EP1079950B1 - Sinter-active metal and alloy powders for powder metallurgy applications and methods for their production and their use - Google Patents

Sinter-active metal and alloy powders for powder metallurgy applications and methods for their production and their use Download PDF

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Publication number
EP1079950B1
EP1079950B1 EP99923562A EP99923562A EP1079950B1 EP 1079950 B1 EP1079950 B1 EP 1079950B1 EP 99923562 A EP99923562 A EP 99923562A EP 99923562 A EP99923562 A EP 99923562A EP 1079950 B1 EP1079950 B1 EP 1079950B1
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Prior art keywords
metal
carboxylic acid
precipitation
metal salt
aqueous
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German (de)
French (fr)
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EP1079950A1 (en
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Bernd Mende
Gerhard Gille
Benno Gries
Peter Aulich
Jörg MÜNCHOW
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HC Starck GmbH
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HC Starck 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
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/20—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
    • B22F9/22—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
    • 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 producing metal powders, consisting of one or more of the elements Fe, Ni, Co, Cu, Sn and possible Additions of Al, Cr, Mn, Mo and W.
  • Alloy powders have a variety of applications for the production of sintered materials by powder metallurgy.
  • the main feature of powder metallurgy is it that corresponding powdered alloy or metal powder is pressed and are then sintered at an elevated temperature.
  • This method is in introduced on an industrial scale for the production of complicated moldings that otherwise only produce with a high degree of elaborate finishing to let.
  • the sintering can be as solid phase sintering or to form a liquid phase, e.g. with hard or heavy metals.
  • a very important applications of alloy and pure metal powders are tools for Metal, stone and woodworking. In these cases, they are two-phase Materials, the hardness carriers (e.g.
  • the element cobalt plays a special role because it has some special properties as a metallic matrix in diamond and hard metal tools. Because it wets tungsten carbide and diamonds particularly well, it is traditionally preferred for both types of tools.
  • the use of cobalt for the metallic binder phase in composite materials based on tungsten carbide or diamond achieves particularly good adhesion of the hardness carrier in the metallic binder phase. It is important to note that in the case of cobalt, the tendency to form carbides of the Co3W3C type ("eta phases"), which lead to embrittlement in hard metals, is less pronounced than, for example, in the case of iron. Co also attacks diamonds less than, for example, iron, which easily forms Fe 3 C. For these technical reasons, cobalt is traditionally used in the carbide and diamond tool industry.
  • the production of hard metals is generally based on cobalt metal powders 0.8 to 2 ⁇ m FSSS (ASTM B330), which together with the Hard materials, pressing aids and a grinding fluid in air gates or ball mills, which contain carbide balls as grinding media, a mixed grinding be subjected.
  • the suspension obtained is then from the grinding media separated, spray dried, and the granules obtained pressed into molds.
  • the subsequent liquid phase sintering at temperatures above the melting point of the W-Co-C eutectic results in dense sintered bodies (hard metals).
  • a An important property of the hard metals produced in this way is their strength Porosity is weakened.
  • a porosity is called the microporosity
  • B porosity is the macroporosity represents.
  • cobalt metal powders are ductile and are used in the mixed grinding is not crushed, but plastically deformed or the existing ones Agglomerates disassembled. If the cobalt metal powder used sintered compactly, contain large agglomerates, they are deformed into the Spray granules transferred and result in the sintered hard metal A and B porosity, often associated with local enrichment of the binder phase.
  • Diamond tools as a second important application group contain as cutting or active grinding parts sintered parts (segments), which mainly consist of Diamonds embedded in a metallic binder phase, mainly cobalt, consist.
  • sintered parts which mainly consist of Diamonds embedded in a metallic binder phase, mainly cobalt, consist.
  • hard materials or other metal powders may also be used to adjust the wear behavior of the bond on the diamond and the added to machined materials.
  • segments Metal powder, diamonds and optionally hard material powder mixed, if necessary granulated and dense in hot presses at elevated pressure and temperature sintered.
  • the requirements placed on the binder metal powder in addition to the necessary chemical purity are: good compressibility, the highest possible sintering activity, one matched to the diamond and the medium to be processed Hardness, adjusted by the grain size and the tendency to coarsen the structure during sintering, as well as slight attack on the metastable at sintering temperature Diamonds (graphitization).
  • the porosity decreases with increasing sintering temperature, i.e. the density of the Sinter institutionss approaches its theoretical value. For strength reasons therefore the sintering temperature chosen as high as possible.
  • the hardness falls the metallic matrix above an optimal temperature, since it is too a coarsening of the structure comes.
  • at higher temperature leads to an increased attack on the diamond.
  • such binder powder should be preferred for segments, if possible low sintering temperatures already reach their theoretical density and can be easily compacted.
  • a disadvantage in the production of diamond tools using metal powders of the individual elements as well as of bronze powders is that the metallic Binding after sintering is very inhomogeneous, since the sintering temperature and time Homogenization is not enough. Also occur when using ferrous metal powders high pressing forces, which wear the pressing tools, and too low strength of the green compacts (e.g. edge breakouts). This too is attributed to the cubic, body-centered lattice type of iron, which has fewer sliding planes than the face-centered cubic types of cobalt and Nickel or copper metal powder. They also include the finer ones available Carbonyl iron powder high amounts of carbon, leading to loss of strength of the segment can lead. There are no atomized metal powders or alloys sufficient sintering activity so that at temperatures acceptable for diamonds sufficient compression has not yet taken place.
  • the object of the invention is metal and alloy powder containing at least one of the metals iron, copper, tin, cobalt or nickel that the named Meet the requirements for binder metals for hard metals and diamond tools, to provide.
  • the metal and alloy powders according to the invention can by doping with the elements Al, Cr, Mn, Mo and / or W in subordinate Amount modified and adapted to special requirements.
  • the invention relates to a method for producing the metal and Alloy powder according to claim 1.
  • the precipitation product is preferably included Washed water and dried.
  • the precipitation product is preferably reduced in a hydrogen-containing one Atmosphere at temperatures between 400 and 600 ° C.
  • the reduction can be in the indirectly heated rotary kiln or in the push-through furnace at low Cover the bed.
  • Other ways to do the reduction are readily known to the person skilled in the art, e.g. in the deck oven or in the Fluidized bed.
  • the calcination causes the precipitation product consisting of polycrystalline particles or agglomerates the gases released upon decomposition of the carboxylic acid residue are crushed by decrepitation is, so that for the subsequent gas phase reaction (reduction) larger surface is available and a finer end product is obtained.
