Lightweight hard alloys and lightweight hard alloy components

Abstract

A lightweight hard alloy comprising a hard phase with a core-rim structure, the lightweight hard alloy being obtained by sintering a mixed powder containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component, containing 5 to 33 mass% of W and / or Mo in terms of carbide, and containing 5 to 40 mass% of at least one binder phase component selected from the group consisting of Ni, Co and Fe, wherein in a cross-sectional structure of the lightweight hard alloy observed with a scanning electron microscope, the core phases having a core-rim structure have an average particle size of D90 or more on a number basis in the particle size distribution of the area circle equivalent diameter of the core phases, and the average Dmax / Dmin ratio of the shortest length Dmin to the longest length Dmax of the straight line connecting the center of gravity of the core phases of D90 or more to the outline is 2.0 or less.

Description

[Technical Field]

[0001] The present invention relates to a lightweight hard alloy and a lightweight hard alloy member using the same. [Background technology]

[0002] In recent years, ceramics and cemented carbide are often used as wear-resistant components for crushing, mixing, and kneading resins and magnetic materials. However, ceramics have low toughness and are prone to chipping due to interference between wear-resistant components. Screws and other components are large, and when made from cemented carbide, their specific gravity is high, making them heavy. This can cause deflection in cantilever screws, and makes it difficult to increase rotational speed.

[0003] On the other hand, when sintering large cermet components, there is a problem that they are prone to cracking during sintering. Therefore, in recent years, there has been a demand for large cermet components that are both lightweight and tough, and that are less susceptible to sintering cracking.

[0004] Patent Document 1 discloses a high-toughness cermet in which needle-like precipitates containing W as one of the constituent elements are dispersed in a matrix containing 5 to 25 weight percent TiC, 25 to 50 weight percent WC, and 5 to 40 weight percent Ni+Co. However, because the cermet contains a large amount of WC, 25 to 50 weight percent, it results in a heavy tool component.

[0005] Patent Document 2 discloses a high-toughness cermet for cutting tools, which has a binder phase made of one or more Fe group metals, a first hard dispersed phase made of titanium nitride, and a second hard dispersed phase made of a solid solution carbonitride of one or more transition metals from groups 4a, 5a, and 6a of the periodic table, with an atomic ratio of carbon to nitrogen of nitrogen / (carbon + nitrogen) = 0.01 to 0.3. However, the presence of the titanium nitride phase results in poor grindability, and the high cost of the solid solution carbide poses production problems.

[0006] Cermets, primarily composed of titanium compounds such as TiC and Ti(C,N), are materials that combine the toughness of cemented carbide with the light weight of ceramics. TiC and Ti(C,N) have relatively good wettability with Ni and Co, allowing for the production of dense sintered bodies, and because they contain a metallic bonding phase, they have higher fracture toughness than ceramics. TiC and Ti(C,N) also have a lower specific gravity than WC, making cermets lighter than cemented carbide. However, compared to cemented carbide, existing cermets do not meet the toughness required for wear-resistant components, and have had problems with chipping during use.

[0007] Non-Patent Document 1 describes commercially available TiC (average particle size by FSSS method: 1.4 μm), Ti(C 0.7 N 0.3 )(1.4μm), Ti(C 0.5 N 0.5 )(1.4μm), Mo2C(3.6μm), Ni(2.5μm) were used to 0.7 N 0.3 )-, Ti(C 0.5 N 0.5 The paper discloses TiC-based and Ti(C,N)-based cermets with a composition of MoC-19% by mass and Ni-24% by mass. However, Ti(C,N)-based cermets tend to produce fine powder during powder mixing, which can lead to cracks when thick-walled products are sintered. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 3-281752 [Patent Document 2] Patent No. 2674243 [Non-patent literature]

[0009] [Non-Patent Document 1] Takayuki Shoji and four others, Elucidation of the Cause of Sintering Cracks in Ti(C,N)-Based Cermets and Development of Prevention Methods, Powder and Powder Metallurgy, Vol. 57, No. 8, August 2010, pp. 579-586 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, an object of the present invention is to provide a lightweight hard alloy that is both lightweight and highly tough and has excellent grindability, and a lightweight hard alloy member that is suitable as a wear-resistant member that rotates, such as a screw or a crushing blade, using the same. [Means for solving the problem]

[0011] To solve the above problem, we investigated the causes of the low toughness of TiC-based and Ti(C,N)-based cermets, and attempted to improve toughness at the same hardness by identifying the required factors and designing the alloy.

[0012] First, we reviewed the titanium compound powder, which is the main component. Conventionally, Ti(C,N) powder, for example, produced by the thermal carbonitriding method, has been widely used. However, fine powder is easily generated during the process of crushing and classifying the powder to the specified particle size after carbonitriding, resulting in a large amount of fine powder at the raw powder stage used to produce the alloy. Furthermore, further crushing during mixing increases the amount of fine powder. The generation of this fine powder results in the formation of many fine hard phases in the sintered compact structure, while the surrounding structure (rim phase) of the hard phase, which has a relatively large particle size, tends to grow even more. As a result, we found that the number of hard phase / hard phase adhesive interfaces increases, cracks become more likely to propagate, and hardness also decreases.

[0013] As a result of various studies to solve these problems, the inventors conducted cross-sectional structural observation of the obtained lightweight hard alloy using a scanning electron microscope and found that a lightweight hard alloy with excellent toughness and high strength can be obtained when the average particle size of the core phase of D90 or more on a number basis in the particle size distribution of the area circle equivalent diameter of the core phase among the hard phases having a core-rim structure is 0.8 to 3.3 μm, and the average ratio Dmax / Dmin of the shortest length Dmin to the longest length Dmax of the straight line connecting the center of gravity of the core phase of D90 or more to its outline is 2.0 or less.

[0014] Furthermore, when titanium compounds consisting of titanium carbide and / or titanium carbonitride containing a small amount of oxygen are used as raw powders for lightweight hard alloys, they are less likely to be pulverized by mixed pulverization, and fine powder is less likely to be produced.In addition, it has been found that a large amount of core phase with excellent wear resistance remains in the resulting sintered alloy, and peripheral structure is less likely to form, and when the ratio of the oxygen content in the core phase of the hard phase to the oxygen content in the rim phase (core phase oxygen content / rim phase oxygen content) is 0.9 or more, an alloy with high toughness can be obtained.

