Cemented carbide for cutting tool and cutting tool using same

Abstract

A cemented carbide for a cutting tool, the cemented carbide containing hard phases that have an average particle diameter of 0.5-4.0 μm and γ phases that have an average particle diameter of 1.0-4.0 μm. Taking a, b, c, d, and e to represent, respectively, the average atomic number ratio of Ti, Zr, Nb, Ta, and W contained in each of the γ phases (where a + b + c + d + e = 100.0), the average values aavg, bavg, cavg, davg, and eavg (where aavg + bavg + cavg + davg + eavg = 100.0) are 20.0 ≤ a ≤ 30.0, 20.0 ≤ b ≤ 30.0, 10.0 ≤ c ≤ 20.0, 20.0 ≤ d ≤ 30.0, and 5.0 ≤ e ≤ 15.0, and the average value of σa, σb, σc, σd, σe, which are standard deviations of a, b, c, d, and e, respectively, is 0.40 or less.

Description

Cemented carbide for cutting tools and cutting tools using said alloy

[0001] The present invention relates to a cemented carbide (WC-based sintered alloy) and a cutting tool using the alloy. This application claims priority to Japanese Patent Application No. 2023-056798, filed on March 30, 2023. The entire contents of this Japanese patent application are incorporated herein by reference.

[0002] Cemented carbide has excellent mechanical strength, thermal fatigue resistance, etc., and is therefore used in tools that are subjected to large impact forces and thermal cycles, such as cutting tools, drilling tools, and metal forming tools.

[0003] On the other hand, the conditions for using tools are becoming more and more efficient, and tools are being required to have even greater durability. Therefore, proposals have been made to improve the aforementioned characteristics of the cemented carbide used in tools.

[0004] For example, Patent Document 1 describes a cemented carbide containing a composite carbide (solid solution) of (Ti, W, Ta, Nb, Zr), and claims that by replacing part of the Ta with inexpensive Nb and Zr, the cemented carbide reduces manufacturing costs and does not lose performance even when used for cutting purposes.

[0005] Chinese Patent Application Publication No. 1425787

[0006] The present invention has been made in consideration of the above circumstances and proposals, and aims to provide a cemented carbide that can be used to form a cutting tool having a cutting edge with excellent resistance to plastic deformation and fracture resistance, even when used in cutting stainless steel.

[0007] A cemented carbide for cutting tools according to an embodiment of the present invention contains 5.0 to 15.0 mass% Co and Ni in total, 4.0 to 12.0 mass% Ti, Zr, Nb, and Ta in total, 5.4 to 6.5 mass% C, and the balance being W and inevitable impurities, and includes a hard phase mainly composed of W carbide, a binder phase mainly composed of Co and Ni, and a γ phase mainly composed of Ti, Zr, Nb, Ta, and W carbides, the hard phase mainly composed of W carbide having an average grain size of 0.5 to 4.0 μm and the γ phase having an average grain size of 1.0 to 4.0 μm, and when the average atomic ratios of Ti, Zr, Nb, Ta, and W contained in each of the γ phases are a, b, c, d, and e, respectively (where a+b+c+d+e=100.0), the average value a ａｖｇ , b ａｖｇ , c ａｖｇ , d ａｖｇ , e ａｖｇ (However, a ａｖｇ +b ａｖｇ +c ａｖｇ +d ａｖｇ +e ａｖｇ = 100.0) is 20.0 ≦ a ａｖｇ ≦30.0, 20.0≦b ａｖｇ ≦30.0, 10.0≦c ａｖｇ ≦20.0, 20.0≦d ａｖｇ ≦30.0, 5.0≦e ａｖｇ ≦15.0, and the average value of σa, σb, σc, σd, and σe, which are the standard deviations of a, b, c, d, and e, respectively, is 0.40 or less. The cemented carbide according to the above embodiment may satisfy the following (1).

[0008] (1) The γ phase contains 0.5 mass% or less of Cr, and d is d ａｖｇ The gamma phase in which the gamma 1 phase, which is a region having a grain size 8 or more higher than the above, exists is present in an amount of 20 to 80% by number of all the gamma phases.

[0009] A cutting tool according to an embodiment of the present invention uses the above cemented carbide for cutting tools.

