WO2022091343A1 - Cemented carbide and cutting tool comprising same - Google Patents

Cemented carbide and cutting tool comprising same Download PDF

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Publication number
WO2022091343A1
WO2022091343A1 PCT/JP2020/040829 JP2020040829W WO2022091343A1 WO 2022091343 A1 WO2022091343 A1 WO 2022091343A1 JP 2020040829 W JP2020040829 W JP 2020040829W WO 2022091343 A1 WO2022091343 A1 WO 2022091343A1
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WIPO (PCT)
Prior art keywords
less
cemented carbide
mass
ratio
tungsten carbide
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PCT/JP2020/040829
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French (fr)
Japanese (ja)
Inventor
隆洋 山川
和弘 広瀬
克哉 内野
剛志 山本
Original Assignee
住友電工ハードメタル株式会社
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Application filed by 住友電工ハードメタル株式会社 filed Critical 住友電工ハードメタル株式会社
Priority to JP2021521440A priority Critical patent/JP6957828B1/en
Priority to CN202080042790.3A priority patent/CN114698373A/en
Priority to PCT/JP2020/040829 priority patent/WO2022091343A1/en
Priority to TW110137325A priority patent/TW202223114A/en
Publication of WO2022091343A1 publication Critical patent/WO2022091343A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B27/00—Tools for turning or boring machines; Tools of a similar kind in general; Accessories therefor
    • B23B27/14—Cutting tools of which the bits or tips or cutting inserts are of special material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B51/00—Tools for drilling machines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23C—MILLING
    • B23C5/00—Milling-cutters
    • B23C5/16—Milling-cutters characterised by physical features other than shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23D—PLANING; SLOTTING; SHEARING; BROACHING; SAWING; FILING; SCRAPING; LIKE OPERATIONS FOR WORKING METAL BY REMOVING MATERIAL, NOT OTHERWISE PROVIDED FOR
    • B23D77/00—Reaming tools
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/05—Mixtures of metal powder with non-metallic powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties

Definitions

  • This disclosure relates to cemented carbide and cutting tools equipped with it.
  • the cemented carbide of the present disclosure is a cemented carbide comprising a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
  • the ratio of the first phase is 78 area% or more and less than 100 area%
  • the ratio of the second phase is more than 0 area% and 22 area% or less.
  • the average value of the circle-equivalent diameter is 0.5 ⁇ m or more and 1.2 ⁇ m or less.
  • the ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of 0.3 ⁇ m or less is 10% or less.
  • the ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of more than 1.8 ⁇ m is less than 2%.
  • the mass-based content of the cobalt in the cemented carbide is more than 0% by mass and 10% by mass or less.
  • the cutting tool disclosed in the present disclosure is a cutting tool equipped with a cutting edge made of the above-mentioned cemented carbide.
  • FIG. 1 is an example of an image taken by a scanning electron microscope of the cemented carbide of the present disclosure.
  • FIG. 2 is an image obtained by performing binarization processing on the captured image of FIG. 1.
  • cemented carbide capable of extending the life of a tool when used as a tool material, especially in microfabrication of a printed circuit board, and a cutting tool provided with the cemented carbide. ..
  • the cemented carbide of the present disclosure enables a long life of a tool, especially in microfabrication of a printed circuit board.
  • the cemented carbide of the present disclosure is a cemented carbide comprising a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
  • the ratio of the first phase is 78 area% or more and less than 100 area%
  • the ratio of the second phase is more than 0 area% and 22 area% or less.
  • the average value of the circle-equivalent diameter is 0.5 ⁇ m or more and 1.2 ⁇ m or less.
  • the ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of 0.3 ⁇ m or less is 10% or less.
  • the ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of more than 1.8 ⁇ m is less than 2%.
  • the mass-based content of the cobalt in the cemented carbide is more than 0% by mass and 10% by mass or less.
  • the cemented carbide disclosed in the present disclosure makes it possible to extend the life of the tool, especially in the microfabrication of printed circuit boards.
  • the ratio of the second phase is preferably 5 area% or more and 12 area% or less. According to this, the tool life is further improved.
  • the content of the cemented carbide based on the mass of chromium is preferably 0.15% by mass or more and 1.0% by mass or less. According to this, the tool life is further improved.
  • the ratio of the chromium to the cobalt is preferably 5% or more and 10% or less on a mass basis. According to this, the tool life is further improved.
  • the mass-based content of vanadium in the cemented carbide is preferably 0 ppm or more and less than 2000 ppm. According to this, the tool life is further improved.
  • the mass-based content of vanadium in the cemented carbide is preferably 0 ppm or more and less than 100 ppm. According to this, the tool life is further improved.
  • the cutting tool of the present disclosure is a cutting tool provided with a cutting edge made of the above-mentioned cemented carbide.
  • the cutting tools of the present disclosure have a long tool life.
  • the cutting tool is preferably a rotary tool for processing a printed circuit board.
  • the cutting tool of the present disclosure is suitable for microfabrication of printed circuit boards.
  • the notation in the form of "A to B” means the upper and lower limits of the range (that is, A or more and B or less), and when there is no description of the unit in A and the unit is described only in B, A.
  • the unit of and the unit of B are the same.
  • a compound or the like when represented by a chemical formula, it shall include all conventionally known atomic ratios when the atomic ratio is not particularly limited, and should not necessarily be limited to those in the stoichiometric range.
  • the ratio of the number of atoms constituting the WC includes any conventionally known atomic ratio.
  • the present inventors describe the damage form of the tool when the printed circuit board is finely machined using a tool made of a conventional fine-grained cemented carbide. investigated. As a result, it was confirmed that in the conventional fine-grained cemented carbide, the tungsten carbide particles fall off and wear with the use of the tool. Further examination of the fall-off wear confirmed that tungsten carbide particles having a particle size of 0.3 ⁇ m or less were particularly easy to fall off.
  • the present inventors can reduce the content of tungsten carbide particles having a particle size of 0.3 ⁇ m or less, which easily falls off when the tool is used, in the fine cemented carbide. I guessed it was important.
  • fine tungsten carbide particles particle size of about 0.2 ⁇ m
  • grain growth of fine tungsten carbide particles is performed in the manufacturing process. It is possible to promote it.
  • fine tungsten carbide particles when sintering fine-grained tungsten carbide particles as a raw material, it is conceivable not to add vanadium or chromium having a grain growth inhibitory effect, or to perform sintering at a high temperature.
  • coarse tungsten carbide particles having a particle size of about 2 ⁇ m or more are generated due to abnormal grain growth.
  • the coarse tungsten carbide particles are a factor that lowers the strength of the fine cemented carbide.
  • the present inventors have a raw material and a composition capable of reducing the content of tungsten carbide particles having a particle size of 0.3 ⁇ m or less in the cemented carbide and suppressing the generation of coarse tungsten carbide particles.
  • the cemented carbide of the present disclosure was completed. The details of the cemented carbide of the present disclosure and the cutting tool provided with the same will be described below.
  • the cemented carbide of the present disclosure is A cemented carbide comprising a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
  • the ratio of the first phase is 78 area% or more and less than 100 area%
  • the ratio of the second phase is more than 0 area% and 22 area% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is 10% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is less than 2%.
  • the mass-based content of cobalt in cemented carbide is greater than 0% by mass and 10% by mass or less.
  • the cemented carbide disclosed in the present disclosure makes it possible to extend the life of the tool, especially in the microfabrication of printed circuit boards. The reason for this is not clear, but it is presumed to be as described in (i) to (v) below.
  • the ratio of the first phase composed of a plurality of tungsten carbide particles is 78 area% or more and less than 100 area%, and the ratio of the second phase containing cobalt is more than 0 area% and 22 areas. % Or less. According to this, the hardness and wear resistance required for processing the printed circuit board can be exhibited, and the occurrence of variation in the tool life can be suppressed.
  • the average value of the equivalent circle diameters of the tungsten carbide particles (hereinafter, also referred to as “WC particles”) is 0.5 ⁇ m or more and 1.2 ⁇ m or less.
  • the cemented carbide When the average value of the equivalent circle diameters of the tungsten carbide particles is 0.5 ⁇ m or more, the cemented carbide is less likely to cause falling wear due to use, and the cemented carbide can have excellent wear resistance. When the average value of the equivalent circle diameters of the tungsten carbide particles is 1.2 ⁇ m or less, the cemented carbide has high hardness, can have excellent wear resistance, and has high folding resistance, and is excellent. It can have breakage resistance.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is 10% or less. According to this, the cemented carbide is less likely to cause falling-off wear due to use, and the cemented carbide can have excellent wear resistance.
  • the ratio based on the number of the tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is less than 2%. According to this, the cemented carbide has a high bending resistance and can have an excellent breaking resistance.
  • the mass-based content of cobalt in cemented carbide is more than 0% by mass and 10% by mass or less. According to this, the cemented carbide has a high hardness and can have excellent wear resistance.
  • the first phase consists of a plurality of tungsten carbide particles.
  • the tungsten carbide is not only "pure WC (including WC containing no impurity element and WC whose impurity element is below the detection limit)", but also "as long as the effect of the present disclosure is not impaired".
  • WC in which other impurity elements are intentionally or inevitably contained is also included.
  • the concentration of impurities contained in tungsten carbide (when two or more kinds of elements constituting the impurities are the total concentration thereof) is less than 0.1% by mass with respect to the total amount of the tungsten carbide and the impurities. ..
  • the content of the impurity element in the first phase is measured by ICP emission spectrometry (Inductively Coupled Plasma) Emission Spectroscopy (measuring device: Shimadzu Corporation "ICPS-8100" (trademark)).
  • the average value of the equivalent circle diameters of the tungsten carbide particles is 0.5 ⁇ m or more and 1.2 ⁇ m or less.
  • the cemented carbide is less likely to cause falling wear due to use, and the cemented carbide can have excellent wear resistance.
  • the cemented carbide has high hardness, can have excellent wear resistance, and has high folding resistance, and is excellent. It can have breakage resistance.
  • the lower limit of the average value of the equivalent circle diameters of the tungsten carbide particles is preferably 0.5 ⁇ m or more, 0.55 ⁇ m or more, and 0.60 ⁇ m or more.
  • the upper limit of the average value of the equivalent circle diameters of the tungsten carbide particles is preferably 1.2 ⁇ m or less, 1.1 ⁇ m or less, and 1.0 ⁇ m or less.
  • the average value of the equivalent circle diameters of the tungsten carbide particles is 0.5 ⁇ m or more and 1.2 ⁇ m or less, preferably 0.55 ⁇ m or more and 1.1 ⁇ m or less, and 0.60 ⁇ m or more and 1.0 ⁇ m or less.
  • the equivalent circle diameter of the tungsten carbide particles is measured by the following procedures (A1) to (C1).
  • A1 Any surface or any cross section of cemented carbide is mirror-finished. Examples of the mirror surface processing method include a method of polishing with diamond paste, a method of using a focused ion beam device (FIB device), a method of using a cross section polisher device (CP device), and a method of combining these.
  • FIB device focused ion beam device
  • CP device cross section polisher device
  • FIG. 1 shows an example of an image taken by a scanning electron microscope of the cemented carbide of the present disclosure.
  • (C1) The captured image obtained in (B1) above is taken into a computer by image analysis software (ImageJ, version 1.51j8: https://imagej.nih.gov/ij/) and binarized.
  • the binarization process is executed by pressing the display of "Make Binary" on the computer screen after capturing the image (the binarization process is performed under the conditions preset in the image analysis software). ).
  • a rectangular measurement field of view of 25.3 ⁇ m in length ⁇ 17.6 ⁇ m in width is set in the obtained image after binarization processing, and the equivalent circle diameter (Heywood diameter: equivalent area circle) of the tungsten carbide particles in the measurement field of view is set. Diameter) is calculated.
  • the first phase composed of tungsten carbide particles and the second phase containing cobalt can be distinguished from each other by the shade of color in the photographed image.
  • FIG. 2 shows an image obtained by performing binarization processing on the captured image of FIG. 1.
  • the black region is the first phase and the white region is the second phase.
  • White lines indicate grain boundaries.
  • the measurement results vary even if the diameter equivalent to the circle of the tungsten carbide particles in the cemented carbide is measured multiple times by changing the selection point of the measurement field. It was confirmed that even if the measurement field was set arbitrarily, it would not be arbitrary.
  • the cemented carbide of the present disclosure In the image of the cemented carbide of the present disclosure taken with a scanning electron microscope, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is 10% or less. According to this, the cemented carbide is less likely to cause falling-off wear due to use, and the cemented carbide can have excellent wear resistance.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is 10% or less, preferably 9% or less, and 8% or less.
  • the lower limit of the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is not particularly limited, but may be, for example, 0% or more, 2% or more, or 4% or more.
  • the percentage of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is 0% or more and 10% or less, 0% or more and 9% or less, 0% or more and 8% or less, 2% or more and 10% or less, 2% or more. It can be 9% or less, 2% or more and 8% or less, 4% or more and 10% or less, 4% or more and 9% or less, 4% or more and 8% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less in an image obtained by imaging a cemented carbide with a scanning electron microscope is calculated by the following procedures (D1) and (E1). Will be done.
  • (D1) Prepare three images (corresponding to three measurement fields) of cemented carbide captured by a scanning electron microscope according to the procedures (A1) and (B1) of the method for measuring the equivalent circle diameter of tungsten carbide particles. do.
  • the image processing (binarization processing) described in (C1) of the method for measuring the equivalent circle diameter of the tungsten carbide particles is performed in each of the three measurement fields of view.
  • the size of one measurement field of view is a rectangle having a length of 25.3 ⁇ m and a width of 17.6 ⁇ m.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less in the cemented carbide is changed at the selection point of the measurement field. It was confirmed that even if the measurement was performed multiple times, the variation in the measurement results was small, and even if the measurement field was set arbitrarily, it was not arbitrary.
  • the ratio of the number-based number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is less than 2%. According to this, the cemented carbide has a high bending resistance and can have an excellent breaking resistance.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is less than 2%, preferably 1% or less and 0.5% or less.
  • the lower limit of the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is not particularly limited, but may be, for example, 0% or more, 0.1% or more, and 0.2% or more.
  • the percentage of tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is 0% or more and less than 2%, 0% or more and 1% or less, 0% or more and 0.5% or less, 0.1% or more and less than 2%. , 0.1% or more and 1% or less, 0.1% or more and 0.5% or less, 0.2% or more and less than 2%, 0.2% or more and 1% or less, 0.2% or more and 0.5% or less can do.
  • the ratio based on the number of tungsten carbide particles having a diameter equivalent to a circle of more than 1.8 ⁇ m in an image obtained by imaging a cemented carbide with a scanning electron microscope is calculated by the following procedures (F1) and (G1). Will be done.
