EP0839920A2 - Procédé de préparation de poudre de départ pour matériau dur à grain fin - Google Patents

Procédé de préparation de poudre de départ pour matériau dur à grain fin Download PDF

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Publication number
EP0839920A2
EP0839920A2 EP97203354A EP97203354A EP0839920A2 EP 0839920 A2 EP0839920 A2 EP 0839920A2 EP 97203354 A EP97203354 A EP 97203354A EP 97203354 A EP97203354 A EP 97203354A EP 0839920 A2 EP0839920 A2 EP 0839920A2
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EP
European Patent Office
Prior art keywords
powder
metal
reaction
cyclone
reduction
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Application number
EP97203354A
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German (de)
English (en)
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EP0839920A3 (fr
EP0839920B1 (fr
Inventor
Günter Dr. Kneringer
Wolfgang Dr. Köck
Joachim Dr. Resch
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Plansee SE
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Plansee SE
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/05—Mixtures of metal powder with non-metallic powder
    • C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
    • C22C1/053—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds
    • C22C1/056—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor with in situ formation of hard compounds using gas
    • 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 quality that can be achieved for a type of hard metal depends to a large extent on the nature of the starting powder, which is pressed and processed into a shaped hard metal body by sintering.
  • the chemical-metallurgical composition is just as important as the powder morphology, powder structure and consequently the powder preparation before pressing and sintering.
  • efforts to produce improved carbide grades have focused primarily on achieving fine grain and homogeneity of the carbide in the carbide.
  • the metallic components in the carbide hard material phase of the hard metal are primarily tungsten or titanium, in addition in the form of grain-stabilizing mixed carbides, small amounts of the high-melting metals tantalum, niobium, molybdenum, vanadium and chromium.
  • the processing steps starting with the reduction of powdered metal oxides or comparable compounds such as ammonium metallate and metal acid, through to metal carbide extraction, are essential for the later quality of hard metal types, particularly with regard to their structure.
  • Metal oxides or comparable compounds familiar to the person skilled in the art are reduced to pure metal in one or more process steps and then the metal, usually in a separate process step, is converted into metal carbide. Occasionally, reduction and carburization are also carried out in a common, ongoing process.
  • metal oxide reduction in a solid-gas reaction metal oxides on carrier boats in comparatively thin layers are continuously passed through a reduction furnace.
  • the reduction in the rotary kiln and in the fluidized bed is also common.
  • Usual processes for carbide formation are the intimate mixing of metal powder, for example tungsten metal powder, with carbon (soot particles) and subsequent reaction in a carburizing furnace.
  • metal powder for example tungsten metal powder
  • carbon silicates
  • commercial production also plays an important role in commercial production. It is determined by the price of the device in accordance with the complexity of the process, the amount of energy and reaction gas consumed per reaction unit and, above all, the factor of production time.
  • the reaction or throughput times of the powders in the devices listed are without exception in the range of hours, at best 1 to 2 hours, at worst 15 to 20 hours of reaction time.
  • the entire production process includes process steps such as grinding and mixing processes, which in turn usually take many hours.
  • powder preparation processes such as granulation of the powder by means of spray drying, largely indispensable in the hard metal industry.
  • the object of the present invention further consists in the selection of a device suitable for carrying out the method, such devices being known for the chemical conversion of various organic and inorganic materials, but for the production of hard metal powder batches to achieve homogeneous, fine-grained hard metal types were not used.
  • hard metal in claim 1 also includes materials known under the name of cermet, which in addition to carbides also contain substantial amounts of nitrides or carbonitrides in the hard material phase.
  • Cyclones are characterized in that they generally have axially or rotationally symmetrical chamber walls.
  • the material to be reacted in the form of solid particles is intimately mixed and swirled with carrier and / or reaction gas immediately upon entry into the reaction chamber and continuously blown in as a mixture in a direction deviating from the longitudinal axis of the chamber.
  • the substances introduced in this way move under the action of gravitation and centrifugal forces in accordance with the gas flow conditions prevailing in the chamber on essentially predetermined trajectories, that is to say not in a statistical movement, for example in a fluidized bed furnace.
  • the gas and particle flow is determined by the chamber walls, including any guide elements that may be attached there. There are high flow velocities tangential to these chamber walls. High relative speeds between solid and gaseous substances occur in the reaction chamber. High speed gradients between individual substances mean high turbulence intensities and result in high heat and mass transfer numbers for the individual reactants in the desired chemical reaction.
  • the duration of the reaction material in the chamber is short due to the device and process. Depending on the system design, the stay or response times are between tenths of a second and about one minute.
  • Such cyclone reactors are already used in the pyrolysis of sawdust: J. Lede et al, “Flash Pyrolysis of Wood in a Cyclone Reactor", Chem. Eng. Proc. 20 (1986), pp. 309-317; J. Cousins et al, "Gasification of Sawdust in an air blown cyclone gasifier", Ind. Eng. Chem. Process Des. Dev. 24 (1985), pages 1281-1287; in slag incineration and incineration of sludge residues, T. Murakami et al, “Characteristics of Melting Process for Sewage Sludge", Wat. Sci, Tech. 23 (1991), pages 2019-2028.
