Hard alloy tool

Abstract

Disclosed is a cemented carbide tool for stamping, the cemented carbide tool comprising: a WC phase and a binder phase containing Co; wherein the average particle size X [mu] m of the WC phase and the total amount Y mass% of the binder phase satisfy the following formulae (1), (2) and (3): X < = 1.2 (1) 2 < = Y (2)-6.7 X + 6 < = Y < =-14 X + 38 (3); and wherein the cemented carbide tool contains from 2% by mass to 20% by mass of Cr and / or V (calculated as carbide) with respect to the total amount of the binder phase.

Description

Technical Field

[0001] The invention relates to a cemented carbide tool. Background Art

[0002] In the general trend of decarbonizing society, the electrification of motor vehicles and other means of transportation plays a major role. The motors used in electric vehicles need to be lighter and have higher performance. In order to achieve low iron loss and high magnetic flux density, the cores of motors and other devices are usually made by laminating multiple electrical steel sheets. In particular, amorphous alloy foils exhibit excellent mechanical properties, magnetic properties, corrosion resistance and other characteristics. Since their magnetic properties are particularly excellent, it is expected that the use of amorphous alloy foils instead of ordinary electrical steel sheets will significantly improve performance.

[0003] Electrical steel sheets used for cores of motors and the like are generally 100 to 500 μm thick, whereas amorphous metal foils are about 10 to 100 μm thick. Therefore, in the case of amorphous metal foils, stamping is required multiple times. When a metal foil having high hardness and high strength, such as an amorphous alloy foil, is repeatedly stamped into a specified shape, the stamping tool wears quickly, resulting in a short tool life.

[0004] JP 2021-130131 A (Patent Document 1) discloses a method for forming a plastic processing groove (the plastic processing groove becomes a stamping contour line with a predetermined shape) on the surface of an amorphous alloy strip, and punching along the plastic processing groove with a punch and a die to obtain an amorphous alloy part. By forming a plastic processing groove that becomes a stamping contour line with a predetermined shape on the surface of an alloy foil, the stamping load is reduced and the tool life is improved.

[0005] In addition, when stamping an amorphous alloy foil, from the perspective of ensuring productivity, multiple alloy foils can be laminated and stamped. However, as the number of laminated sheets increases, the stamping load increases and the quality of the stamping material deteriorates. JP 2023-8048 A (Patent Document 2) discloses a method for stamping an amorphous electrical steel sheet using a die and a punch, the method comprising applying an elastic coating to the amorphous electrical steel sheet, thereby reducing the stamping load. In this way, by using a laminated material coated with an elastic coating between alloy foils, the stamping load is suppressed and the wear of the tool is reduced.

[0006] There are also attempts to improve the shape of the punching tool. Japanese Patent No. 7129048 (Patent Document 3) discloses a shearing method for an amorphous alloy foil, wherein a punch for punching a plurality of laminated amorphous alloy foils is provided with a first edge formed on the punch tip surface and a second edge formed on the punch side surface, and the horizontal distance from the first edge to the punch side surface and the vertical distance from the second edge to the punch tip surface are set to a predetermined distance. When punching a plurality of laminated amorphous alloy foils, the tip of the punching tool is formed into a predetermined shape, so that a product with no cracks and high dimensional stability can be obtained.

[0007] Prior Art References

[0008] Patent Document 1: JP 2021-130131 A

[0009] Patent Document 2: JP 2023-8048 A

[0010] Patent document 3: JP 7129048 B Summary of the invention

[0011] Purpose of the Invention

[0012] However, in the manufacturing method of Patent Document 1, it is necessary to pre-form a plastic processing groove having a predetermined shape of a punching contour line, so a tool for special processing is required and the number of steps is increased. In addition, the punching method of Patent Document 2 requires a process for producing a laminated material with an elastic coating applied between alloy foils. In the shearing method of Patent Document 3, it is necessary to form the end of the punching tool into a predetermined shape, so the degree of freedom in processing is limited.

