DE1181920B - Process for the production of metal carbides in fine and uniform distribution containing powder and molded bodies - Google Patents

Description

Process for making metal carbides in finer and more uniform Distribution Containing Powders and Moldings The invention relates to a method for the production of powders or moldings from metal carbides and optionally Binder metal in a very fine and even distribution of components.

To make cemented carbides, one generally sets up first the individual carbides by carburizing powdered metals or their oxides with solid carbon below the melting point of the carbide, usually at Temperatures from 1200 to 1900 ° C. In the manufacture of powders that several Containing carbides are generally mechanical mixtures of metal oxides or of metals carburized with soot, or mechanical mixtures of individual components are combined Carbides through heat diffusion.

The carbide powders are then mixed with a metal powder that acts as a binder, usually cobalt or nickel, mixed, which means a high level of skill and requires precise monitoring of the particle size and is therefore expensive. Here it is necessary to grind the mixture for several hours or several days, to achieve such a fineness that the metal does not come from the metal carbide can be separated magnetically. The grinding is usually done with hard balls in wear-resistant mills that z. B. lined with stellite or tungsten carbide are. Here, however, there is a certain degree of oxidation and the entrainment of the grinding media can not be avoided. To prevent oxidation it is necessary in one To grind in a hydrogen atmosphere or in the presence of a non-oxidizing liquid. With the latter measure, however, the powders still have to be subjected to a reduction to dry them and remove all oxides.

In this state, however, the powders are difficult to shape and generally too fine to flow evenly into the dies. Therefore, one has to mix the powders with a binder and briquette this mixture in a simple form, after which the briquettes are ground again in order to obtain more easily flowable powders. But even in this state, the powders cannot be easily compressed and only simple shapes can be produced. The pressed bodies are then presintered to give them a certain strength and to evaporate the agglomerating agent. The compacted bodies are then sintered to a density of almost 100 % and then brought into their final shape by grinding. It is clear that the production of sintered carbides is expensive, since this requires many process steps, special equipment and special care.

The continuous compaction of these powders with the help of metal rollers further away from serious difficulties. The powders are very hard and will hurt you Rollers, if they are not made from expensive carbides. The emerging Strips are extremely brittle and - disintegrate with the slightest shock. This procedure is therefore only carried out in the laboratory.

The invention relates to a method for the production of powders or Moldings made from at least two metal carbides or from at least one metal carbide and at least one binding metal with a very fine and even distribution of the Components, whereby an amount of metal oxide is reduced and carburized. The procedure is characterized in that one consists of metals and / or metal compounds existing raw materials into one! vaporizable and smokable solvents dissolves or disperses, this solution or dispersion evaporates to dryness so quickly, that no significant segregation of the dissolved or dispersed components occurs, the solid residue is crushed, reduced, carburized and, if necessary, into molded bodies processed.

When the starting materials are treated with the solvents real solutions, colloidal ones, depending on the working conditions and the substances used Solutions or fine dispersions.

As a vaporizable and smokable solvent in the sense of Invention one can use ammonia, acetic acid, sulfuric acid, nitric acid or water Use alone or in a mixture. The quick evaporation the solution or dispersion is advantageously in droplet form or in a thin layer carried out.

When evaporating, the excess solvents are evaporated or smoked and the resulting salts or other compounds under formation an intimate mixture of oxides decomposed. The evaporation is expediently carried out the solution or dispersion at about 150 to 450 ° C.

After evaporation you can the residue obtained before the further Heat processing to drive off the last remaining solvent and further decompose any existing compounds.

Those resulting from evaporation and, if necessary, further heating Solvents or their decomposition products can be collected in a manner known per se, if necessary regenerated and used again for dissolving.

The solid residue obtained after these process steps is then comminuted to the desired particle size and reduced in a manner known per se, z. B. with hydrogen at higher temperatures.

The resulting metal powder can finally be heated carburized with carbonaceous substances such as carbon black or graphite, d. H. whole or partially converted into carbides. If necessary, another Connect shredding.

If you want to produce moldings, it is advisable in some cases, to make the shaping after reducing and before carburizing, namely in the presence of the carburizing agent. This way of working has the advantage that you do not use a mixture of the often very hard carbides z. B. by rolling needs to deform. After shaping, the shaped bodies can then, for. B. between Carbon blocks are heated in a batch or continuous furnace, with a Carburizing and sintering take place.

