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WO2024180901A1 - Poudre de tungstène et méthode de fabrication de produit de carbure de tungstène - Google Patents

Poudre de tungstène et méthode de fabrication de produit de carbure de tungstène Download PDF

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Publication number
WO2024180901A1
WO2024180901A1 PCT/JP2023/047329 JP2023047329W WO2024180901A1 WO 2024180901 A1 WO2024180901 A1 WO 2024180901A1 JP 2023047329 W JP2023047329 W JP 2023047329W WO 2024180901 A1 WO2024180901 A1 WO 2024180901A1
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tungsten
adsorbent
powder
tungsten carbide
tungsten powder
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Japanese (ja)
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貴彦 牧野
直樹 岩井
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Kyocera Corp
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Kyocera Corp
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Priority to CN202380094559.2A priority Critical patent/CN120659758A/zh
Priority to JP2025503607A priority patent/JPWO2024180901A1/ja
Publication of WO2024180901A1 publication Critical patent/WO2024180901A1/fr
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/949—Tungsten or molybdenum carbides
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/56—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides

Definitions

  • This disclosure relates to a method for producing tungsten powder and tungsten carbide products for use in the manufacture of cutting inserts and the like.
  • Tungsten powder is used in the manufacture of tungsten carbide products such as cutting inserts.
  • tungsten carbide products can be manufactured by mixing this tungsten carbide powder with cobalt powder, forming it into a predetermined shape, and then firing the formed body produced by this forming.
  • Patent Document 2 there is an increasing need to recycle tungsten in tungsten carbide products.
  • tungsten carbide powder usually contains various impurities in addition to the main component tungsten carbide.
  • the content ratio of these impurities affects the performance of products manufactured from the tungsten carbide powder.
  • the tungsten powder according to one embodiment of the present disclosure is a tungsten powder containing tungsten carbide as the main component, oxygen, and nitrogen, and the oxygen content by mass percentage is smaller than the nitrogen content.
  • FIG. 1 is a flow chart outlining a method for producing tungsten carbide powder according to one non-limiting example of the present disclosure.
  • FIG. 2 is a flow chart showing an outline of an example of a conventional method for producing tungsten carbide powder.
  • FIG. 3 is a flow chart showing an outline of an example of a conventional method for producing tungsten carbide powder.
  • Tungsten powder is used in the manufacture of tungsten carbide products such as cutting inserts.
  • tungsten carbide products can be manufactured by mixing this tungsten carbide powder with cobalt powder, forming it into a predetermined shape, and then firing the formed body produced by this forming.
  • Patent Document 2 there is an increasing need to recycle tungsten in tungsten carbide products.
  • tungsten carbide powder usually contains various impurities in addition to the main component tungsten carbide.
  • the content ratio of these impurities affects the performance of products manufactured from the tungsten carbide powder.
  • the tungsten carbide powder refers to a powder mainly composed of tungsten carbide, and the term "main component" means that tungsten carbide is the most abundant component in terms of mass% among the components contained in the powder. Specifically, tungsten carbide is contained in an amount of 99% by mass or more, while the remaining portion contains other elements. Examples of other elements include carbon, hydrogen, nitrogen, oxygen, chromium, vanadium, tantalum, niobium, titanium, etc. More specifically, the powder may contain 99.2% by mass or more of tungsten carbide, and may substantially not contain at least one carbide, nitride, or carbonitride selected from the group IVa, Va, and VIa elements, excluding W.
  • the tungsten carbide powder shown in this embodiment contains oxygen and nitrogen.
  • the oxygen content by mass is smaller than the nitrogen content by mass.
  • the performance of the product using the tungsten carbide powder may be affected.
  • the WC in the tungsten carbide powder may react with oxygen, causing the WC to change to W2C , W, WO3 , or the like. If the composition changes to these, it may become difficult to obtain the properties of WC, or the liquid phase appearance temperature may increase, making sintering difficult. Furthermore, the WC content in the tungsten carbide product after sintering may decrease, making it difficult to obtain the original properties.
  • cobalt functions as a binder. If tungsten carbide powder with a high oxygen content is used, there is a risk that the cobalt will react with oxygen to produce cobalt oxide. As a result, the binding function of cobalt will be reduced, and the characteristics of the cutting insert (such as Vickers hardness) may be reduced.
  • the WC particles repel each other, making it easier to obtain a uniform and fine-grained structure when they are rearranged during the sintering process.
  • the oxygen content and nitrogen content in the tungsten carbide powder can be evaluated, for example, by the SEM-EDX method using an energy dispersive X-ray spectrometer (EDX) attached to a scanning electron microscope.
  • the oxygen content ratio and nitrogen content ratio can be calculated as the oxygen content (mass%) and nitrogen content (mass%) in the entire tungsten carbide powder, respectively.
  • the nitrogen content in the tungsten carbide powder may be 0.1 mass% or more.
  • the nitrogen content is relatively high, so that it is easier to obtain the grain growth inhibition effect and/or the grain structure uniformity effect.
  • the oxygen content in the tungsten carbide powder may be 0.05% by mass or more.
  • affinity with the solvent is ensured and efficient mixing is possible, and the cemented carbide made from the obtained powder tends to have a uniform composition and structure.
