder Schmieden verbunden. Diese Fügeverfahren sind jedoch nicht für alle Werkstoffkombinationen gleich gut geeignet, es fallen häufig beim dauerhaften Zusammenfügen von einzelnen Formkörpern hohe Kosten an und die damit erzeugten Verbindungen zwischen zwei Formkörpern erfüllen nicht immer die an sie gestellten Anforderungen. So sind die bekannten Fügeverfahren insbesondere bei der Verbindung von hoch- und niedriglegierten Stählen problematisch, da hier häufig eine chemische Korrosion einsetzt. Weiterhin sind z.B. gehärtete Werkzeugstähle sowie Superlegierungen wie Hastelloy® von Haynes, Kokomo, USA mechanisch nur mit hohem technischem Aufwand zu bearbeiten.In the prior art, such molded articles produced from powder injection molding compositions are combined, inter alia, by welding, screwing, gluing or forging, with other shaped articles produced by means of other production methods, depending on the material. However, these joining methods are not equally well suited for all material combinations, there are often high costs in the permanent assembly of individual moldings and the connections between two moldings produced therewith do not always meet the requirements placed on them. Thus, the known joining methods are problematic, especially in the connection of high and low alloy steels, since often a chemical corrosion is used here. Furthermore, hardened tool steels and superalloys such as Hastelloy® from Haynes, Kokomo, USA mechanically only with great technical effort to work.

DE-A-101 27 626 offenbart ein Verfahren zum Verbinden von zwei Elementen, wobei das erste Element durch Spritzgießen hergestellt wird.DE-A-101 27 626 discloses a method of joining two elements, wherein the first element is made by injection molding.

Daher ist die Aufgabe der vorliegenden Erfindung die Bereitstellung eines verbesserten Verfahrens zum dauerhaften Verbinden von aus Pulverspritzgussmassen durch Spritzgießen hergestellten anorganischen Formkörpern mit nach anderen Verfahren als Spritzgießen hergestellten anorganischen Formkörpern. Insbesondere soll eine unaufwendig durchführbare stoffschlüssige Verbindung dieser Formkörper unter Reduzierung von Fertigungskosten ermöglicht werden. Weiterhin ist es Aufgabe der vorliegenden Erfindung, das Zusammenfügen dieser Formkörper zu einer Einheit zu ermöglichen, die hohen mechanischen Belastungen standhält.Therefore, the object of the present invention is to provide an improved method for permanently connecting inorganic moldings produced by injection molding of powder injection molding materials with inorganic moldings produced by methods other than injection molding. In particular, an inexpensively feasible cohesive connection of these moldings is to be made possible while reducing manufacturing costs. Furthermore, it is an object of the present invention to allow the joining of these moldings into a unit that can withstand high mechanical loads.

Diese Aufgabe wird erfindungsgemäß gelöst durch ein Verfahren nach Anspruch 1.This object is achieved by a method according to claim 1.

In Schritt a) wird zunächst ein erster anorganischer Formkörper durch Spritzgießen aus Pulverspritzgussmassen hergestellt. Bei dem ersten anorganischen Formkörper kann es sich um einen Metallkörper handeln. Die Pulverspritzgussmassen liegen zum Beispiel als spritzgussfähiges Granulat vor, das sowohl ein anorganisches Pulver (zum Beispiel Metallpulver), als auch ein Bindemittel enthält. Vorzugsweise wird als Spritzgussmasse ein Produkt aus dem Catamold®-Produktsortiment der BASF AG, Ludwigshafen, Deutschland, verwendet. Solche Spritzgussmassen sind beispielsweise aus der DE 197 00 277 A1 oder der DE 40 21 739 A1 bekannt. Zum Spritzgießen des ersten anorganischen Formkörpers können Standardmaschinen für den Thermoplast-Spritzguss eingesetzt werden. Gegebenenfalls muss die Spritzgussmaschine an die Materialeigenschaften der Pulverspritzgussmasse des ersten anorganischen Formkörpers angepasst werden, zum Beispiel durch spezielle Schneckengeometrien oder Düsen, durch Einbau einer Rückstromsperre oder durch Erhöhung des Verschleißschutzes.In step a), first a first inorganic molded body is produced by injection molding from powder injection molding compounds. The first inorganic shaped body may be a metal body. The powder injection molding compounds are, for example, in the form of injection-moldable granules containing both an inorganic powder (for example metal powder) and a binder. The preferred injection molding compound used is a product from the Catamold® product range from BASF AG, Ludwigshafen, Germany. Such injection molding compounds are known, for example, from DE 197 00 277 A1 or DE 40 21 739 A1. For injection molding of the first inorganic shaped body standard machines for thermoplastic injection molding can be used. If necessary, the injection molding machine to the Material properties of the powder injection molding material of the first inorganic shaped body to be adjusted, for example, by special screw geometries or nozzles, by installing a return flow block or by increasing the wear protection.

