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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B34/00—Obtaining refractory metals
  • C22B34/10—Obtaining titanium, zirconium or hafnium
  • C22B34/12—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08
  • C22B34/1263—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining metallic titanium from titanium compounds, e.g. by reduction
  • C22B34/1268—Obtaining titanium or titanium compounds from ores or scrap by metallurgical processing; preparation of titanium compounds from other titanium compounds see C01G23/00 - C01G23/08 obtaining metallic titanium from titanium compounds, e.g. by reduction using alkali or alkaline-earth metals or amalgams

Definitions

• the invention relates to a method for producing sinterable alloy powders based on titanium by calciothermal reduction of the oxides of the metals forming the alloys in the presence of indifferent additives.
• Titanium and titanium-based alloys have found many applications due to their special material properties. Due to the relatively complex manufacturing processes, the alloys of titanium in particular are relatively expensive.
• titanium the naturally occurring oxide is reduced with coal in the presence of chlorine and titanium tetrachloride is obtained, which is processed into the titanium sponge by reduction with metallic sodium or magnesium.
• the titanium sponge is then, after adding the other alloy components, such as Aluminum and vanadium, melted and cast or rolled into bars, profiles or sheets.
• the near-contour shaped parts are given their final shape by machining. A disadvantage of this procedure is the sometimes considerable amount of machined alloy. It is therefore not readily possible to produce complicated shaped parts in this way at reasonable prices.
• the production of such molded parts is more successful using powder metallurgy.
• the alloy Powder in particular, two methods have become known.
• One method is characterized in that the titanium sponge is fused together with alloy partners to form a rod-shaped electrode.
• the electrode is atomized under the action of a plasma flame, and at high speeds in rotation to powder, but because of the dung B il- of agglomerates as a rule, the powder obtained an additional comminution (grinding up) has to be subjected.
• this so-called REP process is extremely complex, in particular due to the apparatus costs, and moreover is limited to one in terms of the batch weight. limited electrode size.
• the second way known for the preparation of the powder consists in hydrogenating the titanium sponge, grinding the brittle titanium hydride, adding the other alloying partners in powder form, intimately grinding, dehydrating at elevated temperatures in vacuo and the powder obtained in a manner known per se pressed and sintered. This process is also complex and cannot satisfy the process.
• the invention is therefore based on the object of finding a method for producing sinterable alloy powders based on titanium which does not have these disadvantages.
• the alloy powders must have a certain grain size and grain size distribution in order to achieve a sufficient bulk density and tapping density.
• the alloy powders should be uniform, i.e. each powder particle must have the same composition and structure as the other alloy particles.
• the alloy powders must also be free from precipitates of oxides, nitrides, carbides and hydrides, since otherwise the sinterability is not ensured. Only the sum of the aforementioned properties makes an alloy powder possible for the production of molded parts by pressing and sintering. It should therefore be possible to subject the powders to hot isostatic pressing, which means that it is possible to manufacture near-contour components without complex post-processing.
• the invention is in particular the object of producing L-e g michspulver such uniformity and purity, that they are useful in the aircraft industry for the production of mechanically highly resistant parts.
• a process for the production of alloy powders preferably suitable for the production of sintered bodies by reduction of metal compounds and possibly subsequent removal of by-products, is known, which is characterized in that intimate mixtures of such metal compounds, at least one of which is difficult to reduce , can be reduced with metals such as sodium, calcium.
• An embodiment of the process is characterized in that the reduction takes place in the presence of indifferent, refractory, easily releasable substances.
• the process according to the invention is thus characterized by a combination of special process measures.
• the oxides of the alloy partners are first provided in the amounts which correspond to the desired alloy composition. It has been shown in many experiments that direct reduction of these mixtures of the oxides does not produce any sinterable alloy powders, regardless of the pretreatment. Metal powders are formed, some of which can consist of the desired alloy, but also, in uncontrollable amounts, of pure titanium or of the metals or alloys of the others Reaction partners exist. It also contains particles which contain titanium as a base and the other metal components alloyed in different amounts.
