EP0968068B1 - Compacting auxiliary agent for producing sinterable shaped parts from a metal powder - Google Patents

Compacting auxiliary agent for producing sinterable shaped parts from a metal powder Download PDF

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Publication number
EP0968068B1
EP0968068B1 EP98964406A EP98964406A EP0968068B1 EP 0968068 B1 EP0968068 B1 EP 0968068B1 EP 98964406 A EP98964406 A EP 98964406A EP 98964406 A EP98964406 A EP 98964406A EP 0968068 B1 EP0968068 B1 EP 0968068B1
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EP
European Patent Office
Prior art keywords
compacting
metal powder
auxiliary
pressing
powder
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EP98964406A
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German (de)
French (fr)
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EP0968068A1 (en
Inventor
René LINDENAU
Klaus Dollmeier
Wieland Kynast
Jens Wahnschaffe
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GKN Sinter Metals GmbH
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GKN Sinter Metals GmbH
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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
    • B22F3/02—Compacting only
    • 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
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • 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
    • B22F3/02—Compacting only
    • B22F2003/023—Lubricant mixed with the metal powder
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME RELATING TO HINGES OR OTHER SUSPENSION DEVICES FOR DOORS, WINDOWS OR WINGS AND DEVICES FOR MOVING WINGS INTO OPEN OR CLOSED POSITION, CHECKS FOR WINGS AND WING FITTINGS NOT OTHERWISE PROVIDED FOR, CONCERNED WITH THE FUNCTIONING OF THE WING
    • E05Y2900/00—Application of doors, windows, wings or fittings thereof
    • E05Y2900/10—Application of doors, windows, wings or fittings thereof for buildings or parts thereof
    • E05Y2900/13—Application of doors, windows, wings or fittings thereof for buildings or parts thereof characterised by the type of wing
    • E05Y2900/132—Doors
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME RELATING TO HINGES OR OTHER SUSPENSION DEVICES FOR DOORS, WINDOWS OR WINGS AND DEVICES FOR MOVING WINGS INTO OPEN OR CLOSED POSITION, CHECKS FOR WINGS AND WING FITTINGS NOT OTHERWISE PROVIDED FOR, CONCERNED WITH THE FUNCTIONING OF THE WING
    • E05Y2900/00—Application of doors, windows, wings or fittings thereof
    • E05Y2900/10—Application of doors, windows, wings or fittings thereof for buildings or parts thereof
    • E05Y2900/13—Application of doors, windows, wings or fittings thereof for buildings or parts thereof characterised by the type of wing
    • E05Y2900/148—Windows