In Schritt b) des erfindungsgemäßen Verfahrens wird der erste anorganische Formkörper entbindert. Unter Entbindern versteht man das weitgehende Entfernen des Bindemittels aus dem durch Spritzgießen hergestellten ersten anorganischen Formkörper (Grünling). Das Entbinderungsverfahren hängt von dem in der Pulverspritzgussmasse enthaltenen Bindemittel ab.In step b) of the process according to the invention, the first inorganic shaped body is debindered. Debinding is understood as meaning the removal of the binder from the first inorganic molding (green body) produced by injection molding. The debinding method depends on the binder contained in the powder injection molding compound.

Im Stand der Technik gibt es Bindersysteme mit thermisch zersetzbaren Bindern, insbesondere Wachsen. Diese werden durch ein thermisches Entbinderungsverfahren (Herausschmelzen oder Zersetzen über die Gasphase) aus dem ersten anorganischen Formkörper entfernt. Eine andere Entbinderungsmöglichkeit ist die Lösungsmittelextraktion, bei der das Bindemittel mit Lösemitteln wie Wasser oder Aceton entfernt wird.In the prior art there are binder systems with thermally decomposable binders, in particular waxes. These are removed from the first inorganic shaped body by a thermal debinding method (melting out or decomposing via the gas phase). Another debinding option is solvent extraction, which removes the binder with solvents such as water or acetone.

Das am weitesten verbreitete Verfahren ist die katalytische Entbinderung, die kurze Entbinderungszeiten ermöglicht. Beispielsweise enthalten die Catamold®-Pulverspritzgussmassen der BASF AG Polyacetal als Binder. In Anwesenheit eines geeigneten Katalysators lässt sich Polyacetal bereits in nicht geschmolzenem Zustand in gasförmige Bestandteile depolymerisieren und folglich rückstandsfrei aus dem Spritzgussteil entfernen. Dies wird durch die besondere chemische Struktur des Polyacetals ermöglicht. Polyacetal ist im Gegensatz zu Polyethylen durch wiederkehrende Kohlenstoff-Sauerstoffbindungen gekennzeichnet. Am Sauerstoffatom dieser Gruppe können Säuren angreifen und das Makromolekül in die Grundbausteine CH2O (Formaldehyd) spalten. Als Katalysator wird vorzugsweise gasförmige Salpetersäure (> 99%) eingesetzt. Die besondere Tauglichkeit dieser chemischen Reaktion für die Entbinderung beim Pulverspritzguss ist an den Bedingungen zu sehen, unter denen sie stattfindet. Das Polymer hat eine Schmelztemperatur von ca. 165 °C. Die Entbinderung findet deutlich unterhalb der Schmelztemperatur bei 110 bis 140 °C statt. Die Reaktion schreitet in Form einer Front von außen nach innen durch das zu entbindernde Teil. Bei der Reaktion geht das Polymer direkt vom Feststoff in den Gaszustand über. Das Reaktionsgas kann damit sehr leicht durch die bereits porösen Formkörperzonen entweichen. Ein Druckaufbau und die daraus resultierende Zerstörung des Formkörpers kann so vermieden werden. Das entstehende Monomer hat eine Siedetemperatur von -21 °C und ist damit unter Entbinderungsbedingungen auf jeden Fall gasförmig. Im Prinzip könnte auf diese Art und Weise eine 100%ige Entbinderung erreicht werden. Solche Formkörper würden jedoch bei der geringsten Erschütterung zerfallen. Deshalb besteht ein geringer Anteil des Binders aus einem Polymer, das gegenüber dem Katalysator resistent ist und dem Formkörper ausreichend Festigkeit für die weitere Verarbeitung verleiht. Dieser Anteil wird beim anschließenden Sinterprozess ausgetrieben. Den entbinderten ersten anorganischen Formkörper nennt man einen Braunling.The most common method is catalytic debinding, which allows for short debinding times. For example, the Catamold® powder injection molding compounds from BASF AG contain polyacetal as a binder. In the presence of a suitable catalyst, polyacetal can be depolymerized in non-molten state in gaseous components and thus remove without residue from the injection molded part. This is made possible by the special chemical structure of the polyacetal. Polyacetal, unlike polyethylene, is characterized by recurrent carbon-oxygen bonds. At the oxygen atom of this group, acids can attack and split the macromolecule into the basic building blocks CH 2 O (formaldehyde). The catalyst used is preferably gaseous nitric acid (> 99%). The particular suitability of this chemical reaction for debindering in powder injection molding is to be seen in the conditions under which it takes place. The polymer has a melting temperature of about 165 ° C. Debindering takes place well below the melting point at 110 to 140 ° C. The reaction proceeds in the form of a front from outside to inside through the part to be debinded. In the reaction, the polymer goes directly from the solid to the gas state. The reaction gas can thus easily escape through the already porous shaped body zones. A pressure build-up and the resulting destruction of the molding can be avoided. The resulting monomer has a boiling point of -21 ° C and is thus under degassing conditions in any case gaseous. In principle, a 100% debinding could be achieved in this way. However, such moldings would disintegrate at the slightest vibration. Therefore, a small proportion of the binder consists of a polymer that is opposite to the catalyst is resistant and gives the molded body sufficient strength for further processing. This proportion is expelled during the subsequent sintering process. The debindered first inorganic shaped body is called a Braunling.

