Cemented carbide and a cutting tool using the same

Abstract

A cemented carbide, which is a cemented carbide having a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide contains the tungsten carbide particles and the binder phase in a total amount of 80% by volume or more, the cemented carbide contains the binder phase in an amount of 0.1% by volume or more and 20% by volume or less, the cemented carbide contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum, the cemented carbide contains the first element in a total amount of 0.01 atomic % or more and 10.0 atomic % or less, the binder phase contains 50% by mass or more of cobalt, and in a first interface region between the tungsten carbide particles adjacent to each other, the first element does not segregate.

Description

Technical Field

[0001] The present disclosure relates to cemented carbide and a cutting tool using the cemented carbide. Background Art

[0002] Heretofore, cemented carbide having tungsten carbide (WC) particles and a binder phase mainly composed of cobalt or the like has been used as a raw material for cutting tools (Patent Document 1, Patent Document 2).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-098393

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2021-110010 Summary of the Invention

[0007] The cemented carbide of the present disclosure is a cemented carbide having a plurality of tungsten carbide particles and a binder phase, wherein

[0008] the cemented carbide contains the tungsten carbide particles and the binder phase in a total amount of 80% by volume or more,

[0009] the cemented carbide contains the binder phase in an amount of 0.1% by volume or more and 20% by volume or less,

[0010] the cemented carbide contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum,

[0011] the cemented carbide contains the first element in a total amount of 0.01 atomic % or more and 10.0 atomic % or less,

[0012] the binder phase contains 50% by mass or more of cobalt,

[0013] in a first interface region between adjacent tungsten carbide particles, the first element does not segregate. Brief Description of the Drawings

[0014] Figure 1 is a schematic cross-sectional view of the cemented carbide according to Embodiment 1.

[0015] Figure 2 is a diagram for explaining a method for confirming that the first element does not segregate in the first interface region, showing a first curve graph.

[0016] Figure 3 is a schematic view of the cutting tool according to Embodiment 2. Detailed Description of the Invention

[0017] [Problems to be Solved by the Present Disclosure]

[0018] In recent years, with the expansion of 5G (the fifth-generation mobile communication system), the high-capacity of information has been continuously developing, and further heat resistance is required for printed circuit boards. In order to improve the heat resistance of printed circuit boards, technologies for improving the heat resistance of resins and glass fillers constituting the printed circuit boards have been developed. On the other hand, the difficulty of cutting such printed circuit boards has increased. In the case of materials for cutting tools used for opening holes in such printed circuit boards, cemented carbides that can achieve long tool life are also required.

[0019] Therefore, an object of the present disclosure is to provide a cemented carbide that can achieve long tool life, especially when used as a material for a cutting tool for opening holes in a printed circuit board, and a cutting tool including the cemented carbide.

[0020] [Effects of the Present Disclosure]

[0021] According to the present disclosure, it is possible to provide a cemented carbide that can achieve long tool life, especially when used as a material for a cutting tool for opening holes in a printed circuit board, and a cutting tool including the cemented carbide.

[0022] [Description of Embodiments of the Present Disclosure]

[0023] First, embodiments of the present disclosure will be listed and described.

[0024] (1) The cemented carbide of the present disclosure is a cemented carbide including a plurality of tungsten carbide particles and a binder phase, wherein,

[0025] the cemented carbide includes the tungsten carbide particles and the binder phase in a total amount of 80% by volume or more,

[0026] the cemented carbide includes the binder phase in an amount of 0.1% by volume or more and 20% by volume or less,

[0027] the cemented carbide includes at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum,

[0028] the cemented carbide includes the first element in a total amount of 0.01 atomic % or more and 10.0 atomic % or less,

[0029] the binder phase includes 50% by mass or more of cobalt,

[0030] in a first interface region between adjacent tungsten carbide particles, the first element does not segregate.

[0031] According to the present disclosure, there can be provided a cemented carbide capable of achieving a long tool life especially in the case of being used as a material for a cutting tool for opening holes in a printed circuit board, and a cutting tool including the cemented carbide.

[0032] (2) Alternatively, in the above (1), the total content ratio of the first elements in the cemented carbide is 0.1 atomic % or more and 5 atomic % or less. Thereby, the tool life is further improved.

[0033] (3) Alternatively, in the above (1) or (2), the cemented carbide contains 18% by volume or less of the binder phase. Thereby, the tool life is further improved.

[0034] (4) Alternatively, in any one of the above (1) to (3), when the adjacent tungsten carbide particles are defined as a first tungsten carbide particle and a second tungsten carbide particle, the first tungsten carbide particle and the second tungsten carbide particle form a first interface,

[0035] The first interface region is composed of a first A region with a distance of 1.2 nm or less from the first interface toward the first tungsten carbide particle side and a first B region with a distance of 1.2 nm or less from the first interface toward the second tungsten carbide particle side.

[0036] (5) The cutting tool of the present disclosure is a cutting tool including a cutting edge composed of the cemented carbide according to any one of the above (1) to (4).

[0037] The cutting tool of the present disclosure can also have a long tool life especially when it is used for opening holes in a printed circuit board.

