JP5309394B2 - Cemented carbide - Google Patents

Cemented carbide Download PDF

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JP5309394B2
JP5309394B2 JP2009098421A JP2009098421A JP5309394B2 JP 5309394 B2 JP5309394 B2 JP 5309394B2 JP 2009098421 A JP2009098421 A JP 2009098421A JP 2009098421 A JP2009098421 A JP 2009098421A JP 5309394 B2 JP5309394 B2 JP 5309394B2
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cemented carbide
carbide
powder
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JP2010248560A (en
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克哉 内野
英司 山本
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Sumitomo Electric Hardmetal Corp
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Priority to PCT/JP2010/056291 priority patent/WO2010119795A1/en
Priority to CN201080001804.3A priority patent/CN102057069B/en
Priority to KR1020107026230A priority patent/KR101245499B1/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
    • 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
    • C22C29/005—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides comprising a particular metallic binder

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  • Mechanical Engineering (AREA)
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  • Perforating, Stamping-Out Or Severing By Means Other Than Cutting (AREA)
  • Ceramic Products (AREA)

Description

本発明は、超硬合金に関するものである。特に、高硬度でありながら、靭性及び強度に優れる超硬合金に関するものである。   The present invention relates to a cemented carbide. In particular, the present invention relates to a cemented carbide excellent in toughness and strength while having high hardness.

高圧水流加工(ウォータジェット加工)用のノズル、カメラなどに用いられるガラスレンズ用などの金型といった部材の構成材料として、WC(炭化タングステン)とCo(コバルト)とを混合した後、焼結した超硬合金が利用されている(例えば、特許文献1〜3)。   Sintered after mixing WC (tungsten carbide) and Co (cobalt) as a component material for parts such as nozzles for high-pressure water flow processing (water jet processing), molds for glass lenses used in cameras, etc. Cemented carbide is used (for example, Patent Documents 1 to 3).

上記高圧水流加工用のノズルなどの部材では、特に、耐摩耗性に優れることが望まれる。耐摩耗性を向上するには、硬度を高めることが効果的である。硬度を高めるには、WCよりも硬度が低いCoの含有量を低減したり、WCを微細にすることが挙げられる。WCを微細にするには、特許文献1〜3に記載されるように、VC(炭化バナジウム),Mo2C(炭化モリブデン),Cr3C2といったCr(クロム)炭化物などの粒成長の抑制効果がある金属炭化物を添加することが挙げられる。 In the member such as the nozzle for high pressure water flow processing, it is particularly desired that the member has excellent wear resistance. In order to improve the wear resistance, it is effective to increase the hardness. In order to increase the hardness, it is possible to reduce the content of Co, which is lower in hardness than WC, or to make WC fine. To make WC finer, as described in Patent Documents 1 to 3, suppression of grain growth of Cr (chromium) carbides such as VC (vanadium carbide), Mo 2 C (molybdenum carbide), Cr 3 C 2 An effective metal carbide is added.

特開平05-230588号公報Japanese Patent Laid-Open No. 05-230588 特開平09-025535号公報JP 09-025535 特開平04-348873号公報Japanese Patent Laid-Open No. 04-348873

昨今、上記ノズルや金型などの構成材料として、高硬度であると共に、靭性及び強度にも優れ、耐摩耗性と耐欠損性(耐チッピング性)とをバランスよく具える超硬合金が望まれている。しかし、従来の超硬合金は、高硬度、高靭性、及び高強度を十分に、かつバランスよく具えているとは言えない。   Recently, as a constituent material for the nozzles and molds, a cemented carbide having high hardness, excellent toughness and strength, and having a good balance between wear resistance and chipping resistance (chipping resistance) is desired. ing. However, it cannot be said that conventional cemented carbide has sufficient hardness and high toughness and high strength in a well-balanced manner.

