Hard member, cutting insert, cutting tool, and method for manufacturing cut article

Abstract

This hard member has a base material that includes a hard phase and a binder phase. The hard phase contains tungsten carbide and nitrogen. The binder phase contains nitrogen and at least one iron group element that is selected from the group consisting of iron, cobalt, and nickel. The base material has an outer part that ranges from the surface to a depth of 1 mm, and an inner part that is located on a side further inward from the surface than the outer part in the thickness direction. When NOH (atm%) is the content ratio of nitrogen in the hard phase in the outer part and NIH (atm%) is the content ratio of nitrogen in the hard phase in the inner part, NOH is higher than NIH.

Description

Method for manufacturing hard member, cutting insert, cutting tool, and machined product

[0001] The disclosed embodiments relate to methods of manufacturing hard components, cutting inserts, cutting tools and machined workpieces.

[0002] BACKGROUND ART Hard members containing tungsten carbide in the hard phase have been widely used as substrates for members such as cutting tools that require high wear resistance.

[0003] Japanese Patent Application Laid-Open No. 2003-206123

[0004] A hard member according to one aspect of the embodiment has a substrate including a hard phase and a binder phase. The hard phase contains tungsten carbide and nitrogen. The binder phase contains at least one iron-group element selected from the group consisting of iron, cobalt, and nickel, and nitrogen. The substrate has an outer portion extending from the surface to a depth of 1 mm, and an inner portion located inside the outer portion in the depth direction from the surface. The nitrogen content ratio of the hard phase in the outer portion is defined as N ＯＨ [atm%], the nitrogen content in the hard phase in the inner part is N ＩＨ When expressed as [atm %], N ＯＨ is N ＩＨ is greater than.

[0005] FIG. 1 is a perspective view showing an example of a cutting insert according to an embodiment. FIG. 2 is a side cross-sectional view showing an example of a cutting insert according to an embodiment. FIG. 3 is a diagram schematically showing a scanning transmission electron microscope photograph of a cross section of a substrate according to an embodiment. FIG. 4 is a graph showing the nitrogen content ratios in the hard phase and binder phase for a substrate according to an embodiment and a conventional substrate. FIG. 5 is a flowchart showing an example of a procedure for producing a tungsten carbide powder according to an embodiment. FIG. 6 is a front view showing an example of a cutting tool according to an embodiment. FIG. 7 is an explanatory diagram for explaining an example of a method for manufacturing a machined product according to an embodiment. FIG. 8 is an explanatory diagram for explaining an example of a method for manufacturing a machined product according to an embodiment. FIG. 9 is an explanatory diagram for explaining an example of a method for manufacturing a machined product according to an embodiment. FIG. 10 is a diagram showing an outer portion of a substrate according to an embodiment.

[0006] Hereinafter, modes for carrying out the methods for manufacturing a hard member, a cutting insert, a cutting tool, and a machined product according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. The methods for manufacturing a hard member, a cutting insert, a cutting tool, and a machined product according to the present disclosure are not limited to these embodiments. The embodiments can be appropriately combined within the scope of not causing any contradiction in the processing content. In the following embodiments, the same parts are assigned the same reference numerals, and redundant explanations will be omitted.

[0007] In the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in a strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision or installation precision.

[0008] <Cutting Insert> Fig. 1 is a perspective view showing an example of a cutting insert 1 according to an embodiment. Fig. 2 is a side cross-sectional view showing an example of the cutting insert 1 according to an embodiment.

[0009] As shown in FIGS. 1 and 2 , a cutting insert 1 according to the embodiment includes a substrate 2 and a coating film 3 .

[0010] (Base 2) The base 2 has, for example, a hexahedral shape in which the upper and lower surfaces (surfaces intersecting with the Z axis shown in FIG. 1) are parallelograms.

[0011] One corner portion of the base body 2 functions as a cutting edge portion. The cutting edge portion includes a first surface (e.g., an upper surface) and a second surface (e.g., a side surface) connected to the first surface. In the embodiment, the first surface functions as a "rake surface" that scoops up chips generated by cutting, and the second surface functions as a "flank surface." A cutting edge is located on at least a portion of the ridge where the first surface and the second surface intersect, and the cutting insert 1 cuts the workpiece by bringing this cutting edge into contact with the workpiece.

[0012] A through hole 21 that passes through the base body 2 from top to bottom may be located in the center of the base body 2. In this case, a screw 75 for attaching the cutting insert 1 to a holder 70 (described later) is inserted into the through hole 21 (see FIG. 6).

[0013] The substrate 2 is made of a hard material. The hard material includes a hard phase and a binder phase. The hard phase may contain W (tungsten). For example, the hard phase may contain WC (tungsten carbide). The binder phase may be mainly composed of at least one iron group element selected from the group consisting of Fe (iron), Co (cobalt), and Ni (nickel). The main component may be an element that accounts for 50% by mass or more of the constituent components. The specific configuration of the substrate 2 will be described later.

