Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B27/00—Tools for turning or boring machines; Tools of a similar kind in general; Accessories therefor
  • B23B27/14—Cutting tools of which the bits or tips or cutting inserts are of special material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B51/00—Tools for drilling machines
• • 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
  • C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
• • 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.
• cemented carbide alloys comprising multiple tungsten carbide particles and a binder phase have been used as materials for cutting tools (Patent Document 1).
• the cemented carbide disclosed herein is a cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide contains a total of 89 to 100 volume % of the tungsten carbide particles and the binder phase, and the cemented carbide contains 0.5 to 25 volume % of the binder phase, the binder phase containing 40 mass % or more of cobalt, and the binder phase further containing at least one first element selected from the group consisting of boron, aluminum, silicon, phosphorus, sulfur, nickel, gallium, germanium, arsenic, and selenium, and the lattice constant of the cobalt is 3.560 ⁇ or less.
• FIG. 1 is a schematic diagram of a cutting tool according to a second embodiment.
• the present disclosure therefore aims to provide a cemented carbide alloy that enables a longer lifespan for cutting tools, particularly when used as a material for cutting tools used to drill holes in thick copper printed circuit boards, and a cutting tool equipped with the same.
• a cutting tool according to the present disclosure is a cemented carbide alloy comprising a plurality of tungsten carbide particles and a binder phase, the cemented carbide alloy comprising a total of 89 to 100 volume % of the tungsten carbide particles and the binder phase, the cemented carbide alloy comprising 0.5 to 25 volume % of the binder phase, the binder phase comprising 40 mass % or more of cobalt, the binder phase further comprising at least one first element selected from the group consisting of boron, aluminum, silicon, phosphorus, sulfur, nickel, gallium, germanium, arsenic, and selenium, and the lattice constant of the cobalt is 3.560 ⁇ or less.
• the present disclosure provides a cemented carbide alloy and a cutting tool incorporating the same that enable a longer cutting tool life, particularly when used as a material for cutting tools used to drill holes in thick copper printed circuit boards.
• the reasons for this are believed to be as follows.
• the cemented carbide of the present disclosure comprises a plurality of tungsten carbide particles (hereinafter also referred to as "WC particles") and a binder phase.
• the total content of the WC particles and binder phase in the cemented carbide is 89% by volume or more and 100% by volume or less. This allows the cemented carbide to have high hardness and strength, and cutting tools incorporating the cemented carbide to have excellent wear resistance and breakage resistance.
• the cemented carbide disclosed herein contains a binder phase of 0.5% by volume or more and 25% by volume or less.
• the binder phase contains 40% by mass or more of cobalt.
• the binder phase content of the cemented carbide is 0.5% by volume or more, the toughness of the cemented carbide is improved.
• the binder phase content of the cemented carbide is 25% by volume or less, the hardness of the cemented carbide is improved. Therefore, cutting tools equipped with this cemented carbide can have excellent wear resistance and breakage resistance.
• the binder phase further contains at least one first element selected from the group consisting of boron, aluminum, silicon, phosphorus, sulfur, nickel, gallium, germanium, arsenic, and selenium.
• a powder of the first element is used together with tungsten carbide powder and cobalt powder as raw materials, and specific production conditions are used. This allows the binder phase to contain the first element, and the lattice constant of the cobalt having an fcc structure in the binder phase to be smaller than the lattice constant (3.569 ⁇ ) when cobalt exists alone.
• the lattice constant of cobalt is 3.560 ⁇ or less.
• the lattice constant of cobalt is smaller than the lattice constant of cobalt in conventional cemented carbide (3.569 ⁇ ) and closer to the lattice constant of tungsten carbide (WC) (2.8 to 2.9 ⁇ ).
• This increases the binding force between the tungsten carbide particles and cobalt, improving the interfacial strength between the WC particles and the binder phase and increasing the rigidity of the cemented carbide.
• the thermal expansion characteristics of the cemented carbide are made uniform, improving resistance to thermal stress fracture.
• the cemented carbide of the present disclosure has improved tensile strength of the binder phase.
• Patent Document 1 the technical idea of increasing the lattice constant of cobalt has been adopted to improve the strength, heat resistance, and other properties of cemented carbide.
• the cemented carbide disclosed herein is based on the opposite technical idea of decreasing the lattice constant of cobalt to improve the properties of the cemented carbide.