[0013] As described above, processing of amorphous alloy foil and the shape of punching tools have been studied, but no research has been conducted on cemented carbide suitable as a material for a tool for continuously punching high-hardness, high-strength metal foil (single layer or multiple laminated layers) into a predetermined shape.

[0014] Therefore, an object of the present invention is to provide a cemented carbide tool suitable for continuously punching a high-hardness, high-strength metal foil (single layer or multiple laminated layers) into a predetermined shape.

[0015] Means of solving the problem

[0016] The present invention relates to a cemented carbide which is most suitable for a punching tool for punching a high hardness, high strength metal foil (single layer or multiple laminated layers) such as an amorphous alloy foil. In order to solve the above problems, in the present invention, the wear and damage mode of the tool for punching the amorphous alloy foil is studied in depth, and improvements are attempted.

[0017] The most important point is that the hardness and wear resistance of cemented carbide used in the stamping tool for stamping amorphous alloy foil are not necessarily proportional. So far, the wear resistance of the stamping tool has been discussed in terms of the hardness of the tool material. In other words, in order to improve the wear resistance of the stamping tool, a cemented carbide with high hardness is selected, but this also reduces the toughness and thus the resistance to chipping. In the present invention, the focus is on the fact that the wear caused by the adhesion of the alloy foil to the stamping tool when stamping the amorphous alloy foil depends largely on the WC phase grain size of the cemented carbide of the stamping tool, and the stamping tool made of cemented carbide with finer WC phase grains tends to have better wear resistance.

[0018] When using lubricating oil to stamp a conventional metal foil (such as electrical steel sheet) with a thickness of about 250 μm, the amount of adhesion between the workpiece and the stamping tool is small. Therefore, the stress when pulling out the adhered material during stamping is also small, and because the larger WC particles have better binder phase support, when comparing cemented carbides with the same hardness but different WC particle sizes, the WC phase particles of the cemented carbide with a relatively large particle size will not fall off, resulting in excellent wear resistance.

[0019] On the other hand, when stamping a glued laminate of an amorphous alloy foil having a thickness of about 10 to 100 μm, lubricating oil cannot be used. In addition, when stamping an amorphous alloy foil without using lubricating oil, the amount of material of the workpiece adhering to the stamping tool increases. Because the amorphous alloy has high hardness and strength, the stress when peeling off the adhered material is very large. Therefore, even the WC phase with a large particle size and high binder phase support falls off due to the stress when peeling off the adhered material, and the stamping tool wears.

[0020] As a result of in-depth research in view of the above problems, the inventors have found that because cemented carbide with a smaller WC phase particle size has a smaller volume loss when WC particles fall off, the total volume loss (= wear amount) caused by repeated falling off is smaller. In other words, when stamping high hardness, high strength metal foil (single layer or multiple laminated layers), cemented carbide with a smaller WC particle size has a smaller wear resistance, even if the cemented carbide has the same hardness. Therefore, the inventors have found that, compared with conventional carbide stamping tools, by using ultrafine cemented carbide with a fine WC particle size (which has a higher hardness within the range where the stamping tool does not collapse under specific stamping conditions) for stamping tools, excellent wear resistance and crack resistance can be achieved at the same time.

[0021] That is, the cemented carbide tool for stamping according to one embodiment of the present invention comprises a WC phase and a binder phase containing Co; wherein the average grain size X μm of the WC phase and the total amount Y mass % of the binder phase satisfy the following formulas (1), (2) and (3):

[0022] X≤1.2 ... (1)

[0023] 2≤Y ... (2)

[0024] -6.7X+6≤Y≤-14X+38 ... (3);

[0025] And wherein the cemented carbide tool contains 2 to 20 mass % of Cr and / or V (calculated as carbides) relative to the total amount of the binder phase.