  • (F1) Prepare three images (corresponding to three measurement fields) of cemented carbide captured by a scanning electron microscope according to the procedures (A1) and (B1) of the method for measuring the equivalent circle diameter of tungsten carbide particles. do.
  • the image processing (binarization processing) described in (C1) of the method for measuring the equivalent circle diameter of the tungsten carbide particles is performed in each of the three measurement fields of view.
  • the size of one measurement field of view is a rectangle having a length of 25.3 ⁇ m and a width of 17.6 ⁇ m.
  • the ratio of the number-based ratio of the tungsten carbide particles having the equivalent circle diameter of more than 1.8 ⁇ m in the cemented carbide is changed, and the selection point of the measurement field is changed. It was confirmed that even if the measurement was performed multiple times, the variation in the measurement results was small, and even if the measurement field was set arbitrarily, it was not arbitrary.
  • the second phase contains cobalt.
  • the second phase is a bonded phase that binds the tungsten carbide particles constituting the first phase to each other.
  • the second phase contains cobalt (Co)
  • the main component of the second phase is Co.
  • the main component of the second phase is Co means that the mass ratio of cobalt in the second phase is 90% by mass or more and 100% by mass or less.
  • the mass ratio of cobalt in the second phase can be measured by ICP emission spectroscopic analysis (equipment used: "ICPS-8100” (trademark) manufactured by Shimadzu Corporation).
  • the second phase can contain iron elements such as nickel and dissolved substances in alloys (chromium (Cr), tungsten (W), vanadium (V), etc.).
  • the cemented carbide includes a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt, and the ratio of the first phase is 78 in an image obtained by capturing the cemented carbide with a scanning electron microscope. % Or more and less than 100 area%, and the ratio of the second phase is more than 0 area% and 22 area% or less. According to this, the hardness and wear resistance required for processing the printed circuit board can be exhibited, and the occurrence of variation in the tool life can be suppressed.
  • the ratio of the first phase in the cemented carbide is 78 area% or more, the hardness of the cemented carbide is improved.
  • the lower limit of the ratio of the first phase in the cemented carbide can be 78 area% or more and 88 area% or more.
  • the upper limit of the ratio of the first phase in the cemented carbide can be less than 100 area% and 95 area% or less.
  • the ratio of the first phase in the cemented carbide can be 78 area% or more and less than 100 area%, 88 area% or more and 95 area% or less.
  • the ratio of the second phase in the cemented carbide is 22 area% or less, the hardness of the cemented carbide is improved.
  • the lower limit of the ratio of the second phase in the cemented carbide can be more than 0 area% and 5 area% or more.
  • the upper limit of the ratio of the second phase in the cemented carbide can be 22 area% or less and 12 area% or less.
  • the ratio of the second phase in the cemented carbide can be 0 area% or more and 22 area% or less, 5 area% or more and 12 area% or less.
  • the ratio of the first phase is preferably 88 area% or more and 95 area% or less, and the ratio of the second phase is 5 area% or more and 12 area% or less.
  • the area ratio of each of the first phase and the second phase in the cemented carbide is measured by the following procedures (A2) to (C2).
  • (A2) Prepare 5 images (corresponding to 5 measurement fields) of cemented carbide captured by a scanning electron microscope according to the procedures (A1) and (B1) of the method for measuring the equivalent circle diameter of tungsten carbide particles. do.
  • the image processing (binarization processing) described in (C1) of the method for measuring the equivalent circle diameter of the tungsten carbide particles is performed in each of the five measurement fields of view.
  • the size of one measurement field of view is a rectangle having a length of 25.3 ⁇ m and a width of 17.6 ⁇ m.
  • the mass-based content of vanadium in the cemented carbide of the present disclosure is preferably 0 ppm or more and less than 2000 ppm. That is, it is preferable that the cemented carbide of the present disclosure does not contain (a) vanadium, or (b) contains vanadium, the mass-based content of vanadium is less than 2000 ppm.
  • Vanadium has a grain growth inhibitory effect, so it was used in the production of conventional ultrafine cemented carbide. However, when vanadium was added to suppress grain growth, the fine-grained tungsten carbide particles used as a raw material tended to remain in the obtained fine-grained cemented carbide as they were.
  • the upper limit of the vanadium content of the cemented carbide is less than 2000 ppm, preferably less than 100 ppm. Since the smaller the vanadium content of the cemented carbide is, the more preferable it is, the lower limit thereof is 0 ppm.
  • the vanadium content of the cemented carbide can be 0 ppm or more and less than 2000 ppm, and 0 ppm or more and less than 100 ppm.
  • the vanadium content of cemented carbide is measured by ICP emission spectroscopy.
  • the mass-based content of cobalt in the cemented carbide of the present disclosure is more than 0% by mass and 10% by mass or less. According to this, the cemented carbide has a high hardness and can have excellent wear resistance.
  • the upper limit of the cobalt content of the cemented carbide is preferably 9% by mass or less and 8% by mass or less.
  • the lower limit of the cobalt content of the cemented carbide is preferably 1% by mass or more and 2% by mass or more.
  • the cobalt content of the cemented carbide is preferably 1% by mass or more and 9% by mass or less, and 2% by mass or more and 8% by mass or less.
  • the cobalt content in cemented carbide is measured by ICP emission spectroscopy.
  • the cemented carbide of the present disclosure contains chromium (Cr), and the content of the cemented carbide based on the mass of chromium is preferably 0.15% by mass or more and 1.0% by mass or less. Chromium has a grain growth inhibitory effect on tungsten carbide particles.
  • the chromium content in the cemented carbide is 0.15% by mass or more and 1.0% by mass or less, the obtained cemented carbide contains fine-grained tungsten carbide particles as a raw material. It was newly found that the residual particles can be effectively suppressed and the generation of coarse particles can be effectively suppressed.
  • the upper limit of the chromium content of the cemented carbide is preferably 0.95% by mass or less and 0.90% by mass or less.
  • the lower limit of the chromium content of the cemented carbide is preferably 0.20% by mass or more and 0.25% by mass or more.
  • the chromium content of the cemented carbide is preferably 0.20% by mass or more and 0.95% by mass or less, and preferably 0.25% by mass or more and 0.90% by mass or less.
  • the chromium content in cemented carbide is measured by ICP emission spectroscopy.
  • the ratio of chromium to cobalt is preferably 5% or more and 10% or less on a mass basis. Chromium has a grain growth inhibitory effect on tungsten carbide particles. Further, by solid-solving in cobalt, the generation of lattice strain of cobalt is promoted. Therefore, when the cemented carbide contains chromium in the above ratio, the breakage resistance is further improved.
  • chromium may precipitate as carbide and become the starting point of damage.
  • the ratio of chromium to cobalt is 5% or more and 10% or less, the precipitation of carbides of chromium is less likely to occur, and the effect of improving breakage resistance can be obtained.
  • the ratio of chromium to cobalt is 10% or less, the degree of the action of suppressing grain growth becomes appropriate, and the amount of tungsten carbide particles having a circle equivalent diameter of more than 1.2 ⁇ m in the cemented carbide becomes excessive. It can be suppressed.
  • the lower limit of the ratio of chromium to cobalt is preferably 5% or more, more preferably 7% or more.
  • the ratio of chromium to cobalt is preferably 10% or less, more preferably 9% or less.
  • the ratio of chromium to cobalt can be 5% or more and 10% or less, and 7% or more and 9% or less.
  • the cemented carbide of the present embodiment can be typically produced by performing a raw material powder preparation step, a mixing step, a molding step, a sintering step, and a cooling step in the above order. Hereinafter, each step will be described.
  • the preparation step is a step of preparing all the raw material powders of the materials constituting the cemented carbide.
  • the raw material powder include tungsten carbide powder, which is the raw material of the first phase, and cobalt (Co) powder, which is the raw material of the second phase, as essential raw material powders.
  • chromium carbide (Cr 3 C 2 ) powder can be prepared as a grain growth inhibitor.
  • tungsten carbide powder, cobalt powder, and chromium carbide powder commercially available ones can be used.
  • the average particle size of the raw material powder means the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method.
  • the average particle size is measured using "Sub-Sive Sizer Model 95" (trademark) manufactured by Fisher Scientific.
  • the tungsten carbide powder preferably has a ratio d20 / d80 of its 20% volume particle diameter d20 and its 80% volume particle diameter d80 of 0.2 or more and 1 or less.
  • Such tungsten carbide powder has a uniform particle size and a small content of fine tungsten carbide particles having a particle size of 0.3 ⁇ m or less. Therefore, when a cemented carbide is produced using the tungsten carbide powder, the generation of coarse tungsten carbide particles due to dissolution and reprecipitation is suppressed in the sintering step. In addition, the content of fine tungsten carbide particles in the obtained cemented carbide can be reduced.
  • the distribution of the volume particle size of the tungsten carbide powder is measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.
  • the 20% volume particle diameter d20 means the particle size when the volumes of the particles constituting the tungsten carbide powder are integrated in ascending order and occupy 20% of the total volume.
  • the 80% volume particle diameter d80 means the particle size when the volume of each particle constituting the tungsten carbide powder is integrated in ascending order and occupies 80% of the total volume.
  • vanadium carbide (VC) powder having a high effect of suppressing grain growth which is generally used in the production of conventional fine-grained cemented carbide, is not used, or even if it is used, a trace amount is used.
  • the mass-based content in the raw material powder is less than 2000 ppm.
  • the content of fine tungsten carbide particles having a particle size of 0.3 ⁇ m or less in the raw material powder is reduced at the stage of preparing the raw material, so that the amount of vanadium (V) added is reduced. Regardless of this, the area ratio of the fine tungsten carbide particles in the cemented carbide can be kept low.
  • the average particle size of the cobalt powder can be 0.5 ⁇ m or more and 1.5 ⁇ m or less.
  • the average particle size of the chromium carbide powder can be 1.0 ⁇ m or more and 2.0 ⁇ m or less.
  • the average particle size is measured using "Sub-Sive Sizer Model 95" (trademark) manufactured by Fisher Scientific.
  • the mixing process is a step of mixing each raw material powder prepared in the preparation step. By the mixing step, a mixed powder in which each raw material powder is mixed is obtained.
  • the ratio of the tungsten carbide powder in the mixed powder can be, for example, 88.85% by mass or more and 99.83% by mass or less.
  • the ratio of the cobalt powder in the mixed powder can be, for example, more than 0% by mass and 10% by mass or less.
  • the ratio of the chromium carbide powder in the mixed powder can be, for example, 0.17% by mass or more and 1.15% by mass or less.
  • the mixing time can be 15 hours or more and 36 hours or less. Under these conditions, crushing of the raw material powder can be suppressed, and the homogeneity of the particle size of the raw material powder can be maintained.
  • the mixed powder may be granulated as needed.
  • a known granulation method can be applied to the granulation, and for example, a commercially available granulator such as a spray dryer can be used.
  • the molding step is a step of molding the mixed powder obtained in the mixing step into a predetermined shape to obtain a molded product.
  • a predetermined shape include a cutting tool shape (for example, the shape of a small-diameter drill).
  • the sintering step is a step of sintering a molded product obtained in the molding step to obtain a cemented carbide.
  • the sintering temperature can be 1350 to 1450 ° C. According to this, the generation of coarse tungsten carbide particles is suppressed. In addition, the content of fine tungsten carbide particles in the obtained cemented carbide can be reduced.
  • the cooling step is a step of cooling the cemented carbide after the sintering is completed.
  • the cooling conditions general conditions may be adopted, and there is no particular limitation.
  • vanadium carbide (VC) powder having a high effect of suppressing grain growth which is generally used in the production of conventional fine-grained cemented carbide, is not used or is used.
  • VC vanadium carbide
  • the cutting tool of the present disclosure includes a cutting edge made of the above cemented carbide.
  • the cutting edge means a portion involved in cutting, and in cemented carbide, the distance between the cutting edge ridge line and the cutting edge ridge line from the cutting edge ridge line to the cemented carbide side along the vertical line of the tangent line of the cutting edge ridge line is 2 mm. It means a virtual surface that is and an area surrounded by.
  • the cutting tool examples include a cutting tool, a drill, an end mill, a cutting tip with a replaceable cutting edge for milling, a cutting tip with a replaceable cutting edge for turning, a metal saw, a gear cutting tool, a reamer or a tap.
  • the cutting tool of the present disclosure can exert an excellent effect in the case of a small-diameter drill for processing a printed circuit board.
  • the cemented carbide of the present embodiment may constitute the whole of these tools, or may constitute a part of them.
  • “partially constituting” indicates an embodiment in which the cemented carbide of the present embodiment is brazed to a predetermined position of an arbitrary base material to form a cutting edge portion.
  • the cutting tool according to 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.
  • a hard film for example, diamond-like carbon or diamond can be used.
  • the average value of the equivalent circle diameters of the tungsten carbide particles is preferably 0.55 ⁇ m or more and 1.1 ⁇ m or less. In the cemented carbide of the present disclosure, the average value of the equivalent circle diameters of the tungsten carbide particles is preferably 0.60 ⁇ m or more and 1.0 ⁇ m or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is preferably 0% or more and 10% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is preferably 0% or more and 9% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or less is preferably 0% or more and 8% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is preferably 0% or more and less than 2%.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is preferably 0% or more and 1% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 ⁇ m is preferably 0% or more and 0.5% or less.
  • the ratio of the first phase is preferably 88 area% or more and 95 area% or less.
  • the ratio of the second phase is preferably 5 area% or more and 12 area% or less.
  • the ratio of the first phase is preferably 88 area% or more and 95 area% or less, and the ratio of the second phase is preferably 5 area% or more and 12 area% or less. ..
  • the mass-based content of vanadium in the cemented carbide of the present disclosure is preferably 0 ppm or more and less than 2000 ppm.
  • the mass-based content of vanadium in the cemented carbide of the present disclosure is preferably 0 ppm or more and less than 100 ppm.
  • the mass-based content of cobalt in the cemented carbide of the present disclosure is preferably 1% by mass or more and 9% by mass or less.
  • the mass-based content of cobalt in the cemented carbide of the present disclosure is preferably 2% by mass or more and 8% by mass or less.
  • the mass-based content of chromium in the cemented carbide of the present disclosure is preferably 0.20% by mass or more and 0.95% by mass or less.
  • the mass-based content of chromium in the cemented carbide of the present disclosure is preferably 0.25% by mass or more and 0.90% by mass or less.
  • the ratio of chromium to cobalt is preferably 7% or more and 9% or less on a mass basis.
  • Cemented carbides of Samples 1 to 17 were prepared by changing the type, compounding ratio and production conditions of the raw material powder. A small-diameter drill having a cutting edge made of the cemented carbide was produced and evaluated.