[0015] That is, the lightweight hard alloy according to the first embodiment of the present invention is a lightweight hard alloy containing a hard phase having a core-rim structure, which is obtained by sintering a mixed powder containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component, containing 5 to 33 mass% of W and / or Mo in terms of carbide, and containing 5 to 40 mass% of at least one selected from the group consisting of Ni, Co and Fe as a binder phase component, In the cross-sectional structure of the lightweight hard alloy observed with a scanning electron microscope, the core phases of the hard phase having a core-rim structure have an average particle size of D90 or more on a number basis in the particle size distribution of the area circle equivalent diameter of the core phases, and the average ratio Dmax / Dmin of the shortest length Dmin to the longest length Dmax of the straight line connecting the center of gravity of the core phases of D90 or more to the outline is 2.0 or less.

[0016] A lightweight hard alloy according to a second embodiment of the present invention is a lightweight hard alloy comprising a hard phase having a core-rim structure, which is obtained by sintering a mixed powder containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component, containing 5 to 33 mass% of W and / or Mo in terms of carbide, and containing 5 to 40 mass% of at least one selected from the group consisting of Ni, Co and Fe as a binder phase component, the titanium compound contains 0.7% by mass or more of oxygen; The hard phase is characterized in that the ratio of the oxygen content in the core phase to the oxygen content in the rim phase (core phase oxygen content / rim phase oxygen content) is 0.9 or more.

[0017] The titanium compound preferably contains 0.7 to 2.5 mass % of oxygen.

[0018] When the amount of particles having a particle size of 0.8 μm or less contained in the mixed powder is A (volume %), the particle amount A is expressed by the following formula (1) relative to the content X (volume %) of at least one selected from the group consisting of Ni, Co, and Fe contained in the mixed powder: A<-1.3X+53.4 (1) or is preferably 20% by volume or less.

[0019] The mixed powder preferably further contains 8 mass % or less of Cr in terms of Cr3C2.

[0020] The mixed powder preferably contains 15% by mass or less of elements in Groups 4 to 6 of the periodic table other than Ti, W, Mo and Cr, calculated as carbides.

[0021] A lightweight hard alloy according to a third embodiment of the present invention is a lightweight hard alloy containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component and including a hard phase having a core-rim structure, In the cross-sectional structure of the lightweight hard alloy observed with a scanning electron microscope, the core phases of the hard phase having a core-rim structure have an average particle size of D90 or more on a number basis in the particle size distribution of the area circle equivalent diameter of the core phases, and the average ratio Dmax / Dmin of the shortest length Dmin to the longest length Dmax of the straight line connecting the center of gravity of the core phases of D90 or more to the outline is 2.0 or less.

[0022] In this embodiment, it is preferable that the material be obtained by sintering a mixed powder containing, as a main component, a titanium compound made of titanium carbide and / or titanium carbonitride.

[0023] A lightweight hard alloy according to a fourth embodiment of the present invention is a lightweight hard alloy comprising a hard phase having a core-rim structure, the lightweight hard alloy being obtained by sintering a mixed powder containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component, the titanium compound contains 0.7% by mass or more of oxygen; The hard phase is characterized in that the ratio of the oxygen content in the core phase to the oxygen content in the rim phase (core phase oxygen content / rim phase oxygen content) is 0.9 or more.

[0024] The titanium compound preferably contains 0.7 to 2.5 mass % of oxygen.

[0025] The nitrogen content of the titanium compound is preferably 0.7% by mass or more and less than 8% by mass.

[0026] A lightweight hard alloy member according to one embodiment of the present invention is characterized by using the lightweight hard alloy described above. [Effects of the Invention]

[0027] According to the present invention, a lightweight hard alloy can be obtained that is both lightweight and highly tough, and that is resistant to cracking during sintering even in thick-walled products, and has excellent grindability. This makes it suitable for use in large, wear-resistant components that rotate at high speeds, such as screws and grinding blades, and can dramatically improve production efficiency in grinding, mixing, and kneading. For example, it is suitable for applications such as tools and grinding blades for grinding, mixing, and kneading resins and magnetic materials. Because of these similar characteristics, it is also suitable for use in molds and peripheral components for lens molding. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 2 is a schematic diagram showing a method for measuring Dmax / Dmin, which is the ratio of the shortest length Dmin to the longest length Dmax of a straight line connecting the center of gravity of a core phase having a nearly circular cross section to its outline. [Figure 2] FIG. 2 is a schematic diagram showing a method for measuring Dmax / Dmin, which is the ratio of the shortest length Dmin to the longest length Dmax of a straight line connecting the center of gravity of a core phase having a longitudinal cross section to the contour. [Figure 3] 1 is an SEM photograph showing a cross section of the lightweight hard alloy of Invention Product 8. [Figure 4] 1 is an SEM photograph showing a cross section of the lightweight hard alloy of Invention Product 13. DETAILED DESCRIPTION OF THE INVENTION

[0029] [1] Lightweight hard alloy (1) First embodiment A lightweight hard alloy according to a first embodiment of the present invention is a lightweight hard alloy containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component and containing a hard phase having a core-rim structure, In the cross-sectional structure of the lightweight hard alloy observed with a scanning electron microscope, the core phase of the hard phase having a core-rim structure has an average particle size of D90 or more on a number basis in the particle size distribution of the area circle equivalent diameter of the core phase, and is characterized in that the average Dmax / Dmin ratio of the shortest length Dmin to the longest length Dmax of the straight line connecting the center of gravity of the core phase of D90 or more to the outline is 2.0 or less.

[0030] The titanium compound constituting the main component is a carbon-containing titanium compound, specifically at least one compound selected from the group consisting of titanium carbide and titanium carbonitride. Furthermore, titanium nitride may be contained in an amount of up to 5 mass% of the total amount of titanium compounds. Carbon-containing titanium compounds have high hardness and excellent wear resistance, so when they are included as the main component, a lightweight hard alloy with excellent wear resistance can be obtained.

[0031] Here, the term "main component" refers to the carbon-containing titanium compound being the largest in mass ratio among all the compounds other than the binder phase components. The mass ratio of the titanium compound to the total amount of compounds other than the binder phase components is preferably greater than 50%, and the mass ratio of the carbon-containing titanium compound is preferably 1.5 to 5 times, and more preferably 2 to 4 times, the total amount of the other compounds.