[0014] (Coating film 3) The coating film 3 coats the base 2 for the purpose of improving the abrasion resistance, heat resistance, etc. of the base 2. While Fig. 2 shows an example in which the coating film 3 covers the entire surface of the base 2, the coating film 3 does not necessarily have to cover the entire surface of the base 2. The coating film 3 only needs to be located on at least a portion of the surface of the base 2. When the coating film 3 is located on the first surface (here, the top surface) of the base 2, the abrasion resistance and heat resistance of the first surface are high. When the coating film 3 is located on the second surface (here, the side surface) of the base 2, the abrasion resistance and heat resistance of the second surface are high.

[0015] The coating film 3 is formed on the surface of the substrate 2 by, for example, chemical vapor deposition (CVD) or physical vapor deposition (PVD). The coating film 3 may be, for example, a nitride film containing N (nitrogen). The coating film 3 may contain, for example, Ti (titanium) and N. The coating film 3 may be, for example, a TiN film containing TiN, a nitride of Ti. The coating film 3 may also contain, for example, Ti, N, and C (carbon). The coating film 3 may be, for example, a TiCN film containing TiCN, a carbonitride of Ti. The coating film 3 may also contain, for example, Al (aluminum), Ti, and N. The coating film 3 may be, for example, an AlTiN film containing AlTiN, a nitride of Al and Ti. The coating film 3 may also be a single layer. The cutting insert 1 may also have a layered coating film 3, i.e., two or more layers.

[0016] (Specific Configuration of Base 2) Next, a specific configuration of the base 2 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a diagram schematically showing a scanning transmission electron microscope photograph of a cross section of the base 2 according to the embodiment. Fig. 3 shows a cross section perpendicular to the normal to the surface of the base 2.

[0017] 3, the substrate 2 made of a hard material includes a hard phase 5 and a binder phase 6. Specifically, the substrate 2 is made up of hard phases 5 bonded together by the binder phase 6.

[0018] The hard phase 5 contains WC and N. The binder phase 6 contains N and at least one iron group element selected from the group consisting of Fe, Co, and Ni.

[0019] Here, among the regions in the depth direction from the surface of the base 2, a region up to 1 mm from the surface of the base 2 is defined as the "outer portion" of the base 2. Furthermore, a region located inside the outer portion in the depth direction from the surface of the base 2 is defined as the "inner portion" of the base 2. For example, the inner portion of the base 2 may be a region that is more than 1.5 mm deep from the surface of the base 2.

[0020] 4 is a graph showing the nitrogen content ratios in the hard phase and binder phase for the substrate 2 according to the embodiment and the substrate of a conventional product. In Fig. 4, the vertical axis shows the N (nitrogen) content ratios in the hard phase 5 and binder phase 6 in the outer and inner parts of the substrate 2, and the vertical axis shows the N content ratios in the hard phase and binder phase in the outer part of the conventional substrate.

[0021] In addition, in FIG. 4, the nitrogen content ratio in the hard phase 5 in the outer part of the substrate 2 is N ＯＨ [atm %], and the nitrogen content ratio in the binder phase 6 in the outer part is N ＯＢ In addition, for the substrate 2, the nitrogen content in the hard phase 5 in the inner part is N ＩＨ [atm %], and the nitrogen content ratio in the binder phase 6 at the inner part is N ＩＢ It is expressed as [atm %].

[0022] Here, a method for measuring and calculating the content ratio of N in this embodiment will be described.

[0023] First, EDX analysis is performed under the following analysis conditions: Elemental analysis (line analysis) Analysis method: Energy dispersive X-ray spectroscopy (EDX) Scanning transmission electron microscope: Hitachi High-Tech HD-2700 Acceleration voltage: 200 kV Beam diameter: Approximately 0.2 nmφ Elemental analysis device: Horiba EMAX Evolution X-ray detector: Si drift detector Energy resolution: Approximately 130 eV X-ray take-off angle: 24.8° Solid angle: Approximately 1.1 sr

[0024] The nitrogen content ratio in the hard layer 5 can be calculated, for example, by performing line analysis within a certain length range on the hard layer 5 as shown in Figure 10, and averaging the total amount of N content measured at intervals of 10 times the beam diameter within that certain length range by the number of measurement points. Here, the certain length is, for example, 100 nm. The nitrogen content ratio in the bonding phase 6 can also be calculated by a similar method. Figure 10 is a diagram showing the outer portion of a substrate according to an embodiment.

[0025] In this embodiment, the nitrogen content ratio of the outer portion is the nitrogen content ratio measured in a cross section 0.5 mm from the surface of the substrate 2, and the nitrogen content ratio of the inner portion is the nitrogen content ratio measured in a cross section 2 mm from the surface of the substrate 2.

[0026] As shown in FIG. 4, the substrate 2 according to the embodiment has a higher nitrogen content in the hard phase 5 in the outer portion than the substrate of the conventional product.

[0027] Here, the base body 2 according to the embodiment is N ＯＨ But, N ＩＨ is greater than.

[0028] With this configuration, N, which has lower diffusivity than C, is present in a relatively large amount in the hard phase 5 of the outer portion including the surface of the substrate 2, and this can reduce the diffusion of C from the substrate 2 to the coating film 3 when the coating film 3 is formed on the surface of the substrate 2 in a high-temperature environment, for example, by a CVD method. Therefore, according to the embodiment, the formation of the coating film 3 can be stabilized, and therefore the film properties such as adhesion, strength, and crystallinity of the coating film 3 can be improved. Furthermore, the excellent strength and crystallinity of the coating film 3 can improve the durability of the coating film 3, and as a result, the tool life of the cutting insert 1 can be extended.

