Carbide alloy materials and rotary tools for rotary tools

Abstract

To provide a cemented carbide stock for a rotary tool enabling the long life performance of the rotary tool when used as a rotary tool material, and a cutting tool provided therewith.SOLUTION: A cemented carbide stock for a rotary tool comprises tungsten carbide particles, and a bonded phase. The cemented carbide stock includes pores having an equivalent circle diameter of less than 0.2 μm by 9 or less in rectangular one measurement field of 24.9×18.8 μm, and the measurement field is provided at a central part of a cross section of the cemented carbide stock.SELECTED DRAWING: Figure 1

Description

Technical Field

[0006] , ,

[0001] The present disclosure relates to a cemented carbide material for a rotary tool and a rotary tool.

Background Art

[0002] Cemented carbide including tungsten carbide particles and a binder phase containing cobalt is widely used as a material for cutting tools (Patent Document 1).

Prior Art Documents

[0007] This disclosure makes it possible to provide rotary tools with a long tool life. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of an image of the cemented carbide material of Embodiment 1 taken with a scanning electron microscope. [Figure 2] Figure 2 is a diagram illustrating the position of the measurement field of view for the cemented carbide material in Embodiment 1. [Figure 3] Figure 3 illustrates a method for measuring the number of pores in the cemented carbide of a rotary tool according to Embodiment 2. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described. (1) This disclosure relates to cemented carbide materials for rotary tools, The cemented carbide material comprises tungsten carbide particles and a binder phase, The aforementioned cemented carbide material contains 9 or fewer pores with an equivalent circular diameter of less than 0.2 μm in a single rectangular measurement field measuring 24.9 μm × 18.8 μm. The measurement field is provided in the central part of the cross-section of the cemented carbide material, which is a cemented carbide material for a rotary tool.

[0010] This disclosure makes it possible to provide rotary tools with a long tool life.

[0011] (2) The average particle size of the tungsten carbide particles is preferably 0.40 μm or more and 1.00 μm or less. This further improves the tool life of the rotary tool.

[0012] (3) The average particle size of the tungsten carbide particles is preferably 0.40 μm or more and less than 0.80 μm. This further improves the tool life of the rotary tool.

[0013] (4) The cemented carbide material preferably contains 85.0% to 95.5% by volume of tungsten carbide particles and 0.5% to 15.0% by volume of the binder phase. This further improves the tool life of the rotary tool.

[0014] (5) The present disclosure relates to a rotary tool made of cemented carbide, The cemented carbide comprises tungsten carbide particles and a binder phase. The cemented carbide contains 9 or fewer pores with an equivalent circular diameter of less than 0.2 μm in each of the first, second, and third measurement fields. Each of the first, second, and third measurement fields is a rectangle measuring 24.9 μm × 18.8 μm. The first measurement field is provided on the cross-section of the cemented carbide, with the rotation axis P1 of the rotary tool as the normal, so as to include the rotation axis P1. The second measurement visual field is provided on the cross section of the cemented carbide so as to include a position P3 on a line segment L connecting the rotation axis P1 and the cutting edge P2 of the rotary tool and at a distance from the rotation axis P1 that is 1 / 3 of the length L1 of the line segment L. The third measurement visual field is a rotary tool provided on the cross section of the cemented carbide so as to include a position P4 on the line segment L and at a distance from the rotation axis P1 that is 2 / 3 of the length L1 of the line segment L.

[0015] The rotary tool of the present disclosure can have a long tool life.

[0016] [Details of Embodiments of the Present Disclosure] Specific examples of the cemented carbide material for the rotary tool of the present disclosure and the rotary tool using the same will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. Also, dimensional relationships such as length, width, thickness, depth, etc. have been appropriately changed for the clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0017] In this specification, the notation in the form of "A to B" means the upper and lower limits of the range (i.e., A or more and B or less). When there is no unit description for A and there is a unit description only for B, the units of A and B are the same.

[0018] In this specification, pores with a diameter of less than 0.2 μm are also referred to as "first pores", and pores with a diameter of 0.2 μm or more are also referred to as "second pores". The first pores and the second pores are collectively also referred to as "pores".

[0019] In this specification, a rotary tool means a tool that rotates about a rotation axis passing through itself to perform machining such as cutting. Examples of the rotary tool include a drill and an end mill.

[0020] [Embodiment 1: Cemented Carbide Material for Rotary Tool] One embodiment of the present disclosure (hereinafter also referred to as "this embodiment") is a cemented carbide material for rotary tools (hereinafter, "cemented carbide material for rotary tools" is also referred to as "cemented carbide material"), The cemented carbide material comprises tungsten carbide particles and a binder phase, The cemented carbide material contains 9 or fewer pores with an equivalent circular diameter of less than 0.2 μm in a single rectangular measurement field measuring 24.9 μm × 18.8 μm. The measurement field is located in the center of the cross-section of the cemented carbide material, which is a cemented carbide material for a rotary tool.

[0021] <Pore> The cemented carbide material of this embodiment contains 9 or fewer pores (first pores) with an equivalent circular diameter of less than 0.2 μm in a single rectangular measuring field of view measuring 24.9 μm × 18.8 μm, and this measuring field is located in the center of the cross-section of the cemented carbide material. The cemented carbide material having 9 or fewer first pores in the measuring field of view has excellent rigidity. Therefore, rotary tools made using this cemented carbide material have excellent straight-line performance and a long tool life. In addition, when the number of first pores in the cemented carbide material is small, chipping originating from the first pores is less likely to occur. Therefore, rotary tools made using this cemented carbide material have excellent chipping resistance and a long tool life.

[0022] The number of first pores in the above measurement field of the cemented carbide material is 9 or less, preferably 7 or less, preferably 5 or less, preferably 3 or less, and most preferably 0. The number of first pores is preferably 0 to 9, preferably 0 to 7, preferably 0 to 5, preferably 0 to 3, and most preferably 0.

[0023] In this embodiment, it is preferable that the cemented carbide material does not contain a second pore with an equivalent circular diameter of 0.2 μm or more in the above measurement field. This allows the cemented carbide material to have high rigidity and excellent fracture resistance.

[0024] In this specification, the method for measuring the number of first and second pores in the above measurement field of a cemented carbide material is as follows (A1) to (H1).

