Cemented carbide, blank for cutting tool, cutting tool, and method for manufacturing machined product

Abstract

Provided is a cemented carbide that can improve the wear resistance and chipping resistance of cutting tools. [Solution] The cemented carbide comprises a plurality of hard particles containing W and C and a plurality of bonding particles containing at least one of Co, Ni, and Fe, and in a cross section measuring 10 μm x 10 μm, the ratio of the cross-sectional area of ​​the plurality of bonding particles to the sum of the cross-sectional areas of the plurality of hard particles and the plurality of bonding particles is 10% or more, and the maximum value of the circle-equivalent diameter of the plurality of bonding particles is 0.2 μm or less.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to methods of manufacturing cemented carbide, cutting tool blanks, cutting tools, and machined workpieces. [Background technology]

[0002] A rotary tool for machining printed circuit boards is known, which has a cutting edge made of cemented carbide. The cemented carbide may have a first phase made of tungsten carbide particles and a second phase containing cobalt.

[0003] For example, a cemented carbide alloy is known in which the average equivalent circle diameter of the tungsten carbide particles is 0.5 μm or more and 1.2 μm or less, the tungsten carbide particles contain 13% or less by number of first tungsten carbide particles having an equivalent circle diameter of 0.3 μm or less, and the tungsten carbide particles contain 12% or less by number of second tungsten carbide particles having an equivalent circle diameter of more than 1.3 μm, and in a histogram showing the distribution of the equivalent circle diameters of the tungsten carbide particles, the ratio of the maximum frequency to the minimum frequency is 7.0 or less in the range of the equivalent circle diameters of the tungsten carbide particles from more than 0.3 μm to 1.3 μm, and the cobalt content of the cemented carbide alloy is more than 0% by mass and 10% by mass or less (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2023 / 062818 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, in order to improve the efficiency of cutting processing using a cutting tool, it is required to improve the wear resistance and fracture resistance of the cutting tool. Thus, the conventional techniques have room for further improvement in terms of improving the wear resistance and fracture resistance of the cutting tool.

[0006] An object of one aspect of the embodiment is to provide a cemented carbide capable of improving the wear resistance and chipping resistance of a cutting tool. [Means for solving the problem]

[0007] A cemented carbide according to one embodiment comprises a plurality of hard particles containing W and C and a plurality of bonding particles containing at least one of Co, Ni, and Fe, and in a cross section measuring 10 μm x 10 μm, the ratio of the cross-sectional area of ​​the plurality of bonding particles to the sum of the cross-sectional areas of the plurality of hard particles and the plurality of bonding particles is 10% or more, and the maximum value of the circle-equivalent diameter of the plurality of bonding particles is 0.2 μm or less. [Effects of the Invention]

[0008] According to one aspect of the embodiment, it is possible to provide a cemented carbide that can improve the wear resistance and chipping resistance of a cutting tool. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1A is a diagram schematically illustrating an example of the configuration of a PWB drill according to an embodiment. [Figure 1B] FIG. 1B is a diagram schematically illustrating an example of a tip portion of a PWB drill according to an embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating an example of the configuration of a blank for a PWB drill according to the embodiment. [Figure 3] FIG. 3 is a diagram schematically showing an example of a cross section of a cemented carbide according to an embodiment. [Figure 4A] FIG. 4A is a diagram schematically illustrating an example of a method for manufacturing a machined product according to an embodiment. [Figure 4B] FIG. 4B is a diagram schematically illustrating an example of a method for manufacturing a machined product according to the embodiment. [Figure 4C] FIG. 4C is a diagram schematically illustrating an example of a method for manufacturing a machined product according to an embodiment. [Figure 5] FIG. 5 is a photograph showing a cross section of the cemented carbide according to the example. [Figure 6] FIG. 6 is a photograph showing a cross section of the cemented carbide according to Comparative Example 1. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, modes for carrying out the methods for manufacturing cemented carbide, cutting tool blanks, cutting tools, and machined products according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. The methods for manufacturing cemented carbide, cutting tool blanks, cutting tools, and machined products according to the present disclosure are not limited to the embodiments described below. In the following embodiments, the same components are designated by the same reference numerals, and redundant explanations will be omitted.

[0011] <Cutting tools> First, a rotary tool for machining printed circuit boards will be described as an example of a cutting tool according to an embodiment. The workpiece to be machined by the rotary tool for machining printed circuit boards is a printed circuit board such as a printed circuit board (PCB) or a printed wiring board (PWB). An example of such a rotary tool for machining printed circuit boards is a very small diameter drill for drilling holes in printed wiring boards. Hereinafter, the very small diameter drill for drilling holes in printed wiring boards will be referred to as a PWB drill.