[0010] When the cemented carbide for cutting tools is used as a cutting tool, even when it is used to cut stainless steel, the cutting edge has excellent resistance to plastic deformation and chipping.

[0011] 1 is a schematic diagram showing an example of the structure of a cemented carbide for a tool according to an embodiment of the present invention; 2 is an explanatory diagram showing a method of line analysis; 3 is a schematic diagram showing an example of the amount of plastic deformation on the flank of a cutting edge; 4 is a plan view of the rake face and 5 is a side view of the flank;

[0012] The present inventors have conducted extensive research to obtain a cemented carbide for cutting tools that can achieve the above-mentioned objective. As a result, they have discovered that the above-mentioned objective can be achieved by setting the average grain sizes of the hard phase and γ phase within a predetermined range, and by setting the composition of the γ phase within a predetermined range, i.e., by setting the average atomic ratio of the metal components contained in the γ phase within a predetermined range, and further setting the average value of the standard deviation of each metal component between the γ phase particles within a predetermined range. Hereinafter, a cemented carbide for cutting tools and a cutting tool using the alloy according to an embodiment of the present invention will be described.

[0013] In this specification and claims, when a numerical range is expressed as "M to N" (M and N are both numerical values), this is synonymous with "M or more, N or less," and the range includes the upper limit (N) and lower limit (M) numerical values. When a unit is stated only for the upper limit (N), the lower limit (M) also has the same unit as the upper limit (N). Furthermore, unless otherwise specified, "average" refers to the arithmetic mean.

[0014] 1. Composition and Structure of the Cemented Carbide for Cutting Tools Details of the composition of the cemented carbide for cutting tools according to this embodiment and the structure shown schematically in FIG. 1 are as follows.

[0015] (1) Co and Ni It is preferable that one or both of Co and Ni are contained. The total content of at least one of Co and Ni is preferably 5.0 to 15.0 mass%. This is because, when used as a cutting tool, if the content is less than 5.0 mass%, the chipping resistance is insufficient, while if the content exceeds 15.0 mass%, the plastic deformation resistance is reduced.

[0016] Here, Co and Ni are mainly present in the binder phase (which has crystal grains with an fcc structure, and is indicated by the symbol (1) in FIG. 1 ), and are the main components of the binder phase, i.e., the main components, with the total of Co and Ni atoms accounting for 50 atomic % or more of all components (atoms) constituting the binder phase.

[0017] The binder phase may contain W and C, which are components of the hard phase, one or more of Ti, Zr, Nb, Ta, and W contained in the γ phase, Cr, which controls the growth of the hard phase, and unavoidable impurities. When these elements are present in the binder phase, they are presumed to be in a state of solid solution in the binder phase. The method for identifying the binder phase will be described later.

[0018] (2) Ti, Zr, Nb, Ta Ti, Zr, Nb, and Ta are all contained, and the total content of Ti, Zr, Nb, and Ta is preferably 4.0 to 12.0% by mass. This is because, when used as a cutting tool, if the content is less than 4.0% by mass, the plastic deformation resistance is insufficient, while if the content exceeds 12.0% by mass, the fracture resistance is reduced.

[0019] Ti, Zr, Nb, Ta, and W, which will be described later, are contained in the γ phase. Here, when the average atomic ratios of Ti, Zr, Nb, Ta, and W contained in one γ phase are respectively a, b, c, d, and e (where a+b+c+d+e=100.0), their average value (average value for all measured γ phases) is a ａｖｇ , b ａｖｇ , c ａｖｇ , d ａｖｇ , e ａｖｇ (However, a ａｖｇ +b ａｖｇ +c ａｖｇ +d ａｖｇ +e ａｖｇ = 100.0) is 20.0 ≦ a ａｖｇ ≦30.0, 20.0≦b ａｖｇ ≦30.0, 10.0≦c ａｖｇ ≦20.0, 20.0≦d ａｖｇ ≦30.0, 5.0≦e ａｖｇIt is preferable that the relationship be ≦15.0. Note that a = [Ti] / ([Ti] + [Zr] + [Nb] + [Ta] + [W]) × 100, b = [Zr] / ([Ti] + [Zr] + [Nb] + [Ta] + [W]) × 100, c = [Nb] / ([Ti] + [Zr] + [Nb] + [Ta] + [W]) × 100, d = [Ta] / ([Ti] + [Zr] + [Nb] + [Ta] + [W]) × 100, and e = [W] / ([Ti] + [Zr] + [Nb] + [Ta] + [W]) × 100.