• the lattice constant of the cobalt may be 3.530 ⁇ or more and 3.550 ⁇ or less.
• the compressive strength of the binder phase is improved.
• the lattice constant of cobalt is 3.550 ⁇ or less, the rigidity and resistance to thermal stress fracture of the cemented carbide, as well as the tensile strength of the binder phase, are further improved. Therefore, cutting tools equipped with cemented carbide have further improved breakage resistance in the early stages of cutting, and further improved tool life.
• the percentage of the mass M1 of the first element in the binder phase relative to the total mass M1+M2 of the first element M1 and the cobalt M2, ⁇ M1/(M1+M2) ⁇ x 100 may be 0.1% or more and 25% or less.
• ⁇ M1/(M1+M2) ⁇ x 100 is 0.2% or more, the rigidity and resistance to thermal stress fracture of the cemented carbide, as well as the tensile strength of the binder phase, are further improved. Therefore, cutting tools including cemented carbide have further improved breakage resistance in the early stages of cutting, and further improved tool life.
• ⁇ M1/(M1+M2) ⁇ x 100 is 25% or less, the strength and hardness of the cemented carbide are improved.
• the average particle size of the tungsten carbide particles may be 0.2 ⁇ m or more and 3 ⁇ m or less.
• the average particle size of the WC particles is 0.2 ⁇ m or more, the strength of the cemented carbide alloy is improved.
• the average particle size of the WC particles is 3 ⁇ m or less, the hardness of the cemented carbide alloy is improved. Therefore, the wear resistance of a cutting tool equipped with the cemented carbide alloy is improved, and the tool life is further extended.
• the lattice constant of the cobalt is measured by wide-angle X-ray diffraction measurement.
• the cutting tool of the present disclosure is a cutting tool having a cutting edge made of the cemented carbide alloy described in any one of (1) to (5) above.
• a ⁇ B means greater than or equal to A and less than or equal to B. If no unit is specified for A and only a unit is specified for B, the units for A and B are the same.
• a cemented carbide according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein the cemented carbide comprises a total of 89 volume % or more and 100 volume % or less of the tungsten carbide particles and the binder phase, and the cemented carbide comprises 0.5 volume % or more and 25 volume % or less of the binder phase, the binder phase comprising 40 mass % or more of cobalt, and the binder phase further comprising at least one first element selected from the group consisting of boron, aluminum, silicon, phosphorus, sulfur, nickel, gallium, germanium, arsenic, and selenium, and the lattice constant of the cobalt is 3.560 ⁇ or less.
• the cemented carbide of embodiment 1 comprises a total of 89 to 100 volume % of tungsten carbide particles and a binder phase.
• the cemented carbide may comprise a total of 90 to 100 volume % of tungsten carbide particles and a binder phase, or may comprise a total of 92 to 100 volume % of tungsten carbide particles and a binder phase.
• the cemented carbide of embodiment 1 contains 0.5% to 25% by volume of a binder phase.
• the binder phase content of the cemented carbide may be 2% to 20% by volume, 3% to 18% by volume, or 4% to 15% by volume.
• the cemented carbide of embodiment 1 may be composed of a plurality of tungsten carbide particles and a binder phase. As long as the effects of the present disclosure are not impaired, the cemented carbide of embodiment 1 may be composed of a plurality of tungsten carbide particles, a binder phase, and impurities.
• the cemented carbide may contain other phases (not shown).
• the other phases may include carbides, nitrides, or carbonitrides containing at least one element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo).
• the composition of the other phases may be, for example, at least one element selected from the group consisting of TiCN, TaC, NbC, ZrC, HfC, and Mo2C .
• the content of other phases in the cemented carbide is permissible as long as it does not impair the effects of the present disclosure.
• the content of other phases in the cemented carbide may be greater than 0 vol% and less than 11 vol%, greater than 0 vol% and less than 10 vol%, or greater than 0 vol% and less than 8 vol%.
• the cemented carbide of embodiment 1 may be composed of a plurality of tungsten carbide particles, a binder phase, and other phases. As long as the effects of the present disclosure are not impaired, the cemented carbide of embodiment 1 may be composed of a plurality of tungsten carbide particles, a binder phase, other phases, and impurities.
• impurities include, for example, iron (Fe) and calcium (Ca).