[0025] (A1) The cemented carbide material is cut so that the cross section normal to its longitudinal direction (axis) is exposed, and this cross section is polished to a mirror finish. Typically, cemented carbide material for rotary tools is in the shape of a round bar, so the longitudinal direction of the cemented carbide material corresponds to the direction in which the rotation axis of the rotary tool obtained by processing the cemented carbide material extends. Examples of methods for mirror polishing include polishing with diamond paste, using a focused ion beam (FIB) device, using a cross-section polisher (CP) device, and methods combining these.

[0026] (B1) The mirror-finished surface of the cemented carbide material is analyzed using energy-dispersive X-ray spectroscopy (SEM-EDX) to identify the elements contained in the cemented carbide material.

[0027] (C1) The mirror-finished surface of the cemented carbide material is photographed with a scanning electron microscope to obtain an image. The imaging area of ​​the image is set to the central part of the cross-section of the cemented carbide material, that is, a position that does not include parts that clearly have different properties from the bulk portion, such as the vicinity of the surface of the cemented carbide material (a position where the entire imaging area is the bulk portion of the cemented carbide material). The observation magnification is set to 5000x.

[0028] Figure 1 is an example of a scanning electron microscope image of the cemented carbide material 1 of this embodiment. In the lower right scale of Figure 1, one division represents 1 μm. In Figure 1, the cemented carbide material 1 contains pores 2. As shown in Figure 1, pores 2 are very small and may be difficult to identify in the scanning electron microscope image. However, as explained in (F1) below, it is possible to identify the pores by superimposing the binarized image of the scanning electron microscope image with an elemental mapping image.

[0029] (D1) The imaging area described in (C1) above is analyzed using scanning electron microscopy (SEM-EDX) to determine the distribution of the elements identified in (B1) above within the imaging area and to obtain an elemental mapping image. In the elemental mapping image, no elements are present in the pore regions.

[0030] (E1) The captured image obtained in (C1) above is imported into a computer, and image processing is performed using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ) to perform binarization. Specifically, after importing the captured image into the computer, pressing the "MakeBinary" button on the computer screen executes the binarization process according to the conditions pre-set in the image analysis software. In the image after binarization, tungsten carbide particles are shown in the lightest color (white), and the binding phase and pores are shown in black.

[0031] (F1) By overlaying the elemental mapping image obtained in (D1) above with the binarized image obtained in (E1) above, the regions where pores exist are identified on the binarized image. Specifically, among the regions shown in black in the binarized image, the regions where elements are absent in the elemental mapping image correspond to the regions where pores exist.

[0032] (G1) A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the obtained binarized image. Based on the number of pixels in the pore and identified region within the measurement field of view, the equivalent circle diameter of the pore (Heywood diameter: equivalent circle diameter of an equal area) is calculated using the image analysis software described above.

[0033] (H1) Based on the calculation results in (G1) above, the number of first pores with an equivalent circle diameter of less than 0.2 μm and the number of second pores with an equivalent circle diameter of 0.2 μm or more in the measurement field are measured.

[0034] As far as the applicant has measured, as long as the measurements are performed on the same sample, the variation in the measurement results is small even when arbitrarily setting the cutting location of the cross-section of the cemented carbide material, arbitrarily setting the imaging area described in (C1) above on the cross-section, and measuring the number of first and second pores multiple times according to the procedures in (B1) to (H1) above. This confirms that arbitrarily setting the cutting location of the cross-section of the cemented carbide material and arbitrarily setting the imaging area of ​​the captured image does not result in arbitrary results. For example, as shown in Figure 2, five imaging areas are set on the cross-section of cemented carbide material 1, including the central part A and positions A1, A2, A3, and A4, each at the same distance from the central part A. Even when measuring the number of first and second pores in each of these five areas according to the procedures in (B1) to (H1) above, the variation in the measurement results is small, and it was confirmed that arbitrarily setting the imaging area of ​​the captured image does not result in arbitrary results.

[0035] <Tungsten carbide particles> ≪Composition≫ Tungsten carbide particles (hereinafter also referred to as "WC particles") are particles made of tungsten carbide. Here, the tungsten carbide may be pure tungsten carbide that does not contain impurity elements, or it may be tungsten carbide that contains impurity elements, as long as the effects of this disclosure are not impaired. The content of impurities contained in the tungsten carbide (if there are two or more elements constituting the impurities, their total concentration) is preferably less than 0.1 mass% of the total amount of WC particles. The content of impurities in the WC particles is measured by ICP emission spectrometry (Inductively Coupled Plasma) Emission Spectroscopy (measuring device: Shimadzu Corporation "ICPS-8100" trademark).

[0036] ≪Average particle size≫ In this embodiment, the average particle size of the tungsten carbide particles is preferably 0.40 μm or more and 1.00 μm or less, more preferably 0.40 μm or more and less than 0.80 μm, and even more preferably 0.42 μm or more and less than 0.80 μm. This further improves tool life.

[0037] In this specification, the average particle size of tungsten carbide particles contained in the cemented carbide material refers to the equivalent circle diameter (Heywood diameter) D50 of the WC particles contained in the cemented carbide material (the equivalent circle diameter at which the cumulative frequency based on the number of particles reaches 50%, the median diameter D50). The method for measuring the particle diameter of each particle to calculate the average particle size of the WC particles is as follows (A2) to (B2).

[0038] (A2) By superimposing the elemental mapping image obtained by the same method as (A1) to (E1) described in the method for measuring the number of first and second pores in the above measurement field of the cemented carbide material with the image after binarization, the region where tungsten carbide particles exist is identified on the binarized image. Specifically, the region shown in the lightest color (white) in the binarized image, where tungsten (W) and carbon (C) exist in the elemental mapping image, corresponds to the region where tungsten carbide particles exist.

[0039] (B2) A rectangular measurement field of view measuring 24.9 μm × 18.8 μm is set in the image after the binarization process described above. The equivalent circle diameter (Heywood diameter: equivalent circle diameter of an equal area) of each tungsten carbide particle in the measurement field of view is calculated using the image analysis software described above.

[0040] As far as the applicant has measured, as long as the measurements are performed on the same sample, the variation in the measurement results is small even when the cutting location of the cross-section of the cemented carbide material is arbitrarily set, the imaging area described in (C1) above is arbitrarily set on the cross-section, and the average particle size of tungsten carbide particles is measured multiple times according to the procedures in (A2) and (B2) above. It has been confirmed that arbitrarily setting the cutting location of the cross-section of the cemented carbide material and arbitrarily setting the imaging area of ​​the captured image does not result in arbitrary results.