[0012] 1A and 1B, an example of a PWB drill according to an embodiment will be described. Fig. 1A is a diagram schematically illustrating an example of the configuration of a PWB drill according to an embodiment. Fig. 1B is a diagram schematically illustrating an example of a tip portion of a PWB drill according to an embodiment.

[0013] As shown in FIG. 1A, the PWB drill 1 has a cutting part 2, a shank part 3, and a connecting part 4.

[0014] The cutting portion 2 is a long, cylindrical member. As shown in Fig. 1B, a cutting edge 2b is provided at the tip of the cutting portion 2. Also, as shown in Figs. 1A and 1B, one or more spiral chip discharge grooves 2a are formed on the side surface of the cutting portion 2, extending from the tip to the base end.

[0015] The cutting edge 2 is made of a cemented carbide alloy including a hard phase containing W (tungsten) and C (carbon) and a binder phase containing an iron-group metal (at least one of Co (cobalt), Ni (nickel), and Fe (iron)). The hard layer is made of a plurality of hard particles containing W and C. The binder phase is made of a plurality of binder particles containing an iron-group metal. The binder phase bonds the plurality of hard particles together.

[0016] The shank portion 3 is a cylindrical member with an outer diameter larger than that of the cutting portion 2. The shank portion 3 is made of, for example, stainless steel, which reduces the manufacturing cost of the PWB drill 1 compared to when the entire PWB drill 1 is made of cemented carbide.

[0017] The connecting portion 4 connects the cutting portion 2 and the shank portion 3, which have different outer diameters, and has a first tapered portion 4a, a second tapered portion 4b, and a cylindrical portion 4c.

[0018] The first tapered portion 4a has an outer diameter that gradually decreases toward the tip. The first tapered portion 4a is integrally formed with the shank portion 3. That is, the first tapered portion 4a is formed of the same material as the shank portion 3, such as stainless steel.

[0019] The second tapered portion 4b has an outer shape that gradually increases toward the base end. The second tapered portion 4b is integrally formed with the cutting portion 2. That is, the second tapered portion 4b is formed of the same material as the cutting portion 2, such as cemented carbide.

[0020] The cylindrical portion 4c has a portion formed integrally with the first tapered portion 4a at the base end and a portion formed integrally with the second tapered portion 4b at the tip end. The portion formed integrally with the first tapered portion 4a is made of the same material as the first tapered portion 4a, such as stainless steel. The portion formed integrally with the second tapered portion 4b is made of the same material as the second tapered portion 4b, such as cemented carbide.

[0021] The portion integrally formed with the first tapered portion 4a and the portion integrally formed with the second tapered portion 4b are joined at a joining surface 4d located within the cylindrical portion 4c. That is, the stainless steel or the like forming the portion integrally formed with the first tapered portion 4a and the cemented carbide forming the portion integrally formed with the second tapered portion 4b are joined at the joining surface 4d. In this way, the cutting portion 2 and the shank portion 3 are connected by the cylindrical portion 4c.

[0022] The cutting tool according to the embodiment is not limited to a rotary tool for machining a printed circuit board, such as the PWB drill 1 shown in Fig. 1. The cutting tool according to the embodiment is not particularly limited as long as it includes at least a cutting edge including a cemented carbide. For example, the cutting tool according to the embodiment may include an insert having a cutting edge including a cemented carbide and a holder for fixing the insert.

[0023] <Cutting tool blanks> Next, a blank for manufacturing a rotary tool for processing a printed circuit board will be described as an example of a cutting tool blank according to the embodiment. An example of a blank for manufacturing a rotary tool for processing a printed circuit board is a PWB drill blank for manufacturing a PWB drill 1 as shown in Figures 1A and 1B.

[0024] Here, an example of a blank for a PWB drill according to an embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram schematically showing an example of the configuration of a blank for a PWB drill according to an embodiment.

[0025] 2, the PWB drill blank 5 is a long, cylindrical member. The length of the PWB drill blank 5 in the longitudinal direction is equal to or greater than the sum of the length of the cutting edge 2 in the longitudinal direction of the PWB drill 1 shown in FIGS. 1A and 1B, the length of the second tapered portion 4b, and the length of the portion of the cylindrical portion 4c that is integrally formed with the second tapered portion 4b.