[0038] [Details of Embodiments of the Present Disclosure]

[0039] Hereinafter, specific examples of the cemented carbide and the cutting tool of the present disclosure will be described with reference to the drawings. In the drawings of the present disclosure, the same reference numerals denote the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, depth, etc. are appropriately changed for the clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0040] In the present disclosure, an expression in the form of "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when there is no unit notation for A and only a unit is noted for B, the unit of A is the same as the unit of B.

[0041] In the present disclosure, when representing a compound or the like by a chemical formula, when the atomic ratio is not particularly limited, it includes all conventionally known atomic ratios and is not necessarily limited to the atomic ratio within the stoichiometric range.

[0042] In the present disclosure, when one or more numerical values are respectively described as the lower limit and the upper limit of a numerical range, combinations of any one of the numerical values described as the lower limit and any one of the numerical values described as the upper limit are also disclosed. For example, when a1 or more, b1 or more, and c1 or more are described as the lower limit, and a2 or less, b2 or less, and c2 or less are described as the upper limit, a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, and c1 or more and c2 or less are disclosed.

[0043] [Embodiment 1: Cemented carbide]

[0044] The cemented carbide according to one embodiment of the present disclosure (hereinafter, also referred to as "Embodiment 1") is a cemented carbide including a plurality of tungsten carbide particles and a binder phase, wherein

[0045] the cemented carbide contains the tungsten carbide particles and the binder phase in a total amount of 80% by volume or more,

[0046] the cemented carbide contains the binder phase in an amount of 0.1% by volume or more and 20% by volume or less,

[0047] the cemented carbide contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum,

[0048] the cemented carbide contains the first element in a total amount of 0.01 atomic% or more and 10.0 atomic% or less,

[0049] the binder phase contains 50% by mass or more of cobalt,

[0050] in the first interface region between adjacent tungsten carbide particles, the first element does not segregate.

[0051] In particular, when the cemented carbide of Embodiment 1 is used as a material for a cutting tool for opening holes in a printed circuit board, a cemented carbide capable of achieving a long tool life and a cutting tool including the cemented carbide can be provided. The reason is not clear yet, but it is speculated as follows.

[0052] The cemented carbide of Embodiment 1 includes a plurality of tungsten carbide particles (hereinafter, also referred to as "WC particles") and a binder phase, and the total content of the WC particles and the binder phase in the cemented carbide is 80% by volume or more. Thus, the cemented carbide has high hardness and high strength, and a cutting tool using the cemented carbide can have excellent wear resistance and fracture resistance.

[0053] The cemented carbide of Embodiment 1 contains a binder phase of 0.1% by volume or more and 20% by volume or less, and the binder phase contains 50% by mass or more of cobalt. Thus, the cemented carbide has high hardness and high strength, and a cutting tool using the cemented carbide can have excellent wear resistance and fracture resistance.

[0054] The cemented carbide of Embodiment 1 contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum, and the cemented carbide contains a total of 0.01 atomic % or more and 10.0 atomic % or less of the first element. Thus, the heat resistance and reactivity of the cemented carbide are improved.

[0055] In the cemented carbide of Embodiment 1, in the first interface region between adjacent tungsten carbide particles, the first element does not segregate. Thus, in the cemented carbide, the interfacial strength between tungsten carbide particles is increased, and the detachment of tungsten carbide particles is suppressed during cutting. Therefore, a cutting tool using the cemented carbide as a material can have a long tool life. Further, the hole position accuracy of the cutting tool is also improved.

[0056] <Composition of Cemented Carbide>

[0057] As Figure 1 shown, the cemented carbide 3 of Embodiment 1 includes a plurality of tungsten carbide particles 1 (hereinafter, also referred to as "WC particles") and a binder phase 2, and the total content rate of the WC particles and the binder phase of the cemented carbide 3 is 80% by volume or more. The lower limit of the total content rate of the WC particles and the binder phase of the cemented carbide may also be 82% by volume or more, may be 84% by volume or more, may be 85% by volume or more, or may be 86% by volume or more. The upper limit of the total content rate of the WC particles and the binder phase of the cemented carbide may be 100% by volume or less. From a manufacturing perspective, the upper limit of the total content rate of the WC particles and the binder phase of the cemented carbide may also be 99% by volume or less, or may be 98% by volume or less. In the cemented carbide, the total content rate of the WC particles and the binder phase of the cemented carbide may be 80% by volume or more and 100% by volume or less, may be 82% by volume or more and 100% by volume or less, or may be 84% by volume or more and 100% by volume or less.

[0058] The cemented carbide of Embodiment 1 may be composed of a plurality of tungsten carbide particles and a binder phase. Based on the tungsten carbide particles and the binder phase, the cemented carbide of the present embodiment may further contain other phases. Examples of the other phases include carbides, nitrides, or carbonitrides containing at least one first element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo). The composition of the other phase is, for example, TiCN, TaC, NbC, ZrC, HfC, Mo2 C.