[0029] Furthermore, since the amount of N contained in the hard phase 5 in the inner portion of the substrate 2 is relatively small, lattice defects due to N are reduced, increasing the strength of the substrate 2 and improving the fracture resistance of the substrate 2. Furthermore, since the affinity between the hard phase 5 and the binder phase 6 in the inner portion of the substrate 2 can be improved, the amount of binder phase 6 in the inner portion of the substrate 2 becomes greater than the amount of binder phase 6 in the outer portion. As a result, the amount of binder phase 6 in the outer portion of the substrate 2 becomes relatively small, and compressive residual stress is generated in the outer portion of the substrate 2, thereby improving the strength, fracture resistance, and chipping resistance of the substrate 2.

[0030] In addition, the base body 2 according to the embodiment is made of N ＩＢ But, N ＯＢWith this configuration, the solubility of the hard phase 5 in the binder phase 6 is reduced in the inner part of the substrate 2. Therefore, according to the embodiment, abnormal grain growth of the hard phase 5 in the inner part of the substrate 2 is inhibited, and the strength of the substrate 2 can be improved.

[0031] In addition, the base body 2 according to the embodiment is made of N ＯＨ and N ＩＨ Difference δ Ｈ But, N ＯＢ and N ＩＢ Difference δ Ｂ This structure improves the affinity between the hard phase 5 and the binder phase 6 in the inner portion of the substrate 2, so that the amount of binder phase 6 in the inner portion of the substrate 2 is greater than the amount of binder phase 6 in the outer portion. This reduces the amount of binder phase 6 in the outer portion of the substrate 2 relatively, and compressive residual stress is generated in the outer portion of the substrate 2, thereby improving the strength, fracture resistance, and chipping resistance of the substrate 2.

[0032] In addition, the base body 2 according to the embodiment is made of N ＩＢ But, N ＯＨ With this configuration, the solubility of the hard phase 5 in the binder phase 6 is reduced in the inner part of the substrate 2. Therefore, according to the embodiment, abnormal grain growth of the hard phase 5 in the inner part of the substrate 2 is inhibited, and the strength of the substrate 2 can be improved.

[0033] In addition, the base body 2 according to the embodiment is made of N ＯＢ and N ＩＢ Difference δ Ｂ But, N ＯＨ and N ＩＢ With this configuration, the solubility of the hard phase 5 in the binder phase 6 is further reduced in the inner part of the substrate 2. Therefore, according to the embodiment, abnormal grain growth of the hard phase 5 in the inner part of the substrate 2 is inhibited, and the strength of the substrate 2 can be improved.

[0034] In addition, the base body 2 according to the embodiment is made of N ＯＨ is 0.04 to 0.06 [atm %], and N ＯＢ is 0.065 to 0.085 [atm %], and N ＩＨis 0.02 to 0.04 [atm %], and N ＩＢ is preferably 0.07 to 0.1 atomic %. With this configuration, the affinity of the hard phase 5 and the binder phase 6 with the coating film 3 can be more uniformly improved in the outer portion including the surface of the substrate 2. Therefore, according to this embodiment, the film properties of the coating film 3 can be further improved.

[0035] (Method of Manufacturing Base 2) Next, a method of manufacturing the base 2 made of a hard member according to the embodiment will be described. Before describing the method of manufacturing the base 2, a process of producing tungsten carbide powder, which is the raw material of the base 2, will first be described with reference to Fig. 5. Fig. 5 is a flowchart showing an example of the procedure of the process of producing tungsten carbide powder according to the embodiment.

[0036] As shown in Figure 5, the process for producing tungsten carbide powder according to the embodiment includes the following steps (A) to (G): (A) preparing a raw material containing tungsten; (B) oxidizing tungsten in the raw material to obtain tungsten oxide; (C) using an alkaline solvent to obtain a solution in which tungsten oxide is eluted from the raw material; (D) adding a metal compound adsorbent (hereinafter sometimes referred to as an adsorbent) to the solution and reacting the adsorbent with the solution containing the eluted tungsten to obtain a compound containing the adsorbent and tungsten; (E) extracting the compound from the solution; (F) mixing the compound with carbon powder to produce a mixture; and (G) heating the mixture.

[0037] (Step A) First, a raw material containing tungsten is prepared. Examples of the raw material include ore and scrap containing tungsten. Examples of the ore containing tungsten include scheelite (CaWO ４ ), Wolframite (MnWO ４ ), ferrite (FeWO ４ ) and Wolframite ((Fe,Mn)WO ４Scrap containing tungsten is waste generated during the production process of products whose main components are metallic tungsten, tungsten carbide (WC), etc. Specific examples include scrap generated during the manufacturing process of cemented carbide tools, hard scrap such as used tools, and powdery soft scrap such as grinding sludge.