[0032] In the particle size distribution of the area circle diameter of the core phase among the hard phases having a core-rim structure, the average particle size of the core phase is D90 or more on a number basis, which is 0.8 to 3.3 μm. If the average particle size of the core phase is less than 0.8 μm, the wear resistance will be slightly inferior depending on the usage conditions. If the average particle size of the core phase is more than 3.3 μm, the strength will be insufficient. The average particle size of the core phase is preferably 0.9 to 3.0 μm, more preferably 1.0 to 2.8 μm, and even more preferably 1.2 to 2.6 μm. The average particle size of the core phase is limited to D90 or more because the average particle size of the core phase within this range has a significant effect on the wear resistance and strength of the lightweight hard alloy. It also clearly shows the effect of the pulverization state of the titanium compound in the mixed powder, which will be described later.

[0033] The average particle size of the core phases with a diameter of D90 or more is determined by photographing 10 fields of view of an arbitrary cross-sectional SEM structure (5,000x magnification) of the lightweight hard alloy, processing the images, calculating the particle size distribution based on the number of core phases with a diameter of 0.2 μm or more among the diameters of the circles converted from the area of ​​each core phase, and averaging the particle sizes of the core phases with a diameter of D90 or more. These operations can be performed by analyzing using general image analysis software such as Image-Pro Plus. Alternatively, an arbitrary cross-section of the lightweight hard alloy may be etched, and then analysis may be performed based on the SEM structure of the etched cross-section. Since the mixed powder of this embodiment is a mixed powder produced by weakening the crushing strength using a titanium compound powder with a small amount of fine powder in the powder, a lightweight hard alloy obtained by sintering such a mixed powder has such structural characteristics.

[0034] The ratio Dmax / Dmin of the shortest length Dmin to the longest length Dmax of a straight line connecting the center of gravity of a core phase of D90 or more to the outline is 2.0 or less. Here, the method for measuring the shortest length Dmin and the longest length Dmax will be explained using Fig. 1 and Fig. 2. Fig. 1 and Fig. 2 are schematic diagrams showing the cross section of a hard phase having a core-rim structure of a lightweight hard alloy observed with a scanning electron microscope. The center of gravity of the core phase of the hard phase having a core-rim structure is determined, and the shortest length of the straight line connecting the center of gravity to the outline of the core phase is defined as Dmin and the longest length is defined as Dmax. As shown in Fig. 1, when the core phase is close to a sphere (the cross section of the core phase is close to a circle), the ratio Dmax / Dmin of the shortest length Dmin to the longest length Dmax is small. On the other hand, when the core phase is elongated (the cross section of the core phase is elongated) as shown in Fig. 2, the ratio Dmax / Dmin of the shortest length Dmin to the longest length Dmax is large.

[0035] It is desirable that 60% or more of the core phases having a core-rim structure with a particle size distribution of D90 or more satisfy the ratio Dmax / Dmin ≦ 2.0. This allows for the production of lightweight hard alloys with excellent toughness and high strength. It is more preferable that 65% or more of the core phases satisfy this ratio, more preferably 70% or more of the core phases, even more preferably 75% or more of the core phases, particularly preferably 80% or more of the core phases, and most preferably 90% of the core phases satisfy this ratio.

[0036] The average value of the ratio Dmax / Dmin of the core phase in the hard phase having a core-rim structure is preferably 2.0 or less. The average value of the ratio Dmax / Dmin is determined, as with the average grain size of the core phase, by photographing 10 fields of view of an arbitrary cross-sectional SEM structure (5,000x magnification) of the lightweight hard alloy, processing the images, determining the particle size distribution based on the number of core phases with a diameter of 0.2 μm or more among the diameters obtained by converting the area of ​​each core phase into a circle, and averaging the values ​​of the ratio Dmax / Dmin of each core phase of D90 or more. It is particularly preferable that 60% or more of the core phase in the hard phase having a core-rim structure satisfy the ratio Dmax / Dmin≦2.0, and that the average value is 2.0 or less. This makes it possible to obtain a lightweight hard alloy that is particularly excellent in toughness and strength.

[0037] When the average grain size of the core phase of D90 or more is 0.8 to 3.3 μm and the ratio Dmax / Dmin of the shortest length Dmin of the straight line connecting the center of gravity to the outline to the longest length Dmax is 2.0 or less, an alloy with excellent toughness and high strength can be obtained. The ratio Dmax / Dmin is preferably 1.9 or less, and more preferably 1.8 or less.

[0038] The number of hard phases having a core-rim structure is preferably 30% or more of the total number of hard phases, more preferably 45% or more, even more preferably 60% or more, and particularly preferably 70% or more. The number of hard phases is determined by photographing 10 fields of view of an arbitrary cross-sectional SEM structure (5,000x magnification) of the lightweight hard alloy, processing the images, and counting the number of hard phases with a diameter of 0.2 μm or more among the diameters of circles converted from the area of ​​each hard phase. Among these hard phases with a diameter of 0.2 μm or more, those in which a core-rim structure can be observed are considered to have a core-rim structure.

[0039] The average grain size of the hard phase is preferably 0.8 to 3.5 μm. The average grain size of the hard phase is determined by Fulman's formula based on the SEM structure of any cross section of the lightweight hard alloy. If the average grain size of the hard phase is less than 0.8 μm, the wear resistance may be slightly inferior depending on the usage conditions. If the average grain size of the hard phase is more than 3.5 μm, the strength may be insufficient. The average grain size of the hard phase is more preferably 0.9 to 3.0 μm, even more preferably 1.1 to 2.8 μm, and particularly preferably 1.3 to 2.6 μm.

[0040] One example of the lightweight hard alloy according to the first embodiment of the present invention is obtained by sintering a mixed powder containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component, containing 5 to 33 mass% of WC and / or Mo2C, and containing 5 to 40 mass% of at least one selected from the group consisting of Ni, Co and Fe as a binder phase component, and in a cross-sectional structure of the lightweight hard alloy observed with a scanning electron microscope, the average particle size of the core phases of D90 or more on a number basis in the particle size distribution of the area circle diameter of the core phases of the hard phases having a core-rim structure is 0.8 to 3.3 μm, and the average ratio Dmax / Dmin of the shortest length Dmin to the longest length Dmax of the straight line connecting the center of gravity of the core phases of D90 or more to the outline is 2.0 or less.

