WO2021199260A1 - Cemented carbide and cutting tool comprising same - Google Patents

Cemented carbide and cutting tool comprising same Download PDF

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Publication number
WO2021199260A1
WO2021199260A1 PCT/JP2020/014778 JP2020014778W WO2021199260A1 WO 2021199260 A1 WO2021199260 A1 WO 2021199260A1 JP 2020014778 W JP2020014778 W JP 2020014778W WO 2021199260 A1 WO2021199260 A1 WO 2021199260A1
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WIPO (PCT)
Prior art keywords
less
range
tungsten carbide
cemented carbide
carbide particles
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PCT/JP2020/014778
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French (fr)
Japanese (ja)
Inventor
広瀬　和弘
隆洋 山川
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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 CN202080002969.6A priority Critical patent/CN113748222A/en
Priority to JP2020548827A priority patent/JP6912033B1/en
Priority to PCT/JP2020/014778 priority patent/WO2021199260A1/en
Priority to TW109134615A priority patent/TWI748676B/en
Priority to JP2021044526A priority patent/JP2021161539A/en
Publication of WO2021199260A1 publication Critical patent/WO2021199260A1/en

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    • 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
    • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
    • 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
    • B23B41/00—Boring or drilling machines or devices specially adapted for particular work; Accessories specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B51/00—Tools for drilling machines
    • 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
    • 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
    • C22C1/10—Alloys containing non-metals
    • 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

Definitions

  • This disclosure relates to cemented carbide and cutting tools equipped with it.
  • JP-A-2007-92090 Japanese Unexamined Patent Publication No. 2012-52237 Japanese Unexamined Patent Publication No. 2012-117100
  • the cemented carbide of the present disclosure is a cemented carbide including a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
  • the equivalent circle diameter of each of the tungsten carbide particles is calculated by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the equivalent circle diameter is 0.3 ⁇ m or more and 1.0 ⁇ m.
  • the ratio based on the number of the tungsten carbide particles below is 50% or more.
  • the distribution of the equivalent circle diameter of the tungsten carbide particles is represented by a histogram with the frequency as the vertical axis and the class as the horizontal axis,
  • the frequency is the number of the tungsten carbide particles, and is In the class, the equivalent circle diameter is divided in ascending order at intervals of 0.1 ⁇ m.
  • On the horizontal axis a range of more than 0.3 ⁇ m and 0.6 ⁇ m or less is defined as the first range, and a range of more than 0.6 ⁇ m and 1.0 ⁇ m or less is defined as the second range.
  • the first range and the second range each have at least one maximum frequency.
  • the ratio of the largest first maximum power to the total number of the tungsten carbide particles is 10% or more. It is a cemented carbide in which the ratio of the largest second maximum power to the total number of the tungsten carbide particles among the maximum powers existing in the second range is 10% or more.
  • the cutting tool of the present disclosure is a cutting tool having a cutting edge made of the above-mentioned cemented carbide.
  • FIG. 1 is an example of an image of the cemented carbide of the present disclosure taken by a scanning electron microscope.
  • FIG. 2 is an image obtained by performing image processing on the captured image of FIG.
  • FIG. 3 is a diagram showing an example of the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure.
  • FIG. 4 is a diagram showing another example of the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure.
  • FIG. 5 is a diagram showing another example of the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure.
  • FIG. 6 is a diagram showing another example of the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure.
  • an object of the present disclosure is to provide a cemented carbide capable of extending the life of a tool when used as a tool material, particularly even 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 including a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
  • the equivalent circle diameter of each of the tungsten carbide particles is calculated by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the equivalent circle diameter is 0.3 ⁇ m or more and 1.0 ⁇ m.
  • the ratio based on the number of the tungsten carbide particles below is 50% or more.
  • the distribution of the equivalent circle diameter of the tungsten carbide particles is represented by a histogram with the frequency as the vertical axis and the class as the horizontal axis,
  • the frequency is the number of the tungsten carbide particles, and is In the class, the equivalent circle diameter is divided in ascending order at intervals of 0.1 ⁇ m.
  • On the horizontal axis a range of more than 0.3 ⁇ m and 0.6 ⁇ m or less is defined as the first range, and a range of more than 0.6 ⁇ m and 1.0 ⁇ m or less is defined as the second range.
  • the first range and the second range each have at least one maximum frequency.
  • the ratio of the largest first maximum power to the total number of the tungsten carbide particles is 10% or more. It is a cemented carbide in which the ratio of the largest second maximum power to the total number of the tungsten carbide particles among the maximum powers existing in the second range is 10% or more.
  • the cemented carbide of the present disclosure makes it possible to extend the life of the tool, especially in the microfabrication of printed circuit boards.
  • the cemented carbide contains 75 area% or more and less than 100 area% of the first phase and more than 0% by volume and 20 area% or less of the second phase in an image taken by a scanning electron microscope. Is preferable. According to this, the tool life is further improved.
  • the cemented carbide preferably contains the second phase in an amount of 5 area% or more and 12 area% or less in an image taken with a scanning electron microscope. According to this, the tool life is further improved.
  • the cemented carbide contains chromium and contains chromium.
  • the mass-based ratio of the chromium to the cobalt is preferably 5% or more and 10% or less. According to this, the breakage resistance of the cemented carbide is improved, and the tool life is further improved.
  • the mass-based content of the vanadium in the cemented carbide is preferably less than 100 ppm. According to this, the strength of the cemented carbide is improved.
  • the ratio based on the number of the tungsten carbide particles having the equivalent circle diameter of less than 0.3 ⁇ m is preferably 7% or less. According to this, the tool life is further improved.
  • the ratio of the second maximum frequency to the first maximum frequency is preferably 0.8 or more and 1.2 or less. According to this, the tool life is further improved.
  • the third range has the first maximal frequency and the fourth range preferably has the second maximum frequency. 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 a printed circuit board.
  • 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) unless otherwise defined, and the unit is not described in A and the unit is described only in B. If so, the unit of A and the unit of B are the same.
  • a compound or the like when represented by a chemical formula in the present specification, 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.
  • a glass epoxy substrate in which a glass woven cloth in which glass fibers are woven into a cloth shape is impregnated with an epoxy resin, a glass polyimide substrate in which a glass woven cloth is impregnated with a polyimide resin, or the like is used. ing.
  • the cemented carbide of the present disclosure is a cemented carbide including a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
  • the equivalent circle diameter of each of the tungsten carbide particles is calculated by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the equivalent circle diameter is 0.3 ⁇ m or more and 1.0 ⁇ m or less.
  • the ratio based on the number of tungsten carbide particles is 50% or more, and when the distribution of the equivalent circle diameter of the tungsten carbide particles is represented by a histogram with the frequency as the vertical axis and the class as the horizontal axis, the frequency is the tungsten carbide particles.
  • the equivalent circle diameter is divided in ascending order at 0.1 ⁇ m intervals, and the range of more than 0.3 ⁇ m and 0.6 ⁇ m or less is defined as the first range on the horizontal axis, and is 0.6 ⁇ m.
  • the range of super 1.0 ⁇ m or less is defined as the second range, and the first range and the second range each have at least one maximum frequency, and the first maximum frequency existing in the first range is the largest.
  • the ratio of the maximum frequency to the total number of tungsten carbide particles is 10% or more, and the ratio of the maximum second maximum frequency to the total number of tungsten carbide particles existing in the second range is 10% or more. It is a cemented carbide.
  • the cemented carbide of 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 shown in (i) and (ii) below.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less is 50% or more. According to this, the cemented carbide structure becomes homogeneous, it is possible to suppress a decrease in the accuracy of microfabrication due to use, and the tool life is extended.
  • the distribution of the equivalent circle diameter of the WC particles is in the range of the particle size of more than 0.3 ⁇ m and not more than 0.6 ⁇ m (first range) and the range of more than 0.6 ⁇ m and not more than 1.0 ⁇ m (the first range).
  • Each of the second range) has at least one maximum frequency.
  • the maximum maximum power in the first range (first maximum power) and the maximum maximum power in the second range (second maximum power) are each 10% of the total number of tungsten carbide particles in the cemented carbide. That is all.
  • the cemented carbide has a structure in which WC particles having a large circle-equivalent diameter form a skeleton, and WC particles having a small circle-equivalent diameter fill a gap between the WC particles. Since the WC particles are bonded to each other in the cemented carbide, the wear resistance is improved by suppressing the WC particles from falling off. Further, by suppressing wear, an increase in cutting resistance is suppressed and breakage resistance is improved. Therefore, the tool life is extended.
  • the amount of cobalt exposed on the tool surface during machining is reduced as compared with the conventional fine-grained cemented carbide. Therefore, the cobalt is less likely to be worn during processing, the WC particles can be suppressed from falling off, and the tool life is extended.
  • the first phase consists of tungsten carbide particles.
  • tungsten carbide includes not only "pure WC (WC containing no impurity elements, WC in which impurity elements are below the detection limit)", but also "as long as the effects of the present disclosure are not impaired.”"WC” in which other impurity elements are intentionally or unavoidably 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 impurity elements in the first phase is measured by ICP emission spectrometry (Inductively Coupled Plasma) Emission Spectroscopy (measuring apparatus: Shimadzu Corporation "ICPS-8100" (trademark)).
  • the ratio of the number-based number of tungsten carbide particles having a circle-equivalent diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less is 50% or more. According to this, the cemented carbide structure becomes homogeneous, it is possible to suppress a decrease in the accuracy of microfabrication due to use, and the tool life is extended.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less is 50% or more, preferably 70% or more, from the viewpoint of improving the homogeneity of the cemented carbide structure.
  • the upper limit of the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less is not particularly limited, but may be, for example, 100% or less, 90% or less, or 80% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less can be 50% or more and 100% or less, 60% or more and 90% or less, and 70% or more and 80% or less.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of less than 0.3 ⁇ m is preferably 7% or less.
  • Tungsten carbide particles having a circle-equivalent diameter of less than 0.3 ⁇ m have a small contribution to improving the strength of cemented carbide and reducing the amount of cobalt exposed on the tool surface during machining. Therefore, by reducing the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of less than 0.3 ⁇ m, the tool life is further extended.
  • the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of less than 0.3 ⁇ m is preferably 0% or more and 7% or less, and more preferably 0% or more and 5% or less. Further, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of less than 0.2 ⁇ m is preferably 0% or more and 3% or less.
  • the equivalent circle diameter of the tungsten carbide particles is measured by the following procedures (A1) to (C1).
  • (A1) Mirror finish any surface or any cross section of cemented carbide. 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 of the cemented carbide of the present disclosure taken with a scanning electron microscope. On the lower right scale of FIG. 1, one scale indicates 1 ⁇ m.
  • (C1) The captured image obtained in (B1) above is taken into a computer, image processing is performed using image analysis software (ImageJ: https://imagej.nih.gov/ij/), and a circle of tungsten carbide particles.
  • the equivalent diameter (Heywood diameter: equivalent area circle equivalent diameter) is calculated.
  • the first phase composed of tungsten carbide particles and the second phase containing cobalt can be distinguished by the shade of color in the photographed image.
  • An image obtained by performing image processing on the captured image of FIG. 1 is shown in FIG. In FIG. 2, the black region is the first phase and the white region is the second phase. White lines indicate grain boundaries. On the lower right scale of FIG. 2, one scale indicates 1 ⁇ m.
  • the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less in the cemented carbide is calculated by the following procedures (D1) and (E1).
  • D1) The image processing of the above (C1) is performed in 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 number of tungsten carbide particles having a circle equivalent diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less in the cemented carbide is selected as the measurement field. It was confirmed that even if the measurement results were changed multiple times, the variation in the measurement results was small, and even if the measurement field was set arbitrarily, it would not be arbitrary.
  • the distribution of the equivalent circle diameter of the tungsten carbide particles contained in the cemented carbide of the present disclosure satisfies the following (a). Further, when the distribution of the equivalent circle diameters of the tungsten carbide particles contained in the cemented carbide of the present disclosure is represented by a histogram having the frequency as the vertical axis and the class as the horizontal axis, the following (b) and (c) are satisfied.
  • the frequency is the number of tungsten carbide particles
  • the class is divided by 0.1 ⁇ m intervals in ascending order of the equivalent circle diameters.
  • the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less is 50% or more.
  • the ratio of the largest first maximum power to the total number of tungsten carbide particles is 10% or more, which is the largest among the maximum powers existing in the second range.
  • the ratio to the total number of tungsten carbide particles having the second maximum frequency is 10% or more.
  • the histogram is prepared by the following procedures (A2) and (B2).
  • the equivalent circle diameter of the tungsten carbide particles is calculated by the procedure (A1) to (C1) described in the above method for measuring the equivalent circle diameter of the tungsten carbide particles.
  • the measurement of the equivalent circle diameter of the tungsten carbide particles is performed in three measurement fields.
  • the maximum frequency is the frequency of a class whose frequency is one lower than the class to which the frequency belongs (the side having a smaller equivalent circle diameter), and the frequency of the class to which the frequency belongs (one higher than the class to which the frequency belongs (). It means that it is larger than any of the frequencies of the class (on the side with the larger equivalent diameter of the circle).
  • the class one level below the class to which the maximum frequency belongs and the class one level above the class to which the maximum frequency belongs may be a class outside the first range or a class outside the second range.
  • the class to which the maximum frequency belongs in the first range is more than 0.3 ⁇ m and 0.4 ⁇ m or less
  • the next lower class is more than 0.2 ⁇ m and 0.3 ⁇ m or less outside the first range.