  • ⁇ Preparation of sample ⁇ As the raw material powder, a powder having the composition shown in the “raw material” column of Table 1 was prepared. A plurality of tungsten carbide (WC) powders having different average particle sizes were prepared. The average particle size of the WC powder is as shown in the "Average particle size ( ⁇ m)" column of "WC powder” in Table 1. The average particle size of the Co powder is 1.0 ⁇ m. The average particle size of the Cr 3 C 2 powder is 1.5 ⁇ m. The average particle size of the VC powder is 0.9 ⁇ m. The average particle size of the raw material powder is a value measured using "Sub-Sive Sizer Model 95" (trademark) manufactured by Fisher Scientific.
  • d20 / d80 of all the samples was 0.2 or more. It was in the following range.
  • d20 / d80 was measured for the WC powders of Samples 14 to 17, the d20 / d80 of all the samples was 0.1 or more and less than 0.2.
  • the d20 / d80 of the WC powder is a value measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.
  • Samples 1 to 13 correspond to Examples, and Samples 14 to 17 correspond to Comparative Examples. It was confirmed that the samples 1 to 13 had a smaller amount of wear and a longer tool life than the samples 14 to 17.
  • Samples 1 to 13 do not contain vanadium carbide powder, which is generally used as a grain growth inhibitor, or even when the raw material powder contains vanadium carbide powder, the amount is as small as 2000 ppm or less. It was confirmed that the proportion of WC particles having a circle equivalent diameter of 1.8 ⁇ m or more was less than 2% in the obtained cemented carbide, and the grain growth was suppressed.

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Abstract

This cemented carbide includes a first phase comprising a plurality of tungsten carbide particles, and a second phase containing cobalt. In an image obtained by imaging the cemented carbide with a scanning electron microscope, the proportion of the first phase is 78% by surface area or greater but less than 100% by surface area, and, the proportion of the second phase is greater than 0% by surface area and at most 22% by surface area. When equivalent circle diameters are calculated for the tungsten carbide particles in the image, the mean value for the equivalent circle diameters is between 0.5 μm and 1.2 μm inclusive, the tungsten carbide particles having equivalent circle diameters of 0.3 μm or smaller occupy a count-based proportion of 10% or less, and the tungsten carbide particles having equivalent circle diameters of larger than 1.8 μm occupy a count-based proportion of less than 2%. The cemented carbide has a mass-based cobalt content of greater than 0% by mass and at most 10% by mass.

Description

超硬合金及びそれを備える切削工具Cemented carbide and cutting tools equipped with it
　本開示は、超硬合金及びそれを備える切削工具に関する。 This disclosure relates to cemented carbide and cutting tools equipped with it.
　プリント回路基板の穴あけでは、φ１ｍｍ以下の小径の穴あけが主流である。このため、小径ドリル等の工具に用いられる超硬合金としては、硬質相が平均粒径１μｍ以下の炭化タングステン粒子からなる、いわゆる微粒超硬合金が用いられている（例えば、特開２００７－９２０９０号公報（特許文献１）、特開２０１２－５２２３７号公報（特許文献２）、特開２０１２－１１７１００号公報（特許文献３））。 For drilling holes in printed circuit boards, drilling holes with a small diameter of φ1 mm or less is the mainstream. Therefore, as the cemented carbide used for tools such as small-diameter drills, a so-called fine-grained cemented carbide having a hard phase composed of tungsten carbide particles having an average particle size of 1 μm or less is used (for example, Japanese Patent Application Laid-Open No. 2007-92090). Japanese Patent Application Laid-Open No. (Patent Document 1), Japanese Patent Application Laid-Open No. 2012-52237 (Patent Document 2), Japanese Patent Application Laid-Open No. 2012-117100 (Patent Document 3).
特開２００７－９２０９０号公報Japanese Unexamined Patent Publication No. 2007-92090 特開２０１２－５２２３７号公報Japanese Unexamined Patent Publication No. 2012-52237 特開２０１２－１１７１００号公報Japanese Unexamined Patent Publication No. 2012-117100
　本開示の超硬合金は、複数の炭化タングステン粒子からなる第１相と、コバルトを含む第２相と、を備える超硬合金であって、
　前記超硬合金を走査型電子顕微鏡で撮像した画像において、前記第１相の割合が７８面積％以上１００面積％未満、かつ、前記第２相の割合が０面積％超２２面積％以下であり、
　前記画像において前記炭化タングステン粒子のそれぞれの円相当径を算出した場合、前記円相当径の平均値が０．５μｍ以上１．２μｍ以下であり、
　前記円相当径が０．３μｍ以下である前記炭化タングステン粒子の個数基準の割合は１０％以下であり、
　前記円相当径が１．８μｍ超である前記炭化タングステン粒子の個数基準の割合は２％未満であり、
　前記超硬合金の前記コバルトの質量基準の含有量は０質量％超１０質量％以下である。 The cemented carbide of the present disclosure is a cemented carbide comprising a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
In the image of the cemented carbide captured by a scanning electron microscope, the ratio of the first phase is 78 area% or more and less than 100 area%, and the ratio of the second phase is more than 0 area% and 22 area% or less. ,
When the circle-equivalent diameter of each of the tungsten carbide particles is calculated in the image, the average value of the circle-equivalent diameter is 0.5 μm or more and 1.2 μm or less.
The ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of 0.3 μm or less is 10% or less.
The ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of more than 1.8 μm is less than 2%.
The mass-based content of the cobalt in the cemented carbide is more than 0% by mass and 10% by mass or less.
　本開示の切削工具は、上記の超硬合金からなる刃先を備える、切削工具である。 The cutting tool disclosed in the present disclosure is a cutting tool equipped with a cutting edge made of the above-mentioned cemented carbide.
図１は、本開示の超硬合金の走査型電子顕微鏡での撮影画像の一例である。FIG. 1 is an example of an image taken by a scanning electron microscope of the cemented carbide of the present disclosure. 図２は、図１の撮影画像に対して二値化処理を行って得られた画像である。FIG. 2 is an image obtained by performing binarization processing on the captured image of FIG. 1.
　［本開示が解決しようとする課題］
　近年、５Ｇ（第５世代移動通信システム）の拡大に伴い、情報の高容量化が進んでいる。このため、プリント回路基板には更なる耐熱性が求められている。プリント回路基板の耐熱性の向上のため、プリント回路基板を構成する樹脂やガラスフィラーの耐熱性を向上させる技術が開発されている。一方、これによりプリント回路基板の難削化が進んでいる。 [Problems to be solved by this disclosure]
In recent years, with the expansion of 5G (5th generation mobile communication system), the capacity of information has been increasing. Therefore, the printed circuit board is required to have further heat resistance. In order to improve the heat resistance of printed circuit boards, techniques for improving the heat resistance of resins and glass fillers constituting printed circuit boards have been developed. On the other hand, this has made it difficult to cut printed circuit boards.
　そこで、本開示は、工具材料として用いた場合に、特にプリント回路基板の微細加工においても、工具の長寿命化を可能とする超硬合金およびそれを備える切削工具を提供することを目的とする。 Therefore, it is an object of the present disclosure to provide a cemented carbide capable of extending the life of a tool when used as a tool material, especially in microfabrication of a printed circuit board, and a cutting tool provided with the cemented carbide. ..
　[本開示の効果]
　本開示の超硬合金は、工具材料として用いた場合に、特にプリント回路基板の微細加工においても、工具の長寿命化を可能とする。 [Effect of this disclosure]
When used as a tool material, the cemented carbide of the present disclosure enables a long life of a tool, especially in microfabrication of a printed circuit board.
　［本開示の実施形態の説明］
　最初に本開示の実施態様を列記して説明する。
　（１）本開示の超硬合金は、複数の炭化タングステン粒子からなる第１相と、コバルトを含む第２相と、を備える超硬合金であって、
　前記超硬合金を走査型電子顕微鏡で撮像した画像において、前記第１相の割合が７８面積％以上１００面積％未満、かつ、前記第２相の割合が０面積％超２２面積％以下であり、
　前記画像において前記炭化タングステン粒子のそれぞれの円相当径を算出した場合、前記円相当径の平均値が０．５μｍ以上１．２μｍ以下であり、
　前記円相当径が０．３μｍ以下である前記炭化タングステン粒子の個数基準の割合は１０％以下であり、
　前記円相当径が１．８μｍ超である前記炭化タングステン粒子の個数基準の割合は２％未満であり、
　前記超硬合金の前記コバルトの質量基準の含有量は０質量％超１０質量％以下である。 [Explanation of Embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.
(1) The cemented carbide of the present disclosure is a cemented carbide comprising a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
In the image of the cemented carbide captured by a scanning electron microscope, the ratio of the first phase is 78 area% or more and less than 100 area%, and the ratio of the second phase is more than 0 area% and 22 area% or less. ,
When the circle-equivalent diameter of each of the tungsten carbide particles is calculated in the image, the average value of the circle-equivalent diameter is 0.5 μm or more and 1.2 μm or less.
The ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of 0.3 μm or less is 10% or less.
The ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of more than 1.8 μm is less than 2%.
The mass-based content of the cobalt in the cemented carbide is more than 0% by mass and 10% by mass or less.
　本開示の超硬合金は、工具材料として用いた場合に、特にプリント回路基板の微細加工においても、工具の長寿命化を可能とする。 When used as a tool material, the cemented carbide disclosed in the present disclosure makes it possible to extend the life of the tool, especially in the microfabrication of printed circuit boards.
　（２）前記画像において、前記第２相の割合が５面積％以上１２面積％以下であることが好ましい。これによると、工具寿命が更に向上する。 (2) In the image, the ratio of the second phase is preferably 5 area% or more and 12 area% or less. According to this, the tool life is further improved.
　（３）前記超硬合金のクロムの質量基準の含有量は０．１５質量％以上１．０質量％以下であることが好ましい。これによると、工具寿命が更に向上する。 (3) The content of the cemented carbide based on the mass of chromium is preferably 0.15% by mass or more and 1.0% by mass or less. According to this, the tool life is further improved.
　（４）前記コバルトに対する前記クロムの割合は、質量基準で５％以上１０％以下であることが好ましい。これによると、工具寿命が更に向上する。 (4) The ratio of the chromium to the cobalt is preferably 5% or more and 10% or less on a mass basis. According to this, the tool life is further improved.
　（５）前記超硬合金のバナジウムの質量基準の含有量は０ｐｐｍ以上２０００ｐｐｍ未満であることが好ましい。これによると、工具寿命が更に向上する。 (5) The mass-based content of vanadium in the cemented carbide is preferably 0 ppm or more and less than 2000 ppm. According to this, the tool life is further improved.
　（６）前記超硬合金のバナジウムの質量基準の含有量は０ｐｐｍ以上１００ｐｐｍ未満であることが好ましい。これによると、工具寿命が更に向上する。 (6) The mass-based content of vanadium in the cemented carbide is preferably 0 ppm or more and less than 100 ppm. According to this, the tool life is further improved.
　（７）本開示の切削工具は、上記の超硬合金からなる刃先を備える、切削工具である。本開示の切削工具は、長い工具寿命を有する。 (7) The cutting tool of the present disclosure is a cutting tool provided with a cutting edge made of the above-mentioned cemented carbide. The cutting tools of the present disclosure have a long tool life.
　（８）前記切削工具は、プリント回路基板加工用回転工具であることが好ましい。本開示の切削工具は、プリント回路基板の微細加工に好適である。 (8) The cutting tool is preferably a rotary tool for processing a printed circuit board. The cutting tool of the present disclosure is suitable for microfabrication of printed circuit boards.
　［本開示の実施形態の詳細］
　本開示の超硬合金及び切削工具の具体例を、以下に図面を参照しつつ説明する。本開示の図面において、同一の参照符号は、同一部分または相当部分を表すものである。また、長さ、幅、厚さ、深さなどの寸法関係は図面の明瞭化と簡略化のために適宜変更されており、必ずしも実際の寸法関係を表すものではない。 [Details of Embodiments of the present disclosure]
Specific examples of the cemented carbide and the cutting tool of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or equivalent parts. Further, the dimensional relations such as length, width, thickness, and depth are appropriately changed for the purpose of clarifying and simplifying the drawings, and do not necessarily represent the actual dimensional relations.
　本明細書において「Ａ～Ｂ」という形式の表記は、範囲の上限下限（すなわちＡ以上Ｂ以下）を意味し、Ａにおいて単位の記載がなく、Ｂにおいてのみ単位が記載されている場合、Ａの単位とＢの単位とは同じである。 In the present specification, the notation in the form of "A to B" means the upper and lower limits of the range (that is, A or more and B or less), and when there is no description of the unit in A and the unit is described only in B, A. The unit of and the unit of B are the same.
　本明細書において化合物などを化学式で表す場合、原子比を特に限定しないときは従来公知のあらゆる原子比を含むものとし、必ずしも化学量論的範囲のもののみに限定されるべきではない。たとえば「ＷＣ」と記載されている場合、ＷＣを構成する原子数の比は、従来公知のあらゆる原子比が含まれる。 In the present specification, when a compound or the like is represented by a chemical formula, it shall include all conventionally known atomic ratios when the atomic ratio is not particularly limited, and should not necessarily be limited to those in the stoichiometric range. For example, when described as "WC", the ratio of the number of atoms constituting the WC includes any conventionally known atomic ratio.
　本発明者らは、工具の長寿命化を可能とする超硬合金を得るために、従来の微粒超硬合金からなる工具を用いてプリント回路基板を微細加工した場合の、工具の損傷形態を検討した。この結果、従来の微粒超硬合金では、工具の使用に伴い、炭化タングステン粒子の脱落摩耗が生じていることが確認された。脱落摩耗について更に検討したところ、粒径が０．３μｍ以下の炭化タングステン粒子が、特に脱落しやすいことが確認された。 In order to obtain a cemented carbide that can extend the life of the tool, the present inventors describe the damage form of the tool when the printed circuit board is finely machined using a tool made of a conventional fine-grained cemented carbide. investigated. As a result, it was confirmed that in the conventional fine-grained cemented carbide, the tungsten carbide particles fall off and wear with the use of the tool. Further examination of the fall-off wear confirmed that tungsten carbide particles having a particle size of 0.3 μm or less were particularly easy to fall off.
　よって、本発明者等は、長い工具寿命を達成するためには、微粒超硬合金において、工具の使用時に脱落しやすい粒径が０．３μｍ以下の炭化タングステン粒子の含有量を低減することが重要であると推測した。 Therefore, in order to achieve a long tool life, the present inventors can reduce the content of tungsten carbide particles having a particle size of 0.3 μm or less, which easily falls off when the tool is used, in the fine cemented carbide. I guessed it was important.