  • cohesiveness of cobalt is also likely to be improved.
  • the oxygen content in the tungsten carbide powder may be 0.3 mass% or less.
  • a reaction between the carbon of the tungsten carbide in the tungsten powder and oxygen is less likely to occur, and the risk of a decrease in the carbon content in the tungsten carbide product after sintering can be reduced.
  • the average particle size of the tungsten carbide particles that make up the tungsten carbide powder may be 0.8 ⁇ m or less. In such a case, the small particle size makes it easier to obtain a cemented carbide alloy with high hardness and strength.
  • the average particle size may be, for example, the total area of tungsten particles in a cross-sectional view of the tungsten powder photographed with a scanning electron microscope (SEM) divided by the number of tungsten particles in the cross-sectional view.
  • SEM scanning electron microscope
  • the tungsten powder may have first particles and second particles having a larger particle size than the first particles.
  • ⁇ 1 may be larger than ⁇ 2.
  • the first particles have a smaller particle size and a larger specific surface area than the second particles. Therefore, even if the oxygen content ratio in the first particles and the second particles is the same, the oxygen contained in the first particles is more likely to affect the surrounding components than the second particles. For example, in products containing tungsten carbide and cobalt, the cobalt may be more likely to oxidize.
  • the oxygen content ratio in both the first and second particles is small, i.e., that both ⁇ 1 and ⁇ 2 are large.
  • simply reducing the oxygen content ratio in both the first and second particles may lead to an increase in manufacturing costs.
  • ⁇ 1 is greater than ⁇ 2, i.e., when the oxygen content in the first particles is relatively small, it is possible to efficiently suppress the effect of the oxygen contained in the tungsten carbide powder on the surrounding components while keeping the manufacturing costs of the tungsten carbide powder low.
  • a particle in the tungsten carbide powder may have two regions separated by a midpoint locus that connects the surface of the particle to the center of the particle.
  • the region located on the surface side may be called the surface region
  • the region located on the center side may be called the center region.
  • the nitrogen content in the surface region may be greater than the nitrogen content in the center region. In such a case, carbonitrides/nitrides are more likely to be formed, making it easier to obtain the grain growth inhibition effect and/or the grain structure uniformity effect.
  • the nitrogen content in the surface region may decrease as it approaches the central region.
  • carbonitrides/nitrides are more likely to form, so that the grain growth inhibition effect and/or grain structure uniformity effect are more likely to be obtained.
  • the nitrogen content does not change suddenly, the tungsten carbide powder is more likely to be chemically stable.
  • the tungsten carbide powder may contain nitrogen in the central region.
  • the nitrogen is uniformly distributed in the tungsten carbide powder, and the tungsten carbide powder is more likely to be chemically stable than when nitrogen is contained only in the surface region.
  • the nitrogen content ratio in the surface region and the nitrogen content ratio in the central region may be compared by mapping a cross-sectional view of the tungsten carbide powder photographed with an SEM.
  • ⁇ When the nitrogen content ratio/oxygen content ratio in the tungsten carbide powder is taken as the content ratio ⁇ , ⁇ may be 1.2 or more. In such a case, the nitrogen content ratio becomes relatively high, so that the grain growth inhibition effect and/or grain structure uniformity effect are more easily obtained.
  • Method of production A method for producing (producing) tungsten powder according to one non-limiting example of the present disclosure will be described.
  • a method for producing tungsten powder includes the following steps (A) to (G).
  • A) a step of preparing a raw material containing tungsten;
  • B) a step of oxidizing tungsten in the raw material to obtain tungsten oxide;
  • C) a step of obtaining a solution by dissolving tungsten oxide from the raw material using an alkaline solvent;
  • D) a step of adding a metal compound adsorbent (hereinafter sometimes referred to as an adsorbent) to the solution, reacting the adsorbent with the solution containing the dissolved tungsten, and obtaining a compound containing the adsorbent and tungsten;
  • E) a step of extracting the compound from the solution;
  • F) a step of mixing the compound with carbon powder to produce a mixture;
  • G) a step of heating the mixture.
  • a raw material containing tungsten is prepared.
  • the raw material include ores and scraps containing tungsten.
  • ores containing tungsten include scheelite (CaWO 4 ), wolframite (MnWO 4 ), ferrite (FeWO 4 ), and wolframite ((Fe,Mn)WO 4 ).
  • Scraps containing tungsten are waste materials generated in the production process of products mainly composed of metal tungsten, tungsten carbide (WC), and the like. Specifically, scraps generated in the manufacturing process of cemented carbide tools, hard scraps such as used tools, powdery soft scraps such as grinding sludge, and the like can be cited.
  • Cemented carbide a type of cemented carbide, is mainly composed of composite carbides such as metal tungsten and tungsten carbide.
  • This composite carbide-based component has iron, nickel, cobalt, etc. as a binder phase, and may contain TiC, TaC, NbC , VC, Cr3C2 , etc. as additive components as necessary.
  • Targeted materials containing cemented carbide include cutting tools (cutting inserts, drills, end mills, etc.), dies (forming rolls, forming dies, etc.), civil engineering and mining tools (oil drilling tools, rock crushing tools, etc.), etc.
  • Process B When tungsten is contained in the raw material in a non-oxide state, the tungsten in the raw material is oxidized to obtain tungsten oxide.