• the molar ratio of the metal oxides to be reduced to alkaline earth oxide or alkaline earth carbonate is 1: 1 to 6: 1, a range from about 1.2: 1 to 2: 1 is preferred.
• Calcium oxide or calcium carbonate is preferably used as the alkaline earth oxide or carbonate.
• the alkaline earth oxide that is to say preferably the calcium oxide
• the alkaline earth oxide is not added as a desensitizing agent, but rather is used to produce a mixed oxide in which the mixture of the metal oxides to be reduced with the alkaline earth oxide or Alkaline earth carbonate after homogenization at temperatures of 1000 to 1300 ° C, in particular 1200 to 1280 ° C, 6 to 18 h, preferably 8 to 12 h, is annealed.
• a mixed oxide of reduced number of phases is formed which, after comminution to a particle size of approximately ⁇ 1 mm, has the same gross composition.
• alkaline earth carbonate in particular calcium carbonate
• the calcium carbonate cleaves carbon dioxide. Calcium oxide forms with a fresh and active surface. At the same time, the annealed mixed oxide is loosened and can be crushed more easily.
• the annealing product can be comminuted in a simple manner, for example by means of jaw crushers and subsequent grinding with a cone Mill.
• the annealed mixed oxide thus obtained is mixed with small-scale calcium.
• the calcium should preferably be about 2 mm to 3, in particular have a particle size of about 0. 5 mm to 8.
• the amount of calcium is related to the oxygen content of the oxides to be reduced. Based on the oxygen content of the oxides to be reduced, 1.2 to 2.0 times, preferably 1.3 to 1.6 times, the equivalent amount of calcium is used. It takes therefore, for example, per mole, Ti0 2 2.4 to 3.6 mol. Ca, per mole of Al 2 O 3 3.6 to 5.4 moles Ca per mole of V 2 0 5 6.0 to 9.0 Mol C a.
• a booster is a compound that reacts with strong exothermic heat in the metallothermic reduction.
• boosters are oxygen-rich compounds, e.g. Calcium peroxide, sodium chlorate, sodium peroxide, potassium perchlorate.
• oxygen-rich compounds e.g. Calcium peroxide, sodium chlorate, sodium peroxide, potassium perchlorate.
• the molar ratio of oxides to boosters to be reduced is 1: 0.01 to 1: 0.2, preferably 1: 0.03 to 1: 0.13.
• the reaction mixture consisting of oxides, calcium and boosters is now mixed thoroughly.
• the green compacts are now filled into a reaction crucible.
• a reaction crucible is used which is chemically and mechanically stable under the given conditions.
• Crucibles made from titanium sheets have proven particularly useful.
• the reaction crucible is now closed, with a low lumen socket in the closure cover, through which the crucible can be evacuated.
• the reaction crucible is placed in a heatable reaction furnace and at an initial pressure of about 1. 10 -4 to 1. Evacuated 10 -6 bar.
• the R eak- tion crucible is then heated to a temperature of 1000 to 1300 ° C. Some calcium distils into the suction nozzle, condenses there and closes the nozzle.
• Such a self-closing crucible is known for example from DE-AS 11 24 248.
• a pressure is then set in the reaction crucible which corresponds to the pressure of the calcium at the given temperature.
• the calcium which is removed from the equilibrium during the reaction and is bound as an oxide can be neglected, since the replication of the gaseous calcium takes place faster than the path reaction.
• the reaction crucible is left at the reaction temperature for about 2 to 8, preferably 2 to 6 hours.
• the gaseous potassium formed during the reduction of the potassium perchlorate used as a booster and which passes through the evacuation port before the reaction vessel is sealed by condensing calcium is absorbed in an intermediate vessel which is filled with silica gel.
• the booster especially the potassium perchlorate
• the booster is reduced.
• calcium oxide and calcium chloride are formed.