[0059] The cemented carbide of Embodiment 1 may be composed of tungsten carbide particles, a binder phase, and other phases. The content ratio of the other phases of the cemented carbide is allowed within a range that does not impair the effects of the present disclosure. For example, the content ratio of the other phases of the cemented carbide may be greater than 0% by volume and 20% by volume or less, may be greater than 0% by volume and 18% by volume or less, or may be greater than 0% by volume and 16% by volume or less. In this case, the total content ratio of the WC particles and the binder phase of the cemented carbide may be 80% by volume or more and less than 100% by volume, may be 82% by volume or more and less than 100% by volume, or may be 84% by volume or more and less than 100% by volume.

[0060] The cemented carbide of Embodiment 1 may contain impurities. Examples of such impurities include iron (Fe), calcium (Ca), silicon (Si), and sulfur (S). The content ratio of the impurities of the cemented carbide is allowed within a range that does not impair the effects of the present disclosure. For example, the content ratio of the impurities of the cemented carbide is preferably 0% by mass or more and less than 0.1% by mass. The content ratio of the impurities of the cemented carbide is measured by ICP emission analysis (Inductively Coupled Plasma Emission Spectroscopy (measurement device: Shimadzu Corporation "ICPS-8100" (trademark))).

[0061] The lower limit of the content ratio of the tungsten carbide particles of the cemented carbide of Embodiment 1 may be 60% by volume or more, may be 62% by volume or more, may be 64% by volume or more, or may be 68% by volume or more. The upper limit of the content ratio of the tungsten carbide particles of the cemented carbide may be 99.9% by volume or less, may be 99.2% by volume or less, may be 99% by volume or less, may be 98% by volume or less, may be 97% by volume or less, or may be 90% by volume or less. The content ratio of the tungsten carbide particles of the cemented carbide may be 60% by volume or more and 99.9% by volume or less, may be 60% by volume or more and 99.2% by volume or less, may be 64% by volume or more and 97% by volume or less, or may be 68% by volume or more and 90% by volume or less.

[0062] The cemented carbide of Embodiment 1 contains a binder phase of 0.1% by volume or more and 20% by volume or less. From the viewpoint of improving toughness, the lower limit of the content rate of the binder phase of the cemented carbide is 0.1% by volume or more, and may be 0.4% by volume or more, may be 1% by volume or more, may be 1.5% by volume or more, may be 2% by volume or more, may be 3% by volume or more, may be 8% by volume or more. From the viewpoint of improving hardness, the upper limit of the content rate of the binder phase of the cemented carbide is 20% by volume or less, and may be 18% by volume or less, may be 16% by volume or less, may be 15% by volume or less. The content rate of the binder phase of the cemented carbide may be 0.1% by volume or more and 18% by volume or less, may be 0.4% by volume or more and 18% by volume or less, may be 1.5% by volume or more and 16% by volume or less, may be 8% by volume or more and 14% by volume or less. If the content rate of the binder phase of the cemented carbide is 18% by volume or less, the hardness of the cemented carbide is further improved, the wear resistance is further improved, and thus the tool life of the cutting tool using the cemented carbide as a material is further improved. The Rockwell hardness (HRC) of the cemented carbide of the present embodiment may be, for example, 90 or more and 95 or less, or may be 91 or more and 95 or less.

[0063] The method for measuring the content rate (volume %) of tungsten carbide particles and the content rate (volume %) of the binder phase of the cemented carbide is as described below.

[0064] (A1) Cut out an arbitrary position of the cemented carbide to expose the cross section. Mirror-finish this cross section using a cross-section polishing machine (manufactured by JEOL Ltd.).

[0065] (B1) Use scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) to analyze the mirror-finished surface of the cemented carbide (device: Gemini450 (trademark) manufactured by Carl Zeiss AG), and determine the elements contained in the cemented carbide.

[0066] (C1) Use a scanning electron microscope (SEM) to photograph the mirror-finished surface of the cemented carbide to obtain a backscattered electron image. The imaging area of the photographed image is set to the central part of the cross section of the cemented carbide, that is, the position that does not include parts with significantly different shapes from the massive part such as near the surface of the cemented carbide (the entire imaging area is the position of the massive part of the cemented carbide). The magnification is 5000 times. The measurement conditions are an acceleration voltage of 3 kV, a current value of 2 nA, and a working distance (WD) of 5 mm.

[0067] (D1) For the shooting area of the above (C1), use an energy-dispersive X-ray analysis device (SEM-EDX) attached to an SEM to analyze it, determine the distribution of the elements determined in the above (B1) in this shooting area, and obtain an elemental mapping image.

[0068] (E1) Take the backscattered electron image obtained in the above (C1) into a computer and perform binarization processing using image analysis software (OpenCV, SciPy). In the binarized image, tungsten carbide particles are represented in white, and the binder phase is represented in gray to black. In addition, since the binarization threshold varies according to the contrast, it is set for each image.