　微粒超硬合金中の粒径が０．３μｍ以下の炭化タングステン粒子の含有量を低減するために、その製造工程において、原料中の微粒炭化タングステン粒子（粒径約０．２μｍ）の粒成長を促進させることが考えられる。例えば、原料の微粒炭化タングステン粒子の焼結時に、粒成長抑制作用を有するバナジウムやクロムを添加しないことや、高温で焼結を行うことが考えられる。しかし、これらの方法を採用すると、異常粒成長により、粒径が約２μｍ以上の粗大炭化タングステン粒子が発生する。該粗大炭化タングステン粒子は微粒超硬合金の強度を低下させる要因となる。 In order to reduce the content of tungsten carbide particles having a particle size of 0.3 μm or less in the fine cemented carbide, grain growth of fine tungsten carbide particles (particle size of about 0.2 μm) in the raw material is performed in the manufacturing process. It is possible to promote it. For example, when sintering fine-grained tungsten carbide particles as a raw material, it is conceivable not to add vanadium or chromium having a grain growth inhibitory effect, or to perform sintering at a high temperature. However, when these methods are adopted, coarse tungsten carbide particles having a particle size of about 2 μm or more are generated due to abnormal grain growth. The coarse tungsten carbide particles are a factor that lowers the strength of the fine cemented carbide.
　一方、異常粒成長を抑制するため、従来の微粒超硬合金の製造方法のようにバナジウムやクロムを添加すると、得られた微粒超硬合金中に、原料として用いられる微粒炭化タングステン粒子がそのまま残存してしまう傾向があった。 On the other hand, when vanadium or chromium is added as in the conventional method for producing fine-grained cemented carbide in order to suppress abnormal grain growth, fine-grained tungsten carbide particles used as a raw material remain in the obtained fine-grained cemented carbide as they are. I tended to do it.
　本発明者等は上記の事情を鑑み、超硬合金中の粒径０．３μｍ以下の炭化タングステン粒子の含有量を低減し、かつ、粗大炭化タングステン粒子の発生を抑制することのできる原料、組成及び製造条件を鋭意検討の結果、本開示の超硬合金を完成させた。本開示の超硬合金及びそれを備える切削工具の詳細について、下記に説明する。 In view of the above circumstances, the present inventors have a raw material and a composition capable of reducing the content of tungsten carbide particles having a particle size of 0.3 μm or less in the cemented carbide and suppressing the generation of coarse tungsten carbide particles. As a result of diligent examination of the manufacturing conditions, the cemented carbide of the present disclosure was completed. The details of the cemented carbide of the present disclosure and the cutting tool provided with the same will be described below.
　［実施形態１：超硬合金］
　本開示の超硬合金は、
　複数の炭化タングステン粒子からなる第１相と、コバルトを含む第２相と、を備える超硬合金であって、
　超硬合金を走査型電子顕微鏡で撮像した画像において、第１相の割合が７８面積％以上１００面積％未満、かつ、第２相の割合が０面積％超２２面積％以下であり、
　画像において炭化タングステン粒子のそれぞれの円相当径を算出した場合、円相当径の平均値が０．５μｍ以上１．２μｍ以下であり、
　円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は１０％以下であり、
　円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合は２％未満であり、
　超硬合金のコバルトの質量基準の含有量は０質量％超１０質量％以下である。 [Embodiment 1: Cemented Carbide]
The cemented carbide of the present disclosure is
A cemented carbide comprising a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
In the image of the cemented carbide captured by the scanning electron microscope, the ratio of the first phase is 78 area% or more and less than 100 area%, and the ratio of the second phase is more than 0 area% and 22 area% or less.
When the circle-equivalent diameter of each of the tungsten carbide particles is calculated in the image, the average value of the circle-equivalent diameter is 0.5 μm or more and 1.2 μm or less.
The ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is 10% or less.
The ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is less than 2%.
The mass-based content of cobalt in cemented carbide is greater than 0% by mass and 10% by mass or less.
　本開示の超硬合金は、工具材料として用いた場合に、特にプリント回路基板の微細加工においても、工具の長寿命化を可能とする。この理由は明らかではないが、下記の（ｉ）～（ｖ）の通りと推察される。 When used as a tool material, the cemented carbide disclosed in the present disclosure makes it possible to extend the life of the tool, especially in the microfabrication of printed circuit boards. The reason for this is not clear, but it is presumed to be as described in (i) to (v) below.
　（ｉ）本開示の超硬合金において、複数の炭化タングステン粒子からなる第１相の割合が７８面積％以上１００面積％未満、かつ、コバルトを含む第２相の割合が０面積％超２２面積％以下である。これによると、プリント回路基板の加工に対して必要な硬度と耐摩耗性が発揮され、工具寿命のばらつきの発生を抑制することができる。
　（ｉｉ）本開示の超硬合金において、炭化タングステン粒子（以下、「ＷＣ粒子」とも記す。）の円相当径の平均値は０．５μｍ以上１．２μｍ以下である。炭化タングステン粒子の円相当径の平均値が０．５μｍ以上であると、使用に伴う脱落摩耗が生じ難く、超硬合金は優れた耐摩耗性を有することができる。炭化タングステン粒子の円相当径の平均値が１．２μｍ以下であると、超硬合金は高い硬度を有し、優れた耐摩耗性を有することができ、また高い抗折力を有し、優れた耐折損性を有することができる。 (I) In the cemented carbide of the present disclosure, the ratio of the first phase composed of a plurality of tungsten carbide particles is 78 area% or more and less than 100 area%, and the ratio of the second phase containing cobalt is more than 0 area% and 22 areas. % Or less. According to this, the hardness and wear resistance required for processing the printed circuit board can be exhibited, and the occurrence of variation in the tool life can be suppressed.
(Ii) In the cemented carbide of the present disclosure, the average value of the equivalent circle diameters of the tungsten carbide particles (hereinafter, also referred to as “WC particles”) is 0.5 μm or more and 1.2 μm or less. When the average value of the equivalent circle diameters of the tungsten carbide particles is 0.5 μm or more, the cemented carbide is less likely to cause falling wear due to use, and the cemented carbide can have excellent wear resistance. When the average value of the equivalent circle diameters of the tungsten carbide particles is 1.2 μm or less, the cemented carbide has high hardness, can have excellent wear resistance, and has high folding resistance, and is excellent. It can have breakage resistance.
　（ｉｉｉ）本開示の超硬合金において、円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は１０％以下である。これによると、使用に伴う脱落摩耗が生じ難く、超硬合金は優れた耐摩耗性を有することができる。 (Iii) In the cemented carbide disclosed in the present disclosure, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is 10% or less. According to this, the cemented carbide is less likely to cause falling-off wear due to use, and the cemented carbide can have excellent wear resistance.
　（ｉｖ）本開示の超硬合金において、円相当径が１．８μｍ超である該炭化タングステン粒子の個数基準の割合は２％未満である。これによると、超硬合金は高い抗折力を有し、優れた耐折損性を有することができる。 (Iv) In the cemented carbide of the present disclosure, the ratio based on the number of the tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is less than 2%. According to this, the cemented carbide has a high bending resistance and can have an excellent breaking resistance.
　（ｖ）超硬合金のコバルトの質量基準の含有量は０質量％超１０質量％以下である。これによると、超硬合金は高い硬度を有し、優れた耐摩耗性を有することができる。 (V) The mass-based content of cobalt in cemented carbide is more than 0% by mass and 10% by mass or less. According to this, the cemented carbide has a high hardness and can have excellent wear resistance.
　＜第１相＞
　（第１相の組成）
　第１相は、複数の炭化タングステン粒子からなる。ここで、炭化タングステンには、「純粋なＷＣ（不純物元素が一切含有されないＷＣ、不純物元素が検出限界未満となるＷＣも含む。）」だけではなく、「本開示の効果を損なわない限りにおいて、その内部に他の不純物元素が意図的あるいは不可避的に含有されるＷＣ」も含まれる。炭化タングステンに含有される不純物の濃度（不純物を構成する元素が二種類以上の場合は、それらの合計濃度。）は、上記炭化タングステン及び上記不純物の総量に対して０．１質量％未満である。第１相中の不純物元素の含有量は、ＩＣＰ発光分析（Ｉｎｄｕｃｔｉｖｅｌｙ　Ｃｏｕｐｌｅｄ　Ｐｌａｓｍａ）Ｅｍｉｓｓｉｏｎ　Ｓｐｅｃｔｒｏｓｃｏｐｙ（測定装置：島津製作所「ＩＣＰＳ－８１００」（商標））により測定される。 <Phase 1>
(Composition of Phase 1)
The first phase consists of a plurality of tungsten carbide particles. Here, the tungsten carbide is not only "pure WC (including WC containing no impurity element and WC whose impurity element is below the detection limit)", but also "as long as the effect of the present disclosure is not impaired". WC in which other impurity elements are intentionally or inevitably contained is also included. The concentration of impurities contained in tungsten carbide (when two or more kinds of elements constituting the impurities are the total concentration thereof) is less than 0.1% by mass with respect to the total amount of the tungsten carbide and the impurities. .. The content of the impurity element in the first phase is measured by ICP emission spectrometry (Inductively Coupled Plasma) Emission Spectroscopy (measuring device: Shimadzu Corporation "ICPS-8100" (trademark)).
　（炭化タングステン粒子の円相当径）
　本開示の超硬合金を走査型電子顕微鏡で撮像した画像において、炭化タングステン粒子の円相当径の平均値は０．５μｍ以上１．２μｍ以下である。炭化タングステン粒子の円相当径の平均値が０．５μｍ以上であると、使用に伴う脱落摩耗が生じ難く、超硬合金は優れた耐摩耗性を有することができる。炭化タングステン粒子の円相当径の平均値が１．２μｍ以下であると、超硬合金は高い硬度を有し、優れた耐摩耗性を有することができ、また高い抗折力を有し、優れた耐折損性を有することができる。 (Diameter equivalent to a circle of tungsten carbide particles)
In the image of the cemented carbide of the present disclosure taken with a scanning electron microscope, the average value of the equivalent circle diameters of the tungsten carbide particles is 0.5 μm or more and 1.2 μm or less. When the average value of the equivalent circle diameters of the tungsten carbide particles is 0.5 μm or more, the cemented carbide is less likely to cause falling wear due to use, and the cemented carbide can have excellent wear resistance. When the average value of the equivalent circle diameters of the tungsten carbide particles is 1.2 μm or less, the cemented carbide has high hardness, can have excellent wear resistance, and has high folding resistance, and is excellent. It can have breakage resistance.
　炭化タングステン粒子の円相当径の平均値の下限は、０．５μｍ以上、０．５５μｍ以上、０．６０μｍ以上が好ましい。炭化タングステン粒子の円相当径の平均値の上限は、１．２μｍ以下、１．１μｍ以下、１．０μｍ以下が好ましい。炭化タングステン粒子の円相当径の平均値は、０．５μｍ以上１．２μｍ以下であり、０．５５μｍ以上１．１μｍ以下、０．６０μｍ以上１．０μｍ以下が好ましい。 The lower limit of the average value of the equivalent circle diameters of the tungsten carbide particles is preferably 0.5 μm or more, 0.55 μm or more, and 0.60 μm or more. The upper limit of the average value of the equivalent circle diameters of the tungsten carbide particles is preferably 1.2 μm or less, 1.1 μm or less, and 1.0 μm or less. The average value of the equivalent circle diameters of the tungsten carbide particles is 0.5 μm or more and 1.2 μm or less, preferably 0.55 μm or more and 1.1 μm or less, and 0.60 μm or more and 1.0 μm or less.
　炭化タングステン粒子の円相当径は、下記（Ａ１）～（Ｃ１）の手順で測定される。
　（Ａ１）超硬合金の任意の表面又は任意の断面を鏡面加工する。鏡面加工の方法としては、例えば、ダイヤモンドペーストで研磨する方法、集束イオンビーム装置（ＦＩＢ装置）を用いる方法、クロスセクションポリッシャー装置（ＣＰ装置）を用いる方法、及びこれらを組み合わせる方法等が挙げられる。 The equivalent circle diameter of the tungsten carbide particles is measured by the following procedures (A1) to (C1).
(A1) Any surface or any cross section of cemented carbide is mirror-finished. Examples of the mirror surface processing method include a method of polishing with diamond paste, a method of using a focused ion beam device (FIB device), a method of using a cross section polisher device (CP device), and a method of combining these.
　（Ｂ１）超硬合金の加工面を走査型電子顕微鏡（株式会社日立ハイテクノロジーズ製「Ｓ－３４００Ｎ」）で撮影する。条件は、観察倍率５０００倍、加速電圧１０ｋＶ、反射電子像とする。本開示の超硬合金の走査型電子顕微鏡での撮影画像の一例を図１に示す。 (B1) The machined surface of the cemented carbide is photographed with a scanning electron microscope ("S-3400N" manufactured by Hitachi High-Technologies Corporation). The conditions are an observation magnification of 5000 times, an acceleration voltage of 10 kV, and a backscattered electron image. FIG. 1 shows an example of an image taken by a scanning electron microscope of the cemented carbide of the present disclosure.
　（Ｃ１）上記（Ｂ１）で得られた撮影画像を画像解析ソフトウェア（ＩｍａｇｅＪ、ｖｅｒｓｉｏｎ　１．５１ｊ８：https://imagej.nih.gov/ij/）でコンピュータに取り込み、二値化処理を行う。二値化処理は、画像を取り込んだのちに、コンピュータ画面上の「Ｍａｋｅ　Ｂｉｎａｒｙ」との表示を押すことにより実行される（前記画像解析ソフトウェアに予め設定された条件で二値化処理が行われる）。得られた二値化処理後の画像中に縦２５．３μｍ×幅１７．６μｍの矩形の測定視野を設定し、該測定視野中の炭化タングステン粒子の円相当径（Ｈｅｙｗｏｏｄ径：等面積円相当径）を算出する。炭化タングステン粒子からなる第１相とコバルトを含む第２相とは、上記撮影画像中の色の濃淡で識別できる。図１の撮影画像に対して二値化処理を行って得られた画像を図２に示す。図２において、黒色領域は第１相であり、白色領域は第２相である。白色の線は粒界を示す。 (C1) The captured image obtained in (B1) above is taken into a computer by image analysis software (ImageJ, version 1.51j8: https://imagej.nih.gov/ij/) and binarized. The binarization process is executed by pressing the display of "Make Binary" on the computer screen after capturing the image (the binarization process is performed under the conditions preset in the image analysis software). ). A rectangular measurement field of view of 25.3 μm in length × 17.6 μm in width is set in the obtained image after binarization processing, and the equivalent circle diameter (Heywood diameter: equivalent area circle) of the tungsten carbide particles in the measurement field of view is set. Diameter) is calculated. The first phase composed of tungsten carbide particles and the second phase containing cobalt can be distinguished from each other by the shade of color in the photographed image. FIG. 2 shows an image obtained by performing binarization processing on the captured image of FIG. 1. In FIG. 2, the black region is the first phase and the white region is the second phase. White lines indicate grain boundaries.