[0026] The total amount Y mass % of the binder phase preferably satisfies the following formula (4):

[0027] -7X+12≤Y ... (4),

[0028] And more preferably, the following equations (5) and (6) are satisfied:

[0029] X≤0.9 ... (5)

[0030] -11X+22≤Y ... (6).

[0031] In the cemented carbide tool according to one embodiment of the present invention, the total amount Y mass % of the binder phase preferably satisfies the following formulas (7) and (8):

[0032] X≤0.7 ... (7)

[0033] -6.7X+9.1≤Y ... (8).

[0034] In the cemented carbide tool according to one embodiment of the present invention, the cemented carbide tool preferably contains at least one element selected from the elements of Group 4 to Group 6 of the periodic table excluding Cr and V, and the total content of the at least one element is preferably 0.2 mass % to 5 mass % (calculated as carbides), and preferably contains a compound phase composed of carbides and / or carbonitrides of the above elements, and the particle size of the compound phase is 0.02 to 2 μm.

[0035] In the cemented carbide tool according to one embodiment of the present invention, the binder phase preferably contains at least one of Ni and Fe.

[0036] Such a cemented carbide tool is suitable for punching a metal foil having a thickness of 10 to 100 μm and a hardness of 700 HV or more, and the metal foil is preferably an amorphous alloy foil.

[0037] In a cemented carbide tool according to one embodiment of the present invention, after a laminate consisting of five amorphous alloy foil layers with a thickness of 25 μm and a hardness of 900 HV is subjected to a punching test more than 500 times with a gap of 5%t and without lubrication, the surface roughness Ra of the cutting edge of the cemented carbide tool is preferably less than 0.1 μm.

[0038] The cemented carbide tool according to one embodiment of the present invention is preferably coated with a hard coating layer.

[0039] Effects of the Invention

[0040] According to the present invention, a cemented carbide tool suitable for continuously punching a high-hardness, high-strength metal foil (a single layer or a plurality of laminated layers) into a predetermined shape can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram showing the measurement position of the line roughness Ra of the wear area. DETAILED DESCRIPTION

[0042] A cemented carbide tool for stamping according to one embodiment of the present invention comprises a WC phase and a binder phase containing Co; wherein the average grain size X μm of the WC phase and the total amount Y mass % of the binder phase satisfy the following formulas (1), (2) and (3):

[0043] X≤1.2 ... (1)

[0044] 2≤Y ... (2)

[0045] -6.7X+6≤Y≤-14X+38 ... (3);

[0046] And wherein the cemented carbide tool contains 2 to 20 mass % of Cr and / or V (calculated as carbides) relative to the total amount of the binder phase.

[0047] The average particle size X of the WC phase is less than 1.2 μm. Based on the structure of any cross section of the cemented carbide, the average particle size X of the WC phase is calculated by the Fullman formula. When the average particle size X of the WC phase exceeds 1.2 μm, wear may occur due to the shedding of the WC phase when punching a high hardness, high strength metal foil (single layer or multiple laminated layers), making it difficult to obtain sufficient wear resistance as a punching tool. The average particle size X of the hard phase is preferably less than 0.9 μm, more preferably less than 0.7 μm, further preferably less than 0.6 μm, and particularly preferably less than 0.4 μm.

[0048] The total amount Y (mass %) of the binder phase is 2 or more and satisfies the following formula (3):

[0049] -6.7X+6≤Y≤-14X+38 ... (3).

[0050] Herein, the total amount Y of binder phase represents the summation of the component added in the binder phase as a binder phase component, and the component solid-dissolved in the binder phase after adding as other components is not included in the total amount Y of binder phase.When the total amount Y (quality %) of binder phase is less than 2 or less than -6.7X+6, the toughness of cemented carbide is reduced, and the anti-cracking property of punching tool is reduced.When the total amount Y (quality %) of binder phase is greater than -14X+38, the hardness of cemented carbide is not enough, and the wear resistance of punching tool is reduced.The total amount Y (quality %) of binder phase is preferably more than -6.7X+9.1, more preferably more than -6.7X+9.6, even more preferably more than -6.7X+10.1, further preferably more than -7X+12, and particularly preferably -11X+22.