  • calcination in an oxygen-containing atmosphere that a metal or alloy powder is formed, which is compared to the direct reduction has a significantly reduced porosity.
  • the carboxylic acids are aliphatic or aromatic, saturated or unsaturated Mono- or dicarboxylic acids, especially those with 1 to 8 carbon atoms, are suitable. Due to their reducing effect, formic acid, oxalic acid, acrylic acid and crotonic acid preferred, due to their availability in particular Formic and oxalic acid. Oxalic acid is particularly preferably used.
  • the surplus reducing carboxylic acids prevents the formation of Fe (III) ions that would cause problems with the precipitation.
  • the carboxylic acid is preferably in a 1.1- to 1.6-fold stoichiometric excess based on the metals used.
  • a 1,2- is particularly preferred 1.5 times excess.
  • the carboxylic acid solution used as a suspension that contains undissolved carboxylic acid suspended does not contain a depot dissolved carboxylic acid, from the carboxylic acid extracted by precipitation of the solution is replaced so that a high concentration during the entire precipitation reaction of carboxylic acid is maintained in the mother liquor.
  • the Concentration of dissolved carboxylic acid in the mother liquor at the end of the precipitation reaction still at least 20% of the saturation concentration of the carboxylic acid in Amount of water.
  • the concentration is particularly preferred of dissolved carboxylic acid in the mother liquor still 25 to 50% of the saturation concentration the carboxylic acid in water.
  • a chloride solution is preferably used as the metal salt solution.
  • concentration of the metal salt solution is about 1.6 to 2.5 mol per liter.
  • the metal salt solution preferably has a content of 10 to 90% by weight of iron based on the total metal content and at least one other of the elements Copper, tin, nickel or cobalt.
  • the content of is particularly preferably Iron in the metal salt solution at least 20 wt .-%, more preferably at least 25% by weight, very particularly preferably at least 50% by weight, but less than 80% by weight, very particularly preferably less than 60% by weight, in each case based on the total metal content.
  • the metal salt solutions more preferably contain 10 to 70% by weight, in particular preferably up to 45% by weight, cobalt based on the total metal content.
  • the nickel content the metal salt solution is preferably 0 to 50% by weight, in particular preferably up to 16% by weight.
  • Copper and / or tin can be used in amounts of up to 30% by weight, preferably up to 10 wt .-%, based on the total metal content, are used.
  • Particularly preferred embodiment of the method according to the invention follows the addition of the metal salt solution to the carboxylic acid suspension gradually in the Way that the content of dissolved carboxylic acid in the mother liquor during the Supply of the metal salt solution a value of 50% of the solubility of carboxylic acid not less than in water.
  • the addition of the is particularly preferred Metal salt solution so gradually that until the suspended carboxylic acid dissolves the concentration of dissolved carboxylic acid does not fall below 80% of the solubility in Water falls below.
  • the rate of addition of the metal salt solution to the Carboxylic acid suspension thus takes place in such a way that the withdrawal of carboxylic acid from the mother liquor including concentration reduction by dilution by the water supplied with the metal salt solution by the dissolution of not dissolved, suspended carboxylic acid is largely compensated.
  • the solubility of the oxalic acid which is preferably used is in water approx. 1 mol per liter of water (room temperature), corresponding to 126 g oxalic acid (2nd Molecules of crystal water).
  • the oxalic acid as an aqueous suspension the 2.3 to 4.5 moles of oxalic acid per liter of water contains.
  • This suspension contains approximately 1.3 to 3.5 moles of undissolved Oxalic acid per liter of water.
  • the content of oxalic acid in the mother liquor is said to be 20 to 55 g / l of water be.
  • the metal salt solution is added in this way gradually that the oxalic acid concentration in the mother liquor during the addition not less than 75 g, particularly preferably not less than 100 g per liter of mother liquor decreases.
  • a sufficiently high level of supersaturation is constantly achieved, which leads to nucleation, i.e. is sufficient to generate further precipitation particles.
  • This will on the one hand high nucleation rate, which leads to correspondingly small particle sizes and, on the other hand, due to the small amount present in the mother liquor Metal ion concentration an agglomeration of the particles by dissolving largely prevented.
  • the high carboxylic acid concentration preferred according to the invention during the precipitation also causes the precipitate to increase in relative levels
  • Metals have the same composition as the metal salt solution, i.e. the existence homogeneous precipitation product with regard to its composition and thus alloy metal powder arises.
  • Metal and alloy powders can be obtained by the process according to the invention be at least one of the elements iron, copper, tin, nickel or Contain cobalt and optionally by one or more of the elements Al, Cr, Mn, Mo, W can be doped in a minor amount, and the middle one Grain size according to ASTM
  • B330 (FSSS) of 0.5 to 5 microns, preferably below 3 microns.
  • the Alloy powders are characterized in that they are not produced by grinding Have fracture areas. You are with this immediately after the reduction Grain size available.
  • Preferred metal or alloy particles have a very low carbon content of less than 0.04% by weight, preferably less than 0.01% by weight. This is due to that carried out between precipitation and reduction Temperature treatment in an oxygen-containing atmosphere attributable to the existing organic carbon is removed after the precipitation.
  • preferred Metal or alloy powders also have an oxygen content of below 1% by weight, preferably less than 0.5% by weight.
  • the preferred composition the alloy powder corresponds to the preferred relative metal contents of the metal salt solutions used, as indicated above.
  • the available according to the invention Metal and alloy powders are extremely suitable as Binder metal for hard metals or diamond tools. They are also used for powder metallurgy Suitable for the production of components.
  • example 1 2 3 4 Amount of water oxalic acid suspension (1) 15.6 ) 7.8 5.9 3.9 Particle size of the mixed oxalate ( ⁇ m, FSSS) 25.7 21.0 11.5 7.6 Alloy metal powders: particle size ( ⁇ m, FSSS) 2.1 ) 1.73 0.72 0.7 physical density (g / cm 3 ) 6.49 7.51 7.53 7.53 bulk density (g / cm 3 ) 0.44 0.38 0.26 0.24 oxygen content (Wt .-%) 0.96 0.81 0.69 0.70
  • Sintered body Density (g / cm 3 ) 14.36 14.38 14.43 14.41 Vickers hardness HV 30 (kg / mm 2 ) 1785 1797 1814 1812 Porosity ASTM B 276 A04B02C00 A04B00C00 ⁇ A02B00C00 ⁇ A02B00C00 ⁇ A02B00C00
  • a hard metal test was carried out on this metal powder under identical conditions as in Examples 1 to 4.
  • the oxalate precipitation was carried out as in Example 5, but a Chloride solution with 42.7 g / l Co and 56.3 g / l Fe used.
  • the calcination in the muffle furnace was carried out at 250 ° C.
  • the three-step reduction below Hydrogen occurred at 520/550/570 ° C.
  • Example 2 Analogously to Example 1, an iron-cobalt-copper oxalate was precipitated, washed and dried, a metal chloride solution containing about 45 g / l Fe, 45 g / l Co and 10 g / l Cu was used.
  • the metal powders had the properties shown in Table 3.
  • Example 7 A Example 7 B Sintering temperature ° C HRB SD % TD HRB SD % TD 580 105.8 7.55 88.95 110.9 7.92 93.83 620 111.1 8.05 94.84 111.3 8.22 97.38 660 111.2 8.19 96.49 110.6 8.22 97.38 700 110.6 8.19 96.49 109.8 8.22 97.38 740 109.6 8.20 96.6 107.5 8.22 97.38 780 109.6 8.19 96.49 108.6 8.24 97.62 820 108.6 8.18 96.37 104.4 8.24 97.62 860 106.6 8.20 96,60 106.2 8.23 97.5