　出願人が測定した限りでは、同一の試料において測定する限りにおいては、超硬合金における炭化タングステン粒子の円相当径を、測定視野の選択個所を変更して複数回行っても、測定結果のばらつきは少なく、任意に測定視野を設定しても恣意的にはならないことが確認された。 As far as the applicant has measured, as long as the measurement is performed on the same sample, the measurement results vary even if the diameter equivalent to the circle of the tungsten carbide particles in the cemented carbide is measured multiple times by changing the selection point of the measurement field. It was confirmed that even if the measurement field was set arbitrarily, it would not be arbitrary.
　（炭化タングステン粒子の円相当径の分布）
　本開示の超硬合金を走査型電子顕微鏡で撮像した画像において、円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は１０％以下である。これによると、使用に伴う脱落摩耗が生じ難く、超硬合金は優れた耐摩耗性を有することができる。 (Distribution of equivalent circle diameter of tungsten carbide particles)
In the image of the cemented carbide of the present disclosure taken with a scanning electron microscope, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is 10% or less. According to this, the cemented carbide is less likely to cause falling-off wear due to use, and the cemented carbide can have excellent wear resistance.
　円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は１０％以下であり、９％以下、８％以下が好ましい。円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合の下限は特に限定されないが、例えば、０％以上、２％以上、４％以上とすることができる。円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は０％以上１０％以下、０％以上９％以下、０％以上８％以下、２％以上１０％以下、２％以上９％以下、２％以上８％以下、４％以上１０％以下、４％以上９％以下、４％以上８％以下とすることができる。 The ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is 10% or less, preferably 9% or less, and 8% or less. The lower limit of the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is not particularly limited, but may be, for example, 0% or more, 2% or more, or 4% or more. The percentage of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is 0% or more and 10% or less, 0% or more and 9% or less, 0% or more and 8% or less, 2% or more and 10% or less, 2% or more. It can be 9% or less, 2% or more and 8% or less, 4% or more and 10% or less, 4% or more and 9% or less, 4% or more and 8% or less.
　本明細書において、超硬合金を走査型電子顕微鏡で撮像した画像における円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は、下記（Ｄ１）及び（Ｅ１）の手順で算出される。 In the present specification, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less in an image obtained by imaging a cemented carbide with a scanning electron microscope is calculated by the following procedures (D1) and (E1). Will be done.
　（Ｄ１）上記炭化タングステン粒子の円相当径の測定方法の（Ａ１）及び（Ｂ１）の手順に従い、超硬合金を走査型電子顕微鏡で撮像した画像を３枚（３つの測定視野に該当）準備する。上記炭化タングステン粒子の円相当径の測定方法の（Ｃ１）に記載の画像処理（二値化処理）を、３つの測定視野のそれぞれで行う。１つの測定視野の大きさは、縦２５．３μｍ×幅１７．６μｍの矩形とする。 (D1) Prepare three images (corresponding to three measurement fields) of cemented carbide captured by a scanning electron microscope according to the procedures (A1) and (B1) of the method for measuring the equivalent circle diameter of tungsten carbide particles. do. The image processing (binarization processing) described in (C1) of the method for measuring the equivalent circle diameter of the tungsten carbide particles is performed in each of the three measurement fields of view. The size of one measurement field of view is a rectangle having a length of 25.3 μm and a width of 17.6 μm.
　（Ｅ１）３つの測定視野のそれぞれにおいて、測定視野中の全炭化タングステン粒子に対する、円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合を算出する。３つの測定視野における個数基準の割合の平均を、超硬合金における円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合とする。 (E1) In each of the three measurement visual fields, the ratio of the number-based ratio of the tungsten carbide particles having the equivalent circle diameter of 0.3 μm or less to the total tungsten carbide particles in the measurement visual field is calculated. The average of the number-based ratios in the three measurement fields is taken as the number-based ratio of the tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less in the cemented carbide.
　出願人が測定した限りでは、同一の試料において測定する限りにおいては、超硬合金における円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合を、測定視野の選択個所を変更して複数回行っても、測定結果のばらつきは少なく、任意に測定視野を設定しても恣意的にはならないことが確認された。 As far as the applicant has measured, as far as the measurement is performed on the same sample, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less in the cemented carbide is changed at the selection point of the measurement field. It was confirmed that even if the measurement was performed multiple times, the variation in the measurement results was small, and even if the measurement field was set arbitrarily, it was not arbitrary.
　本開示の超硬合金を走査型電子顕微鏡で撮像した画像において、円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合は２％未満である。これによると、超硬合金は高い抗折力を有し、優れた耐折損性を有することができる。 In the image of the cemented carbide disclosed in the present disclosure taken with a scanning electron microscope, the ratio of the number-based number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is less than 2%. According to this, the cemented carbide has a high bending resistance and can have an excellent breaking resistance.
　円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合は２％未満であり、１％以下、０．５％以下が好ましい。円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合の下限は特に限定されないが、例えば、０％以上、０．１％以上、０．２％以上とすることができる。円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合は０％以上２％未満、０％以上１％以下、０％以上０．５％以下、０．１％以上２％未満、０．１％以上１％以下、０．１％以上０．５％以下、０．２％以上２％未満、０．２％以上１％以下、０．２％以上０．５％以下とすることができる。 The ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is less than 2%, preferably 1% or less and 0.5% or less. The lower limit of the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is not particularly limited, but may be, for example, 0% or more, 0.1% or more, and 0.2% or more. The percentage of tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is 0% or more and less than 2%, 0% or more and 1% or less, 0% or more and 0.5% or less, 0.1% or more and less than 2%. , 0.1% or more and 1% or less, 0.1% or more and 0.5% or less, 0.2% or more and less than 2%, 0.2% or more and 1% or less, 0.2% or more and 0.5% or less can do.
　本明細書において、超硬合金を走査型電子顕微鏡で撮像した画像における円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合は、下記（Ｆ１）及び（Ｇ１）の手順で算出される。 In the present specification, the ratio based on the number of tungsten carbide particles having a diameter equivalent to a circle of more than 1.8 μm in an image obtained by imaging a cemented carbide with a scanning electron microscope is calculated by the following procedures (F1) and (G1). Will be done.
　（Ｆ１）上記炭化タングステン粒子の円相当径の測定方法の（Ａ１）及び（Ｂ１）の手順に従い、超硬合金を走査型電子顕微鏡で撮像した画像を３枚（３つの測定視野に該当）準備する。上記炭化タングステン粒子の円相当径の測定方法の（Ｃ１）に記載の画像処理（二値化処理）を、３つの測定視野のそれぞれで行う。１つの測定視野の大きさは、縦２５．３μｍ×幅１７．６μｍの矩形とする。 (F1) Prepare three images (corresponding to three measurement fields) of cemented carbide captured by a scanning electron microscope according to the procedures (A1) and (B1) of the method for measuring the equivalent circle diameter of tungsten carbide particles. do. The image processing (binarization processing) described in (C1) of the method for measuring the equivalent circle diameter of the tungsten carbide particles is performed in each of the three measurement fields of view. The size of one measurement field of view is a rectangle having a length of 25.3 μm and a width of 17.6 μm.
　（Ｇ１）３つの測定視野のそれぞれにおいて、測定視野中の全炭化タングステン粒子に対する、円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合を算出する。これらの平均を超硬合金における円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合とする。 (G1) In each of the three measurement visual fields, the ratio of the number-based ratio of the tungsten carbide particles having the equivalent circle diameter of more than 1.8 μm to the total tungsten carbide particles in the measurement visual field is calculated. The average of these is taken as the ratio based on the number of tungsten carbide particles having a diameter equivalent to a circle of more than 1.8 μm in the cemented carbide.
　出願人が測定した限りでは、同一の試料において測定する限りにおいては、超硬合金における円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合を、測定視野の選択個所を変更して複数回行っても、測定結果のばらつきは少なく、任意に測定視野を設定しても恣意的にはならないことが確認された。 As far as the applicant has measured, as far as the measurement is performed on the same sample, the ratio of the number-based ratio of the tungsten carbide particles having the equivalent circle diameter of more than 1.8 μm in the cemented carbide is changed, and the selection point of the measurement field is changed. It was confirmed that even if the measurement was performed multiple times, the variation in the measurement results was small, and even if the measurement field was set arbitrarily, it was not arbitrary.
　＜第２相＞
　第２相は、コバルトを含む。第２相は、第１相を構成する炭化タングステン粒子同士を結合させる結合相である。 <Phase 2>
The second phase contains cobalt. The second phase is a bonded phase that binds the tungsten carbide particles constituting the first phase to each other.
　ここで、「第２相はコバルト（Ｃｏ）を含む」とは、第２相の主成分がＣｏであることを意味する。「第２相の主成分がＣｏである」とは、第２相中のコバルトの質量比率が９０質量％以上１００質量％以下であることを意味する。第２相中のコバルトの質量比率は、ＩＣＰ発光分光分析法（使用機器：島津製作所製「ＩＣＰＳ－８１００」（商標））により測定することができる。 Here, "the second phase contains cobalt (Co)" means that the main component of the second phase is Co. "The main component of the second phase is Co" means that the mass ratio of cobalt in the second phase is 90% by mass or more and 100% by mass or less. The mass ratio of cobalt in the second phase can be measured by ICP emission spectroscopic analysis (equipment used: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).
　第２相は、コバルトに加えて、ニッケルなどの鉄属元素、合金中の溶解物（クロム（Ｃｒ）、タングステン（Ｗ）、バナジウム（Ｖ）等）を含むことができる。 In addition to cobalt, the second phase can contain iron elements such as nickel and dissolved substances in alloys (chromium (Cr), tungsten (W), vanadium (V), etc.).
　＜超硬合金の組成＞
　（組成）
　超硬合金は、複数の炭化タングステン粒子からなる第１相と、コバルトを含む第２相と、を備え、超硬合金を走査型電子顕微鏡で撮像した画像において、第１相の割合が７８面積％以上１００面積％未満、かつ、第２相の割合が０面積％超２２面積％以下である。これによると、プリント回路基板の加工に対して必要な硬度と耐摩耗性が発揮され、工具寿命のばらつきの発生を抑制することができる。 <Composition of cemented carbide>
(composition)
The cemented carbide includes a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt, and the ratio of the first phase is 78 in an image obtained by capturing the cemented carbide with a scanning electron microscope. % Or more and less than 100 area%, and the ratio of the second phase is more than 0 area% and 22 area% or less. According to this, the hardness and wear resistance required for processing the printed circuit board can be exhibited, and the occurrence of variation in the tool life can be suppressed.
　超硬合金中の第１相の割合が７８面積％以上であると、超硬合金の硬度が向上する。超硬合金中の第１相の割合の下限は、７８面積％以上、８８面積％以上とすることができる。超硬合金中の第１相の割合の上限は、１００面積％未満、９５面積％以下とすることができる。超硬合金中の第１相の割合は、７８面積％以上１００面積％未満、８８面積％以上９５面積％以下とすることができる。 When the ratio of the first phase in the cemented carbide is 78 area% or more, the hardness of the cemented carbide is improved. The lower limit of the ratio of the first phase in the cemented carbide can be 78 area% or more and 88 area% or more. The upper limit of the ratio of the first phase in the cemented carbide can be less than 100 area% and 95 area% or less. The ratio of the first phase in the cemented carbide can be 78 area% or more and less than 100 area%, 88 area% or more and 95 area% or less.
　超硬合金中の第２相の割合が２２面積％以下であると、超硬合金の硬度が向上する。超硬合金中の第２相の割合の下限は、０面積％超、５面積％以上とすることができる。超硬合金中の第２相の割合の上限は、２２面積％以下、１２面積％以下とすることができる。超硬合金中の第２相の割合は、０面積％超２２面積％以下、５面積％以上１２面積％以下とすることができる。 When the ratio of the second phase in the cemented carbide is 22 area% or less, the hardness of the cemented carbide is improved. The lower limit of the ratio of the second phase in the cemented carbide can be more than 0 area% and 5 area% or more. The upper limit of the ratio of the second phase in the cemented carbide can be 22 area% or less and 12 area% or less. The ratio of the second phase in the cemented carbide can be 0 area% or more and 22 area% or less, 5 area% or more and 12 area% or less.
　超硬合金を走査型電子顕微鏡で撮像した画像において、第１相の割合が８８面積％以上９５面積％以下、かつ、第２相の割合が５面積％以上１２面積％以下が好ましい。 In the image of the cemented carbide captured by the scanning electron microscope, the ratio of the first phase is preferably 88 area% or more and 95 area% or less, and the ratio of the second phase is 5 area% or more and 12 area% or less.
　超硬合金中の第１相及び第２相のそれぞれの面積割合は、下記（Ａ２）～（Ｃ２）の手順で測定される。 The area ratio of each of the first phase and the second phase in the cemented carbide is measured by the following procedures (A2) to (C2).
　（Ａ２）上記炭化タングステン粒子の円相当径の測定方法の（Ａ１）及び（Ｂ１）の手順に従い、超硬合金を走査型電子顕微鏡で撮像した画像を５枚（５つの測定視野に該当）準備する。上記炭化タングステン粒子の円相当径の測定方法の（Ｃ１）に記載の画像処理（二値化処理）を、５つの測定視野のそれぞれで行う。１つの測定視野の大きさは、縦２５．３μｍ×幅１７．６μｍの矩形とする。 (A2) Prepare 5 images (corresponding to 5 measurement fields) of cemented carbide captured by a scanning electron microscope according to the procedures (A1) and (B1) of the method for measuring the equivalent circle diameter of tungsten carbide particles. do. The image processing (binarization processing) described in (C1) of the method for measuring the equivalent circle diameter of the tungsten carbide particles is performed in each of the five measurement fields of view. The size of one measurement field of view is a rectangle having a length of 25.3 μm and a width of 17.6 μm.
　（Ｂ２）５つの測定視野のそれぞれにおいて、測定視野の全体を分母として第１相及び第２相のそれぞれの面積割合を測定する。 (B2) In each of the five measurement visual fields, the area ratio of each of the first phase and the second phase is measured with the entire measurement visual field as the denominator.
　（Ｃ２）５つの測定視野で得られた第１相の面積割合の平均を、超硬合金中の第１相の面積割合とする。５つの測定視野で得られた第２相の面積割合の平均を、超硬合金中の第２相の面積割合とする。 (C2) The average of the area ratios of the first phase obtained in the five measurement fields is taken as the area ratio of the first phase in the cemented carbide. The average of the area ratios of the second phase obtained in the five measurement fields is taken as the area ratio of the second phase in the cemented carbide.
　（バナジウム含有量）
　本開示の超硬合金のバナジウムの質量基準の含有量は０ｐｐｍ以上２０００ｐｐｍ未満であることが好ましい。すなわち、本開示の超硬合金は、（ａ）バナジウムを含まない、又は、（ｂ）バナジウムを含む場合はバナジウムの質量基準の含有量は２０００ｐｐｍ未満であることが好ましい。 (Vanadium content)
The mass-based content of vanadium in the cemented carbide of the present disclosure is preferably 0 ppm or more and less than 2000 ppm. That is, it is preferable that the cemented carbide of the present disclosure does not contain (a) vanadium, or (b) contains vanadium, the mass-based content of vanadium is less than 2000 ppm.