  • the cutting tool when preparing a used cutting tool as the raw material, the cutting tool contains tungsten in the form of tungsten carbide. Therefore, the tungsten carbide is oxidized to obtain tungsten oxide.
  • a method for oxidizing tungsten includes, for example, oxidizing roasting.
  • a cutting tool containing tungsten carbide and cobalt is oxidizing roasted to obtain a mixture of tungsten oxide (WO 3 ) and cobalt tungstate (CoWO 4 ).
  • steps A and B since the purpose of steps A and B is to obtain tungsten oxide from raw materials, these steps may be collectively expressed as a process for preparing raw materials containing tungsten oxide.
  • the recovery method includes an alkali extraction/alkali fusion process in which the metal components of the cemented carbide scrap are dissolved in an alkali solution to obtain a tungsten compound solution in which tungsten compound ions are dissolved.
  • Methods for obtaining a metal compound solution include an alkali extraction method and an alkali fusion method.
  • the alkali extraction method is a method in which scrap that has been previously oxidized and roasted is subjected to alkali extraction using, for example, an aqueous NaOH solution.
  • the alkali dissolution method is a method in which the scrap is oxidized and dissolved at the same time using a molten salt of a sodium salt such as NaNO3, Na2SO4, Na2CO3 , or NaOH .
  • soft scrap is highly reactive and difficult to control, so it is more efficient to use the alkaline extraction method, while hard scrap is more efficient to use the alkaline dissolution method, because only the surface can be oxidized by oxidizing roasting.
  • the adsorbent of this embodiment is added to the tungsten compound solution obtained in step C.
  • the adsorbent of this embodiment adsorbs the metal compound present as an anion in the solution.
  • the adsorbent of this embodiment for example, the first adsorbent and/or the second adsorbent shown below can be used.
  • the first adsorbent contains at least one first amino acid selected from alanine, cystine, methionine, tyrosine, lysine, valine, glutamic acid, histidine, proline, threonine, asparagine, glycine, isoleucine, ornithine, arginine, serine, citrulline, and cystathionine as a free amino acid.
  • the first adsorbent may contain 10 mol% or more of the first amino acid as a free amino acid (sometimes called the first free amino acid) with respect to the total amount of free amino acids.
  • the free amino acids in the adsorbent may exist as a solid, or may exist as free amino acids when dissolved in solution. In either case, the solution contains free amino acids, and by using these adsorbents, metal compounds can be recovered through a simple processing process.
  • the first adsorbent is a substrate having free amino acids supported on its surface.
  • the substrate can be, for example, a peptide containing free amino acids, a protein, or a substance that forms a living organism such as a microorganism (hereinafter sometimes referred to as a biological substance), an organic substance such as a resin, or an inorganic substance.
  • Microorganisms include bacteria such as E. coli (Escherichia coli), Bacillus sp., Thiobacillus ferrooxidans, Streptomyces rimosus, Pseudomonas sp., Bacillus thuringiensis, Arthrobacternicotianae, Shewanella algae, and Shewanella oneidensis, yeasts such as Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida albicans, Yarrowialipolytica, Pichiapastoris, Hansenula polymorpha, and Kluyveromyces lactis, and koji mold.
  • bacteria such as E. coli (Escherichia coli), Bacillus sp., Thiobacillus ferrooxidans, Streptomyces rimosus, Pseudomonas sp., Bacillus thuringiensis, Arthrobacternicotianae, Shewanella algae
  • Adsorbents made from biological substances come in various forms, such as powders, pellets made from powders, gels, and aqueous solutions. Powders and pellets are easy to store and handle. If the adsorbent is a solid such as a powder or pellets, the solid can be dissolved in another liquid such as water and then added to a solution containing the metal compound, or the solid can be added directly to a solution containing the metal compound and stirred.
  • the first adsorbent may contain, as free amino acids, at least one of the first amino acids alanine, cystine, methionine, tyrosine, lysine, valine, glutamic acid, histidine, and proline (hereinafter, sometimes referred to as the 1-1 amino acid), at least one of the first amino acids threonine, asparagine, glycine, isoleucine, ornithine, and arginine (hereinafter, sometimes referred to as the 1-2 amino acid), and at least one of the first amino acids serine, citrulline, and cystathionine (hereinafter, sometimes referred to as the 1-3 amino acid).
  • the first adsorbent may contain, as free amino acids, at least one of the second amino acids phosphoserine, aspartic acid, leucine, and phenylalanine at a ratio of 40 mol% or less to the total amount of free amino acids.
  • An adsorbent containing the 1-1 amino acid, the 1-2 amino acid, and the 1-3 amino acid as free amino acids can increase the recovery efficiency of metal compounds.
  • the 1-1 amino acid may be contained in a ratio of 5 mol% or more as a free amino acid when the total amount of free amino acids is 100 mol%.
  • lysine may be contained in a ratio of 10 mol% or more as a free amino acid.
  • the recovery efficiency of metal compounds is improved.
  • the total amount of the 1-1 amino acid contains 10 mol% or more as a free amino acid. This improves the recovery efficiency of metal compounds.