  • a major advantage of the method in question over the known methods for producing submicron or nanophase powder for powder press batches for producing hard metal is that raw material powder (metal compounds to be reduced) are used can, as they are provided from the mineral processing without special additional treatment and can be processed into a very uniform and fine-grained structure after using this method.
  • the powder batches which are produced very economically by the process in question, allow hard metal qualities to be achieved which correspond to or are even superior to those achieved by the processes described above, production of nanophase composite powders, production of submicron carbides.
  • reaction times in the chemical process steps reduction and carburization according to the present invention until the complete reaction for at least 90% by volume of the material to be reacted in the solid phase are, however, significantly lower than those of the known processes. This results in a significantly higher economy of the method in comparison with the known prior art.
  • the cost advantages of the method in question increase because of the comparatively simple construction of cyclone reaction chambers and because of the comparatively cheaper energy and gas consumption data.
  • Metal oxides, or standard compounds which are alternatively available for the reduction to metal powder are usually provided in particle sizes between approximately 2 and 30 ⁇ m and, according to the method according to the invention, give metal powders with a particle size approximately comparable to the starting powder size, but with a significant proportion of agglomerated powders. Agglomerated powders are generally not a good starting point for the production of extremely fine-grained carbide. It was completely surprising, however, that the metal powders produced by chemical reduction according to the present invention consistently have an extremely high, sponge-like microporosity in the range of 0.1 ⁇ m. However, this means that the metal powder for further processing to carbide and hard metal has a quality that has previously only been known to a certain extent called nanophase method was known ago. The entire volume of the metal powder can be completely carburized in a cyclone reaction and leads to a previously unattainable, fine-grained hard metal quality.
  • the throughput time of the material to be reacted in the solid phase is 0.2 to 10 s, with complete chemical conversion into the predetermined reaction state for at least 90% by volume of the solid phase.
  • the individual chemical process step in the cyclone is optionally repeated in at least one further run.
  • metal filler materials in particular the metals Co and / or Ni used in hard metal as binder metal, are added to the metal oxide powder or the powdery metal compound as the material to be reduced before the reduction step. This is done by adding metallic powders, or by preparing a solid solution beforehand, i.e. by introducing the filler materials into the solid phase of the material to be reduced.
  • the following variants result for the method according to the invention, which comprises several partial steps, for producing powder press batches for further processing into fine-grained hard metal.
  • a first process variant of the process according to the invention consists in the reduction of metal oxide or of comparable metal compounds to metal powder in the cyclone by the cyclone process; in the case of high purity requirements for the metal powder to be produced, also in a repetition of this reduction step.
  • the metal powder obtained in this way is then used in a ball mill with carbon particles which is frequently used in hard metal production intimately mixed. Agglomerates of the sponge-like metal powder are crushed. In this mixing and grinding process, powdered additional metals (to form mixed carbides as grain growth inhibitors in the hard metal) are preferably added.
  • the powder mixture is further converted to metal carbide in the carburizing furnace by customary methods, mixed with the binder metal (cobalt and / or nickel powder) by customary standard methods and optionally converted into a ready-to-press powder batch by attritor grinding and spray drying.
  • the powder press batch obtained in this way can be processed to very fine-grained hard metal with very high phase homogeneity by means of conventional pressing and sintering processes.
  • the metal oxides are reduced to metal powder in the cyclone, as above.
  • the metal powder obtained in this way is also further processed in the cyclone to metal carbide by the cyclone process which is essential to the invention, namely in two sub-variants, either following prior external mixing with carbon particles (as above) by simultaneously blowing this mixture together with carrier gas and possibly with reaction gas into the reaction chamber, or according to a second sub-variant, by directly blowing the metal powder into the cyclone reactor together with gaseous carbon compounds, in particular hydrocarbon gases and / or CO.
  • This variant is also supplemented by customary grinding, mixing and granulating processes, with grinding and granulating processes not necessarily having to take place.
  • the metal oxides are admitted or blown into the cyclone reaction chamber together with a reducing gas and a carbon-containing gas, and the oxide is first reduced during a single overall run in a first part of a spatially uniform overall reactor Metal powder and immediately afterwards in a second chamber part the carburization of the reduced metal powder to metal carbide.
  • additional metals for mixed carbide formation such as niobium, tantalum, vanadium and chromium, can also be added to the carburizing process in the cyclone and simultaneously converted to carbides with the main metal.
  • additional metals for mixed carbide formation such as niobium, tantalum, vanadium and chromium, can also be added to the carburizing process in the cyclone and simultaneously converted to carbides with the main metal.
  • a cyclone with the features of the present invention and corresponding to the representation in FIG. 1 is used as the device for carrying out the reduction process.