Abstract

A process is described for the production of metal powder and alloy powders containing at least one of the metals iron, copper, tin, cobalt or nickel, by mixing aqueous metal salt solutions with an aqueous carboxylic acid solution, separating the precipitation product from the mother liquor and reducing the precipitation product to the metal.

Description

Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung von Metallpulvern, bestehend aus einem oder mehreren der Elemente Fe, Ni, Co, Cu, Sn und möglichen Zusätzen von Al, Cr, Mn, Mo und W.The present invention relates to a method for producing metal powders, consisting of one or more of the elements Fe, Ni, Co, Cu, Sn and possible Additions of Al, Cr, Mn, Mo and W.

Legierungspulver haben vielfältige Anwendungen zur Herstellung von Sinterwerkstoffen auf pulvermetallurgischem Wege. Hauptmerkmal der Pulvermetallurgie ist es, daß entsprechende pulverförmige Legierungs- oder Metallpulver gepreßt und anschließend bei erhöhter Temperatur gesintert werden. Diese Methode ist in industriellem Maßstab zur Herstellung von komplizierten Formteilen eingeführt, die sich sonst nur mit einem hohen Maß an aufwendiger Endbearbeitung herstellen lassen. Die Sinterung kann als Festphasensinterung oder unter Bildung einer flüssigen Phase, wie z.B. bei den Hart- oder Schwermetallen, erfolgen. Eine sehr wichtige Anwendung von Legierungs- und reinen Metallpulvern sind Werkzeuge zur Metall-, Stein- und Holzbearbeitung. In diesen Fällen handelt es sich um zweiphasige Werkstoffe, wobei die Härteträger (z.B. Karbide oder Diamanten) in eine metallische Matrix eingebettet sind, welche für die erforderlichen Zähigkeitseigenschaften dieser Verbundwerkstoffe verantwortlich ist. Die so hergestellten Hartmetalle (im Falle von Karbiden oder Karbonitriden) oder Diamantwerkzeuge (im Fall von Diamanten) sind von erheblicher wirtschaftlicher Bedeutung.Alloy powders have a variety of applications for the production of sintered materials by powder metallurgy. The main feature of powder metallurgy is it that corresponding powdered alloy or metal powder is pressed and are then sintered at an elevated temperature. This method is in introduced on an industrial scale for the production of complicated moldings that otherwise only produce with a high degree of elaborate finishing to let. The sintering can be as solid phase sintering or to form a liquid phase, e.g. with hard or heavy metals. A very important applications of alloy and pure metal powders are tools for Metal, stone and woodworking. In these cases, they are two-phase Materials, the hardness carriers (e.g. carbides or diamonds) in a metallic Are embedded matrix, which for the required toughness properties of this Composites is responsible. The hard metals thus produced (in the case of Carbides or carbonitrides) or diamond tools (in the case of diamonds) of considerable economic importance.

Eine besondere Rolle spielt das Element Kobalt, da es als metallische Matrix in Diamant- und Hartmetallwerkzeugen einige besondere Eigenschaften hat. Da es Wolframkarbid und Diamanten besonders gut benetzt, wird es traditionell für beide Werkzeugarten vorzugsweise verwendet. Mittels der Verwendung von Kobalt für die metallische Binderphase in Verbundwerkstoffen auf Wolframkarbid- oder Diamantbasis wird eine besonders gute Haftung des Härteträgers in der metallischen Binderphase erreicht. Wichtig ist dabei die Tatsache, daß im Falle des Kobalts die Tendenz zur Bildung von Karbiden des Typs Co3W3C ("eta-Phasen"), die in Hartmetallen zur Versprödung führen, weniger ausgeprägt ist als z.B. beim Eisen. Auch greift Co Diamanten weniger an als z.B. Eisen, welches leicht Fe3C bildet. Aus diesen technischen Gründen wird Kobalt in der Hartmetall- und Diamantwerkzeugindustrie traditionell eingesetzt.The element cobalt plays a special role because it has some special properties as a metallic matrix in diamond and hard metal tools. Because it wets tungsten carbide and diamonds particularly well, it is traditionally preferred for both types of tools. The use of cobalt for the metallic binder phase in composite materials based on tungsten carbide or diamond achieves particularly good adhesion of the hardness carrier in the metallic binder phase. It is important to note that in the case of cobalt, the tendency to form carbides of the Co3W3C type ("eta phases"), which lead to embrittlement in hard metals, is less pronounced than, for example, in the case of iron. Co also attacks diamonds less than, for example, iron, which easily forms Fe 3 C. For these technical reasons, cobalt is traditionally used in the carbide and diamond tool industry.

Bei der Herstellung von Hartmetallen geht man im allgemeinen von Kobaltmetallpulvern 0,8 bis 2 µm FSSS (ASTM B330) aus, die zusammen mit den Hartstoffen, Preßhilfsmitteln und einer Mahlflüssigkeit in Atrittoren oder Kugelmühlen, welche Hartmetallkugeln als Mahlkörper enthalten, einer Mischmahlung unterzogen werden. Die erhaltene Suspension wird anschließend von den Mahlkörpern getrennt, sprühgetrocknet, und das erhaltene Granulat in Formen gepreßt. Die nachfolgende Flüssigphasen-Sinterung bei Temperaturen oberhalb des Schmelzpunktes des W-Co-C-Eutektikums ergibt dichte Sinterkörper (Hartmetalle). Eine wichtige Eigenschaft der so erzeugten Hartmetalle ist deren Festigkeit, die durch Porosität geschwächt wird. Industrielle Hartmetalle haben eine Porosität von besser oder gleich A02B00C00 gemäß ASTM B276 (oder DIN ISO 4505). Als A-Porosität bezeichnet man die Mikroporosität, während B-Porosität die Makroporosität darstellt. Kobaltmetallpulver sind im Gegensatz zu Hartstoffen duktil und werden bei der Mischmahlung nicht zerkleinert, sondern plastisch verformt oder die vorhandenen Agglomerate zerlegt. Falls die verwendeten Kobaltmetallpulver kompakt versinterte, große Agglomerate enthalten, werden diese in deformierter Form in das Sprühgranulat überführt und ergeben im gesinterten Hartmetall A- und B-Porosität, häufig vergesellschaftet mit lokaler Anreicherung der Binderphase.The production of hard metals is generally based on cobalt metal powders 0.8 to 2 µm FSSS (ASTM B330), which together with the Hard materials, pressing aids and a grinding fluid in air gates or ball mills, which contain carbide balls as grinding media, a mixed grinding be subjected. The suspension obtained is then from the grinding media separated, spray dried, and the granules obtained pressed into molds. The subsequent liquid phase sintering at temperatures above the melting point of the W-Co-C eutectic results in dense sintered bodies (hard metals). A An important property of the hard metals produced in this way is their strength Porosity is weakened. Industrial hard metals have a better porosity or equal to A02B00C00 according to ASTM B276 (or DIN ISO 4505). As an A porosity is called the microporosity, while B porosity is the macroporosity represents. In contrast to hard materials, cobalt metal powders are ductile and are used in the mixed grinding is not crushed, but plastically deformed or the existing ones Agglomerates disassembled. If the cobalt metal powder used sintered compactly, contain large agglomerates, they are deformed into the Spray granules transferred and result in the sintered hard metal A and B porosity, often associated with local enrichment of the binder phase.

Diamantwerkzeuge als zweite wichtige Anwendungsgruppe enthalten als schneidoder schleifaktive Bauteile Sinterteile (Segmente), welche hauptsächlich aus Diamanten, eingebettet in einer metallischen Binderphase, hauptsächlich Kobalt, bestehen. Daneben werden gegebenenfalls noch Hartstoffe oder andere Metallpulver zum Abstimmen des Verschleißverhaltens der Bindung auf den Diamanten und den zu bearbeitenden Werkstoffen zugesetzt. Zur Herstellung von Segmenten werden Metallpulver, Diamanten und gegebenenfalls Hartstoffpulver vermischt, gegebenenfalls granuliert und in Heißpressen bei erhöhtem Druck und Temperatur dicht gesintert. Die hierbei gestellten Anforderungen an die Bindermetallpulver neben der notwendigen chemischen Reinheit sind: gute Verdichtbarkeit, möglichst hohe Sinteraktivität, eine auf den Diamanten und das zu bearbeitende Medium abgestimmte Härte, eingestellt durch die Korngröße und die Tendenz zur Gefügevergröberung beim Sintern, sowie geringer Angriff auf den bei Sintertemperatur metastabilen Diamanten (Graphitisierung).Diamond tools as a second important application group contain as cutting or active grinding parts sintered parts (segments), which mainly consist of Diamonds embedded in a metallic binder phase, mainly cobalt, consist. In addition, hard materials or other metal powders may also be used to adjust the wear behavior of the bond on the diamond and the added to machined materials. For the production of segments Metal powder, diamonds and optionally hard material powder mixed, if necessary granulated and dense in hot presses at elevated pressure and temperature sintered. The requirements placed on the binder metal powder in addition to the necessary chemical purity are: good compressibility, the highest possible sintering activity, one matched to the diamond and the medium to be processed Hardness, adjusted by the grain size and the tendency to coarsen the structure during sintering, as well as slight attack on the metastable at sintering temperature Diamonds (graphitization).