[0069] (F1) By overlapping the elemental mapping image obtained in the above (D1) with the binarized image obtained in the above (E1), determine the existence regions of tungsten carbide particles and the binder phase respectively on this binarized image. Specifically, the region that is represented in white in the binarized image and where tungsten (W) and carbon (C) exist in the elemental mapping image corresponds to the existence region of tungsten carbide particles. The region that is represented in gray to black in the binarized image and where cobalt (Co) exists in the elemental mapping image corresponds to the existence region of the binder phase.

[0070] (G1) Set a measurement field of view of a rectangle of 24.9 μm × 18.8 μm in the above binarized image. Using the above image analysis software, measure the area percentages of tungsten carbide particles and the binder phase respectively with the total area of this measurement field of view as the denominator.

[0071] (H1) Perform the measurement in the above (G1) in five different and non-overlapping measurement fields of view. In this specification, the average of the area percentages of tungsten carbide particles in the five measurement fields of view corresponds to the content rate (volume %) of tungsten carbide particles in the cemented carbide, and the average of the area percentages of the binder phase in the five measurement fields of view corresponds to the content rate (volume %) of the binder phase in the cemented carbide.

[0072] In the case where the cemented carbide further contains other phases on the basis of WC particles and the binder phase, the content rate of other phases of the cemented carbide can be obtained by subtracting the content rate (volume %) of tungsten carbide particles and the content rate (volume %) of the binder phase measured according to the above steps from the whole cemented carbide (100 volume %).

[0073] It was confirmed that as long as it is within the range measured by the applicant and as long as the measurement is carried out on the same specimen, even if the cut-out position of the cross-section of the cemented carbide, the imaging area described in the above (C1), and the measurement field of view described in the above (G1) are arbitrarily set, and the measurement of the content rate of tungsten carbide particles and the content rate of the binder phase of the cemented carbide is carried out multiple times according to the above steps, the deviation of the measurement results is very small, and even if the cut-out position of the cross-section of the cemented carbide, the imaging area, and the measurement field of view are arbitrarily set, the results will not change randomly.

[0074] <Tungsten carbide particles>

[0075] In Embodiment 1, the tungsten carbide particles include at least any one of "pure WC particles (including WC that completely does not contain impurity elements and WC with an impurity element content less than the detection limit)" and "WC particles that intentionally or inevitably contain impurity elements inside within the range that does not impair the effects of the present disclosure". The content rate of impurities in the tungsten carbide particles (when there are two or more elements constituting the impurities, their total concentration) is less than 0.1% by mass. The content rate of impurity elements in the tungsten carbide particles is measured by ICP emission analysis.

[0076] In Embodiment 1, the average particle size of the tungsten carbide particles is not particularly limited. The average particle size of the tungsten carbide particles can be, for example, 0.1 μm or more and 3.5 μm or less. It was confirmed that the cemented carbide of Embodiment 1 can have a long tool life regardless of the average particle size of the tungsten carbide particles.

[0077] <Binder phase>

[0078] In Embodiment 1, the binder phase contains 50% by mass or more of cobalt. Thereby, excellent toughness can be imparted to the cemented carbide. The lower limit of the cobalt content rate in the binder phase can be 52% by mass or more, can be 60% by mass or more, can be 66% by mass or more, or can be 70% by mass or more. The upper limit of the cobalt content rate in the binder phase can be 100% by mass or less, can be less than 100% by mass, can be 95% by mass or less, can be 93% by mass or less, or can be 90% by mass or less. The cobalt content rate in the binder phase can be 50% by mass or more and less than 100% by mass, can be 60% by mass or more and 95% by mass or less, or can be 70% by mass or more and 90% by mass or less.

[0079] The method for measuring the cobalt content rate of the binder phase is as described below. By the same method as (A1) to (F1) of the method for measuring the tungsten carbide particle content rate, the binder phase content rate, and the hard phase particle content rate of the above cemented carbide, the existence region of the binder phase is determined on the binarized image. For the existence region of the binder phase, SEM-EDX is used for analysis to measure the cobalt content rate of the binder phase.

[0080] The following was confirmed: As long as it is within the range measured by the applicant and as long as the measurement is performed on the same specimen, even if the cut-out position of the cross-section of the cemented carbide and the shooting region described in (C1) above are arbitrarily set, and the measurement of the cobalt content rate of the binder phase is performed multiple times according to the above steps, the deviation of the measurement results is very small. Even if the cut-out position of the cross-section of the cemented carbide and the shooting region are arbitrarily set, the results will not change randomly.

[0081] In Embodiment 1, the binder phase may further contain at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum on the basis of cobalt. On the basis of cobalt and the first element, the binder phase may further contain at least one second element selected from the group consisting of nickel (Ni), chromium (Cr), iron (Fe), aluminum (Al), ruthenium (Ru), and rhenium (Re). The binder phase may be composed of cobalt and the first element. The binder phase may be composed of cobalt, the first element, and the second element. The binder phase may be composed of cobalt, the first element, the second element, and inevitable impurities. Examples of such inevitable impurities include manganese (Mn), magnesium (Mg), calcium (Ca), sulfur (S), etc.