[0020] If the standard deviations of a, b, c, d, and e are σa, σb, σc, σd, and σe, respectively, their average value ((σa+σb+σc+σd+σe) / 4) is preferably 0.4 or less (the lower limit may be 0.0, but in an example of the manufacturing method described later, the lower limit is about 0.1). The reason for this is that if this average value exceeds 0.4, the plastic deformation resistance and fracture resistance will decrease.

[0021] That is, it is preferable that the atomic ratio of the metal components contained in the γ phase is approximately equal within a predetermined range, because this provides excellent resistance to plastic deformation and chipping when used as a cutting tool.

[0022] (3) γ Phase These Ti, Zr, Nb, and Ta are contained as carbides (not limited to stoichiometric composition) that constitute the gamma phase, i.e., as the main components. The term "main components" refers to the fact that the total amount of carbides of these elements accounts for 50 atomic % or more of all the elements (atoms) that make up the gamma phase. In addition to these carbides, the gamma phase may also contain WC contained in the hard phase, Co and Ni contained in the binder phase, and unavoidable impurities. In Figure 1, the gamma phases are indicated by symbols (3) and (4), and some of the gamma phases (symbol (4)) contain a gamma phase (symbol (5)) with a different composition.

[0023] The average grain size of the γ phase is preferably 1.0 to 4.0 μm. The reason for this is that when the cemented carbide for cutting tools is used as a cutting tool, a grain size of less than 1.0 μm results in insufficient fracture resistance, while a grain size of more than 4.0 μm results in insufficient resistance to plastic deformation. Here, the average grain size of the γ phase refers to the circle-equivalent diameter, i.e., the diameter of a circle having an area equal to that of the γ phase, and the method for measuring this will be described later.

[0024] Inside the γ phase, d is ａｖｇ It is more preferable that the γ phases containing γ1 phases, which are in a region where γ is 8 or more higher than γ (in an example of a manufacturing method described later, γ has an upper limit of 22), are present in an amount of 20 to 80% by number of all the γ phases. The presence of a predetermined proportion of γ phases containing γ1 phases further improves plastic deformation resistance and fracture resistance.

[0025] (4) C C is contained to form carbides and is mainly contained in the hard phase, γ phase, and γ1 phase. Its content is preferably 5.4 to 6.5 mass%, and within this content range, sufficient amounts of carbides can be formed in the hard phase, γ phase, and γ1 phase.

[0026] (5) Cr Cr is an optional component and may be contained in an amount of less than 0.5% by mass. In other words, the inclusion of Cr is not essential. Cr dissolves in Cr in the binder phase, suppresses the growth of W carbides contained in the hard phase, refines the W carbides, and creates a structure with a narrow grain size distribution, thereby improving the toughness of the cemented carbide and improving its resistance to plastic deformation. This function is impaired if the Cr content exceeds 0.5% by mass, causing precipitation of Cr-W composite carbides in the binder phase, reducing toughness and potentially becoming the starting point for chipping.

[0027] (5) W W is the main component of the hard phase, that is, the main component, and W carbides (mostly WC, but not limited to the stoichiometric composition) account for 50 atomic % or more of all the components (atoms) that make up the hard phase (shown by the symbol (2) in Figure 1).

[0028] (6) hard phase Hard phase may contain binder phase components, γ phase components, Cr, and the inevitable impurities that are inevitably mixed in during manufacturing process.In addition, the crystal structure of hard phase is hcp structure, so it is different from the crystal structure of γ phase that is fcc structure.In addition, the method of identifying hard phase will be described later.

[0029] The average grain size of the hard phase is preferably 0.5 to 4.0 μm. The reason for this is that when used as a cutting tool, if the average grain size is less than 0.5 μm, the chipping resistance is insufficient, while if it exceeds 4.0 μm, the plastic deformation resistance decreases. Here, the average grain size of the hard phase refers to the circle-equivalent diameter, i.e., the diameter of a circle having an area equal to that of the hard phase, as with the γ phase, and the measurement method thereof will be described later.