　バナジウムは粒成長抑制作用を有するため、従来の超微粒超硬合金の製造時に用いられていた。しかし、粒成長抑制のためにバナジウムを添加すると、得られた微粒超硬合金中に、原料として用いられる微粒炭化タングステン粒子がそのまま残存してしまう傾向があった。 Vanadium has a grain growth inhibitory effect, so it was used in the production of conventional ultrafine cemented carbide. However, when vanadium was added to suppress grain growth, the fine-grained tungsten carbide particles used as a raw material tended to remain in the obtained fine-grained cemented carbide as they were.
　本発明者等は製造条件を鋭意検討した結果、バナジウムを添加しない場合、又は、微量のバナジウムを添加する場合においても、得られた超硬合金中に、原料の微粒炭化タングステン粒子が残存することを効果的に抑制でき、かつ、粗大粒の発生を効果的に抑制できる製造条件を新たに知見した。製造条件の詳細については後述する。 As a result of diligent examination of the production conditions, the present inventors have found that fine particles of tungsten carbide as a raw material remain in the obtained cemented carbide even when vanadium is not added or a small amount of vanadium is added. We have newly discovered the production conditions that can effectively suppress the generation of coarse particles. Details of the manufacturing conditions will be described later.
　超硬合金のバナジウムの含有量の上限は、２０００ｐｐｍ未満であり、１００ｐｐｍ未満が好ましい。超硬合金のバナジウムの含有量は少ないほど好ましいため、その下限は０ｐｐｍである。超硬合金のバナジウムの含有量は、０ｐｐｍ以上２０００ｐｐｍ未満、０ｐｐｍ以上１００ｐｐｍ未満とすることができる。 The upper limit of the vanadium content of the cemented carbide is less than 2000 ppm, preferably less than 100 ppm. Since the smaller the vanadium content of the cemented carbide is, the more preferable it is, the lower limit thereof is 0 ppm. The vanadium content of the cemented carbide can be 0 ppm or more and less than 2000 ppm, and 0 ppm or more and less than 100 ppm.
　超硬合金のバナジウムの含有量は、ＩＣＰ発光分光分析法により測定される。 The vanadium content of cemented carbide is measured by ICP emission spectroscopy.
　（コバルト含有量）
　本開示の超硬合金のコバルトの質量基準の含有量は０質量％超１０質量％以下である。これによると、超硬合金は高い硬度を有し、優れた耐摩耗性を有することができる。 (Cobalt content)
The mass-based content of cobalt in the cemented carbide of the present disclosure is more than 0% by mass and 10% by mass or less. According to this, the cemented carbide has a high hardness and can have excellent wear resistance.
　超硬合金のコバルトの含有量の上限は、９質量％以下、８質量％以下が好ましい。超硬合金のコバルトの含有量の下限は、１質量％以上、２質量％以上が好ましい。超硬合金のコバルトの含有量は、１質量％以上９質量％以下、２質量％以上８質量％以下が好ましい。 The upper limit of the cobalt content of the cemented carbide is preferably 9% by mass or less and 8% by mass or less. The lower limit of the cobalt content of the cemented carbide is preferably 1% by mass or more and 2% by mass or more. The cobalt content of the cemented carbide is preferably 1% by mass or more and 9% by mass or less, and 2% by mass or more and 8% by mass or less.
　超硬合金中のコバルトの含有量は、ＩＣＰ発光分光分析法により測定される。 The cobalt content in cemented carbide is measured by ICP emission spectroscopy.
　（クロム含有量）
　本開示の超硬合金はクロム（Ｃｒ）を含み、超硬合金のクロムの質量基準の含有量は０．１５質量％以上１．０質量％以下であることが好ましい。クロムは炭化タングステン粒子の粒成長抑制作用を有する。本発明者等は検討の結果、超硬合金中のクロムの含有量が０．１５質量％以上１．０質量％以下の場合、得られた超硬合金中に、原料の微粒炭化タングステン粒子が残存することを効果的に抑制でき、かつ、粗大粒の発生を効果的に抑制できることを新たに知見した。 (Chromium content)
The cemented carbide of the present disclosure contains chromium (Cr), and the content of the cemented carbide based on the mass of chromium is preferably 0.15% by mass or more and 1.0% by mass or less. Chromium has a grain growth inhibitory effect on tungsten carbide particles. As a result of the study by the present inventors, when the chromium content in the cemented carbide is 0.15% by mass or more and 1.0% by mass or less, the obtained cemented carbide contains fine-grained tungsten carbide particles as a raw material. It was newly found that the residual particles can be effectively suppressed and the generation of coarse particles can be effectively suppressed.
　超硬合金のクロムの含有量の上限は、０．９５質量％以下、０．９０質量％以下が好ましい。超硬合金のクロムの含有量の下限は、０．２０質量％以上、０．２５質量％以上が好ましい。超硬合金のクロムの含有量は、０．２０質量％以上０．９５質量％以下、０．２５質量％以上０．９０質量％以下が好ましい。 The upper limit of the chromium content of the cemented carbide is preferably 0.95% by mass or less and 0.90% by mass or less. The lower limit of the chromium content of the cemented carbide is preferably 0.20% by mass or more and 0.25% by mass or more. The chromium content of the cemented carbide is preferably 0.20% by mass or more and 0.95% by mass or less, and preferably 0.25% by mass or more and 0.90% by mass or less.
　超硬合金中のクロムの含有量は、ＩＣＰ発光分光分析法により測定される。 The chromium content in cemented carbide is measured by ICP emission spectroscopy.
　（コバルトとクロムの割合）
　本開示の超硬合金において、コバルトに対するクロムの割合は、質量基準で５％以上１０％以下であることが好ましい。クロムは炭化タングステン粒子の粒成長抑制作用を有する。更に、コバルト中に固溶することにより、コバルトの格子歪みの発生を促進する。よって、超硬合金がクロムを上記の割合で含むと、耐折損性が更に向上する。 (Ratio of cobalt and chromium)
In the cemented carbide of the present disclosure, the ratio of chromium to cobalt is preferably 5% or more and 10% or less on a mass basis. Chromium has a grain growth inhibitory effect on tungsten carbide particles. Further, by solid-solving in cobalt, the generation of lattice strain of cobalt is promoted. Therefore, when the cemented carbide contains chromium in the above ratio, the breakage resistance is further improved.
　一方、クロムの量が過剰であると、クロムが炭化物として析出し、破損の起点となる場合がある。コバルトに対するクロムの割合が５％以上１０％以下であると、クロムの炭化物の析出が発生しにくく、耐折損性の向上効果を得ることができる。 On the other hand, if the amount of chromium is excessive, chromium may precipitate as carbide and become the starting point of damage. When the ratio of chromium to cobalt is 5% or more and 10% or less, the precipitation of carbides of chromium is less likely to occur, and the effect of improving breakage resistance can be obtained.
　また、コバルトに対するクロムの割合が１０％以下であると、粒成長抑制作用の程度が適度となり、超硬合金中の円相当径が１．２μｍ超の炭化タングステン粒子の量が過剰になるのを抑制することができる。 Further, when the ratio of chromium to cobalt is 10% or less, the degree of the action of suppressing grain growth becomes appropriate, and the amount of tungsten carbide particles having a circle equivalent diameter of more than 1.2 μm in the cemented carbide becomes excessive. It can be suppressed.
　コバルトに対するクロムの割合の下限は、５％以上が好ましく、７％以上がより好ましい。コバルトに対するクロムの割合は、１０％以下が好ましく、９％以下がより好ましい。コバルトに対するクロムの割合は５％以上１０％以下、７％以上９％以下とすることができる。 The lower limit of the ratio of chromium to cobalt is preferably 5% or more, more preferably 7% or more. The ratio of chromium to cobalt is preferably 10% or less, more preferably 9% or less. The ratio of chromium to cobalt can be 5% or more and 10% or less, and 7% or more and 9% or less.
　＜超硬合金の製造方法＞
　本実施形態の超硬合金は、代表的には、原料粉末の準備工程、混合工程、成形工程、焼結工程、冷却工程を前記の順で行うことにより製造することができる。以下、各工程について説明する。 <Manufacturing method of cemented carbide>
The cemented carbide of the present embodiment can be typically produced by performing a raw material powder preparation step, a mixing step, a molding step, a sintering step, and a cooling step in the above order. Hereinafter, each step will be described.
　≪準備工程≫
　準備工程は、超硬合金を構成する材料の全ての原料粉末を準備する工程である。原料粉末としては、第１相の原料である炭化タングステン粉末、第２相の原料であるコバルト（Ｃｏ）粉末が必須の原料粉末として挙げられる。また、必要に応じて、粒成長抑制剤として、炭化クロム（Ｃｒ３Ｃ２）粉末を準備することができる。炭化タングステン粉末、コバルト粉末、炭化クロム粉末は、市販のものを用いることができる。 ≪Preparation process≫
The preparation step is a step of preparing all the raw material powders of the materials constituting the cemented carbide. Examples of the raw material powder include tungsten carbide powder, which is the raw material of the first phase, and cobalt (Co) powder, which is the raw material of the second phase, as essential raw material powders. Further, if necessary, chromium carbide (Cr 3 C 2 ) powder can be prepared as a grain growth inhibitor. As the tungsten carbide powder, cobalt powder, and chromium carbide powder, commercially available ones can be used.
　炭化タングステン粉末としては、平均粒径が０．５μｍ以上１．５μｍ以下の炭化タングステン粉末を準備する。本明細書において、原料粉末の平均粒径とは、ＦＳＳＳ（Ｆｉｓｈｅｒ　Ｓｕｂ－Ｓｉｅｖｅ　Ｓｉｚｅｒ）法により測定される平均粒径を意味する。該平均粒径は、Ｆｉｓｈｅｒ　Ｓｃｉｅｎｔｉｆｉｃ社製の「Ｓｕｂ－Ｓｉｅｖｅ　Ｓｉｚｅｒ　モデル９５」（商標）を用いて測定される。 As the tungsten carbide powder, prepare a tungsten carbide powder having an average particle size of 0.5 μm or more and 1.5 μm or less. In the present specification, the average particle size of the raw material powder means the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method. The average particle size is measured using "Sub-Sive Sizer Model 95" (trademark) manufactured by Fisher Scientific.
　炭化タングステン粉末は、その２０％体積粒子径ｄ２０と、その８０％体積粒子径ｄ８０との比ｄ２０／ｄ８０が０．２以上１以下であることが好ましい。このような炭化タングステン粉末は粒径が均質であり、粒径が０．３μｍ以下の微粒炭化タングステン粒子の含有量が少ない。このため、該炭化タングステン粉末を用いて超硬合金を作製すると、焼結工程において、溶解再析出による粗大炭化タングステン粒子の発生が抑制される。また、得られた超硬合金中の微粒炭化タングステン粒子の含有量を低減することができる。 The tungsten carbide powder preferably has a ratio d20 / d80 of its 20% volume particle diameter d20 and its 80% volume particle diameter d80 of 0.2 or more and 1 or less. Such tungsten carbide powder has a uniform particle size and a small content of fine tungsten carbide particles having a particle size of 0.3 μm or less. Therefore, when a cemented carbide is produced using the tungsten carbide powder, the generation of coarse tungsten carbide particles due to dissolution and reprecipitation is suppressed in the sintering step. In addition, the content of fine tungsten carbide particles in the obtained cemented carbide can be reduced.
　本明細書において、炭化タングステン粉末の体積粒子径の分布は、マイクロトラック社製の粒度分布測定装置（商品名：ＭＴ３３００ＥＸ）を用いて測定される。２０％体積粒子径ｄ２０とは、炭化タングステン粉末を構成する各粒子の体積を昇順で積算したとき、全体積の２０％を占める時の粒径を意味する。８０％体積粒子径ｄ８０とは、炭化タングステン粉末を構成する各粒子の体積を昇順で積算したとき、全体積の８０％を占める時の粒径を意味する。 In the present specification, the distribution of the volume particle size of the tungsten carbide powder is measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac. The 20% volume particle diameter d20 means the particle size when the volumes of the particles constituting the tungsten carbide powder are integrated in ascending order and occupy 20% of the total volume. The 80% volume particle diameter d80 means the particle size when the volume of each particle constituting the tungsten carbide powder is integrated in ascending order and occupies 80% of the total volume.
　本開示の超硬合金の製造方法では、従来の微粒超硬合金の製造時に一般的に用いられている粒成長抑制効果の高い炭化バナジウム（ＶＣ）粉末は用いない、又は、用いたとしても微量（例えば、原料粉末中の質量基準の含有量は２０００ｐｐｍ未満）である。本開示の超硬合金の製造方法では、原料の準備段階で、粒径が０．３μｍ以下の微粒炭化タングステン粒子の原料粉末中の含有量を低減させているため、バナジウム（Ｖ）の添加量に関わらず、超硬合金中の微粒炭化タングステン粒子の面積比率を低く抑えることができる。なお、原料の準備段階で微粒炭化タングステン粒子の含有量を低減させているため、バナジウム（Ｖ）を添加しない場合にはこれらの微粒炭化タングステン粒子の粒成長が進み、超硬合金中の微粒炭化タングステン粒子をさらに低減することが可能である。一方、元々の原料粉末中の微粒炭化タングステン粒子の数が少ないため、粗大な炭化タングステン粒子が発生する程の異常粒成長が起こることもない。この作用機序は、本発明者らが新たに見出したものである。 In the method for producing cemented carbide of the present disclosure, vanadium carbide (VC) powder having a high effect of suppressing grain growth, which is generally used in the production of conventional fine-grained cemented carbide, is not used, or even if it is used, a trace amount is used. (For example, the mass-based content in the raw material powder is less than 2000 ppm). In the method for producing cemented carbide of the present disclosure, the content of fine tungsten carbide particles having a particle size of 0.3 μm or less in the raw material powder is reduced at the stage of preparing the raw material, so that the amount of vanadium (V) added is reduced. Regardless of this, the area ratio of the fine tungsten carbide particles in the cemented carbide can be kept low. Since the content of the fine tungsten carbide particles is reduced at the stage of preparing the raw material, the grain growth of these fine tungsten carbide particles progresses when vanadium (V) is not added, and the fine particles are carbonized in the cemented carbide. It is possible to further reduce the number of tungsten particles. On the other hand, since the number of fine tungsten carbide particles in the original raw material powder is small, abnormal grain growth that causes coarse tungsten carbide particles does not occur. This mechanism of action was newly discovered by the present inventors.