[0082] <First element>

[0083] The cemented carbide of Embodiment 1 contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum, and the cemented carbide contains a total of 0.01 atomic% or more and 10 atomic% or less of the first element. From the viewpoint of improving the tool life, the lower limit of the content rate of the first element of the cemented carbide is 0.01 atomic% or more, and may be 0.03 atomic% or more, may be 0.1 atomic% or more, may be 0.8 atomic% or more, may be 1 atomic% or more, may be 2 atomic% or more, may be 2.3 atomic% or more. From the viewpoint of maintaining strength, the upper limit of the content rate of the first element of the cemented carbide is 10.0 atomic% or less, and may be 9 atomic% or less, may be 8.2 atomic% or less, may be 8 atomic% or less, may be 7.7 atomic% or less, may be 5 atomic% or less. The content rate of the first element of the cemented carbide may be 0.1 atomic% or more and 5 atomic% or less.

[0084] The content ratio of the first element of the cemented carbide based on the number of atoms is measured by ICP (Inductively Coupled Plasma) emission analysis (measurement device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0085] In the cemented carbide of Embodiment 1, in the first interface region between adjacent tungsten carbide particles, the first element does not segregate. As a result, the interfacial strength between tungsten carbide particles is improved, and the cemented carbide can have excellent abrasion resistance and fracture resistance.

[0086] In the present disclosure, Figure 2 A method for confirming that the first element does not segregate in the first interface region between adjacent tungsten carbide particles of the cemented carbide will be described.

[0087] Using an argon ion milling machine ("Cryo Ion Milling IB-09060BCIS" (trademark) manufactured by JEOL Ltd.), the cemented carbide is thinned to a thickness of 30 to 100 nm under the conditions of an acceleration voltage of 6 kV and a final processing voltage of 2 kV to produce a measurement sample. Then, using TEM (Transmission Electron Microscopy) ("JEM-ARM300F2" (trademark) manufactured by JEOL Ltd.), the measurement sample is observed at a magnification of 200,000 times under the condition of an acceleration voltage of 200 V, thereby obtaining a first image (not shown).

[0088] In the first image, the tungsten carbide particles are observed as white regions, the binder phase is observed as black regions, and the interfaces are observed as black regions. In the first image, an interface between tungsten carbide particles is arbitrarily selected. In the present disclosure, the adjacent tungsten carbide particles forming the interface are also referred to as the first tungsten carbide particle and the second tungsten carbide particle.

[0089] Next, position it in such a way that the selected interface passes near the center of the image, adjust the observation magnification so that the field of view size is 5 nm × 5 nm for observation, and thereby obtain a second image (not shown). In the second image, confirm the elongation direction of the interface. Perform line analysis in the direction perpendicular to this elongation direction and from the first tungsten carbide particle toward the second tungsten carbide particle to obtain a graph (hereinafter, also referred to as the first graph) showing the distribution of cobalt, tungsten, and the first element measured. When the cemented carbide contains two or more first elements, measure the distribution of each element. Here, the direction perpendicular to the elongation direction of the interface refers to the direction of a straight line that intersects at an angle of 90° ± 5° with respect to the tangent line of the elongation direction. The measurement conditions for obtaining the second image are an acceleration voltage of 200 kV, a camera length of 10 cm, a pixel number of 128 × 128 pixel, and a dwell time of 0.02 to 3 s / pixel.

[0090] Figure 2 is an example of the first graph. In Figure 2 , the horizontal axis (X-axis) represents the distance (nm) from the measurement start point, and the vertical axis (Y-axis) represents the NET intensity (unitless). In the cemented carbide shown in Figure 2 , the first element is tantalum (Ta).

[0091] In the first graph, determine the peak position of cobalt. In the present disclosure, the peak position of cobalt is denoted as the first interface. The first interface is formed by the first tungsten carbide particle and the second tungsten carbide particle adjacent to each other. In the first graph of Figure 2 , the position of the first interface is 4.15 nm on the X-axis.

[0092] In the first graph, determine a first A region within a distance of 1.20 nm or less from the first interface toward the first tungsten carbide particle side and a first B region within a distance of 1.20 nm or less from the first interface toward the second tungsten carbide particle side. In the present disclosure, the region composed of the first A region and the first B region is the first interface region. In the first graph of Figure 2 , the position of the first interface region is 2.95 to 5.35 nm on the X-axis.

[0093] In the first graph, determine a second A region within a distance of 1.50 nm or more and 3.50 nm or less from the first interface toward the first tungsten carbide particle side and a second B region within a distance of 1.50 nm or more and 3.50 nm or less from the first interface toward the second tungsten carbide particle side. In the first graph of Figure 2 , the position of the second A region is 0.65 to 2.65 nm on the X-axis, and the position of the second B region is 5.65 to 7.65 nm on the X-axis.