[0041] <Binded phase> The cemented carbide of this embodiment includes a binder phase. Preferably, the binder phase contains cobalt as its main component. Here, "containing cobalt as its main component" means that the cobalt content in the binder phase is 90% by mass or more and 100% by mass or less. The cobalt content in the binder phase can be measured by ICP emission spectrometry (equipment used: Shimadzu Corporation's "ICPS-8100" trademark).

[0042] The bonding phase can include, in addition to cobalt, chromium, vanadium, nickel, tungsten, titanium, niobium, tantalum, and others.

[0043] <Composition of cemented carbide material> The cemented carbide material of this embodiment preferably contains tungsten carbide particles in an amount of 85.0% to 95.5% by volume and a binder phase in an amount of 0.5% to 15.0% by volume. This further improves the tool life of rotary tools using the cemented carbide material.

[0044] The lower limit of the tungsten carbide particle content in cemented carbide material can be 85.0 volume% or more, 88.0 volume% or more, or 90.0 volume% or more. The upper limit of the tungsten carbide particle content in cemented carbide material can be 99.5 volume% or less, or 95.0 volume% or less. The tungsten carbide particle content in cemented carbide material can be 85.0 volume% or more and 99.5 volume% or less, 88.0 volume% or more and 99.5 volume% or less, 90.0 volume% or more and 99.5 volume% or less, 85.0 volume% or more and 95.0 volume% or less, 88.0 volume% or more and 95.0 volume% or less, or 90.0 volume% or more and 95.0 volume% or less.

[0045] The lower limit of the binder phase content in cemented carbide material can be 0.5 volume% or more, or 5.0 volume% or more. The upper limit of the binder phase content in cemented carbide material can be 15.0 volume% or less, 12.0 volume% or less, or 10.0 volume% or less. The binder phase content in cemented carbide material can be 0.5 volume% or more and 15.0 volume% or less, 5.0 volume% or more and 15.0 volume% or less, 0.5 volume% or more and 12.0 volume% or less, 5.0 volume% or more and 12.0 volume% or less, 0.5 volume% or more and 10.0 volume% or less, or 5.0 volume% or more and 10.0 volume% or less.

[0046] The cemented carbide material may contain 85.0% to 99.5% by volume of tungsten carbide particles and 0.5% to 15.0% by volume of the binder phase. The cemented carbide material may contain 88.0% to 99.5% by volume of tungsten carbide particles and 0.5% to 12.0% by volume of the binder phase. The cemented carbide material may contain 90.0% to 99.5% by volume of tungsten carbide particles and 0.5% to 10% by volume of the binder phase. The cemented carbide material may contain 85.0% to 95.0% by volume of tungsten carbide particles and 5.0% to 15.0% by volume of the binder phase. The cemented carbide material may contain tungsten carbide particles in an amount of 88.0% to 95.0% by volume, and a binder phase in an amount of 5.0% to 12.0% by volume. The cemented carbide material may contain tungsten carbide particles in an amount of 90.0% to 95.0% by volume, and a binder phase in an amount of 5.0% to 10.0% by volume.

[0047] The cemented carbide material may consist of tungsten carbide particles and a binder phase. In addition to tungsten carbide particles and the binder phase, the cemented carbide material may contain hard phase particles other than tungsten carbide and / or impurities. Examples of such hard phase particles include titanium, niobium, and tantalum. The impurity content of the cemented carbide material may be 0.1% by mass or less. The cemented carbide material may consist of tungsten carbide particles, a binder phase, and impurities. The cemented carbide material may consist of tungsten carbide particles, a binder phase, hard phase particles, and impurities.

[0048] The methods for measuring the respective content (volume %) of tungsten carbide particles and the binding phase in cemented carbide materials are as follows (A3) to (B3).

[0049] (A3) By superimposing the elemental mapping image obtained by the same method as (A1) to (E1) described in (A3) for measuring the number of first and second pores in the above measurement field of the cemented carbide material with the image after binarization, the regions where tungsten carbide particles exist and the regions where the bonding phase exists are identified on the binarized image. Specifically, the regions shown in the lightest color (white) in the binarized image, where tungsten (W) and carbon (C) exist in the elemental mapping image, correspond to the regions where tungsten carbide particles exist. The regions shown in black in the binarized image, where cobalt (Co) exists in the elemental mapping image, correspond to the regions where the bonding phase exists.

[0050] (B3) A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the image after the binarization process described above. Using the image analysis software described above, the area percentages of the tungsten carbide particles and the binder phase are measured with the area of ​​the entire measurement field of view as the denominator. In this specification, the area percentage of the tungsten carbide particles corresponds to the tungsten carbide particle content (volume %) of the cemented carbide material, and the area percentage of the binder phase corresponds to the binder phase content (volume %) of the cemented carbide material.

[0051] If the cemented carbide material contains hard phase particles in addition to WC particles and the binder phase, the region where the hard phase particles exist is identified in (A3) above, and their area percentage is measured in (B3) above. The area percentage of the hard phase particles corresponds to the hard phase particle content (volume %) of the cemented carbide material.

[0052] As far as the applicant has measured, as long as the measurements are performed on the same sample, the variation in measurement results is small even when the cutting location of the cross-section of the cemented carbide material is arbitrarily set, the imaging area described in (C1) above is arbitrarily set on the cross-section, and the area percentage measurements of tungsten carbide particles, binder phase, hard phase particles, and impurities are performed multiple times according to the procedures in (A3) and (B3) above. It has been confirmed that arbitrarily setting the cutting location of the cross-section of the cemented carbide material and arbitrarily setting the imaging area of ​​the captured image does not result in arbitrary results.

[0053] <Manufacturing method for cemented carbide material for rotary tools> The cemented carbide material for rotary tools according to this embodiment can be manufactured by performing the following steps in the order described above: preparation of raw material powder, mixing, granulation, molding, sintering, HIP treatment, and cooling. Each step will be described below.

[0054] ≪Preparation process≫ The preparation process involves preparing the raw material powders for the cemented carbide material. Examples of raw material powders include tungsten carbide powder, which is the raw material for tungsten carbide particles; cobalt (Co) powder, which is the raw material for the binder phase; and chromium carbide (Cr3C2) powder and vanadium carbide (VC) powder, which are grain growth inhibitors. Furthermore, hard phase powder, which is the raw material for hard phase particles, can also be used. Commercially available tungsten carbide powder, cobalt powder, chromium carbide powder, vanadium carbide powder, and hard phase powder can be used.