Definitions

  • the density of the finished sintered molded part depends on this essentially depends on the green density achieved, whereby different than when pressing ceramic powders the metal powder particles because of their different crystalline structure and the associated number of movable lattice construction errors undergo plastic deformation.
  • the particle geometry - also different from ceramic powders - is the lubricity of the individual with metallic powders Powder particles reduced against each other, so that even the loose Filling in the mold has a pore volume, which at Presses almost only when very high pressures are applied can be completely eliminated.
  • high pressures have high wear on the pressing tool during the compression process and also lead to increased sliding friction the finished green body in the press die, so that here also higher ejection forces with accordingly increased wear must be applied. High ejection forces however, pose a risk of undesirable local Post-compaction and cracking of the green compact in itself.
  • EP-A-0 375 627 Proposed method in which the metal powder to be pressed with one liquefied by a liquid solvent Lubricant is added.
  • a lubricant metal stearates, in particular lithium or zinc stearates as well as paraffins, waxes, natural or synthetic Fat derivatives proposed, for example, with organic Paraffinic solvents as a liquid solvent initially be liquefied.
  • the disadvantage of this method is on the one hand in that the dry metal powder with a two-component lubricant system, namely the stearates and have to be mixed with the solvent first, this premix must be largely homogeneous.
  • From EP 0 559 987 is a metallurgical powder composition known iron-based, which is an organic binder for the iron-based powder components and the alloy powder components contains. Contains to improve the pressing behavior the organic binder contains a proportion of polyalkylene oxide, which have a molecular weight of at least 7000 g / mol should, however, much higher molecular weights are preferred.
  • US 4,595,558 discloses a process for making molded Alloy products. To avoid in particular the separation of mixtures from the base metal with the Alloy metal is proposed as a process aid add, with a polyethylene glycol for this purpose Molecular weight above 200 g / mol is preferred. From the alloy mix with aids using a roller press Briquettes made, for example, in melted Aluminum are given, then a good solution of the Briquettes in the melt took place.
  • US 5 432 223 discloses a binder system for manufacture of segregation-free iron powder mixtures with an alloy metal comprising polyvinyl pyrrolidones and as plasticizers for example polyethylene glycol with molecular weights essentially below 10,000 g / mol. From these mixtures green bodies are produced, the green strengths have in an area that is approximately that of green bodies without the addition of polyvinylpyrrolidone and polyethylene glycol correspond.
  • EP 0 501 602 A2 discloses a method for faster removal a binder from powder mixtures for metal injection molding, in which the binder content at least 11% by weight, based on the amount of metal powder used, is.
  • the binder can, among others Ingredients contain polyethylene glycols.
  • the invention is based on the object described above Improve procedures.
  • This task is solved with a manufacturing process of sinterable metallic moldings from a metal powder, which is mixed with a pressing aid, the Pressing aids in an amount of up to 5% by weight, preferably below 1% by weight, based on the metal powder content, in the mixture is contained and at least partially components from the family of polyethylene glycols with a molecular weight contains between 3000 and 6500 g / mol, the Mixture poured into a mold and after compaction ejected under pressure as a pressed molded part from the mold becomes.
  • pressing aids at least some components from the family of polyethylene glycols contain, has surprisingly shown that to achieve high Density and high green strength much lower pressures than to be used with other pressing aids and that also for ejecting the pressed molded part from the Necessary forces are significantly reduced, so that the above-mentioned disadvantages of the known methods are avoided.
  • a special binder in the powder mix it is not necessary, because of the "lubrication” the moving relative to each other during the pressing process Powder particles already have a high density as well as a high one Strength of the green body due to the much higher "packing density" of powder particles and thus an increase in direct contacts between the metal particles in the powder can be.
  • Metal powder in the sense the invention refers to that for the production of the molded part intended powder mixture with all alloy and other surcharges, with the exception of pressing aids.
  • a special advantage of the family of polyethylene glycols selected pressing aids is that by an appropriate choice of molecular weight influence the pressing parameters can be taken, both in terms of the flow behavior when mixing and filling the shape, as well as the softening point and thus the temperature control and the material flow during Pressing operation.
  • Pressing aids proposed according to the invention with its softening point is between 40 ° C and 80 ° C, so that for example in series production which is continuously Press-setting tool temperature is usually sufficient for a perfect "flow" of the powder mixture to effect when filling into the mold as well as when pressing. Accordingly, this can be done with the pressing aid added metal powder to the mold at room temperature Fill.
  • Another advantage of the low softening temperature is in the fact that immediately after filling in first the pressing aids in the with the warmed up Form walls of metal powder in contact with their Obtain softening temperature, so that the subsequent Pressing the relative movements occurring on the tool walls between powder filling and pressing tool already "lubricated” and so the friction in these areas is reduced. At the subsequent full Pressurization will result in the entire powder filling the pressing pressure heated above the softening point, so that also the internal, as a result of the particle geometry of the metal powder caused relatively large relative movements in the metal powder filling by the effect of lubricating pressing aid can be facilitated.
  • the softening temperature of the pressing aid must be so can be set taking into account the working temperature the outer surfaces of the green compact during the pressing process not to be "moistened” by the pressing aid to a Avoid sticking of loose powder particles.
  • the pressing aid can be mixed into the metal powder "cold", i.e. H. at room temperature. Particularly useful is the warm mixing of the pressing aid with the metal powder, for example in a heated drum mixer with subsequent cooling with simultaneous agitation, whereby the temperature of the mixer is initially slightly higher than that intended softening temperature set for the pressing process becomes.
  • the mixing temperature is appropriate 50-100 ° C, preferably 85 ° C. After cooling down it is then a free-flowing powder mixture is available, which is a good one Manageability guaranteed when filling the mold.
  • the pressing aid has a liquid consistency
  • Solvents are particularly suitable for alcohols, such as ethanol, Isopropanol or benzyl alcohol, which after spraying quickly evaporate so that the obtained with the pressing aid staggered powder is "dry" and the required trickle or. Flowability is maintained when filling the mold remains.
  • the hydroxyl number of the pressing aid can be between 500 and 700, while the density can be between 0.9 and 1.25 g / cm 3 .
  • Polyethylene glycols are also useful different molecular weights.
  • Polyethylene glycols with different molecular weights can be deliberately a pressing aid that with respect Blending properties, softening point and Lubrication properties exactly to the compression method used can be coordinated.
  • the polyethylene glycol proposed here as a pressing aid can be characterized using the empirical formula given below: H - [- O-CH 2 -CH 2 -] n -OH
  • the increase in press densities to be achieved with polyethylene glycol do not primarily take place via a temperature-dependent Change in the physical properties of the metallic Powder, such as in the process described in EP-A-0 375 627, but essentially about improving the Lubrication behavior in the powder to be compacted itself, in particular but between the die wall and the powder filling with an appropriate temperature control on the pressing tools.
  • Another advantage of the pressing aid proposed here is that it is thermal before sintering is easier to eliminate, for example via diffusion processes, Escape via capillary forces, sublimation, evaporation or similar. This is what distinguishes the invention Pressing aids also through an environmentally friendly Disposal option, as it is through pyrolysis in water vapor and carbon dioxide can be broken down.
  • metal stearates As a lubricant to reduce friction between the die wall and powder particles on the one hand and between powder particles on the other hand, metal stearates have been used in particular Lithium or zinc stearates as well as paraffins, waxes, natural or synthetic fat derivatives used. at newer developments are becoming multi-component high temperature resistant (i.e. approx. 130 ° C here) lubricant that thus a reduction in the yield strength of the material to be pressed Cause metal and consequently lead to higher compression densities, as also described in EP-A-0 375 627.
  • a water-atomized iron powder was used for an experiment 2% copper and 0.6% carbon each used in powder form.
  • the curves show the dependence of the density from the pressure.
  • Curve 1 shows the result of the application as a reference curve the cold pressing process with a conventional one Lubricant in the form of an amide wax or micro wax, for example ethylene bisstearoylamide.
  • Curve 2 shows the result when using the hot pressing process according to the state of the art. Here there is already a clear improvement. in this connection however, the disadvantages described must be accepted become.
  • curve 3 shows the result in the application of the method according to the invention, which is even clearer Leads to an increase in the final density.
  • Table 1 shows the metal powder specified above containing 0.6% by weight of polyethylene glycol with a mol weight in the range of about 6000 g / mol, that cold, d. H. mixed at room temperature and also pressed has been.
  • the table shows what is practically proportional to the baling pressure Increase in green density and green strength.
  • Table 2 shows the result for a starting material shown with the same composition, but mixed warm but was cold pressed. Here shows up next to one Increase in green density a significant increase in green strength compared to the values for cold pressing one cold mixed powder.
  • Table 3 shows the values for a cold mixed powder, that is pressed warm.
  • the achievable values for the green density correspond to the above values, while the green strength shows a significant increase, what the interaction between the type of polyethylene glycol used with low molecular weight and temperature control shows when pressing.
  • the increase in green strength is probably due to the better Flow behavior of the pressing aid with the relative low molecular weight in the metal powder matrix below Pressure and temperature due to the fact that very homogeneous mixture of pressing aids and metal powder and secondly because of the thin already achieved during mixing "Lubricant film" that extends even further when hot pressed reduced, a very between the individual metal particles much higher frequency of direct contact between metallic Surfaces is given and so the one described above plastic deformation and entanglement of the metal powder particles can be achieved.
  • Table 5 shows the values for the metal powder as a reference reproduced, an amide wax mixed cold as a pressing aid and that was cold pressed.

Description

Bei der Herstellung von metallischen Formteilen im pulvermetallurgischen Verfahren besteht eine Schwierigkeit darin, die Formteile mit einer möglichst hohen Dichte herzustellen, da die metallischen Pulver zunächst in eine Preßmatrize eingefüllt werden und dann über ein ein- oder mehrachsiges Pressen mittels hydraulischer oder mechanischer Presseinrichtungen mit hohem Druck verdichtet werden müssen. Ein hierdurch gewonnener, allgemein als Grünling bezeichneter Formkörper wird anschließend in einem thermischen Verfahren meist unter Schutzatmosphäre gesintert, so daß sich ein festes und auch formgenaues metallisches Formteil ergibt.In the production of metallic moldings in powder metallurgy One difficulty is the procedure To produce molded parts with the highest possible density, because the metallic powders are first filled into a press die and then with single or multi-axis pressing by means of hydraulic or mechanical pressing devices must be compressed with high pressure. A hereby won is generally referred to as a green body then mostly in a thermal process Protective atmosphere sintered, so that there is a firm and also Form-fitting metallic molded part results.