In Schritt c) des erfindungsgemäßen Verfahrens wird ein Sinterverfahren mit den zusammengefügten ersten und zweiten anorganischen Formkörpern durchgeführt.In step c) of the process according to the invention, a sintering process is performed with the assembled first and second inorganic moldings.

Der zweite anorganische Formkörper ist ein nach einem anderen Verfahren als Spritzgießen hergestellter anorganischer Formkörper, beispielsweise ein durch Press-Sintern, Gießen, Schmieden, Fräsen oder Drehen hergestelltes Formteil.The second inorganic molded article is an inorganic molded article produced by a method other than injection molding, for example, a molded article produced by press-sintering, casting, forging, milling or turning.

Unter Sintern ist ein Wärmebehandlungsverfahren zu verstehen, bei dem das lose Pulvergerüst des entbinderten ersten anorganischen Formkörpers (Braunling) zum fertigen Bauteil verdichtet und gleichzeitig mit dem zweiten anorganischen Formkörper verbunden wird. Beim Sintern findet ein thermisch aktivierter Materialtransport statt, der zu einer Abnahme der spezifischen Oberfläche der anorganischen Pulverteilchen führt. Durch das Wachstum von Teilchenkontakten und die Verringerung des Porenvolumens schrumpft der erste anorganische Formkörper beim Sintern in Schritt c) des erfindungsgemäßen Verfahrens. Ferner entstehen durch das Sinterverfahren an Berührungsflächen der vor der Durchführung des Sinterverfahrens zusammengefügten Formkörper Teilchenkontakte zwischen den Teilchen des ersten anorganischen Formkörpers und des zweiten anorganischen Formkörpers. Es entsteht ein stoffschlüssiger Verbund zwischen den zwei Formkörpern.Sintering is a heat treatment process in which the loose powder structure of the debindered first inorganic shaped body (Braunling) is compacted into the finished component and simultaneously bonded to the second inorganic shaped body. During sintering, a thermally activated material transport takes place, which leads to a decrease in the specific surface area of the inorganic powder particles. Due to the growth of particle contacts and the reduction of the pore volume, the first inorganic shaped body shrinks during sintering in step c) of the method according to the invention. Furthermore, particle contacts between the particles of the first inorganic shaped body and of the second inorganic shaped body are produced by the sintering process at contact surfaces of the molded bodies assembled before the sintering process is carried out. The result is a cohesive bond between the two moldings.

Das erfindungsgemäße Verfahren ermöglicht folglich die kostengünstige Verbindung von anorganischen Spritzguss-Formkörpern mit anorganischen Nicht-Spritzguss-Formkörpern in großen Stückzahlen.The inventive method thus allows the cost-effective combination of inorganic injection molded articles with inorganic non-injection molded articles in large quantities.

Der erste anorganische Formkörper und der zweite anorganische Formkörper können bei der vorliegenden Erfindung vor Schritt b) des erfindungsgemäßen Verfahrens oder vor Schritt c) des erfindungsgemäßen Verfahrens zusammengefügt werden. Wenn die Formkörper vor Schritt b) zusammengesetzt werden, durchlaufen sie gemeinsam den Entbinderungsschritt b). Dabei werden die erfindungsgemäßen Verfahrensschritte b) und c) in zwei verschiedenen Öfen (Entbinderungs- und Sinterofen) oder nacheinander in einem einzigen Ofen durchgeführt. Das Zusammenfügen der Formkörper vor Schritt b) hat den Vorteil, dass der brüchige Braunling (der entbinderte erste Formkörper) nicht mehr einzeln vor der Durchführung des Sinterverfahrens bewegt werden muss und somit ein mögliches Zerbrechen des Braunlings vermieden wird. Ein vorsichtiges Zusammenfügen der Formkörper nach dem Entbindern des ersten anorganischen Formkörpers und vor der Durchführung des gemeinsamen Sinterverfahrens ist jedoch ebenfalls möglich.The first inorganic shaped body and the second inorganic shaped body can be combined in the present invention before step b) of the method according to the invention or before step c) of the method according to the invention. If the shaped bodies are assembled before step b), they jointly pass through the debinding step b). The process steps b) and c) according to the invention are carried out in two different furnaces (debinding and sintering furnace) or successively in a single furnace. The joining of the shaped bodies before step b) has the advantage that the brittle brown compact (the debinded first molded body) no longer has to be moved individually before carrying out the sintering process and thus avoiding possible breakage of the brown compact. A careful joining of the moldings after debinding the first inorganic shaped body and before performing the common sintering process, however, is also possible.

