Classifications

• • 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

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Powder Metallurgy (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Manufacture And Refinement Of Metals (AREA)

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• 1998
  • 1998-05-20 DE DE19822663A patent/DE19822663A1/de not_active Ceased
• 1999
  • 1999-05-08 WO PCT/EP1999/003170 patent/WO1999059755A1/de active IP Right Grant
  • 1999-05-08 US US09/700,533 patent/US6554885B1/en not_active Expired - Fee Related
  • 1999-05-08 CN CNB998062944A patent/CN1254339C/zh not_active Expired - Fee Related
  • 1999-05-08 DE DE59906598T patent/DE59906598D1/de not_active Expired - Lifetime
  • 1999-05-08 EP EP99923562A patent/EP1079950B1/de not_active Expired - Lifetime
  • 1999-05-08 CA CA2332889A patent/CA2332889C/en not_active Expired - Fee Related
  • 1999-05-08 AT AT99923562T patent/ATE246976T1/de active
  • 1999-05-08 KR KR1020007012982A patent/KR100543834B1/ko not_active IP Right Cessation
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  • 1999-05-08 JP JP2000549408A patent/JP4257690B2/ja not_active Expired - Fee Related
• 2008
  • 2008-07-30 JP JP2008196006A patent/JP2009001908A/ja active Pending

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