[0030] (7) Inevitable Impurities As described above, the hard phase, γ phase, and binder phase may contain impurities that are inevitably (unintentionally) mixed in during the manufacturing process, and the amount of impurities is preferably 0.3% by mass or less, with the total amount of the cemented carbide being 100% by mass.

[0031] 2. Measurement Method (1) Measurement of Composition of Cemented Carbide for Cutting Tools The surface or cross section of a cemented carbide for cutting tools is mirror-finished using, for example, a focused ion beam (FIB) device, a cross-section polisher (CP) device, or the like. Then, this mirror-finished surface is observed in multiple fields (e.g., 5 fields at 4000x magnification) using a field emission scanning electron microscope (SEM) (each field is, for example, a square measuring 25 μm (vertical) × 25 μm (horizontal)). Area analysis is then performed using an electron probe microanalyzer (EPMA) to measure the composition for each field. Here, the beam diameter of the EPMA can be, for example, 1 μm. The alloy compositions obtained in each measurement field are then averaged to determine the composition of the entire alloy.

[0032] (2) Average atomic ratios of Ti, Zr, Nb, Ta, and W contained in the γ phase: The hard phase, γ phase, and binder phase are identified by the following measurements: 1) For the mirror-finished surface on which the composition of the entire cemented carbide for cutting tools is measured, a rectangular observation field of, for example, 24 μm (vertical) × 72 μm (horizontal) is set as one field of view on the mirror-finished surface, and EBSD patterns and EDS data are simultaneously captured using a field emission scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and an electron backscatter diffraction (EBSD) measurement device. Examples of EDS and EBSD devices include, but are not limited to, the OIM Data Collection manufactured by EDAX / TSL (now AMETEK). Measurement conditions using the field emission scanning electron microscope (SEM) include, but are not limited to, an acceleration voltage of 15 kV and a measurement point spacing of 50 nm.

[0033] Examples of software used for analyzing EBSD patterns include OIM Data Collection version 6 manufactured by TSL and OIM Analysis version 7 manufactured by TSL, but are not limited to these as long as they are capable of performing similar analyses.

[0034] 2) From the analysis of EBSD pattern, for all the measurement points that are identified as fcc phase and hcp phase, calculate the average value of the EDS count value of Co and Ni that are detected, and the measurement points that are identified as fcc phase and hcp phase that have the EDS count value of Co and Ni that is higher than this average value are considered as binder phase.The measurement points that are judged to have hcp crystal structure other than the binder phase that is identified as hcp phase are considered as hard phase, and the remaining measurement points are considered as γ phase.

[0035] 3) Here, when the measurement results of adjacent EBSD measurement points indicate the same phase, the boundary between those measurement points is determined to be a phase interface only when the difference in orientation obtained from both measurement points is 5 degrees or more.

[0036] 4) EPMA line analysis is performed on the γ phase determined in this manner. EPMA line analysis will be explained with reference to FIG. 2. In FIG. 2, the γ phase (4) to be measured is shown to have a γ1 phase (5) therein. However, the γ phase (3) not containing the γ1 phase shown in FIG. 1 is also included in the measurement. The observation field is, for example, a rectangle measuring 24 μm in length and 72 μm in width, and a reference line (6) is set within the observation field, tangent to the phase interface of the γ phase (4) to be measured (although in FIG. 2, the reference line (6) is horizontal to the observation field, this is not limited to horizontal). A measurement line (7) is set parallel to the reference line (6) at an interval of 1 / 10 of the average grain size of the γ phase (determined without distinguishing between those containing and not containing the γ1 phase), which is determined separately as described below.

[0037] The measurement lines (7) are set at the same intervals until they no longer penetrate the gamma phase (4) to be measured. EPMA line analysis is performed on all measurement lines (7) within the gamma phase (4) to be measured, with measurement point intervals of 50 nm, and the atomic ratios of Ti, Zr, Nb, Ta, and W relative to all atoms measured at each measurement point, i.e., a, b, c, d, and e, are measured. Here, the EPMA beam diameter can be 50 nm, for example. The EPMA line analysis (beam diameter can be 50 nm, for example) is performed on four different gamma phases per observation field to determine the atomic ratios of Ti, Zr, Nb, Ta, and W contained in the gamma phase. This atomic ratio is similarly determined for five or more observation fields, and all measured values ​​of at least 20 gamma phases obtained are averaged, resulting in a ａｖｇ , b ａｖｇ , c ａｖｇ , d ａｖｇ and e ａｖｇ When the number of γ phases in one observation field is less than 4, the number of observation fields is increased so that the total number of γ phases to be measured is at least 20, and a ａｖｇ , b ａｖｇ , c ａｖｇ , d ａｖｇ and e ａｖｇ Ask for.