In einer bevorzugten Ausführungsform der vorliegenden Erfindung enthält die Pulverspritzgussmasse zum Spritzgießen des ersten anorganischen Formkörpers

  1. i) 40 bis 85 Vol-% mindestens eines anorganischen sinterbaren Pulvers A,
  2. ii) 15 bis 60 Vol-% mindestens eines Bindemittels B und
  3. iii) 0 bis 5 Vol-% mindestens eines Dispergierhilfsmittels C, wobei die Summe der Komponenten A, B und C 100 Vol-% ergibt.
In a preferred embodiment of the present invention, the powder injection molding material for injection molding of the first inorganic molded article
  1. i) 40 to 85% by volume of at least one inorganic sinterable powder A,
  2. ii) 15 to 60% by volume of at least one binder B and
  3. iii) 0 to 5% by volume of at least one dispersing aid C, the sum of the components A, B and C giving 100% by volume.

Das anorganische sinterbare Pulver A kann aus allen bekannten geeigneten anorganischen sinterbaren Pulvern ausgewählt werden. Vorzugsweise ist es aus Metallpulvern, Metalllegierungspulvern, Metallcarbonylpulvern und Gemischen davon ausgewählt.The inorganic sinterable powder A can be selected from any known suitable inorganic sinterable powders. Preferably, it is selected from metal powders, metal alloy powders, metal carbonyl powders, and mixtures thereof.

Als Metalle, die in Pulverform vorliegen können, seien beispielsweise Eisen, Kobalt, Nickel und Silizium genannt. Legierungen sind beispielsweise Leichtmetalllegierungen auf der Basis von Aluminium und Titan sowie Legierungen von Kupfer oder Bronze. Auch Hartmetalle wie Wolframcarbid, Borcarbid oder Titannitrid kommen in Kombination mit Metallen wie Kobalt und Nickel in Betracht. Geeignete Pulver sind beispielsweise in EP-A 0 465 940, EP-A 0 710 516, DE-A 39 36 869, DE-A 40 00 278 und EP-A 0 114 746 sowie der darin zitierten Literatur beschrieben.Examples of metals which may be present in powder form are iron, cobalt, nickel and silicon. Alloys are, for example, light alloys based on aluminum and titanium and alloys of copper or bronze. Hard metals such as tungsten carbide, boron carbide or titanium nitride are also suitable in combination with metals such as cobalt and nickel. Suitable powders are described, for example, in EP-A 0 465 940, EP-A 0 710 516, DE-A 39 36 869, DE-A 40 00 278 and EP-A 0 114 746 and the literature cited therein.

Die Korngrößen der Pulver betragen vorzugsweise 0,1 bis 50 µm, besonders bevorzugt 0,2 bis 8 µm. Die Metallpulver, Metalllegierungspulver, Metallcarbonylpulver können auch im Gemisch eingesetzt werden.The particle sizes of the powders are preferably 0.1 to 50 μm, more preferably 0.2 to 8 μm. The metal powder, metal alloy powder, Metallcarbonylpulver can also be used in a mixture.

Das als Komponente C gegebenenfalls vorliegende Dispergierhilfsmittel kann aus bekannten Dispergierhilfsmitteln ausgewählt sein. Beispiele sind oligomeres Polyethylenoxid mit einem mittleren Molekulargewicht von 200 bis 600, Stearinsäure, Stearinsäureamid, Hydroxystearinsäure, Fettalkohole, Fettalkoholsulfonate und Blockcopolymere von Ethylen- und Propylenoxid, wie auch besonders bevorzugt Polyisobutylen. Besonders bevorzugt wird Polyisobutylen in einer Menge von 1 bis 6 Vol-%, bezogen auf die Komponente A, B und C eingesetzt.The optionally present as component C dispersing aid may be selected from known dispersing aids. Examples are oligomeric polyethylene oxide having an average molecular weight of 200 to 600, stearic acid, stearic acid amide, hydroxystearic acid, fatty alcohols, fatty alcohol sulfonates and block copolymers of ethylene and propylene oxide, as well as particularly preferred polyisobutylene. Polyisobutylene is particularly preferably used in an amount of 1 to 6% by volume, based on the components A, B and C.