  • the class to which the maximum frequency belongs in the second range is more than 0.9 ⁇ m and 1.0 ⁇ m or less
  • the class one level higher is more than 1.0 ⁇ m and 1.1 ⁇ m or less outside the second range.
  • FIGS. 3 to 6 are examples of diagrams showing the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure, respectively.
  • the horizontal axis shows the class in which the equivalent circle diameter is divided in ascending order at intervals of 0.1 ⁇ m
  • the vertical axis shows the ratio (%) of the number of tungsten particles belonging to each class to all the tungsten particles. ..
  • the notation in the form of "C to D” means C super D or less.
  • the notation “0 to 0.1” on the horizontal axis of FIGS. 3 to 6 means more than 0 ⁇ m and 0.1 ⁇ m or less
  • the notation “0.1 to 0.2” means 0. It means more than 1 ⁇ m and 0.2 ⁇ m or less.
  • FIGS. 3 to 6 can be regarded as the shape of the histogram when the rules of the class on the horizontal axis are the same and the frequency on the vertical axis is the number of tungsten carbide particles. Therefore, the above (a) to (c) can be described using the shapes of FIGS. 3 to 6.
  • the vertical axis shows the ratio (%) of the number of tungsten particles belonging to each class to the total tungsten particles.
  • the axis may be referred to as frequency.
  • the frequency in the class having a circle equivalent diameter of more than 0.4 ⁇ m and 0.5 ⁇ m or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.3 ⁇ m and 0.4 ⁇ m or less).
  • the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.5 ⁇ m and 0.6 ⁇ m or less). That is, in FIG. 3, the first range (the equivalent circle diameter is more than 0.3 ⁇ m and 0.6 ⁇ m or less) has one maximum frequency.
  • the frequency in the class having a circle equivalent diameter of more than 0.7 ⁇ m and 0.8 ⁇ m or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.6 ⁇ m and 0.7 ⁇ m or less).
  • the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.8 ⁇ m and 0.9 ⁇ m or less). That is, in FIG. 3, the second range (the equivalent circle diameter is more than 0.6 ⁇ m and 1.0 ⁇ m or less) has one maximum frequency.
  • the first maximum frequency which is the largest maximum frequency existing in the first range, is a frequency in a class having a circle equivalent diameter of more than 0.4 ⁇ m and 0.5 ⁇ m or less.
  • the ratio of the first maximum power to the total number of tungsten carbide particles is 10% or more (about 14.3%).
  • the second maximum frequency which is the largest maximum frequency existing in the second range, is a frequency in a class having a circle equivalent diameter of more than 0.7 ⁇ m and 0.8 ⁇ m or less.
  • the ratio of the second maximum power to the total number of tungsten carbide particles is 10% or more (about 12.6%).
  • the frequency in the class having a circle equivalent diameter of more than 0.5 ⁇ m and 0.6 ⁇ m or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.4 ⁇ m and 0.5 ⁇ m or less).
  • the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.6 ⁇ m and 0.7 ⁇ m or less). That is, in FIG. 4, the first range (the equivalent circle diameter is more than 0.3 ⁇ m and 0.6 ⁇ m or less) has one maximum frequency.
  • the frequency in the class having a circle equivalent diameter of more than 0.7 ⁇ m and 0.8 ⁇ m or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.6 ⁇ m and 0.7 ⁇ m or less).
  • the frequency of the class one level higher than the class to which the frequency belongs is more than 0.8 ⁇ m and 0.9 ⁇ m or less.
  • the frequency in the class having a circle equivalent diameter of more than 0.9 ⁇ m and 1.0 ⁇ m or less is one class lower than the class to which the frequency belongs (the circle equivalent diameter is more than 0.8 ⁇ m and 0.9 ⁇ m or less).
  • the equivalent circle diameter is more than 1.0 ⁇ m and 1.1 ⁇ m or less. That is, in FIG. 4, the second range (the equivalent circle diameter is more than 0.6 ⁇ m and 1.0 ⁇ m or less) has two maximum frequencies.
  • the first maximum frequency which is the largest maximum frequency existing in the first range, is a frequency in a class having a circle equivalent diameter of more than 0.5 ⁇ m and 0.6 ⁇ m or less.
  • the ratio of the first maximum power to the total number of tungsten carbide particles is 10% or more (about 13.4%).
  • the second maximum frequency which is the largest maximum frequency existing in the second range, is a frequency in a class having a circle equivalent diameter of more than 0.7 ⁇ m and 0.8 ⁇ m or less.
  • the ratio of the second maximum power to the total number of tungsten carbide particles is 10% or more (about 12.7%).
  • the frequency in the class having the equivalent circle diameter of more than 0.3 ⁇ m and 0.4 ⁇ m or less is the frequency of the class one below the class to which the frequency belongs (the equivalent circle diameter is more than 0.2 ⁇ m and 0.3 ⁇ m or less).
  • the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.4 ⁇ m and 0.5 ⁇ m or less). That is, in FIG. 5, the first range (the equivalent circle diameter is more than 0.3 ⁇ m and 0.6 ⁇ m or less) has one maximum frequency.
  • the frequency in the class having a circle equivalent diameter of more than 0.7 ⁇ m and 0.8 ⁇ m or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.6 ⁇ m and 0.7 ⁇ m or less).
  • the frequency of the class one level higher than the class to which the frequency belongs is more than 0.8 ⁇ m and 0.9 ⁇ m or less.
  • the frequency in the class having a circle equivalent diameter of more than 0.9 ⁇ m and 1.0 ⁇ m or less is one class lower than the class to which the frequency belongs (the circle equivalent diameter is more than 0.8 ⁇ m and 0.9 ⁇ m or less).
  • the equivalent circle diameter is more than 1.0 ⁇ m and 1.1 ⁇ m or less. That is, in FIG. 5, the second range (the equivalent circle diameter is more than 0.6 ⁇ m and 1.0 ⁇ m or less) has two maximum frequencies.
  • the first maximum frequency which is the largest maximum frequency existing in the first range, is a frequency in a class having a circle equivalent diameter of more than 0.3 ⁇ m and 0.4 ⁇ m or less.
  • the ratio of the first maximum power to the total number of tungsten carbide particles is 10% or more (about 11.8%).
  • the second maximum frequency which is the largest maximum frequency existing in the second range, is a frequency in a class having a circle equivalent diameter of more than 0.7 ⁇ m and 0.8 ⁇ m or less.
  • the ratio of the second maximum power to the total number of tungsten carbide particles is 10% or more (about 12.2%).
  • the frequency in the class having the equivalent circle diameter of more than 0.4 ⁇ m and 0.5 ⁇ m or less is the frequency of the class one below the class to which the frequency belongs (the equivalent circle diameter is more than 0.3 ⁇ m and 0.4 ⁇ m or less).
  • the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.5 ⁇ m and 0.6 ⁇ m or less). That is, in FIG. 6, the first range (the equivalent circle diameter is more than 0.3 ⁇ m and 0.6 ⁇ m or less) has one maximum frequency.
  • the frequency in the class having a circle equivalent diameter of more than 0.6 ⁇ m and 0.7 ⁇ m or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.5 ⁇ m and 0.6 ⁇ m or less).
  • the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.7 ⁇ m and 0.8 ⁇ m or less). That is, in FIG. 6, the second range (the equivalent circle diameter is more than 0.6 ⁇ m and 1.0 ⁇ m or less) has one maximum frequency.
  • the first maximum frequency which is the largest maximum frequency existing in the first range, is a frequency in a class having a circle equivalent diameter of more than 0.4 ⁇ m and 0.5 ⁇ m or less.
  • the ratio of the first maximum power to the total number of tungsten carbide particles is 10% or more (about 14.2%).
  • the second maximum frequency which is the largest maximum frequency existing in the second range, is a frequency in a class having a circle equivalent diameter of more than 0.6 ⁇ m and 0.7 ⁇ m or less.
  • the ratio of the second maximum power to the total number of tungsten carbide particles is 10% or more (about 12.4%).
  • the range of more than 0.4 ⁇ m and less than 0.6 ⁇ m is defined as the third range, and the range of more than 0.6 ⁇ m and less than 0.8 ⁇ m is defined as the third range.
  • the third range has a first maximum frequency and the fourth range has a second maximum frequency. According to this, the tool life is further improved.
  • the ratio of the second maximum frequency to the first maximum frequency is preferably 0.8 or more and 1.2 or less. According to this, the tool life is further improved. The reason for this is that the bonding by contact between the tungsten carbide particles is important, and when the difference between the maximum power existing in the first range and the maximum power existing in the second range becomes large, the tungsten carbide in the cemented carbide eventually becomes large. It is presumed that this is because the contact between particles is reduced.
  • the second phase contains cobalt.
  • the second phase is a bonding phase in which the tungsten carbide particles constituting the first phase are bonded 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 group elements such as nickel and dissolved substances (Cr, W, etc.) in the alloy in addition to cobalt.
  • iron group elements such as nickel and dissolved substances (Cr, W, etc.) in the alloy in addition to cobalt.
  • the cemented carbide includes a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
  • the cemented carbide preferably contains 75 area% or more and less than 100 area% of the first phase and 0 area% or more and 20 area% or less of the second phase in the image taken by the scanning electron microscope.
  • the ratio of the second phase in the cemented carbide is 20 area% or less, it is possible to suppress the dissolution of fine tungsten carbide particles having a circle equivalent diameter of 0.6 ⁇ m or less in the cobalt of the second phase. It is possible to suppress the decrease of tungsten carbide particles having a circle-equivalent diameter of more than 0.3 ⁇ m and 0.6 ⁇ m or less. In addition, the amount of cobalt exposed on the tool surface during machining is further reduced. Therefore, the tool life is further improved.
  • the cemented carbide preferably contains the second phase in an amount of 5 area% or more and 12 area% or less in the image taken by the scanning electron microscope. According to this, the hardness and wear resistance required for processing the printed circuit board can be exhibited, and the occurrence of variation in tool life can be suppressed.
  • the lower limit of the ratio of the first phase in the cemented carbide can be 75 area% or more and 85 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 75 area% or more and less than 100 area%, and 85 area% or more and 95 area% or less.
  • 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 20 area% or less and 12 area% or less.
  • the ratio of the second phase in the cemented carbide can be more than 0 area% and 20 area% or less, 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 (A3) to (C3).
  • (C3) Perform the image processing of (B3) above in five measurement fields of view.
  • 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.
  • the cemented carbide contains chromium (Cr), and the mass-based ratio of chromium to cobalt is preferably 5% or more and 10% or less. 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.
  • mass-based ratio of chromium to cobalt is 5% or more and 10% or less, precipitation of chromium carbide is unlikely to occur, and the effect of improving breakage resistance can be obtained.
  • the mass-based ratio of chromium to cobalt is 10% or less, the degree of grain growth inhibitory action becomes appropriate, and the amount of tungsten carbide particles having a circle equivalent diameter of more than 1.0 ⁇ m in the cemented carbide becomes excessive. It can be suppressed.
  • the lower limit of the mass-based ratio of chromium to cobalt is preferably 5% or more, more preferably 7% or more.
  • the mass-based ratio of chromium to cobalt is preferably 10% or less, more preferably 9% or less.
  • the mass standard of chromium with respect to cobalt can be 5% or more and 10% or less, and 7% or more and 9% or less.
  • the content of cobalt and chromium in cemented carbide is measured by ICP emission spectroscopy.
  • the mass-based content of vanadium in the cemented carbide is preferably less than 100 ppm.
  • vanadium Since vanadium has a grain growth inhibitory effect, it has been used in the production of conventional ultrafine cemented carbide. If vanadium is present during the grain growth of the tungsten carbide particles, vanadium is precipitated on the surface of the tungsten carbide particles, or vanadium intervenes in the growth surface of the tungsten carbide particles in a short period of time, so that the tungsten carbide particles grow. It is thought to be suppressed.
  • the content of vanadium in the cemented carbide is preferably 100 ppm or less, more preferably 10 ppm or less. Since the smaller the content of vanadium in the cemented carbide is, the more preferable it is, the lower limit thereof is preferably 0 ppm. In addition, vanadium of several ppm may be unintentionally detected in the manufacturing process.
  • the content of vanadium in the cemented carbide can be 0 ppm or more and 100 ppm or less, and 0 ppm or more and 10 ppm or less.
  • the content of vanadium in cemented carbide is measured by ICP emission spectroscopy.
  • 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 a raw material for the first phase, and cobalt (Co) powder, which is a raw material for the second phase, as essential raw material powders.
  • chromium carbide (Cr 3 C 2 ) powder can be prepared as a grain growth inhibitor.
  • Vanadium carbide (VC) powder can also be prepared as long as the effects of the present disclosure are exhibited.
  • As the tungsten carbide powder, cobalt powder, chromium carbide powder, and vanadium carbide powder commercially available ones can be used.
  • the tungsten carbide powder includes (a) tungsten carbide powder having an average particle size of 0.4 ⁇ m or more and 1.2 ⁇ m or less (hereinafter, also referred to as “first tungsten carbide powder”), and (b) an average particle size of 0.8 ⁇ m or more and 1.2 ⁇ m or more.
  • Tungsten carbide powder of ⁇ m or less (hereinafter, also referred to as “second tungsten carbide powder”) is prepared.
  • the first tungsten carbide powder having an average particle size smaller than the average particle size of the second tungsten carbide powder is prepared.
  • the average particle size of the raw material powder means a median diameter d50 having a diameter equivalent to a circle.