Die Dichte des fertigen gesinterten Formteils hängt hierbei im wesentlichen von der erreichten Gründichte ab, wobei anders als beim Verpressen von keramischen Pulvern die Metallpulverpartikel aufgrund ihrer anderen kristallinen Struktur und der damit verbundenen Anzahl beweglicher Gitterbaufehler eine plastische Verformung erfahren. Aufgrund der Teilchengeometrie - ebenfalls anders als bei keramischen Pulvern - ist bei metallischen Pulvern die Gleitfähigkeit der einzelnen Pulverteilchen gegeneinander reduziert, so daß schon die lose Schüttung in der Preßform ein Porenvolumen aufweist, das beim Pressen nur unter Aufwendung sehr hoher Preßdrücke nahezu vollständig beseitigt werden kann. Hohe Preßdrücke haben jedoch einen hohen Verschleiß am Preßwerkzeug beim Verdichtungsvorgang zur Folge und führen auch zu einer erhöhten Ausstoßgleitreibung des fertigen Grünlings in der Preßmatrize, so daß hier ebenfalls auch höhere Ausstoßkräfte mit entsprechend erhöhtem Verschleiß aufzubringen sind. Hohe Ausstoßkräfte bergen jedoch die Gefahr einer unerwünschten lokalen Nachverdichtung und der Rißbildung des Grünlings in sich. The density of the finished sintered molded part depends on this essentially depends on the green density achieved, whereby different than when pressing ceramic powders the metal powder particles because of their different crystalline structure and the associated number of movable lattice construction errors undergo plastic deformation. Because of the particle geometry - also different from ceramic powders - is the lubricity of the individual with metallic powders Powder particles reduced against each other, so that even the loose Filling in the mold has a pore volume, which at Presses almost only when very high pressures are applied can be completely eliminated. However, high pressures have high wear on the pressing tool during the compression process and also lead to increased sliding friction the finished green body in the press die, so that here also higher ejection forces with accordingly increased wear must be applied. High ejection forces however, pose a risk of undesirable local Post-compaction and cracking of the green compact in itself.

Um diese Nachteile zu vermeiden, wurde in EP-A-0 375 627 ein Verfahren vorgeschlagen, bei dem das zu verpressende Metallpulver mit einem durch ein flüssiges Lösungsmittel verflüssigtes Schmiermittel versetzt wird. Als Schmiermittel werden hierzu Metallstearate, insbesondere Lithium- oder Zinkstearate sowie Paraffine, Wachse, natürliche oder synthetische Fettderivate vorgeschlagen, die beispielsweise mit organischen Paraffinlösungsmitteln als flüssigem Lösungsmittel zunächst verflüssigt werden. Der Nachteil dieses Verfahrens besteht zum einen darin, daß die trockenen Metallpulver mit einem zweikomponentigen Schmiermittelsystem, nämlich den Stearaten und dem Lösungsmittel zunächst vermischt werden müssen, wobei diese Vormischung weitgehend homogen sein muß. Ein weiterer Nachteil besteht darin, daß diese Pulvermischung vor dem Füllen der Preßform zunächst bis in den Bereich des Erweichungspunktes des verwendeten Schmiermittels relativ hoch vorerhitzt werden muß. Dadurch ist auch die Gefahr von Anbakkungen in den Zuführeinrichtungen zur Preßform gegeben. Nach Abschluß des Preßvorganges und dem Ausstoßen des Grünlings muß das Schmiermittel in einem gesonderten Vorgang abgedampft werden, bevor der Grünling dann auf die eigentliche Sintertemperatur aufgeheizt werden kann. Hierbei ist es nicht zu vermeiden, daß die Restanteile des Schmiermittels im Sinterkörper verbleiben, was je nach Einsatzzweck und je nach Art des verwendeten reinen oder legierten Metallpulvers ebenfalls zu Nachteilen führen kann.In order to avoid these disadvantages, EP-A-0 375 627 Proposed method in which the metal powder to be pressed with one liquefied by a liquid solvent Lubricant is added. As a lubricant metal stearates, in particular lithium or zinc stearates as well as paraffins, waxes, natural or synthetic Fat derivatives proposed, for example, with organic Paraffinic solvents as a liquid solvent initially be liquefied. The disadvantage of this method is on the one hand in that the dry metal powder with a two-component lubricant system, namely the stearates and have to be mixed with the solvent first, this premix must be largely homogeneous. Another The disadvantage is that this powder mixture before filling the mold up to the softening point of the lubricant used is relatively high must be preheated. This also creates the risk of tick marks given in the feeders to the mold. To Completion of the pressing process and the ejection of the green body the lubricant must be evaporated in a separate process before the green body reaches the actual sintering temperature can be heated. Here it is not too avoid the residual lubricant in the sintered body remain, which depending on the purpose and depending on the type of the pure or alloyed metal powder used as well can lead to disadvantages.

Aus EP 0 559 987 ist eine metallurgische Pulverzusammensetzung auf Eisenbasis bekannt, die ein organisches Bindemittel für die eisenbasierten Pulveranteile und die Legierungspulveranteile enthält. Zur Verbesserung des Preßverhaltens enthält das organische Bindemittel einen Anteil an Polyalkylenoxid, das ein Molekulargewicht von mindestens 7000 g/mol aufweisen soll, bevorzugt sind jedoch wesentlich höhere Molekulargewichte. From EP 0 559 987 is a metallurgical powder composition known iron-based, which is an organic binder for the iron-based powder components and the alloy powder components contains. Contains to improve the pressing behavior the organic binder contains a proportion of polyalkylene oxide, which have a molecular weight of at least 7000 g / mol should, however, much higher molecular weights are preferred.

US 4 595 558 offenbart ein Verfahren zur Herstellung von geformten Produkten aus Legierungen. Zur Vermeidung insbesondere der Separierung von Mischungen aus dem Basismetall mit dem Legierungsmetall wird vorgeschlagen, ein Verfahrenshilfsmittel zuzugeben, wobei hierfür ein Polyethylenglykol mit einem Molekulargewicht über 200 g/mol bevorzugt ist. Aus der Legierungsmischung mit Hilfsmittel werden mittels einer Rollpresse Briketts hergestellt, die beispielsweise in geschmolzenes Aluminium gegeben werden, wobei dann eine gute Lösung der Briketts in der Schmelze erfolgte.US 4,595,558 discloses a process for making molded Alloy products. To avoid in particular the separation of mixtures from the base metal with the Alloy metal is proposed as a process aid add, with a polyethylene glycol for this purpose Molecular weight above 200 g / mol is preferred. From the alloy mix with aids using a roller press Briquettes made, for example, in melted Aluminum are given, then a good solution of the Briquettes in the melt took place.

US 5 432 223 offenbart ein Bindemittelsystem zur Herstellung von segregationsfreien Eisenpulvermischungen mit einem Legierungsmetall umfassend Polyvinylpyrrolidone und als Plastifiziermittel beispielsweise Polyethylenglykol mit Molekulargewichten im wesentlichen unter 10.000 g/mol. Aus diesen Mischungen werden Grünkörper hergestellt, die Grünfestigkeiten in einem Bereich aufweisen, die in etwa derjenigen von Grünkörpern ohne Zusatz von Polyvinylpyrrolidon und Polyethylenglykol entsprechen.US 5 432 223 discloses a binder system for manufacture of segregation-free iron powder mixtures with an alloy metal comprising polyvinyl pyrrolidones and as plasticizers for example polyethylene glycol with molecular weights essentially below 10,000 g / mol. From these mixtures green bodies are produced, the green strengths have in an area that is approximately that of green bodies without the addition of polyvinylpyrrolidone and polyethylene glycol correspond.