• the heat released in this way reduces the reduction of the metal oxides favored and accelerated. It occurs in and after the desired R alloying e-production a.
• the melting temperature of the alloy which is surrounded on all sides by calcium oxide, is briefly exceeded. Supported by the molten calcium chloride and under the influence of the surface tension, the alloy particles form in the desired shape of an approximate spherical shape.
• the reaction crucible is then removed from the furnace, the crucible is opened, the reaction product is removed from the crucible and comminuted to a particle size of ⁇ 2 mm.
• the calcium oxide is treated with a suitable solvent, especially dilute acids, e.g. diluted acetic acid or dilute hydrochloric acid, or complexing agents, such as ethylenediaminetetraacetic acid, leached.
• a suitable solvent especially dilute acids, e.g. diluted acetic acid or dilute hydrochloric acid, or complexing agents, such as ethylenediaminetetraacetic acid, leached.
• the remaining alloy powder is washed neutral and dried.
• the reduced reaction product obtained in process step c) contains hydrogen in an impermissible amount, it is advisable to use the reduction product of a vacuum treatment at 1 .
• the alloy powder obtained according to the invention Due to its particle size and particle size distribution, the alloy powder obtained according to the invention has the required tap density of about> 60% of the theoretical density. Knock densities of up to almost 70% of theory are achieved.
• the examination of the alloy powders by microscopic micrographs and with the microsensor prove a uniform composition of each of the alloy particles. They are free of excretions which impair the sinterability or would reduce the mechanical strength of the molded bodies obtained by hot isostatic pressing.
• the properties of the standard alloys examined e.g. TiA16V4; TiA16V6Sn2; TiAl4Mo4Sn2; TiAl6Zr5Mo0.5Si0.25; TiA12V11.5Zr11Sn2; TiA13V10Fe3; manufacture flawlessly.
• the particular advantages of the process according to the invention additionally consist in the fact that the raw materials, namely the oxides of the metals, are available in practically unlimited quantities. Apart from their cleaning, they do not require any special processing. By selecting the type and amount of the metal oxides to be reduced, the alloys in the desired composition can easily be produced.
• the yields in the process according to the invention are very high (> 96%), since no loss-making intermediate steps, as in the process of the prior art, are required are.
• the method according to the invention is therefore particularly inexpensive. The expenditure on equipment is kept to a minimum. The reproducibility of the alloys produced according to the process is great.
• the sinterable alloy powders can be produced directly from naturally occurring, purified raw materials while avoiding remelting processes.
• the bulk density is approx. 1.40 g / cm 3 and the tap density is approx. 2.30 g / cm 3 .
• the yield of mixed oxide phases amounts to 2418.0 g ⁇ 99.7%.
• the grain distribution curve has the following composition:
• the chemical analysis of the alloy powder shows the following composition:
• the metallographic examination of the alloy powder shows that structurally homogeneous alloy particles are present, the microstructure being from lamellar to fine-globular assign. A homogeneous distribution between a high a and a low ß content can be seen in the alloy.
• the mixed oxide After comminution, the mixed oxide has the following particle size distribution:
• the bulk density of the comminuted mixed oxide is approximately 1.33 g / cm 3
• the tap density is approximately 1.97 g / cm 3 .
• the mixed oxide is obtained with a yield of 2154.9 g ⁇ 99.16%.
• 895 g of the mixed oxide are intimately mixed with 1290 g Ca and 133 g KClO 4 ( ⁇ 0.12 mol KClO 4 / mol alloy powder), annealed at 1100 ° C. for 12 hours and treated as in Example 1.
• the yield of titanium alloy powder is 365.5 g, which corresponds to 96.75% of the theoretically possible yield.
• the alloy powder has a bulk density of 2.14 g / cm 3 ⁇ 48.97% and a K lopf Why of 2.78 g / cm 3 ⁇ 63.76%, based on the theoretical density on.