  • the overall system shown in FIG. 1 is composed of a steel reaction chamber designed as a cyclone, which is followed by a second reaction chamber designed as a downpipe for chemical aftertreatment of the reacted material, this aftertreatment and the associated reaction chamber not being part of the invention. It is a pilot plant that is smaller in comparison to plants for industrial production in terms of the throughput quantity of goods to be reduced per unit of time.
  • powdered W 4 O 11 is blown in via a feed device (1) together with reaction and / or carrier gas into the head part of a reaction chamber (2) which is approximately rotationally symmetrical with respect to the direction of fall.
  • the amount of gas is metered by means of a flow meter (7).
  • the reaction chamber is brought to a reaction temperature of 1100 ° C. by means of an electrical heating device (6).
  • the pulverulent reaction product leaves the chamber at the lower end, falls into a storage room with a screw conveyor (3) and is transferred to the second one Reaction chamber (4) with heating device (6) initiated.
  • the exhaust gas (8), reaction and / or carrier gas and H 2 O vapor as the end product of the reaction leave the first chamber at the top.
  • the tungsten powder is collected in a container (5).
  • the temperature of the entire two-stage process is controlled by means of a thermocouple (9) at the exhaust outlet of the first reaction chamber.
  • a gas amount of 4000 l H 2 gas is used, ie a large excess of gas based on the stoichiometric reaction amounts.
  • Tungsten oxide as the material to be reduced and H 2 as the carrier or reducing gas are fed to the cyclone separately.
  • the carrier or reducing gas is preferably introduced horizontally into the chamber at the upper end at a high flow rate.
  • the pulverulent material to be reduced is brought up to the gas inlet nozzle in such a way that it is entrained by the gas jet as it enters the chamber, is swirled and mixed intensively with it, and passes through the chamber in accordance with the guidance of the gas flow on predetermined trajectories.
  • the material reduced to tungsten powder leaves the reduction chamber after a passage time of 1-2 s and has a residual oxygen content of 10,500 ⁇ g / g at the outlet.
  • the emerging tungsten powder has a grain size of the order of 20 ⁇ m in diameter comparable to the let-in powder, although the individual powder particles or grains have a large porosity throughout their entire volume.
  • the spatial expansion of the substructure in the tungsten particle is 0.1 ⁇ m.
  • the cyclone reduction process is repeated once for the production of high-purity tungsten powder with a very low residual oxygen content.
  • the tungsten powder obtained in this way is converted into carbide by customary methods.
  • the tungsten powder is first intensively mixed in the ball mill with a stoichiometric proportion of fine soot particles for tungsten carbide, WC. Individual agglomerates of the tungsten powder are crushed.
  • the batch obtained in this way is carburized in a graphite furnace with induction heating under an H 2 atmosphere at 1300 ° C. for 3 hours. Pure tungsten carbide with a carbon content of 6.12% and a residual oxygen content of 1200 ⁇ g / g is formed.
  • the carbide is mixed with binder metal and usual amounts of mixed carbides (niobium carbide, tantalum carbide) and optionally processed into free-flowing granules by attritor grinding and spray drying.
  • mixed carbides niobium carbide, tantalum carbide
  • Tungsten carbide samples produced from such powder batches by means of pressing and sintering according to customary methods have exceptionally large fine-grain size with a very homogeneous carbide structure.
  • the device used corresponds to that of Example 1 without a downpipe being connected downstream of the cyclone.
  • Tungsten oxide, blue is reduced to tungsten powder in the cyclone in accordance with the process conditions mentioned in Example 1.
  • the tungsten powder is then further processed in a graphite-lined cyclone reactor with the aid of carbon-containing gases plus carrier gas (CH 4 / H 2 mixture) to form tungsten carbide.
  • Carburization takes place in one step at a cyclone temperature of 1100 ° C.
  • a gas throughput of 6000 l / h is regulated for a tungsten powder throughput of 1000 g / h.
  • the methane concentration in the CH 4 / H 2 mixture is 1.1% by volume.
  • ready-to-press powder batches are produced by mixing the WC with binder material and small proportions of mixed carbides with optional granulation by means of spray drying.
  • the hard metal obtained from these powder batches corresponds in its fine-grained structure and homogeneity to that according to Example 1.
  • the subsequent carburization is again carried out in the cyclone reactor, but in contrast to Example 2, using CO as the carburizing and carrier gas.
  • the tungsten powder obtained from the cyclone reactor is continuously introduced into the chamber at a throughput of 1000 g / h with a gas quantity of 6000 l / h (CO gas) and at 1000 ° C. chamber temperature in a one-step process to produce W 2 C and WC (C content 4.2% by weight) and a residual oxygen content of 3240 ⁇ g / g.
  • the X-ray diffractometer examination shows that in addition to W 2 C, small amounts of WC but no free carbon are present in the end product obtained in this way.
  • the throughput time for the particles to be carburized in the cyclone reactor is 1-2 s.
  • the W 2 C-WC powder mixture obtained in this way is reacted in a second process step in the cyclone under approximately the same test conditions as for the first carburization step to pure tungsten carbide WC with only a very small residual oxygen content and without detectable free carbon residues.
  • the powder sets are completed by mixing and optionally granulating as in Examples 1 and 2.
  • a hard metal made from these powder batches by customary processes has a high degree of fine grain and a high degree of material homogeneity.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Carbon And Carbon Compounds (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Powder Metallurgy (AREA)
EP97203354A 1996-11-04 1997-10-29 Procédé de préparation de poudre de départ pour matériau dur à grain fin Expired - Lifetime EP0839920B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
AT0191296A AT404912B (de) 1996-11-04 1996-11-04 Verfahren zur herstellung von pulver-pressansätzen für feinkörniges hartmetall
AT1912/96 1996-11-04
AT191296 1996-11-04