[0038] (3) Average grain size of hard phase and γ phase While measuring and analyzing the EBSD patterns described above, the average grain size of the phases identified as hard phases and γ phases is measured. The average grain size of both phases is measured by determining the area of ​​at least 300 phases for each type of phase, calculating the diameter of a circle equal to each area, and averaging the diameters. Examples of software used to measure the average grain size include OIM Data Collection version 6 manufactured by TSL and OIM Analysis version 7 manufactured by TSL, but are not limited to these as long as it can perform a similar analysis.

[0039] (4) The ratio of the number of γ phases in which γ1 phases exist. In the above-mentioned EPMA line analysis in which the average atomic ratios of Ti, Zr, Nb, Ta and W contained in the γ phases were measured, d was d for all measurement points in one γ phase to be measured. ａｖｇ When the percentage of measurement points with a value 8 or more higher than γ1 is 1.4% or more, the γ phase is considered to have γ1 phase inside. At least 20 γ phases are measured to check for the presence or absence of γ1 phase, and the percentage of γ phases that have γ1 phase inside them is calculated relative to the total number of γ phases examined.

[0040] 3. Manufacturing Method The cemented carbide for cutting tools according to this embodiment and cutting tools using the cemented carbide can be manufactured, for example, as follows. Raw material powders such as WC powder, Co powder, and carbide powder containing Ti, Zr, Nb, and Ta are prepared, wet-mixed, dried, and press-molded into the desired cutting tool shape, followed by sintering. Sintering is performed by holding the mixture at a temperature between 1440 and 1470°C for 1 to 3 hours, cooling to 1200°C, and then holding the mixture at 1200°C for 0 to 24 hours (holding for 0 hours means no holding).

[0041] The carbide powder containing Ti, Zr, Nb, and Ta may be a powder of any one of Ti carbide, Zr carbide, Nb carbide, and Ta carbide, as long as all of Ti, Zr, Nb, and Ta are contained in the cemented carbide for cutting tools, or may be a powder of a plurality of composite carbides containing two or more of Ti, Zr, Nb, and Ta.

[0042] The cemented carbide for tools of the present invention will be specifically described with reference to an example in which it is used as a cutting tool in an insert for turning, but the present invention is not limited to this example.

[0043] First, as powders for sintering, WC powder with a Fischer particle size of 1.5 to 6.0 μm, Co powder with a Fischer particle size of 1.2 μm, Ni powder with a Fischer particle size of 1.3 μm, Cr powder with a Fischer particle size of 1.0 μm, ３ C ２ Powder, Fischer particle size 1.1 μm (Ti ０．２５ Zr ０．２５ Nb ０．２５ Ta ０．２５ ) C powder, Fischer particle size of 1.1 μm (Ti ０．１５ Zr ０．１５ Nb ０．３５ Ta ０．３５ ) C powder, Fischer particle size of 1.1 μm (Ti ０．３５ Zr ０．３５ Nb ０．１５ Ta ０．１５ ) C powder, TiC powder with a Fischer particle size of 1.0 μm, ZrC powder with a Fischer particle size of 1.2 μm, NbC powder with a Fischer particle size of 1.1 μm, and TaC powder with a Fischer particle size of 1.1 μm were prepared.

[0044] Next, these powders were blended to obtain the composition shown in Table 1 to prepare powders for sintering, which were then wet mixed in a ball mill for 72 hours, dried, and then press-molded at a pressure of 100 MPa to prepare powder compacts.