• the grain distribution curve of the alloy powder has the following composition:
• the alloy particles have the same structure, which can largely be characterized as lamellar to fine globular.
• the microstructure also shows that the alloy particles have a homogeneous a and ⁇ phase distribution.
• the bulk density of the comminuted oxide is 1.63 g / cm 3 and the tap density is 2.58 g / cm 3 . After the annealing, the mixed oxide is obtained with a yield of 2415.0 g ⁇ 97.4%.
• the alloy powder has a bulk density of 2.18 g / cm 3 ⁇ 49.3% and a tap density of 2.81 g / cm 3 ⁇ 63.45% of the theoretical density.
• the grain distribution curve of the alloy powder has the following composition:
• the chemical analysis shows the following composition:
• the metallographic examination shows alloy particles with a homogeneous structure and phase distribution.
• the microstructure is fine lamellar structure of the a-phase which is stabilized by innzu accounts Z. There are no Ti 3 Al phases that hinder the non-cutting shaping.
• the mixed oxide has the following grain distribution curve:
• the bulk density of the composite oxide is 1.84 g / cm 3 and the toilet fêt p is 2, 76 g / cm 3.
• the yield of usable mixed oxide is 2358.0 g ⁇ 98.1% of the theoretical yield.
• the alloy powder has a bulk density of 2.39 g / cm 3 ⁇ 52.8% and a tap density of 2.88 g / cm 3 ⁇ 63.6% of the theoretical density.
• the grain distribution curve has the following composition:
• the chemical analysis of the alloy powder shows the following composition:
• the metallographic examination shows alloy particles with a homogeneous structure. In addition to the stabilized a phase as the main component, there is a small ⁇ component in the alloy particles.
• the bulk density of the mixed oxide is 2.12 g / cm3 ⁇ 48.11% and the tap density is 2.54 g / cm 3 ⁇ 57.65% of the theoretical density.
• the yield of usable mixed oxide is 2425.0 g and corresponds to 98.7% of the theoretical yield.
• the alloy powder has the following grain distribution curve:
• the chemical analysis of the alloy powder shows the following composition:
• the bulk density of the annealed mixed oxide is 2.415 g / cm 3 ⁇ 50.15% and the tap density 3.185 g / cm 3 ⁇ 66.2% of the theoretical density.
• the yield of usable mixed oxides is 2412.2 g, which is 94.2% of the theoretical yield.
• the alloy powder has a bulk density of 2.68 g / cm 3 ⁇ 55.65% and a tap density of 3.13 g / cm3 ⁇ 65.1% of the theoretical density.
• the alloy powder has the following grain distribution curve:
• the chemical analysis of the alloy powder shows the following composition:
• the metallographic examination of the alloy powder shows particles with a homogeneous structure and ⁇ stabilization. Sintered parts made from these alloys result in components with relatively high fracture toughness.
• 1325.2 g TiO 2 , 55.2 g Al 2 O 3 , 168.6 g V 2 O 5 , 39.4 g Fe 3 0 4 and 1601.2 g CaCO 3 are mixed homogeneously and at a temperature of 1100 ° C annealed for 12 h.
• the grain distribution curve then has the following composition:
• the bulk density of the annealed mixed oxide is 2.314 g / cm 3 ⁇ 49.61% and the tap density 3.012 g / cm 3 ⁇ 64.6% of the theoretical density.
• the yield of usable mixed oxides is 2398.6 g ⁇ 96.5. % of theoretical yield.
• the metallographic examination of the powdery alloy shows particles with a homogeneous structure and a-phase stabilized. Sintered parts made from these alloy powders are said to have a higher creep resistance.
• the alloy powders produced by the process according to the invention contain a typical process content of 0.05 to 0.15% by weight of calcium. However, this amount has no influence on the quality and processability of the alloy powder.
• the bulk density is approximately 1.45 g / cm.
• the tap density is 2.28 g / cm 3 .
• the yield is 2605.8 g ⁇ 98.7%.