[0041] The mixed powder contains 5 to 33 mass% of WC and / or Mo2C. If the WC and / or Mo2C content is less than 5 mass%, the surrounding structure may not be sufficiently formed in the hard phase of the lightweight hard alloy, making it difficult to control the particle size and resulting in insufficient strength. On the other hand, if the WC and / or Mo2C content exceeds 33 mass%, the lightweight hard alloy may have too high hardness and reduced toughness. The WC and Mo2C content is preferably 7 to 30 mass%, more preferably 10 to 26 mass%. The hard phase constituent particles are titanium carbide and / or titanium carbonitride, WC, and Mo2C. The mixed powder may contain only Mo2C. The mass ratio of WC to Mo2C (WC / Mo2C ratio) is preferably 0.11 to 1, more preferably 0.25 to 0.67, and even more preferably 0.25 to 0.43. Furthermore, since WC improves high-temperature properties such as high-temperature deformation, the WC / Mo2C ratio may be set to 1 to 9, or only WC may be used, if necessary for the intended use.

[0042] The mixed powder preferably further contains 8% by mass or less of Cr in terms of Cr3C2. This can improve the corrosion resistance of the lightweight hard alloy. If the Cr content exceeds 8% by mass in terms of Cr3C2, there is a risk of a decrease in toughness. Cr may be added in the form of carbide or nitride, or as an alloy of Ni, Cr, etc. The Cr content is more preferably 0.1 to 5% by mass, and even more preferably 0.5 to 4% by mass in terms of Cr3C2.

[0043] At least a portion of WC, Mo2C and Cr3C2 may be added as a solid solution with a compound of another element such as a titanium compound.

[0044] The mixed powder may further contain up to 15 mass% of Group 4 to 6 elements of the periodic table other than Ti, W, Mo, and Cr, calculated as carbides. Furthermore, Group 4 to 6 elements other than Ti, W, Mo, and Cr may be added as a solid solution with other element compounds, such as titanium compounds. Even when other elements are contained in the titanium compound, the core can be identified by the difference in brightness, as in the case of alloys using titanium compounds that do not contain other elements, or the core shape can be identified by the difference in color tone along the core phase / rim phase boundary.

[0045] When Zr is contained in the mixed powder in an amount of 0.1 to 3 mass% in terms of carbide, wear resistance is improved. If it is less than 0.1 mass%, no effect is exhibited. If it exceeds 3 mass%, sinterability may be reduced. Zr may be added to the mixed powder as metal, as carbide, nitride, oxide, or a solid solution compound thereof, or as a solid solution in another compound such as a titanium compound.

[0046] The total amount of the elements of Groups 4 to 6 of the periodic table other than Ti that are dissolved in the titanium compound is preferably 30 mass % or less in terms of carbide relative to the titanium compound.

[0047] In the lightweight hard alloy of this example, some of the W, Mo, and Cr in WC, Mo2C, and Cr3C2, and some of the above Group 4 to 6 elements, form a solid solution with a titanium compound containing carbon to form a peripheral structure of the hard phase. That is, the hard phase forms a core-rim structure with a core mainly composed of a titanium compound and a peripheral structure surrounding it. Some of them also form a solid solution in the binder phase.

[0048] The nitrogen content of the titanium compound is preferably less than 8% by mass. If the nitrogen content of titanium is 8% by mass or more, the core phase of titanium carbonitride remains, improving wear resistance, and the grain growth of the hard phase is suppressed, improving strength and alloy hardness. However, grindability deteriorates and the processing time for the wear-resistant component increases, resulting in reduced productivity and increased costs. Furthermore, the nitrogen content of the titanium compound is preferably 0.7% by mass or more. If the nitrogen content is less than 0.7% by mass, fine powder is more likely to be generated during mixed grinding than when the nitrogen content is not 0.7%.

[0049] The mixed powder contains 5 to 40 mass% of at least one selected from the group consisting of Ni, Co, and Fe as a binder phase component. If this content is less than 5 mass%, the required strength of the lightweight hard alloy cannot be maintained, and if it exceeds 40 mass%, the required wear resistance cannot be maintained. The content of the binder phase component is preferably 10 to 38 mass%, more preferably 16 to 36 mass%.

[0050] The higher the Co content in the entire mixed powder, the higher the alloy hardness and the better the wear resistance tends to be. However, the wettability with the hard phase tends to decrease, which reduces sinterability, and the interfacial strength tends to decrease, making cracks more likely to develop. Therefore, if toughness is important, the Co content should be 9.5 mass% or less.

[0051] It is preferable that the BET value x theoretical specific gravity of the mixed powder is 38 or less. The BET value is the total surface area per unit weight (1 g) of the mixed powder measured by the BET method, expressed in square meters. 2 / g). The theoretical specific gravity of the mixed powder is calculated from the specific gravity and composition ratio of each raw material powder used. The BET value of the mixed powder x the theoretical specific gravity is a dimensionless number.

[0052] Here, we will explain the significance of the BET value x theoretical specific gravity parameter. The lightweight hard alloy mixed powder of this example contains a carbon-containing titanium compound as the main component of the hard phase particles, and also contains WC and / or Mo2C. The specific gravity of each component is significantly different: WC has a specific gravity of 15.6, Mo2C has a specific gravity of 9.18, while TiC has a specific gravity of 4.92. Therefore, the specific gravity of the mixed powder varies significantly depending on the content ratio of these components. As a result, the amount of powder per unit weight (1 g) also changes, and the BET value cannot fully represent the characteristics of the mixed powder. Therefore, by multiplying the BET value by the theoretical specific gravity of the mixed powder, the specific surface area of ​​the powder per volume when the mixed powder is considered as a dense body is used as an index.