[0045] Next, these powder compacts were subjected to a liquid phase sintering (main sintering) process in which they were held at a predetermined temperature for a predetermined time. In this example, the main sintering was performed under the conditions shown in Table 2, i.e., in a vacuum atmosphere of 0.1 Pa or less, by heating to a holding temperature range of 1440°C and holding at that temperature for 2 hours, or by heating to a holding temperature range of 1470°C and holding at that temperature for 1 hour. The furnace was then maintained in a vacuum atmosphere of 0.1 Pa or less, and the compacts were cooled to 1200°C at a rate of 1 to 20°C / min, and then held at 1200°C for 0 to 20 hours in a vacuum atmosphere of 1 Pa or less (the cooling rate and holding time are shown in Table 2). Then, cemented carbides 1 to 10 (hereinafter referred to as Examples 1 to 10) shown in Table 3 were produced.

[0046] For comparison, comparative cemented carbides 1' to 9' (hereinafter referred to as Comparative Examples 1' to 9') were manufactured using the manufacturing processes of Examples 1 to 10, but with alloy compositions other than those described above, holding temperatures of 1360°C or 1470°C, cooling rates exceeding 20°C / min, and / or holding times at 1200°C of 0 to 1 hour.

[0047] That is, sintering powders blended according to the blending compositions shown in Table 1 were wet mixed in a ball mill for 72 hours, dried, and then press-molded at a pressure of 100 MPa to produce a powder compact. The compact was then sintered under the conditions shown in Table 2, that is, heated to a holding temperature range of 1360°C or 1470°C in a vacuum atmosphere of 0.1 Pa or less and held at that temperature for 1 hour. Thereafter, the inside of the furnace was maintained in a vacuum atmosphere of 0.1 Pa or less, cooled to 1200°C at 70°C / min, and held at 1200°C for 0 to 1 hour, to produce Comparative Examples 1' to 9' shown in Table 4.

[0048] The cross sections of the cemented carbides of Examples 1 to 10 and Comparative Examples 1' to 9' were measured as described above, and the values ​​shown in Tables 3 and 4 were obtained.

[0049]

[0050] In Table 1, "-" indicates that the component was not blended.

[0051]

[0052]

[0053] It was confirmed that the contents of unavoidable impurities in both the Examples and Comparative Examples were within the above-mentioned preferred range.

[0054]

[0055] Next, no coating layer was formed on the surfaces of Examples 1 to 5 and Comparative Examples 1' to 5', but a coating layer having the average total thickness shown in Table 5 was formed by CVD on the surfaces of Examples 6 to 10 and Comparative Examples 6' to 9'. Here, the coating layer was formed by vapor deposition as a three-layer laminated structure, but the number of layers in this laminated structure is not limited to three, and may be one, two, or four or more layers. There are no particular restrictions on the vapor deposition conditions for the hard coating layer, but the TiN, TiCN, and Al in Examples 6 to 10 and Comparative Examples 6' to 9' were formed by vapor deposition. ２ O ３ The chemical vapor deposition conditions were as follows:

[0056] [Chemical Vapor Deposition Conditions for TiN] Reactant gas (volume %): TiCl ４ 2%, N ２ 30%, H ２ Residual reaction pressure: 7 kPa Reaction temperature: 1000°C

[0057] [Chemical vapor deposition conditions for TiCN] Reactant gas (vol %): TiCl ４ 2%, CH ３ CN 0.7%, N ２ 10%, H ２ Residual reaction pressure: 7 kPa Reaction temperature: 900°C

[0058] [Al ２ O ３ Chemical vapor deposition conditions] Reactant gas (volume %): AlCl ３ 2.2%, CO ２ 5.5%, HCl 2.2%, H ２ S 0.2%, H ２ Residual reaction pressure: 7 kPa Reaction temperature: 1000°C

[0059]

[0060] Next, cutting test 1 was performed on Examples 1 to 5 and Comparative Examples 1' to 5' in which no coating layer was formed, and cutting test 2 was performed on Examples 6 to 10 and Comparative Examples 6' to 9' in which a coating layer was formed, and the amount of plastic deformation on the flank of the cutting edge was measured and the state of wear on the cutting edge was observed.