特許文献1〜3に記載されるように、超硬合金中のWCの微細化のために粒成長の抑制効果がある金属炭化物を原料として添加すると、得られた超硬合金中に上記金属炭化物が残存したり、再析出することで、強度の低下を招く。また、原料の上記金属炭化物自体が粗大であると、原料のWC粉末に均一に混合することが難しく、WCの粒成長の抑制効果にばらつきが生じて、超硬合金中に成長して粗大になったWCが存在したり、超硬合金中に粗大な金属炭化物が存在し易くなる恐れがある。原料のWC粉末、及び上記金属炭化物を十分に混合するために、原料の混合時間を長くすると、上記WC粉末が過剰に粉砕され、焼結中にオストワルド成長によりWCが成長し易くなり、粗大なWCが存在する超硬合金となる恐れがある。局所的に粗大なWCが存在することで、強度の低下を招く。   As described in Patent Documents 1 to 3, when a metal carbide having an effect of suppressing grain growth for the refinement of WC in the cemented carbide is added as a raw material, the metal carbide is added to the obtained cemented carbide. Remains or reprecipitates, causing a decrease in strength. In addition, if the metal carbide itself of the raw material is coarse, it is difficult to uniformly mix with the raw material WC powder, resulting in variations in the effect of suppressing the grain growth of WC, and it grows coarsely in the cemented carbide. There is a risk that WC becomes present or coarse metal carbide is likely to exist in the cemented carbide. In order to sufficiently mix the WC powder of the raw material and the metal carbide, if the mixing time of the raw material is lengthened, the WC powder is excessively pulverized, and WC grows easily due to Ostwald growth during sintering. There is a risk of becoming a cemented carbide with WC. The presence of locally coarse WC causes a decrease in strength.

また、レンズ用金型には、耐摩耗性に優れることに加えて、金型による形成だけで面品位が高いレンズが得られることが望まれる。即ち、金型により形成されたレンズに、別途研磨処理などを施さずそのままの状態で使用可能な程度に表面性状に優れるレンズが形成できる金型が望まれる。このような要望に対応するためには、金型を構成する超硬合金中のWCが微粒でかつ均質であることが望まれる。   In addition to being excellent in wear resistance, it is desired that a lens having a high surface quality can be obtained only by forming with a mold. That is, there is a demand for a mold that can form a lens that is excellent in surface properties to such an extent that it can be used as it is without being subjected to a separate polishing process or the like. In order to meet such a demand, it is desired that WC in the cemented carbide constituting the mold is fine and homogeneous.

特許文献1に記載される硬質合金には、W2Cが存在する。W2Cは、WCよりも粒成長し易いことから、超硬合金中に粗大なW2Cが存在する恐れがある。超硬合金中に粗大な粒子が存在すると、強度や靭性の低下、面品位の低下を招く。 In the hard alloy described in Patent Document 1, W 2 C exists. Since W 2 C grows more easily than WC, coarse W 2 C may be present in the cemented carbide. If coarse particles are present in the cemented carbide, the strength and toughness are lowered, and the surface quality is lowered.

特許文献2に記載される焼結硬質材は、高硬度化を目的として、低硬度なCoを非常に少なく添加しているため、強度や靭性が低い。また、Coが少な過ぎることで、W2Cが析出され易い上に、焼結性が悪いことから緻密化のために1700℃以上といった非常に高温で焼結する必要がある。このような高温で焼結するために析出されたW2Cが成長し易く、上述のように金属炭化物を添加しても粒成長の抑制効果に限界がある。そして、超硬合金中に粗大なW2Cが存在すると、強度や靭性の低下、面品位の低下を招く。従って、この焼結硬質材では、高硬度、高靭性、及び高強度の両立ができない。 The sintered hard material described in Patent Document 2 has low strength and toughness because it adds very low amount of Co for the purpose of increasing hardness. Further, when Co is too small, W 2 C is likely to be precipitated and, since the sinterability is poor, it is necessary to sinter at a very high temperature of 1700 ° C. or higher for densification. Precipitated W 2 C is likely to grow because of sintering at such a high temperature, and there is a limit to the effect of suppressing grain growth even if metal carbide is added as described above. If coarse W 2 C is present in the cemented carbide, strength, toughness and surface quality are deteriorated. Therefore, this sintered hard material cannot achieve both high hardness, high toughness, and high strength.