Generell nimmt mit steigender Sintertemperatur die Porosität ab, d.h. die Dichte des Sinterstücks nähert sich seinem theoretischen Wert. Aus Gründen der Festigkeit wird daher die Sintertemperatur so hoch wie möglich gewählt. Andererseits fällt die Härte der metallischen Matrix oberhalb einer optimalen Temperatur wieder ab, da es zu einer Vergröberung des Gefüges kommt. Zusätzlich ist zu beachten, daß es bei höherer Temperatur zu einem verstärkten Angriff auf den Diamanten kommt. Aus diesen Gründen sind für Segmente solche Binderpulver vorzuziehen, die bei möglichst niedrigen Sintertemperaturen bereits ihre theoretische Dichte erreichen und sich leicht verdichten lassen.In general, the porosity decreases with increasing sintering temperature, i.e. the density of the Sinterstücks approaches its theoretical value. For strength reasons therefore the sintering temperature chosen as high as possible. On the other hand, the hardness falls the metallic matrix above an optimal temperature, since it is too a coarsening of the structure comes. In addition, it should be noted that at higher temperature leads to an increased attack on the diamond. Out For these reasons, such binder powder should be preferred for segments, if possible low sintering temperatures already reach their theoretical density and can be easily compacted.

Die nur begrenzte Verfügbarkeit von Kobalt, starke Preisschwankungen, Umweltaspekte und der Wunsch nach technischer Verbesserung haben zu zahlreichen Aktivitäten geführt, Kobalt in der Hartmetall- und Diamantwerkzeugindustrie zu ersetzen.The limited availability of cobalt, strong price fluctuations, environmental aspects and the desire for technical improvement have led to numerous activities led to replace cobalt in the carbide and diamond tool industry.

So gibt es bereits eine Reihe von Vorschlägen, als Bindermetall Kobalt zumindest teilweise durch Eisen und/oder Nickel oder deren Legierungen zu ersetzen (Metall, 40 (1986), 133 bis 140); Int. J. of Refractory Metals & Hard Materials 15 (1997), 139 bis 149).There are already a number of proposals to replace cobalt as a binder metal at least partially by iron and / or nickel or their alloys (Metall, 40 (1986), 133 to 140); Int. J. of Refractory Metals & Hard Materials 15 (1997), 139-149).

Nachteilig bei der Herstellung von Diamantwerkzeugen unter Einsatz von Metallpulvern der Einzelelemente sowie von Bronzepulvern ist, daß die metallische Bindung nach dem Sintern sehr inhomogen ist, da die Sintertemperatur und -zeit zur Homogenisierung nicht ausreichen. Außerdem treten bei der Verwendung von Eisenmetallpulvern hohe Preßkräfte auf, die die Preßwerkzeuge verschleißen, und zu niedrigen Festigkeiten der Grünlinge führen (z.B. Kantenausbrüche). Auch dies ist auf den kubisch-raumzentrierten Gittertyp des Eisens zurückzuführen, welcher weniger Gleitebenen besitzt als die kubisch-flächenzentrierten Typen der Kobalt- und Nickel- oder Kupfermetallpulver. Zusätzlich enthalten die verfügbaren feineren Carbonyl-Eisenpulver hohe Mengen an Kohlenstoff, welche zu Festigkeitsverlusten des Segmentes führen können. Verdüste Metallpulver oder Legierungen weisen keine ausreichende Sinteraktivität auf, so daß bei den für Diamanten vertretbaren Temperaturen noch keine ausreichende Verdichtung erfolgt.A disadvantage in the production of diamond tools using metal powders of the individual elements as well as of bronze powders is that the metallic Binding after sintering is very inhomogeneous, since the sintering temperature and time Homogenization is not enough. Also occur when using ferrous metal powders high pressing forces, which wear the pressing tools, and too low strength of the green compacts (e.g. edge breakouts). This too is attributed to the cubic, body-centered lattice type of iron, which has fewer sliding planes than the face-centered cubic types of cobalt and Nickel or copper metal powder. They also include the finer ones available Carbonyl iron powder high amounts of carbon, leading to loss of strength of the segment can lead. There are no atomized metal powders or alloys sufficient sintering activity so that at temperatures acceptable for diamonds sufficient compression has not yet taken place.

Bei der Herstellung von Hartmetallen unter Verwendung von Carbonyleisenpulvern gibt es Probleme mit der Binderverteilung (A- und/oder B-Porosität). Kompensiert werden kann dies durch eine intensivere Mahlung. Dies führt jedoch zu einer unerwünschten Verbreiterung der Korngrößenverteilung.In the production of hard metals using carbonyl iron powders there are problems with the binder distribution (A and / or B porosity). compensated this can be achieved through more intensive grinding. However, this leads to an undesirable one Broadening the grain size distribution.

Dementsprechend gibt es auch eine Reihe von Vorschlägen, metallische Legierungspulver durch Fällung, z.T. in Gegenwart von organischen Phasen, und anschließende Reduktion herzustellen (WO 92/18 656, WO 96/04 088, WO 97/21 844).Accordingly, there are also a number of proposals, metallic alloy powder by precipitation, partly in the presence of organic phases, and subsequent To produce reduction (WO 92/18 656, WO 96/04 088, WO 97/21 844).

Aufgabe der Erfindung ist es, Metall- und Legierungspulver, enthaltend mindestens eines der Metalle Eisen, Kupfer, Zinn, Kobalt oder Nickel, die die genannten Anforderungen an Bindermetalle fiir Hartmetalle und Diamantwerkzeuge erfüllen, zur Verfügung zu stellen. Die erfindungsgemäßen Metall- und Legierungspulver können durch Dotierungen mit den Elementen Al, Cr, Mn, Mo und/oder W in untergeordneter Menge modifiziert und an spezielle Anforderungen angepaßt werden.The object of the invention is metal and alloy powder containing at least one of the metals iron, copper, tin, cobalt or nickel that the named Meet the requirements for binder metals for hard metals and diamond tools, to provide. The metal and alloy powders according to the invention can by doping with the elements Al, Cr, Mn, Mo and / or W in subordinate Amount modified and adapted to special requirements.

Gegenstand der Erfindung ist ein Verfahren zur Herstellung der Metall- und Legierungspulver gemäβ Anspruch 1. The invention relates to a method for producing the metal and Alloy powder according to claim 1.

Vorzugsweise wird das Fällungsprodukt nach Abtrennung von der Mutterlauge mit Wasser gewaschen und getrocknet.After separation from the mother liquor, the precipitation product is preferably included Washed water and dried.

Die Reduktion des Fällungsproduktes erfolgt vorzugsweise in einer wasserstoffhaltigen Atmosphäre bei Temperaturen zwischen 400 und 600°C. Die Reduktion kann im indirekt beheizten Drehrohrofen oder im Durchschubofen bei geringer Bettüberdeckung erfolgen. Weitere Möglichkeiten zur Durchführung der Reduktion sind dem Fachmann ohne weiteres geläufig, wie z.B. im Etagenofen oder in der Wirbelschicht.The precipitation product is preferably reduced in a hydrogen-containing one Atmosphere at temperatures between 400 and 600 ° C. The reduction can be in the indirectly heated rotary kiln or in the push-through furnace at low Cover the bed. Other ways to do the reduction are readily known to the person skilled in the art, e.g. in the deck oven or in the Fluidized bed.