EP 0 501 602 A2 offenbart ein Verfahren zur schnelleren Entfernung eines Bindemittels aus Pulvermischungen für das Metallspritzgießen, bei welchem der Bindemittelanteil mindestens 11 Gew.-%, bezogen auf die Menge an eingesetztem Metallpulver, beträgt. Das Bindemittel kann dabei neben weiteren Bestandteilen Polyethylenglykole enthalten.EP 0 501 602 A2 discloses a method for faster removal a binder from powder mixtures for metal injection molding, in which the binder content at least 11% by weight, based on the amount of metal powder used, is. The binder can, among others Ingredients contain polyethylene glycols.

Der Erfindung liegt die Aufgabe zugrunde, die vorstehend beschriebenen Verfahren zu verbessern. The invention is based on the object described above Improve procedures.

Gelöst wird diese Aufgabe mit einem Verfahren zur Herstellung von sinterbaren metallischen Formteilen aus einem Metallpulver, das mit einem Preßhilfsmittel versetzt ist, wobei das Preßhilfsmittel in einer Menge von bis zu 5 Gew.-%, vorzugsweise unter 1 Gew.-%, bezogen auf den Metallpulveranteil, in der Mischung enthalten ist und zumindest teilweise Komponenten aus der Familie der Polyethylenglykole mit einem Molekulargewicht zwischen 3000 und 6500 g/mol enthält, wobei die Mischung in eine Preßform eingefüllt und nach dem Verdichten unter Druck als gepreßtes Formteil aus der Preßform ausgestoßen wird. Die Verwendung von Preßhilfsmitteln, die zumindest teilweise Komponenten aus der Familie der Polyethylenglykole enthalten, hat überraschend gezeigt, daß zur Erzielung hoher Dichten und hoher Grünfestigkeiten sehr viel geringere Preßdrücke als bei anderen Preßhilfsmitteln aufzuwenden sind und daß auch die zum Ausstoßen des gepreßten Formteils aus der Preßform notwendigen Kräfte deutlich verringert sind, so daß die vorstehend aufgeführten Nachteile der vorbekannten Verfahren vermieden sind. Eines besonderen Binders in der Pulvermischung bedarf es nicht, da schon aufgrund der "Schmierung" der sich beim Preßvorgang relativ zueinander bewegenden Pulverteilchen bereits neben einer hohen Dichte auch eine hohe Festigkeit des Grünlings durch die sehr viel höhere "Pakkungsdichte" der Pulverteilchen und damit eine Erhöhung von direkten Kontakten zwischen den Metallteilchen im Pulver erzielt werden kann. Eine hohe Grünfestigkeit ist immer dann wünschenswert, wenn der Grünling vor dem Sintern noch einer Bearbeitung unterzogen werden soll. "Metallpulver" im Sinne der Erfindung bezeichnet die für die Herstellung des Formteils vorgesehene Pulvermischung mit allen Legierungs- und sonstigen Zuschlägen, ausgenommen Preßhilfsmittel.This task is solved with a manufacturing process of sinterable metallic moldings from a metal powder, which is mixed with a pressing aid, the Pressing aids in an amount of up to 5% by weight, preferably below 1% by weight, based on the metal powder content, in the mixture is contained and at least partially components from the family of polyethylene glycols with a molecular weight contains between 3000 and 6500 g / mol, the Mixture poured into a mold and after compaction ejected under pressure as a pressed molded part from the mold becomes. The use of pressing aids, at least some components from the family of polyethylene glycols contain, has surprisingly shown that to achieve high Density and high green strength much lower pressures than to be used with other pressing aids and that also for ejecting the pressed molded part from the Necessary forces are significantly reduced, so that the above-mentioned disadvantages of the known methods are avoided. A special binder in the powder mix it is not necessary, because of the "lubrication" the moving relative to each other during the pressing process Powder particles already have a high density as well as a high one Strength of the green body due to the much higher "packing density" of powder particles and thus an increase in direct contacts between the metal particles in the powder can be. A high green strength is always then desirable if the green body one more before sintering Processing to be subjected. "Metal powder" in the sense the invention refers to that for the production of the molded part intended powder mixture with all alloy and other surcharges, with the exception of pressing aids.

Ein besonderer Vorteil der aus der Familie der Polyethylenglykole ausgewählten Preßhilfsmittel besteht darin, daß durch eine entsprechende Auswahl des Molekulargewichtes Einfluß auf die Preßparameter genommen werden kann, und zwar sowohl hinsichtlich des Fließverhaltens beim Mischen und beim Füllen der Form, als auch hinsichtlich des Erweichungspunktes und damit der Temperaturführung und des Materialflusses beim Preßvorgang. Hierbei ist insbesondere vorteilhaft, wenn das erfindungsgemäß vorgeschlagene Preßhilfsmittel mit seinem Erweichungspunkt zwischen 40°C und 80°C liegt, so daß beispielsweise in der Serienfertigung die sich beim fortlaufenden Pressen einstellende Werkzeugtemperatur in der Regel ausreicht, um ein einwandfreies "Fließen" der Pulvermischung beim Einfüllen in die Preßform als auch beim Pressen zu bewirken. Dementsprechend läßt sich das mit dem Preßhilfsmittel versetzte Metallpulver mit Raumtemperatur in die Preßform einfüllen. Insbesondere in der Serienfertigung kann es zweckmäßig sein, das Preßwerkzeug entsprechend zu beheizen, um etwaige Unterbrechungen des Serienlaufs aufzufangen. Zweckmäßig ist eine geregelte Beheizung der Preßwerkzeuge auf etwa 55°C, so daß sowohl die Aufheizung durch die Reibungswärme als auch Abkühlungen durch Arbeitsunterbrechungen berücksichtigt werden und so konstante Preßbedingungen vorgebbar sind. Hierdurch wird die Handhabung des Metallpulvers erheblich vereinfacht, insbesondere das Füllverfahren, da mit "kaltem" Pulver, also mit Pulver mit Raumtemperatur gearbeitet werden kann. Anbackungen, Klumpenbildung oder dergl. können nicht auftreten, da die Erwärmung des mit dem Preßhilfsmittel versetzten Metallpulvers erst in der Preßform erfolgt. Bei extrem großvolumigen Teilen kann eine zusätzliche Pulvervorwärmung zweckmäßig sein.A special advantage of the family of polyethylene glycols selected pressing aids is that by an appropriate choice of molecular weight influence the pressing parameters can be taken, both in terms of the flow behavior when mixing and filling the shape, as well as the softening point and thus the temperature control and the material flow during Pressing operation. This is particularly advantageous if that Pressing aids proposed according to the invention with its softening point is between 40 ° C and 80 ° C, so that for example in series production which is continuously Press-setting tool temperature is usually sufficient for a perfect "flow" of the powder mixture to effect when filling into the mold as well as when pressing. Accordingly, this can be done with the pressing aid added metal powder to the mold at room temperature Fill. It can be particularly useful in series production be to heat the press tool accordingly, to any To catch interruptions in the series run. expedient is controlled heating of the pressing tools to about 55 ° C, so that both the heating by the frictional heat as well Cooling due to work breaks are taken into account and so constant pressing conditions can be specified. hereby the handling of the metal powder is considerably simplified, especially the filling process, because with "cold" powder, So you work with powder at room temperature can. Caking, clumping or the like cannot occur because the heating of the with the pressing aid Metal powder only takes place in the mold. At extreme Large-volume parts can require additional powder preheating be appropriate.