[0051] In addition to the main component Co, the binder phase preferably also contains at least one of Ni and Fe. Relative to the total amount of the binder phase, the content of at least one of Ni and Fe can be 30 mass %, and when it is 20 mass %, it can further bring advantages and not deteriorate properties. In addition, the binder phase can contain components that can be used as binder phase, such as Al and Cu. These components correspond to the above-mentioned components added as binder phase components. In addition, the metal elements constituting the hard phase can be dissolved in the binder phase of cemented carbide. When containing components other than Co as binder phase components as described above, relative to the total amount of the binder phase, the content of Co is preferably more than 70 mass %, and more preferably more than 80 mass %.

[0052] With respect to binder phase, cemented carbide of the present invention contains 2% to 20% by mass (calculated as carbide) of Cr and / or V. When adding 2% to 20% by mass of Cr (calculated as carbide), the grain growth of WC during sintering is suppressed and corrosion resistance is improved. When adding 2% to 20% by mass of V (calculated as carbide), a larger grain growth inhibition effect than Cr can be obtained. Calculated as carbide, the addition of Cr and / or V is preferably 3% to 18% by mass, and more preferably 4% to 15% by mass.

[0053] It may contain at least one element selected from the group consisting of elements of Groups 4 to 6 of the periodic table except Cr and V. The total content of the at least one element is preferably 0.2% to 5% by mass, calculated as carbide. The total content of the above elements is more preferably 0.5% to 4% by mass, and further preferably 1% to 3% by mass, calculated as carbide. These components may also be dissolved in the binder phase.

[0054] The cemented carbide of the present invention preferably contains a compound phase composed of carbides and / or carbonitrides of the above-mentioned elements, and the particle size of the compound phase is 0.02 to 2 μm. The compound phase can be composed of a variety of compounds existing alone, or can include a solid solution phase. Examples of solid solution phases include (Ta, Nb) C, (W, Ti) C, (W, Cr, Ti) C, (W, Ti) CN and (W, Ti, Nb) C. The particle size of the compound phase is more preferably 0.05 to 1 μm.

[0055] The cemented carbide tool according to one embodiment of the present invention emphasizes improvement in chipping resistance, and preferably satisfies the following formula (4):

[0056] -7X+12≤Y ... (4).

[0057] By reducing the WC phase grain size of cemented carbide and increasing the amount of a binder phase mainly composed of Co, a cemented carbide tool more suitable for punching metal foil can be obtained, which is less likely to crack at the cutting edge even when a high-hardness, high-strength metal foil (a single layer or multiple laminated layers) is continuously punched into a specified shape.

[0058] In order to further enhance chipping resistance and improve wear resistance relative to conventional products, it is more preferred that the cemented carbide tool according to one embodiment of the present invention satisfies the following formulas (5) and (6):

[0059] X≤0.9 ... (5)

[0060] -11X+22≤Y ... (6).

[0061] This cemented carbide tool is particularly suitable for punching a plurality of laminated metal foils having high hardness and strength, and is less likely to crack at the cutting edge even when the punching load increases, making it possible to suppress wear at the cutting edge of the punching tool. In other words, it is advantageous when punching under high load conditions or using a tool having a shape that is prone to cracking.

[0062] In addition, a cemented carbide tool according to another embodiment of the present invention emphasizes that wear resistance is improved while ensuring sufficient chipping resistance, and preferably satisfies the following formulas (7) and (8):

[0063] X≤0.7 ... (7)

[0064] -6.7X+9.1≤Y ... (8).