  • the total amount of free amino acids consisting of the first amino acid may be 0.5% by mass or more relative to the total amount of solids obtained by drying the adsorbent, i.e., the solid content of the adsorbent. In such a case, the recovery efficiency of the metal compound is improved.
  • the free amino acids contain aspartic acid and at least one of glutamic acid and valine as free amino acids
  • the content of at least one of glutamic acid and valine may be greater than that of aspartic acid.
  • the free amino acids consisting of glutamic acid and valine have a positive zeta potential when the pH of the solution is adjusted to the acidic side, and adsorb metal compound ions (anions) in the solution.
  • aspartic acid has a low ability to adsorb metal compounds (ions). Therefore, when the content of at least one of glutamic acid and valine in the free amino acids is greater than the content of aspartic acid, the adsorption efficiency of metal compounds can be improved.
  • the type and content of free amino acids contained in the adsorbent can be confirmed by free amino acid analysis (also called bioamino acid analysis).
  • the content ratio of the total amount of free amino acids to the solid content of the adsorbent can be calculated from the mass of the free amino acids in the adsorbent and the mass of the solid content of the adsorbent.
  • the adsorbent is a solid such as a powder
  • the adsorbent is added to pure water at a liquid temperature of 25°C, and the adsorbent is suspended by stirring for 10 minutes while rotating a magnetic stirrer at a rotation speed of 500 rpm. Free amino acid analysis is performed using this suspension.
  • the adsorbent is a solution
  • free amino acid analysis is performed in the solution, and the total amount of free amino acids can be calculated from the mass of the solid content of the adsorbent obtained by centrifuging the adsorbent solution.
  • the mass of the solid content of the adsorbent is measured after it has been thoroughly dried under drying conditions such as 60°C for 24 hours.
  • the free amino acids contained in the biological material are supported on the surface of a substrate, which is a peptide or protein.
  • a substrate which is a peptide or protein.
  • the substrate may be a biological material, a resin or an inorganic material, but if it is a biological material, the free amino acids can be easily increased.
  • the free amino acids are supported on the body surface of a microorganism.
  • the base of the adsorbent is a resin or inorganic material
  • the base is in the form of a powder or porous body with a large specific surface area
  • a large number of free amino acids can be supported on the surface of the base.
  • amino acids can also be supported on the inner walls of the pores.
  • inactive amino acids When the adsorbent is made of a biological substance, in addition to free amino acids, there are amino acids that do not contribute to the adsorption reaction (hereinafter sometimes referred to as inactive amino acids).
  • inactive amino acids include amino acids that are located in the middle position of amino acids linked by peptide bonds, and amino acids that are located in the interior of the adsorbent and are not exposed on the surface.
  • the adsorbent When the adsorbent is made of a biological substance, it is effective to increase the content of free amino acids in the adsorbent by carrying out a process that breaks the peptide bonds of inactive amino acids present in the adsorbent and converts the inactive amino acids into free amino acids.
  • the peptide bonds present in the microorganism can be cleaved by existing processing methods.
  • the proteins that constitute the microorganism are decomposed with proteolytic enzymes such as trypsin, LYSYLENDOPEPTIDASE (registered trademark), and V8 Protease. This allows at least a portion of the inactive amino acids contained in the body of the microorganism to be converted into free amino acids.
  • a method for converting inactive amino acids into free amino acids a method in which the adsorbent is subjected to a heating treatment at 60°C or higher, a boiling treatment, or a heating and pressurizing treatment using an autoclave or the like to decompose the proteins is also effective.
  • the adsorbent is a living organism such as a microorganism and does not need to be stored in a solution, but can be stored as a solid like a decomposed inanimate object, then large-scale facilities for cultivation and storage and maintenance are not required, and the facilities can be made smaller.
  • the second adsorbent contains at least one first amino acid selected from the group consisting of alanine, cystine, methionine, tyrosine, lysine, valine, glutamic acid, histidine, proline, threonine, asparagine, glycine, isoleucine, ornithine, arginine, serine, citrulline, and cystathionine, and at least a portion of the first amino acid is present as a free amino acid in the solution.
  • the second adsorbent may also contain a total amount of the first amino acid in the form of free amino acid of 10 mol% or more relative to the total amount of free amino acids.
  • the second adsorbent exists as a solid and does not contain free amino acids in the solid state, but has free amino acids in solution.
  • An example of the second adsorbent is a salt of the first amino acid.
  • salts include hydrochloride, nitrate, sulfate, acetate, and carbonate.
  • An adsorbent made of an amino acid salt dissolves in a liquid to supply free amino acids. Then, similar to the first adsorbent, the adsorbent is added to a solution in which a metal compound has been dissolved, and the pH is adjusted so that the zeta potential of the free amino acid of the adsorbent is positive. At this time, the metal compound exists as an anion, and the anion of the metal compound is adsorbed to the positively charged free amino acid of the adsorbent.
  • the content ratio of free amino acids in the adsorbent can be made higher than in the case where free amino acids are supported on the surface of a substrate. This makes it possible to achieve high adsorption efficiency of metal compounds, and a large amount of metal compounds can be adsorbed with a small amount of adsorbent. In addition, when recovering metal compounds after adsorption, the content of unnecessary materials that need to be disposed of is small, making handling easy and reducing manufacturing costs. Furthermore, since the adsorbent is not a living organism like bacteria or microorganisms, it is easy to store and manage the adsorbent.