Der weitere Vorteil der niederigen Erweichungstemperatur besteht darin, daß unmittelbar nach dem Einfüllen zunächst einmal die Preßhilfsmittelanteile in den mit den aufgewärmten Formwandungen in Kontakt stehenden Metallpulvermengen ihre Erweichungstemperatur erhalten, so daß beim anschließenden Preßvorgang die an den Werkzeugwandungen auftretenden Relativbewegungen zwischen Pulverfüllung und Preßwerkzeug bereits "geschmiert" erfolgen und so die Reibung in diesen Bereichen herabgesetzt wird. Bei der anschließenden vollständigen Druckbeaufschlagung wird die gesamte Pulverfüllung infolge des Preßdruckes über der Erweichungspunkt hinaus erwärmt, so daß auch die internen, infolge der durch die Teilchengeometrie des Metallpulvers bedingten relativ großen Relativbewegungen in der Metallpulverfüllung durch die Wirkung des schmierenden Preßhilfsmittels erleichtert werden. Infolge der Verformung der Pulverteilchen und der dadurch bewirkten Erhöhung der Packungsdichte wird zudem ein Teil des dann in fließfähigem Zustand vorliegenden Preßhilfsmittels in den Randbereich verdrängt, so daß sich auch beim Ausstoßen des fertigen Grünlings eine erhebliche Reduzierung der Reibung zwischen dem Grünling und der Wandung der Preßmatrize ergibt. Die Erweichungstemperatur des Preßhilfsmittels muß also so eingestellt werden, daß unter Berücksichtigung der Arbeitstemperatur beim Preßvorgang die Außenflächen des Grünlings durch das Preßhilfsmittel nicht "angefeuchtet" werden, um ein Anhaften von losen Pulverteilchen zu vermeiden.Another advantage of the low softening temperature is in the fact that immediately after filling in first the pressing aids in the with the warmed up Form walls of metal powder in contact with their Obtain softening temperature, so that the subsequent Pressing the relative movements occurring on the tool walls between powder filling and pressing tool already "lubricated" and so the friction in these areas is reduced. At the subsequent full Pressurization will result in the entire powder filling the pressing pressure heated above the softening point, so that also the internal, as a result of the particle geometry of the metal powder caused relatively large relative movements in the metal powder filling by the effect of lubricating pressing aid can be facilitated. As a result of Deformation of the powder particles and the resulting increase the packing density also becomes part of the flowable state existing pressing aid in the Edge area displaced, so that even when ejecting the green bodies produce a significant reduction in friction between the green body and the wall of the press die. The softening temperature of the pressing aid must be so can be set taking into account the working temperature the outer surfaces of the green compact during the pressing process not to be "moistened" by the pressing aid to a Avoid sticking of loose powder particles.

Auch bei niedrigem Molekulargewicht ergeben sich keine Nachteile beim Mischen mit dem Metallpulver. Durch die Wahl des Preßhilfsmittels und/oder einer Mischung von Preßhilfsmitteln mit entsprechendem Molekulargewicht kann auf den Mischvorgang beim Einmischen in das Metallpulver und den Erweichungspunkt in gewissen Grenzen Einfluß genommen werden. Überraschend hat sich herausgestellt, daß Polyethylenglykole auch bei sehr niedrigen Molekulargewichten sich zum einen auch in geringeren Gewichtsanteilen mit Metallpulvern gleichmäßig mischen lassen und zum anderen ein gutes "Fließen" der Pulvermischung beim Füllen der Preßform und beim Verdichten erzielt wird.Even with a low molecular weight, there are no disadvantages when mixing with the metal powder. By choosing the Pressing aids and / or a mixture of pressing aids with appropriate molecular weight can affect the mixing process when mixing into the metal powder and the softening point be influenced within certain limits. Surprisingly it turned out that polyethylene glycols even at very low molecular weights also result in lower ones Mix parts by weight with metal powder evenly and on the other hand a good "flow" of the powder mixture is achieved when filling the mold and when compacting.

Das Einmischen des Preßhilfsmittels in das Metallpulver kann "kalt", d. h. bei Raumtemperatur erfolgen. Besonders zweckmäßig ist das warme Mischen des Preßhilfsmittels mit dem Metallpulver, beispielsweise in einem beheizten Trommelmischer mit anschließender Kühlung bei gleichzeitiger Agitation, wobei die Temperatur des Mischers zunächst etwas höher als die für das Preßverfahren vorgesehene Erweichungstemperatur eingestellt wird. Die Mischtemperatur beträgt zweckmäßig 50 - 100°C, vorzugsweise 85°C. Nach der Abkühlung steht dann eine rieselfähige Pulvermischung zur Verfügung, die eine gute Handhabbarkeit bei der Formfüllung gewährleistet.The pressing aid can be mixed into the metal powder "cold", i.e. H. at room temperature. Particularly useful is the warm mixing of the pressing aid with the metal powder, for example in a heated drum mixer with subsequent cooling with simultaneous agitation, whereby the temperature of the mixer is initially slightly higher than that intended softening temperature set for the pressing process becomes. The mixing temperature is appropriate 50-100 ° C, preferably 85 ° C. After cooling down it is then a free-flowing powder mixture is available, which is a good one Manageability guaranteed when filling the mold.

Bei flüssiger Konsistenz des Preßhilfsmittels ist es möglich, das Preßhilfsmittel noch über ein zusätzliches Lösemittel in seiner Viskosität zu reduzieren, so daß die Pulverteilchen in einem der Sprühtrocknung vergleichbaren Verfahren mit dem Preßhilfsmittel noch dünner beschichtet werden können. Als Lösungsmittel eignen sich besonders Alkohole, wie Ethanol, Isopropanol oder Benzylalkohol, die nach dem Sprühen schnell verdampfen, so daß das gewonnene, mit dem Preßhilfsmittel versetzte Pulver "trocken" ist und die geforderte Riesel-bzw. Fließfähigkeit beim Einfüllen in die Preßform erhalten bleibt.If the pressing aid has a liquid consistency, it is possible to the pressing aid in an additional solvent reduce its viscosity so that the powder particles in a process comparable to spray drying with the Pressing aids can be coated even thinner. As Solvents are particularly suitable for alcohols, such as ethanol, Isopropanol or benzyl alcohol, which after spraying quickly evaporate so that the obtained with the pressing aid staggered powder is "dry" and the required trickle or. Flowability is maintained when filling the mold remains.