[0094] Based on the first curve graph, the average B of the NET intensity in the baseline region composed of the 2A region and the 2B region of the first element is calculated. In the first curve graph, the maximum value A of the NET intensity in the first interface region of the first element is measured. When the ratio A / B of the maximum value A to the average B is less than 3, it is confirmed that no segregation of the first element occurs in the first interface region between adjacent tungsten carbide particles in the cemented carbide. In Figure 2 In the first curve graph of Figure 2 , the average B of the NET intensity in the baseline region composed of the 2A region and the 2B region of tantalum (the first element) is 78.7 (the average of the NET intensity in the 2A region is 97.6, and the average of the NET intensity in the 2B region is 59.7), and the maximum value A of the NET intensity in the first interface region of tantalum (the first element) is 112.6. In

[0095] In the cemented carbide, five non-overlapping first images of the fields of view are arbitrarily obtained, and the above analysis is repeatedly performed based on each first image. When no segregation of the first element is confirmed in the first interface region in four or more fields of view, it is determined that no segregation of the first element occurs in the first interface region between adjacent tungsten carbide particles in the cemented carbide.

[0096] The following is confirmed: As long as it is within the range measured by the applicant and as long as the measurement is performed on the same specimen, even if the cut-out position of the cross-section of the cemented carbide is arbitrarily set, the first image is arbitrarily obtained on the cross-section, and according to the above steps, the region of the line analysis is changed and the presence or absence of segregation of the first element in the first interface region is confirmed multiple times, it is also confirmed that there is almost no deviation in the result of the presence or absence of segregation of the first element in the first interface region. Therefore, for the method of confirming the segregation of the first element in the cemented carbide, as long as no segregation of the first element is confirmed in the first interface region, it can be inferred that the interfacial strength between the tungsten carbide particles in the cemented carbide is improved.

[0097] In the cemented carbide of the present disclosure, the first element may be present in the above other phases and cobalt.

[0098] <Manufacturing method of cemented carbide>

[0099] The cemented carbide of the present embodiment can be manufactured by successively performing a raw material powder preparation process, a mixing process, a molding process, a sintering process, and a cooling process. Hereinafter, each process will be described.

[0100] <Preparation process>

[0101] The preparation process is a process of preparing raw material powders that constitute the raw materials of cemented carbide. As the raw material powders, tungsten carbide powder (hereinafter, also referred to as "WC powder"), cobalt (Co) powder, and powders containing a first metal element can be cited. As the powders containing a first metal element, titanium carbonitride (TiCN) powder, tantalum carbide (TaC) powder, niobium carbide (NbC) powder, zirconium carbide (ZrC) powder, hafnium carbide (HfC) powder, molybdenum carbide (Mo 2 C) powder, etc. can be cited. These raw material powders can use commercially available products. The average particle size of these raw material powders is not particularly limited, and for example, it can be set to 0.1 to 3.0 μm. The average particle size of the raw material powders refers to the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method. This average particle size is measured using "Sub-Sieve Sizer model 95" (trademark) manufactured by Fisher Scientific Company. The particle size distribution of the above WC powder is measured using a particle size distribution measuring device (trade name: MT3300 EX) manufactured by Microtrac Company.

[0102] <Mixing process>

[0103] The mixing process is a process of mixing each raw material powder prepared in the preparation process in a predetermined ratio. Through the mixing process, a mixed powder formed by mixing each raw material powder is obtained. The mixing ratio of each raw material powder is appropriately adjusted according to the composition of the target cemented carbide.

[0104] The mixing of each raw material powder can use conventionally known mixing methods such as a grinder, a ball mill, and a bead mill. The mixing conditions can also use conventionally known conditions. For example, the mixing time can be set to 2 hours or more and 20 hours or less, for example.

[0105] After the mixing process, granulation of the mixed powder can be performed as needed. By granulating the mixed powder, it is easy to fill the mixed powder into the die head or die in the subsequent forming process. Granulation can apply known granulation methods, and for example, commercially available granulators such as a spray dryer can be used.

[0106] <Forming process>

[0107] The forming process is a process of forming the mixed powder obtained in the mixing process into a shape for a cutting tool (for example, a round bar shape) to obtain a formed body. The forming method and forming conditions in the forming process can adopt general methods and conditions and are not particularly limited.

[0108] <Sintering process>

[0109] The sintering process is a process of sintering a green compact obtained through a forming process by sintering HIP (Hot Isostatic Pressing) (SINTER-HIP, sintering hot isostatic pressing) treatment capable of simultaneously sintering and pressurizing to obtain a cemented carbide intermediate body.

[0110] The sintering process may include a first sintering process and a second sintering process. First, in the first sintering process, it is maintained at a sintering temperature of 1300 °C and a sintering pressure of 7 MPa for 240 minutes. Then, in the second sintering process, it is possible to raise the temperature to 1360 °C while maintaining the sintering pressure of 7 MPa, and maintain it at 1360 °C for 15 minutes to obtain a cemented carbide intermediate body.

[0111] The atmosphere during sintering is not particularly limited. For example, N 2 gas atmosphere or an inert gas atmosphere such as Ar can be used.

[0112] <Cooling process>

[0113] The cooling process is a process of cooling the cemented carbide intermediate body after the sintering process. For example, the above-mentioned cemented carbide intermediate body can be quenched in Ar gas under the condition of a pressure of 100 to 400 MPaG to obtain cemented carbide.