  • the second adsorbent which is an adsorbent made of salt, may be in the form of a solution, but is easier to handle, store, and manage if it is a solid, and is particularly easy to dissolve in a solution if it is in powder form.
  • the adsorbent may also be in the form of pellets to facilitate handling.
  • the adsorbent has good adsorption efficiency.
  • a salt containing lysine may be used as the adsorbent.
  • examples of salts containing lysine include lysine hydrochloride, lysine sulfate, lysine nitrate, and lysine acetate.
  • lysine hydrochloride for example, L-lysine hydrochloride
  • lysine hydrochloride is stable and inexpensive.
  • lysine hydrochloride is used as an adsorbent, it is difficult for unnecessary elements to be introduced during the acid treatment in the subsequent process.
  • “having at least one salt of lysine or arginine as the main component” means that the ratio of the total mass of the lysine salt or arginine salt in the adsorbent is 50 mass% or more relative to the total mass of the adsorbent.
  • the total amount of the lysine salt and the arginine salt present in the adsorbent is preferably 90% by mass or more. This allows a large amount of metal compound to be adsorbed with a small amount of adsorbent. A more preferable range for the total amount of the lysine salt and the arginine salt present in the adsorbent is 95% by mass or more.
  • the cost of the adsorbent can be reduced by including a salt of glutamic acid as the salt of the first amino acid.
  • a salt of glutamic acid as the salt of the first amino acid.
  • sodium glutamate is stable and inexpensive.
  • the content of glutamic acid salts in the adsorbent is preferably 90% by mass or more. This allows the metal compounds to be recovered inexpensively.
  • the preferred range for the total amount of glutamic acid salts in the adsorbent is 95% by mass or more.
  • the free amino acid is not limited to one type.
  • salts of other first amino acids such as lysine and arginine, can be added along with the salt of glutamic acid.
  • the adsorbent when the adsorbent is made of a microorganism, the adsorbent is added so that 1 g to 10 kg is added per 1 m3 of a tungsten compound solution in which the tungsten concentration is adjusted to 0.1 to 10 mmol/l (tungsten concentration is 0.1 to 10 mmol per 1 liter of alkaline solution).
  • the adsorbent is made of a salt of a first amino acid
  • the total amount of the salt of the first amino acid added in the adsorbent is added at a content ratio of 0.2 to 1.1 mol per mol of the metal component of the metal compound. This allows a large amount of metal compound such as a tungsten compound to be adsorbed with a small amount of adsorbent.
  • the total amount of the salt of the first amino acid added may be 10 to 300 g/l of the metal compound solution. In such a case, the viscosity of the solution does not increase, and the recovery efficiency of the metal compound is less likely to decrease. In particular, when the adsorbent is made of a salt of an amino acid, the viscosity of the solution does not increase easily, and workability is good.
  • the temperature can be adjusted according to the activity of the free amino acid, and can usually be room temperature.
  • the tungsten compound solution with added adsorbent is adjusted using hydrochloric acid or the like so that the zeta potential of the free amino acid is positive. This causes the adsorbent to adsorb the anionic tungsten compound ions.
  • the pH of the solution is less than 7 (acidic).
  • the free amino acids are lysine and arginine
  • the preferred pH is 4 or less, preferably 1 to 3, and more preferably 1 to 2.3.
  • the free amino acid is glutamic acid
  • the preferred pH is 1.5 or less. This can increase the recovery rate of the tungsten compound. Note that the step of adjusting the pH of the solution and the step of adding an adsorbent to the solution containing the metal compound can be carried out in any order.
  • the recovery efficiency of the adsorbent is higher if the adsorption reaction lasts for less than one hour. In other words, if the adsorption reaction lasts for more than one hour, some of the adsorbed metal compound may be released from the free amino acid.
  • removing includes a step of filtering the compound from the solution and a step of drying and powdering the compound recovered by filtering.
  • the adsorbent that has adsorbed tungsten compound ions is filtered with filter paper or the like to recover the compound in a slurry form on the filter paper.
  • the recovered compound is then dried and powdered to extract the tungsten compound containing the powdered adsorbent.
  • the tungsten compound containing the adsorbent refers to, for example, lysine- WO4 when the adsorbent is lysine.
  • FG process A predetermined amount of carbon powder (carbon black, graphite powder, activated carbon, etc.) or carbon slurry is added as a reducing agent to the extracted tungsten compound and mixed (step F). Then, this mixture is heated to 1100 to 2000°C under a predetermined atmosphere and held for a predetermined time, thereby performing a carbonization treatment, and a tungsten powder mainly composed of tungsten carbide can be obtained (step G).
  • the above-mentioned predetermined atmosphere may be, for example, a reducing atmosphere containing carbon monoxide, nitrogen, hydrogen, methane, etc.
  • the carbonization process is performed in a mixed atmosphere containing nitrogen and hydrogen as the main components.
  • the mixed atmosphere contains nitrogen and hydrogen as the main components
  • the production costs are reduced compared to when nitrogen and hydrogen are treated separately in their respective atmospheres.