Nach einer bevorzugten Ausführungsform der Erfindung wird das getrocknete Fällungsprodukt vor der Reduktion in sauerstoffhaltiger Atmosphäre bei Temperaturen von 200 bis 1000°C, vorzugsweise zwischen 250 und 500°C kalziniert. Die Kalzination bewirkt einerseits, daß das aus polykristallinen Teilchen bzw. Agglomeraten bestehende Fällungsprodukt durch die bei Zersetzung des Carbonsäurerestes freigesetzten Gase durch Dekrepitation zerkleinert wird, so daß für die anschließende Gasphasenreaktion (Reduktion) eine größere Oberfläche zur Verfügung steht und ein feineres Endprodukt erhalten wird. Zum anderen wird durch die Kalzination in sauerstoffhaltiger Atmosphäre bewirkt, daß ein Metall- bzw. Legierungspulver entsteht, das gegenüber der Direktreduktion eine erheblich reduzierte Porosität aufweist. Bei der Überführung des (Misch)metallcarbonsäuresalzes zum Metall- bzw. Legierungspulver tritt eine erhebliche Volumenreduktion der Teilchen auf, die zum Einschluß von Poren führt. Durch den zwischengeschalteten Kalzinierungsschritt in sauerstoffhaltiger Atmosphäre wird das (Misch)-metallcarbonsäuresalz zunächst in das (Misch)metalloxid überführt und getempert, so daß eine Vorverdichtung unter Ausheilung von Gitterstörungen erfolgt. Bei der anschließenden Reduktion in wasserstoffhaltiger Atmosphäre ist demgemäß nur noch die Volumenschrumpfung vom Oxid zum Metall zu überwinden. Durch die zwischengeschaltete Kalzinationsstufc wird eine stufenweise Volumenschrumpfung erzielt, jeweils unter struktureller Stabilisierung der Kristalle nach jeder Schrumpfungsstufe.According to a preferred embodiment of the invention, the dried Precipitation product before reduction in an oxygen-containing atmosphere at temperatures calcined from 200 to 1000 ° C, preferably between 250 and 500 ° C. On the one hand, the calcination causes the precipitation product consisting of polycrystalline particles or agglomerates the gases released upon decomposition of the carboxylic acid residue are crushed by decrepitation is, so that for the subsequent gas phase reaction (reduction) larger surface is available and a finer end product is obtained. On the other hand, calcination in an oxygen-containing atmosphere that a metal or alloy powder is formed, which is compared to the direct reduction has a significantly reduced porosity. When transferring the (mixed) metal carboxylic acid salt a considerable volume reduction occurs with the metal or alloy powder of the particles that lead to the inclusion of pores. Through the intermediary The calcination step in an oxygen-containing atmosphere becomes the (mixed) metal carboxylic acid salt first transferred to the (mixed) metal oxide and annealed, see above that a pre-compression takes place with the healing of lattice defects. In the Subsequent reduction in a hydrogen-containing atmosphere is accordingly only to overcome volume shrinkage from oxide to metal. Through the Intermediate calcination step gradually shrinks in volume achieved, each with structural stabilization of the crystals after each Shrinkage stage.

Als Carbonsäuren sind aliphatische oder aromatische, gesättigte oder ungesättigte Mono- oder Dicarbonsäuren, insbesondere solche mit 1 bis 8 Kohlenstoffatomen, geeignet. Aufgrund ihrer reduzierenden Wirkung sind Ameisensäure, Oxalsäure, Acrylsäure und Crotonsäure bevorzugt, aufgrund ihrer Verfügbarkeit insbesondere Ameisen- und Oxalsäure. Besonders bevorzugt wird Oxalsäure eingesetzt. Der Überschuß reduzierender Carbonsäuren verhindert die Ausbildung von Fe(III)-Ionen, die zu Problemen bei der Fällung führen würde.The carboxylic acids are aliphatic or aromatic, saturated or unsaturated Mono- or dicarboxylic acids, especially those with 1 to 8 carbon atoms, are suitable. Due to their reducing effect, formic acid, oxalic acid, acrylic acid and crotonic acid preferred, due to their availability in particular Formic and oxalic acid. Oxalic acid is particularly preferably used. The surplus reducing carboxylic acids prevents the formation of Fe (III) ions that would cause problems with the precipitation.

Vorzugsweise wird die Carbonsäure mit 1,1- bis 1,6-fach stöchiometrischem Überschuß bezogen auf die Metalle eingesetzt. Insbesondere bevorzugt ist ein 1,2- bis 1,5-facher Überschuß.The carboxylic acid is preferably in a 1.1- to 1.6-fold stoichiometric excess based on the metals used. A 1,2- is particularly preferred 1.5 times excess.

Nach einer weiter bevorzugten Ausführungsform der Erfindung wird dic Carbonsäurelösung als Suspension eingesetzt, die ungelöste Carbonsäure suspendiert enthält. Die bevorzugt eingesetzte Carbonsäuresuspension enthält ein Depot an nicht gelöster Carbonsäure, aus dem durch Fällung der Lösung entzogene Carbonsäure ersetzt wird, so daß während der gesamten Fällungsreaktion eine hohe Konzentration an Carbonsäure in der Mutterlauge aufrechterhalten wird. Vorzugsweise soll die Konzentration an gelöster Carbonsäure in der Mutterlauge am Ende der Fällungsreaktion noch mindestens 20 % der Sättigungskonzentration der Carbonsäure in Wasser betragen. Besonders bevorzugt soll am Ende der Fällungsreaktion die Konzentration an gelöster Carbonsäure in der Mutterlauge noch 25 bis 50 % der Sättigungskonzentration der Carbonsäure in Wasser betragen.According to a further preferred embodiment of the invention, the carboxylic acid solution used as a suspension that contains undissolved carboxylic acid suspended. The preferred carboxylic acid suspension does not contain a depot dissolved carboxylic acid, from the carboxylic acid extracted by precipitation of the solution is replaced so that a high concentration during the entire precipitation reaction of carboxylic acid is maintained in the mother liquor. Preferably, the Concentration of dissolved carboxylic acid in the mother liquor at the end of the precipitation reaction still at least 20% of the saturation concentration of the carboxylic acid in Amount of water. At the end of the precipitation reaction, the concentration is particularly preferred of dissolved carboxylic acid in the mother liquor still 25 to 50% of the saturation concentration the carboxylic acid in water.

Als Metallsalzlösung wird vorzugsweise eine Chloridlösung eingesetzt. Vorzugsweise beträgt die Konzentration der Metallsalzlösung etwa 1,6 bis 2,5 Mol pro Liter. Vorzugsweise weist die Metallsalzlösung einen Gehalt von 10 bis 90 Gew.-% Eisen bezogen auf den Gesamtmetallgehalt und mindestens ein weiteres der Elemente Kupfer, Zinn, Nickel oder Kobalt auf. Insbesondere bevorzugt beträgt der Gehalt an Eisen in der Metallsalzlösung mindestens 20 Gew.-%, weiter bevorzugt mindestens 25 Gew.-%, ganz besonders bevorzugt mindestens 50 Gew.-%, jedoch weniger als 80 Gew.-%, ganz besonders bevorzugt weniger als 60 Gew.-%, jeweils bezogen auf den Gesamtmetallgehalt.A chloride solution is preferably used as the metal salt solution. Preferably the concentration of the metal salt solution is about 1.6 to 2.5 mol per liter. The metal salt solution preferably has a content of 10 to 90% by weight of iron based on the total metal content and at least one other of the elements Copper, tin, nickel or cobalt. The content of is particularly preferably Iron in the metal salt solution at least 20 wt .-%, more preferably at least 25% by weight, very particularly preferably at least 50% by weight, but less than 80% by weight, very particularly preferably less than 60% by weight, in each case based on the total metal content.

Weiter bevorzugt enthalten die Metallsalzlösungen 10 bis 70 Gew.-%, insbesondere bevorzugt bis 45 Gew.-%, Kobalt bezogen auf den Gesamtmetallgehalt. Der Nickelgehalt der Metallsalzlösung beträgt vorzugsweise 0 bis 50 Gew.-%, insbesondere bevorzugt bis 16 Gew.-%.The metal salt solutions more preferably contain 10 to 70% by weight, in particular preferably up to 45% by weight, cobalt based on the total metal content. The nickel content the metal salt solution is preferably 0 to 50% by weight, in particular preferably up to 16% by weight.