• the impurity content of the cemented carbide alloy is acceptable as long as it does not impair the effects of the present disclosure.
• the impurity content of the cemented carbide alloy may be equal to or greater than 0% by mass and less than 0.1% by mass.
• the impurity content of the cemented carbide alloy is measured by ICP optical emission spectroscopy (Inductively Coupled Plasma Emission Spectroscopy).
• the measuring device that can be used is the "ICPS-8100" (trademark) manufactured by Shimadzu Corporation.
• the tungsten carbide particle content of the cemented carbide of embodiment 1 may be 75% by volume or more and 99.5% by volume or less, 80% by volume or more and 98% by volume or less, 82% by volume or more and 97% by volume or less, or 85% by volume or more and 96% by volume or less.
• the method for measuring the tungsten carbide particle content (volume %) and binder phase content (volume %) of cemented carbide is as follows:
• the mirror-finished surface of the cemented carbide is photographed with a scanning electron microscope (SEM) to obtain a backscattered electron image.
• the photographed area is set to the center of the cemented carbide cross section, that is, a position that does not include areas with properties clearly different from the bulk part, such as near the surface of the cemented carbide (a position where the photographed area is entirely the bulk part of the cemented carbide).
• the observation magnification is 5000x.
• the measurement conditions are an acceleration voltage of 3 kV, a current value of 2 nA, and a working distance (WD) of 5 mm.
• (H1) The measurement of (G1) above is performed in five different, non-overlapping measurement fields.
• the average area percentage of tungsten carbide particles in the five measurement fields corresponds to the tungsten carbide particle content (volume %) of the cemented carbide
• the average area percentage of the binder phase in the five measurement fields corresponds to the binder phase content (volume %) of the cemented carbide.
• the content of the other phases in the cemented carbide can be obtained by subtracting the content (volume %) of tungsten carbide particles and the content (volume %) of binder phase measured using the above procedure from the total cemented carbide (100 volume %).
• the tungsten carbide particles include at least one of "pure WC particles (including WC containing no impurity elements and WC containing impurity elements below the detection limit)" and "WC particles containing impurity elements intentionally or unavoidably contained therein, as long as the effects of the present disclosure are not impaired.”
• the impurity content of the tungsten carbide particles (when two or more elements constitute the impurities, the total concentration of these elements) is less than 0.1% by mass.
• the impurity element content of the tungsten carbide particles is measured by ICP optical emission spectrometry.
• the average particle size of the tungsten carbide particles is not particularly limited. It has been confirmed that the cemented carbide of embodiment 1 enables a longer tool life when used as a cutting tool material, regardless of the average particle size of the tungsten carbide particles. From the perspective of improving tool life, the average particle size of the tungsten carbide particles may be 0.2 ⁇ m or more and 3 ⁇ m or less, 0.2 ⁇ m or more and 2.8 ⁇ m or less, or 0.8 ⁇ m or more and 2.5 ⁇ m or less.
• the average particle size of tungsten carbide particles is measured as follows. Using the same method as steps (A1) to (G1) of the methods for measuring the tungsten carbide particle content and binder phase content of cemented carbide, a rectangular measurement field of 24.9 ⁇ m x 18.8 ⁇ m is set in the binarized image. Using the image analysis software, the equivalent circle diameter (Heywood diameter: diameter equivalent to a circle with an equal area) of each of the tungsten carbide particles in the measurement field is measured. This measurement is performed in three different, non-overlapping measurement fields. In this disclosure, the 50% cumulative area-based particle size (equivalent circle diameter) D50 is calculated based on all tungsten carbide particles in the three measurement fields. This D50 corresponds to the average particle size of the tungsten carbide particles.
• the binder phase contains 40% by mass or more of cobalt, which allows the cemented carbide to have excellent toughness.
• the cobalt content of the binder phase may be 40% by mass or more but less than 100% by mass, 50% by mass or more but 90% by mass or less, or 60% by mass or more but 80% by mass or less.
• the method for measuring the cobalt content of the binder phase is as follows.
• An elemental mapping image and a binarized image are obtained using the same methods as steps (A1) to (E1) of the method for measuring the tungsten carbide particle content and binder phase content of the cemented carbide described above.
• the elemental mapping image and the binarized image are overlaid to identify the region where the binder phase exists in the elemental mapping image.
• a rectangular measurement field of view measuring 24.9 ⁇ m x 18.8 ⁇ m is set in the elemental mapping image.