[0055] The average particle size of tungsten carbide powder can be between 0.7 μm and 1.3 μm. The average particle size of cobalt powder can be between 0.8 μm and 1.2 μm. The average particle size of chromium carbide powder can be between 1.0 μm and 2.0 μm. The average particle size of vanadium carbide powder can be between 0.5 μm and 1.0 μm. The average particle size of hard phase powder can be between 0.2 μm and 2.0 μm. In this specification, the average particle size of the raw material powder refers to the median diameter d50 of the spherical equivalent diameter of the raw material powder. The average particle size of the raw material powder is measured using a particle size distribution analyzer (product name: MT3300EX) manufactured by Microtrac.

[0056] ≪Mixing process≫ The mixing step is the process of mixing the individual raw material powders prepared in the preparation step. The mixing step yields a mixed powder in which the individual raw material powders are combined.

[0057] The proportion of tungsten carbide powder in the mixed powder can be, for example, 84% by mass or more and 99.5% by mass or less. The proportion of cobalt powder in the mixed powder can be, for example, 0.5% by mass or more and 15% by mass or less. The proportion of chromium carbide powder in the mixed powder can be, for example, 0.1% by mass or more and 1.2% by mass or less. The proportion of vanadium carbide powder in the mixed powder can be, for example, 0% by mass or more and 0.2% by mass or less.

[0058] An attritor or ball mill can be used to mix each raw material powder. The mixing time in an attritor can be between 5 hours and 20 hours. The mixing time in a ball mill can be between 20 hours and 70 hours.

[0059] ≪Pelletization process≫ The mixed powder obtained by mixing is dried by a water bath to obtain dried raw material powder. A mixed solution is prepared by mixing polyethylene oxide (weight-average molecular weight (Mw): approximately 100,000) and glycerin in a volume ratio of 1:1. The above dried raw material powder is granulated by spraying this mixed solution onto it. Hereinafter, the mixed solution sprayed onto the dried raw material powder will also be referred to as the binder.

[0060] ≪Molding process≫ The molding process involves shaping the mixed powder obtained in the mixing process into a shape suitable for a rotary tool (e.g., a round bar) to obtain a molded body. The molding method and conditions in the molding process can be general methods and conditions, and are not particularly limited.

[0061] ≪Sintering Process≫ The sintering process is a process in which the molded body obtained in the molding process is sintered to obtain cemented carbide material. The sintering process can be carried out according to the following procedure.

[0062] The molded body is placed in a sintering furnace and heated to 800°C in a vacuum (1.0 Pa or less) at a heating rate of 0.5°C / min.

[0063] Next, N2 gas is introduced into the sintering furnace, and the furnace is heated to 1200°C at a heating rate of 0.5°C / min under an N2 gas atmosphere (30kPaG). Subsequently, the furnace is evacuated (1.0Pa or less), and the furnace is heated to 1370°C at a heating rate of 0.5°C / min. Finally, Ar gas is introduced into the sintering furnace, and the furnace is held at 1370°C for 120-240 minutes under an Ar gas atmosphere (140kPaG) to obtain cemented carbide material.

[0064] ≪HIP Treatment Process≫ The HIP treatment process is a process of applying HIP (Hot Isostatic Pressing) to cemented carbide material after sintering. For example, a temperature of 1320°C and a pressure of 10 MPa can be applied to the cemented carbide material for 60 minutes using Ar gas as the pressure medium.

[0065] ≪Cooling process≫ The cooling process involves cooling the cemented carbide material after HIP treatment. For example, the cemented carbide material can be rapidly cooled in Ar gas after HIP treatment.

[0066] Features of the manufacturing method for cemented carbide material in this embodiment The cemented carbide material obtained by the above manufacturing method has 9 or fewer pores with an equivalent circle diameter of less than 0.2 μm in a single rectangular measurement field of view measuring 24.9 μm × 18.8 μm. The reason for this is presumed to be as follows.

[0067] Pores in cemented carbide material are presumed to be formed when the binder vaporizes during the sintering process. In the above manufacturing method, a mixed solution of polyethylene oxide and glycerin is used as the binder in the granulation process, and the heating rate in the sintering process is slow. This binder has a large molecular weight and does not vaporize easily. Therefore, in the above manufacturing method, when the temperature rises in the sintering process, vaporization of the binder occurs almost simultaneously inside and near the surface of the molded body, and the binder does not remain inside the molded body but is easily discharged to the outside. Furthermore, in the above sintering process, the molded body is held at the maximum temperature (1370°C) and in an Ar gas atmosphere (140kPaG) for a certain period of time (120 minutes). By pressurizing the molded body at a high temperature, the structure flows, and the pores become smaller. Therefore, in the cemented carbide material after sintering, pores are less likely to exist inside, and the number of pores is reduced overall. Also, even if pores are present, their size is minute. The inventors have newly discovered, through diligent research, that by using a mixed solution of polyethylene oxide and glycerin as a binder and slowing down the heating rate during the sintering process, it is possible to obtain a cemented carbide material with 9 or fewer pores having an equivalent circle diameter of less than 0.2 μm in a single rectangular measurement field of 24.9 μm × 18.8 μm.

[0068] On the other hand, in conventional methods for manufacturing cemented carbide materials, granulation is performed by spray drying for efficiency reasons, and polyethylene glycol, which is suitable for spray drying, is used as a binder. Polyethylene glycol has a small molecular weight and is easily vaporized. However, polyethylene oxide used in this embodiment cannot be used for spray drying because it causes clogging of the spray dryer. Furthermore, in conventional methods for manufacturing cemented carbide materials, the heating rate during sintering is set to 10-20°C / min for efficiency reasons, and sintering at the maximum temperature is performed under reduced pressure or vacuum. As a result, the binder near the surface of the molded body is easily vaporized during heating, but the binder inside the molded body is not easily vaporized. Therefore, in cemented carbide materials after sintering, pores tend to exist inside, and the structure tends to be non-uniform.

[0069] [Embodiment 2: Rotary Tool] This embodiment is a rotary tool made of cemented carbide, The cemented carbide comprises tungsten carbide particles and a binder phase, The cemented carbide contains 9 or fewer pores with an equivalent circular diameter of less than 0.2 μm in each of the first, second, and third measurement fields. Each of the first, second, and third measurement fields is a rectangle measuring 24.9 μm × 18.8 μm. The first measuring field is provided on the cross-section of the cemented carbide, with the rotation axis P1 of the rotary tool as the normal, so as to include the rotation axis P1. The second measuring field is provided on the cross-section of the cemented carbide, on the line segment L connecting the rotation axis P1 and the cutting edge P2 of the rotary tool, and includes a position P3 at a distance from the rotation axis P1 that is 1 / 3 of the length L1 of the line segment L. The third measuring field is provided on the cross-section of the cemented carbide, on the line segment L, and includes a position P4 at a distance from the rotation axis P1 that is 2 / 3 of the length L1 of the line segment L, and is a rotary tool.