According to the method of the invention, powders and shaped bodies can be of different types Composition are prepared, e.g. B. from tungsten carbide-cobalt, tungsten carbide - molybdenum carbide - nickel - cobalt, molybdenum carbide - vanadium carbide - nickel, tungsten carbide - titanium carbide, tungsten carbide - titanium carbide - cobalt. Example 1 10 parts of cobalt powder were dissolved in excess nitric acid. A solution of 125 was added to this Part ammonium metatungstate (85% W03) in water. The mixture of these two solutions was placed in a drying drum kept at 250 ° C. The escaping here Nitric acid, which contained oxides of nitrogen, was captured in itself regenerated in a known manner to nitric acid and again to dissolve a new batch used. The homogeneous residue, consisting largely of oxides, was in heated in an oven to 600 ° C for 15 minutes and ground in a hammer mill, until all particles have a diameter of about 1 @. had.

This powder was reduced in an oven at 1000 ° C. for 40 minutes with cracked propane gas, which essentially consisted of hydrogen and carbon oxide, to form a powdery alloy of cobalt and tungsten. The alloy powder was mixed with 5.85 ° / Q carbon black, heated in a rotating furnace for 20 minutes in an atmosphere of cracked ammonia at 1000 ° C and finally ground again in a hammer mill into particles with a diameter of about 1 #t. The end product consisted of 900 % tungsten carbide and 10% cobalt in a molecular mixture.

The powder was mixed with 1% camphor and added at 3100 kg / cml right-angled test specimens. These bodies were in a charcoal crucible sintered in a muffle furnace in a hydrogen atmosphere for 60 minutes at 1500 ° C. The body treated in this way had a density of 14.4 g / cm3 and a hardness of 89 RA and a flexural strength of about 200 kg / mm 2.

Example 2 The processing according to Example 1 up to and including the Reduction with hydrogen.

The metal powder was mixed with graphite 5,850 /, and compacted between rollers to form a strip about 0.75 mm thick. The strips had good processing strength.

Part of this strip was between carbon blocks in one Furnace sintered in a hydrogen atmosphere at 1500 ° C for 120 minutes. The resulting carburized strips had a density of 14.4 g / cm3, a hardness of 89 RA and a flexural strength of 140 kg / mm '.

Another part of the strip became various cutting tools, z. B. Saw blades and knife blades, processed; the resulting shapes were sintered and carburized as described above. The various moldings shrunk evenly by about 15%, so that one did not have to grind the tools needed. They were hard and dense and could be used commercially.

Example 3 63.5 parts of Mo03 and 57.5 parts of HQW04 were made into 86.6 parts 29% dissolved in aqueous ammonia. An aqueous solution of 22.4 parts was added NiS04 - 6 HZO and 23.9 parts CoS04 - 7 H $ 0. The mixture of these solutions was in brought a drying drum held at 200 ° C. The ammonia escaping in the process was collected and used again to dissolve a new batch. The homogeneous one The residue, consisting largely of oxides, was left in an oven for 15 minutes heated to 600 ° C for a further 15 minutes and heated to 900 ° C in a hammer mill ground until all particles were about 1 #t in diameter.

This powder was cracked with propane gas for 40 minutes at 1000 ° C reduced, being a powdery alloy of molybdenum, tungsten, and nickel Cobalt was created.

The alloy powder was mixed with 5.7% carbon black, heated for 20 minutes at 1000 ° C. in an atmosphere of cracked ammonia and finally ground again in a hammer mill into particles with a diameter of about 1 t. The end product consisted of 45 % molybdenum carbide, 45% tungsten carbide, 5% nickel and 5% cobalt.

This powder was mixed with 10% camphor and made into test specimens pressed. The test specimens were placed in a carbon crucible in a muffle furnace be in a hydrogen atmosphere for 60 minutes Sintered at 1500 ° C. A hard, dense body of high hardness and high flexural strength resulted. Example 4 One works according to Example 13 up to and including the reduction with hydrogen.

The metal powder was mixed with 5.7% graphite and between Rollers compacted into a strip about 0.75 mm thick. The strip had one good processing strength.

Part of this strip was between carbon blocks in one Muffle furnace sintered in a hydrogen atmosphere for 120 minutes at 1500 ° C: The resulting carburized strip was hard and dense.

Another part of the strip became various cutting tools, z. B. saw blades and knife blades, processed: the resulting shapes were sintered and carburized as described above. The various moldings shrunk evenly by about 15%, so that one did not have to grind the tools needed. The tools were hard and tight and could be used commercially. Example s 61.4 parts of V205 and 60.0 parts of Mo03 were in 97.7 parts of 29% aqueous Dissolved ammonia. A solution of 63.6 parts of Ni (CZH302) 2-4H20 was then added in 50 parts of water. The mixture of these solutions was kept at 200 ° C in a Brought drying drum. The ammonia escaping here was collected and used again to dissolve a new batch. The homogeneous for the most part off Oxide residue was heated in an oven at 550 ° C for 15 minutes and ground in a hammer mill until all of the particles are about 1 # had.