Bei einem Anteil des Preßhilfsmittels in einer Menge von bis zu 5 Gew.-%, bezogen auf den Metallpulveranteil, in der Mischung wird mit Vorteil ausgenutzt, daß die Dichte des erfindungsgemäßen Preßhilfsmittels höher als die Dichte herkömmlicher Preßhilfsmittel ist und somit bei gleichem Gewichtsanteil eine geringere Raumfüllung seitens des Preßhilfsmittels und demzufolge eine höhere Raumfüllung durch das verdichtete Metallpulver eingestellt wird. Zweckmäßig ist ein Anteil an Preßhilfsmittel von höchstens 1 Gew.-%, bezogen auf das Metallpulver.With a proportion of the pressing aid in an amount of up to 5% by weight, based on the metal powder content, in the mixture is advantageously used that the density of the invention Pressing aid higher than the density of conventional Is pressing aid and thus with the same weight proportion less space filling on the part of the pressing aid and consequently a higher space filling through the condensed Metal powder is set. A share in is expedient Pressing aids of at most 1% by weight, based on the metal powder.

Die Hydroxylzahl des Preßhilfsmittels kann zwischen 500 bis 700 liegen, während die Dichte zwischen 0,9 bis 1,25 g/cm3 liegen kann.The hydroxyl number of the pressing aid can be between 500 and 700, while the density can be between 0.9 and 1.25 g / cm 3 .

Zweckmäßig sind auch Mischungen von Polyethylenglykolen mit unterschiedlichen Molakulargewichten. Durch die Mischung von Polyethylenglykolen mit unterschiedlichen Molekulargewicht läßt sich gezielt ein Preßhilfsmittel darstellen, das hinsichtlich Mischungseigenschaften, Erweichungspunkt und Schmiereigenschaften genau auf das verwendete Verdichtungsverfahren abgestimmt werden kann.Mixtures of polyethylene glycols are also useful different molecular weights. By mixing Polyethylene glycols with different molecular weights can be deliberately a pressing aid that with respect Blending properties, softening point and Lubrication properties exactly to the compression method used can be coordinated.

Das hier als Preßhilfsmittel vorgeschlagene Polyethylenglycol kann mit der nachstehend angegebenen Summenformel charakterisiert werden: H-[-O-CH2-CH2-]n-OH The polyethylene glycol proposed here as a pressing aid can be characterized using the empirical formula given below: H - [- O-CH 2 -CH 2 -] n -OH

Die mit Polyethylenglykol zu erzielende Erhöhung der Preßdichten erfolgen nicht vorrangig über eine temperaturabhängige Änderung der physikalischen Eigenschaften des metallischen Pulvers, wie bei dem in EP-A-0 375 627 beschriebenen Verfahren, sondern im wesentlichen über eine Verbesserung des Schmierverhaltens im zu verdichtenden Pulver selbst, insbesondere aber zwischen der Matrizenwand und der Pulverfüllung bei einer entsprechenden Temperaturführung an den Preßwerkzeugen. Ein weiterer Vorteil des hier vorgeschlagenen Preßhilfsmittels besteht darin, daß es vor dem Sintern thermisch einfacher zu eliminieren ist, beispielsweise über Diffusionsvorgänge, Entweichen über Kapillarkräfte, Sublimieren, Verdampfen oder ähnliches. Hierbei zeichnet sich das erfindungsgemäße Preßhilfsmittel auch durch eine umweltverträgliche Entsorgungsmöglichkeit aus, da es über eine Pyrolyse in Wasserdampf und Kohlendioxid zerlegt werden kann. The increase in press densities to be achieved with polyethylene glycol do not primarily take place via a temperature-dependent Change in the physical properties of the metallic Powder, such as in the process described in EP-A-0 375 627, but essentially about improving the Lubrication behavior in the powder to be compacted itself, in particular but between the die wall and the powder filling with an appropriate temperature control on the pressing tools. Another advantage of the pressing aid proposed here is that it is thermal before sintering is easier to eliminate, for example via diffusion processes, Escape via capillary forces, sublimation, evaporation or similar. This is what distinguishes the invention Pressing aids also through an environmentally friendly Disposal option, as it is through pyrolysis in water vapor and carbon dioxide can be broken down.

Als Schmiermittel zur Verminderung der Reibung zwischen Matrizenwand und Pulverpartikeln einerseits sowie zwischen Pulverpartikeln andererseits wurden bisher Metallstearate, insbesondere Lithium- oder Zinkstearate sowie Paraffine, Wachse, natürliche oder synthetische Fettderivate verwendet. Bei neueren Entwicklungen werden vielkomponentige hochtemperaturresistente (d. h. hier ca. 130°C) Schmiermittel verwendet, die somit eine Reduzierung der Streckgrenze des zu verpressenden Metalls bewirken und folglich zu höheren Preßdichten führen, wie auch in EP-A-0 375 627 beschrieben. Ein Vergleich der Verpreßbarkeit nach den unterschiedlichen Verfahren, konventionelles Pressen bei Raumtemperatur, sogenanntes Warmpressen, wie in EP-A-0 375 627 beschrieben, mit dem erfindungsgemäßen Verfahren ist in dem nachstehend Diagramm wiedergegeben.As a lubricant to reduce friction between the die wall and powder particles on the one hand and between powder particles on the other hand, metal stearates have been used in particular Lithium or zinc stearates as well as paraffins, waxes, natural or synthetic fat derivatives used. at newer developments are becoming multi-component high temperature resistant (i.e. approx. 130 ° C here) lubricant that thus a reduction in the yield strength of the material to be pressed Cause metal and consequently lead to higher compression densities, as also described in EP-A-0 375 627. A comparison of the Pressability according to the different processes, conventional Pressing at room temperature, so-called hot pressing, as described in EP-A-0 375 627, with the inventive The procedure is shown in the diagram below.

Für einen Versuch wurde ein wasserverdüstes Eisenpulver mit 2% Kupfer und 0,6% Kohlenstoff jeweils in Pulverform verwendet. Die Kurven zeigen schematisch die Abhängigkeit der Dichte vom Preßdruck.A water-atomized iron powder was used for an experiment 2% copper and 0.6% carbon each used in powder form. The curves show the dependence of the density from the pressure.

Die Kurve 1 zeigt als Referenzkurve das Ergebnis bei der Anwendung des Kaltpreßverfahrens mit einem herkömmlichen Schmiermittel in Form eines Amidwachses bzw. Mikrowachses, beispielsweise Ethylenbisstearoylamid.Curve 1 shows the result of the application as a reference curve the cold pressing process with a conventional one Lubricant in the form of an amide wax or micro wax, for example ethylene bisstearoylamide.

Die Kurve 2 zeigt das Ergebnis bei der Anwendung des Warmpreßverfahrens nach dem angegebenen Stand der Technik. Hier ist schon eine deutliche Verbesserung zu erkennen. Hierbei müssen jedoch die beschriebenen Nachteile in Kauf genommen werden.Curve 2 shows the result when using the hot pressing process according to the state of the art. Here there is already a clear improvement. in this connection however, the disadvantages described must be accepted become.

Die Kurve 3 zeigt schließlich das Ergebnis bei der Anwendung des erfindungsgemäßen Verfahrens, das noch zu einer deutlicheren Steigerung in der Enddichte führt. Finally, curve 3 shows the result in the application of the method according to the invention, which is even clearer Leads to an increase in the final density.