[0070] Examples of rotary tools in this embodiment include drills and end mills. The rotary tool in this embodiment may be entirely made of the above-mentioned cemented carbide alloy. Alternatively, a part of it may be made of the above-mentioned cemented carbide alloy. Here, "a part of it being made of the above-mentioned cemented carbide alloy" refers to an embodiment in which at least the part of the drill and end mill involved in cutting (for example, the body part other than the shank) is made of the above-mentioned cemented carbide alloy.

[0071] <Pore> The cemented carbide alloy constituting the rotary tool of this embodiment contains 9 or fewer pores (first pores) with an equivalent circular diameter of less than 0.2 μm in each of the first, second, and third measuring fields. The cemented carbide alloy constituting the rotary tool of this embodiment has excellent rigidity. Therefore, the rotary tool of this embodiment has excellent straight-line stability and a long tool life. Furthermore, when the number of first pores in the cemented carbide alloy is small, chipping originating from the first pores is less likely to occur. Therefore, the rotary tool using this cemented carbide alloy has excellent chipping resistance and a long tool life.

[0072] The number of first pores in the first, second, and third measuring fields of the above cemented carbide is preferably 9 or less, preferably 7 or less, preferably 5 or less, preferably 3 or less, and most preferably 0. The number of first pores is preferably 0 to 9, preferably 0 to 7, preferably 0 to 5, preferably 0 to 3, and most preferably 0.

[0073] In this embodiment, it is preferable that the rotary tool does not contain a second pore with an equivalent circular diameter of 0.2 μm or more in each of the first, second, and third measuring fields of the cemented carbide. This allows the rotary tool to have high rigidity and excellent fracture resistance.

[0074] In this specification, the method for measuring the number of first pores and second pores in the first, second, and third measurement fields of the cemented carbide constituting the rotary tool is as follows (A4) to (H4).

[0075] (A4) The cemented carbide that constitutes the rotary tool is cut out so that the cross section normal to the rotation axis of the rotary tool is exposed, and the cross section is polished to a mirror finish. Examples of methods for mirror polishing include polishing with diamond paste, using a focused ion beam (FIB) device, using a cross-section polisher (CP) device, and methods combining these.

[0076] (B4) The cross-section of the cemented carbide alloy, which has been polished to a mirror finish, is analyzed using energy-dispersive X-ray spectroscopy (SEM-EDX) to identify the elements contained in the cemented carbide alloy.

[0077] (C4) The above cross-section of the cemented carbide is photographed using a scanning electron microscope. When taking the photograph, the imaging area is set so that the rotation axis P1 and the cutting edge P2 of the rotary tool 3 are included, as shown in Figure 3. The observation magnification is 5000x. In the above cross-section, the length L1 of the line segment L connecting the rotation axis P1 and the cutting edge P2 is 1 / 2 the diameter D of the rotary tool.

[0078] (D4) The imaging area described in (C4) above is analyzed using scanning electron microscopy (SEM-EDX) to determine the distribution of the elements identified in (B4) above within the imaging area and to obtain an elemental mapping image. In the elemental mapping image, no elements are present in the pore regions.

[0079] (E4) The captured images obtained in (C4) above are imported into a computer and image processing is performed using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ) to perform binarization. Specifically, after importing the images into the computer, pressing the "MakeBinary" button on the computer screen executes the binarization process according to the conditions pre-set in the image analysis software. In the image after binarization, tungsten carbide particles are shown in the lightest color (white), and the binding phase and pores are shown in black.

[0080] (F4) By overlaying the elemental mapping image obtained in (D4) above with the binarized image obtained in (E4) above, the regions where pores exist are identified on the binarized image. Specifically, among the regions shown in black in the binarized image, the regions where elements are absent in the elemental mapping image correspond to the regions where pores exist.

[0081] (G4) In the resulting binarized image, the first, second, and third measurement fields are set. Each of the first, second, and third measurement fields is a rectangle measuring 24.9 μm × 18.8 μm. The method for setting the positions of the first, second, and third measurement fields will be explained using Figure 3. As shown in Figure 3, in the binarized image, a line segment L is drawn connecting the rotation axis P1 of the rotary tool 3 and the cutting edge P2 of the rotary tool (in Figure 2, the line segment L is shown as a dotted line). A position P3 is set on the line segment L, where the distance from the rotation axis P1 is 1 / 3 of the length L1 of the line segment L. A position P4 is set on the line segment L, where the distance from the rotation axis P1 is 2 / 3 of the length L1 of the line segment L. The first measurement field is set to include the rotation axis P1. The second measurement field is set to include the position P3. The third measurement field is set to include the position P4. If the groove 4 of the rotary tool is deep and the entire third measurement field cannot be set on the cross-section of the rotary tool, the third measurement field is set as follows: In the image after the above binarization process, draw a circle R1 with the rotation axis P1 as the center and a radius of 2 / 3 of the length L1 of the line segment L. Set the third measurement field so that it includes any point on circle R1 and the entire measurement field is located on the cross-section of the rotary tool.

[0082] In each of the three measurement fields, the equivalent circular diameter of the pore (Heywood diameter: equivalent circular diameter of an equal area) is calculated using the image analysis software based on the number of pixels in the area identified as a pore within the measurement field.

[0083] (H4) Based on the calculation results in (G4) above, the number of first pores with an equivalent circle diameter of less than 0.2 μm and the number of second pores with an equivalent circle diameter of 0.2 μm or more in each measurement field are measured. If the number of first pores is 9 or less in all three measurement fields of the cemented carbide constituting the rotary tool, it is determined that the cemented carbide contains 9 or fewer pores with an equivalent circle diameter of less than 0.2 μm in each of the first, second, and third measurement fields.

[0084] As far as the applicant has measured, as long as the measurements are performed on the same sample, the variation in the measurement results is small even when the cutting location of the cross-section of the cemented carbide is arbitrarily set, and the position of the measurement field is arbitrarily set according to the procedure (B4) to (H4) above, and the number of first and second pores is measured multiple times. It has been confirmed that arbitrarily setting the cutting location of the cross-section of the cemented carbide and the position of the measurement field does not result in arbitrary results.