  • main component means that, among the components contained in the gas, nitrogen and hydrogen are more abundant in mole percent than the components other than nitrogen and hydrogen. More specifically, this refers to the case where the proportions of nitrogen and hydrogen are 40 mole percent or more and 10 mole percent or more, respectively.
  • the powder extracted in the E step is incinerated to remove the adsorbent, and WO3 is extracted.
  • Metallic tungsten is extracted by removing oxygen from this WO3 through a reduction process.
  • tungsten carbide powder is obtained by carbonizing this metallic tungsten.
  • the process of removing the adsorbent and extracting WO3 requires incineration at a temperature of 300 (°C) or higher, and the reduction process of WO3 requires heat treatment at a temperature of 800 (°C) to 950 (°C) in a reducing atmosphere (for example, a hydrogen gas atmosphere). Therefore, a large burden was required to produce tungsten carbide powder.
  • the tungsten compound extracted in the above-mentioned E step is directly carbonized to produce WC without going through the above-mentioned oxidation and reduction treatments. This reduces the burden of producing tungsten carbide powder. Furthermore, when carbonizing the above-mentioned tungsten compound, carbon powder is mixed in to produce a mixture, and this mixture is then heated.
  • the carbon component contained in the adsorbent can be used to carbonize tungsten to obtain WC.
  • the carbon component contained in the adsorbent alone is likely to be insufficient in the G step of carbonizing tungsten, and therefore not only WC but also W2C is likely to be produced in this G step.
  • step F of the production method of this embodiment since carbon powder is mixed with the tungsten compound, the above-mentioned carbon shortage is eliminated, W 2 C is less likely to be produced, and it is possible to produce WC powder with high purity.
  • the amount of carbon powder added in the step F may be adjusted so that the carbon content in the mixture is 5 mass% or more. In this case, tungsten is easily and stably carbonized in the step G, so that W2C is not easily generated and WC is easily generated.
  • the amount of carbon powder added in step F may be adjusted so that the carbon content in the mixture is 6% by mass or less.
  • the more carbon there is in the mixture the more stable the carbonization of tungsten becomes.
  • the process of removing the excess carbon that has not bonded with tungsten after step G may become complicated.
  • the carbon content in the mixture is 6% by mass or less, the load required to remove the excess carbon is small.
  • the amount of carbon powder may be adjusted taking into account the amount of carbon components contained in the adsorbent.
  • the carbon components in tungsten carbide may not only be derived from the carbon powder, but may also be derived from the carbon components in the adsorbent. In other words, the carbon in the tungsten powder may contain the carbon in the adsorbent. If the adsorbent is an organic material as described above and contains carbon, and the carbon in the tungsten powder contains the carbon in the adsorbent, the amount of carbon powder added in step F can be reduced.
  • the hydrogen content may be less than or equal to that of nitrogen. If there is less hydrogen than nitrogen, coarse particles are less likely to form. Note that the nitrogen and hydrogen content ratios being approximately the same does not require them to be strictly the same. If the nitrogen content ratio/hydrogen content ratio is between 0.9 and 1.1, it is considered to be "approximately the same.”
  • the metal compound recovery method of this embodiment can reduce the number of steps, as well as the amount of chemicals used and waste liquid, making it possible to recover tungsten compounds at low cost.
  • the total amount of CO2 emitted by the process of the present application may be about 40% of the total amount of CO2 (energy equivalent) emitted by a conventional ion exchange method for producing tungsten carbide via ammonium paratungstate and W metal powder.
  • the nitrogen in the tungsten carbide powder may originate from the nitrogen in the adsorbent. In such a case, it is not necessary to add nitrogen to increase the nitrogen in the tungsten carbide powder, or the amount of nitrogen added can be reduced, thereby reducing production costs.
  • FIG. 1 shows tungsten carbide powder according to the embodiment
  • FIG. 2 is a flow chart showing an example of the steps of a manufacturing process for tungsten carbide powder according to a conventional embodiment.
  • scrap of cemented carbide is prepared in the manufacturing process for tungsten carbide powder according to the embodiment and the conventional embodiment.
  • Cemented carbide a type of hard alloy, is mainly composed of composite carbides such as metal tungsten and tungsten carbide, with iron, nickel, cobalt, etc. as a binder phase, and optionally containing TiC, TaC, NbC, VC, Cr3C2 , etc. as additive components.
  • the target materials containing cemented carbide include, for example, cutting tools (cutting inserts, drills, end mills, etc.), dies (forming rolls, forming dies, etc.), and mining and civil engineering tools (oil drilling tools, rock crushing tools, etc.).
  • the prepared cemented carbide scrap was oxidized and roasted to obtain a mixture of tungsten oxide (WO 3 ) and cobalt tungstate (CoWO 4 ).
  • the mixture was refluxed with an aqueous sodium hydroxide (NaOH) solution and then extracted to obtain a tungsten compound solution containing sodium tungstate (Na 2 WO 4 ).
  • the total amount of the salt of the first amino acid in the adsorbent is added in a content ratio of 0.2 (mol) to 1.1 (mol) per 1 (mol) of the metal component of the tungsten compound. This makes it possible to adsorb a large amount of tungsten compound with a small amount of adsorbent.