　コバルト粉末の平均粒径は、０．５μｍ以上１．５μｍ以下とすることができる。炭化クロム粉末の平均粒径は、１．０μｍ以上２．０μｍ以下とすることができる。該平均粒径は、Ｆｉｓｈｅｒ　Ｓｃｉｅｎｔｉｆｉｃ社製の「Ｓｕｂ－Ｓｉｅｖｅ　Ｓｉｚｅｒ　モデル９５」（商標）を用いて測定される。 The average particle size of the cobalt powder can be 0.5 μm or more and 1.5 μm or less. The average particle size of the chromium carbide powder can be 1.0 μm or more and 2.0 μm or less. The average particle size is measured using "Sub-Sive Sizer Model 95" (trademark) manufactured by Fisher Scientific.
　≪混合工程≫
　混合行程は、準備工程で準備した各原料粉末を混合する工程である。混合工程により、各原料粉末が混合された混合粉末が得られる。 ≪Mixing process≫
The mixing process is a step of mixing each raw material powder prepared in the preparation step. By the mixing step, a mixed powder in which each raw material powder is mixed is obtained.
　混合粉末中の炭化タングステン粉末の割合は、例えば、８８．８５質量％以上９９．８３質量％以下とすることができる。 The ratio of the tungsten carbide powder in the mixed powder can be, for example, 88.85% by mass or more and 99.83% by mass or less.
　混合粉末中のコバルト粉末の割合は、例えば、０質量％超１０質量％以下とすることができる。 The ratio of the cobalt powder in the mixed powder can be, for example, more than 0% by mass and 10% by mass or less.
　混合粉末中の炭化クロム粉末の割合は、例えば、０．１７質量％以上１．１５質量％以下とすることができる。 The ratio of the chromium carbide powder in the mixed powder can be, for example, 0.17% by mass or more and 1.15% by mass or less.
　混合粉末をボールミルを用いて混合する。混合時間は１５時間以上３６時間以下とすることができる。これらの条件によると、原料粉末の粉砕を抑制でき、原料粉末の粒径の均質性を維持することができる。 Mix the mixed powder using a ball mill. The mixing time can be 15 hours or more and 36 hours or less. Under these conditions, crushing of the raw material powder can be suppressed, and the homogeneity of the particle size of the raw material powder can be maintained.
　混合工程の後、必要に応じて混合粉末を造粒してもよい。混合粉末を造粒することで、後述する成形工程の際にダイ又は金型へ混合粉末を充填し易い。造粒には、公知の造粒方法が適用でき、例えば、スプレードライヤー等の市販の造粒機を用いることができる。 After the mixing step, the mixed powder may be granulated as needed. By granulating the mixed powder, it is easy to fill the die or the mold with the mixed powder in the molding process described later. A known granulation method can be applied to the granulation, and for example, a commercially available granulator such as a spray dryer can be used.
　≪成形工程≫
　成形工程は、混合工程で得られた混合粉末を所定の形状に成形して、成形体を得る工程である。成形工程における成形方法及び成形条件は、一般的な方法及び条件を採用すればよく、特に問わない。所定の形状としては、例えば、切削工具形状（例えば、小径ドリルの形状）とすることが挙げられる。 ≪Molding process≫
The molding step is a step of molding the mixed powder obtained in the mixing step into a predetermined shape to obtain a molded product. As the molding method and molding conditions in the molding step, general methods and conditions may be adopted, and there is no particular limitation. Examples of the predetermined shape include a cutting tool shape (for example, the shape of a small-diameter drill).
　≪焼結工程≫
　焼結工程は、成形工程で得られた成形体を焼結して、超硬合金を得る工程である。本開示の超硬合金の製造方法においては、焼結温度は１３５０～１４５０℃とすることができる。これによると、粗大炭化タングステン粒子の発生が抑制される。また、得られた超硬合金中の微粒炭化タングステン粒子の含有量を低減することができる。 ≪Sintering process≫
The sintering step is a step of sintering a molded product obtained in the molding step to obtain a cemented carbide. In the method for producing cemented carbide of the present disclosure, the sintering temperature can be 1350 to 1450 ° C. According to this, the generation of coarse tungsten carbide particles is suppressed. In addition, the content of fine tungsten carbide particles in the obtained cemented carbide can be reduced.
　焼結温度が１３５０℃未満であると、粒成長が抑制され、得られた超硬合金中の微粒炭化タングステン粒子の含有量が増加する傾向がある。一方、焼結温度が１４５０℃を超えると、異常粒成長が生じ易い傾向がある。 When the sintering temperature is less than 1350 ° C., grain growth is suppressed and the content of fine tungsten carbide particles in the obtained cemented carbide tends to increase. On the other hand, when the sintering temperature exceeds 1450 ° C., abnormal grain growth tends to occur.
　≪冷却工程≫
　冷却工程は、焼結完了後の超硬合金を冷却する工程である。冷却条件は一般的な条件を採用すればよく、特に問わない。 ≪Cooling process≫
The cooling step is a step of cooling the cemented carbide after the sintering is completed. As the cooling conditions, general conditions may be adopted, and there is no particular limitation.
　本開示の超硬合金の製造方法によれば、従来の微粒超硬合金の製造時に一般的に用いられている粒成長抑制効果の高い炭化バナジウム（ＶＣ）粉末を用いない、又は、用いたとしても微量（例えば、原料粉末中の質量基準の含有量は２０００ｐｐｍ未満）の場合でも、異常粒成長の発生が抑制され、かつ、微粒炭化タングステン粒子の含有量が低減された超硬合金を得ることができる。これは、本発明者らが鋭意検討の結果、新たに見いだしたものである。 According to the method for producing cemented carbide of the present disclosure, vanadium carbide (VC) powder having a high effect of suppressing grain growth, which is generally used in the production of conventional fine-grained cemented carbide, is not used or is used. To obtain a cemented carbide in which the occurrence of abnormal grain growth is suppressed and the content of fine tungsten carbide particles is reduced even in the case of a very small amount (for example, the mass-based content in the raw material powder is less than 2000 ppm). Can be done. This was newly discovered by the present inventors as a result of diligent studies.
　［実施形態２：切削工具］
　本開示の切削工具は、上記超硬合金からなる刃先を含む。本明細書において、刃先とは、切削に関与する部分を意味し、超硬合金において、その刃先稜線と、該刃先稜線から超硬合金側へ、該刃先稜線の接線の垂線に沿う距離が２ｍｍである仮想の面と、に囲まれる領域を意味する。 [Embodiment 2: Cutting Tool]
The cutting tool of the present disclosure includes a cutting edge made of the above cemented carbide. In the present specification, the cutting edge means a portion involved in cutting, and in cemented carbide, the distance between the cutting edge ridge line and the cutting edge ridge line from the cutting edge ridge line to the cemented carbide side along the vertical line of the tangent line of the cutting edge ridge line is 2 mm. It means a virtual surface that is and an area surrounded by.
　切削工具としては、例えば、切削バイト、ドリル、エンドミル、フライス加工用刃先交換型切削チップ、旋削加工用刃先交換型切削チップ、メタルソー、歯切り工具、リーマ又はタップ等を例示できる。特に、本開示の切削工具は、プリント回路基板加工用の小径ドリルの場合に、優れた効果を発揮することができる。 Examples of the cutting tool include a cutting tool, a drill, an end mill, a cutting tip with a replaceable cutting edge for milling, a cutting tip with a replaceable cutting edge for turning, a metal saw, a gear cutting tool, a reamer or a tap. In particular, the cutting tool of the present disclosure can exert an excellent effect in the case of a small-diameter drill for processing a printed circuit board.
　本実施形態の超硬合金は、これらの工具の全体を構成していてもよいし、一部を構成するものであってもよい。ここで「一部を構成する」とは、任意の基材の所定位置に本実施形態の超硬合金をロウ付けして刃先部とする態様等を示している。 The cemented carbide of the present embodiment may constitute the whole of these tools, or may constitute a part of them. Here, "partially constituting" indicates an embodiment in which the cemented carbide of the present embodiment is brazed to a predetermined position of an arbitrary base material to form a cutting edge portion.
　≪硬質膜≫
　本実施形態に係る切削工具は、超硬合金からなる基材の表面の少なくとも一部を被覆する硬質膜を更に備えてもよい。硬質膜としては、例えば、ダイヤモンドライクカーボンやダイヤモンドを用いることができる。 ≪Hard film≫
The cutting tool according to 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.
　［付記１］
　本開示の超硬合金において、炭化タングステン粒子の円相当径の平均値は、０．５５μｍ以上１．１μｍ以下が好ましい。
　本開示の超硬合金において、炭化タングステン粒子の円相当径の平均値は、０．６０μｍ以上１．０μｍ以下が好ましい。 [Appendix 1]
In the cemented carbide of the present disclosure, the average value of the equivalent circle diameters of the tungsten carbide particles is preferably 0.55 μm or more and 1.1 μm or less.
In the cemented carbide of the present disclosure, the average value of the equivalent circle diameters of the tungsten carbide particles is preferably 0.60 μm or more and 1.0 μm or less.
　［付記２］
　本開示の超硬合金において、円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は、０％以上１０％以下が好ましい。
　本開示の超硬合金において、円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は、０％以上９％以下が好ましい。
　本開示の超硬合金において、円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合は、０％以上８％以下が好ましい。 [Appendix 2]
In the cemented carbide of the present disclosure, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is preferably 0% or more and 10% or less.
In the cemented carbide of the present disclosure, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is preferably 0% or more and 9% or less.
In the cemented carbide of the present disclosure, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or less is preferably 0% or more and 8% or less.
　［付記３］
　本開示の超硬合金において、円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合は、０％以上２％未満が好ましい。
　本開示の超硬合金において、円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合は、０％以上１％以下が好ましい。
　本開示の超硬合金において、円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合は、０％以上０．５％以下が好ましい。 [Appendix 3]
In the cemented carbide of the present disclosure, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is preferably 0% or more and less than 2%.
In the cemented carbide of the present disclosure, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is preferably 0% or more and 1% or less.
In the cemented carbide of the present disclosure, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of more than 1.8 μm is preferably 0% or more and 0.5% or less.
　［付記４］
　本開示の超硬合金を走査型電子顕微鏡で撮像した画像において、第１相の割合は８８面積％以上９５面積％以下が好ましい。
　本開示の超硬合金を走査型電子顕微鏡で撮像した画像において、第２相の割合は５面積％以上１２面積％以下が好ましい。
　本開示の超硬合金を走査型電子顕微鏡で撮像した画像において、第１相の割合が８８面積％以上９５面積％以下、かつ、第２相の割合が５面積％以上１２面積％以下が好ましい。 [Appendix 4]
In the image of the cemented carbide of the present disclosure taken with a scanning electron microscope, the ratio of the first phase is preferably 88 area% or more and 95 area% or less.
In the image of the cemented carbide of the present disclosure taken by a scanning electron microscope, the ratio of the second phase is preferably 5 area% or more and 12 area% or less.
In the image of the cemented carbide of the present disclosure taken by a scanning electron microscope, the ratio of the first phase is preferably 88 area% or more and 95 area% or less, and the ratio of the second phase is preferably 5 area% or more and 12 area% or less. ..
　［付記５］
　本開示の超硬合金のバナジウムの質量基準の含有量は、０ｐｐｍ以上２０００ｐｐｍ未満が好ましい。
　本開示の超硬合金のバナジウムの質量基準の含有量は、０ｐｐｍ以上１００ｐｐｍ未満が好ましい。 [Appendix 5]
The mass-based content of vanadium in the cemented carbide of the present disclosure is preferably 0 ppm or more and less than 2000 ppm.
The mass-based content of vanadium in the cemented carbide of the present disclosure is preferably 0 ppm or more and less than 100 ppm.
　［付記６］
　本開示の超硬合金のコバルトの質量基準の含有量は、１質量％以上９質量％以下が好ましい。
　本開示の超硬合金のコバルトの質量基準の含有量は、２質量％以上８質量％以下が好ましい。 [Appendix 6]
The mass-based content of cobalt in the cemented carbide of the present disclosure is preferably 1% by mass or more and 9% by mass or less.
The mass-based content of cobalt in the cemented carbide of the present disclosure is preferably 2% by mass or more and 8% by mass or less.
　［付記７］
　本開示の超硬合金のクロムの質量基準の含有量は、０．２０質量％以上０．９５質量％以下が好ましい。
　本開示の超硬合金のクロムの質量基準の含有量は、０．２５質量％以上０．９０質量％以下が好ましい。 [Appendix 7]
The mass-based content of chromium in the cemented carbide of the present disclosure is preferably 0.20% by mass or more and 0.95% by mass or less.
The mass-based content of chromium in the cemented carbide of the present disclosure is preferably 0.25% by mass or more and 0.90% by mass or less.
　［付記８］
　本開示の超硬合金において、コバルトに対するクロムの割合は、質量基準で７％以上９％以下が好ましい。 [Appendix 8]
In the cemented carbide of the present disclosure, the ratio of chromium to cobalt is preferably 7% or more and 9% or less on a mass basis.
　本実施の形態を実施例によりさらに具体的に説明する。ただし、これらの実施例により本実施の形態が限定されるものではない。 The present embodiment will be described more specifically by way of examples. However, these embodiments do not limit the present embodiment.
　原料粉末の種類、配合比及び製造条件を変更して試料１～試料１７の超硬合金を作製した。該超硬合金からなる刃先を備える小径ドリルを作製し、その評価を行った。 Cemented carbides of Samples 1 to 17 were prepared by changing the type, compounding ratio and production conditions of the raw material powder. A small-diameter drill having a cutting edge made of the cemented carbide was produced and evaluated.
　≪試料の作製≫
　（準備工程）
　原料粉末として、表１の「原料」欄に示す組成の粉末を準備した。炭化タングステン（ＷＣ）粉末は、平均粒径の異なるものを複数準備した。ＷＣ粉末の平均粒径は表１の「ＷＣ粉末」の「平均粒径（μｍ）」欄に示される通りである。Ｃｏ粉末の平均粒径は１．０μｍである。Ｃｒ３Ｃ２粉末の平均粒径は１．５μｍである。ＶＣ粉末の平均粒径は０．９μｍである。原料粉末の平均粒径は、Ｆｉｓｈｅｒ　Ｓｃｉｅｎｔｉｆｉｃ社製の「Ｓｕｂ－Ｓｉｅｖｅ　Ｓｉｚｅｒ　モデル９５」（商標）を用いて測定した値である。 ≪Preparation of sample≫
(Preparation process)
As the raw material powder, a powder having the composition shown in the “raw material” column of Table 1 was prepared. A plurality of tungsten carbide (WC) powders having different average particle sizes were prepared. The average particle size of the WC powder is as shown in the "Average particle size (μm)" column of "WC powder" in Table 1. The average particle size of the Co powder is 1.0 μm. The average particle size of the Cr 3 C 2 powder is 1.5 μm. The average particle size of the VC powder is 0.9 μm. The average particle size of the raw material powder is a value measured using "Sub-Sive Sizer Model 95" (trademark) manufactured by Fisher Scientific.