[0026] The cross section of the PWB drill blank 5 at one end thereof corresponds to the joining surface 4d of the cylindrical portion 4c of the PWB drill 1. The PWB drill blank 5 is joined at the joining surface 4d by a laser or the like to the shank portion 3, the first tapered portion 4a, and a portion of the cylindrical portion 4c that is integral with the first tapered portion 4a. The PWB drill blank 5 is then sharpened by mechanical grinding, polishing, or the like to form the cutting portion 2 of the PWB drill 1, the second tapered portion 4b, and a portion of the cylindrical portion 4c that is integral with the second tapered portion 4b.

[0027] The blank 5 for the PWB drill is formed from the same material, such as cemented carbide, as the material forming the cutting portion 2 of the PWB drill 1, the second tapered portion 4b, and the portion of the cylindrical portion 4c that is integrally formed with the second tapered portion 4b.

[0028] In the PWB drill blank 5, a coating film may be formed on the surface of a substrate made of cemented carbide. Examples of such a coating film include coating films made of titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), titanium-aluminum composite nitride (TiAlN), aluminum oxide (Al2O3), etc.

[0029] The cutting tool blank according to the embodiment is not limited to a blank for manufacturing a rotary tool for processing printed circuit boards, such as the PWB drill blank 5 shown in Fig. 2. The cutting tool blank according to the embodiment is not particularly limited as long as it contains at least a cemented carbide. The cutting tool blank according to the embodiment may be, for example, a blank for manufacturing an insert having a cutting edge containing a cemented carbide.

[0030] <Cemented carbide> Next, an example of a cemented carbide according to an embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram schematically showing an example of a cross section of a cemented carbide according to an embodiment.

[0031] As shown in FIG. 3, for the cemented carbide 10 according to the embodiment, a photograph of the cross section of the cemented carbide 10 is obtained. For example, a scanning electron microscope or the like is used to observe the surface of the cemented carbide 10, thereby obtaining a photograph of the cross section of the cemented carbide 10. The cross section of the cemented carbide 10 has a size that allows an appropriate maximum value of the circle-equivalent diameter of the plurality of bonding particles 30 to be obtained. For example, the cross section of the cemented carbide 10 has a size of 10 μm × 10 μm.

[0032] As shown in FIG. 3 , the cemented carbide 10 according to the embodiment includes a plurality of hard particles 20 and a plurality of bonding particles 30. The plurality of hard particles 20 contain tungsten (W) and carbon (C). The plurality of hard particles 20 may be tungsten carbide (WC) particles. As shown in FIG. 3 , the plurality of hard particles 20 have various cross-sectional areas in a cross section of the cemented carbide 10. The plurality of bonding particles 30 bond the plurality of hard particles 20 together. The plurality of bonding particles 30 contain at least one iron group element, such as cobalt (Co), nickel (Ni), and iron (Fe). As shown in FIG. 3 , the plurality of bonding particles 30 have various cross-sectional areas in a cross section of the cemented carbide 10.

[0033] For the cemented carbide 10 according to the embodiment, the cross-sectional areas of the plurality of hard particles 20, the cross-sectional areas of the plurality of bonding particles 30, the circle-equivalent diameters of the plurality of hard particles 20, and the circle-equivalent diameters of the plurality of bonding particles 30 in the cross section of the cemented carbide 10 are obtained. The circle-equivalent diameter of each hard particle 20 means the diameter (μm) of a circle having the same area as the cross-sectional area of ​​the hard particle 20 in the cross section of the cemented carbide 10. The circle-equivalent diameter of each bonding particle 30 means the diameter (μm) of a circle having the same area as the cross-sectional area of ​​the bonding particle 30 in the cross section of the cemented carbide 10.

[0034] By analyzing the images of the hard particles 20 and the bonding particles 30 in the cross-sectional photograph of the cemented carbide 10 using image processing software such as "ImageJ" (manufactured by Wayne Rasband National Institutes of Health), the cross-sectional area of ​​each hard particle 20, the cross-sectional area of ​​each bonding particle 30, the circle-equivalent diameter of each hard particle 20, and the circle-equivalent diameter of each bonding particle 30 are calculated.

[0035] In the cemented carbide 10 according to the embodiment, the ratio of the cross-sectional area of ​​the plurality of bonding particles 30 to the sum of the cross-sectional areas of the plurality of hard particles 20 and the plurality of bonding particles 30 is 10% or more. In this case, it is possible to increase the proportion of the plurality of bonding particles 30 in the cemented carbide 10. Accordingly, it is possible to improve the fracture resistance of a cutting tool including a cutting edge 2b including the cemented carbide 10.