  • the total amount of the salt of the first amino acid added is, for example, 10 (g/l) to 300 (g/l) relative to the tungsten compound solution. This prevents the viscosity of the solution from increasing, and the recovery efficiency of the metal compound from decreasing. In particular, when the adsorbent is made of an amino acid salt, the viscosity of the solution is less likely to increase, and workability is good.
  • the temperature can be adjusted according to the activity of the free amino acid, and is usually room temperature.
  • the tungsten compound solution to which the adsorbent has been added can be adjusted using hydrochloric acid or the like so that the zeta potential of the free amino acid is positive. This allows the adsorbent to adsorb the anionic tungsten compound ions.
  • the pH of the solution may also be less than 7 (acidic).
  • the free amino acids are lysine and arginine
  • the preferred pH is 4 or less, preferably 0.5 to 3, and more preferably 0.8 to 2.3.
  • the free amino acid is glutamic acid
  • the preferred pH is 1.5 or less. In the examples, the pH was adjusted to 1.8.
  • the adsorbent that has adsorbed tungsten compound ions is filtered with filter paper or the like to recover the compound in a slurry form on the filter paper.
  • the recovered compound is then dried and powdered to extract the tungsten compound containing the powdered adsorbent.
  • the tungsten compound containing the adsorbent refers to lysine- WO4 , etc., since the adsorbent is lysine.
  • carbon black is added to and mixed with the recovered tungsten compound, and the mixture is heated for at least one hour in a mixed atmosphere of hydrogen gas and nitrogen gas (1-10 L/min) at a temperature as shown in Table 1, to directly carbonize the adsorbent with the tungsten compound ions adsorbed.
  • the carbon content of the carbon black was 5-6 mass% of the carbon content in the mixture.
  • the adsorbent with the tungsten compound ions adsorbed thereon was incinerated, for example, in the atmosphere at a temperature of 300° C. or higher to oxidize the tungsten compounds and remove the organic components including the adsorbent. This resulted in the production of a tungsten oxide powder (WO 3 ) according to the embodiment.
  • the obtained tungsten oxide powder is heat treated in a reducing atmosphere (for example, a hydrogen gas atmosphere) at a temperature of 800 (°C) to 950 (°C) to reduce the tungsten oxide compound.
  • a reducing atmosphere for example, a hydrogen gas atmosphere
  • metallic tungsten (W) metallic tungsten
  • carbon black is added to and mixed with the obtained metallic tungsten powder, and the mixture is heated and carbonized for at least one hour in a mixed atmosphere of hydrogen gas and nitrogen gas at a temperature as shown in Table 1, thereby obtaining tungsten carbide (WC), which is a raw material for conventional cemented carbide alloys.
  • Comparative Examples 1 and 2 in Table 1 show tungsten carbide powder produced by this production method.
  • (Manufacturing process in FIG. 3) 3 is a flow chart showing an example of a procedure for producing a tungsten carbide powder according to a conventional embodiment. As shown in FIG. 3, in the production process of tungsten oxide powder and tungsten carbide in the reference example, first, scrap of cemented carbide was prepared.
  • the prepared cemented carbide scrap was oxidized and roasted to obtain a mixture of tungsten oxide (WO 3 ) and cobalt tungstate (CoWO 4 ).
  • the mixture was then extracted with an aqueous solution of sodium hydroxide (NaOH) to obtain a tungsten compound solution containing sodium tungstate (Na 2 WO 4 ).
  • the obtained tungsten compound solution was subjected to ion exchange using an ion exchange resin or the like to produce an aqueous solution of ammonium tungstate ((NH 4 ) 2 WO 4 ).
  • the obtained aqueous solution was then heated and concentrated to crystallize the tungsten compound as ammonium paratungstate (APT).
  • carbon powder carbon black, graphite powder, activated carbon, etc.
  • a reducing atmosphere for example, a mixed atmosphere of hydrogen gas and nitrogen gas
  • tungsten carbide powder which is the raw material for cemented carbide.
  • Comparative Example 3 in Table 1 shows tungsten carbide powder produced by this production method.
  • the average particle size of tungsten particles in tungsten powder was measured by the following method. First, particles in any tungsten powder were observed in a SEM image (10,000 times) of a range of 10 ⁇ m ⁇ 10 ⁇ m. The total area of tungsten particles in the SEM image was divided by the number of tungsten particles in the SEM image.
  • the number of abnormally grown particles in the tungsten powder was measured by the following method. First, 10 random tungsten powders were selected. Then, each of these particles was observed in an SEM image (10,000 times) in the range of 10 ⁇ m ⁇ 10 ⁇ m. The number of particles with abnormal grain growth in the SEM image of each particle was measured, and the average value obtained by dividing the total number by 10 is shown in Table 1.
  • the particles with abnormal grain growth refer to tungsten particles that have an area three times or more larger than the value of (total area of tungsten particles)/(number of tungsten particles) in the SEM image of each tungsten powder.
  • the above cemented carbide was processed into a sample shape for three-point bending strength measurement in accordance with JIS R1601, and the three-point bending strength was measured, while the Weibull modulus was calculated in accordance with JIS R1625.
  • the tungsten carbide powder of the above embodiment can further improve the properties of tungsten carbide products made from it. More specifically, it can further improve the properties of cutting inserts made from the tungsten carbide powder.