　試料１～試料１３のＷＣ粉末について、その２０％体積粒子径ｄ２０と、その８０％体積粒子径ｄ８０との比ｄ２０／ｄ８０を測定したところ、全ての試料のｄ２０／ｄ８０は０．２以上１以下の範囲であった。
　試料１４～試料１７のＷＣ粉末について、ｄ２０／ｄ８０を測定したところ、全ての試料のｄ２０／ｄ８０は０．１以上０．２未満であった。
　ＷＣ粉末のｄ２０／ｄ８０は、マイクロトラック社製の粒度分布測定装置（商品名：ＭＴ３３００ＥＸ）を用いて測定した値である。 When the ratio d20 / d80 of the 20% volume particle diameter d20 and the 80% volume particle diameter d80 of the WC powders of Samples 1 to 13 was measured, d20 / d80 of all the samples was 0.2 or more. It was in the following range.
When d20 / d80 was measured for the WC powders of Samples 14 to 17, the d20 / d80 of all the samples was 0.1 or more and less than 0.2.
The d20 / d80 of the WC powder is a value measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.
　（混合工程）
　各原料粉末を表１の「原料」の「質量％」欄に示される配合量で混合し、混合粉末を作製した。表１の「原料」欄の「質量％」とは、原料粉末の合計質量に対する、各原料粉末の割合を示す。混合はボールミル又はアトライターで行った。混合時間は表１の「混合工程」の「混合機／時間」欄に記載の通りである。得られた混合粉末をスプレードライ乾燥して造粒粉末とした。 (Mixing process)
Each raw material powder was mixed in the blending amount shown in the "mass%" column of "raw material" in Table 1 to prepare a mixed powder. “Mass%” in the “raw material” column of Table 1 indicates the ratio of each raw material powder to the total mass of the raw material powder. Mixing was done with a ball mill or attritor. The mixing time is as described in the "Mixer / time" column of "Mixing step" in Table 1. The obtained mixed powder was spray-dried and dried to obtain a granulated powder.
　（成形工程）
　得られた造粒粉末をプレス成形して、φ３．４ｍｍの丸棒形状の成形体を作製した。 (Molding process)
The obtained granulated powder was press-molded to prepare a round bar-shaped molded body having a diameter of 3.4 mm.
　（焼結工程）
　成形体を焼結炉に入れ、真空中で焼結した。焼結温度及び焼結時間は、表１の「焼結工程」の「温度／時間」欄に記載の通りである。 (Sintering process)
The molded product was placed in a sintering furnace and sintered in vacuum. The sintering temperature and sintering time are as described in the "Temperature / Time" column of "Sintering Step" in Table 1.
　（冷却工程）
　焼結完了後、アルゴン（Ａｒ）ガス雰囲気中で徐冷して、超硬合金を得た。 (Cooling process)
After the sintering was completed, the cemented carbide was obtained by slowly cooling in an argon (Ar) gas atmosphere.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　＜評価＞
　各試料の超硬合金について、炭化タングステン粒子の円相当径の平均値及び分布、第１相及び第２相の面積割合、バナジウムの質量基準の含有量、コバルトの質量基準の含有量及びコバルトに対するクロムの質量基準の割合を測定した。 <Evaluation>
For the cemented carbide of each sample, the average value and distribution of the equivalent circle diameter of the tungsten carbide particles, the area ratio of the first phase and the second phase, the mass-based content of vanadium, the mass-based content of cobalt, and the content of cobalt. The mass-based proportion of chromium was measured.
　（炭化タングステン粒子の円相当径の平均値）
　各試料の超硬合金について、炭化タングステン粒子の円相当径の平均値を測定した。具体的な測定方法は、実施の形態１に記載されているため、その説明は繰り返さない。結果を表２の「ＷＣ粒子円相当径」の「平均値」欄に示す。 (Average value of the equivalent circle diameter of tungsten carbide particles)
For the cemented carbide of each sample, the average value of the equivalent circle diameters of the tungsten carbide particles was measured. Since the specific measurement method is described in the first embodiment, the description thereof will not be repeated. The results are shown in the "Mean value" column of "WC particle circle equivalent diameter" in Table 2.
　（炭化タングステン粒子の円相当径の分布）
　各試料の超硬合金について、円相当径が０．３μｍ以下である炭化タングステン粒子の個数基準の割合、及び、円相当径が１．８μｍ超である炭化タングステン粒子の個数基準の割合を算出した。具体的な測定方法及び算出方法は、実施の形態１に記載されているため、その説明は繰り返さない。 (Distribution of equivalent circle diameter of tungsten carbide particles)
For the cemented carbide of each sample, the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or less and the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of more than 1.8 μm were calculated. .. Since the specific measurement method and calculation method are described in the first embodiment, the description thereof will not be repeated.
　結果をそれぞれ表２の「ＷＣ粒子円相当径」の「０．３μｍ以下割合（％）」及び「１．８μｍ超割合」欄に示す。 The results are shown in the "0.3 μm or less ratio (%)" and "1.8 μm or more ratio" columns of "WC particle circle equivalent diameter" in Table 2, respectively.
　（第１相及び第２相の体積割合）
　各試料の超硬合金について、走査型電子顕微鏡で撮影した画像における第１相及び第２相の面積割合を測定した。具体的な測定方法は、実施の形態１に記載されているため、その説明は繰り返さない。結果を表２の「第１相」の「面積％」欄、及び、「第２相」の「面積％」欄に示す。 (Volume ratio of Phase 1 and Phase 2)
For the cemented carbide of each sample, the area ratio of the first phase and the second phase in the image taken by the scanning electron microscope was measured. Since the specific measurement method is described in the first embodiment, the description thereof will not be repeated. The results are shown in the "Area%" column of "Phase 1" and the "Area%" column of "Phase 2" in Table 2.
　（バナジウムの質量基準の含有量、コバルトの質量基準の含有量、コバルトに対するクロムの質量基準の割合）
　各試料の超硬合金について、バナジウムの質量基準の含有量、コバルトの質量基準の含有量及びコバルトに対するクロムの質量基準の割合を測定した。具体的な測定方法は、実施の形態１に記載されているため、その説明は繰り返さない。結果を表２の「Ｖ」の「ｐｐｍ」、「Ｃｏ」の「質量％」、「Ｃｒ」の「質量％」及び「Ｃｒ／Ｃｏ」の「％」欄に示す。 (Vanadium mass-based content, cobalt mass-based content, chromium mass-based ratio to cobalt)
For the cemented carbide of each sample, the mass-based content of vanadium, the mass-based content of cobalt, and the ratio of the mass-based chromium to cobalt were measured. Since the specific measurement method is described in the first embodiment, the description thereof will not be repeated. The results are shown in the "ppm" of "V", the "mass%" of "Co", the "mass%" of "Cr" and the "%" column of "Cr / Co" in Table 2.
　＜切削試験＞
　各試料の丸棒を加工し、刃径φ０．３５ｍｍの小径ドリルを作製した。現在、刃部のみをステンレスシャンクに圧入してドリルを成形することが主流であるが、評価のためにφ３．４ｍｍの丸棒の先端を刃付け加工することでドリルの作製を行った。該ドリルを用いて市販の車載用プリント回路基板の穴開け加工を行った。穴開け加工の条件は、回転数１５５ｋｒｐｍ、送り速度２．５ｍ／ｍｉｎとした。１００００個の穴あけを行った後のドリルの摩耗量を、ドリル径の減少量により算出した。３本のドリルで穴開け加工を行った。３本の摩耗量の平均値を表２の「摩耗量（μｍ）」欄に示す。また、穴開け加工後の刃先状態の観察を行った。その結果を表１の「刃先状態」欄に示す。 <Cutting test>
The round bar of each sample was processed to produce a small-diameter drill with a blade diameter of φ0.35 mm. Currently, the mainstream is to press-fit only the blade into a stainless shank to form a drill, but for evaluation, the drill was manufactured by cutting the tip of a round bar with a diameter of 3.4 mm. Using the drill, a commercially available printed circuit board for automobiles was drilled. The conditions for drilling were a rotation speed of 155 kHz and a feed rate of 2.5 m / min. The amount of wear of the drill after drilling 10,000 holes was calculated by the amount of decrease in the drill diameter. Drilling was performed with three drills. The average value of the three wear amounts is shown in the "wear amount (μm)" column of Table 2. In addition, the state of the cutting edge after drilling was observed. The results are shown in the "edge state" column of Table 1.
　摩耗量が小さいほどドリルの工具寿命が長いことを示す。「摩耗量（μｍ）」欄に「－」と記載されている場合は、２本以上のドリルにおいて加工開始直後に折損が生じ、摩耗量を測定できなかったことを示す。また、「刃先状態」欄に「１本折損」と記載されている場合は、折損しなかった２本の摩耗量の平均値を表２の「摩耗量（μｍ）」欄に示す。「刃先状態」欄に「微小チッピング」と記載されている場合は、刃先に微小なチッピングが生じていることを示す。 The smaller the amount of wear, the longer the tool life of the drill. When "-" is described in the "wear amount (μm)" column, it means that the two or more drills were broken immediately after the start of machining and the wear amount could not be measured. When "one broken edge" is described in the "cutting edge state" column, the average value of the wear amount of the two pieces that did not break is shown in the "wear amount (μm)" column of Table 2. When "fine chipping" is described in the "cutting edge state" column, it indicates that minute chipping has occurred on the cutting edge.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　＜考察＞
　試料１～試料１３は実施例に該当し、試料１４～試料１７は比較例に該当する。試料１～試料１３は、試料１４～試料１７に比べて、摩耗量が少なく、工具寿命が長いことが確認された。 <Discussion>
Samples 1 to 13 correspond to Examples, and Samples 14 to 17 correspond to Comparative Examples. It was confirmed that the samples 1 to 13 had a smaller amount of wear and a longer tool life than the samples 14 to 17.
　試料１～試料１３は、原料粉末が粒成長抑制剤として一般的に用いられている炭化バナジウム粉末を含まない、又は、炭化バナジウム粉末を含む場合であっても２０００ｐｐｍ以下と微量であるが、得られた超硬合金において、円相当径が１．８μｍ以上のＷＣ粒子の割合が２％未満であり、粒成長が抑制されていることが確認された。 Samples 1 to 13 do not contain vanadium carbide powder, which is generally used as a grain growth inhibitor, or even when the raw material powder contains vanadium carbide powder, the amount is as small as 2000 ppm or less. It was confirmed that the proportion of WC particles having a circle equivalent diameter of 1.8 μm or more was less than 2% in the obtained cemented carbide, and the grain growth was suppressed.
　以上のように本開示の実施の形態および実施例について説明を行なったが、上述の各実施の形態および実施例の構成を適宜組み合わせたり、様々に変形することも当初から予定している。
　今回開示された実施の形態および実施例はすべての点で例示であって、制限的なものではないと考えられるべきである。本発明の範囲は上記した実施の形態および実施例ではなく請求の範囲によって示され、請求の範囲と均等の意味、および範囲内でのすべての変更が含まれることが意図される。 Although the embodiments and examples of the present disclosure have been described as described above, it is planned from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined or variously modified.
The embodiments and examples disclosed this time should be considered to be exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the embodiments and examples described above, and is intended to include the meaning equivalent to the scope of claims and all modifications within the scope.

Claims (8)

  1. 　複数の炭化タングステン粒子からなる第１相と、コバルトを含む第２相と、を備える超硬合金であって、
    　前記超硬合金を走査型電子顕微鏡で撮像した画像において、前記第１相の割合が７８面積％以上１００面積％未満、かつ、前記第２相の割合が０面積％超２２面積％以下であり、
    　前記画像において前記炭化タングステン粒子のそれぞれの円相当径を算出した場合、前記円相当径の平均値が０．５μｍ以上１．２μｍ以下であり、
    　前記円相当径が０．３μｍ以下である前記炭化タングステン粒子の個数基準の割合は１０％以下であり、
    　前記円相当径が１．８μｍ超である前記炭化タングステン粒子の個数基準の割合は２％未満であり、
    　前記超硬合金の前記コバルトの質量基準の含有量は０質量％超１０質量％以下である、超硬合金。     A cemented carbide comprising a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
    In the image of the cemented carbide captured by a scanning electron microscope, the ratio of the first phase is 78 area% or more and less than 100 area%, and the ratio of the second phase is more than 0 area% and 22 area% or less. ,
    When the circle-equivalent diameter of each of the tungsten carbide particles is calculated in the image, the average value of the circle-equivalent diameter is 0.5 μm or more and 1.2 μm or less.
    The ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of 0.3 μm or less is 10% or less.
    The ratio of the number-based number of the tungsten carbide particles having the equivalent circle diameter of more than 1.8 μm is less than 2%.
    A cemented carbide having a cobalt mass-based content of more than 0% by mass and 10% by mass or less.
  2. 　前記画像において、前記第２相の割合が５面積％以上１２面積％以下である、請求項１に記載の超硬合金。 The cemented carbide according to claim 1, wherein in the image, the ratio of the second phase is 5 area% or more and 12 area% or less.
  3. 　前記超硬合金のクロムの質量基準の含有量は０．１５質量％以上１．０質量％以下である、請求項１又は請求項２に記載の超硬合金。 The cemented carbide according to claim 1 or 2, wherein the content of the cemented carbide based on the mass of chromium is 0.15% by mass or more and 1.0% by mass or less.
  4. 　前記コバルトに対する前記クロムの割合は、質量基準で５％以上１０％以下である、請求項３に記載の超硬合金。 The cemented carbide according to claim 3, wherein the ratio of the chromium to the cobalt is 5% or more and 10% or less on a mass basis.
  5. 　前記超硬合金のバナジウムの質量基準の含有量は０ｐｐｍ以上２０００ｐｐｍ未満である、請求項１から請求項４のいずれか１項に記載の超硬合金。 The cemented carbide according to any one of claims 1 to 4, wherein the content of vanadium in the cemented carbide is 0 ppm or more and less than 2000 ppm.
  6. 　前記超硬合金のバナジウムの質量基準の含有量は０ｐｐｍ以上１００ｐｐｍ未満である、請求項５に記載の超硬合金。 The cemented carbide according to claim 5, wherein the cemented carbide has a vanadium mass-based content of 0 ppm or more and less than 100 ppm.
  7. 　請求項１から請求項６のいずれか１項に記載の超硬合金からなる刃先を備える、切削工具。 A cutting tool provided with a cutting edge made of the cemented carbide according to any one of claims 1 to 6.
  8. 　前記切削工具は、プリント回路基板加工用回転工具である、請求項７に記載の切削工具。 The cutting tool according to claim 7, wherein the cutting tool is a rotary tool for processing a printed circuit board.
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