[0114] <Features of the manufacturing method of the cemented carbide of the present embodiment>

[0115] The sintering temperature of 1300 °C in the first sintering process is lower than the sintering temperature of general cemented carbide. Further, the sintering time of 240 minutes in the first sintering process is longer than the sintering time of 30 to 60 minutes of general cemented carbide. Thus, it can be speculated that atomic diffusion and rearrangement occur during sintering, and the cemented carbide of the present disclosure in which the first element does not segregate in the first interface region between adjacent tungsten carbide particles can be obtained. As a result of in-depth research by the inventors of the present invention, it was newly discovered that the cemented carbide of the present disclosure can be achieved through such sintering conditions. In addition, the sintering temperature and sintering time of the first sintering process are not adopted by those skilled in the art due to reduced production efficiency.

[0116] [Embodiment 2: Cutting tool]

[0117] The cutting tool of the present embodiment includes a cutting edge made of the cemented carbide of Embodiment 1. In the present disclosure, the cutting edge refers to the part participating in cutting. More specifically, the cutting edge refers to the region surrounded by the cutting edge ridge line and a virtual plane with a distance of 2 mm from the cutting edge ridge line toward the cemented carbide side.

[0118] As a cutting tool, for example, it can be exemplified as a cutting tool, a drill bit, an end mill, an indexable cutting insert for milling, an indexable cutting insert for turning, a metalworking saw, a gear cutting tool, a reamer or a tap, etc. In particular, as Figure 3 shown, in the case of the small-diameter drill bit for printed circuit board processing, the cutting tool 10 of the present embodiment can exhibit excellent effects. Figure 3 The tip 11 of the cutting tool 10 shown is made of the cemented carbide of Embodiment 1.

[0119] The cemented carbide of the present embodiment can form the whole of these tools or a part thereof. Here, "forming a part" means a method of brazing the cemented carbide of the present embodiment to a predetermined position of an arbitrary base material to form a tip portion, etc.

[0120] The cutting tool of the present embodiment may further include a hard film that covers at least a part of the surface of a base material made of cemented carbide. As the hard film, for example, diamond-like carbon or diamond can be used.

[0121] The cutting tool of the present embodiment can be obtained by forming the cemented carbide of Embodiment 1 into a desired shape.

[0122] Examples

[0123] The present embodiment will be further specifically described by way of examples. However, the present embodiment is not limited to these examples.

[0124] [Production of Cemented Carbide]

[0125] The cemented carbide of each specimen was produced according to the following steps.

[0126] WC powder (average particle size 0.3 μm), Co powder (average particle size 1.0 μm), TiCN powder (average particle size 1.0 μm), TaC powder (average particle size 1.0 μm), NbC powder (average particle size 1.0 μm), ZrC powder (average particle size 1.0 μm), HfC powder (average particle size 1.0 μm), Mo 2 C powder (average particle size 1.0 μm) were prepared in the proportions described in the "Raw Material Powder" column of Table 1 and mixed to obtain a mixed powder. For example, in Specimen 1, WC powder, Co powder, and TiCN powder were prepared in a ratio of 81.8:11.7:6.5 by mass and mixed to obtain a mixed powder. In all specimens, mixing was carried out using a grinder for 10 hours.

[0127] Table @

[0128]

[0129] Next, a formed body in a round bar shape is produced by stamping the mixed powder. Next, the formed body is subjected to a first sintering process in Ar gas. The temperature, pressure, and time in the first sintering process are as shown in the column of "First Sintering Process" in Table 2. Next, while maintaining the pressure constant, the temperature is changed to 1360 °C and a second sintering process is carried out to obtain a cemented carbide intermediate. The holding time in the second sintering process is as shown in the column of "Second Sintering Process" in Table 2. Next, the cemented carbide intermediate is rapidly cooled in Ar gas under the condition of a pressure of 200 MPaG to obtain the cemented carbide of each sample.

[0130] Table 2

[0131]

[0132] [Manufacture of Cutting Tools]

[0133] The obtained round bar made of cemented carbide is processed to produce a drill bit for printed circuit board processing (PCB (Printed Circuit Board) drill bit) with a cutting edge diameter of .

[0134] [Evaluation of Cemented Carbide]

[0135] <Content ratio (volume %) of tungsten carbide particles and content ratio (volume %) of binder phase of cemented carbide>

[0136] The content ratio (volume %) of tungsten carbide particles and the content ratio (volume %) of the binder phase of the cemented carbide of each sample are measured. The specific measurement method is as described in Embodiment 1. The results are shown in the columns of "WC Particle Content Ratio" and "Binder Phase Content Ratio" of "Cemented Carbide" in Table 3. Further, the total of the content ratio of tungsten carbide particles and the content ratio of the binder phase of the cemented carbide is shown in the column of "WC Particle + Binder Phase Content Ratio" of "Cemented Carbide" in Table 3. In Table 3, it is confirmed that the cemented carbide with a "WC Particle + Binder Phase Content Ratio" column less than 100 volume % further contains at least one selected from the group consisting of carbides, nitrides, and carbonitrides containing a first element.