Kupfer und/oder Zinn können in Mengen von bis zu 30 Gew.-%, bevorzugt bis zu 10 Gew.-%, bezogen auf den Gesamtmetallgehalt, eingesetzt werden. Nach der besonders bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens folgt die Zugabe der Metallsalzlösung zur Carbonsäuresuspension allmählich in der Weise, daß der Gehalt an gelöster Carbonsäure in der Mutterlauge während der Zuführung der Metallsalzlösung einen Wert von 50 % der Löslichkeit von Carbonsäure in Wasser nicht unterschreitet. Insbesondere bevorzugt erfolgt die Zugabe der Metallsalzlösung derart allmählich, daß bis zur Auflösung der suspendierten Carbonsäure die Konzentration an gelöster Carbonsäure nicht unter 80 % der Löslichkeit in Wasser unterschritten wird. Die Zugabegeschwindigkeit der Metallsalzlösung zur Carbonsäuresuspension erfolgt also in der Weise, daß der Entzug von Carbonsäure aus der Mutterlauge einschließlich Konzentrationsherabsetzung durch Verdünnung durch das mit der Metallsalzlösung zugeführte Wasser durch die Auflösung von nicht gelöster, suspendierter Carbonsäure weitgehend kompensiert wird.Copper and / or tin can be used in amounts of up to 30% by weight, preferably up to 10 wt .-%, based on the total metal content, are used. After Particularly preferred embodiment of the method according to the invention follows the addition of the metal salt solution to the carboxylic acid suspension gradually in the Way that the content of dissolved carboxylic acid in the mother liquor during the Supply of the metal salt solution a value of 50% of the solubility of carboxylic acid not less than in water. The addition of the is particularly preferred Metal salt solution so gradually that until the suspended carboxylic acid dissolves the concentration of dissolved carboxylic acid does not fall below 80% of the solubility in Water falls below. The rate of addition of the metal salt solution to the Carboxylic acid suspension thus takes place in such a way that the withdrawal of carboxylic acid from the mother liquor including concentration reduction by dilution by the water supplied with the metal salt solution by the dissolution of not dissolved, suspended carboxylic acid is largely compensated.

In bezug auf die Fällung der Metallsalze besitzt eine konzentrierte Carbonsäurclösung die "Aktivität 1", eine nur halb konzentrierte Carbonsäurelösung die "Aktivität 0,5". Erfindungsgemäß bevorzugt soll demgemäß die Aktivität der Muttcrlaugc während der Zugabe der Metallsalzlösung nicht unter 0,8 fallen. Concerning the precipitation of the metal salts has a concentrated carboxylic acid solution the "Activity 1", a only half-concentrated carboxylic acid solution "Activity 0.5". The activity of the mother liquor should accordingly be preferred according to the invention do not fall below 0.8 during the addition of the metal salt solution.

Beispielsweise beträgt die Löslichkeit der bevorzugt eingesetzten Oxalsäure in Wasser ca. 1 Mol pro Liter Wasser (Raumtemperatur), entsprechend 126 g Oxalsäure (2 Moleküle Kristallwasser). Nach dem erfindungsgemäßen bevorzugten Verfahren soll die Oxalsäure als wäßrige Suspension, die 2,3 bis 4,5 Mol Oxalsäure pro Liter Wasser enthält, vorgelegt werden. Diese Suspension enthält ca. 1,3 bis 3,5 Mol ungelöste Oxalsäure pro Liter Wasser. Nach Einleitung der Metallsalzlösung und beendeter Fällung soll der Gehalt an Oxalsäure in der Mutterlauge noch 20 bis 55 g/l Wasser betragen. Während der Einleitung der Metallsalzlösung in die Oxalsäuresuspension wird die zur Fällung verbrauchte Oxalsäure ständig durch Auflösung suspendierter Oxalsäure ersetzt. Zur Homogenisierung der Mutterlauge wird diese ständig gerührt. Nach der bevorzugten Ausführungsform erfolgt die Zugabe der Metallsalzlösung derart allmählich, daß die Oxalsäurekonzentration in der Mutterlauge während der Zugabe nicht unter 75 g, besonders bevorzugt nicht unter 100 g pro Liter Mutterlauge absinkt. Dadurch wird bewirkt, daß während der Zugabe der Metallsalzlösung ständig eine ausreichend hohe Übersättigung erzielt wird, die zur Keimbildung, d.h. zur Erzeugung weiterer Fällungspartikel ausreicht. Hierdurch wird einerseits eine hohe Keimbildungsrate, die zu entsprechend kleinen Partikelgrößen führt, gewährleistet und andererseits aufgrund der geringen, in der Mutterlauge vorhandenen Metallionenkonzentration eine Agglomeration der Teilchen durch Anlösen weitgehend verhindert.For example, the solubility of the oxalic acid which is preferably used is in water approx. 1 mol per liter of water (room temperature), corresponding to 126 g oxalic acid (2nd Molecules of crystal water). According to the preferred method according to the invention the oxalic acid as an aqueous suspension, the 2.3 to 4.5 moles of oxalic acid per liter of water contains. This suspension contains approximately 1.3 to 3.5 moles of undissolved Oxalic acid per liter of water. After introducing the metal salt solution and finished The content of oxalic acid in the mother liquor is said to be 20 to 55 g / l of water be. During the introduction of the metal salt solution into the oxalic acid suspension the oxalic acid consumed for the precipitation is constantly suspended by dissolution Oxalic acid replaced. The mother liquor is constantly stirred to homogenize it. According to the preferred embodiment, the metal salt solution is added in this way gradually that the oxalic acid concentration in the mother liquor during the addition not less than 75 g, particularly preferably not less than 100 g per liter of mother liquor decreases. This causes during the addition of the metal salt solution A sufficiently high level of supersaturation is constantly achieved, which leads to nucleation, i.e. is sufficient to generate further precipitation particles. This will on the one hand high nucleation rate, which leads to correspondingly small particle sizes and, on the other hand, due to the small amount present in the mother liquor Metal ion concentration an agglomeration of the particles by dissolving largely prevented.

Die erfindungsgemäß bevorzugt hohe Carbonsäurekonzentration während der Fällung bewirkt ferner, daß das Fällungsprodukt hinsichtlich der relativen Gehalte an Metallen dieselbe Zusammensetzung aufweist wie die Metallsalzlösung, d.h. daß ein bezüglich seiner Zusammensetzung homogenes Fällungsprodukt und damit Legierungsmetallpulver entsteht.The high carboxylic acid concentration preferred according to the invention during the precipitation also causes the precipitate to increase in relative levels Metals have the same composition as the metal salt solution, i.e. the existence homogeneous precipitation product with regard to its composition and thus alloy metal powder arises.

Nach dem erfindungsgemäßen Verfahren können Metall- und Legierungspulver erhalten werden, die mindestens eines der Elemente Eisen, Kupfer, Zinn, Nickel oder Kobalt enthalten und gegebenenfalls durch eines oder mehrere der Elemente Al, Cr, Mn, Mo, W in untergeordneter Menge dotiert sein können, und die eine mittlere Korngröße nach ASTM Metal and alloy powders can be obtained by the process according to the invention be at least one of the elements iron, copper, tin, nickel or Contain cobalt and optionally by one or more of the elements Al, Cr, Mn, Mo, W can be doped in a minor amount, and the middle one Grain size according to ASTM