[0053] If the BET value x theoretical specific gravity of the mixed powder exceeds 38, the specific surface area per volume of the mixed powder becomes too large, resulting in a large amount of fine powder in the mixed powder and a too small average particle size. This leads to the formation of fine hard phases in the lightweight hard alloy, and the dissolution and reprecipitation of the fine powder also leads to the formation of a peripheral structure (rim phase) around the hard phase. The peripheral structure has low strength, and the formation of the peripheral structure increases the adhesion of the hard phase, resulting in reduced fracture toughness, insufficient strength, and prone to chipping. The BET value x theoretical specific gravity of the mixed powder is more preferably 37 or less, even more preferably 36 or less, and particularly preferably 35 or less. This suppresses the formation of a weak peripheral structure and the increase in adhesion of the hard phase. As a result, the alloy retains a large amount of the titanium compound core phase, which is high in strength and wear resistance. This results in a lightweight hard alloy with excellent wear resistance and chipping resistance when used as a tool. If a mixed powder is obtained in which the average particle size of the hard phase constituting the sintered body of the lightweight hard alloy does not exceed 3.5 μm, there is no lower limit to the product of the BET value and the theoretical specific gravity.

[0054] When the amount of particles having a particle size of 0.8 μm or less contained in the mixed powder is A (volume %) (the entire mixed powder is taken as 100 volume %), the particle amount A is expressed by the following formula (1) relative to the content X (volume %) of at least one selected from the group consisting of Ni, Co, and Fe contained in the mixed powder: A<-1.3X+53.4 (1) It is preferable that the particle amount A satisfies the following condition or is 20% by volume or less. The particle size distribution of the mixed powder may be measured using a laser diffraction particle size distribution analyzer. From the obtained particle size distribution of the mixed powder, the amount A of particles with a particle size of 0.8 μm or less is calculated as a volume ratio. If the particle amount A satisfies A<-1.3X+53.4 or is 20% by volume or less, fine hard phases are less likely to form in the lightweight hard alloy structure, and the small amount of fine powder makes it difficult for peripheral structures to form due to dissolution and reprecipitation during sintering. It is more preferable that the particle amount A satisfies A<-1.3X+53.4, and even more preferable that the particle amount A is A≦-X+41.3. The particle amount A may satisfy A<-1.3X+53.4 or may be 20% by volume or less of the total mixed powder. The particle amount A may also be 20% by volume or less of the total mixed powder.

[0055] (2) Second embodiment A lightweight hard alloy according to a second embodiment of the present invention is a lightweight hard alloy comprising a hard phase having a core-rim structure, which is obtained by sintering a mixed powder containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component, The titanium compound contains 0.7% by mass or more of oxygen, The hard phase is characterized in that the ratio of the oxygen content in the core phase to the oxygen content in the rim phase (core phase oxygen content / rim phase oxygen content) is 0.9 or more.

[0056] The titanium compound constituting the main component is a carbon-containing titanium compound, specifically at least one compound selected from the group consisting of titanium carbide and titanium carbonitride. Furthermore, titanium nitride may be contained in an amount of up to 5 mass% of the total amount of titanium compounds. Carbon-containing titanium compounds have high hardness and excellent wear resistance, so when they are included as the main component, a lightweight hard alloy with excellent wear resistance can be obtained.

[0057] Here, the term "main component" refers to the carbon-containing titanium compound being the largest in mass ratio among all the compounds other than the binder phase components. The mass ratio of the titanium compound to the total amount of compounds other than the binder phase components is preferably greater than 50%, and the mass ratio of the carbon-containing titanium compound is preferably 1.5 to 5 times, and more preferably 2 to 4 times, the total amount of the other compounds.

[0058] In a second embodiment, the titanium compound in the mixed powder contains 0.7% by mass or more of oxygen. By using titanium compound powder containing 0.7% by mass or more of oxygen, the titanium compound powder is less likely to be finely powdered, and the rim phase thickness of the hard phase of the resulting lightweight hard alloy is reduced, thereby improving toughness. Furthermore, by adding an appropriate amount of oxygen to the titanium compound powder, the effect of suppressing rim phase growth can also be expected.

[0059] In the lightweight hard alloy of this embodiment, the ratio of the oxygen content in the core phase of the hard phase to the oxygen content in the rim phase (core phase oxygen content / rim phase oxygen content) is 0.9 or more. This configuration can be achieved by using a titanium compound powder containing 0.7% or more by mass of oxygen. The amount of oxygen dissolved in TiC, WC, MoC, and Ni is usually as low as 0.3% or less by mass, but the surface area increases due to mixed grinding, which increases the amount of adsorbed oxygen and increases the amount of oxygen in the mixed powder. When a compact of this mixed powder is sintered, the rim phase contains a large amount of oxygen due to the adsorbed oxygen, so the amount of oxygen in the rim phase is greater than the amount of oxygen in the core phase (core phase oxygen content / rim phase oxygen content) is less than 0.9. On the other hand, when a titanium compound containing 0.7% or more by mass of oxygen is used as the main component, the amount of oxygen in the core phase composed of such a titanium compound phase is large, so the ratio of the oxygen content in the core phase of the hard phase to the oxygen content in the rim phase (core phase oxygen content / rim phase oxygen content) is 0.9 or more. The above ratio is preferably 0.95 or more, more preferably 1.0 or more, and even more preferably 1.05 or more.

[0060] The oxygen content in the titanium compound powder is preferably 0.7 to 2.5% by mass. If the oxygen content exceeds 2.5% by mass, sinterability decreases. The oxygen content in the titanium compound powder is preferably 0.8 to 2.4% by mass, more preferably 1.0 to 2.3% by mass, and even more preferably 1.2 to 2.2% by mass.

[0061] The nitrogen content in the titanium compound powder is preferably 0.7% by mass or more but less than 8% by mass. If the oxygen content is less than 0.7% by mass, fine powder is more likely to be generated by mixed pulverization than when the oxygen content is not 0.7%, while if it is 8% by mass or more, the grindability of the sintered alloy is reduced. The nitrogen content in the titanium compound powder may be 0.7 to 2.5% by mass. If the oxygen content in the titanium compound powder is 0.7 to 2.5% by mass and the nitrogen content is 0.7% by mass or more but less than 2.5% by mass, the titanium compound powder is particularly difficult to pulverize by mixed pulverization and is less likely to generate fine powder. As a result, a large amount of a core phase with excellent wear resistance remains in the sintered alloy, and peripheral structures are less likely to form, resulting in a lightweight hard alloy with high toughness.