Publications (3)

Publication Number Publication Date
EP0839920A2 true EP0839920A2 (fr) 1998-05-06
EP0839920A3 EP0839920A3 (fr) 2000-03-29
EP0839920B1 EP0839920B1 (fr) 2002-12-18

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EP97203354A Expired - Lifetime EP0839920B1 (fr) 1996-11-04 1997-10-29 Procédé de préparation de poudre de départ pour matériau dur à grain fin

Country Status (6)

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US (1) US6113668A (fr)
EP (1) EP0839920B1 (fr)
JP (1) JPH10140216A (fr)
AT (2) AT404912B (fr)
DE (1) DE59709001D1 (fr)
ES (1) ES2186840T3 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114853021A (zh) * 2022-05-23 2022-08-05 赣州海盛钨业股份有限公司 纳米碳化钨粉末及其制备方法

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US6843824B2 (en) * 2001-11-06 2005-01-18 Cerbide Method of making a ceramic body of densified tungsten carbide
JP4619907B2 (ja) * 2005-09-20 2011-01-26 中外炉工業株式会社 粉体製造装置
US20130209308A1 (en) * 2012-02-15 2013-08-15 Baker Hughes Incorporated Method of making a metallic powder and powder compact and powder and powder compact made thereby
JP2013222497A (ja) * 2012-04-12 2013-10-28 Toshiba Corp 真空バルブ用接点材料
CN112390261A (zh) * 2019-08-13 2021-02-23 斯特里特技术有限公司 气相二氧化硅颗粒分离脱氢的系统和方法

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US5125964A (en) * 1990-09-10 1992-06-30 General Electric Company Fluidized bed process for preparing tungsten powder
WO1997016275A1 (fr) * 1995-10-31 1997-05-09 Plansee Aktiengesellschaft Procede de reduction de composes metalliques

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FR941412A (fr) * 1945-06-27 1949-01-11 Pluro Inc Réduction des oxydes métalliques
US5125964A (en) * 1990-09-10 1992-06-30 General Electric Company Fluidized bed process for preparing tungsten powder
WO1997016275A1 (fr) * 1995-10-31 1997-05-09 Plansee Aktiengesellschaft Procede de reduction de composes metalliques

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Publication number Priority date Publication date Assignee Title
CN114853021A (zh) * 2022-05-23 2022-08-05 赣州海盛钨业股份有限公司 纳米碳化钨粉末及其制备方法

Also Published As

Publication number Publication date
DE59709001D1 (de) 2003-01-30
ES2186840T3 (es) 2003-05-16
ATE230038T1 (de) 2003-01-15
ATA191296A (de) 1998-08-15
EP0839920A3 (fr) 2000-03-29
AT404912B (de) 1999-03-25
JPH10140216A (ja) 1998-05-26
US6113668A (en) 2000-09-05
EP0839920B1 (fr) 2002-12-18

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