B330 (FSSS) von 0,5 bis 5 µ, vorzugsweise unterhalb 3 µm aufweisen. Die Legierungspulver sind dadurch gekennzeichnet, daß sie keine durch Mahlung erzeugten Bruchflächen aufweisen. Sie sind unmittelbar nach der Reduktion mit dieser Korngröße erhältlich. Bevorzugte Metall- bzw. Legierungsteilchen weisen einen sehr geringen Kohlenstoffgehalt von weniger als 0,04 Gew.-%, vorzugsweise weniger als 0,01 Gew.-%, auf. Dies ist auf die zwischen Fällung und Reduktion durchgeführte Temperaturbehandlung in sauerstoffhaltiger Atmosphäre zurückzuführen, bei der der nach der Fällung vorhandene organische Kohlenstoff entfernt wird. Bevorzugte Metall- bzw. Legierungspulver weisen ferner einen Sauerstoffgehalt von unter 1 Gew.-%, vorzugsweise weniger als 0,5 Gew.-%, auf. Die bevorzugte Zusammensetzung der Legierungspulver entspricht den bevorzugten relativen Metallgehalten der eingesetzten Metallsalzlösungen, wie oben angegeben. Die erfindungsgemäß erhältlichen Metall- und Legierungspulver sind in hervorragender Weise geeignet als Bindermetall fiir Hartmetalle oder Diamantwerkzeuge. Ferner sind sie zur pulvermetallurgischen Herstellung von Bauteilen geeignet. B330 (FSSS) of 0.5 to 5 microns, preferably below 3 microns. The Alloy powders are characterized in that they are not produced by grinding Have fracture areas. You are with this immediately after the reduction Grain size available. Preferred metal or alloy particles have a very low carbon content of less than 0.04% by weight, preferably less than 0.01% by weight. This is due to that carried out between precipitation and reduction Temperature treatment in an oxygen-containing atmosphere attributable to the existing organic carbon is removed after the precipitation. preferred Metal or alloy powders also have an oxygen content of below 1% by weight, preferably less than 0.5% by weight. The preferred composition the alloy powder corresponds to the preferred relative metal contents of the metal salt solutions used, as indicated above. The available according to the invention Metal and alloy powders are extremely suitable as Binder metal for hard metals or diamond tools. They are also used for powder metallurgy Suitable for the production of components.

Die Erfindung wird nachfolgend anhand der beigefügten Beispiele 1 bis 7 näher erläutert. The invention will now be described with reference to the accompanying Examples 1 to 7 explained.

Beispiele 1 bis 4Examples 1 to 4

Jeweils 6,3 l einer Metallchloridlösung, enthaltend 75 g/l Fe, 15 g/l Ni und 10 g/l Co, wurden unter Rühren in eine Suspension von 1954 g Oxalsäure (die 1,4-fache stöchiometrische Menge bezogen auf die Metallsalze) in der in Tabelle 1 angegebenen Menge Wasser allmählich eindosiert. Nach beendeter Fällung wurde noch 30 Minuten gerührt, anschließend das Präzipitat abfiltriert und mit Wasser gewaschen. Das Oxalat wurde bei 105°C bis zur Gewichtskonstanz getrocknet. Die Teilchengrößen (FSSS) des getrockneten Mischoxalates sind in Tabelle 1 angegeben. Das Mischoxalat wurde anschließend im Muffelofen 3 Stunden bei 300°C kalziniert und danach im Durchschubofen bei 500°C unter Wasserstoff zum Legierungsmetallpulver reduziert.6.3 l each of a metal chloride solution containing 75 g / l Fe, 15 g / l Ni and 10 g / l Co, were stirred into a suspension of 1954 g of oxalic acid (1.4 times stoichiometric amount based on the metal salts) in that given in Table 1 Gradually add a lot of water. After the precipitation had ended, 30 Stirred for minutes, then the precipitate was filtered off and washed with water. The oxalate was dried at 105 ° C. to constant weight. The particle sizes (FSSS) of the dried mixed oxalate are given in Table 1. The Mixed oxalate was then calcined in the muffle furnace for 3 hours at 300 ° C. and then in a push-through furnace at 500 ° C under hydrogen to the alloy metal powder reduced.

Je 27 g des Mischmetallpulvers wurden mit 273 g WC (Sorte DS80 mit 0,15 % VC, Hersteller HCSt, Goslar) unter Zuschlag von 0,3 g Ruß im Attritor unter Hexan vermahlen. Nach Abtrennen der Mahlkugeln und Trocknung des Mahlgutes wurde ein Grünkörper hergestellt und wie folgt mit einem Preßdruck von 1500 kg/cm2 gesintert: 20°C/min auf 1100°C, 60 min Halten bei dieser Temperatur, weiter Aufheizen mit einer Rate von 20°C/min auf 1400°C, 45 min Halten bei dieser Tempcratur, Abkühlung auf 1100°C, 60 min Halten bei dieser Temperatur und Abkühlung auf Raumtemperatur. Der Sinterkörper wies die in Tabelle 1 angegebenen Eigenschaften auf. Beispiel 1 2 3 4 Wassermenge Oxalsäuresuspension (1) 15,6) 7,8 5,9 3,9 Teilchengröße des Mischoxalates (µm, FSSS) 25,7 21,0 11,5 7,6 Legierungsmetallpulver: Teilchengröße
(µm, FSSS) 2,1) 1,73 0,72 0,7 physikalische Dichte
(g/cm3) 6,49 7,51 7,53 7,53 Fülldichte
(g/cm3) 0,44 0,38 0,26 0,24 Sauerstoffgehalt
(Gew.-%) 0,96 0,81 0,69 0,70 Sinterkörper: Dichte (g/cm3) 14,36 14,38 14,43 14,41 Vickershärte HV30
(kg/mm2) 1785 1797 1814 1812 Porosität ASTM B 276 A04B02C00 A04B00C00 <A02B00C00 <A02B00C00 27 g of the mixed metal powder were ground with 273 g of WC (grade DS80 with 0.15% VC, manufacturer HCSt, Goslar) with the addition of 0.3 g of soot in the attritor under hexane. After the grinding balls had been separated off and the ground material had been dried, a green body was produced and sintered as follows with a pressing pressure of 1500 kg / cm 2 : 20 ° C./min to 1100 ° C., holding at this temperature for 60 minutes, further heating at a rate of 20 ° C / min to 1400 ° C, 45 min hold at this temperature, cooling to 1100 ° C, 60 min hold at this temperature and cooling to room temperature. The sintered body had the properties given in Table 1. example 1 2 3 4 Amount of water oxalic acid suspension (1) 15.6 ) 7.8 5.9 3.9 Particle size of the mixed oxalate (µm, FSSS) 25.7 21.0 11.5 7.6 Alloy metal powders: particle size
(µm, FSSS) 2.1 ) 1.73 0.72 0.7 physical density
(g / cm 3 ) 6.49 7.51 7.53 7.53 bulk density
(g / cm 3 ) 0.44 0.38 0.26 0.24 oxygen content
(Wt .-%) 0.96 0.81 0.69 0.70 Sintered body: Density (g / cm 3 ) 14.36 14.38 14.43 14.41 Vickers hardness HV 30
(kg / mm 2 ) 1785 1797 1814 1812 Porosity ASTM B 276 A04B02C00 A04B00C00 <A02B00C00 <A02B00C00

Beispiel 5Example 5

Es wurden 39 l einer Metallchloridlösung mit 50 g/l Fe, 42,3 g/l Co und 7,7 g/l Ni bei Raumtemperatur unter ständigem Rühren über eine Zeit von 30 min in eine Suspension aus 12,877 kg Oxalsäure in 45 Wasser eindosiert und anschließend weitere 60 min gerührt. Danach wurde filtriert, gewaschen und das Oxalat bei 110°C bis zur Gewichtskonstanz getrocknet. Das Oxalat wurde im Muffelofen 3 h bei 300°C kalziniert und das so produzierte Oxid nachfolgend im Durchschubofen in 3 aufeinanderfolgenden Heizzonen bei 480/500/530°C in insgesamt 130 min unter Wasserstoff (Taupunkt 10°C) zum Metallpulver reduziert. Am Metallpulver wurden ein FSSS-Wert von 0,71 µm, eine physikalische Dichte von 7,76 g/cm3 und eine Fülldichte von 0,24 g/cm3 gemessen; der Gehalt an Sauerstoff wurde mit 0,71 % bestimmt.39 l of a metal chloride solution with 50 g / l Fe, 42.3 g / l Co and 7.7 g / l Ni were metered in at room temperature with constant stirring over a period of 30 min into a suspension of 12.877 kg oxalic acid in 45 water and then stirred for a further 60 min. It was then filtered, washed and the oxalate dried at 110 ° C. to constant weight. The oxalate was calcined in the muffle furnace at 300 ° C for 3 h and the oxide thus produced was subsequently reduced to metal powder in a row in three successive heating zones at 480/500/530 ° C in 130 min under hydrogen (dew point 10 ° C). An FSSS value of 0.71 μm, a physical density of 7.76 g / cm 3 and a bulk density of 0.24 g / cm 3 were measured on the metal powder; the oxygen content was determined to be 0.71%.