[0038] Cemented carbide, a type of cemented carbide, is mainly composed of composite carbides such as metallic tungsten and tungsten carbide. This composite carbide-based material contains iron, nickel, cobalt, etc. as a binder phase, and TiC, TaC, NbC, VC, Cr, etc. as additive components as needed. ３ C ２ Target materials containing cemented carbide include cutting tools (cutting inserts, drills, end mills, etc.), dies (forming rolls, forming dies, etc.), and civil engineering and mining tools (oil drilling tools, rock crushing tools, etc.).

[0039] (Step 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. For example, 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.

[0040] Examples of methods for oxidizing tungsten include oxidizing roasting. For example, tungsten oxide (WO ) can be obtained by oxidizing roasting a cutting tool containing tungsten carbide and cobalt. ３ ) and cobalt tungstate (CoWO ４ ) mixture is obtained.

[0041] As described above, the purpose of steps A and B is to obtain tungsten oxide from a raw material, and therefore these steps may be collectively expressed as a step of preparing a raw material containing tungsten oxide.

[0042] (Process C) Process C is an alkali extraction / alkali fusion process in which metal components of 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 tungsten 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 with, for example, an aqueous NaOH solution. The alkali dissolution method is a method in which scrap is subjected to alkali extraction with, for example, an aqueous NaOH solution, in which NaNO ３ , Na ２ SO ４ , Na ２ CO ３ This method involves simultaneously oxidizing and dissolving the metal using a molten salt of sodium salt such as NaOH.

[0043] For example, 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, as only the surface can be oxidized by oxidizing roasting.

[0044] (Step D) An adsorbent is added to the tungsten compound solution obtained in Step C. The adsorbent adsorbs tungsten compound ions in the tungsten compound solution. Here, the adsorbent may be, for example, a first adsorbent and / or a second adsorbent shown below.

[0045] [First Adsorbent] The first 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 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 referred to as the first free amino acid) relative to the total amount of free amino acids.

[0046] This allows metal compounds to be recovered through a simple process, and because it does not require the use of large amounts of chemicals, it reduces environmental pollution.

[0047] The free amino acids in the adsorbent may exist as a solid or may exist as free amino acids when dissolved in a solution. In either case, the solution contains free amino acids, and by using these adsorbents, metal compounds can be recovered through a simple treatment process.

[0048] An example of the first adsorbent is a substrate having free amino acids supported on its surface. The substrate may be, for example, an organic substance such as 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), or a resin, or an inorganic substance.

[0049] Examples of 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, Yarrowia ipolytica, Pichiapastoris, Hansenula polymorpha, and Kluyveromyces lactis, and koji mold.

[0050] Adsorbents made from biological substances come in various forms, such as powders, pellets formed from powders, gels, and aqueous solutions. Powders and pellets are easy to store and handle. When 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. Alternatively, the solid can be directly added to a solution containing the metal compound and stirred.

[0051] The first adsorbent preferably contains, as free amino acids, at least one amino acid selected from alanine, cystine, methionine, tyrosine, lysine, valine, glutamic acid, histidine, and proline (hereinafter sometimes referred to as the 1-1 amino acid), at least one amino acid selected from threonine, asparagine, glycine, isoleucine, ornithine, and arginine (hereinafter sometimes referred to as the 1-2 amino acid), and at least one amino acid selected from serine, citrulline, and cystathionine (hereinafter sometimes referred to as the 1-3 amino acid). Furthermore, the first adsorbent may contain, as free amino acids, at least one second amino acid selected from phosphoserine, aspartic acid, leucine, and phenylalanine, in a ratio of 40 mol% or less relative to the total amount of free amino acids.

[0052] 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.

[0053] When such an adsorbent is used and the 1-1 amino acid consists of two or more types, the 1-1 amino acid may be contained in a ratio of 5 mol% or more as free amino acids when the total amount of free amino acids is 100 mol%. In particular, lysine may be contained in a ratio of 10 mol% or more as free amino acids. In such cases, the recovery efficiency of metal compounds is improved. Furthermore, the total amount of the 1-1 amino acids is contained in a ratio of 10 mol% or more as free amino acids. This improves the recovery efficiency of metal compounds.

[0054] The adsorbent may contain a total amount of free amino acids consisting of the first amino acid of 0.5% by mass or more relative to the total amount of solid matter obtained by drying the adsorbent, i.e., the solid content of the adsorbent, which improves the recovery efficiency of metal compounds.

[0055] Furthermore, when the free amino acids contain aspartic acid and at least one amino acid selected from glutamic acid and valine as free amino acids, the content of at least one amino acid selected from glutamic acid and valine may be greater than that of aspartic acid. The free amino acids selected from 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. On the other hand, aspartic acid has a low ability to adsorb metal compounds (ions). Therefore, when the content of at least one amino acid selected from glutamic acid and valine in the free amino acids is greater than that of aspartic acid, the adsorption efficiency of metal compounds can be improved.

[0056] The type and content of free amino acids contained in the adsorbent can be confirmed by free amino acid analysis (also called biological amino 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. When 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. This suspension is used for free amino acid analysis.

[0057] When the adsorbent is in the form of a solution, the free amino acid content can be calculated by analyzing the solution for free amino acids and 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, for example, at 60°C for 24 hours.