  • the average particle size is measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.
  • the average particle size of the cobalt powder can be 0.8 ⁇ m or more and 1.2 ⁇ 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 of the vanadium carbide powder can be 0.5 ⁇ m or more and 1.0 ⁇ m or less.
  • 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 first tungsten carbide powder in the mixed powder can be, for example, 30% by mass or more and 94.6% by mass or less.
  • the ratio of the second tungsten carbide powder in the mixed powder can be, for example, 30% by mass or more and 64.6% by mass or less.
  • the ratio of the cobalt powder in the mixed powder can be, for example, 2.8% by mass or more and 10% by mass or less.
  • the ratio of chromium carbide powder in the mixed powder can be, for example, 0.2% by mass or more and 1.2% by mass or less.
  • the ratio of vanadium carbide powder in the mixed powder can be, for example, 0% by mass or more and 0.2% by mass or less.
  • the mixing time can be 20 hours or more and 48 hours or less.
  • 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 the molded product obtained in the molding step to obtain a cemented carbide.
  • the sintering temperature can be a general cemented carbide sintering temperature (1350 to 1500 ° C.).
  • Cemented carbide is generally sintered at 1350 to 1500 ° C., but fine tungsten carbide particles have a large surface area and are easily dissolved in cobalt, so that an abnormal structure is likely to occur due to dissolution and reprecipitation. Therefore, in the sintering of fine tungsten carbide particles, in order to suppress dissolution and reprecipitation, sintering is performed in a low temperature region of 1350 to 1380 ° C., which has a low solid solution limit of tungsten carbide with cobalt. However, in the cemented carbide obtained by sintering in a low temperature region, the tungsten carbide particles do not grow, so the surface of the tungsten carbide particles remains crushed by crushing or mixing in the previous process. It has become. Therefore, the bonding force between the tungsten carbide particles and cobalt and the interface between the tungsten carbide particles is low, and the wear resistance and breakage resistance tend to decrease.
  • the generation of fragments of ultrafine tungsten carbide particles generated by crushing or mixing raw materials is suppressed, and the effect of suppressing grain growth by chromium is maximized. Furthermore, it has been found that abnormal grain growth can be suppressed even in a temperature range where grain growth normally occurs by providing a distribution of coarse particles and fine particles having peaks having similar particle sizes in the fine structure. .. Therefore, in the method for producing cemented carbide of the present disclosure, even if the tungsten carbide particles are sintered at a higher temperature than before, the generation of abnormal structure can be suppressed, and the interface between the tungsten carbide particles and cobalt can be suppressed. Further, by improving the bonding force at the interface between the tungsten carbide particles, it is possible to improve the wear resistance and the breaking resistance of the cemented carbide. This was newly discovered by the present inventors as a result of diligent studies.
  • the cooling step is a step of cooling the cemented carbide after the sintering is completed.
  • the cooling condition general conditions may be adopted, and there is no particular limitation.
  • 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 perpendicular 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, and the like.
  • 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.
  • Example 1 cemented carbides of Samples 1 to 24 were prepared by changing the type and compounding ratio 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 carbonized WC powder is as shown in the "Average particle size ( ⁇ m)" column of the "first WC powder” in Table 1.
  • WC tungsten carbide
  • the average particle size of cobalt (Co) powder is 1 [mu] m
  • an average particle diameter of the vanadium carbide (VC) powder was 0.8 [mu] m
  • an average particle size of chromium carbide (Cr 3 C 2) powder is 1 [mu] m.
  • Co powder, VC powder and Cr 3 C 2 powder are commercially available products.
  • the average particle size of the raw material powder is a value measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.
  • the distribution of the equivalent circle diameter of the tungsten carbide particles was measured, and the ratio based on the number of tungsten carbide particles having the equivalent circle diameter of 0.3 ⁇ m or more and 1.0 ⁇ m or less, and the existence of the first maximum frequency.
  • the class to be used the ratio of the first maximum frequency to the total number of tungsten carbide particles, the class in which the second maximum frequency exists, the ratio of the second maximum frequency to the total number of tungsten carbide particles, and the ratio of the second maximum frequency to the first maximum frequency. Calculated. Since the specific measurement method and calculation method are described in the first embodiment, the description thereof will not be repeated.
  • the maximum frequency does not exist within the first range (more than 0.3 ⁇ m and less than 0.6 ⁇ m) or the second range (more than 0.6 ⁇ m and less than 1.0 ⁇ m), it is indicated as “-”. If the maximum frequency is outside the first range (more than 0.3 ⁇ m and 0.6 ⁇ m or less) or outside the second range (more than 0.6 ⁇ m and 1.0 ⁇ m or less), the class of the maximum frequency is shown in parentheses. Shown in parentheses.
  • Samples 1, 4 and 12 do not have a maximum frequency (second maximum frequency) within the second range, and correspond to a comparative example.
  • the maximum frequency was present in the class of more than 1.0 ⁇ m and 1.1 ⁇ m or less.
  • Samples 2, 10 and 11 do not have a maximum frequency (first maximum frequency) within the first range, and correspond to a comparative example.
  • Sample 2 had a maximum frequency in a class of more than 0.2 ⁇ m and 0.3 ⁇ m or less, and the ratio of the number standard of this maximum frequency was 10.1%.

Abstract

A cemented carbide comprising: a first phase including a plurality of tungsten carbide particles; and a second phase containing cobalt, wherein when the equivalent circular diameter of each of the tungsten carbide particles is calculated by performing image processing on an image of the cemented carbide captured using a scanning electron microscope, the proportion of tungsten carbide particles having an equivalent circular diameter of 0.3-1.0 μm is at least 50% in terms of number of particles, and when the distribution of the equivalent circular diameters of the tungsten carbide particles is represented by a histogram in which the vertical axis indicates count and the horizontal axis indicates tiers, said count represents the number of tungsten carbide particles, and the tiers are formed by delimiting the equivalent circular diameter in an ascending order at an interval of 0.1 μm, and, on the horizontal axis, a range of more than 0.3 μm but not more than 0.6 μm is designated as a first range and a range of more than 0.6 μm but not more than 1.0 μm is designated as a second range, and the first range and the second range each have at least one local maximum count, and, of the local maximum counts in the first range, the proportion of tungsten carbide particles resulting in a first local maximum count that is the largest with respect to the total number of tungsten carbide particles is 10% or more, and, of the local maximum counts in the second range, the proportion of tungsten carbide particles resulting in a second local maximum count that is the largest with respect to the total number of tungsten carbide particles is 10% or more.

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 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JP-A-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影した画像に対して画像処理を行うことにより、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、前記円相当径が０．３μｍ以上１．０μｍ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５０％以上であり、
　前記炭化タングステン粒子の円相当径の分布を、度数を縦軸とし、階級を横軸とするヒストグラムで表した場合、
　前記度数は、前記炭化タングステン粒子の個数であり、
　前記階級は、前記円相当径が昇順に０．１μｍ間隔で区切られており、
　前記横軸において、０．３μｍ超０．６μｍ以下の範囲を第１範囲と規定し、０．６μｍ超１．０μｍ以下の範囲を第２範囲と規定し、
　前記第１範囲及び前記第２範囲は、それぞれ少なくとも一つの極大度数を有し、
　前記第１範囲内に存在する極大度数のうち、最も大きい第１極大度数の前記炭化タングステン粒子の総数に対する割合は１０％以上であり、
　前記第２範囲内に存在する極大度数のうち、最も大きい第２極大度数の前記炭化タングステン粒子の総数に対する割合は１０％以上である、超硬合金である。 The cemented carbide of the present disclosure is a cemented carbide including a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
When the equivalent circle diameter of each of the tungsten carbide particles is calculated by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the equivalent circle diameter is 0.3 μm or more and 1.0 μm. The ratio based on the number of the tungsten carbide particles below is 50% or more.
When the distribution of the equivalent circle diameter of the tungsten carbide particles is represented by a histogram with the frequency as the vertical axis and the class as the horizontal axis,
The frequency is the number of the tungsten carbide particles, and is
In the class, the equivalent circle diameter is divided in ascending order at intervals of 0.1 μm.
On the horizontal axis, a range of more than 0.3 μm and 0.6 μm or less is defined as the first range, and a range of more than 0.6 μm and 1.0 μm or less is defined as the second range.
The first range and the second range each have at least one maximum frequency.
Among the maximum powers existing in the first range, the ratio of the largest first maximum power to the total number of the tungsten carbide particles is 10% or more.
It is a cemented carbide in which the ratio of the largest second maximum power to the total number of the tungsten carbide particles among the maximum powers existing in the second range is 10% or more.
　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 of the present disclosure is a cutting tool having 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 of the cemented carbide of the present disclosure taken by a scanning electron microscope. 図２は、図１の撮影画像に対して画像処理を行って得られた画像である。FIG. 2 is an image obtained by performing image processing on the captured image of FIG. 図３は、本開示の超硬合金中の炭化タングステン粒子の円相当径の分布の一例を示す図である。FIG. 3 is a diagram showing an example of the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure. 図４は、本開示の超硬合金中の炭化タングステン粒子の円相当径の分布の他の一例を示す図である。FIG. 4 is a diagram showing another example of the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure. 図５は、本開示の超硬合金中の炭化タングステン粒子の円相当径の分布の他の一例を示す図である。FIG. 5 is a diagram showing another example of the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure. 図６は、本開示の超硬合金中の炭化タングステン粒子の円相当径の分布の他の一例を示す図である。FIG. 6 is a diagram showing another example of the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure.
　[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。 [Issues to be resolved 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 the printed circuit board, a technique for improving the heat resistance of the resin and the glass filler constituting the printed circuit board has 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, an object of the present disclosure is to provide a cemented carbide capable of extending the life of a tool when used as a tool material, particularly even 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影した画像に対して画像処理を行うことにより、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、前記円相当径が０．３μｍ以上１．０μｍ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５０％以上であり、
　前記炭化タングステン粒子の円相当径の分布を、度数を縦軸とし、階級を横軸とするヒストグラムで表した場合、
　前記度数は、前記炭化タングステン粒子の個数であり、
　前記階級は、前記円相当径が昇順に０．１μｍ間隔で区切られており、
　前記横軸において、０．３μｍ超０．６μｍ以下の範囲を第１範囲と規定し、０．６μｍ超１．０μｍ以下の範囲を第２範囲と規定し、
　前記第１範囲及び前記第２範囲は、それぞれ少なくとも一つの極大度数を有し、
　前記第１範囲内に存在する極大度数のうち、最も大きい第１極大度数の前記炭化タングステン粒子の総数に対する割合は１０％以上であり、
　前記第２範囲内に存在する極大度数のうち、最も大きい第２極大度数の前記炭化タングステン粒子の総数に対する割合は１０％以上である、超硬合金である。 [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 including a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
When the equivalent circle diameter of each of the tungsten carbide particles is calculated by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the equivalent circle diameter is 0.3 μm or more and 1.0 μm. The ratio based on the number of the tungsten carbide particles below is 50% or more.
When the distribution of the equivalent circle diameter of the tungsten carbide particles is represented by a histogram with the frequency as the vertical axis and the class as the horizontal axis,
The frequency is the number of the tungsten carbide particles, and is
In the class, the equivalent circle diameter is divided in ascending order at intervals of 0.1 μm.
On the horizontal axis, a range of more than 0.3 μm and 0.6 μm or less is defined as the first range, and a range of more than 0.6 μm and 1.0 μm or less is defined as the second range.
The first range and the second range each have at least one maximum frequency.
Among the maximum powers existing in the first range, the ratio of the largest first maximum power to the total number of the tungsten carbide particles is 10% or more.
It is a cemented carbide in which the ratio of the largest second maximum power to the total number of the tungsten carbide particles among the maximum powers existing in the second range is 10% or more.
　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 of the present disclosure makes it possible to extend the life of the tool, especially in the microfabrication of printed circuit boards.
　（２）前記超硬合金は、走査型電子顕微鏡で撮影した画像において、前記第１相を７５面積％以上１００面積％未満、かつ、前記第２相を０体積％超２０面積％以下含むことが好ましい。これによると、工具寿命が更に向上する。 (2) The cemented carbide contains 75 area% or more and less than 100 area% of the first phase and more than 0% by volume and 20 area% or less of the second phase in an image taken by a scanning electron microscope. Is preferable. According to this, the tool life is further improved.
　（３）前記超硬合金は、走査型電子顕微鏡で撮影した画像において、前記第２相を５面積％以上１２面積％以下含むことが好ましい。これによると、工具寿命が更に向上する。 (3) The cemented carbide preferably contains the second phase in an amount of 5 area% or more and 12 area% or less in an image taken with a scanning electron microscope. According to this, the tool life is further improved.
　（４）前記超硬合金は、クロムを含み、
　前記コバルトに対する前記クロムの質量基準の割合は、５％以上１０％以下であることが好ましい。これによると、超硬合金の耐折損性が向上し、工具寿命が更に向上する。 (4) The cemented carbide contains chromium and contains chromium.
The mass-based ratio of the chromium to the cobalt is preferably 5% or more and 10% or less. According to this, the breakage resistance of the cemented carbide is improved, and the tool life is further improved.
　（５）前記超硬合金がバナジウムを含む場合、前記超硬合金の前記バナジウムの質量基準の含有率は、１００ｐｐｍ未満であることが好ましい。これによると、超硬合金の強度が向上する。 (5) When the cemented carbide contains vanadium, the mass-based content of the vanadium in the cemented carbide is preferably less than 100 ppm. According to this, the strength of the cemented carbide is improved.