• the cobalt content is measured in the region where the binder phase exists in the measurement field.
• the above measurement is performed in five different, non-overlapping measurement fields.
• the average of the cobalt contents in the regions where the binder phase exists in the five measurement fields corresponds to the cobalt content of the binder phase.
• the binder phase further comprises at least one first element selected from the group consisting of boron, aluminum, silicon, phosphorus, sulfur, nickel, gallium, germanium, arsenic, and selenium.
• the inclusion of the first element in the binder phase can be confirmed using the following procedure.
• An elemental mapping image and a binarized image are obtained using the same methods as steps (A1) to (E1) in the method for measuring the tungsten carbide particle content and binder phase content of the cemented carbide described above.
• the region in which the binder phase exists is identified in the elemental mapping image. If the first element is present in the region in which the binder phase exists in the elemental mapping, it is confirmed that the binder phase contains the first element.
• the percentage of the mass M1 of the first element relative to the sum M1+M2 of the mass M1 of the first element and the mass M2 of cobalt, ⁇ M1/(M1+M2) ⁇ x 100 is 0.1% or more and 25% or less, or may be 0.2% or more and 25% or less, 0.4% or more and 10% or less, 0.6% or more and 7% or less, or 1.0% or more and 5% or less.
• the units of mass M1 and mass M2 are the same.
• the mass M1 of the first element means the total mass of all types of first elements.
• the method for measuring the percentage ⁇ M1/(M1+M2) ⁇ x 100 is as follows: An elemental mapping image and a binarized image are obtained using the same methods as steps (A1) to (E1) of the method for measuring the tungsten carbide particle content and binder phase content of the cemented carbide. The elemental mapping image and the binarized image are overlaid to identify the region where the binder phase exists in the elemental mapping image. A rectangular measurement field of view measuring 24.9 ⁇ m x 18.8 ⁇ m is set in the elemental mapping image.
• the percentage ⁇ m1/(m1+m2) ⁇ x 100 of the mass m1 of the first element relative to the sum m1+m2 of the mass m1 of the first element and the mass m2 of cobalt is calculated.
• the above measurement is performed in five different, non-overlapping measurement fields.
• the average of the percentage ⁇ m1/(m1+m2) ⁇ x 100 in the five measurement fields corresponds to the "percentage ⁇ M1/(M1+M2) ⁇ x 100" in the binder phase of the cemented carbide.
• the binder phase may contain, in addition to cobalt and the first element, at least one second element selected from the group consisting of iron (Fe) and chromium (Cr).
• the binder phase may consist of cobalt, the first element, and the second element.
• the binder phase may consist of cobalt, the first element, the second element, and inevitable impurities.
• the lattice constant of cobalt is 3.560 ⁇ or less, or may be 3.559 ⁇ or less, 3.556 ⁇ or less, 3.553 ⁇ or less, 3.552 ⁇ or less, 3.550 ⁇ or less, 3.549 ⁇ or less, 3.557 ⁇ or less, or 3.546 ⁇ or less.
• the lattice constant of cobalt may be 3.530 ⁇ or more, or 3.540 ⁇ or more.
• the lattice constant of cobalt may be 3.530 ⁇ or more and 3.560 ⁇ or less.
• the lattice constant of cobalt refers to the lattice constant of cobalt having an fcc structure.
• the main crystal structure of cobalt is an fcc structure.
• more than 50 volume % of the cobalt may have an fcc structure, or 60 volume % or more may have an fcc structure. It has been confirmed that as long as more than 50 volume % of the cobalt in the cemented carbide of embodiment 1 has an fcc structure and the lattice constant of the cobalt is 3.560 ⁇ or less, the effects of the present disclosure derived from the lattice constant of cobalt can be obtained.
• ⁇ Measurement conditions> X-ray used: Cu-K ⁇ Incidence optical system: CBO-f Excitation conditions: 45 kV/200 mA Slit: 0.8 mm Light receiving optical system: HyPix-3000 (2-dimensional) Scanning: 2 ⁇ - ⁇ scan Range: 2 ⁇ 42°-53° Scan speed: 0.2°/min
• the cemented carbide of the first embodiment can be manufactured by carrying out the steps of preparing raw material powder, mixing, molding, sintering, cooling and sintering, and HIP (Hot Isostatic Pressing) in the above order. Each step will be described below.