[0065] By reducing the WC phase grain size of cemented carbide to 0.7 μm, wear resistance can be further improved. The WC phase grain size is more preferably 0.6 μm or less, which provides more excellent wear resistance, and is further preferably 0.4 μm or less. In addition, the average grain size X μm of the WC phase and the total amount Y mass % of the binder phase more preferably satisfy the following relationship: -6.7X+9.6≤Y, because the cutting edge of the punching tool is less likely to break and stable processing can be performed, and -6.7X+10.1≤Y is further preferred.

[0066] The cemented carbide tool according to one embodiment of the present invention can be coated with a hard coating on its surface according to the application, which can extend the tool life. There is no particular limitation on the method of coating the hard coating, but known coating methods such as DLC, PVD and CVD can be used.

[0067] Furthermore, the surface of the cemented carbide tool according to one embodiment of the present invention may be processed by shot peening, laser shot peening, etc. to improve chipping resistance. Any commonly used method may be used for shot peening and laser shot peening.

[0068] An example of a method for manufacturing a cemented carbide tool of the present invention will be described below. However, the method for manufacturing a cemented carbide tool of the present invention is not limited to the following, and any common method for manufacturing a cemented carbide tool (such as a tool for stamping a metal foil) may be used. The raw material powder is wet mixed in a ball mill or the like, and then dried to prepare a molding powder, which is a raw material for cemented carbide. The molding powder is molded by a method such as mold molding or cold isostatic pressing (CIP). The obtained green body is sintered in a vacuum or inert atmosphere at a temperature equal to or higher than the liquid phase appearance temperature. The liquid phase appearance temperature of the green body is the temperature at which the liquid phase appears during the temperature rise process of sintering, and is measured using a differential thermal analyzer. The upper limit of the sintering temperature is preferably equal to or lower than the liquid phase appearance temperature + 100 ° C. The obtained sintered body may be further subjected to HIP treatment.

[0069] The cemented carbide tool of the present invention can be used to continuously stamp high-hardness, high-strength metal foil (such as amorphous alloy foil) into a predetermined shape. The cemented carbide tool of the present invention is effective for workpieces with a hardness of about HV200 or more, more effective for workpieces with a hardness of HV500 or more, and further effective for workpieces with a hardness of HV700 or more. There is no particular restriction on the thickness of the workpiece, and it can be applied to ordinary metal plates with a thickness of 100 to 500 μm, such as electrical steel plates, but is suitable for metal foils with a thickness of about 10 to 100 μm, and is particularly suitable for metal foils with a thickness of about 25 to 50 μm. Depending on the machinability of the workpiece, stamping can be performed in a single layer or multiple laminated layers, and the stamping method can be selected according to the most suitable method. It is particularly suitable for stamping amorphous alloy foils without using lubricating oil. In addition, even when stamping multiple layers of high-hardness, high-strength metal foils (such as amorphous alloy foils), the wear of the stamping tool can be suppressed. Therefore, even when a plurality of laminated amorphous alloy foils are punched out without using lubricating oil, the tool for punching out metal foils of the present invention can be appropriately used.

[0070] When the WC phase of the cemented carbide tool falls off from the wear surface, the falling portion becomes concave, and the sharp corners of the WC particles tend to protrude from the surrounding area, thereby increasing the roughness of the wear surface. As a result, the friction between the workpiece and the wear surface during punching also increases, making the wear surface more easily worn. In other words, it has been found that the wear surface of a cemented carbide tool with a small wear surface roughness has a small friction with the workpiece during punching, and is less prone to wear.

[0071] That is, after a laminate composed of five amorphous alloy foils having a thickness of 25 μm and a hardness of 900 HV is subjected to a punching test of 500 times or more with a gap of 5%t and without lubrication, the surface roughness Ra of the cutting edge is preferably 0.1 μm or less. Figure 1 The method for measuring the surface roughness Ra of the cutting edge is described. The surface roughness Ra of the cutting edge indicates that the wear area on the side around the cutting edge of the cemented carbide tool after the punch test is as follows: Figure 1 The wear area shown in (1) and the distance from the tool end face to the end of the wear area (the length perpendicular to the tool end face) is A (the cutoff λc is 8 μm and the rest conforms to JIS B 0601), the line roughness Ra at a position A / 2 from the tool end face in the direction perpendicular to the punching direction. When it is difficult to measure by avoiding adhesion of material, the value measured at a position within the range of A / 8 to A / 2 from the tool end face can be used as the surface roughness Ra of the cutting edge.