　（６）前記円相当径が０．３μｍ未満である前記炭化タングステン粒子の個数基準の割合は７％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。 (6) The ratio based on the number of the tungsten carbide particles having the equivalent circle diameter of less than 0.3 μm is preferably 7% or less. According to this, the tool life is further improved.
　（７）前記第１極大度数に対する、前記第２極大度数の割合は、０．８以上１．２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。 (7) The ratio of the second maximum frequency to the first maximum frequency is preferably 0.8 or more and 1.2 or less. According to this, the tool life is further improved.
　（８）前記横軸において、０．４μｍ超０．６μｍ以下の範囲を第３範囲と規定し、０．６μｍ超０．８μｍ以下の範囲を第４範囲と規定した場合、
　前記第３範囲は、前記第１極大度数を有し、
　前記第４範囲は、前記第２極大度数を有することが好ましい。これによると、工具寿命が更に向上する。 (8) When the range of more than 0.4 μm and 0.6 μm or less is defined as the third range and the range of more than 0.6 μm and 0.8 μm or less is defined as the fourth range on the horizontal axis.
The third range has the first maximal frequency and
The fourth range preferably has the second maximum frequency. According to this, the tool life is further improved.
　（９）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。 (9) 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.
　（１０）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。 (10) 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 a printed circuit board.
　［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 parts or equivalent parts. Further, the dimensional relationships 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 relationships.
　本明細書において「Ａ～Ｂ」という形式の表記は、特に定義のない場合、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) unless otherwise defined, and the unit is not described in A and the unit is described only in B. If so, the unit of A 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。 When a compound or the like is represented by a chemical formula in the present specification, 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ところ、下記の知見を得た。 In order to obtain a cemented carbide that enables a longer tool life, 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. As a result of the examination, the following findings were obtained.
　プリント回路基板に用いられる基板としては、ガラス繊維を布状に編んだガラス織布にエポキシ樹脂を含浸させたガラスエポキシ基板や、ガラス織布にポリイミド樹脂を含浸させたガラスポリイミド基板等が用いられている。 As the substrate used for the printed circuit substrate, a glass epoxy substrate in which a glass woven cloth in which glass fibers are woven into a cloth shape is impregnated with an epoxy resin, a glass polyimide substrate in which a glass woven cloth is impregnated with a polyimide resin, or the like is used. ing.
　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ところ、プリント回路基板中の樹脂やガラス繊維により、超硬合金の結合相であるコバルトが局所的に摩耗し、炭化タングステン粒子（以下、「ＷＣ粒子」とも記す。）が露出し、該ＷＣ粒子が脱落することが確認された。 When the printed circuit board was finely processed using a conventional tool made of fine-grained cemented carbide, cobalt, which is the bonding phase of the cemented carbide, was locally worn by the resin and glass fibers in the printed circuit board, resulting in tungsten carbide. It was confirmed that the particles (hereinafter, also referred to as “WC particles”) were exposed and the WC particles were shed.
　よって、本発明者らは、長い工具寿命を達成するためには、加工中に工具表面に露出するコバルト（Ｃｏ）の量を減少させること、及び、ＷＣ粒子同士の結合力を高めることが重要であると推測した。また、本発明者らは、超硬合金中のＷＣ粒子がプリント回路基板の切削に直接的に関与することから、微細加工の精度を維持するためには、ＷＣ粒子が工具表面に連続的及び緻密に現れることも重要であると推測した。 Therefore, in order to achieve a long tool life, it is important for the present inventors to reduce the amount of cobalt (Co) exposed on the tool surface during machining and to increase the bonding force between WC particles. I guessed that. In addition, since the WC particles in the cemented carbide are directly involved in the cutting of the printed circuit board, the present inventors continuously apply the WC particles to the tool surface in order to maintain the accuracy of micromachining. I speculated that it is also important to appear precisely.
　Ｃｏが存在するＷＣ同士の界面を減らし、加工中に工具表面に露出するコバルトの量を減少させるためには、超硬合金中のＷＣ粒子の粒径を大きくし、コバルト量を減少させることが考えられる。しかし、ＷＣ粒子の粒径を大きくし、コバルト量を減少させると、強度が低下し、加工中に折損が発生しやすくなる。 In order to reduce the interface between WCs in which Co is present and reduce the amount of cobalt exposed on the tool surface during machining, it is possible to increase the particle size of the WC particles in the cemented carbide and reduce the amount of cobalt. Conceivable. However, if the particle size of the WC particles is increased and the amount of cobalt is reduced, the strength is lowered and breakage is likely to occur during processing.
　上記の知見に基づき、本発明者らは鋭意検討の結果、ＷＣ粒子の粒径を制御することにより、ＷＣ粒子間の結合力を高めることが出来ることを新たに見出し、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。 Based on the above findings, as a result of diligent studies, the present inventors have newly found that the bonding force between WC particles can be enhanced by controlling the particle size of WC particles, and the cemented carbide of the present disclosure is disclosed. Was completed. Details of the cemented carbide of the present disclosure and the cutting tool provided with the cemented carbide 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影した画像に対して画像処理を行うことにより、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、円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は５０％以上であり、炭化タングステン粒子の円相当径の分布を、度数を縦軸とし、階級を横軸とするヒストグラムで表した場合、度数は、炭化タングステン粒子の個数であり、階級は、前記円相当径が昇順に０．１μｍ間隔で区切られており、横軸において、０．３μｍ超０．６μｍ以下の範囲を第１範囲と規定し、０．６μｍ超１．０μｍ以下の範囲を第２範囲と規定し、第１範囲及び第２範囲は、それぞれ少なくとも一つの極大度数を有し、第１範囲内に存在する極大度数のうち、最も大きい第１極大度数の炭化タングステン粒子の総数に対する割合は１０％以上であり、第２範囲内に存在する極大度数のうち、最も大きい第２極大度数の炭化タングステン粒子の総数に対する割合は１０％以上である、超硬合金である。 [Embodiment 1: Cemented Carbide]
The cemented carbide of the present disclosure is a cemented carbide including a first phase composed of a plurality of tungsten carbide particles and a second phase containing cobalt.
When the equivalent circle diameter of each of the tungsten carbide particles is calculated by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the equivalent circle diameter is 0.3 μm or more and 1.0 μm or less. The ratio based on the number of tungsten carbide particles is 50% or more, and when the distribution of the equivalent circle diameter of the tungsten carbide particles is represented by a histogram with the frequency as the vertical axis and the class as the horizontal axis, the frequency is the tungsten carbide particles. In the class, the equivalent circle diameter is divided in ascending order at 0.1 μm intervals, and the range of more than 0.3 μm and 0.6 μm or less is defined as the first range on the horizontal axis, and is 0.6 μm. The range of super 1.0 μm or less is defined as the second range, and the first range and the second range each have at least one maximum frequency, and the first maximum frequency existing in the first range is the largest. The ratio of the maximum frequency to the total number of tungsten carbide particles is 10% or more, and the ratio of the maximum second maximum frequency to the total number of tungsten carbide particles existing in the second range is 10% or more. It is a cemented carbide.
　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）及び（ｉｉ）の通りと推察される。 When used as a tool material, the cemented carbide of 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 shown in (i) and (ii) below.
　（ｉ）本開示の超硬合金において、円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は５０％以上である。これによると、超硬合金組織が均質となり、使用に伴う微細加工の精度の低下を抑制することができ、工具寿命が長くなる。 (I) 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 more and 1.0 μm or less is 50% or more. According to this, the cemented carbide structure becomes homogeneous, it is possible to suppress a decrease in the accuracy of microfabrication due to use, and the tool life is extended.
　（ｉｉ）本開示の超硬合金において、ＷＣ粒子の円相当径の分布は、粒径０．３μｍ超０．６μｍ以下の範囲（第１範囲）及び０．６μｍ超１．０μｍ以下の範囲（第２範囲）のそれぞれに、少なくとも一つの極大度数を有する。第１範囲内の最大の極大度数（第１極大度数）及び第２範囲内の最大の極大度数（第２極大度数）のそれぞれは、超硬合金中の炭化タングステン粒子の総数に対する割合が１０％以上である。 (Ii) In the cemented carbide of the present disclosure, the distribution of the equivalent circle diameter of the WC particles is in the range of the particle size of more than 0.3 μm and not more than 0.6 μm (first range) and the range of more than 0.6 μm and not more than 1.0 μm (the first range). Each of the second range) has at least one maximum frequency. The maximum maximum power in the first range (first maximum power) and the maximum maximum power in the second range (second maximum power) are each 10% of the total number of tungsten carbide particles in the cemented carbide. That is all.
　これによると、超硬合金は、円相当径の大きいＷＣ粒子が骨格となり、該ＷＣ粒子間に、円相当径の小さいＷＣ粒子が隙間を埋める形態の組織を有する。該超硬合金ではＷＣ粒子同士が結合しているため、ＷＣ粒子の脱落が抑制されることで耐摩耗性が向上する。更に、摩耗が抑制されることで、切削抵抗の増加が抑制され耐折損性が向上する。よって工具寿命が長くなる。 According to this, the cemented carbide has a structure in which WC particles having a large circle-equivalent diameter form a skeleton, and WC particles having a small circle-equivalent diameter fill a gap between the WC particles. Since the WC particles are bonded to each other in the cemented carbide, the wear resistance is improved by suppressing the WC particles from falling off. Further, by suppressing wear, an increase in cutting resistance is suppressed and breakage resistance is improved. Therefore, the tool life is extended.
　更に、該超硬合金では、加工中に工具表面に露出するコバルト量が、従来の微粒超硬合金よりも低減されている。このため、加工中のコバルトの摩耗が生じ難く、ＷＣ粒子の脱落を抑制でき、工具寿命が長くなる。 Furthermore, in the cemented carbide, the amount of cobalt exposed on the tool surface during machining is reduced as compared with the conventional fine-grained cemented carbide. Therefore, the cobalt is less likely to be worn during processing, the WC particles can be suppressed from falling off, and the tool life is extended.
　＜第１相＞
　（第１相の組成）
　第１相は、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 tungsten carbide particles. Here, tungsten carbide includes not only "pure WC (WC containing no impurity elements, WC in which impurity elements are below the detection limit)", but also "as long as the effects of the present disclosure are not impaired.""WC" in which other impurity elements are intentionally or unavoidably 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 impurity elements in the first phase is measured by ICP emission spectrometry (Inductively Coupled Plasma) Emission Spectroscopy (measuring apparatus: Shimadzu Corporation "ICPS-8100" (trademark)).
　（炭化タングステン粒子の円相当径の分布）
　炭化タングステン粒子は、その円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合が５０％以上である。これによると、超硬合金組織が均質となり、使用に伴う微細加工の精度の低下を抑制することができ、工具寿命が長くなる。 (Distribution of equivalent circle diameter of tungsten carbide particles)
The ratio of the number-based number of tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more. According to this, the cemented carbide structure becomes homogeneous, it is possible to suppress a decrease in the accuracy of microfabrication due to use, and the tool life is extended.
　超硬合金中のコバルト量が一定の場合、円相当径が１μｍ超の粗粒の炭化タングステン粒子の割合が増加すると、硬度が低下して耐摩耗性が低下する傾向があり、円相当径が０．３μｍ未満の微粒の炭化タングステン粒子の割合が増加すると、炭化タングステン粒子の脱落が進み耐摩耗性が低下する傾向がある。本開示の超硬合金では、円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合が５０％以上であるため、優れた耐摩耗性を有することができる。 When the amount of cobalt in the cemented carbide is constant, if the proportion of coarse-grained tungsten carbide particles having a circle-equivalent diameter of more than 1 μm increases, the hardness tends to decrease and the wear resistance tends to decrease, resulting in a circle-equivalent diameter. When the proportion of fine tungsten carbide particles smaller than 0.3 μm increases, the tungsten carbide particles tend to fall off and the wear resistance tends to decrease. In the cemented carbide of the present disclosure, since the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more, excellent wear resistance can be obtained.
　円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は、超硬合金組織の均質性向上の観点から、５０％以上であり、７０％以上が好ましい。円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合の上限は特に限定されないが、例えば、１００％以下、９０％以下、８０％以下とすることができる。円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は、５０％以上１００％以下、６０％以上９０％以下、７０％以上８０％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 more and 1.0 μm or less is 50% or more, preferably 70% or more, from the viewpoint of improving the homogeneity of the cemented carbide structure. The upper limit of the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less is not particularly limited, but may be, for example, 100% or less, 90% or less, or 80% or less. The ratio based on the number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less can be 50% or more and 100% or less, 60% or more and 90% or less, and 70% or more and 80% or less.
　円相当径が０．３μｍ未満である炭化タングステン粒子の個数基準の割合は７％以下であることが好ましい。円相当径が０．３μｍ未満である炭化タングステン粒子は、超硬合金の強度の向上や、加工中に工具表面に露出するコバルト量の低減への寄与が小さい。従って、円相当径が０．３μｍ未満である炭化タングステン粒子の個数基準の割合を低減することで、工具寿命が更に長くなる。 The ratio based on the number of tungsten carbide particles having a circle equivalent diameter of less than 0.3 μm is preferably 7% or less. Tungsten carbide particles having a circle-equivalent diameter of less than 0.3 μm have a small contribution to improving the strength of cemented carbide and reducing the amount of cobalt exposed on the tool surface during machining. Therefore, by reducing the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of less than 0.3 μm, the tool life is further extended.