• 1000 g of this mixed oxide are homogeneously mixed with 1051.62 g Ca (1: 1.2 mol) and 228.50 g KClO 4 ( ⁇ 0.20 mol KC10 4 / mol alloy powder) and green bodies with the dimensions of 50 mm diameter and a height of 30 mm.
• reaction crucible is inserted into the furnace and the furnace is closed.
• the reaction chamber with reduction crucible is evacuated to a pressure of ⁇ 1 ⁇ 10 -4 bar at room temperature and then heated up to 1300 ° C. and held at this temperature for 2 hours.
• the reaction product is comminuted to a maximum particle size of ⁇ 2 mm, the comminuted reaction product is leached with dilute nitric acid, filtered and washed until neutral.
• the obtained Le g ists- powder is vacuum treated and dried.
• the yield of alloy powder is 363.5 g ⁇ 94.8%, based on the theoretical yield.
• the alloy powder obtained has a bulk density of 2.0 3 g / cm 3 ⁇ 46.56% and a tap density of 2.69 g / cm 3 ⁇ 61.7% of the theoretical density.
• the particle size distribution curve of the L eg michspulvers has the following composition:
• the chemical analysis of the alloy powder shows the following composition:
• the metallographic examination of the alloy powder shows that there are structurally homogeneous alloy particles with a uniform a and ⁇ distribution.
• the proportion of a in the alloy particles predominates.
• the development of the individual phases can be classified as fine globular to lamellar.
• the annealed mixed oxide is comminuted to a grain size of ⁇ 1 mm using a jaw crusher, cone and cross beater mill nert and has the following grain distribution curve:
• the bulk density of the annealed, mixed oxide phases is 1.58 g / cm 3 and the tap density is approximately 2.48 g / cm 3 . After annealing, the yield is 1665.7 g 97.9%, based on the theoretical yield.
• the green compacts are then inserted into the reaction crucible, the reaction crucible is placed in the furnace and the furnace is then closed.
• the reaction chamber with the reduction crucible is then evacuated at room temperature to a pressure of ⁇ 1 ⁇ 10 -6 bar and then heated up to 1000 ° C. and kept at this temperature for 8 hours.
• the reaction product is crushed to a grain size of ⁇ 2 mm, then leached with formic acid, vacuum-treated and dried.
• the yield of alloy powder is approx. 358 g ⁇ 93.5%, based on the theoretical yield.
• the alloy powder obtained has a bulk density of 1.91 g / cm 3 ⁇ 43.80% and a K lopf Why of 2.76 g / cm 3 ⁇ 63.6% theoretical density.
• the grain distribution curve has the following composition:
• the chemical analysis of the alloy powder shows the following composition:
• the metallographic examination of the alloy powder shows that structurally homogeneous alloy particles are present, the microstructure being lamellar to fine-globular.
• the alloy mainly consists of a high a component and a low ⁇ component.
• the annealed mixed oxide is crushed to a grain size of ⁇ 1 mm using a jaw crusher, cone and cross beater mill and has the following grain distribution curve:
• the bulk density of the mixed oxide is 1.54 g / cm 3 and the tap density is 2.49 g / cm 3 . After annealing, the yield is 1869.6 g ⁇ 99.7% of the theoretical yield.
• the reaction product is crushed to a maximum grain size of ⁇ 2 mm, then leached with dilute hydrochloric acid, vacuum-treated and dried.
• the yield of alloy powder is 501.8 g ⁇ 97.4%, based on the theoretical yield.
• the alloy powder produced has a bulk density of 2.43 g / cm 3 ⁇ 53.3% and a tap density of 2.978 g / cm 3 ⁇ 65.2% of the theoretical density.
• the chemical analysis of the alloy powder shows the following composition:
• the metallographic examination of the alloy powder shows particles with a homogeneous structure and stabilized a-phase.

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  • 1980-05-09 DE DE3017782A patent/DE3017782C2/de not_active Expired
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