[0137] <Cobalt content ratio in binder phase>

[0138] In the cemented carbide of each sample, the cobalt content ratio in the binder phase is measured. The specific measurement method is as described in Embodiment 1. The results are shown in the column of "Co Content Ratio in Binder Phase" of "Cemented Carbide" in Table 3. It is confirmed that in all the samples, the binder phase contains, in addition to cobalt, the same first element as the first element described in the column of "First Element Type" of "Cemented Carbide" in Table 3.

[0139] <Content of the first element in the cemented carbide>

[0140] In the cemented carbide of each specimen, the type of the first element contained in the cemented carbide and the total content ratio (atomic %) of the first element of the cemented carbide were measured. The specific measurement method is as described in Embodiment 1. The results are shown in the columns of "Type of the first element" and "Content ratio of the first element" in Table 3 under "Cemented carbide". When the type of the first element is one kind, the "Content ratio of the first element" refers to the content ratio of one kind of the first element. When the type of the first element is two kinds, the "Content ratio of the first element" refers to the total content ratio of the two kinds of the first element.

[0141] <Presence or absence of segregation of the first element in the first interface region>

[0142] In the cemented carbide of each specimen, it was confirmed whether there was segregation of the first element in the first interface region between adjacent tungsten carbide particles. The specific confirmation method is as described in Embodiment 1. The results are shown in the column of "Segregation of the first element" in Table 3 under "Cemented carbide".

[0143] <Rockwell hardness>

[0144] According to "JIS Z 2245:2016 Rockwell hardness test - Test method", the Rockwell hardness (HRC) of the cemented carbide of each specimen was measured. The measurement conditions were at room temperature (23°C ± 5°C), test force 60 N, and holding time 4 s. The results are shown in the column of "Rockwell hardness" in Table 3.

[0145] [Evaluation of cutting tools]

[0146] <Cutting test>

[0147] The PCB drill bits of each specimen were used to perform hole opening processing on a commercially available in-vehicle printed circuit board, and the hole position accuracy was evaluated. The conditions for the hole opening processing were set as a rotational speed of 120 krpm, a feed rate of 2 m / min, and a pulling speed of 25 m / min. The number of hole openings (hit number) at the time point when the hole position accuracy (ave + 3σ (μm)) exceeded 70 μm was measured. The results are shown in the column of "Cutting test" in Table 3. The values in Table 3 are the values obtained by rounding off the actual number of hole openings to the nearest ten. For example, when the actual number of hole openings is 6250 times, it is recorded as 6200 times in the column of "Cutting test". The more the number of hole openings, the better the hole position accuracy of the cutting tool and the longer the tool life.

[0148] Table 3

[0149]

[0150] <Discussion>

[0151] The cemented carbides and cutting tools of Specimens 1 to 13 correspond to the examples. The cemented carbides and cutting tools of Specimens 1-1 to 1-8 correspond to the comparative examples. It was confirmed that the cutting tools of Specimens 1 to 13 (examples) were excellent in hole position accuracy and had a longer tool life than the cutting tools of Specimens 1-1 to 1-8 (comparative examples). It is presumed that this is because the cemented carbides of Specimens 1 to 13 have excellent wear resistance and fracture resistance.

[0152] As described above, the embodiments and examples of the present disclosure have been described. However, from the beginning, it has also been contemplated to appropriately combine the configurations of the above-described embodiments and examples or to make various modifications.

[0153] The embodiments and examples disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is not represented by the above-described embodiments and examples, but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0154] Explanation of Reference Numerals

[0155] 1: tungsten carbide particle; 2: binder phase; 3: cemented carbide; 10: cutting tool; 11: cutting edge.

Claims

1. A cemented carbide which is a cemented carbide having a plurality of tungsten carbide particles and a binder phase, wherein, the cemented carbide contains a total of 80% by volume or more of the tungsten carbide particles and the binder phase, the cemented carbide contains 0.1% by volume or more and 20% by volume or less of the binder phase, the cemented carbide contains at least one first element selected from the group consisting of titanium, tantalum, niobium, zirconium, hafnium, and molybdenum, the cemented carbide contains a total of 0.01 atomic% or more and 10.0 atomic% or less of the first element, the binder phase contains 50% by mass or more of cobalt, in a first interface region between the adjacent tungsten carbide particles, the first element does not segregate, when the adjacent tungsten carbide particles are a first tungsten carbide particle and a second tungsten carbide particle, the first tungsten carbide particle and the second tungsten carbide particle form a first interface, the first interface region is composed of a first A region within a distance of 1.2 nm from the first interface toward the first tungsten carbide particle side and a first B region within a distance of 1.2 nm from the first interface toward the second tungsten carbide particle side.

2. The cemented carbide according to claim 1, wherein, the total content rate of the first element in the cemented carbide is 0.1 atomic% or more and 5 atomic% or less.

3. The cemented carbide according to claim 1 or 2, wherein, the cemented carbide contains 18% by volume or less of the binder phase.

4. A cutting tool, wherein, the cutting tool has a cutting edge composed of the cemented carbide according to claim 1 or 2.

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