[0036] Furthermore, in the cemented carbide 10 according to the embodiment, the maximum circle-equivalent diameter of the plurality of bonding particles 30 is 0.2 μm or less. In this case, it is possible to reduce uneven distribution of the plurality of bonding particles 30 in the cemented carbide 10. Accordingly, it is possible to reduce the occurrence of abnormal wear such as chipping caused by uneven distribution of the plurality of bonding particles 30 in the cemented carbide 10. As a result, it is possible to improve the wear resistance of a cutting tool including a cutting edge 2b including the cemented carbide 10.

[0037] It is generally known that there is a trade-off between the wear resistance and fracture resistance of a cutting tool made of a cemented carbide and the ratio of the content of a plurality of hard particles to a plurality of bonding particles in the cemented carbide. For example, increasing the content of a plurality of hard particles (decreasing the content of a plurality of bonding particles) improves the wear resistance of the cutting tool but decreases the fracture resistance of the cutting tool. Conversely, increasing the content of a plurality of bonding particles (decreasing the content of a plurality of hard particles) improves the fracture resistance of the cutting tool but decreases the wear resistance of the cutting tool.

[0038] As described above, in the cemented carbide 10 according to the embodiment, the ratio of the cross-sectional area of ​​the bonding particles 30 to the sum of the cross-sectional areas of the hard particles 20 and the bonding particles 30 is 10% or more, and the maximum circle-equivalent diameter of the bonding particles 30 is 0.2 μm or less. In this case, it is possible to improve both the wear resistance and chipping resistance of a cutting tool including a cutting edge 2b containing the cemented carbide 10.

[0039] In the cemented carbide 10 according to the embodiment, the average value of the circle-equivalent diameter of the plurality of hard particles 20 may be larger than the median value of the circle-equivalent diameter of the plurality of bonding particles 30. In this case, it becomes possible to increase the proportion of the plurality of hard particles 20 in the cemented carbide 10. Accordingly, it becomes possible to improve the wear resistance of the cutting tool.

[0040] In the cemented carbide 10 according to the embodiment, the average value of the circle-equivalent diameter of the plurality of hard particles 20 may be larger than the maximum value of the circle-equivalent diameter of the plurality of bonding particles 30. In this case, it becomes possible to increase the proportion of the plurality of hard particles 20 in the cemented carbide 10. Accordingly, it becomes possible to improve the wear resistance of the cutting tool.

[0041] In the cemented carbide 10 according to the embodiment, the maximum circle-equivalent diameter of the plurality of bonding particles 30 may be 0.1 μm or more. In this case, it becomes possible to increase the proportion of the plurality of bonding particles 30 in the cemented carbide 10. Accordingly, it becomes possible to improve the chipping resistance of the cutting tool.

[0042] In the cemented carbide 10 according to the embodiment, the ratio of the cross-sectional area of ​​the plurality of bonding particles 30 to the sum of the cross-sectional areas of the plurality of hard particles 20 and the plurality of bonding particles 30 may be 30% or less. In this case, it becomes possible to increase the proportion of the plurality of bonding particles 30 in the cemented carbide 10. Accordingly, it becomes possible to improve the chipping resistance of the cutting tool.

[0043] In the cemented carbide 10 according to the embodiment, the standard deviation of the indentation hardness measured on a cross section having a size of 200 μm × 200 μm may be 1 GPa or less. The indentation hardness of the cross section of the cemented carbide 10 having a size of 200 μm × 200 μm is measured, for example, using a nanoindenter. The indentation hardness of the cross section of the cemented carbide 10 is measured, for example, at 100 or more points on the cross section of the cemented carbide 10 in three or more fields of view. The standard deviation of the indentation hardness is calculated based on the indentation hardness values ​​measured at multiple points in this manner.

[0044] In this case, it is possible to improve the uniformity of the indentation hardness of the cemented carbide 10. The improvement in the uniformity of the indentation hardness of the cemented carbide 10 is related to the reduction in uneven distribution of the plurality of bonding particles 30 in the cemented carbide 10. Therefore, it is possible to reduce the uneven distribution of the plurality of bonding particles 30 in the cemented carbide 10. Accordingly, it is possible to reduce the occurrence of abnormal wear such as chipping caused by the uneven distribution of the plurality of bonding particles 30 in the cemented carbide 10. As a result, it is possible to improve the wear resistance of the cutting tool.