[0062] When the oxygen and nitrogen contents are both less than 0.7% by mass, fine powder is more likely to be generated during co-milling than when they are not. The fact that titanium compounds containing appropriate amounts of oxygen and nitrogen are less likely to generate fine powder during co-milling also indicates that the titanium compound itself has high toughness. As a result, as mentioned above, peripheral structures are less likely to form during sintering, a large amount of core phase remains, the degree of adhesion between hard phases is reduced, and the toughness of the sintered alloy is increased. At the same time, by setting the ratio of hard phases having a core-rim structure (core phase oxygen content / rim phase oxygen content) to 0.9 or more, the toughness of the core portion of the core-rim structure itself is also increased. Therefore, compared to sintered alloys with this ratio less than 0.9, fine chipping is less likely to occur during tool use and the wear resistance is higher.

[0063] The number of hard phases having a core-rim structure is preferably 25% or more of the total number of hard phases, more preferably 40% or more, even more preferably 55% or more, and particularly preferably 65% ​​or more. The number of hard phases is determined by photographing 10 fields of view of an arbitrary cross-sectional SEM structure (5,000x magnification) of the lightweight hard alloy, processing the images, and counting the number of hard phases with a diameter of 0.2 μm or more among the diameters of circles converted from the area of ​​each hard phase. Among these hard phases with a diameter of 0.2 μm or more, those in which a core-rim structure can be observed are considered to have a core-rim structure.

[0064] One example of the lightweight hard alloy according to the second embodiment of the present invention is a lightweight hard alloy containing a hard phase having a core-rim structure, which is obtained by sintering a mixed powder containing a titanium compound consisting of titanium carbide and / or titanium carbonitride as a main component, containing 5 to 33 mass% of WC and / or MoC, and containing 5 to 40 mass% of at least one selected from the group consisting of Ni, Co, and Fe as a binder phase component, The titanium compound contains 0.7% by mass or more of oxygen, The ratio of the oxygen content in the core phase of the hard phase to the oxygen content in the rim phase (core phase oxygen content / rim phase oxygen content) is 0.9 or more.

[0065] The composition of the mixed powder used in this example may be the same as that of the example of the first embodiment, and a description of other parts common to the first embodiment will be omitted.

[0066] In the lightweight hard alloy according to the second embodiment of the present invention, as in the first embodiment, in the cross-sectional structure of the lightweight hard alloy observed with a scanning electron microscope, the core phases having a core-rim structure may have an average particle size of D90 or more on a number basis in the particle size distribution of the area circle diameter of the core phases, and the average Dmax / Dmin of the shortest length Dmin to the longest length Dmax of the straight line connecting the center of gravity of the core phases having D90 or more to the outline may be 2.0 or less. When the titanium compound in the mixed powder contains 0.7% by mass or more of oxygen, fine powder is unlikely to be produced, and a large amount of the core phase having excellent wear resistance remains in the sintered alloy, making it easier to obtain a hard phase having the core-rim structure.

[0067] As with the first embodiment, the lightweight hard alloy according to the second embodiment of the present invention preferably has a mixed powder BET value x theoretical specific gravity of not more than 38. In a lightweight hard alloy obtained by sintering a compact of a mixed powder containing as a main component a titanium compound consisting of titanium carbide and / or titanium carbonitride, and including a hard phase with a core-rim structure, if the titanium compound contains 0.7 mass% oxygen, the ratio of the oxygen content in the core phase of the hard phase to the oxygen content in the rim phase (core phase oxygen content / rim phase oxygen content) is 0.9 or more, and the mixed powder BET value x theoretical specific gravity is 38 or less, it is possible to suppress the formation of a peripheral structure with low strength and an increase in the adhesion of the hard phase, and a lightweight hard alloy with excellent toughness and high strength can be obtained.

[0068] [2] Manufacturing method for lightweight hard alloys One example of a method for producing the lightweight hard alloy of the present invention is a method in which powders of the above-mentioned hard phase constituent particles and binder phase constituent particles are blended, wet mixed and pulverized in an organic solvent, dried, and then a binder such as paraffin is added to the powder, which is then pressure-molded to form a compact, and the compact is sintered to obtain a lightweight hard alloy.

[0069] The compact of the mixed powder may be formed by press molding into a shape close to the finished product (near net shape), or may be further machined to give a predetermined shape, or may be machined after preliminary sintering to give a predetermined shape.

[0070] The sintering atmosphere can be a vacuum or an inert gas. When sintering a compact made of a nitrogen-containing mixed powder, nitrogen or a nitrogen-containing mixed gas, or CO gas, can be used. The introduction temperature and gas pressure of these atmospheric gases can be varied depending on the purpose. The heating rate, sintering temperature and holding time, as well as the temperature holding and gas pressure along the way, can be selected as desired depending on the purpose, such as degreasing, improving sinterability, adjusting the structure and composition of the surface layer, or improving surface properties.

[0071] Titanium compounds include TiC produced by the Menstrum process, and Ti(C,N), which is produced by heating and carbonitriding titanium metal, titanium hydride, titanium oxide, etc., as the main raw materials. However, the finished titanium compound is often pulverized and classified to control the particle size within a specified range. The pulverization process produces powder that is much finer than the desired particle size. It has been discovered that the presence of a certain amount of this fine powder in titanium compound powder is one of the causes of the low toughness of lightweight hard alloys. To improve the toughness of lightweight hard alloys made using this titanium compound powder, simply reduce the amount of fine powder in the mixed powder before sintering.

[0072] For this reason, it is necessary to select mixing conditions that do not easily produce fine powder. It is necessary to set conditions that will allow a predetermined average particle size to be obtained even if the mixing time is shortened. For example, in the case of mixing and grinding using a ball mill, mixing conditions such as the ball mill rotation speed, amount of powder, amount of solvent, amount of balls, ball diameter, ball material, and mixing and grinding time can be set. Any of the parameters can be changed, and the specific surface area (m 2 It was found that it is essential that the value obtained by multiplying the theoretical specific gravity (g / g) be 38 or less. Furthermore, in the course of investigating this, it was found that, as mentioned above, some raw powders contain fine particles at the raw powder stage, and that the fine particles can be removed by various methods such as classification, or that the same effect can be obtained by using a titanium compound powder with less fine particles.

[0073] The sintering temperature is preferably 1330 to 1450°C so as not to cause excessive growth of the structure around the hard phase. Depending on the application, sinter-HIP may be used, or a normally sintered sintered body may be subjected to HIP treatment. Sintering may be performed by hot press sintering or electromagnetic energy assisted sintering such as electric current sintering or SPS sintering.