In den nachstehenden Tabellen sind die in Abhängigkeit vom Preßdruck erzielbaren Gründichten und Grünfestigkeiten dargestellt. Hierbei sind die Ergebnisse gegenübergestellt, die sich bei unterschiedlichen Mischverfahren für das mit Preßhilfsmittel versetzte Metallpulver und unterschiedlichen Preßdrücken ergeben.

Figure 00100001
The green densities and green strengths that can be achieved depending on the baling pressure are shown in the tables below. The results are compared here, which result from different mixing processes for the metal powder mixed with pressing aid and different pressing pressures.
Figure 00100001

Tabelle 1 zeigt hierbei für das vorstehend angegebene Metallpulver mit einem Gehalt von 0,6 Gewichts-% an Polyethylenglykol mit einem Mol-Gewicht im Bereich von etwa 6000 g/mol, das kalt, d. h. bei Raumtemperatur gemischt und auch verpreßt wurde. Die Tabelle zeigt ein zum Preßdruck praktisch proportionales Ansteigen der Gründichte und der Grünfestigkeit. Table 1 shows the metal powder specified above containing 0.6% by weight of polyethylene glycol with a mol weight in the range of about 6000 g / mol, that cold, d. H. mixed at room temperature and also pressed has been. The table shows what is practically proportional to the baling pressure Increase in green density and green strength.

In der Tabelle 2 ist das Ergebnis für ein Ausgangsmaterial mit gleicher Zusammensetzung dargestellt, das jedoch warm gemischt aber kalt verpreßt wurde. Hier zeigt sich neben einer Steigerung der Gründichte eine deutliche Steigerung der Grünfestigkeit gegenüber den Werten bei kaltem Verpressen eines kalt gemischten Pulvers. Durch das Mischen bei einer Temperatur im Bereich der oberen Grenze der Erweichungstemperatur des Preßhilfsmittels, oder auch etwas darüber, ergibt sich offensichtlich eine bessere Verteilung in der Pulvermatrix und damit ein dünnerer "Schmiermittelfilm", der die Gleitbewegungen der Pulverteilchen und damit die "Kontaktdichte" der Metallteilchen und ihre dadurch mögliche "Verkrallung" begünstigt.Table 2 shows the result for a starting material shown with the same composition, but mixed warm but was cold pressed. Here shows up next to one Increase in green density a significant increase in green strength compared to the values for cold pressing one cold mixed powder. By mixing at one temperature in the area of the upper limit of the softening temperature the pressing aid, or something above it, results obviously a better distribution in the powder matrix and thus a thinner "lubricant film", which the sliding movements the powder particles and thus the "contact density" of the Metal particles and their possible "clawing" favored.

Die Tabelle 3 zeigt die Werte für ein kalt gemischtes Pulver, das warm verpreßt wird. Die erzielbaren Werte für die Gründichte entsprechen den vorstehend genannten Werten, während die Grünfestigkeit eine deutliche Steigerung erkennen läßt, was die Wechselwirkung zwischen der Art des eingesetzten Polyethylenglykols mit niedrigem Molekulargewicht und der Temperaturführung beim Pressen erkennen läßt.Table 3 shows the values for a cold mixed powder, that is pressed warm. The achievable values for the green density correspond to the above values, while the green strength shows a significant increase, what the interaction between the type of polyethylene glycol used with low molecular weight and temperature control shows when pressing.

In Tabelle 4 ist dann für ein warm gemischtes Metallpulver, das warm verpreßt worden ist, ein weiterer Anstieg der Gründichte zu verzeichnen, wobei bei einem Preßdruck von 800 MPa nahezu die theoretisch größtmögliche Dichte nahe der Dichte eines massiven Eisens erreicht wird. Besonders auffällig ist jedoch hierbei der weitere Anstieg der Grünfestigkeit. Die Grünfestigkeit wurde durch einen sogenannten 3-Punkt-Biegeversuch bestimmt. Die angegebenen Werte bezeichnen jeweils die maximale spezifische Auflast, bei der dann ein Bruch des grünen Prüflings eintritt.In Table 4 is then for a warm mixed metal powder, that has been hot-pressed, a further increase in green density to be recorded, with a pressure of 800 MPa almost the theoretically greatest possible density close to the density massive iron is achieved. Is particularly striking however, the further increase in green strength. The Green strength was determined by a so-called 3-point bending test certainly. The specified values denote in each case the maximum specific load at which then a If the green specimen breaks.

Die aus den vorstehenden Tabellen abzulesende Verbesserung der Gründichte, insbesondere aber auch der Grünfestigkeit, dürfte auf die Verwendung eines Polyethylenglykols mit einem Molekulargewicht zwischen 3000 und 6500 g/mol zurückzuführen sein. Entscheidend ist hierbei die beim Warmmischen zu verzeichnende Steigerung der Grünfestigkeit, die darauf zurückzuführen sein dürfte, daß beim Warmmischvorgang die Eisenpulverteilchen, die Kupferteilchen und die Kohlenstoffteilchen mit einer sehr dünnen Schicht des Preßhilfsmittels überzogen werden. Dies ist schon daraus abzulesen, daß bei einem warm gemischten Pulver der angegebenen Zusammensetzung das einzumischende Kohlepulver nicht staubt und bei einer "Fingerprobe" im Vergleich zum kalt gemischten Pulver nicht am Finger haften bleibt. Eine Prüfung der Verteilung der pulverförmigen Legierungsteile Kupfer und Kohlenstoff ergab eine Homogenität, die der Homogenität eines diffusionslegierten Metallpulvers entspricht, als einem Metallpulver, bei dem zunächst das Eisenpulver und die pulverförmigen Legierungsbestandteile gemischt und die Mischung thermisch vorbehandelt wird, um die Legierungspulver an dem Eisenpulver anzulagern, so daß ein Entmischen vermieden wird. Erst danach erfolgt in einem weiteren Arbeitsschritt das Zumischen des Preßhilfsmittels.The improvement seen in the tables above green density, but especially green strength, is likely to use a polyethylene glycol with a Molecular weight between 3000 and 6500 g / mol can be attributed. The decisive factor here is the one recorded during hot mixing Increase in green strength due to this should be that during the warm mixing process the iron powder particles, the copper particles and the carbon particles with one very thin layer of the pressing aid are coated. This can be seen from the fact that with a warm mixed Powder of the specified composition to be mixed Charcoal powder not dusty and in a "finger test" do not stick to the finger compared to the cold mixed powder remains. An examination of the distribution of the powder Alloy parts copper and carbon resulted in homogeneity, that of the homogeneity of a diffusion alloy metal powder corresponds to a metal powder, in which the first Iron powder and the powdered alloy components mixed and the mixture is pretreated to heat the Alloy powder to accumulate on the iron powder, so that a Segregation is avoided. Only then does another take place Working step of adding the pressing aid.