[0045] <Method of manufacturing cemented carbide> Next, an example of a method for manufacturing the cemented carbide 10 according to the embodiment will be described. The method for manufacturing the cemented carbide 10 according to the embodiment is not limited to the following manufacturing method.

[0046] First, various powders are blended together to make a total of 100 mass% containing 75 to 98.9 mass% tungsten carbide (WC) powder with an average particle size of 0.1 to 1 μm, 1 to 20 mass% cobalt powder, 0.1 to 5 mass% carbide powder of at least one element selected from Groups 4, 5, and 6 of the periodic table, and other unavoidable impurities. Furthermore, metallic tungsten (W) powder or carbon black (C) may be blended if desired.

[0047] Next, water or an organic solvent and, if desired, an organic binder are added to the prepared mixed powder and mixed, and the mixture is pulverized and mixed using a known method such as a ball mill or a vibration mill, and then dried in a spray dryer to form granules.

[0048] Next, this granular mixed powder is molded into a predetermined cutting tool shape as shown in FIGS. 1A and 1B by a known molding method such as press molding, casting, extrusion molding, or cold isostatic pressing.

[0049] Next, this compact is fired in a firing furnace in a vacuum or in a non-oxidizing atmosphere such as Ar or N2 at a firing temperature of 1350 to 1450°C for 0.5 to 5 hours, and then hot isostatic pressing (HIP) sintering is performed at a temperature 5 to 50°C lower than the firing temperature, at a pressure of 5 to 20 MPa, and for 0.5 to 3 hours to produce a cemented carbide for cutting tools.

[0050] In addition, while the maximum firing temperature itself is kept the same for all materials, the crystalline state within the cemented carbide is controlled by varying the rate of temperature rise just before the firing temperature reaches the maximum temperature.

[0051] If desired, the produced cemented carbide may be used as a substrate for a cutting tool, and a coating film may be formed on the surface of the substrate, such as titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), titanium-aluminum nitride (TiAlN), or aluminum oxide (Al2O3).

[0052] The coating film can be formed by known film-forming methods such as chemical vapor deposition (thermal CVD, plasma CVD, organic CVD, catalytic CVD, etc.) and physical vapor deposition (ion plating, sputtering, etc.).

[0053] <Method of manufacturing machined products> Next, as an example of a method for manufacturing a machined product according to an embodiment, a method for manufacturing a machined product using a rotary tool for machining a printed circuit board will be described. An example of the rotary tool for machining a printed circuit board is a PWB drill 1 as shown in FIGS. 1A and 1B.

[0054] Here, an example of a method for manufacturing a machined product according to an embodiment will be described with reference to Figures 4A, 4B, and 4C. Figures 4A, 4B, and 4C are diagrams that schematically show an example of a method for manufacturing a machined product according to an embodiment.

[0055] The machined product is produced by cutting a workpiece 100. In Fig. 4A, Fig. 4B, and Fig. 4C, drilling performed using a drilling machine is illustrated as an example of cutting. The manufacturing method of the machined product in the embodiment includes the following steps: (1) a step of rotating a PWB drill 1; (2) contacting the workpiece 100 with the PWB drill 1; (3) a step of relatively separating the PWB drill 1 from the workpiece 100; It is equipped with:

[0056] More specifically, first, as shown in Fig. 4A, the PWB drill 1 is rotated around the axis CR and brought relatively close to the workpiece 100. Next, as shown in Fig. 4B, the cutting edge 2b of the PWB drill 1 is brought into contact with the workpiece 100 to drill a hole in the workpiece 100. Then, as shown in Fig. 4C, the PWB drill 1 is moved relatively away from the workpiece 100.

[0057] In Fig. 4A, the workpiece 100 is fixed and the PWB drill 1 is moved downward while being rotated, thereby bringing the PWB drill 1 closer to the workpiece 100. In Fig. 4B, the cutting edge 2b of the PWB drill 1 is brought into contact with the fixed workpiece 100 to drill a hole in the workpiece 100. In Fig. 4C, the PWB drill 1 is moved upward while the workpiece 100 is fixed, thereby moving the PWB drill 1 away from the workpiece 100.

[0058] In the cutting process in the manufacturing method of the embodiment, the PWB drill 1 is moved in each step to bring the PWB drill 1 into contact with the workpiece 100 or to move the PWB drill 1 away from the workpiece 100, but of course this is not limited to this form.