[0072] In addition, when the cutting edge is C-faced ( Figure 1 (2)) or R processing ( Figure 1 (3)) etc., the position of the wear area corresponding to the boundary between the processed part and the side part should be measured ( Figure 1 (2) and Figure 1 The line roughness Ra in the direction perpendicular to the punching direction (the position indicated by the arrow in (3)) is measured (the cutoff λc is 8 μm, and the rest conforms to JIS B 0601). When it is difficult to measure due to avoiding adhesion of materials, or when the cutting edge is processed but the boundary between the processed part and the side part is not clear, follow Figure 1 The measurement position for the tool in (1).

[0073] The method for measuring the line roughness Ra is preferably measured at three or more positions of a measuring length of 258 μm or more while avoiding any adhering material or after removing the adhering material, so that the total measuring length is 1,000 μm or more. In order to make it easier to measure while avoiding adhering material, it is preferred that the position of A / 2 is located at a position of 10 μm or more from the tool end face. After the punching test, the surface roughness Ra of the cutting edge is more preferably 0.06 μm or less, and further preferably 0.04 μm or less.

[0074] The tool for stamping metal foil of the present invention can show better wear resistance and chipping resistance when stamping with lubricating oil. It also shows excellent performance for laminated foils, such as those disclosed in Patent Document 2. It can show excellent performance not only for amorphous alloys but also for nanocrystalline alloys, and can show even better performance when stamping ordinary electrical steel sheets. It can also be applied to stamping foils and sheets for various applications, not limited to stamping motor cores.

[0075] In the following examples, performance evaluation was performed using a tool manufactured by a grinding process, and it was shown that the cemented carbide tool of the present invention exhibited excellent performance under various stamping conditions. Note that stamping tools with complex shapes can be manufactured by electrical discharge machining. In this case, for example, when the tool is made of cemented carbide, which is essential for improving chipping resistance, defects that occur during electrical discharge machining, which may cause chipping during stamping, can be minimized, and excellent tool performance is exhibited. Example

[0076] The present invention will be specifically described below by way of examples, but is not limited thereto.

[0077] Example 1

[0078] As raw material powders, WC powder (0.07-1.4 μm), Co powder (1.3 μm), Ni powder (2.5 μm), VC powder (2.2 μm), TaC powder (1.2 μm), Cr3C2 powder (2.3 μm), and Mo2C powder (3.4 μm) having different particle sizes were used, and they were wet mixed and dried to obtain a mixed powder as shown in Table 1. The mixed powder was press-molded, vacuum sintered at 1320 to 1400° C., and further HIP-treated to produce a sintered body (cemented carbide).

[0079] Table 1

[0080]

[0081] The WC phase grain size, the amount of the binder phase, the transverse rupture strength and the Vickers hardness of the cemented carbides of the invention products 1 to 15 and the comparative products 1 to 5 were measured by the following methods.

[0082] (WC phase particle size)

[0083] The average grain size X of the WC phase of the cemented carbides of the inventive products 1-15 and the comparative products 1-5 was calculated using the Fullman formula based on the structure of an arbitrary cross section of the cemented carbide.

[0084] (Amount of binder phase)

[0085] The amount Y of the binder phase in the cemented carbides of the Inventive Products 1 to 15 and the Comparative Products 1 to 5 was determined as a mass ratio of the composition.

[0086] (Transverse rupture strength)

[0087] The transverse rupture strength (MPa) of the cemented carbides of the invention products 1 to 15 and the comparative products 1 to 5 was determined by transverse rupture strength measurement (three-point bending test) according to the method of JIS B4104.