[0058] In addition, the free amino acids contained in the biological material are supported on the surface of a substrate, which is a peptide or protein. Supporting free amino acids on a peptide or protein with a large molecular weight makes the adsorbent easier to handle, and when recovering the adsorbent to which the metal compound has been adsorbed from a solution containing the metal compound, it becomes possible to concentrate the adsorbent by a simple method such as filtration. The substrate may be a biological material or a resin or inorganic material, but if it is a biological material, the free amino acids can be easily increased. In the first adsorbent, free amino acids are supported on the body surface of a microorganism.

[0059] When the substrate of the adsorbent is a resin or an inorganic substance, a large number of free amino acids can be supported on the surface of the substrate if the substrate has a large specific surface area, such as a powder or a porous body. In the case of a porous body, amino acids can also be supported on the inner walls of the pores.

[0060] 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). Examples of inactive amino acids include amino acids located at intermediate positions among amino acids linked by peptide bonds, and amino acids located at internal positions that are not exposed on the surface of the adsorbent.

[0061] When the adsorbent is made of a biological substance, it is effective to perform a treatment to cleave the peptide bonds of the inactive amino acids present in the adsorbent and convert the inactive amino acids into free amino acids in order to increase the content of free amino acids in the adsorbent.

[0062] For example, when the organic matter is a microorganism, the peptide bonds present in the microorganism can be cleaved using existing treatment methods. Specifically, the proteins constituting 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.

[0063] Another effective method for converting inactive amino acids into free amino acids is to decompose proteins by subjecting the adsorbent to, for example, a heating treatment at 60°C or higher, a boiling treatment, or a heating and pressurizing treatment using an autoclave, etc. If 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, large-scale facilities for cultivation and storage and their maintenance are not required, and the facilities can be made smaller.

[0064] [Second Adsorbent] 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 exists 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 the free amino acids.

[0065] That is, 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.

[0066] An example of the second adsorbent is a salt of a first amino acid. Examples of salts include hydrochloride, nitrate, sulfate, acetate, and carbonate. An adsorbent made of an amino acid salt dissolves in a liquid to provide free amino acids. Then, as with 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 acids on the adsorbent is positive. At this time, since the metal compound exists as an anion, the anion of the metal compound is adsorbed to the positively charged free amino acids on the adsorbent.

[0067] In the second adsorbent, the content ratio of free amino acids in the adsorbent can be increased compared to a form in which free amino acids are supported on the surface of a substrate. Therefore, the adsorption efficiency of metal compounds is high, and a large amount of metal compounds can be adsorbed with a small amount of adsorbent. Furthermore, when recovering metal compounds after adsorption, the content of unnecessary materials that need to be disposed of is small, making handling easy and reducing production costs. Furthermore, since the adsorbent is not a living organism like bacteria or microorganisms, it is easy to store and manage the adsorbent.

[0068] The second adsorbent, which is an adsorbent made of a salt, may be in the form of a solution, but is easier to handle, store, and manage when it is solid, and in particular, when it is in powder form, it can be easily dissolved in a solution. Furthermore, the adsorbent may be in the form of pellets to facilitate handling of the adsorbent.

[0069] When the salt of the first amino acid is a salt of at least one of lysine and arginine as the main component, the adsorbent has good adsorption efficiency. For example, a salt containing lysine may be used as the adsorbent. Here, examples of the salt containing lysine include lysine hydrochloride, lysine sulfate, lysine nitrate, and lysine acetate.

[0070] Among these, lysine hydrochloride (e.g., L-lysine hydrochloride) is stable and inexpensive. Furthermore, when lysine hydrochloride is used as an adsorbent, it is less likely that unnecessary elements will be introduced during acid treatment in a subsequent step. Note that "containing at least one salt of lysine or arginine as the main component" means that the total mass ratio of the lysine salt or arginine salt in the adsorbent is 50 mass% or more relative to the total mass of the adsorbent.

[0071] 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 the adsorbent. The total amount of the lysine salt and the arginine salt present in the adsorbent is more preferably 95% by mass or more.

[0072] When a salt of glutamic acid is contained as the salt of the first amino acid, the cost of the adsorbent can be reduced. Among them, sodium glutamate is stable and inexpensive.

[0073] The content of glutamic acid salts in the adsorbent is preferably 90% by mass or more, which allows for inexpensive recovery of metal compounds. The total amount of glutamic acid salts in the adsorbent is preferably 95% by mass or more.

[0074] The free amino acid is not limited to one type, and for example, salts of other first amino acids such as lysine and arginine can be added together with the salt of glutamic acid.

[0075] Furthermore, for example, when the adsorbent is made of a microorganism, 1 g to 10 kg of the adsorbent is added per 1 m3 of a tungsten compound solution adjusted to a tungsten concentration of 0.1 to 10 mmol / L (0.1 to 10 mmol of tungsten per 1 liter of alkaline solution). When the adsorbent is made of a salt of a first amino acid, for example, 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 1 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 the adsorbent.

[0076] The total amount of the salt of the first amino acid added may be 10 to 300 g / L relative to 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.