[0085] <Tungsten carbide particles> ≪Composition≫ The composition of the tungsten carbide particles in this embodiment can be the same as the composition of the tungsten carbide particles described in Embodiment 1.

[0086] ≪Average particle size≫ In this embodiment, the average particle size of the tungsten carbide particles (median diameter D50 of the equivalent diameter of an equal-area circle) is preferably 0.40 μm or more and 1.00 μm or less, more preferably 0.40 μm or more and less than 0.80 μm, and even more preferably 0.42 μm or more and less than 0.80 μm. This further improves tool life.

[0087] In this specification, the average particle size of tungsten carbide particles contained in the cemented carbide of a rotary tool means the equivalent circle diameter (Heywood diameter) D50 of the WC particles contained in the cemented carbide (the equivalent circle diameter where the cumulative frequency based on the number of particles reaches 50%, the median diameter D50). The method for measuring the particle size of each particle to calculate the average particle size of the tungsten carbide particles (median diameter D50 of the equivalent circle diameter) is as follows (A5) to (B5).

[0088] (A5) By superimposing an elemental mapping image obtained by the same method as (A4) to (E4) described in (A5) Method for measuring the number of first and second pores in cemented carbide of rotary tools with a binarized image, the region where tungsten carbide particles exist is identified on the binarized image. Specifically, the region shown in the lightest color (white) in the binarized image, where tungsten (W) and carbon (C) are present in the elemental mapping image, corresponds to the region where tungsten carbide particles exist.

[0089] (B5) In the image after the binarization process described above, a first measurement field, a second measurement field, and a third measurement field are set. Using the image analysis software described above, the equivalent diameter of an equiarea circle (Heywood diameter) of each tungsten carbide particle is calculated in each of the three measurement fields. The average value of the average particle size (median diameter D50 of the equivalent diameter of an equiarea circle) of the tungsten carbide particles in the three measurement fields is calculated. In this specification, this average value corresponds to the average particle size of the tungsten carbide particles contained in the cemented carbide of the rotary tool.

[0090] As far as the applicant has measured, as long as the measurements are performed on the same sample, the variation in the measurement results is small even when the cutting location of the cemented carbide cross-section is arbitrarily set, and the position of the measurement field is arbitrarily set according to the procedure (B4) to (H4) above, and the average particle size of tungsten carbide particles is measured multiple times. It has been confirmed that arbitrarily setting the cutting location of the cemented carbide cross-section and the position of the measurement field does not result in arbitrary results.

[0091] <Binded phase> The composition of the bonding phase in this embodiment can be the same as the composition of the bonding phase described in Embodiment 1.

[0092] <Composition of cemented carbide> The composition of the cemented carbide in this embodiment (such as the content of tungsten carbide particles, the content of the binder phase, and the constituent components) can be the same as the composition of the cemented carbide material described in Embodiment 1.

[0093] The method for measuring the respective content (volume %) of tungsten carbide particles and the binding phase in the cemented carbide of the above-mentioned rotary tool is as follows (A6) to (B6).

[0094] (A6) By superimposing an elemental mapping image obtained by the same method as (A4) to (E4) described in (A6) Method for measuring the number of first and second pores in cemented carbide for rotary tools with a binarized image, the regions where tungsten carbide particles and the regions where the bonding phase exists are identified on the binarized image. Specifically, the regions shown in the lightest color (white) in the binarized image, where tungsten (W) and carbon (C) are present in the elemental mapping image, correspond to the regions where tungsten carbide particles exist. The regions shown in black in the binarized image, where cobalt (Co) is present in the elemental mapping image, correspond to the regions where the bonding phase exists.

[0095] (B6) In the obtained binarized image, a first measurement field, a second measurement field, and a third measurement field are set. Using the image analysis software described above, the area percentages of tungsten carbide particles and the binder phase are measured in each of the three measurement fields, with the total area of ​​the measurement field as the denominator. The average value of the area percentages of tungsten carbide particles in the three measurement fields is calculated. In this specification, this average value corresponds to the tungsten carbide particle content (volume %) of the cemented carbide of the rotary tool. The average value of the area percentages of the binder phase in the three measurement fields is calculated. In this specification, this average value corresponds to the binder phase content (volume %) of the cemented carbide of the rotary tool.

[0096] As far as the applicant has measured, as long as the measurements are performed on the same sample, the variation in the measurement results is small even when the cutting location of the cemented carbide cross-section is arbitrarily set, and the position of the measurement field is arbitrarily set according to the procedure (B4) to (H4) above, and the tungsten carbide particle content and the binder phase content are measured multiple times. It has been confirmed that arbitrarily setting the cutting location of the cemented carbide cross-section and the position of the measurement field does not result in arbitrary results.

[0097] The rotary tool according to this embodiment may further include a hard coating that covers at least a portion of the surface of a substrate made of cemented carbide. For example, diamond-like carbon or diamond can be used as the hard coating.

[0098] <Manufacturing method for rotary tools> The rotary tool of this embodiment can be obtained, for example, by machining the cemented carbide material for the rotary tool of Embodiment 1. During machining, the machining process should be carried out in a way that does not include parts that have properties clearly different from the bulk portion, such as the area near the surface of the cemented carbide material.

[0099] [Note 1] This disclosure relates to a cemented carbide material for rotary tools, The above cemented carbide material comprises tungsten carbide particles and a binder phase. The above cemented carbide material contains 0 to 9 pores with an equivalent circular diameter of less than 0.2 μm in a single rectangular measurement field of 24.9 μm × 18.8 μm, and does not contain any pores with an equivalent circular diameter of 0.2 μm or more. The measurement field is provided in the central part of the cross-section of the cemented carbide material, which is a cemented carbide material for a rotary tool. [Note 2] This disclosure relates to a rotary tool made of cemented carbide, The cemented carbide comprises tungsten carbide particles and a binder phase. The cemented carbide contains 9 or fewer pores with an equivalent circular diameter of less than 0.2 μm in each of the first, second, and third measurement fields, and does not contain any pores with an equivalent circular diameter of 0.2 μm or more. Each of the first, second, and third measurement fields is a rectangle measuring 24.9 μm × 18.8 μm. The first measurement field is provided on the cross-section of the cemented carbide, with the rotation axis P1 of the rotary tool as the normal, so as to include the rotation axis P1. The second measurement field is provided on the cross-section of the cemented carbide, on the line segment L connecting the rotation axis P1 and the cutting edge P2 of the rotary tool, and includes a position P3 at a distance from the rotation axis P1 that is 1 / 3 of the length L1 of the line segment L. The third measuring field is a rotary tool provided on the cross-section of the cemented carbide, on the line segment L, and including a position P4 whose distance from the rotation axis P1 is 2 / 3 of the length L1 of the line segment L. [Examples]

[0100] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0101] <Manufacturing of cemented carbide materials> The cemented carbide materials for each sample were prepared using the following procedure. Seven cemented carbide materials were prepared for each sample. ≪Preparation process≫ As raw material powders, we prepared tungsten carbide (WC) powder, cobalt (Co) powder, chromium carbide (Cr3C2) powder, and vanadium carbide (VC) powder.