Zusätzlich können die thermoplastischen Massen auch übliche Zusatzstoffe und Bearbeitungshilfsmittel, die die rheologischen Eigenschaften der Mischungen bei der Verformung günstig beeinflussen, enthalten.In addition, the thermoplastic compositions may also contain conventional additives and processing aids which favorably influence the rheological properties of the mixtures during the shaping.

Vorzugsweise enthält der mindestens eine zweite anorganische Formkörper mindestens einen Werkstoff aus der Gruppe niedrig legierte Stähle, rostfreie Stähle, Werkzeugstahl, weichmagnetische Legierungen, Leichtmetalle, Schwermetalle, Kupferbasiswerkstoffe oder Edelmetalle.Preferably, the at least one second inorganic shaped body contains at least one material from the group of low-alloyed steels, stainless steels, tool steel, soft magnetic alloys, light metals, heavy metals, copper base materials or precious metals.

In einer bevorzugten Ausführungsform der vorliegenden Erfindung umfasst das Sinterverfahren, das in einem Ofen durchgeführt wird, folgende Schritte:

  1. A) Aufheizen des Ofens mit den zusammengefügten ersten und zweiten anorganischen Formkörpern von Raumtemperatur auf eine erste Haltetemperatur von 300 bis 700°C, bevorzugt von 550 bis 650°C, mit einer Rate zwischen 2 und 10 K/min, bevorzugt zwischen 4 und 6 K/min,
  2. B) Halten der ersten Haltetemperatur, vorzugsweise während eines Zeitraumes zwischen 0,5 und 3 h,
  3. C) Aufheizen des Ofens auf eine zweite Haltetemperatur von 1000 bis 1400°C, bevorzugt auf 1200 bis 1300°C, mit einer Rate zwischen 2 und 10 K/min, bevorzugt zwischen 4 und 6 K/min,
  4. D) Halten der zweiten Haltetemperatur, vorzugsweise während eines Zeitraumes zwischen 2 und 12h und
  5. E) Abkühlen des Ofens mit einer Rate zwischen 2 und 20 K/min.
In a preferred embodiment of the present invention, the sintering process carried out in an oven comprises the following steps:
  1. A) heating the oven with the assembled first and second inorganic moldings from room temperature to a first holding temperature of 300 to 700 ° C, preferably from 550 to 650 ° C, at a rate between 2 and 10 K / min, preferably between 4 and 6 K / min,
  2. B) holding the first holding temperature, preferably for a period between 0.5 and 3 h,
  3. C) heating the furnace to a second holding temperature of 1000 to 1400 ° C, preferably 1200 to 1300 ° C, at a rate between 2 and 10 K / min, preferably between 4 and 6 K / min,
  4. D) holding the second holding temperature, preferably during a period between 2 and 12h and
  5. E) Cool the furnace at a rate between 2 and 20 K / min.

Dieses Sinterverfahren ist insbesondere für Pulverspritzgussmassen aus dem Catamold®-Produktsortiment der BASF AG geeignet. Im Allgemeinen muss das Sinterverfahren auf den jeweiligen zu sinternden Werkstoff abgestimmt sein. Bei dem oben genannten Temperaturprogramm wird berücksichtigt, dass sich nach dem Entbindern in Schritt b) noch ein geringer Anteil Restbinder im ersten anorganischen Formkörper befindet. Durch das Halten der ersten Haltetemperatur in Schritt B) erfolgt die vollständige thermische Zersetzung dieses Restbindemittels. Die zu erreichende maximale Sintertemperatur (zweite Haltetemperatur in Schritt C)) hängt von den Werkstoff des ersten und zweiten anorganischen Formkörpers ab.This sintering process is particularly suitable for powder injection molding compounds from the Catamold® product range from BASF AG. In general, the sintering process must be adapted to the respective material to be sintered. In the temperature program mentioned above, it is taken into account that, after debindering in step b), there is still a small proportion of residual binder in the first inorganic shaped body. By keeping the first holding temperature in step B), the complete thermal decomposition of this residual binder takes place. The maximum sintering temperature to be achieved (second holding temperature in step C)) depends on the material of the first and second inorganic shaped bodies.