[0077] The temperature can be adjusted depending on the activity of the free amino acid, and is usually room temperature. The tungsten compound solution to which the adsorbent has been added is adjusted using hydrochloric acid or the like so that the zeta potential of the free amino acid becomes positive. This allows the adsorbent to adsorb anionic tungsten compound ions.

[0078] The pH of the solution is less than 7 (acidic). When the free amino acids are lysine and arginine, the preferred pH is 4 or less, preferably 1 to 3, and desirably 1 to 2.3. When 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 either order.

[0079] When the adsorbent is a salt of the first amino acid, the recovery efficiency of the adsorbent is higher if the adsorption reaction is carried out within one hour. In other words, if the adsorption reaction exceeds one hour, a portion of the adsorbed metal compound may be desorbed from the free amino acid.

[0080] (Step E) Next, the adsorbent that has adsorbed the tungsten compound ions is extracted from the solution. Here, "extracting" includes a step of filtering the compound from the solution and a step of drying and powdering the compound recovered by filtration.

[0081] Specifically, 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 powdered tungsten compound containing the adsorbent. Here, the tungsten compound containing the adsorbent is, for example, lysine-WO ４ etc.

[0082] (Steps F and G) 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). This produces a mixture of tungsten compound and reducing agent. This mixture is then heated to 1100-2000°C under a predetermined atmosphere for a predetermined time, resulting in a carbonization treatment, producing tungsten powder primarily composed of tungsten carbide (Step G).

[0083] Here, "main component" means that tungsten carbide accounts for the largest proportion of the components contained in the powder, by mass %. Specifically, the powder contains 99 mass % or more of tungsten carbide, while unavoidable impurities of less than 1 mass % may be contained. Examples of unavoidable impurities include carbon, hydrogen, nitrogen, oxygen, chromium, vanadium, tantalum, niobium, and titanium.

[0084] More specifically, the material may contain 99.2 mass% or more of tungsten carbide and be substantially free of at least one carbide, nitride, or carbonitride selected from the group consisting of elements of groups IVa, Va, and VIa, excluding W. The predetermined atmosphere may be, for example, a reducing atmosphere containing carbon monoxide, nitrogen, hydrogen, methane, etc.

[0085] In step G, carbonization is performed in a mixed atmosphere containing nitrogen and hydrogen as the main components. In this way, when the mixed atmosphere contains nitrogen and hydrogen as the main components, production costs are reduced compared to when nitrogen and hydrogen are treated separately in separate atmospheres. Note that "main component" means that, among the components contained in the gas, nitrogen and hydrogen are present in greater amounts in mole percent than components other than nitrogen and hydrogen. More specifically, this refers to a case where the proportions of nitrogen and hydrogen are 40 mole % or more and 10 mole % or more, respectively.

[0086] Generally, the powder extracted in step E is incinerated to remove the adsorbent, and WO ３ is taken out. ３ Metallic tungsten is extracted by removing oxygen from the tungsten by reduction treatment, and tungsten carbide powder is obtained by carbonizing this metallic tungsten.

[0087] However, for example, if the adsorbent is removed and WO ３ The process of extracting WO requires incineration at a temperature of 300°C or higher. ３ The reduction treatment of tungsten carbide powder requires heat treatment in a reducing atmosphere (e.g., a hydrogen gas atmosphere) at a temperature of 800°C to 950°C, which places a heavy burden on the user.

[0088] On the other hand, in the production process of the embodiment, the tungsten compound extracted in the above-mentioned step E is directly carbonized to produce WC without undergoing the above-mentioned oxidation and reduction treatments. Therefore, the burden of producing tungsten carbide powder is reduced. Furthermore, when carbonizing the above-mentioned tungsten compound, carbon powder is mixed to produce a mixture, and then this mixture is heated.

[0089] When the adsorbent is an organic material as described above, the carbon component contained in the adsorbent can be used to carbonize tungsten to obtain WC. However, since the carbon component contained in the adsorbent alone is likely to be insufficient in the G step of carbonizing tungsten, in the G step, not only WC but also W can be obtained. ２ C is also easily produced.

[0090] In the step F of the production process of the embodiment, carbon powder is mixed with the tungsten compound, so the above-mentioned carbon shortage is resolved, and W ２ C is less likely to be produced, and it is possible to produce high-purity WC powder.

[0091] The amount of carbon powder added in the F step may be adjusted so that the carbon content in the mixture is 5 mass % or more. In this case, tungsten is easily carbonized stably in the G step, so that W ２ C is less likely to be produced, and WC is more likely to be produced.

[0092] Furthermore, 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. While the greater the carbon content in the mixture, the more stable the carbonization of tungsten becomes, if the carbon content in the mixture is too high, the step of removing the excess carbon that has not bonded to tungsten after step G may become complicated. However, if the carbon content in the mixture is 6% by mass or less, the load required to remove the excess carbon is small.

[0093] In addition, when the adsorbent is an organic substance as described above, the amount of carbon powder may be adjusted taking into account the amount of carbon components contained in the adsorbent. From another perspective, the carbon components in tungsten carbide may not only be derived from the carbon powder, but also from the carbon components in the adsorbent. That is, the carbon in the tungsten powder may contain the carbon in the adsorbent. When the adsorbent is an organic substance 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.