[0102] As tungsten carbide powders, we used tungsten carbide powders "WC08" (average particle size 0.7-0.9 μm), "WC10" (average particle size 0.9-1.1 μm), and "WC12" (average particle size 1.1-1.3 μm) manufactured by Allied Material Co., Ltd. The tungsten carbide powders used in each sample are shown in the "WC Powder" column of Table 1.

[0103] The average particle size of the cobalt (Co) powder is 1 μm, the average particle size of the vanadium carbide (VC) powder is 0.8 μm, and the average particle size of the chromium carbide (Cr3C2) powder is 1 μm. The Co powder, VC powder, and Cr3C2 powder are commercially available. The average particle size of the raw material powders was measured using a particle size distribution analyzer (product name: MT3300EX) manufactured by Microtrac.

[0104] ≪Mixing process≫ The nuclear raw material powders were mixed in the proportions shown in the "Mixed Powder (mass%)" column of Table 1 to prepare the mixed powder. For example, the notation "0.1Cr3C2-0.2VC-10Co-remainder WC" in the "Mixed Powder (mass%)" column for Sample 1 indicates that the Cr3C2 powder content is 0.1 mass%, the VC powder content is 0.2 mass%, the Co powder content is 10 mass%, and the remainder (89.7 mass%) is WC powder. Mixing was performed using an attritor (indicated as "ATR" in Table 1). The mixing time in the attritor is shown in the "Mixing / Time" column of Table 1. For example, the mixing time for Sample 1 was 15h (15 hours).

[0105] ≪Pelletization process≫ The mixed powder obtained by mixing was dried by a water bath to obtain dried raw material powder. A mixed solution was prepared by mixing polyethylene oxide (weight-average molecular weight (Mw): approximately 100,000) and glycerin in a volume ratio of 1:1. The above dried raw material powder was granulated by applying this mixed solution by spraying.

[0106] ≪Molding process≫ The obtained granulated powder was press-molded to produce a round bar-shaped molded body with a diameter of 3.4 mm.

[0107] ≪Sintering Process≫ The molded body was placed in a sintering furnace and heated to 800°C at a heating rate of 0.5°C / min in a vacuum (1.0 Pa or less). Subsequently, N2 gas was introduced into the sintering furnace, and the body was heated to 1200°C under an N2 gas atmosphere (30 kPaG) at the heating rate specified in the "Heating Rate (°C / min)" column for "800°C~1200°C" in the "Sintering Process" section of Table 1. Subsequently, the sintering furnace was evacuated (1.0 Pa or less), and the body was heated to 1370°C at a heating rate of 0.5°C / min. Subsequently, under the atmosphere specified in the "Atmosphere" column for "1370°C" in the "Sintering Process" section of Table 1, the body was held at 1370°C for the time specified in the "Holding Time (minutes)" column for "1370°C" in the "Sintering Process" section of Table 1 to obtain a cemented carbide material.

[0108] ≪HIP Treatment Process≫ Next, the sintered cemented carbide material was subjected to HIP treatment. Specifically, the cemented carbide material was subjected to a temperature of 1320°C and a pressure of 10 MPa for 60 minutes, using Ar gas as the pressure medium.

[0109] ≪Cooling process≫ Next, the cemented carbide material was cooled after the HIP treatment.

[0110] <Manufacturing of rotary tools> Round bars made from cemented carbide material (samples 1-8, sample 1-1, and sample 1-2) were processed to produce five small-diameter drills with a diameter of φ0.2 mm.

[0111] Round bars made from cemented carbide material, sample 9 and samples 1-3, were machined to produce five 3-flute end mills with a diameter of φ3 mm.

[0112] [Table 1]

[0113] [evaluation] <Superhard alloy material> For each sample of cemented carbide material before machining into a rotary tool, the composition, average particle size of tungsten carbide particles, composition of the binder phase, and number of pores were measured.

[0114] ≪Composition of cemented carbide material≫ For each cemented carbide material sample, the content (volume %) of tungsten carbide particles and the binder phase was measured. The specific measurement method is described in Embodiment 1, so it will not be repeated here. The content (volume %) of the binder phase is shown in the "Volume %" column of "Binder Phase" under "Cemented Carbide Material" in Table 2. In all samples, the sum of the volume % of WC particles, the volume % of the binder phase, and the volume % of pores was 100 volume %.

[0115] ≪Average particle size of tungsten carbide particles≫ The average particle size of tungsten carbide particles was measured for each cemented carbide material sample. The specific measurement method is described in Embodiment 1, so it will not be repeated here. The results are shown in the "Average Particle Size (μm)" column of "WC Particles" under "Cemented Carbide Material" in Table 2.

[0116] ≪Composition of the bonded phase≫ The composition of the binder phase of each cemented carbide material sample was measured by ICP emission spectrometry. In all samples, the binder phase was confirmed to contain Co, Cr, and V. In all samples, the binder phase was confirmed to contain 90% or more by mass of cobalt.

[0117] ≪Number of pores≫ For each cemented carbide material sample, the number of pores with an equivalent circle diameter of less than 0.2 μm (first pores) and pores with an equivalent circle diameter of 0.2 μm or more (second pores) was measured within a rectangular measurement field of view measuring 24.9 μm × 18.8 μm. The specific measurement method is described in Embodiment 1, so that explanation will not be repeated. The results are shown in the "Less than 0.2 μm (pores)" and "0.2 μm or more (pores)" columns of "Number of Pores" under "Cemented Carbide Material" in Table 2.

[0118] <Rotating Tools> For each sample of the cemented carbide rotary tool, the average particle size of tungsten carbide particles, the number of pores, and the composition of the cemented carbide were measured.