This powder was in an oven for 60 minutes with cracked propane gas reduced, the temperature of the furnace on the inlet side at 300 ° C and on the outlet side was kept at 1200 ° C. A powdery alloy was created of molybdenum and nickel mixed with vanadium oxide.

The powder was mixed with 23; 1 % carbon black, heated in a nickel crucible for 2 hours in an atmosphere of cracked ammonia at 1200 ° C. and finally comminuted again in a hammer mill to give particles with a diameter of about 1 t. The end product consisted of 42.5% vanadium carbide, 42.5% molybdenum carbide and 15% nickel.

The powder was mixed with 1% camphor and pressed into a test specimen at a pressure of 3200 kg / cm '. The test specimen had a theoretical density of 600 % and had good processing strength.

The test rod was placed in a carbon crucible in a muffle furnace heated in a hydrogen atmosphere at 145 ° C for 60 minutes. There was a hard, dense body of high hardness and high flexural strength.

Example 6 120 parts of ammonium metatungstate (850 / " WO3) were dissolved in 42 parts of water. 17.7 parts of powdered TiO2 were stirred into this solution. The dispersion was dried in a drying drum kept at 250 ° C. The homogeneous residue was in an oven Heated to 500 ° C for 15 minutes and ground in a hammer mill until all particles were about 1 #t in diameter.

This powder was cracked in an oven at 1000 ° C for 4 minutes Reduced propane gas, being a molecular mixture of tungsten and titanium dioxide originated.

The mixture was ground again, mixed with 16.00% carbon black, heated in a carbon crucible with a carbon lid at 1900 ° C. for 3 hours and finally again comminuted in a hammer mill to give particles with a diameter of about 1 t. The end product consisted of 13.3 % titanium carbide and 86.70 % tungsten carbide. Example ? 90 parts of the end product obtained according to Example 6 were stirred into 150 parts of an aqueous solution which contained 41.9 parts of Co (CZH30 @ 2-411.0. The dispersion) was dried in a drying drum kept at 200.degree. The homogeneous residue was heated to 500 ° C. for 15 minutes in a nitrogen atmosphere and ground in a hammer mill until all particles were about 1 #t in diameter.

This powder was reduced with dry hydrogen in an oven at 800 ° C. for 20 minutes and finally again comminuted in a hammer mill into particles with a diameter of about 1 μL. The end product consisted of 12 % titanium carbide, 78% tungsten carbide and 200% cobalt.

The powder was mixed with 1% camphor and pressed at 3000 kg / cm2 to form rectangular test specimens. The bodies had good workability and handling strength. These bodies were sintered in a coal boat in a muffle furnace in dry hydrogen for 60 minutes at 1500 ° C. The resulting body had the high strength and high hardness characteristic of materials of this composition, with the additional advantage of a homogeneous composition in a molecular mixture.

Claims (7)

Claims: 1. Process for the production of powders or moldings of at least two metal carbides or of at least one metal carbide and at least a binding metal with a very fine and even distribution of the components, wherein a metal oxide mixture is reduced and carburized, characterized in that, that the starting materials consisting of metals and / or metal compounds dissolves or disperses in a vaporizable or smokable solvent, this solution or dispersion evaporated to dryness so quickly that no significant Separation of the dissolved or dispersed constituents occurs, the solid residue crushed, reduced, carburized and, if necessary, processed into shaped bodies. 2. The method according to claim 1, characterized in that one is as vaporizable or consumable solvents ammonia, acetic acid, sulfuric acid, nitric acid and / or water is used. 3. The method according to claim 1 or 2, characterized in that that one is the solution or dispersinn in droplet form or in thinner Layer evaporated to dryness. 4. The method according to any one of claims 1 to 3, characterized in that the solution or dispersion is evaporated to dryness at about 150 to 450 ° C. 5. The method according to any one of claims 1 to 4, characterized in that that the residue obtained after evaporation of the solution or dispersion heated before further processing in order to drive off the last remnants of the solvent and to further decompose any existing compounds. 6. Procedure according to one of the Claims 1 to 5, characterized in that that obtained on reducing Mixture mixed with charcoal, pressed and heated until sintering. 7. Procedure according to Claim 6, characterized in that the carbon-containing, reduced mixture before carburizing and sintering into bodies such as tools or tool blades forms. Documents considered: R. Kieffer and P. Schwarzkopf, Hartstoffe and hard metal; 1953, p. 159.