Wie die Versuche zeigen, kann beim erfindungsgemäßen Verfahren auf die energieaufwendige thermische Vorbehandlung der Pulvermischung verzichtet werden, da es insbesondere beim Warmmischverfahren gelingt, die pulverförmigen Legierungsbestandteile über das Preßhilfsmittel an die Eisenteilchen unentmischbar mit guter Homogenität zu binden. Auch darin zeigt sich der Vorteil der Erfindung.As the experiments show, in the method according to the invention on the energy-intensive thermal pretreatment of the Powder mixture can be dispensed with, as it is especially useful for The powdery alloy components are successfully mixed cannot be separated from the iron particles via the pressing aid bind with good homogeneity. Also shows in it the advantage of the invention.

Die Steigerung der Grünfestigkeit ist wohl auf das bessere Fließverhalten des Preßhilfsmittels mit dem verhältnismäßig niedrigen Molekulargewicht in der Metallpulvermatrix unter Druck und Temperatur zurückzuführen, da zum einen durch die sehr homogene Mischung von Preßhilfsmittel und Metallpulver und zum anderen wegen des schon beim Mischen erzielten dünnen "Schmiermittelfilms", der sich beim Warmpressen noch weiter reduziert, zwischen den einzelnen Metallteilchen eine sehr viel höhere Häufigkeit von unmittelbarem Kontakt zwischen metallischen Oberflächen gegeben ist und so die eingangs beschriebene plastische Verformung und Verhakung der Metallpulverteilchen erzielt werden kann.The increase in green strength is probably due to the better Flow behavior of the pressing aid with the relative low molecular weight in the metal powder matrix below Pressure and temperature due to the fact that very homogeneous mixture of pressing aids and metal powder and secondly because of the thin already achieved during mixing "Lubricant film" that extends even further when hot pressed reduced, a very between the individual metal particles much higher frequency of direct contact between metallic Surfaces is given and so the one described above plastic deformation and entanglement of the metal powder particles can be achieved.

Gegenüber der Tabelle 2 etwas höhere Werte ergaben sich überraschenderweise auch für eine Preßhilfsmittelmischung aus dem Amidwachs und mit Anteil von etwa 40% eines Polyethylenglykols mit einem Molekulargewicht von über 6000 g/mol, die warm in das Metallpulver eingemischt wurde, das anschließend warm verpreßt wurde.Surprisingly, somewhat higher values were found compared to Table 2 also for a mixture of pressing aids from the Amide wax and with a share of about 40% of a polyethylene glycol with a molecular weight of over 6000 g / mol, which is warm was mixed into the metal powder, which was then warm was pressed.

In Tabelle 5 sind als Referenz die Werte für das Metallpulver wiedergegeben, dem als Preßhilfsmittel ein Amidwachs kalt zugemischt wurde und das kalt verpreßt wurde.Table 5 shows the values for the metal powder as a reference reproduced, an amide wax mixed cold as a pressing aid and that was cold pressed.

Claims (9)

  1. Method for producing sinterable, metallic shaped parts from a metal powder which is mixed with an auxiliary compacting agent, the auxiliary compacting agent being contained in the mixture in a quantity of up to 5% by weight, preferably under 1% by weight relative to the metal powder proportion, and containing at least partially components from the family of polyethylene glycols with a molecular weight between 3,000 and 6,500 g/mol, the mixture being filled into a compacting mould and being ejected from the compacting mould after compacting under pressure as a compacted shaped part.
  2. Method according to claim 1, characterised in that the auxiliary compacting agent has a softening point between 40°C and 80°C.
  3. Method according to one of the claims 1 or 2, characterised in that the auxiliary compacting agent has a hydroxyl number of 500 to 700.
  4. Method according to one of the claims 1 to 3, characterised in that the auxiliary compacting agent has a density of 0.9 to 1.25 g/cm3.
  5. Method according to one of the claims 1 to 4, characterised in that the metal powder mixed with the auxiliary compacting agent is filled into the compacting mould at a temperature below the softening point of the auxiliary compacting agent used so that softening of the auxiliary compacting agent is effected by the introduction of energy in the compacting mould, preferably during compacting (warm-compacting).
  6. Method according to one of the claims 1 to 5, characterised in that the metal powder mixed with the auxiliary compacting agent is filled into the compacting mould at a temperature below the softening point of the auxiliary compacting agent used and is compacted without the supply of energy during compacting (cold-compacting).
  7. Method according to one of the claims 1 to 6, characterised in that the auxiliary compacting agent is mixed into the metal powder at a temperature which is at least in the range of the softening point of the auxiliary compacting agent (warm-mixing).
  8. Mixture for producing sinterable, metallic shaped parts from a metal powder which is mixed with an auxiliary compacting agent, the auxiliary compacting agent being contained in the mixture in a quantity of up to 5% by weight, preferably below 1% by weight, relative to the metal powder proportion, and containing at least partially components from the family of polyethylene glycols with a molecular weight between 3,000 and 6,500 g/mol.
  9. Sinterable metallic shaped parts, produced according to the method according to one of the claims 1 to 7.
EP98964406A 1997-11-28 1998-11-18 Compacting auxiliary agent for producing sinterable shaped parts from a metal powder Expired - Lifetime EP0968068B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19752993 1997-11-28
DE19752993A DE19752993A1 (en) 1997-11-28 1997-11-28 Process for producing sinterable metallic molded parts from a metal powder
PCT/EP1998/007406 WO1999028069A1 (en) 1997-11-28 1998-11-18 Compacting auxiliary agent for producing sinterable shaped parts from a metal powder

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EP0968068A1 EP0968068A1 (en) 2000-01-05
EP0968068B1 true EP0968068B1 (en) 2002-03-27

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JP (1) JP3386078B2 (en)
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AT (1) ATE214988T1 (en)
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CA (1) CA2279275C (en)
DE (2) DE19752993A1 (en)
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EP3165302A1 (en) 2015-11-03 2017-05-10 Wachs-Chemie Elsteraue e.K. Lubricant on the basis of sugar cane waxes

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DE10111325C1 (en) * 2001-03-08 2002-10-02 Gkn Sinter Metals Gmbh Method for producing a sintered metallic component with at least one bore
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EP3165302A1 (en) 2015-11-03 2017-05-10 Wachs-Chemie Elsteraue e.K. Lubricant on the basis of sugar cane waxes

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CA2279275A1 (en) 1999-06-10
WO1999028069A1 (en) 1999-06-10
KR100341359B1 (en) 2002-06-22
TW434064B (en) 2001-05-16
AR009920A1 (en) 2000-05-03
DE19752993A1 (en) 1999-06-02
JP2000517004A (en) 2000-12-19
DE59803513D1 (en) 2002-05-02
CA2279275C (en) 2006-04-18
ES2173662T3 (en) 2002-10-16
KR20000070202A (en) 2000-11-25
BR9807116A (en) 2000-04-25
JP3386078B2 (en) 2003-03-10
ATE214988T1 (en) 2002-04-15
US6224823B1 (en) 2001-05-01
EP0968068A1 (en) 2000-01-05

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