[0094] When the mixing atmosphere in the G step is mainly composed of nitrogen and hydrogen, the hydrogen content (mol %) may be less than or equal to that of nitrogen. When the hydrogen content is less than that of nitrogen, coarse particles are less likely to form. Note that the nitrogen and hydrogen content ratios being equal do not necessarily have to be exactly the same. A ratio of (nitrogen content ratio) / (hydrogen content ratio) between 0.9 and 1.1 is considered to be "equal."

[0095] In the tungsten carbide powder production process of the embodiment, the number of steps can be reduced compared to conventional tungsten carbide powder production processes, and the amount of chemicals used and waste liquid can be reduced, making it possible to recover tungsten compounds at low cost.

[0096] Furthermore, CO emitted in the conventional ion exchange method for producing tungsten carbide via ammonium paratungstate and W metal powder ２ CO emitted by the process of this application relative to the total amount (energy equivalent) ２ In this case, by using the process of the present invention to produce tungsten carbide, the total amount of CO emitted ２ It is possible to significantly reduce the amount of

[0097] Next, a method for manufacturing the substrate 2 using the tungsten carbide powder obtained in the production process of FIG. 5 as a raw material will be described.

[0098] The method for manufacturing the substrate 2 according to the embodiment includes the following steps (X) and (Y): (X) a step of mixing tungsten carbide powder with cobalt powder to form a compact; and (Y) a step of firing the compact.

[0099] More specifically, cobalt powder is first added to the tungsten carbide powder obtained by the production process shown in Figure 5. At this time, 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 shape using a known molding method such as press molding, slip casting, extrusion molding, or cold isostatic pressing to obtain a compact.

[0100] Thereafter, the compact is fired in a vacuum or in a non-oxidizing atmosphere to produce the base body 2 of the cutting insert 1. The surface of the produced base body 2 may be subjected to polishing or honing.

[0101] Thereafter, a coating film 3 may be formed by CVD or PVD on the surface of the substrate 2. Examples of the coating film 3 include titanium nitride (TiN), titanium carbonitride (TiCN), and aluminum titanium nitride (AlTiN).

[0102] <Cutting Tool> Next, a configuration of a cutting tool 100 including the above-described cutting insert 1 will be described with reference to Fig. 6. Fig. 6 is a front view showing an example of the cutting tool 100 according to an embodiment.

[0103] As shown in FIG. 6 , a cutting tool 100 according to the embodiment includes a cutting insert 1 and a holder 70 for fixing the cutting insert 1 .

[0104] The holder 70 is a rod-shaped member extending from its front end (upper end in FIG. 6 ) to its rear end (lower end in FIG. 6 ). The holder 70 is made of, for example, steel or cast iron. Of these materials, it is particularly preferable to use steel, which has high toughness.

[0105] The holder 70 has a pocket 73 at its tip end. The pocket 73 is a portion into which the cutting insert 1 is attached, and has a seating surface that intersects with the rotation direction of the workpiece and a constraint side surface that is inclined relative to the seating surface. The seating surface is provided with a screw hole into which a screw 75, which will be described later, is threaded.

[0106] The cutting insert 1 is positioned in the pocket 73 of the holder 70 and attached to the holder 70 by a screw 75. That is, the screw 75 is inserted into the through hole 21 of the cutting insert 1, and the tip of the screw 75 is inserted into a threaded hole formed in the seating surface of the pocket 73 to screw the threaded portions together. In this way, the cutting insert 1 is attached to the holder 70 so that the cutting edge portion protrudes outward from the holder 70.

[0107] In the embodiment, a cutting tool used for so-called turning is exemplified. Examples of turning include internal diameter machining, external diameter machining, and grooving. The cutting tool is not limited to that used for turning. For example, the cutting insert 1 may be used in a cutting tool used for milling. Examples of cutting tools used for milling include milling cutters such as flat milling cutters, face milling cutters, side milling cutters, and groove milling cutters, and end mills such as single-blade end mills, multi-blade end mills, tapered-blade end mills, and ball end mills.

[0108] <Method of Manufacturing Machined Product> Next, a method of manufacturing a machined product using the above-described cutting tool 100 will be described with reference to Figures 7 to 9. Figures 7 to 9 are explanatory views for explaining an example of a method of manufacturing a machined product according to an embodiment.

[0109] The machined product is produced by cutting the workpiece 200. The manufacturing method of the machined product in this embodiment includes the following steps: (1) a step of rotating the workpiece 200, (2) a step of bringing the cutting tool 100 into contact with the rotating workpiece 200, and (3) a step of separating the cutting tool 100 from the workpiece 200.

[0110] More specifically, first, as shown in Fig. 7 , workpiece 200 is rotated around axis O2, and cutting tool 100 is brought relatively close to workpiece 200. Typical examples of the material of workpiece 200 include carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals. Next, as shown in Fig. 8 , the cutting edge of cutting tool 100 is brought into contact with workpiece 200 to cut workpiece 200. Then, as shown in Fig. 9 , cutting tool 100 is moved relatively away from workpiece 200.