Das Sinterverfahren findet vorzugsweise in Schutzgas oder im Vakuum statt. Die Schutzgasatmosphäre beziehungsweise das Vakuum sind notwendig, um unerwünschte chemische Reaktionen während des Sinterns zu verhindern. Bei der Auswahl der Atmosphäre sollen alle zwischen dem Gas, dem Sintergut und der Ofenanlage möglichen Reaktionen berücksichtigt werden. Mögliche Schutzgase sind Wasserstoff, Argon oder Stickstoff oder ein Gemisch daraus.The sintering process preferably takes place in inert gas or in a vacuum. The protective gas atmosphere or the vacuum are necessary to prevent unwanted chemical reactions during sintering. When selecting the atmosphere, all should be possible between the gas, the sintered material and the furnace Reactions are considered. Possible shielding gases are hydrogen, argon or nitrogen or a mixture thereof.

In der vorliegenden Erfindung wird auf mindestens Teile der Berührungsflächen der zusammengefügten ersten und zweiten anorganischen Formkörper vor Schritt c) ein Gleithilfsmittel aufgetragen. Das Gleithilfsmittel dient dazu, das Schrumpfen des ersten anorganischen Formkörpers während des Sinterprozesses ohne Behinderung und ohne eine an bestimmten Stellen unerwünschte stoffschlüssige Verbindung der Formteile zu gewährleisten. Das Gleithilfsmittel wird daher vor dem Sinterschritt auf Oberflächenabschnitte der Formteile aufgetragen, die sich nach ihrem Zusammenfügen berühren, die aber nicht durch das Sintern fest verbunden werden sollen, sondern auf denen der erste anorganische Formkörper durch das Schrumpfen beim Sintern entlanggleitet. Eine notwendige Eigenschaft des Gleithilfsmittels ist daher seine Gleitwirkung bei der maximalen Sintertemperatur (zweite Haltetemperatur). Bevorzugte Gleithilfsmittel für das erfindungsgemäße Verfahren sind Bornitrid, Molybdänsulfid oder Molybdändisulfid.In the present invention, a lubricant is applied to at least portions of the mating surfaces of the assembled first and second inorganic moldings prior to step c). The lubricant is used to ensure the shrinkage of the first inorganic shaped body during the sintering process without hindrance and without an undesirable at certain points cohesive connection of the moldings. The lubricant is therefore applied before the sintering step on surface portions of the moldings, which touch after their joining, but should not be firmly connected by the sintering, but on which the first inorganic molded body slides by the shrinkage during sintering. A necessary property of the slip aid is therefore its sliding action at the maximum sintering temperature (second holding temperature). Preferred lubricity aids for the process according to the invention are boron nitride, molybdenum sulfide or molybdenum disulfide.

In einer bevorzugten Ausführungsform der vorliegenden Erfindung wird vor dem Durchführen des Sinterverfahrens eine Polymerfolie zwischen bestimmte zusammenzusinternde Oberflächen eingefügt. Die Polymerfolie kann dabei verschiedene Funktionen erfüllen. Sie kann für einen besseren Verbund zwischen dem ersten anorganischen Formkörper und dem zweiten anorganischen Formkörper sorgen, da sie einen niedrigeren Schmelzpunkt als die maximale Sintertemperatur besitzt und folglich während des Sinterverfahrens eine Klebewirkung zwischen den Formkörpern entfaltet. Ferner kann sie Kohlenstoff abgeben, das in die Oberflächen beider Formkörper diffundiert, die Schmelztemperatur dort verringert und somit ein Sintern näher bei der Schmelztemperatur ermöglicht. Die Polymerfolie kann aus allen bekannten geeigneten Polymerfolien ausgewählt werden. Vorzugsweise enthält sie ein Polymer aus der Gruppe Polyethylen (PE), Polypropylen (PP) oder Polyvinylchlorid (PVC).In a preferred embodiment of the present invention, prior to carrying out the sintering process, a polymer film is interposed between certain surfaces to be sintered together. The polymer film can fulfill various functions. It can provide a better bond between the first inorganic molded article and the second inorganic molded article because it has a melting point lower than the maximum sintering temperature and thus exhibits an adhesive effect between the molded articles during the sintering process. It can also release carbon, which diffuses into the surfaces of both moldings, reduces the melting temperature there and thus enables sintering closer to the melting temperature. The polymer film can be selected from any known suitable polymer film. Preferably, it contains a polymer from the group polyethylene (PE), polypropylene (PP) or polyvinyl chloride (PVC).

Die vorliegende Erfindung umfasst weiterhin die Verwendung des erfindungsgemäßen Verfahrens zur Herstellung von Getriebeteilen, Zahnrädern, Schmuck, Hebeln, Düsen, Deckeln, Pumpenteilen, Elektromotorteilen, Kugellagern, Ventilen, Waffenteilen, Sportgeräten, Haushaltsgeräten, medizinischen Geräten, Werkzeugen oder Teilen davon. Die Verwendung des erfindungsgemäßen Verfahrens ist jedoch nicht auf die Herstellung der genannten Werkstücke beschränkt.The present invention further includes the use of the inventive method for the production of transmission parts, gears, jewelry, levers, nozzles, covers, pump parts, electric motor parts, ball bearings, valves, weapon parts, sports equipment, household appliances, medical equipment, tools or parts thereof. However, the use of the method according to the invention is not limited to the production of said workpieces.