  • tungsten carbide products a method for producing a tungsten carbide product according to a non-limiting example of the present disclosure will be described. Specifically, a method for producing a tungsten carbide product using tungsten carbide powder obtained by the production method of the present disclosure as a raw material will be described. Here, a method for producing a cutting insert using tungsten carbide powder obtained by the production method of the present disclosure as a raw material will be described in detail as an example.
  • a method for manufacturing a machined product includes the following steps (X) and (Y). (X) mixing tungsten carbide powder with cobalt powder to form a compact; (Y) firing the compact.
  • a suitable amount of cobalt powder is added to the tungsten carbide powder obtained by the production method disclosed herein.
  • metal powders other than cobalt powder and/or carbon powder may also be added.
  • the mixture is then wet mixed in a ball mill for a predetermined time, dried, and then molded into a predetermined tool shape using a known molding method such as press molding, casting, extrusion molding, or cold isostatic pressing to obtain a molded body.
  • the molded body is sintered in a vacuum or a non-oxidizing atmosphere to produce a cutting insert.
  • the surface of the produced cutting insert may be polished or honed.
  • the surface of the cutting insert may be coated with a coating by chemical vapor deposition (CVD) or physical vapor deposition ( PVD ) techniques, with coating compositions including titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina ( Al2O3 ).
  • CVD chemical vapor deposition
  • PVD physical vapor deposition
  • the tungsten powder (1) contains tungsten carbide as a main component, oxygen, and nitrogen, and the oxygen content by mass % may be smaller than the nitrogen content.
  • the nitrogen content in the tungsten powder may be 0.1 mass% or more.
  • the oxygen content in the tungsten powder may be 0.05 mass% or more.
  • the oxygen content in the tungsten powder may be 0.3 mass% or less.
  • the average particle size of the tungsten particles constituting the tungsten powder may be 0.8 ⁇ m or less.
  • the tungsten powder may have first particles and second particles having a particle size larger than the first particles, and when the content ratio ⁇ 1 is the nitrogen content ratio/oxygen content ratio in mass% in the first particles and the content ratio ⁇ 2 is the nitrogen content ratio/oxygen content ratio in mass% in the second particles, the content ratio ⁇ 1 may be greater than the content ratio ⁇ 2.
  • the tungsten powder may have a surface region and a central region located inside the tungsten powder relative to the surface region, and the nitrogen content in the surface region may be greater than the nitrogen content in the central region.
  • the nitrogen content in the surface region may decrease toward the central region.
  • the content ratio ⁇ may be 1.2 or more.
  • a method for producing a tungsten carbide product may include a step of mixing tungsten powder obtained by any one of the above tungsten powder production methods (1) to (9) with cobalt powder to form a molded body, and a step of sintering the molded body.
  • the invention according to the present disclosure has been described above based on the embodiments.
  • the invention according to the present disclosure is not limited to the above-mentioned embodiments.
  • the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure.
  • the above embodiment shows the case where tungsten oxide powder and tungsten carbide are produced (recycled) from scrap of cemented carbide, but the present disclosure is not limited to such an example and can also be applied when producing tungsten oxide powder and tungsten carbide from ore.

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Abstract

Une poudre de tungstène basée sur un aspect de la présente invention contient du carbure de tungstène en tant qu'ingrédient principal, de l'oxygène et de l'azote, et le rapport de teneur en oxygène est inférieur au rapport de teneur en azote en termes de % en masse.
PCT/JP2023/047329 2023-03-01 2023-12-28 Poudre de tungstène et méthode de fabrication de produit de carbure de tungstène Pending WO2024180901A1 (fr)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003206123A (ja) * 2002-01-16 2003-07-22 Mitsubishi Materials Corp 炭化タングステン基超硬合金製造用炭化タングステン基合金粉末
JP2007269534A (ja) * 2006-03-31 2007-10-18 Allied Material Corp Ｗｃ粉とその製造方法
JP2015040161A (ja) * 2013-08-23 2015-03-02 京セラ株式会社 タングステン化合物の回収方法
JP2015045041A (ja) * 2013-08-27 2015-03-12 京セラ株式会社 タングステン化合物の回収方法
JP2015098641A (ja) * 2013-10-18 2015-05-28 京セラ株式会社 タングステン化合物の回収方法
JP2022060899A (ja) * 2020-10-05 2022-04-15 株式会社Moldino 複合粒子、複合粉末ならびに複合粉末を用いた複合部材の製造方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003206123A (ja) * 2002-01-16 2003-07-22 Mitsubishi Materials Corp 炭化タングステン基超硬合金製造用炭化タングステン基合金粉末
JP2007269534A (ja) * 2006-03-31 2007-10-18 Allied Material Corp Ｗｃ粉とその製造方法
JP2015040161A (ja) * 2013-08-23 2015-03-02 京セラ株式会社 タングステン化合物の回収方法
JP2015045041A (ja) * 2013-08-27 2015-03-12 京セラ株式会社 タングステン化合物の回収方法
JP2015098641A (ja) * 2013-10-18 2015-05-28 京セラ株式会社 タングステン化合物の回収方法
JP2022060899A (ja) * 2020-10-05 2022-04-15 株式会社Moldino 複合粒子、複合粉末ならびに複合粉末を用いた複合部材の製造方法

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