[0074] [3] Lightweight hard alloy components The lightweight hard alloy of the present invention is suitable for use in large, wear-resistant components that rotate at high speeds, such as screws and crushing blades. Therefore, lightweight hard alloy components using the lightweight hard alloy of the present invention can demonstrate excellent performance when used, for example, in components for crushing, mixing, or kneading. Furthermore, the lightweight hard alloy of the present invention is not limited to these applications. Because it is less likely to crack during tool use, it can also be used for punching punches, room-temperature, warm- and hot-working forming dies, extrusion dies, metal molds, and forging punches. Furthermore, because it is less likely to chip or crack during handling, it is effective for use in peripheral components for lens molding, such as barrel dies for special lenses, which have a large thermal expansion coefficient.

[0075] The lightweight hard alloy member of the present invention is not limited to the wear-resistant tools and members described above, but is also effective in cutting tools such as insert tips, end mills, drills, etc. The lightweight hard alloy member of the present invention may have a hard coating applied to its surface by DLC or PVD, or may have a hard coating applied to its surface by CVD depending on the application. [Example]

[0076] The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0077] Example 1 As raw material powders, TiC powder (1.4 μm, 1.5 μm, 1.6 μm, 3.5 μm), Ti(C 0.7 N 0.3 ) powder (1.6 μm, 1.7 μm), (Ti,Mo)(C,N) powder (1.5 μm), (Ta,Nb)C powder (Ta:Nb=9:1, 2.1 μm), WC powder (0.6 μm), Mo2C powder (3.2 μm), Cr3C2 powder (1.3 μm), Ni powder (2.4 μm), Co powder (1.9 μm), and Fe powder (3.5 μm) were prepared. The values ​​in parentheses indicate the average particle size measured by the Fischer particle size measurement method (FSSS method). The (Ti,Mo)(C,N) powder has the composition Ti(C 0.7 N 0.3The mixed powder was subjected to a solid solution treatment by heat treatment in nitrogen to obtain a solid solution of Ti(C)-25 mass% MoC (oxygen content: 0.51 mass%, nitrogen content: 5.56 mass%), and the resulting solid solution was then crushed and classified. 0.7 N 0.3 The powders contained oxygen and nitrogen in the amounts shown in Table 2. These raw material powders were weighed so that the sintered bodies had the compositions shown in Table 1 for each sample.

[0078] TiC powder, Ti(C 0.7 N 0.3 The titanium compound raw powders (Ti,Mo)(C,N) and (Ti,Mo)(C,N) were observed under an SEM, and those with relatively little fine powder were classified as "low," while those with relatively much fine powder, which were likely due to pulverization and classification, were classified as "high." The results are shown in Table 2.

[0079] The weighed powders were mixed and wet mixed and pulverized using a ball mill. For the inventive product, the mixing and pulverization conditions were adjusted taking into consideration the amount of fine powder contained in the titanium compound raw powder so that the BET value x theoretical specific gravity was 38 or less and the average particle size of the hard phase of the resulting sintered body was within the range of 0.8 to 3.5 μm. The crushing intensity level was rated as "2" for normal strength, "1" for weaker strength, "3" for stronger strength, and "4" for strength stronger than crushing level "3." The crushing levels of the mixed powder for each sample are shown in Table 3.

[0080] The powder after pulverization and mixing was dried in a vacuum dryer, and the particle size distribution of the resulting mixed powder was measured using an MT3300EXII (Microtrack Bell Co., Ltd.), and the amount of particles with a particle size of 0.8 μm or less (A) was calculated as a volume ratio. The results are shown in Table 3.

[0081] The BET value of the mixed powder was measured using a TriStar II 3020 (Micromeritics). The theoretical specific gravity of the mixed powder was calculated from the specific gravity and composition ratio of the raw material powder for each sample. The BET value x theoretical specific gravity of each sample is shown in Table 3.

[0082] A binder was added to the mixed powder, and the strength was 98 N / mm 2The powder was pressed into a cylinder of φ20 × 20 mm H (mm) under a pressure of 1000 kJ / cm, and then sintered at a sintering temperature of 1400°C for 1 hour to produce invention products 1 to 16 and comparison products 1 to 4. Test pieces for the transverse strength test were also prepared in the same manner after the powder was pressed into a rectangular parallelepiped of 6 × 11 × 31 mm.

[0083] The Vickers hardness of each sample was measured using a Vickers hardness tester HV (294N). The results are shown in Table 4.

[0084] The sintered body of each sample was cut, and the cross section was mirror-polished. SEM photographs (magnification: 8,000x) of the polished cross section were then taken using a Regulus 8100 (Hitachi High-Tech Corporation). The average grain size of the hard phase was determined using the SEM photographs. The average grain size of the hard phase was calculated using the Fullman equation. The results are shown in Table 4.

[0085] Using SEM photographs (magnification: 5,000x) showing the polished cross sections of the above samples, the average particle size of the core phases with a core-rim structure, D90 or larger on a number basis, was determined in the particle size distribution of the area circle diameter of the core phases. The results are shown in Table 4.

[0086] The oxygen content of the hard phases (core and rim phases) of the lightweight hard alloys was measured using an energy dispersive X-ray analyzer, QUANTAX FlatQUAD (manufactured by Bruker), and the ratio of the oxygen content of the core phase to the oxygen content of the rim phase (core phase oxygen content / rim phase oxygen content) was calculated. The results are shown in Table 4.

[0087] Using the SEM photographs, the particle size distribution of the core phase's equivalent diameter was determined using Image-Pro Plus. Furthermore, the shortest and longest lengths Dmin and Dmax of the straight lines connecting the center of gravity of the core phase with a particle size of D90 or greater on a number basis to its outline were determined, and the average value of the Dmax / Dmin ratio was calculated. The results are shown in Table 4.

[0088] The transverse strength of each sample was measured by a three-point bending test based on JISR 1601. The fracture toughness value K ICwas measured and calculated based on JISR 1607. The results are shown in Table 4.

[0089] To evaluate the wear resistance of each sample (resistance to wear as a tool), a blasting machine was used to bombard each sample with SiC powder (grain size: #500) at a projection angle of 30°, a projection pressure of 0.6 MPa, and a projection time of 90 seconds. The degree of wear of each sample after blasting was evaluated on a scale of 0 to 5. For Invention Product 3, a rating of "4" was given for a wear amount of 0.9 to less than 1.1 times, a rating of "5" for less than 0.9 times, a rating of "3" for a wear amount of 1.1 to less than 1.5 times, a rating of "2" for a wear amount of 1.5 to less than 1.9 times, a rating of "1" for a wear amount of 1.9 to less than 2.3 times, and a rating of "0" for a wear amount of 2.3 times or more. The results are shown in Table 4.