[0059] For example, in step (1), the workpiece 100 may be brought closer to the PWB drill 1. Similarly, in step (3), the workpiece 100 may be moved away from the PWB drill 1. To continue the cutting process, for example, the PWB drill 1 may be kept rotating, and the step of bringing the cutting edge 2b of the PWB drill 1 into contact with different locations on the workpiece 100 may be repeated.

[0060] Representative examples of the workpiece 100 include printed circuit boards such as printed circuit boards (PCB) and printed wiring boards (PWB). [Example]

[0061] Examples of the present disclosure will be specifically described below, but the present disclosure is not limited to the examples shown below.

[0062] (Example) First, 95% by mass of tungsten carbide (WC) powder with an average particle size of 0.2 μm and 5% by mass of cobalt powder were mixed to obtain a mixed powder. Next, isopropyl alcohol (IPA) was added to the mixed powder and pulverized using a vibration mill. The mixed powder was then dried using a spray dryer to obtain a granular mixed powder. The granular mixed powder was then pressed into the shape of the PWB drill 1 shown in FIG. 1A. Next, this compact was sintered in a sintering furnace under vacuum at a sintering temperature of 1450°C for 1 hour. Subsequently, HIP sintering was performed at a temperature 10°C lower than the sintering temperature and a pressure of 10 MPa for 1 hour to produce a cemented carbide according to the example. The crystalline state of the cemented carbide was controlled by adjusting the heating rate just before the sintering temperature reached its maximum temperature.

[0063] Next, a predetermined surface of the obtained cemented carbide was polished, and the polished surface was photographed using a field emission scanning electron microscope (FE-SEM) manufactured by JEOL under the following conditions: magnification: 2000x, acceleration voltage: 10 (kV), brightness: 581, contrast: 4630.

[0064] Fig. 5 is a photograph showing a cross section of the cemented carbide according to the example. As shown in Fig. 5, no uneven distribution of cobalt constituting the binding particles was observed in the cross section of the cemented carbide according to the example.

[0065] Next, the photographs were analyzed using image processing software "ImageJ" (Wayne Rasband National Institutes of Health). The cross-sectional areas of the hard particles, the bonded particles, the equivalent circle diameters of the hard particles, and the equivalent circle diameters of the bonded particles were calculated for each area of ​​10 μm × 10 μm in the image.

[0066] The ratio of the cross-sectional area of ​​the multiple bonded particles to the sum of the cross-sectional areas of the multiple hard particles and the multiple bonded particles was 24%, and the maximum circle-equivalent diameter of the multiple bonded particles was 0.16 μm.

[0067] The average equivalent circle diameter of the plurality of hard particles was 0.28 μm. The median equivalent circle diameter of the plurality of hard particles was 0.25 μm. The average equivalent circle diameter of the plurality of bonded particles was 0.05 μm. The median equivalent circle diameter of the plurality of bonded particles was 0.05 μm.

[0068] Next, the indentation hardness of the obtained cemented carbide was measured in a region measuring 200 μm × 200 μm. Specifically, the indentation hardness was measured at a total of 100 locations spaced approximately 2 μm apart vertically and horizontally using a nanoindenter. The standard deviation of the measured indentation hardness was 0.84 GPa.

[0069] Using the PWB drill made of the obtained cemented carbide, holes were drilled into printed wiring boards under the drilling conditions shown below. Drilling conditions Rotation speed: 240,000 / min Feed: 3.3 μm / rev Drill size: φ0.2 x 3mm Board: MCL-E-705G (manufactured by RESONAC)

[0070] The wear amount of the PWB drill bit when drilling 4,000 holes in the printed wiring board was 21.1 μm. The wear amount of the PWB drill bit when drilling 8,000 holes in the printed wiring board was 24.7 μm. The wear amount of the PWB drill bit when drilling 12,000 holes in the printed wiring board was 25.3 μm. The wear amount of the PWB drill bit when drilling 16,000 holes in the printed wiring board was 26 μm.

[0071] The degree of deviation in hole position when drilling holes in a printed wiring board using a PWB drill made of the obtained cemented carbide was evaluated using the process capability index Cpk. The distance between the drilled hole and the target position at the center was measured and used as hole position accuracy data. The average value and standard deviation of the measured hole position accuracy data were then calculated. Finally, using the calculated average value and standard deviation, Cpk = (specification value - mean value) / (3 x standard deviation) The process capability index Cpk was calculated according to the formula below. Here, the standard value was set to ±50 μm. The process capability index Cpk was 1.55.