　円相当径が０．３μｍ未満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７％以下が好ましく、０％以上５％以下が更に好ましい。また、円相当径が０．２μｍ未満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３％以下が好ましい。 The ratio based on the number of tungsten carbide particles having a circle equivalent diameter of less than 0.3 μm is preferably 0% or more and 7% or less, and more preferably 0% or more and 5% or less. Further, the ratio based on the number of tungsten carbide particles having a circle equivalent diameter of less than 0.2 μm is preferably 0% or more and 3% 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) Mirror finish any surface or any cross section of cemented carbide. 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で撮影する。観察倍率は５０００倍とする。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。図１の右下のスケールにおいて、１目盛は１μｍを示す。 (B1) Photograph the machined surface of cemented carbide with a scanning electron microscope. The observation magnification is 5000 times. FIG. 1 shows an example of an image of the cemented carbide of the present disclosure taken with a scanning electron microscope. On the lower right scale of FIG. 1, one scale indicates 1 μm.
　（Ｃ１）上記（Ｂ１）で得られた撮影画像をコンピュータに取り込み、画像解析ソフトウェア（ＩｍａｇｅＪ：https://imagej.nih.gov/ij/）を用いて画像処理を行い、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画像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。図２の右下のスケールにおいて、１目盛は１μｍを示す。 (C1) The captured image obtained in (B1) above is taken into a computer, image processing is performed using image analysis software (ImageJ: https://imagej.nih.gov/ij/), and a circle of tungsten carbide particles. The equivalent diameter (Heywood diameter: equivalent area circle equivalent diameter) is calculated. The first phase composed of tungsten carbide particles and the second phase containing cobalt can be distinguished by the shade of color in the photographed image. An image obtained by performing image processing on the captured image of FIG. 1 is shown in FIG. In FIG. 2, the black region is the first phase and the white region is the second phase. White lines indicate grain boundaries. On the lower right scale of FIG. 2, one scale indicates 1 μm.
　本明細書において、超硬合金における円相当径が０．３μｍ以上１．０μｍ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。
　（Ｄ１）上記（Ｃ１）の画像処理を３つの測定視野で行う。１つの測定視野の大きさは、縦２５．３μｍ×幅１７．６μｍの矩形とする。 In the present specification, the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less in the cemented carbide is calculated by the following procedures (D1) and (E1).
(D1) The image processing of the above (C1) is performed in 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以上１．０μｍ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。これらの平均を超硬合金における円相当径が０．３μｍ以上１．０μｍ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 a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less 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 circle-equivalent diameter of 0.3 μm or more and 1.0 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以上１．０μｍ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 measures, as long as the measurement is performed on the same sample, the ratio of the number-based number of tungsten carbide particles having a circle equivalent diameter of 0.3 μm or more and 1.0 μm or less in the cemented carbide is selected as the measurement field. It was confirmed that even if the measurement results were changed multiple times, the variation in the measurement results was small, and even if the measurement field was set arbitrarily, it would not be arbitrary.
　本開示の超硬合金に含まれる炭化タングステン粒子の円相当径の分布は下記（ａ）を満たす。さらに本開示の超硬合金に含まれる炭化タングステン粒子の円相当径の分布を、度数を縦軸とし、階級を横軸とするヒストグラムで表した場合、下記（ｂ）及び（ｃ）を満たす。ここで、度数は、炭化タングステン粒子の個数であり、階級は、前記円相当径が昇順に０．１μｍ間隔で区切られている。 The distribution of the equivalent circle diameter of the tungsten carbide particles contained in the cemented carbide of the present disclosure satisfies the following (a). Further, when the distribution of the equivalent circle diameters of the tungsten carbide particles contained in the cemented carbide of the present disclosure is represented by a histogram having the frequency as the vertical axis and the class as the horizontal axis, the following (b) and (c) are satisfied. Here, the frequency is the number of tungsten carbide particles, and the class is divided by 0.1 μm intervals in ascending order of the equivalent circle diameters.
　（ａ）円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は５０％以上である。 (A) The ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more.
　（ｂ）横軸において、０．３μｍ超０．６μｍ以下の範囲を第１範囲と規定し、０．６μｍ超１．０μｍ以下の範囲を第２範囲と規定した場合、第１範囲及び第２範囲は、それぞれ少なくとも一つの極大度数を有する。 (B) On the horizontal axis, when the range of more than 0.3 μm and 0.6 μm or less is defined as the first range and the range of more than 0.6 μm and 1.0 μm or less is defined as the second range, the first range and the second range are defined. Each range has at least one maximum frequency.
　（ｃ）第１範囲内に存在する極大度数のうち、最も大きい第１極大度数の炭化タングステン粒子の総数に対する割合は１０％以上であり、第２範囲内に存在する極大度数のうち、最も大きい第２極大度数の炭化タングステン粒子の総数に対する割合は１０％以上である。 (C) Among the maximum powers existing in the first range, the ratio of the largest first maximum power to the total number of tungsten carbide particles is 10% or more, which is the largest among the maximum powers existing in the second range. The ratio to the total number of tungsten carbide particles having the second maximum frequency is 10% or more.
　本明細書において、ヒストグラムは下記（Ａ２）及び（Ｂ２）の手順で作製される。 In the present specification, the histogram is prepared by the following procedures (A2) and (B2).
　（Ａ２）上記の炭化タングステン粒子の円相当径の測定方法に記載される（Ａ１）～（Ｃ１）の手順により、炭化タングステン粒子の円相当径を算出する。炭化タングステン粒子の円相当径の測定は、３つの測定視野で行う。 (A2) The equivalent circle diameter of the tungsten carbide particles is calculated by the procedure (A1) to (C1) described in the above method for measuring the equivalent circle diameter of the tungsten carbide particles. The measurement of the equivalent circle diameter of the tungsten carbide particles is performed in three measurement fields.
　（Ｂ２）３つの測定視野で測定された全ての炭化タングステン粒子の円相当径に基づき、度数を縦軸とし、階級を横軸とするヒストグラムを作成する。度数は、炭化タングステン粒子の個数であり、階級は、円相当径が昇順に０．１μｍ間隔で区切られている。 (B2) Based on the circle-equivalent diameters of all the tungsten carbide particles measured in the three measurement fields of view, a histogram is created with the frequency as the vertical axis and the class as the horizontal axis. The frequency is the number of tungsten carbide particles, and the class is divided into circles in ascending order at intervals of 0.1 μm.
　本明細書において、極大度数とは、その度数が、その度数の属する階級よりも一つ下（円相当径が小さい側）の階級の度数、及び、その度数の属する階級よりも一つ上（円相当径が大きい側）の階級の度数のいずれよりも大きいことを意味する。 In the present specification, the maximum frequency is the frequency of a class whose frequency is one lower than the class to which the frequency belongs (the side having a smaller equivalent circle diameter), and the frequency of the class to which the frequency belongs (one higher than the class to which the frequency belongs (). It means that it is larger than any of the frequencies of the class (on the side with the larger equivalent diameter of the circle).
　なお、極大度数の属する階級よりも一つ下の階級、及び、極大度数の属する階級よりも一つ上の階級は、第１範囲外又は第２範囲外の階級であってもよい。具体的には、第１範囲内の極大度数の属する階級が０．３μｍ超０．４μｍ以下の場合、一つ下の階級は第１範囲外の０．２μｍ超０．３μｍ以下となる。第２範囲内の極大度数の属する階級が０．９μｍ超１．０μｍ以下の場合、一つ上の階級は第２範囲外の１．０μｍ超１．１μｍ以下となる。 Note that the class one level below the class to which the maximum frequency belongs and the class one level above the class to which the maximum frequency belongs may be a class outside the first range or a class outside the second range. Specifically, when the class to which the maximum frequency belongs in the first range is more than 0.3 μm and 0.4 μm or less, the next lower class is more than 0.2 μm and 0.3 μm or less outside the first range. When the class to which the maximum frequency belongs in the second range is more than 0.9 μm and 1.0 μm or less, the class one level higher is more than 1.0 μm and 1.1 μm or less outside the second range.
　上記（ａ）～（ｃ）を満たすことにより、使用に伴う微細加工の精度の低下を抑制することができ、強度が向上し、耐折損性が向上し、ＷＣ粒子の脱落を抑制でき、工具寿命が長くなる。 By satisfying the above (a) to (c), it is possible to suppress a decrease in the accuracy of microfabrication due to use, improve strength, improve breakage resistance, suppress WC particles from falling off, and use a tool. The life is extended.
　上記（ａ）～（ｃ）について、図３～図６を用いて説明する。図３～図６は、それぞれ本開示の超硬合金中の炭化タングステン粒子の円相当径の分布を示す図の一例である。図３～図６では、横軸は円相当径を昇順に０．１μｍ間隔で区切った階級を示し、縦軸は全タングステン粒子に対する各階級に属するタングステン粒子の個数基準の割合（％）を示す。 The above (a) to (c) will be described with reference to FIGS. 3 to 6. 3 to 6 are examples of diagrams showing the distribution of the equivalent circle diameters of the tungsten carbide particles in the cemented carbide of the present disclosure, respectively. In FIGS. 3 to 6, the horizontal axis shows the class in which the equivalent circle diameter is divided in ascending order at intervals of 0.1 μm, and the vertical axis shows the ratio (%) of the number of tungsten particles belonging to each class to all the tungsten particles. ..
　図３～図６において、「Ｃ～Ｄ」という形式の表記は、Ｃ超Ｄ以下を意味する。具体的には、図３～図６の横軸の「０～０．１」という表記は、０μｍ超０．１μｍ以下を意味し、「０．１～０．２」という表記は、０．１μｍ超０．２μｍ以下を意味する。 In FIGS. 3 to 6, the notation in the form of "C to D" means C super D or less. Specifically, the notation "0 to 0.1" on the horizontal axis of FIGS. 3 to 6 means more than 0 μm and 0.1 μm or less, and the notation “0.1 to 0.2” means 0. It means more than 1 μm and 0.2 μm or less.
　図３～図６の形状は、横軸の階級の規定が同一で、かつ、縦軸の度数を炭化タングステン粒子の個数とした場合のヒストグラムの形状と見做すことが出来る。従って、図３～図６の形状を用いて、上記（ａ）～（ｃ）について説明することができる。図３～図６では、縦軸は全タングステン粒子に対する各階級に属するタングステン粒子の個数基準の割合（％）を示すが、以下では、説明を容易にするために、図３～図６の縦軸を、度数と表記する場合がある。 The shapes of FIGS. 3 to 6 can be regarded as the shape of the histogram when the rules of the class on the horizontal axis are the same and the frequency on the vertical axis is the number of tungsten carbide particles. Therefore, the above (a) to (c) can be described using the shapes of FIGS. 3 to 6. In FIGS. 3 to 6, the vertical axis shows the ratio (%) of the number of tungsten particles belonging to each class to the total tungsten particles. The axis may be referred to as frequency.
　（図３）
　図３では、円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は５０％以上（約７２％）である。従って、図３で示される炭化タングステン粒子の円相当径の分布は、上記（ａ）を満たす。 (Fig. 3)
In FIG. 3, the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more (about 72%). Therefore, the distribution of the equivalent circle diameters of the tungsten carbide particles shown in FIG. 3 satisfies the above (a).
　図３では、円相当径が０．４μｍ超０．５μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．３μｍ超０．４μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が０．５μｍ超０．６μｍ以下）の度数よりも大きい。すなわち、図３では、第１範囲（円相当径が０．３μｍ超０．６μｍ以下）は一つの極大度数を有する。 In FIG. 3, the frequency in the class having a circle equivalent diameter of more than 0.4 μm and 0.5 μm or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.3 μm and 0.4 μm or less). , And the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.5 μm and 0.6 μm or less). That is, in FIG. 3, the first range (the equivalent circle diameter is more than 0.3 μm and 0.6 μm or less) has one maximum frequency.
　図３では、円相当径が０．７μｍ超０．８μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．６μｍ超０．７μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が０．８μｍ超０．９μｍ以下）の度数よりも大きい。すなわち、図３では、第２範囲（円相当径が０．６μｍ超１．０μｍ以下）は一つの極大度数を有する。 In FIG. 3, the frequency in the class having a circle equivalent diameter of more than 0.7 μm and 0.8 μm or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.6 μm and 0.7 μm or less). , And the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.8 μm and 0.9 μm or less). That is, in FIG. 3, the second range (the equivalent circle diameter is more than 0.6 μm and 1.0 μm or less) has one maximum frequency.
　上記より、図３で示される炭化タングステン粒子の円相当径の分布は、上記（ｂ）を満たす。 From the above, the distribution of the equivalent circle diameter of the tungsten carbide particles shown in FIG. 3 satisfies the above (b).
　図３において、第１範囲内に存在する最も大きい極大度数である第１極大度数は、円相当径が０．４μｍ超０．５μｍ以下の階級における度数である。該第１極大度数の炭化タングステン粒子の総数に対する割合は１０％以上（約１４．３％）である。 In FIG. 3, the first maximum frequency, which is the largest maximum frequency existing in the first range, is a frequency in a class having a circle equivalent diameter of more than 0.4 μm and 0.5 μm or less. The ratio of the first maximum power to the total number of tungsten carbide particles is 10% or more (about 14.3%).
　図３において、第２範囲内に存在する最も大きい極大度数である第２極大度数は、円相当径が０．７μｍ超０．８μｍ以下の階級における度数である。該第２極大度数の炭化タングステン粒子の総数に対する割合は１０％以上（約１２．６％）である。 In FIG. 3, the second maximum frequency, which is the largest maximum frequency existing in the second range, is a frequency in a class having a circle equivalent diameter of more than 0.7 μm and 0.8 μm or less. The ratio of the second maximum power to the total number of tungsten carbide particles is 10% or more (about 12.6%).