Mit diesem Metallpulver wurde unter identischen Bedingungen wie in Beispielen 1 bis 4 ein Hartmetalltest durchgeführt. Am Testkörper wurden eine Dichte von 14,54 g/cm3, eine Vickershärte HV30 = 1817 kg/mm2 und eine Porosität <A02B00C00 nach ASTM B276 (unter dem Lichtmikroskop bei 200-facher Vergrößerung keine sichtbare Mikroporosität) gemessen.A hard metal test was carried out on this metal powder under identical conditions as in Examples 1 to 4. A density of 14.54 g / cm 3 , a Vickers hardness HV 30 = 1817 kg / mm 2 and a porosity <A02B00C00 according to ASTM B276 (no visible microporosity under a light microscope at 200 × magnification) were measured on the test body.

Beispiel 6Example 6

Die Oxalatfällung wurde wie in Beispiel 5 durchgeführt, jedoch wurde eine Chloridlösung mit 42,7 g/l Co und 56,3 g/l Fe eingesetzt.The oxalate precipitation was carried out as in Example 5, but a Chloride solution with 42.7 g / l Co and 56.3 g / l Fe used.

Die Kalzination im Muffelofen erfolgte bei 250°C. Die dreistufige Reduktion unter Wasserstoff erfolgte bei 520/550/570°C.The calcination in the muffle furnace was carried out at 250 ° C. The three-step reduction below Hydrogen occurred at 520/550/570 ° C.

Je 25 g dieses Fe-Co-Legierungspulvers wurden in einer Graphitmatrize im Vakuum (Heißpresse der Fa. Dr. Fritsch, Typ TSP) bei einem Preßdruck von 35 MPa über eine Preßzeit von 3 min bei unterschiedlicher Temperatur gesintert. 25 g each of this Fe-Co alloy powder were in a graphite matrix in a vacuum (Hot press from Dr. Fritsch, type TSP) at a pressure of 35 MPa a sintering time of 3 min at different temperatures.

Es wurden die in Tabelle 2 dargestellten Ergebnisse erzielt. Sintertemperatur °C Härte
Rockwell B Sinterdichte
g/cm3 % der theor.
Dichte 580 116,9 7,87 93,98 620 116,3 8,07 96,37 660 113,5 8,15 97,32 700 109,4 8,16 97,44 740 109,5 8,16 97,44 780 110,1 8,11 96,84 820 109,4 8,16 97,44 860 109,7 8,10 96,72 The results shown in Table 2 were achieved. Sintering temperature ° C hardness
Rockwell B sintered density
g / cm 3 % of theor.
density 580 116.9 7.87 93.98 620 116.3 8.07 96.37 660 113.5 8.15 97.32 700 109.4 8.16 97.44 740 109.5 8.16 97.44 780 110.1 8.11 96,84 820 109.4 8.16 97.44 860 109.7 8.10 96.72

Beispiel 7Example 7

Analog Beispiel 1 wurde ein Eisen-Kobalt-Kupfer-Oxalat gefällt, gewaschen und getrocknet, wobei eine Metallchloridlösung, enthaltend etwa 45 g/l Fe, 45 g/l Co und 10 g/l Cu, eingesetzt wurde.Analogously to Example 1, an iron-cobalt-copper oxalate was precipitated, washed and dried, a metal chloride solution containing about 45 g / l Fe, 45 g / l Co and 10 g / l Cu was used.

Ein Teil des erhaltenen Mischmetalloxalates wurde direkt im Wasserstoffstrom über 6 Stunden bei 520°C reduziert (Charge A). Ein weiterer Teil des Materials wurde zunächst unter atmosphärischer Luft über 3 Stunden bei 300°C behandelt und anschließend über 130 Minuten bei 520°C im Wasserstoffstrom reduziert (Charge B).A portion of the mixed metal oxalate obtained was directly in the hydrogen stream Reduced for 6 hours at 520 ° C (Charge A). Another part of the material was initially treated in atmospheric air for 3 hours at 300 ° C and then reduced over 130 minutes at 520 ° C in a hydrogen stream (Charge B).

Die Metallpulver hatten die in Tabelle 3 dargestellten Eigenschaften. Beispiel 7A 7B Teilchengröße FSSS, µm 4,67 4,8 Mastersizer D10 µm 12,91 14,43 D50 µm 35,23 36,72 D90 µm 430,22 419,9 Dichte g/cm3 7,91 8,04 O2-Gehalt ppm 3210 2100 C-Gehalt ppm 200 50 The metal powders had the properties shown in Table 3. example 7A 7B particle size FSSS, µm 4.67 4.8 Mastersizer D10 µm 12,91 14.43 D50 µm 35.23 36.72 D90 µm 430.22 419.9 Density g / cm 3 7.91 8.04 O 2 content ppm 3210 2100 C content ppm 200 50

Mit den Metallpulvern wurden Heißpreßtests wie in Beispiel 6 durchgeführt. Die Ergebnisse sind in Tabelle 4 angegeben (HBR = Rockwell Härte B, SD = Sinterdichte g/cm3, % TD = % der theoretischen Dichte): Beispiel 7 A Beispiel 7 B Sintertemperatur °C HRB SD % TD HRB SD % TD 580 105,8 7,55 88,95 110,9 7,92 93,83 620 111,1 8,05 94,84 111,3 8,22 97,38 660 111,2 8,19 96,49 110,6 8,22 97,38 700 110,6 8,19 96,49 109,8 8,22 97,38 740 109,6 8,20 96,6 107,5 8,22 97,38 780 109,6 8,19 96,49 108,6 8,24 97,62 820 108,6 8,18 96,37 104,4 8,24 97,62 860 106,6 8,20 96,60 106,2 8,23 97,5 Hot press tests as in Example 6 were carried out on the metal powders. The results are given in Table 4 (HBR = Rockwell hardness B, SD = sintered density g / cm 3 ,% TD =% of the theoretical density): Example 7 A Example 7 B Sintering temperature ° C HRB SD % TD HRB SD % TD 580 105.8 7.55 88.95 110.9 7.92 93.83 620 111.1 8.05 94.84 111.3 8.22 97.38 660 111.2 8.19 96.49 110.6 8.22 97.38 700 110.6 8.19 96.49 109.8 8.22 97.38 740 109.6 8.20 96.6 107.5 8.22 97.38 780 109.6 8.19 96.49 108.6 8.24 97.62 820 108.6 8.18 96.37 104.4 8.24 97.62 860 106.6 8.20 96,60 106.2 8.23 97.5

Claims (4)

  1. Process for preparing metal and alloy powders containing at least one of the metals iron, copper, tin, cobalt or nickel by mixing aqueous metal salt solutions with an aqueous carboxylic acid solution, separating the precipitation product from the mother liquor and reducing the precipitation product to the metal, characterized in that the aqueous carboxylic acid solution contains solid carboxylic acid in such an amount that the mother liquor is still at least 10% saturated, based on aqueous solution free of metal salt, after the precipitation is complete.
  2. Process according to Claim 1, characterized in that the precipitation product is subjected to thermal decomposition at from 200 to 1000°C in an oxygen-containing atmosphere prior to reduction to the metallic alloy powder.
  3. Process according to Claim 1 or 2, characterized in that the metal salt solution is introduced into an initially charged aqueous carboxylic acid suspension.
  4. Process according to any of Claims 1 to 3, characterized in that aqueous metal salt solution and carboxylic acid are introduced continuously into a precipitation reactor and a mother liquor containing the precipitation product is continuously taken off.
EP99923562A 1998-05-20 1999-05-08 Sinter-active metal and alloy powders for powder metallurgy applications and methods for their production and their use Expired - Lifetime EP1079950B1 (en)

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