[0072] (Comparative Example 1) A predetermined surface of the cemented carbide of the conventional PWB drill was polished, and the polished surface was photographed under the same conditions as those in Example 1 using a field emission scanning electron microscope (FE-SEM) manufactured by JEOL.

[0073] Fig. 6 is a photograph of a cross section of the cemented carbide according to Comparative Example 1. As shown in Fig. 6, uneven distribution of cobalt constituting the binding particles was observed in the cross section of the cemented carbide according to Comparative Example 1.

[0074] Next, the captured photographic image was analyzed in the same manner as in Example 1. Here, the cross-sectional areas of the plurality of hard particles, the cross-sectional areas of the plurality of bonded particles, the circle-equivalent diameters of the plurality of hard particles, and the circle-equivalent diameters of the plurality of bonded particles contained in an area having a size of 10 μm × 10 μm in the image were calculated.

[0075] The ratio of the cross-sectional area of ​​the multiple bonded particles to the sum of the cross-sectional areas of the multiple hard particles and the multiple bonded particles was 24%, and the maximum circle-equivalent diameter of the multiple bonded particles was 0.23 μm.

[0076] The average equivalent circle diameter of the plurality of hard particles was 0.27 μm. The median equivalent circle diameter of the plurality of hard particles was 0.24 μm. The average equivalent circle diameter of the plurality of bonded particles was 0.05 μm. The median equivalent circle diameter of the plurality of bonded particles was 0.05 μm.

[0077] Next, the indentation hardness of a region having a size of 200 μm×200 μm in the conventional cemented carbide was measured under the same conditions as those in Example 1. The standard deviation of the measured indentation hardness was 1.1 GPa.

[0078] Using a conventional PWB drill, drilling was performed on a printed wiring board under the same conditions as in Example 1.

[0079] The wear amount of the PWB drill bit when drilling 4,000 holes in the printed wiring board was 23.8 μm. The wear amount of the PWB drill bit when drilling 8,000 holes in the printed wiring board was 28.4 μm. The wear amount of the PWB drill bit when drilling 12,000 holes in the printed wiring board was 29.3 μm. The wear amount of the PWB drill bit when drilling 16,000 holes in the printed wiring board was 29.6 μm.

[0080] When drilling holes in a printed wiring board using a conventional PWB drill, the process capability index Cpk was 1.26.

[0081] (Comparative Example 2) A predetermined surface of the cemented carbide of a commercially available PWB drill was polished, and the polished surface was photographed under the same conditions as in Example 1 using a field emission scanning electron microscope (FE-SEM) manufactured by JEOL.

[0082] Next, the captured photographic image was analyzed in the same manner as in Example 1. Here, the cross-sectional areas of the plurality of hard particles, the cross-sectional areas of the plurality of bonded particles, the circle-equivalent diameters of the plurality of hard particles, and the circle-equivalent diameters of the plurality of bonded particles contained in an area having a size of 10 μm × 10 μm in the image were calculated.

[0083] The ratio of the cross-sectional area of ​​the multiple bonded particles to the sum of the cross-sectional areas of the multiple hard particles and the multiple bonded particles was 23%, and the maximum circle-equivalent diameter of the multiple bonded particles was 0.21 μm.

[0084] The average equivalent circle diameter of the plurality of hard particles was 0.29 μm. The median equivalent circle diameter of the plurality of hard particles was 0.26 μm. The average equivalent circle diameter of the plurality of bonded particles was 0.06 μm. The median equivalent circle diameter of the plurality of bonded particles was 0.05 μm.

[0085] Next, the indentation hardness of a region having a size of 200 μm × 200 μm in the commercially available cemented carbide was measured under the same conditions as those in Example 1. The standard deviation of the measured indentation hardness was 1.02 GPa.

[0086] Using a commercially available PWB drill, drilling was performed on the printed wiring board under the same conditions as in Example 1.

[0087] The wear amount of the PWB drill bit when drilling 4,000 holes in the printed wiring board was 20.2 μm. The wear amount of the PWB drill bit when drilling 8,000 holes in the printed wiring board was 25.4 μm. The wear amount of the PWB drill bit when drilling 12,000 holes in the printed wiring board was 26.4 μm. The wear amount of the PWB drill bit when drilling 16,000 holes in the printed wiring board was 27.3 μm.