　上記より、図３で示される炭化タングステン粒子の円相当径の分布は、上記（ｃ）を満たす。 From the above, the distribution of the equivalent circle diameter of the tungsten carbide particles shown in FIG. 3 satisfies the above (c).
　（図４）
　図４では、円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は５０％以上（約７２．１％）である。従って、図４で示される炭化タングステン粒子の円相当径の分布は、上記（ａ）を満たす。 (Fig. 4)
In FIG. 4, the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more (about 72.1%). Therefore, the distribution of the equivalent circle diameters of the tungsten carbide particles shown in FIG. 4 satisfies the above (a).
　図４では、円相当径が０．５μｍ超０．６μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．４μｍ超０．５μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が０．６μｍ超０．７μｍ以下）の度数よりも大きい。すなわち、図４では、第１範囲（円相当径が０．３μｍ超０．６μｍ以下）は一つの極大度数を有する。 In FIG. 4, the frequency in the class having a circle equivalent diameter of more than 0.5 μm and 0.6 μm or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.4 μm and 0.5 μm or less). , And the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.6 μm and 0.7 μm or less). That is, in FIG. 4, the first range (the equivalent circle diameter is more than 0.3 μm and 0.6 μm or less) has one maximum frequency.
　図４では、円相当径が０．７μｍ超０．８μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．６μｍ超０．７μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が０．８μｍ超０．９μｍ以下）の度数よりも大きい。また、図４では、円相当径が０．９μｍ超１．０μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．８μｍ超０．９μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が１．０μｍ超１．１μｍ以下）の度数よりも大きい。すなわち、図４では、第２範囲（円相当径が０．６μｍ超１．０μｍ以下）は二つの極大度数を有する。 In FIG. 4, the frequency in the class having a circle equivalent diameter of more than 0.7 μm and 0.8 μm or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.6 μm and 0.7 μm or less). , And the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.8 μm and 0.9 μm or less). Further, in FIG. 4, the frequency in the class having a circle equivalent diameter of more than 0.9 μm and 1.0 μm or less is one class lower than the class to which the frequency belongs (the circle equivalent diameter is more than 0.8 μm and 0.9 μm or less). It is larger than the frequency of the frequency and the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 1.0 μm and 1.1 μm or less). That is, in FIG. 4, the second range (the equivalent circle diameter is more than 0.6 μm and 1.0 μm or less) has two maximum frequencies.
　上記より、図４で示される炭化タングステン粒子の円相当径の分布は、上記（ｂ）を満たす。 From the above, the distribution of the equivalent circle diameter of the tungsten carbide particles shown in FIG. 4 satisfies the above (b).
　図４において、第１範囲内に存在する最も大きい極大度数である第１極大度数は、円相当径が０．５μｍ超０．６μｍ以下の階級における度数である。該第１極大度数の炭化タングステン粒子の総数に対する割合は１０％以上（約１３．４％）である。 In FIG. 4, the first maximum frequency, which is the largest maximum frequency existing in the first range, is a frequency in a class having a circle equivalent diameter of more than 0.5 μm and 0.6 μm or less. The ratio of the first maximum power to the total number of tungsten carbide particles is 10% or more (about 13.4%).
　図４において、第２範囲内に存在する最も大きい極大度数である第２極大度数は、円相当径が０．７μｍ超０．８μｍ以下の階級における度数である。該第２極大度数の炭化タングステン粒子の総数に対する割合は１０％以上（約１２．７％）である。 In FIG. 4, the second maximum frequency, which is the largest maximum frequency existing in the second range, is a frequency in a class having a circle equivalent diameter of more than 0.7 μm and 0.8 μm or less. The ratio of the second maximum power to the total number of tungsten carbide particles is 10% or more (about 12.7%).
　上記より、図４で示される炭化タングステン粒子の円相当径の分布は、上記（ｃ）を満たす。 From the above, the distribution of the equivalent circle diameter of the tungsten carbide particles shown in FIG. 4 satisfies the above (c).
　（図５）
　図５では、円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は５０％以上（約７３．５％）である。従って、図５で示される炭化タングステン粒子の円相当径の分布は、上記（ａ）を満たす。 (Fig. 5)
In FIG. 5, the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more (about 73.5%). Therefore, the distribution of the equivalent circle diameters of the tungsten carbide particles shown in FIG. 5 satisfies the above (a).
　図５では、円相当径が０．３μｍ超０．４μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．２μｍ超０．３μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が０．４μｍ超０．５μｍ以下）の度数よりも大きい。すなわち、図５では、第１範囲（円相当径が０．３μｍ超０．６μｍ以下）は一つの極大度数を有する。 In FIG. 5, the frequency in the class having the equivalent circle diameter of more than 0.3 μm and 0.4 μm or less is the frequency of the class one below the class to which the frequency belongs (the equivalent circle diameter is more than 0.2 μm and 0.3 μm or less). , And the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.4 μm and 0.5 μm or less). That is, in FIG. 5, the first range (the equivalent circle diameter is more than 0.3 μm and 0.6 μm or less) has one maximum frequency.
　図５では、円相当径が０．７μｍ超０．８μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．６μｍ超０．７μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が０．８μｍ超０．９μｍ以下）の度数よりも大きい。また、図５では、円相当径が０．９μｍ超１．０μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．８μｍ超０．９μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が１．０μｍ超１．１μｍ以下）の度数よりも大きい。すなわち、図５では、第２範囲（円相当径が０．６μｍ超１．０μｍ以下）は二つの極大度数を有する。 In FIG. 5, the frequency in the class having a circle equivalent diameter of more than 0.7 μm and 0.8 μm or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.6 μm and 0.7 μm or less). , And the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.8 μm and 0.9 μm or less). Further, in FIG. 5, the frequency in the class having a circle equivalent diameter of more than 0.9 μm and 1.0 μm or less is one class lower than the class to which the frequency belongs (the circle equivalent diameter is more than 0.8 μm and 0.9 μm or less). It is larger than the frequency of the frequency and the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 1.0 μm and 1.1 μm or less). That is, in FIG. 5, the second range (the equivalent circle diameter is more than 0.6 μm and 1.0 μm or less) has two maximum frequencies.
　上記より、図５で示される炭化タングステン粒子の円相当径の分布は、上記（ｂ）を満たす。 From the above, the distribution of the equivalent circle diameter of the tungsten carbide particles shown in FIG. 5 satisfies the above (b).
　図５において、第１範囲内に存在する最も大きい極大度数である第１極大度数は、円相当径が０．３μｍ超０．４μｍ以下の階級における度数である。該第１極大度数の炭化タングステン粒子の総数に対する割合は１０％以上（約１１．８％）である。 In FIG. 5, the first maximum frequency, which is the largest maximum frequency existing in the first range, is a frequency in a class having a circle equivalent diameter of more than 0.3 μm and 0.4 μm or less. The ratio of the first maximum power to the total number of tungsten carbide particles is 10% or more (about 11.8%).
　図５において、第２範囲内に存在する最も大きい極大度数である第２極大度数は、円相当径が０．７μｍ超０．８μｍ以下の階級における度数である。該第２極大度数の炭化タングステン粒子の総数に対する割合は１０％以上（約１２．２％）である。 In FIG. 5, the second maximum frequency, which is the largest maximum frequency existing in the second range, is a frequency in a class having a circle equivalent diameter of more than 0.7 μm and 0.8 μm or less. The ratio of the second maximum power to the total number of tungsten carbide particles is 10% or more (about 12.2%).
　上記より、図５で示される炭化タングステン粒子の円相当径の分布は、上記（ｃ）を満たす。 From the above, the distribution of the equivalent circle diameter of the tungsten carbide particles shown in FIG. 5 satisfies the above (c).
　（図６）
　図６では、円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合は５０％以上（約７２．６％）である。従って、図６で示される炭化タングステン粒子の円相当径の分布は、上記（ａ）を満たす。 (Fig. 6)
In FIG. 6, the ratio based on the number of tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or more and 1.0 μm or less is 50% or more (about 72.6%). Therefore, the distribution of the equivalent circle diameters of the tungsten carbide particles shown in FIG. 6 satisfies the above (a).
　図６では、円相当径が０．４μｍ超０．５μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．３μｍ超０．４μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が０．５μｍ超０．６μｍ以下）の度数よりも大きい。すなわち、図６では、第１範囲（円相当径が０．３μｍ超０．６μｍ以下）は一つの極大度数を有する。 In FIG. 6, the frequency in the class having the equivalent circle diameter of more than 0.4 μm and 0.5 μm or less is the frequency of the class one below the class to which the frequency belongs (the equivalent circle diameter is more than 0.3 μm and 0.4 μm or less). , And the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.5 μm and 0.6 μm or less). That is, in FIG. 6, the first range (the equivalent circle diameter is more than 0.3 μm and 0.6 μm or less) has one maximum frequency.
　図６では、円相当径が０．６μｍ超０．７μｍ以下の階級における度数は、その度数の属する階級よりも一つ下の階級（円相当径が０．５μｍ超０．６μｍ以下）の度数、及び、その度数の属する階級よりも一つ上の階級（円相当径が０．７μｍ超０．８μｍ以下）の度数よりも大きい。すなわち、図６では、第２範囲（円相当径が０．６μｍ超１．０μｍ以下）は一つの極大度数を有する。 In FIG. 6, the frequency in the class having a circle equivalent diameter of more than 0.6 μm and 0.7 μm or less is the frequency of the class one below the class to which the frequency belongs (the circle equivalent diameter is more than 0.5 μm and 0.6 μm or less). , And the frequency of the class one level higher than the class to which the frequency belongs (the equivalent circle diameter is more than 0.7 μm and 0.8 μm or less). That is, in FIG. 6, the second range (the equivalent circle diameter is more than 0.6 μm and 1.0 μm or less) has one maximum frequency.
　上記より、図６で示される炭化タングステン粒子の円相当径の分布は、上記（ｂ）を満たす。 From the above, the distribution of the equivalent circle diameter of the tungsten carbide particles shown in FIG. 6 satisfies the above (b).
　図６において、第１範囲内に存在する最も大きい極大度数である第１極大度数は、円相当径が０．４μｍ超０．５μｍ以下の階級における度数である。該第１極大度数の炭化タングステン粒子の総数に対する割合は１０％以上（約１４．２％）である。 In FIG. 6, the first maximum frequency, which is the largest maximum frequency existing in the first range, is a frequency in a class having a circle equivalent diameter of more than 0.4 μm and 0.5 μm or less. The ratio of the first maximum power to the total number of tungsten carbide particles is 10% or more (about 14.2%).
　図６において、第２範囲内に存在する最も大きい極大度数である第２極大度数は、円相当径が０．６μｍ超０．７μｍ以下の階級における度数である。該第２極大度数の炭化タングステン粒子の総数に対する割合は１０％以上（約１２．４％）である。 In FIG. 6, the second maximum frequency, which is the largest maximum frequency existing in the second range, is a frequency in a class having a circle equivalent diameter of more than 0.6 μm and 0.7 μm or less. The ratio of the second maximum power to the total number of tungsten carbide particles is 10% or more (about 12.4%).
　上記より、図６で示される炭化タングステン粒子の円相当径の分布は、上記（ｃ）を満たす。 From the above, the distribution of the equivalent circle diameter of the tungsten carbide particles shown in FIG. 6 satisfies the above (c).
　本開示の炭化タングステン粒子の円相当径の分布を示すヒストグラムの横軸において、０．４μｍ超０．６μｍ以下の範囲を第３範囲と規定し、０．６μｍ超０．８μｍ以下の範囲を第４範囲と規定した場合、第３範囲は、第１極大度数を有し、第４範囲は、第２極大度数を有することが好ましい。これによると、工具寿命が更に向上する。 On the horizontal axis of the histogram showing the distribution of the equivalent circle diameters of the tungsten carbide particles of the present disclosure, the range of more than 0.4 μm and less than 0.6 μm is defined as the third range, and the range of more than 0.6 μm and less than 0.8 μm is defined as the third range. When defined as four ranges, it is preferable that the third range has a first maximum frequency and the fourth range has a second maximum frequency. According to this, the tool life is further improved.
　第１極大度数に対する、第２極大度数の割合は、０．８以上１．２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。この理由は、炭化タングステン粒子同士の接触による結合が重要であり、第１範囲内に存在する極大度数と第２範囲に存在する極大度数の差が大きくなると、結果的に超硬合金における炭化タングステン粒子同士の接触が少なくなるためと推察される。 The ratio of the second maximum frequency to the first maximum frequency is preferably 0.8 or more and 1.2 or less. According to this, the tool life is further improved. The reason for this is that the bonding by contact between the tungsten carbide particles is important, and when the difference between the maximum power existing in the first range and the maximum power existing in the second range becomes large, the tungsten carbide in the cemented carbide eventually becomes large. It is presumed that this is because the contact between particles is reduced.
　＜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 bonding phase in which the tungsten carbide particles constituting the first phase are bonded 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（Ｃｒ，Ｗ等）を含むことができる。 The second phase can contain iron group elements such as nickel and dissolved substances (Cr, W, etc.) in the alloy in addition to cobalt.