Zeichnungdrawing

Anhand der Zeichnung wird die Erfindung nachstehend näher erläutert.

Figur 1
zeigt schematisch den Ablauf des erfindungsgemäßen Verfahrens in seiner bevorzugten Ausführungsform.
Reference to the drawings, the invention will be explained in more detail below.
FIG. 1
schematically shows the sequence of the method according to the invention in its preferred embodiment.

Figur 1 zeigt in Abbildung i einen Schnitt durch zwei Formkörper, die mit Hilfe des erfindungsgemäßen Verfahrens fest miteinander verbunden werden sollen.Figure 1 shows in Figure i a section through two moldings, which are to be firmly connected to each other by means of the method according to the invention.

Der erste anorganische Formkörper 1 ist ein ringförmiges Werkstück, das in Abbildung i als Grünling vorliegt, also mittels Spritzgießen aus einer Pulverspritzgussmasse hergestellt wurde, oder das als Braunling vorliegt, also bereits entbindert ist. Die Pulverspritzgussmasse war beispielsweise ein spritzgussfähiges Granulat zur Herstellung von gesinterten Formteilen aus einem niedrig legierten, einsatzhärtbaren Stahl vom Typ 8620.The first inorganic shaped body 1 is an annular workpiece, which is present in FIG. 1 as a green compact, that is to say produced by injection molding from a powder injection molding compound, or which is present as a brown compact, that is to say already debinded. The powder injection molding material was, for example, an injection-moldable granulate for the production of sintered moldings from a low-alloy, case-hardenable steel of the type 8620.

Das zweite anorganische Formteil ist beispielsweise ein Schmiedeteil aus hoch legiertem Stahl. Es weist einen zylinderförmigen Abschnitt 3 auf, dessen Radius kleiner als der Radius des ersten anorganischen Formteils 1 ist.The second inorganic molded part is, for example, a forging of high alloy steel. It has a cylindrical section 3 whose radius is smaller than the radius of the first inorganic molded part 1.

In Abbildung ii der Figur 1 sind die beiden Formkörper 1 und 2 zusammengefügt. Der ringförmige erste Formkörper 1 umgibt den zylinderförmigen Abschnitt 3 des zweiten Formkörpers 2, wobei die Symmetrielinien 4 der beiden Formkörper 1, 2 zusammenfallen. Falls es sich bei dem ersten Formkörper 1 um einen noch binderhaltigen Grünling handelt, wird die Entbinderung entsprechend dem erfindungsgemäßen Verfahren im zusammengefügten Zustand der beiden Formkörper 1, 2 gemäß Abbildung ii der Figur 1 durchgeführt, bevor das Sinterverfahren beginnt.In Figure ii of Figure 1, the two moldings 1 and 2 are joined together. The annular first molded body 1 surrounds the cylindrical portion 3 of the second molded body 2, the symmetry lines 4 of the two molded bodies 1, 2 coinciding. If the first molded body 1 is still a binder-containing green compact, the binder removal is carried out according to the method according to the invention in the assembled state of the two molded bodies 1, 2 according to FIG. 2 of FIG. 1 before the sintering process begins.

Falls es sich bei dem ersten Formkörper 1 um einen entbinderten Braunling handelt, kann nach dem Zusammenfügen der beiden Formkörper 1, 2 als nächstes das Sinterverfahren durchgeführt werden.If the first shaped body 1 is a debinded Braunling, the sintering process can be carried out next after the two shaped bodies 1, 2 have been assembled.

Auf den Berührungsflächen 5 der beiden Formteile, auf denen der erste Formkörper 1 während seines Schrumpfens aufgrund des Sinterns entlanggleitet, wird ein (nicht dargestelltes) Gleithilfsmittel aufgetragen.On the contact surfaces 5 of the two mold parts, on which slides the first molded body 1 during its shrinkage due to sintering, a (not shown) sliding lubricant is applied.

An einer Oberfläche 6 des zweiten Formkörpers wird vor dem Sintern vorzugsweise eine (nicht dargestellte) Polymerfolie angelegt, die sich folglich zwischen den zusammenzusinternden Oberflächen 6 und 7 der beiden Formkörper 2 beziehungsweise 1 befindet.On a surface 6 of the second molded body, a (not shown) polymer film is preferably applied before sintering, which is consequently located between the zusammenzusinternden surfaces 6 and 7 of the two moldings 2 and 1 respectively.