[0088] The process capability index Cpk was 1.53 when drilling holes in a printed wiring board using a commercially available PWB drill.

[0089] The present technology can be configured as follows: (1) a plurality of hard particles containing W and C; a plurality of bonding particles containing at least one of Co, Ni, and Fe; Equipped with In a cross section having a size of 10 μm×10 μm, a ratio of a cross-sectional area of ​​the plurality of bonded particles to a sum of a cross-sectional area of ​​the plurality of hard particles and a cross-sectional area of ​​the plurality of bonded particles is 10% or more; The maximum equivalent circle diameter of the plurality of combined particles is 0.2 μm or less. Cemented carbide. (2) the average value of the equivalent circle diameters of the plurality of hard particles is larger than the median value of the equivalent circle diameters of the plurality of bonded particles; (1) The cemented carbide according to (1). (3) the average value of the equivalent circle diameters of the plurality of hard particles is larger than the maximum value of the equivalent circle diameters of the plurality of bonded particles; (2) The cemented carbide according to (1). (4) The maximum equivalent circle diameter of the plurality of combined particles is 0.1 μm or more. The cemented carbide according to any one of (1) to (3). (5) a ratio of a cross-sectional area of ​​the plurality of bonding particles to a sum of a cross-sectional area of ​​the plurality of hard particles and a cross-sectional area of ​​the plurality of bonding particles is 30% or less; The cemented carbide according to any one of (1) to (4). (6) The standard deviation of the indentation hardness measured on a cross section having a size of 200 μm × 200 μm is 1.0 GPa or less. The cemented carbide according to any one of (1) to (5). (7) The cemented carbide according to any one of (1) to (6) Including, Cutting tool blanks. (8) A cutting blade comprising the cemented carbide according to any one of (1) to (6). Equipped with cutting tools. (9) It is a rotary tool for processing printed circuit boards. (8) A cutting tool according to (8). (10) A step of rotating a workpiece or the cutting tool described in (8); bringing the workpiece into contact with the cutting tool; moving the cutting tool relatively away from the workpiece; Equipped with Manufacturing method for machined products. (11) The workpiece is a printed circuit board. (10) A method for producing a machined product according to (10).

[0090] Further advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0091] 1 PWB drill 2 Blade part 2a Chip discharge groove 2b cutting edge 3 Shank 4 Connecting part 4a First tapered section 4b Second tapered section 4c Cylindrical part 4d joint surface 5 PWB Drill Blanks 100 Work material

Claims

1. a plurality of hard particles containing W and C; a plurality of bonding particles containing at least one of Co, Ni, and Fe; Equipped with In a cross section having a size of 10 μm×10 μm, a ratio of a cross-sectional area of ​​the plurality of bonded particles to a sum of a cross-sectional area of ​​the plurality of hard particles and a cross-sectional area of ​​the plurality of bonded particles is 10% or more; The maximum value of the equivalent circle diameter of the plurality of combined particles is 0.2 μm or less. Cemented carbide.

2. the average value of the equivalent circle diameters of the plurality of hard particles is larger than the median value of the equivalent circle diameters of the plurality of bonded particles; The cemented carbide according to claim 1.

3. the average value of the equivalent circle diameters of the plurality of hard particles is larger than the maximum value of the equivalent circle diameters of the plurality of bonded particles; The cemented carbide according to claim 2.

4. The maximum value of the equivalent circle diameter of the plurality of combined particles is 0.1 μm or more. The cemented carbide according to claim 1.

5. a ratio of a cross-sectional area of ​​the plurality of bonding particles to a sum of a cross-sectional area of ​​the plurality of hard particles and a cross-sectional area of ​​the plurality of bonding particles is 30% or less; The cemented carbide according to claim 1.

6. The standard deviation of the indentation hardness measured on a cross section having a size of 200 μm × 200 μm is 1.0 GPa or less. The cemented carbide according to claim 1.

7. The cemented carbide according to any one of claims 1 to 6. Including, Cutting tool blanks.

8. A cutting blade comprising the cemented carbide according to any one of claims 1 to 6. Equipped with cutting tools.

9. It is a rotary tool for processing printed circuit boards. The cutting tool according to claim 8.

10. rotating a workpiece or the cutting tool according to claim 8; bringing the workpiece into contact with the cutting tool; moving the cutting tool relatively away from the workpiece; Equipped with Manufacturing method for machined products.

11. The workpiece is a printed circuit board. The method for manufacturing a machined product according to claim 10.

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