　＜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、を備える。超硬合金は、走査型電子顕微鏡で撮影した画像において、第１相を７５面積％以上１００面積％未満、かつ、第２相を０面積％超２０面積％以下含むことが好ましい。 <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. The cemented carbide preferably contains 75 area% or more and less than 100 area% of the first phase and 0 area% or more and 20 area% or less of the second phase in the image taken by the scanning electron microscope.
　超硬合金中の第２相の割合が２０面積％以下であると、円相当径が０．６μｍ以下である微粒の炭化タングステン粒子が第２相のコバルト中に溶解することを抑制することができ、円相当径が０．３μｍ超０．６μｍ以下の炭化タングステン粒子の減少を抑制することができる。また、加工中に工具表面に露出するコバルト量が更に減少する。よって、工具寿命が更に向上する。 When the ratio of the second phase in the cemented carbide is 20 area% or less, it is possible to suppress the dissolution of fine tungsten carbide particles having a circle equivalent diameter of 0.6 μm or less in the cobalt of the second phase. It is possible to suppress the decrease of tungsten carbide particles having a circle-equivalent diameter of more than 0.3 μm and 0.6 μm or less. In addition, the amount of cobalt exposed on the tool surface during machining is further reduced. Therefore, the tool life is further improved.
　超硬合金は、走査型電子顕微鏡で撮影した画像において、第２相を５面積％以上１２面積％以下含むことが好ましい。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。 The cemented carbide preferably contains the second phase in an amount of 5 area% or more and 12 area% or less in the image taken by the scanning electron microscope. According to this, the hardness and wear resistance required for processing the printed circuit board can be exhibited, and the occurrence of variation in tool life can be suppressed.
　超硬合金中の第１相の割合の下限は、７５面積％以上、８５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、７５面積％以上１００面積％未満、８５面積％以上９５面積％以下とすることができる。 The lower limit of the ratio of the first phase in the cemented carbide can be 75 area% or more and 85 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 75 area% or more and less than 100 area%, and 85 area% or more and 95 area% or less.
　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、２０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２０面積％以下、５面積％以上１２面積％以下とすることができる。 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 20 area% or less and 12 area% or less. The ratio of the second phase in the cemented carbide can be more than 0 area% and 20 area% or less, 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（Ａ３）～（Ｃ３）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 (A3) to (C3).
　（Ａ３）上記の炭化タングステン粒子の円相当径の測定方法に記載される（Ａ１）及び（Ｂ１）と同様の手順で、超硬合金の断面の撮像画像を得る。 (A3) An image of a cross section of the cemented carbide is obtained by the same procedure as in (A1) and (B1) described in the above-mentioned method for measuring the equivalent circle diameter of tungsten carbide particles.
　（Ｂ３）上記（Ａ３）で得られた撮影画像をコンピュータに取り込み、画像解析ソフトウェア（ＩｍａｇｅＪ：https://imagej.nih.gov/ij/）を用いて画像処理を行い、測定視野全体（縦２５．３μｍ×幅１７．６μｍの矩形）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。第１相と第２相とは、上記撮影画像中の色の濃淡で識別できる。 (B3) The captured image obtained in (A3) above is taken into a computer, image processing is performed using image analysis software (ImageJ: https://imagej.nih.gov/ij/), and the entire measurement field (vertical) is performed. The area ratio of each of the first phase and the second phase is measured with 25.3 μm × 17.6 μm wide rectangle as the denominator. The first phase and the second phase can be distinguished by the shade of color in the captured image.
　（Ｃ３）上記（Ｂ３）の画像処理を５つの測定視野で行う。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。 (C3) Perform the image processing of (B3) above in five measurement fields of view. 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.
　（クロム含有量）
　超硬合金はクロム（Ｃｒ）を含み、コバルトに対するクロムの質量基準の割合は、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。 (Chromium content)
The cemented carbide contains chromium (Cr), and the mass-based ratio of chromium to cobalt is preferably 5% or more and 10% or less. 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質量基準の割合が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 mass-based ratio of chromium to cobalt is 5% or more and 10% or less, precipitation of chromium carbide is unlikely 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質量基準の割合が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１．０μｍ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 mass-based ratio of chromium to cobalt is 10% or less, the degree of grain growth inhibitory action becomes appropriate, and the amount of tungsten carbide particles having a circle equivalent diameter of more than 1.0 μm in the cemented carbide becomes excessive. It can be suppressed.
　コバルトに対するクロムの質量基準の割合の下限は、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質量基準の割合は、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質量基準は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 mass-based ratio of chromium to cobalt is preferably 5% or more, more preferably 7% or more. The mass-based ratio of chromium to cobalt is preferably 10% or less, more preferably 9% or less. The mass standard of chromium with respect to cobalt can be 5% or more and 10% or less, and 7% or more and 9% or less.
　超硬合金中のコバルト及びクロムの含有量は、ＩＣＰ発光分光分析法により測定される。 The content of cobalt and chromium in cemented carbide is measured by ICP emission spectroscopy.
　（バナジウム）
　超硬合金がバナジウムを含む場合、超硬合金のバナジウムの質量基準の含有率は、１００ｐｐｍ未満であることが好ましい。 (vanadium)
When the cemented carbide contains vanadium, the mass-based content of vanadium in the cemented carbide is preferably less than 100 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。炭化タングステン粒子の粒成長の際にバナジウムが存在すると、炭化タングステン粒子の表面にバナジウムが析出する、又は、炭化タングステン粒子の成長面に短期的にバナジウムが介在することにより、炭化タングステン粒子の成長が抑制されると考えられる。 Since vanadium has a grain growth inhibitory effect, it has been used in the production of conventional ultrafine cemented carbide. If vanadium is present during the grain growth of the tungsten carbide particles, vanadium is precipitated on the surface of the tungsten carbide particles, or vanadium intervenes in the growth surface of the tungsten carbide particles in a short period of time, so that the tungsten carbide particles grow. It is thought to be suppressed.
　従って、バナジウムを添加すると、粒成長抑制作用を得ることができるが、炭化タングステン粒子とコバルトとの界面や、炭化タングステン粒子同士の界面に炭化タングステンが存在することから、濡れ性の低下や強度の低下を生じる傾向がある。従って、炭化タングステン中のバナジウムの含有量が少ないほど、炭化タングステン粒子とコバルトとの親和性や、炭化タングステン粒子同士の親和性を高く維持することができ、超硬合金の強度が向上する。 Therefore, when vanadium is added, a grain growth inhibitory effect can be obtained, but since tungsten carbide is present at the interface between the tungsten carbide particles and cobalt and at the interface between the tungsten carbide particles, the wettability is lowered and the strength is reduced. Tends to cause a decline. Therefore, the smaller the content of vanadium in the tungsten carbide, the higher the affinity between the tungsten carbide particles and cobalt and the affinity between the tungsten carbide particles can be maintained, and the strength of the cemented carbide is improved.
　超硬合金中のバナジウムの含有量は、１００ｐｐｍ以下が好ましく、10ｐｐｍ以下がより好ましい。超硬合金中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が好ましい。なお、意図せずに製造工程で数ppmのバナジウムが検出される場合がある。超硬合金中のバナジウムの含有量は、０ｐｐｍ以上１００ｐｐｍ以下、０ｐｐｍ以上１０ｐｐｍ以下とすることができる。 The content of vanadium in the cemented carbide is preferably 100 ppm or less, more preferably 10 ppm or less. Since the smaller the content of vanadium in the cemented carbide is, the more preferable it is, the lower limit thereof is preferably 0 ppm. In addition, vanadium of several ppm may be unintentionally detected in the manufacturing process. The content of vanadium in the cemented carbide can be 0 ppm or more and 100 ppm or less, and 0 ppm or more and 10 ppm or less.
　超硬合金中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 content of vanadium in cemented carbide is measured by ICP emission spectroscopy.
　＜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。また、本開示の効果を奏する限り、炭化バナジウム（ＶＣ）粉末も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、炭化バナジウム粉末は、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 a raw material for the first phase, and cobalt (Co) powder, which is a raw material for 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. Vanadium carbide (VC) powder can also be prepared as long as the effects of the present disclosure are exhibited. As the tungsten carbide powder, cobalt powder, chromium carbide powder, and vanadium carbide powder, commercially available ones can be used.
　炭化タングステン粉末は、（ａ）平均粒径が0.4μｍ以上1.2μｍ以下の炭化タングステン粉末（以下、「第１炭化タングステン粉末とも記す。」）、及び、（ｂ）平均粒径が0.8μｍ以上1.2μｍ以下の炭化タングステン粉末（以下、「第２炭化タングステン粉末」とも記す。）を準備する。第１炭化タングステン粉末は、その平均粒径が、第２炭化タングステン粉末の平均粒径よりも小さいものを準備する。本明細書において、原料粉末の平均粒径とは、円相当径のメジアン径ｄ５０を意味する。該平均粒径は、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。 The tungsten carbide powder includes (a) tungsten carbide powder having an average particle size of 0.4 μm or more and 1.2 μm or less (hereinafter, also referred to as “first tungsten carbide powder”), and (b) an average particle size of 0.8 μm or more and 1.2 μm or more. Tungsten carbide powder of μm or less (hereinafter, also referred to as “second tungsten carbide powder”) is prepared. The first tungsten carbide powder having an average particle size smaller than the average particle size of the second tungsten carbide powder is prepared. In the present specification, the average particle size of the raw material powder means a median diameter d50 having a diameter equivalent to a circle. The average particle size is measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.
　コバルト粉末の平均粒径は、０．８μｍ以上１．２μｍ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。炭化バナジウム粉末の平均粒径は、０．５μｍ以上１．０μｍ以下とすることができる。 The average particle size of the cobalt powder can be 0.8 μm or more and 1.2 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 of the vanadium carbide powder can be 0.5 μm or more and 1.0 μm or less.
　≪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.
　混合粉末中の第１炭化タングステン粉末の割合は、例えば、30質量％以上94.6質量％以下とすることができる。 The ratio of the first tungsten carbide powder in the mixed powder can be, for example, 30% by mass or more and 94.6% by mass or less.
　混合粉末中の第２炭化タングステン粉末の割合は、例えば、30質量％以上64.6質量％以下とすることができる。 The ratio of the second tungsten carbide powder in the mixed powder can be, for example, 30% by mass or more and 64.6% by mass or less.
　第１炭化タングステン粉末と第２炭化タングステン粉末との混合比は、例えば、質量基準で第１炭化タングステン粉末：第２炭化タングステン粉末＝２：１～１：２とすることができる。 The mixing ratio of the first tungsten carbide powder and the second tungsten carbide powder can be, for example, the first tungsten carbide powder: the second tungsten carbide powder = 2: 1 to 1: 2 on a mass basis.
　混合粉末中のコバルト粉末の割合は、例えば、２．８質量％以上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, 2.8% by mass or more 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、０．２質量％以上１．２質量％以下とすることができる。 The ratio of chromium carbide powder in the mixed powder can be, for example, 0.2% by mass or more and 1.2% by mass or less.
　混合粉末中の炭化バナジウム粉末の割合は、例えば、０質量％以上０．２質量％以下とすることができる。 The ratio of vanadium carbide powder in the mixed powder can be, for example, 0% by mass or more and 0.2% 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２０時間以上４８時間以下とすることができる。 Mix the mixed powder using a ball mill. The mixing time can be 20 hours or more and 48 hours or less.
　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 during 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、焼結温度は一般的な超硬合金の焼結温度（１３５０～１５００℃）とすることができる。 ≪Sintering process≫
The sintering step is a step of sintering the 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 a general cemented carbide sintering temperature (1350 to 1500 ° C.).
　超硬合金は一般的に１３５０～１５００℃で焼結されるが、微粒炭化タングステン粒子は表面積が大きく、コバルトに溶解しやすいため、溶解再析出により異常組織が発生しやすい。このため、微粒炭化タングステン粒子の焼結では、溶解再析出を抑制するために、コバルトに対する炭化タングステンの固溶限が低い１３５０～１３８０℃の低温度領域で焼結が行われている。しかし、低温度領域で焼結して得られた超硬合金においては、炭化タングステン粒子が粒成長をしていないため、炭化タングステン粒子表面は前工程での粉砕や混合により破砕されたままの状態となっている。よって、炭化タングステン粒子とコバルトとの界面や、炭化タングステン粒子同士の界面の結合力が低い状態となっており、耐摩耗性及び耐折損性が低下する傾向がある。 Cemented carbide is generally sintered at 1350 to 1500 ° C., but fine tungsten carbide particles have a large surface area and are easily dissolved in cobalt, so that an abnormal structure is likely to occur due to dissolution and reprecipitation. Therefore, in the sintering of fine tungsten carbide particles, in order to suppress dissolution and reprecipitation, sintering is performed in a low temperature region of 1350 to 1380 ° C., which has a low solid solution limit of tungsten carbide with cobalt. However, in the cemented carbide obtained by sintering in a low temperature region, the tungsten carbide particles do not grow, so the surface of the tungsten carbide particles remains crushed by crushing or mixing in the previous process. It has become. Therefore, the bonding force between the tungsten carbide particles and cobalt and the interface between the tungsten carbide particles is low, and the wear resistance and breakage resistance tend to decrease.