[0111] In Fig. 7, the axis O2 is fixed and the workpiece 200 is rotated around the axis O2, while the cutting tool 100 is moved in the Y1 direction to approach the workpiece 200. In Fig. 8, the cutting edge of the cutting insert 1 is brought into contact with the rotating workpiece 200 to cut the workpiece 200. In Fig. 9, the cutting tool 100 is moved away from the rotating workpiece 200 by moving in the Y2 direction.

[0112] In the cutting process in the manufacturing method of this embodiment, the cutting tool 100 is moved in each step to bring the cutting tool 100 into contact with the workpiece 200 or to move the cutting tool 100 away from the workpiece 200. However, the cutting process is not limited to this form.

[0113] For example, in step (1), the workpiece 200 may be brought closer to the cutting tool 100. Similarly, in step (3), the workpiece 200 may be moved away from the cutting tool 100. When continuing the cutting process, the workpiece 200 may be kept rotating, and the step of bringing the cutting edge of the cutting insert 1 into contact with different locations on the workpiece 200 may be repeated.

[0114] Furthermore, in the method for manufacturing a machined product according to this embodiment, an example has been shown in which the workpiece 200 is rotated, but the cutting tool 100 may be rotated instead of the workpiece 200. That is, the method for manufacturing a machined product may include a step of rotating the cutting tool 100, a step of bringing the cutting tool 100 into contact with the workpiece 200, and a step of separating the cutting tool 100 from the workpiece 200.

[0115] As described above, the hard member according to the embodiment has a substrate (for example, substrate 2) including a hard phase (for example, hard phase 5) and a binder phase (for example, binder phase 6). The hard phase contains tungsten carbide and nitrogen. The binder phase contains nitrogen and at least one iron group element selected from the group consisting of iron, cobalt, and nickel. The substrate has an outer portion extending from the surface to a depth of 1 mm, and an inner portion located inside the outer portion in the depth direction from the surface. The nitrogen content ratio of the hard phase in the outer portion is defined as N ＯＨ [atm%], the nitrogen content in the hard phase in the inner part is N ＩＨ When expressed as [atm %], N ＯＨ is N ＩＨ is greater than.

[0116] As a result, the hard member according to the embodiment can improve the adhesion of the coating film to the substrate.

[0117] 1 is merely an example and does not limit the shape of the cutting insert 1 according to the present disclosure. The cutting insert according to the present disclosure may have, for example, a rod-shaped body having a rotation axis and extending from a front end to a rear end, a cutting edge located at a first end of the body, and a groove extending spirally from the cutting edge toward a second end of the body.

[0118] Further, although an example in which the hard member is used as a tool has been described here, the use of the hard member according to the present disclosure is not limited to tools.

[0119] Further advantages and alternative embodiments may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0120] REFERENCE SIGNS LIST 1 Cutting insert 2 Substrate 3 Coating film 5 Hard phase 6 Binder phase 21 Through hole 70 Holder 73 Pocket 75 Screw 100 Cutting tool

Claims

1. A substrate including a hard phase and a binder phase, wherein the hard phase contains tungsten carbide and nitrogen, and the binder phase contains at least one iron-group element selected from the group consisting of iron, cobalt, and nickel, and nitrogen, and the substrate has an outer portion that is a region extending from the surface to 1 mm, and an inner portion located inside the outer portion in a depth direction from the surface, and the nitrogen content ratio of the hard phase in the outer portion is N ＯＨ [atm %], the nitrogen content ratio in the hard phase in the inner part is N ＩＨ When expressed as [atm %], N ＯＨ is N ＩＨ Larger than hard material.

2. The nitrogen content in the binder phase in the outer portion is N ＯＢ [atm %], the nitrogen content in the binder phase in the inner portion is N ＩＢ When expressed as [atm %], N ＩＢ is N ＯＢ The hard member according to claim 1 , wherein the hard member has a diameter greater than 1 / 2 mm.

3. N ＯＨ and N ＩＨ The difference is N ＯＢ and N ＩＢ The hard member according to claim 2 , wherein the difference between the 4. N ＩＢ is N ＯＨ The hard member according to claim 2 or 3, wherein the hard member has a thickness greater than 1 / 2 mm.

5. N ＯＢ and N ＩＢ The difference is N ＯＨ and N ＩＢ The hard member according to any one of claims 2 to 4, wherein the difference between the 6. N ＯＨ is 0.04 to 0.06 [atm %], and N ＯＢ is 0.065 to 0.085 [atm%], and N ＩＨ is 0.02 to 0.04 [atm %], and N ＩB The hard member according to any one of claims 2 to 5, wherein the content of Cr is 0.07 to 0.1 [atm %].

7. A cutting insert comprising the hard member according to any one of claims 1 to 6, wherein the base body has a cutting edge.

8. A cutting tool comprising: a holder extending from a front end to a rear end and having a pocket located on the front end side; and the cutting insert according to claim 7 located in the pocket.

9. A method for manufacturing a machined product, comprising the steps of: rotating the cutting tool according to claim 8; bringing the cutting tool into contact with a workpiece; and separating the cutting tool from the workpiece.

10. A method for manufacturing a machined product, comprising the steps of: rotating a workpiece; bringing the cutting tool according to claim 8 into contact with the rotating workpiece; and separating the cutting tool from the workpiece.

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