特許文献3に記載される焼結体は、耐アブレシブ摩耗性の向上を目的とし、高硬度であるものの強度や靭性が低い。特に、Coの添加が少ない焼結体では、抗折力が低い。また、特許文献3では、WCの平均粒径を単に小さくすることを提案するだけであり、粒度分布の制御について検討されていない。焼結体中のWCの粒径のばらつきが大きいと、焼結体中のCoの厚さが不均一になり(局所的に厚くなったり薄くなったりし)、偏摩耗や欠損の原因となる。また、粒成長を抑制するために原料に用いた複炭化物(異種金属炭化物)が析出されると、この複炭化物がCoなどの結合相との濡れ性が悪いことで、強度の低下を招いたり、析出した複炭化物が脱落することで摩耗が進行し易くなる。従って、この焼結体では、高硬度、高靭性、及び高強度の両立ができない。   The sintered body described in Patent Document 3 aims to improve the abrasive wear resistance, and has high hardness but low strength and toughness. In particular, the bending strength is low in a sintered body with little Co addition. Patent Document 3 only proposes to reduce the average particle diameter of WC, and does not discuss control of the particle size distribution. If the variation in the particle size of WC in the sintered body is large, the Co thickness in the sintered body becomes non-uniform (locally thickens or thins), causing uneven wear and defects. . In addition, when double carbide (dissimilar metal carbide) used as a raw material is precipitated to suppress grain growth, the double carbide has poor wettability with a binder phase such as Co, leading to a decrease in strength. As the precipitated double carbide falls off, the wear easily proceeds. Therefore, this sintered body cannot achieve both high hardness, high toughness, and high strength.

そこで、本発明の目的は、高硬度、高靭性、及び高強度をバランスよく具える超硬合金を提供することにある。   Accordingly, an object of the present invention is to provide a cemented carbide having a good balance of high hardness, high toughness, and high strength.

本発明者らは、特定の組成とすると共に、原料の調整及び製造方法を工夫することで、高硬度で耐摩耗性に優れると共に、高靭性及び高強度で耐欠損性にも優れる超硬合金が得られる、との知見を得た。本発明は、上記知見に基づくものである。   The inventors of the present invention have a specific composition and devise a raw material adjustment and manufacturing method, so that it has high hardness and excellent wear resistance, and has high toughness, high strength and excellent fracture resistance. I got the knowledge that The present invention is based on the above findings.

本発明の超硬合金は、Co及びCrを含有し、残部がWとCとの二元化合物及び不純物から構成される。上記Coは、当該超硬合金に対して0.2質量％以上0.9質量％以下含有する。Coは、CoxWyCzの状態で存在する。上記Crは、当該超硬合金に対して0.2質量％以上1.5質量％以下含有する。そして、上記WとCとの二元化合物は、主としてWCであり、上記超硬合金中のWCの平均粒度が0.2μm以上0.7μm以下、かつWCの粒度の標準偏差σがσ≦0.25を満たす。   The cemented carbide of the present invention contains Co and Cr, and the balance is composed of a binary compound of W and C and impurities. The Co is contained in an amount of 0.2% by mass to 0.9% by mass with respect to the cemented carbide. Co exists in the state of CoxWyCz. The Cr is contained in an amount of 0.2% by mass to 1.5% by mass with respect to the cemented carbide. The binary compound of W and C is mainly WC, the average grain size of WC in the cemented carbide is 0.2 μm or more and 0.7 μm or less, and the standard deviation σ of the grain size of WC satisfies σ ≦ 0.25. .