[0119] ≪Average particle size of tungsten carbide particles≫ The average particle size of tungsten carbide particles was measured for the cemented carbide of the rotary tools in each sample. The specific measurement method is described in Embodiment 2, so it will not be repeated here. The results are shown in the "Average Particle Size (μm)" column of "WC Particles" under "Rotating Tools" in Table 2.

[0120] ≪Number of pores≫ For each sample of the cemented carbide rotary tool, the number of pores with an equivalent circle diameter of less than 0.2 μm (first pores) and pores with an equivalent circle diameter of 0.2 μm or more (second pores) was measured in three rectangular measurement fields of 24.9 μm × 18.8 μm. The specific measurement method is described in Embodiment 2, so that explanation will not be repeated. The number of the most numerous pores in each of the three measurement fields is shown in the "Less than 0.2 μm (pores)" and "0.2 μm or more (pores)" columns of "Number of Pores" under "Rotating Tool" in Table 2.

[0121] ≪Composition of cemented carbide≫ In all samples, it was confirmed that the composition of the cemented carbide in the rotary tool was identical to the composition of the cemented carbide material before machining into the rotary tool.

[0122] <Cutting Test> ≪Drill≫ Commercial semiconductor printed circuit boards were drilled using small-diameter drills from samples 1 to 8, sample 1-1, and sample 1-2. The drilling conditions were a rotation speed of 200 krpm and a feed rate of 1.0 m / min. Drilling was performed with five drills. For each drill, the hole position accuracy was measured every 100 holes drilled. The number of drilled holes when the average value + 3σ of the five drills exceeded 70 μm was measured. The results are shown in the "Tool Life" column under "Rotating Tool" in Table 2. A higher number of drilled holes indicates a longer tool life.

[0123] End mill Side machining was performed on S45C block material using the end mills of Sample 9 and Samples 1-3. The machining conditions were a rotational speed of 10krpm, a feed rate of 400mm / min, a depth of cut (axial) of ap 1.5mm, and a depth of cut (radial) of ae 0.2mm. Machining was performed with three end mills. The cutting length was measured when the flank wear reached 0.2mm. The average cutting length for the three end mills is shown in the "Tool Life" column of "Rotational Tool" in Table 2. A longer cutting length indicates a longer tool life.

[0124] [Table 2]

[0125] <Consideration> The small-diameter drills in Samples 1 to 8 correspond to the Examples, while the small-diameter drills in Samples 1-1 and 1-2 correspond to the Comparative Examples. It was confirmed that the small-diameter drills in Samples 1 to 8 (Examples) had a longer tool life compared to the small-diameter drills in Samples 1-1 and 1-2 (Comparative Examples).

[0126] In sample 1-1, the small-diameter drill broke before drilling 1000 holes. In sample 1-2, localized wear progression was observed in the small-diameter drill, starting from small chipping.

[0127] The end mill in sample 9 corresponds to the example, while the end mills in samples 1-3 correspond to the comparative examples. It was confirmed that the end mill in sample 9 (example) had a longer tool life compared to the end mills in samples 1-3 (comparative examples).

[0128] As described above, embodiments and examples of this disclosure have been explained, but it is also intended from the outset that the configurations of each of the above embodiments and examples may be combined as appropriate or modified in various ways. The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the meaning and scope of the claims are intended to be included. [Explanation of symbols]

[0129] 1. Carbide alloy material 2 pore 3 Rotary Tools 4 grooves P1 Rotation axis P2 cutting edge

Claims

1. A cemented carbide material for rotary tools, The cemented carbide material contains 85.0% to 95.0% by volume of tungsten carbide particles and 5.0% to 15.0% by volume of a binder phase. When a binarized image of a first image obtained by photographing the central part of the cross-section of the cemented carbide material at a scanning electron microscope at an observation magnification of 5000x is superimposed with an elemental mapping image obtained by analyzing the same region as the first image using energy-dispersive X-ray spectroscopy, if a region shown in black in the binarized image where no elements are present in the elemental mapping image is identified as a pore, In one rectangular measurement field of 24.9 μm × 18.8 μm provided in the image after the binarization process, the number of pores with an equivalent circle diameter of less than 0.2 μm is 0 or more and 9 or less. In the aforementioned measurement field, no pores with an equivalent diameter of 0.2 μm or more exist. The average particle size of the tungsten carbide particles is 0.40 μm or more and 1.00 μm or less. The cemented carbide material for rotary tools has an average particle size of tungsten carbide particles, with a median diameter D50 of the equivalent diameter of the equiarea circle of the tungsten carbide particles.

2. The cemented carbide material for rotary tools according to claim 1, wherein the average particle size of the tungsten carbide particles is 0.40 μm or more and less than 0.80 μm.

3. A rotary tool made of cemented carbide, The cemented carbide alloy contains 85.0% to 95.0% by volume of tungsten carbide particles and 5.0% to 15.0% by volume of a binder phase. When a binarized image of a first image obtained by photographing a cross-section of the cemented carbide alloy with respect to the rotation axis P1 of the rotary tool using a scanning electron microscope at an observation magnification of 5000x is superimposed with an elemental mapping image obtained by analyzing the same region as the first image using energy-dispersive X-ray spectroscopy, if a region shown in black in the binarized image where no elements are present in the elemental mapping image is identified as a pore, In each of the first, second, and third measurement fields provided in the image after the binarization process, the number of pores with an equivalent circle diameter of less than 0.2 μm is 0 to 9. In each of the first, second, and third measurement fields, there are no pores with an equivalent circle diameter of 0.2 μm or more. Each of the first, second, and third measurement fields is a rectangle measuring 24.9 μm × 18.8 μm. The first measurement field is provided on the cross-section of the cemented carbide, with the rotation axis P1 of the rotary tool as the normal, so as to include the rotation axis P1. The second measurement field is provided on the cross-section of the cemented carbide, on the line segment L connecting the rotation axis P1 and the cutting edge P2 of the rotary tool, and includes a position P3 at a distance from the rotation axis P1 that is 1 / 3 of the length L1 of the line segment L. The third measurement field is provided on the cross-section of the cemented carbide, on the line segment L, and includes a position P4 whose distance from the rotation axis P1 is 2 / 3 of the length L1 of the line segment L. The average particle size of the tungsten carbide particles is 0.40 μm or more and 1.00 μm or less. A rotary tool in which the average particle size of the tungsten carbide particles is the median diameter D50 of the equivalent diameter of the equiarea circle of the tungsten carbide particles.

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