[0090] To evaluate the chipping resistance (resistance to chipping as a tool; toughness) of each sample, a diamond wheel grinder (#140) was used to perform surface grinding at a cutting depth of 5 μm to create a 20° sharp edge. The size of the chip at the tip of each sample's sharp edge was evaluated on a scale of 0 to 5. A chip width of 0.9 to 1.1 times the chip width of Invention Product 3 was evaluated as "4," less than 0.9 times was evaluated as "5," 1.1 to 1.2 times was evaluated as "3," 1.2 to 1.3 times was evaluated as "2," 1.3 to 1.4 times was evaluated as "1," and 1.4 times or greater was evaluated as "0." If the chipping resistance did not meet the evaluation criteria of "1," i.e., the evaluation was "0," the wear resistance was not evaluated. If either the wear resistance or the chipping resistance was evaluated as "0," the sample could not be used as a tool. If all ratings are "1" or higher and the total is "5" or higher, then depending on the application, an alloy that prioritizes either toughness or wear resistance, or an alloy with a good balance of toughness and wear resistance, can be selected. The results are shown in Table 4.

[0091] [Table 1]

[0092] [Table 2]

[0093] [Table 3]

[0094] [Table 4]

[0095] Invention products 1 to 15 have an average particle size of the core phase of D90 or more in the range of 0.8 to 3.3 μm, and an average ratio Dmax / Dmin of the core phase of D90 or more of 2.0 or less, and are excellent in wear resistance and chipping resistance, as well as in transverse rupture strength, and can achieve both lightweight and high toughness.

[0096] Invention Product 12 uses a titanium compound powder with a low amount of fine powder, resulting in a Dmax / Dmin of 2 or less. However, the oxygen content of the powder is low at 0.19 mass%, resulting in a slightly lower overall evaluation of wear resistance and chipping resistance compared to the other invention products. Invention Product 13 also has a Dmax / Dmin of 2 or less, but the oxygen content of the titanium compound powder is lower than the specified amount and the amount of fine powder is high, resulting in poor chipping resistance and wear resistance. The overall evaluation is lower than Invention Products 6 to 10. Invention Product 16 uses a titanium compound with a low amount of fine powder, but the amount of fine powder is high due to the high level of mixing and grinding, resulting in a Dmax / Dmin slightly exceeding 2. However, the oxygen content of the powder is high at 0.89 mass%, achieving both wear resistance and chipping resistance. Comparative Products 1 to 3 have a Dmax / Dmin of over 2 and a low oxygen content of 0.59 mass%, resulting in a poor overall evaluation of wear resistance and chipping resistance compared to the other invention products.

[0097] Arbitrary cross-sectional SEM structures (15,000x magnification) were photographed for Invention Products 8 and 13. The obtained SEM photographs are shown in Figures 3 and 4. The core phase (black, circled area) and rim phase (gray, straight line area) in each SEM photograph were subjected to the aforementioned EDS analysis to determine the oxygen content, and based on this, the ratio of the oxygen content in the core phase to the oxygen content in the rim phase of the hard phase of Invention Products 8 and 13 lightweight hard alloys was calculated.

[0098] The ratio of the oxygen content in the core phase to the oxygen content in the rim phase of the lightweight hard alloy of invention product 8 (oxygen content in core phase / oxygen content in rim phase) was approximately 1.13, while the ratio of the oxygen content in the core phase to the oxygen content in the rim phase of the lightweight hard alloy of invention product 13 (oxygen content in core phase / oxygen content in rim phase) was approximately 0.69.

Claims

1. A lightweight hard alloy comprising a hard phase having a core-rim structure, the hard phase being composed of a core phase mainly composed of the titanium compound and a rim phase which is a solid solution of the titanium compound and W and / or Mo, the hard phase being obtained by sintering a mixed powder containing 5 to 33 mass % of W and / or Mo in terms of carbide, and 5 to 40 mass % of at least one selected from the group consisting of Ni, Co and Fe as a binder phase; In a cross-sectional structure of the lightweight hard alloy observed with a scanning electron microscope, the average particle size of the core phase of D90 or more on a number basis in the particle size distribution of the area circle equivalent diameter of the core phase among the hard phases having a core-rim structure is 0.8 to 3.3 μm, and the average ratio Dmax / Dmin of the shortest length Dmin to the longest length Dmax of the straight line connecting the center of gravity of the core phase of D90 or more to the outline is 2.0 or less, the number of hard phases having a core-rim structure is 30% or more of the total number of hard phases; A lightweight hard alloy characterized in that the oxygen content of the titanium compound is 0.19 to 2.5 mass%, the nitrogen content of the titanium compound is 0.08 mass% or more but less than 8 mass%, and the ratio of the oxygen content of the core phase to the oxygen content of the rim phase of the hard phase (core phase oxygen content / rim phase oxygen content) is 0.59 or more.

2. When the amount of particles having a particle size of 0.8 μm or less contained in the mixed powder is A (volume %), the particle amount A is expressed by the following formula (1) relative to the content X (volume %) of at least one selected from the group consisting of Ni, Co, and Fe contained in the mixed powder: A<-1.3X+53.4 ・・・(1) 2. The lightweight hard alloy according to claim 1, wherein the content of C is 20% by volume or less.

3. The mixed powder further contains Cr. 3 C 2 2. The lightweight hard alloy according to claim 1, characterized in that it contains 8 mass % or less of the Cr-based alloy, a part of which is present in solid solution in the rim phase.

4. The lightweight hard alloy according to any one of claims 1 to 3, characterized in that the mixed powder contains 15 mass% or less of elements of Groups 4 to 6 of the periodic table other than Ti, W, Mo and Cr in terms of carbide, and a part of these elements is solid-solved in the rim phase.

5. 4. The lightweight hard alloy according to claim 1, wherein the nitrogen content of the titanium compound is 0.7% by mass or more and less than 8% by mass.

6. A lightweight hard alloy member using the lightweight hard alloy according to any one of claims 1 to 3.

Images