[0088] (Vickers hardness)

[0089] The Vickers hardness (HV) of the cemented carbides of the invention products 1 to 15 and the comparative products 1 to 5 was measured using a Vickers hardness tester HV30.

[0090] Table 2

[0091]

[0092] Using the cemented carbides of the inventive products 1 to 15 and the comparative products 1 to 4, stamping tools having a stamping shape of 5 mm square were produced by a grinding process. In addition, the corresponding molds were prepared from cemented carbide (WC-1.0%Cr3C2-15Co, WC phase grain size: 1.4μm). Using these stamping tools, a stamping test was performed on an amorphous alloy foil (thickness: 25μm). At this time, since the trend of tool life varies depending on the stamping conditions, the stamping test was performed under the following two conditions (Test A, Test B). Note that the stamping test was not performed on the comparative product 5 because there were pores due to the amount Y of the binder phase being as low as 1% by mass.

[0093] (1) Test A: A single layer of amorphous alloy foil (thickness: 25 μm, hardness: 900 HV) was punched with a gap of 10%t without lubrication.

[0094] (2) Test B: Five layers of the above-mentioned amorphous alloy foil (total thickness: 125 μm) were simply stacked and punched with a gap of 5%t without lubrication.

[0095] After the test, the cutting edge of each punching tool was observed and the wear resistance and chipping resistance were evaluated. For small wear, the wear resistance was evaluated as excellent, for a certain degree of wear but still usable, the wear resistance was evaluated as good, and for large wear, the wear resistance was evaluated as poor. For no chipping, the chipping resistance was evaluated as excellent, for small chipping, the chipping resistance was evaluated as good, and for larger chipping, the chipping resistance was evaluated as poor. The results are shown in Table 3.

[0096] Table 3

[0097]

[0098] Note: (1) Not evaluable.

[0099] (1) About Test A

[0100] Comparative products 1 and 2 have low wear resistance because the WC phase particle size is greater than 1.2 μm. Comparative product 3 has a WC phase particle size less than 1.2 μm, but the amount of the binder phase is 27% by mass, which is relatively high relative to the WC phase particle size, so the hardness is very low and the wear resistance is poor. Comparative product 4 has a WC phase particle size of 0.25 μm, but the amount of the binder phase is 39% by mass, which is relatively high relative to the WC phase particle size, so the hardness is very low and the wear resistance is poor. Inventive products 1 to 5 and 14 have high hardness, so slight cracking occurs, but this is not a problem for use. In addition, the WC phase particle size is less than 1.2 μm, and the hardness is high, so the wear resistance is excellent. Inventive products 6 to 9, 11 and 12 do not have too high hardness, so no cracking is observed, and because the WC phase particle size is less than 1.2 μm, they also have excellent wear resistance. Inventive products 10 and 13 have WC phase grain sizes of 1.0 μm and 0.90 μm, respectively, which are close to 1.2 μm, so their hardness is low, but they are usable. Inventive product 15 has a small WC phase grain size of 0.25 μm, but has a high binder phase amount of 34 mass %, so their hardness is low, so they are usable, but have a certain degree of wear.

[0101] (2) About Test B

[0102] Comparative product 1 has slight chipping due to its high hardness, but this is not a problem for use. In addition, the WC phase particle size is greater than 1.2μm, so the wear resistance is low. Comparative product 2 has no chipping, but has low wear resistance due to its WC phase particle size greater than 1.2μm and low hardness. Comparative product 3 has a WC phase particle size of less than 1.2μm, but has an amount of 27% by mass of the binder phase, which is relatively high relative to the WC phase particle size, so the hardness is very low and the wear resistance is poor. Comparative product 4 has a WC phase particle size of 0.25μm, but has an amount of 39% by mass of the binder phase, which is relatively high relative to the WC phase particle size, so the hardness is very low and the wear resistance is poor. Inventive products 1 to 4 and 14 have large chipping at the beginning of stamping due to their high hardness. In addition, they become unusable at an early stage, so quantitative comparison of the amount of wear is not feasible. Inventive products 5 and 6 have excellent wear resistance because the WC phase grain size is less than 1.2 μm, but large chipping occurs because the hardness is too high. Inventive products 7, 8, and 10 have high hardness, so slight chipping occurs, but this is not a problem for use. They also have a certain degree of wear, but can be used. Inventive product 9 has a small WC phase grain size of 0.24 μm, so they also have excellent wear resistance. They also have a certain degree of wear, but this is not a problem for use. Inventive products 11 to 13 and 15 have low hardness, so they have a certain degree of wear, but can be used.