• the preparation step is a step of preparing a raw material powder for the cemented carbide.
• the raw material powder include tungsten carbide powder (hereinafter also referred to as "WC powder"), cobalt powder, first element powder, and alloy powder of the first element and cobalt.
• the first element powder include boron powder, aluminum powder, silicon powder, phosphorus powder, sulfur powder, nickel powder, gallium powder, germanium powder, arsenic powder, and selenium powder.
• raw material powders such as iron powder, vanadium carbide powder, and titanium carbonitride powder can be prepared. These raw material powders can be commercially available.
• the average particle size of the raw material powder is not particularly limited and may be, for example, 0.5 to 5 ⁇ m.
• the average particle size of the raw material powder refers to the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method.
• the average particle size is measured using a "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.
• the mixing step is a step of mixing the raw material powders prepared in the preparation step in a predetermined ratio.
• a mixed powder in which the raw material powders are mixed is obtained by the mixing step.
• the mixing ratio of the raw material powders is appropriately adjusted according to the target composition of the cemented carbide and within a range in which free carbon does not appear.
• a ball mill is used to mix the raw material powders.
• the mixing conditions are a ball diameter of 2 mm, a rotation speed of 100 rpm, and a time of 10 hours.
• the mixed powder may be granulated if necessary. Granulating the mixed powder makes it easier to fill the mixed powder into a die or mold during the molding step described below.
• Known granulation methods can be used for granulation, and for example, commercially available granulators such as spray dryers can be used.
• the molding step is a step of molding the mixed powder obtained in the mixing step into a shape for a cutting tool to obtain a molded body.
• the molding method and molding conditions in the molding step are not particularly limited and may be general methods and conditions.
• the sintering step is a step in which the compact obtained in the compacting step is sintered to obtain a cemented carbide intermediate body, which is sintered under vacuum at 1350°C for 6 hours.
• the cooling and sintering step is a step in which the cemented carbide intermediate body after the sintering step is repeatedly cooled and sintered. Specifically, the cemented carbide intermediate body is cooled to 800°C at a rate of -2°C/min, then heated to 1350°C and held at that temperature for 4 hours for sintering. This cooling and sintering step is repeated five times.
• the HIP process is a process for obtaining a cemented carbide by subjecting the cemented carbide intermediate body after the cooling and sintering processes to HIP, where the HIP conditions are 100 MPa and 1250°C, and holding for 2 hours.
• a cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is a cutting tool having a cutting edge made of the cemented carbide of Embodiment 1.
• the cutting edge refers to a portion involved in cutting. More specifically, the cutting edge refers to a region surrounded by a cutting edge ridge and an imaginary surface that is 0.5 mm or 2 mm away from the cutting edge ridge toward the cemented carbide.
• Cutting tools include, for example, cutting tools, drills, end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, metal saws, gear cutting tools, reamers, taps, etc.
• the cutting tool 10 of embodiment 2 can demonstrate excellent effects in the case of small-diameter drills for machining copper-plated printed circuit boards.
• the cutting edge 11 of the cutting tool 10 shown in Figure 1 is made of the cemented carbide of embodiment 1.
• the cemented carbide of embodiment 1 may constitute the entire tool, or may constitute only a part of the tool.
• "constitute a part” refers to a mode in which the cemented carbide of embodiment 1 is brazed to a predetermined position on any substrate to form a cutting edge.
• the cutting tool of embodiment 2 may further include a hard film that covers at least a portion of the surface of the substrate made of cemented carbide.
• a hard film that covers at least a portion of the surface of the substrate made of cemented carbide.
• diamond-like carbon or diamond can be used as the hard film.
• WC powder (average particle size: as shown in Table 1)
• Co powder (average particle size: 1 ⁇ m)
• first element powder (average particle size: 1 ⁇ m)
• Fe powder (average particle size: 1 ⁇ m)
• VC powder (average particle size: 1 ⁇ m)
• TiCN powder average particle size: 1 ⁇ m
• first element powders boron powder, aluminum powder, silicon powder, phosphorus powder, sulfur powder, nickel powder, gallium powder, germanium powder, arsenic powder, and selenium powder were prepared.
• Each raw material powder was prepared in the proportion shown in Table 1.
• step A or B The following step A or B was carried out on the cemented carbide intermediate.

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