Abbildung iii der Figur 1 zeigt die gemäß dem erfindungsgemäßen Verfahren verbundenen Formkörper 1, 2 nach dem Durchführen des Sinterverfahrens. Formkörper 1 ist während des Sinterns auf den zylinderförmigen Abschnitt 3 des zweiten Formkörpers 2 "aufgeschrumpft" und mit diesem an den Oberflächen 6, 7 zusammengesintert. Das so gefertigte Werkstück 8 ist beispielsweise ein Getriebeteil.FIG. 1 shows the molded bodies 1, 2 connected according to the method according to the invention after the sintering process has been carried out. Shaped body 1 is "shrunk" onto the cylindrical section 3 of the second molded body 2 during sintering and sintered together with it on the surfaces 6, 7. The thus manufactured workpiece 8 is for example a gear part.

BezugszeichenlisteLIST OF REFERENCE NUMBERS

11
erster anorganischer Formkörperfirst inorganic molded article
22
zweiter anorganischer Formkörpersecond inorganic shaped body
33
zylinderförmiger Abschnittcylindrical section
44
Symmetrielinienlines of symmetry
55
Berührungsflächencontact surfaces
66
zusammenzusinternde Oberfläche des zweiten Formkörperszusammenzusinternde surface of the second molded body
77
zusammenzusinternde Oberfläche des ersten Formkörperszusammenzusinternde surface of the first molded body
88th
Werkstückworkpiece

Claims (9)

  1. A method for permanently bonding at least one first inorganic molding (1) produced from powder injection molding materials by injection molding to at least one second inorganic molding (2) produced by a method other than injection molding, comprising the method steps:
    a) injection molding the first inorganic molding (1) from binder-comprising powder injection molding materials,
    b) removing binder from the first inorganic molding (1) and
    c) carrying out a sinter process with the first and second inorganic moldings (1, 2) which have been fitted together,
    the at least one first inorganic molding (1) and the at least one second inorganic molding (2) being fitted together before step b) or before step c), wherein a lubricant is applied to at least parts of contact surfaces (5) of the assembled first and second inorganic moldings (1, 2) before the sinter process is carried out.
  2. The method according to claim 1, wherein the powder injection molding material for injection molding of the first inorganic molding (1) comprises
    i) from 40 to 85% by volume of at least one inorganic sinterable powder A),
    ii) from 15 to 60% by volume of at least one binder B and
    iii) from 0 to 5% by volume of at least one dispersant C,
    the sum of the components A, B and C being 100% by volume.
  3. The method according to claim 2, wherein the powder A is selected from metal powders, metal alloy powders, metal carbonyl powders and mixtures thereof.
  4. The method according to any of claims 1 to 3, wherein the at least one second inorganic molding (2) comprises at least one material from the group consisting of low-alloy steel, stainless steels, tool steel, magnetically soft alloys, light metals, heavy metals, copper-based materials or noble metals.
  5. The method according to any of claims 1 to 4, wherein the sinter process is carried out in a furnace and comprises the following steps:
    A) heating the furnace containing the assembled first and second inorganic moldings (1, 2) from room temperature to a first hold temperature of from 300 to 700°C at a rate of from 2 to 10 K/min,
    B) maintaining the first hold temperature,
    C) heating the furnace to a second hold temperature of from 1000 to 1400°C at a rate of from 2 to 10 K/min,
    D) maintaining the second hold temperature and
    E) cooling the furnace at a rate of from 2 to 20 K/min.
  6. The method according to any of claims 1 to 5, wherein the lubricant is boron nitride, molybdenum sulfide or molydenum disulfide.
  7. The method according to any of claims 1 to 6, wherein a polymer film is inserted, before the sinter process is carried out, between certain surfaces (6, 7) to be sintered together.
  8. The method according to claim 7, wherein the polymer film comprises a polymer from the group consisting of polyethylene, polypropylene or polyvinyl chloride.
  9. The use of the method according to any of claims 1 to8 for producing gear parts, gear wheels, jewelry, levers, nozzles, covers, pump parts, electric motor parts, ball bearings, valves, weapons parts, sports apparatuses, household appliances, medical equipment, tools or parts thereof.
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ATE359889T1 (en) 2007-05-15
PT1563931E (en) 2007-05-31
EP1563931A1 (en) 2005-08-17
US20050182176A1 (en) 2005-08-18
DE502005000591D1 (en) 2007-05-31
DE102004006954A1 (en) 2005-09-01
ES2285580T3 (en) 2007-11-16
JP2005226160A (en) 2005-08-25
PL1563931T3 (en) 2007-09-28

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