　一方、本開示の超硬合金の製造方法では、原料の粉砕や混合で発生する超微細な炭化タングステン粒子の破片の発生を抑制するとともに、クロムによる粒成長抑制効果を最大限に発揮させる。更に、微細組織の中に粒度の近いピークを持つ粗粒子と微粒子の分布を持たせることにより、通常では粒成長が起こるような温度域においても、異常粒成長を抑制することができることを見出した。このため、本開示の超硬合金の製造方法では、炭化タングステン粒子を従来よりも高温で焼結しても、異常組織の発生を抑制することが可能であり、炭化タングステン粒子とコバルトとの界面や、炭化タングステン粒子同士の界面の結合力が向上することで、超硬合金の耐摩耗性及び耐折損性を向上させることができる。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。 On the other hand, in the method for producing cemented carbide of the present disclosure, the generation of fragments of ultrafine tungsten carbide particles generated by crushing or mixing raw materials is suppressed, and the effect of suppressing grain growth by chromium is maximized. Furthermore, it has been found that abnormal grain growth can be suppressed even in a temperature range where grain growth normally occurs by providing a distribution of coarse particles and fine particles having peaks having similar particle sizes in the fine structure. .. Therefore, in the method for producing cemented carbide of the present disclosure, even if the tungsten carbide particles are sintered at a higher temperature than before, the generation of abnormal structure can be suppressed, and the interface between the tungsten carbide particles and cobalt can be suppressed. Further, by improving the bonding force at the interface between the tungsten carbide particles, it is possible to improve the wear resistance and the breaking resistance of the cemented carbide. This was newly discovered by the present inventors as a result of diligent studies.
　≪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 condition, general conditions may be adopted, and there is no particular limitation.
　［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 perpendicular 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, and the like. 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.
　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.
　［実施例１］
　実施例１では、原料粉末の種類及び配合比を変更して試料１～試料２４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。 [Example 1]
In Example 1, cemented carbides of Samples 1 to 24 were prepared by changing the type and compounding ratio 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。炭化ＷＣ粉末の平均粒径は表１の「第１ＷＣ粉末」の「平均粒径（μｍ）」欄に示される通りである。 ≪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 carbonized WC powder is as shown in the "Average particle size (μm)" column of the "first WC powder" in Table 1.
　コバルト（Ｃｏ）粉末の平均粒径は１μｍであり、炭化バナジウム（ＶＣ）粉末の平均粒径は０．８μｍであり、炭化クロム（Ｃｒ３Ｃ２）粉末の平均粒径は１μｍである。Ｃｏ粉末、ＶＣ粉末及びＣｒ３Ｃ２粉末は市販品である。原料粉末の平均粒径は、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。 The average particle size of cobalt (Co) powder is 1 [mu] m, an average particle diameter of the vanadium carbide (VC) powder was 0.8 [mu] m, an average particle size of chromium carbide (Cr 3 C 2) powder is 1 [mu] m. Co powder, VC powder and Cr 3 C 2 powder are commercially available products. The average particle size of the raw material 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。混合はボールミルで２０時間行った。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 amounts shown 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 carried out on a ball mill for 20 hours. 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、１４００℃で１時間維持して焼結した。 (Sintering process)
The molded product was placed in a sintering furnace and sintered in vacuum at 1400 ° C. for 1 hour.
　（冷却工程）
　焼結完了後、アルゴン（Ａｒ）ガス雰囲気中、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分布、第１相及び第２相の面積割合、コバルトに対するクロムの質量基準の割合、バナジウムの質量基準の含有量を測定した。 <Evaluation>
For the cemented carbide of each sample, the 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 ratio of chromium to cobalt, and the mass-based content of vanadium were measured.
　（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、炭化タングステン粒子の円相当径の分布を測定し、円相当径が０．３μｍ以上１．０μｍ以下である炭化タングステン粒子の個数基準の割合、第１極大度数の存在する階級、第１極大度数の炭化タングステン粒子の総数に対する割合、第２極大度数の存在する階級、第２極大度数の炭化タングステン粒子の総数に対する割合、第１極大度数に対する第２極大度数の割合を算出した。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 distribution of the equivalent circle diameter of the tungsten carbide particles was measured, and the ratio based on the number of tungsten carbide particles having the equivalent circle diameter of 0.3 μm or more and 1.0 μm or less, and the existence of the first maximum frequency. The class to be used, the ratio of the first maximum frequency to the total number of tungsten carbide particles, the class in which the second maximum frequency exists, the ratio of the second maximum frequency to the total number of tungsten carbide particles, and the ratio of the second maximum frequency to the first maximum frequency. 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１の「円相当径０．３－１．０μｍ割合（％）」、「第１極大度数」の「階級（μｍ）」及び「割合（％）」、「第２極大度数」の「階級（μｍ）」及び「割合（％）」、「第２極大度数／第１極大度数」欄に示す。 The results are shown in Table 1 for "Circle equivalent diameter 0.3-1.0 μm ratio (%)", "First maximum frequency", "Class (μm)", "Ratio (%)", and "Second maximum frequency", respectively. It is shown in the "Class (μm)", "Ratio (%)", and "Second maximum frequency / First maximum frequency" columns.
　極大度数が、第１範囲（０．３μｍ超０．６μｍ以下）内、又は、第２範囲（０．６μｍ超１．０μｍ以下）内に存在しない場合は、「－」と表記する。また、極大度数が、第１範囲（０．３μｍ超０．６μｍ以下）外、又は、第２範囲（０．６μｍ超１．０μｍ以下）外に存在する場合は、該極大度数の階級を括弧（）内に示す。 If the maximum frequency does not exist within the first range (more than 0.3 μm and less than 0.6 μm) or the second range (more than 0.6 μm and less than 1.0 μm), it is indicated as “-”. If the maximum frequency is outside the first range (more than 0.3 μm and 0.6 μm or less) or outside the second range (more than 0.6 μm and 1.0 μm or less), the class of the maximum frequency is shown in parentheses. Shown in parentheses.
　（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１の「第１相（面積％）」及び「第２相（面積％）」欄に示す。 (Volume ratio of first phase and second phase)
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 "Phase 1 (Area%)" and "Phase 2 (Area%)" columns of Table 1.
　（コバルトに対するクロムの質量基準の割合、バナジウムの質量基準の含有量）
　各試料の超硬合金について、コバルトに対するクロムの質量基準の割合及びバナジウムの質量基準の含有量を測定した。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１の「Ｃｒ／Ｃｏ（％）」及び「Ｖ（ｐｐｍ）」欄に示す。 (Mass-based ratio of chromium to cobalt, mass-based content of vanadium)
For the cemented carbide of each sample, the mass-based ratio of chromium to cobalt and the mass-based content of vanadium 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 "Cr / Co (%)" and "V (ppm)" columns of Table 1.
　＜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線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１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 prepare a small-diameter drill having 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. A commercially available in-vehicle printed circuit board was drilled using the drill. The conditions for drilling were a rotation speed of 155 krpm 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 1. In addition, the state of the cutting edge after drilling was observed. The results are shown in the "Blade 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、３本のドリル全て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１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 all three drills were broken immediately after the start of machining and the wear amount could not be measured. When "one broken piece" 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 1. When "fine chipping" is described in the "cutting edge state" column, it indicates that minute chipping has occurred on the cutting edge.
　＜考察＞
　試料３，５～９，１３～２４は実施例に該当する。 <Discussion>
Samples 3, 5 to 9, 13 to 24 correspond to Examples.
　試料１，４，１２は、第２範囲内に極大度数（第２極大度数）が存在せず、比較例に該当する。なお、試料１２には階級１．０μｍ超１．１μｍ以下に極大度数が存在していた。 Samples 1, 4 and 12 do not have a maximum frequency (second maximum frequency) within the second range, and correspond to a comparative example. In the sample 12, the maximum frequency was present in the class of more than 1.0 μm and 1.1 μm or less.
　試料２，１０，１１は、第１範囲内に極大度数（第１極大度数）が存在せず、比較例に該当する。試料２は階級０．２μｍ超０．３μｍ以下に極大度数が存在しており、この極大度数の個数基準の割合は１０．１％であった。 Samples 2, 10 and 11 do not have a maximum frequency (first maximum frequency) within the first range, and correspond to a comparative example. Sample 2 had a maximum frequency in a class of more than 0.2 μm and 0.3 μm or less, and the ratio of the number standard of this maximum frequency was 10.1%.
　試料３，５～９，１３～２４（実施例）は、試料１，２，４，１０，１２（比較例）に比べて摩耗量が小さく、工具寿命が長いことが確認された。なお、試料１１（比較例）は、３本とも開始直後に折損が生じ、摩耗量を測定できなかった。 It was confirmed that the samples 3, 5 to 9, 13 to 24 (Example) had a smaller amount of wear and a longer tool life than the samples 1, 2, 4, 10, 12 (Comparative Example). In addition, in the sample 11 (comparative example), the amount of wear could not be measured because all three samples were broken immediately after the start.
　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。 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 modified in various ways.
　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。 It should be considered that the embodiments and examples disclosed this time are examples in all respects and are 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 meaning equivalent to the scope of claims and all modifications within the scope.

Claims (10)

  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影した画像に対して画像処理を行うことにより、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、前記円相当径が０．３μｍ以上１．０μｍ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５０％以上であり、
    　前記炭化タングステン粒子の円相当径の分布を、度数を縦軸とし、階級を横軸とするヒストグラムで表した場合、
    　前記度数は、前記炭化タングステン粒子の個数であり、
    　前記階級は、前記円相当径が昇順に０．１μｍ間隔で区切られており、
    　前記横軸において、０．３μｍ超０．６μｍ以下の範囲を第１範囲と規定し、０．６μｍ超１．０μｍ以下の範囲を第２範囲と規定し、
    　前記第１範囲及び前記第２範囲は、それぞれ少なくとも一つの極大度数を有し、
    　前記第１範囲内に存在する極大度数のうち、最も大きい第１極大度数の前記炭化タングステン粒子の総数に対する割合は１０％以上であり、
    　前記第２範囲内に存在する極大度数のうち、最も大きい第２極大度数の前記炭化タングステン粒子の総数に対する割合は１０％以上である、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.
    When the equivalent circle diameter of each of the tungsten carbide particles is calculated by performing image processing on the image of the cemented carbide taken with a scanning electron microscope, the equivalent circle diameter is 0.3 μm or more and 1.0 μm. The ratio based on the number of the tungsten carbide particles below is 50% or more.
    When the distribution of the equivalent circle diameter of the tungsten carbide particles is represented by a histogram with the frequency as the vertical axis and the class as the horizontal axis,
    The frequency is the number of the tungsten carbide particles, and is
    In the class, the equivalent circle diameter is divided in ascending order at intervals of 0.1 μm.
    On the horizontal axis, a range of more than 0.3 μm and 0.6 μm or less is defined as the first range, and a range of more than 0.6 μm and 1.0 μm or less is defined as the second range.
    The first range and the second range each have at least one maximum frequency.
    Among the maximum powers existing in the first range, the ratio of the largest first maximum power to the total number of the tungsten carbide particles is 10% or more.
    A cemented carbide in which the ratio of the largest second maximum power to the total number of the tungsten carbide particles among the maximum powers existing in the second range is 10% or more.
  2. 　前記超硬合金は、走査型電子顕微鏡で撮影した画像において、前記第１相を７５面積％以上１００面積％未満、かつ、前記第２相を０面積％超２０面積％以下含む、請求項１に記載の超硬合金。 The cemented carbide comprises 75 area% or more and less than 100 area% of the first phase and 0 area% or more and 20 area% or less of the second phase in an image taken by a scanning electron microscope. Cemented carbide described in.
  3. 　前記超硬合金は、走査型電子顕微鏡で撮影した画像において、前記第２相を５面積％以上１２面積％以下含む、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 cemented carbide contains 5 area% or more and 12 area% or less of the second phase in an image taken by a scanning electron microscope.
  4. 　前記超硬合金は、クロムを含み、
    　前記コバルトに対する前記クロムの質量基準の割合は、５％以上１０％以下である、請求項１から請求項３のいずれか１項に記載の超硬合金。     The cemented carbide contains chromium and
    The cemented carbide according to any one of claims 1 to 3, wherein the ratio of the chromium to the cobalt based on the mass is 5% or more and 10% or less.
  5. 　前記超硬合金がバナジウムを含む場合、前記超硬合金の前記バナジウムの質量基準の含有率は、１００ｐｐｍ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 when the cemented carbide contains vanadium, the content of the cemented carbide based on the mass of the vanadium is less than 100 ppm.
  6. 　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７％以下である、請求項１から請求項５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 5, wherein the ratio based on the number of the tungsten carbide particles having a circle-equivalent diameter of 0.3 μm or less is 7% or less.
  7. 　前記第１極大度数に対する、前記第２極大度数の割合は、０．８以上１．２以下である、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。 The cemented carbide according to any one of claims 1 to 6, wherein the ratio of the second maximum frequency to the first maximum frequency is 0.8 or more and 1.2 or less.
  8. 　前記横軸において、０．４μｍ超０．６μｍ以下の範囲を第３範囲と規定し、０．６μｍ超０．８μｍ以下の範囲を第４範囲と規定した場合、
    　前記第３範囲は、前記第１極大度数を有し、
    　前記第４範囲は、前記第２極大度数を有する、請求項１から請求項７のいずれか１項に記載の超硬合金。     When the range of more than 0.4 μm and 0.6 μm or less is defined as the third range and the range of more than 0.6 μm and 0.8 μm or less is defined as the fourth range on the horizontal axis,
    The third range has the first maximal frequency and
    The cemented carbide according to any one of claims 1 to 7, wherein the fourth range has the second maximum frequency.
  9. 　請求項１から請求項８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 8.
  10. 　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９に記載の切削工具。 The cutting tool according to claim 9, wherein the cutting tool is a rotary tool for processing a printed circuit board.
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