[0103] Example 2

[0104] In the punching test B performed in Example 1, for the invention products 5, 7 and 9 and the comparative product 2, the surface roughness Ra of each worn portion of the cutting edge was measured after 500 shots and 1000 shots. The measurement position is the line roughness at the specified position, and while avoiding the adhering material or after removing the adhering material, the laser microscope OLS4100 (available from Olympus Corporation) was used to measure at four points with a measuring length of 258 μm, and the numerical value was calculated by setting the cutoff λc to 8 μm and the rest in accordance with JIS B 0601, and then the average value was taken. The results are shown in Table 4.

[0105] Table 4

[0106]

[0107] Inventive product 5 has excellent wear resistance because the surface roughness Ra of the cutting edge is less than 0.1 μm, and the hardness is high, HV1530. The surface roughness of the cutting edge of Inventive product 7 has some wear, but it is still usable. Inventive product 9 has excellent wear resistance because the surface roughness Ra of the cutting edge is very small. Comparative product 2 has poor wear resistance because the surface roughness Ra of the cutting edge exceeds 0.1 μm.

Claims

1. A cemented carbide tool for stamping, the cemented carbide tool comprising: WC phase and binder phase containing Co; The average particle size X μm of the WC phase and the total amount Y mass % of the binder phase satisfy the following formulas (1), (2) and (3): X≤1.2 ... (1) 2≤Y ... (2) -6.7X+6≤Y≤-14X+38 ... (3); And wherein the cemented carbide tool contains 2 to 20 mass % of Cr and / or V (calculated as carbides) relative to the total amount of the binder phase.

2. The cemented carbide tool according to claim 1, wherein: The total amount Y mass % of the binder phase satisfies the following formula (4): -7X+12≤Y ... (4).

3. The cemented carbide tool according to claim 2, wherein: The total amount Y mass % of the binder phase satisfies the following formulas (5) and (6): X≤0.9 ... (5) -11X+22≤Y ... (6).

4. The cemented carbide tool according to claim 1, wherein: The total amount Y mass % of the binder phase satisfies the following formulas (7) and (8): X≤0.7 ... (7) -6.7X+9.1≤Y ... (8).

5. The cemented carbide tool according to any one of claims 1 to 4, comprising at least one element selected from the group consisting of elements of Group 4 to Group 6 of the periodic table excluding Cr and V, wherein the total content of the at least one element is 0.2 mass % to 5 mass % (calculated as carbide). 6 . The cemented carbide tool according to claim 1 , wherein the binder phase contains at least one of Ni and Fe. 7 . The cemented carbide tool according to claim 1 , which is used for punching a metal foil having a thickness of 10 to 100 μm and a hardness of 700 HV or more.

8. The cemented carbide tool according to claim 7, wherein the metal foil is an amorphous alloy foil.

9. The cemented carbide tool according to any one of claims 1 to 8, wherein the surface roughness Ra of the cutting edge of the cemented carbide tool is 0.1 μm or less after a laminate consisting of five amorphous alloy foil layers having a thickness of 25 μm and a hardness of 900 HV is subjected to a punching test of 500 times or more with a gap of 5%t and without lubrication.

10. The cemented carbide tool according to any one of claims 1 to 9, which is coated with a hard coating.

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