[0061] Cutting test 1: Wet external turning of a round bar (diameter 200 mm) made of alloy steel (JIS SUS304) Workpiece: JIS SUS304 Cutting speed: 250 m / min Depth of cut: 1.8 mm Feed: 0.18 mm / rev Cutting time: 5 minutes (cutting was interrupted every 20 seconds to observe the cutting edge) Wet water-soluble cutting oil was used

[0062] Cutting test 2: Dry external turning of a round bar (diameter 200 mm) made of alloy steel (JIS SUS304) Workpiece: JIS SUS304 Cutting speed: 55 m / min Depth of cut: 1.1 mm Feed: 0.12 mm / rev Cutting time: 5 minutes (cutting was interrupted every 20 seconds to observe the cutting edge) Wet water-soluble cutting oil was used

[0063] After completion of Cutting Test 1 and Cutting Test 2 (after 5 minutes of cutting), the amount of plastic deformation of the cutting edge flank was measured, and the state of wear of the cutting edge was observed. The amount of plastic deformation of the cutting edge flank was measured by drawing a line segment on the ridge where the main cutting edge flank (9) and the rake face (8) intersect at a position sufficiently distant from the cutting edge (10) on the main cutting edge flank (9) of the tool, extending the line segment toward the cutting edge, and measuring the maximum distance between the extended line segment (12) and the cutting edge ridge (perpendicular to the extended line segment), which was taken as the amount of plastic deformation of the cutting edge flank (11). When the amount of plastic deformation of the flank was 0.100 mm or more, the state of wear was considered to be cutting edge deformation (see FIG. 3).

[0064] The results of Cutting Test 1 are shown in Table 6, and the results of Cutting Test 2 are shown in Table 7. In Tables 6 and 7, "flaws due to plastic deformation" refer to the results of interrupting cutting every 20 seconds to observe the cutting edge and confirming whether or not a flaw occurred and whether the flaw was caused by plastic deformation. For the samples where this flaw occurred, the flaw occurred on the cutting edge, making it difficult to distinguish the ridgeline, and the amount of plastic deformation could not be measured, so they are marked as "immeasurable."

[0065]

[0066]

[0067] As is clear from Table 6 showing the results of Cutting Test 1 and Table 7 showing the results of Cutting Test 2, all of the Examples exhibited little plastic deformation on the flank, which affects the tool life, and exhibited excellent toughness and resistance to plastic deformation without uneven wear or chipping. In contrast, all of the Comparative Examples exhibited a large amount of plastic deformation on the tool for the specified cutting time, making it difficult to machine the workpiece to the specified dimensions.

[0068] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0069] REFERENCE SIGNS LIST 1 Binder phase 2 Hard phase 3 γ phase 4 γ phase (γ phase with γ1 phase) 5 γ1 phase 6 Reference line 7 Measurement line 8 Rake face 9 Flank face on main cutting edge side 10 Cutting edge 11 Amount of plastic deformation on flank face of cutting edge 12 Elongated line segment

Claims

1. Co, Ni total 5.0-15.0 mass%, Ti, Zr, Nb, Ta total 4.0-12.0 mass%, C 5.4-6.5 mass%, the balance being W and unavoidable impurities, comprising a hard phase mainly composed of W carbides, a binder phase mainly composed of Co and Ni, and a gamma phase mainly composed of Ti, Zr, Nb, Ta and W carbides, the hard phase mainly composed of W carbides has an average grain size of 0.5-4.0 μm, and the gamma phase has an average grain size of 1.0-4.0 μm, and when the average atomic ratios of Ti, Zr, Nb, Ta and W contained in each of the gamma phases are a, b, c, d and e, respectively (wherein a+b+c+d+e=100.0), the average value a ａｖｇ , b ａｖｇ , c ａｖｇ , d ａｖｇ , e ａｖｇ (However, a ａｖｇ +b ａｖｇ +c ａｖｇ +d ａｖｇ + e ａｖｇ = 100.0) satisfies 20.0≦a≦30.0, 20.0≦b≦30.0, 10.0≦c≦20.0, 20.0≦d≦30.0, and 5.0≦e≦15.0, and the average values ​​of σa, σb, σc, σd, and σe, which are standard deviations of a, b, c, d, and e, respectively, are 0.40 or less.

2. Contains 0.5 mass% or less of Cr, and d is present inside the γ phase. ａｖｇ The cemented carbide for cutting tools according to claim 1, characterized in that γ phases in which γ1 phases, which are in a region having a grain size 8 or more higher than the grain size, are present in an amount of 20 to 80% by number with respect to all of the γ phases.

3. A cutting tool using the cemented carbide for cutting tools according to claim 1 or 2.

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