本発明超硬合金は、金属Coに比べて高硬度なCo化合物(CoxWyCz)を主たる結合相とし、かつWCが微細であることで、硬度が高く、耐摩耗性に優れる。特に、本発明超硬合金は、Crを含有することで、WCの粒成長を効果的に抑えて微細なWCとすることができ、硬度を向上できる上に、粗大なWCの存在による強度の低下を抑制できる。また、本発明超硬合金では、結合相(主としてCoxWyCz)によりWCの周囲を十分に覆うことが可能な程度にCo成分を含有していることから焼結性が高い。そのため、焼結温度が高い特許文献2,3と比較して、本発明超硬合金の製造にあたり、焼結温度を低くすることができることから、局所的なWCなどの粒成長を抑制して、超硬合金中に粗大なWCなどが存在し難い。更に、本発明超硬合金中のCrは、主として金属成分で存在し、炭化物といった化合物の状態でほとんど存在しない。そのため、本発明超硬合金では、粒成長を抑制するために原料に金属炭化物を用いた場合のように金属炭化物が残留したり、再析出したりすることによる強度の低下が実質的に生じ得ない。かつ、本発明超硬合金は、上記特定の範囲でCo成分を含有することで、Coが少な過ぎる超硬合金のような靭性及び強度の極端な低下を低減でき、強度及び靭性も高い。また、上述のように微細で均一的なWCの周囲を覆うように結合相(主としてCoxWyCz)が存在することで、結合相の厚さも均一的であることから、本発明超硬合金は、偏摩耗や欠損が生じ難く、耐摩耗性や耐欠損性に優れる。   The cemented carbide according to the present invention has a Co compound (CoxWyCz) whose hardness is higher than that of metal Co as a main binder phase and fine WC, so that the hardness is high and the wear resistance is excellent. In particular, the cemented carbide according to the present invention can effectively reduce the grain growth of WC to contain fine WC by containing Cr, thereby improving the hardness and improving the strength due to the presence of coarse WC. Reduction can be suppressed. Further, the cemented carbide of the present invention has high sinterability because it contains a Co component to the extent that the surrounding of WC can be sufficiently covered with the binder phase (mainly CoxWyCz). Therefore, compared to Patent Documents 2 and 3 having a high sintering temperature, the production of the cemented carbide of the present invention can reduce the sintering temperature, thereby suppressing local grain growth such as WC, Coarse WC is unlikely to exist in the cemented carbide. Furthermore, Cr in the cemented carbide of the present invention is present mainly as a metal component and hardly exists in the state of a compound such as carbide. For this reason, in the cemented carbide of the present invention, the strength of the metal carbide may be substantially reduced due to the metal carbide remaining or reprecipitating as in the case of using the metal carbide as a raw material in order to suppress grain growth. Absent. In addition, the cemented carbide of the present invention contains a Co component in the above specific range, so that an extreme decrease in toughness and strength like a cemented carbide with too little Co can be reduced, and the strength and toughness are also high. In addition, since the binder phase (mainly CoxWyCz) exists so as to cover the periphery of the fine and uniform WC as described above, the thickness of the binder phase is uniform, so that the cemented carbide of the present invention has a bias. Abrasion and chipping hardly occur, and has excellent wear resistance and chipping resistance.

上述のように本発明超硬合金は、高硬度、高靭性、及び高強度をバランスよく具え、耐摩耗性及び耐欠損性の双方に優れる。また、低Co組成であり、CoがCoxWyCzの状態で存在する本発明超硬合金は、室温だけでなく高温、例えば、500℃〜800℃といった温度域でも硬度の低下が少なく高硬度であり、室温から高温に亘る広い範囲においても耐摩耗性に優れる。従って、本発明超硬合金は、例えば、耐摩耗性に優れることが望まれる部材、例えば高圧水流加工用のノズルの構成材料に好適に利用することができる。また、本発明超硬合金は、WCが微細で均一的であり、結合相(主としてCoxWyCz)の厚さも均一的である。即ち、本発明超硬合金は、組織が均一的であり、Co成分が比較的少ないことから、耐摩耗性に加えて、鏡面仕上げといった良好な仕上げ面品位が求められる部材、例えばガラスレンズの金型の構成材料にも好適に利用することができる。そして、本発明超硬合金は、高靭性で高強度であることから、上記ノズルや金型などを製造する際に研削、ワイヤ加工、放電加工などが施されても、これらの加工に伴う加工亀裂やチッピングを低減することができ、上記ノズルなどの部材を生産性よく製造することができる。また、本発明超硬合金は、上述のように高強度で高靭性であることから、上記各種の部材の使用時に亀裂やチッピングが生じ難く、耐欠損性にも優れる。以下、本発明を詳細に説明する。   As described above, the cemented carbide of the present invention has a high balance of high hardness, high toughness, and high strength, and is excellent in both wear resistance and fracture resistance. In addition, the cemented carbide of the present invention having a low Co composition and Co in the state of CoxWyCz is not only at room temperature but also at a high temperature, for example, at a temperature range of 500 ° C. to 800 ° C. Excellent wear resistance in a wide range from room temperature to high temperature. Therefore, the cemented carbide of the present invention can be suitably used as a constituent material of, for example, a member that is desired to have excellent wear resistance, for example, a nozzle for high pressure water flow processing. Further, the cemented carbide of the present invention has a fine and uniform WC, and the thickness of the binder phase (mainly CoxWyCz) is also uniform. That is, the cemented carbide of the present invention has a uniform structure and a relatively small Co component. Therefore, in addition to wear resistance, a member that requires a good finished surface quality such as a mirror finish, such as a glass lens metal, is used. It can utilize suitably also for the constituent material of a type | mold. Since the cemented carbide of the present invention has high toughness and high strength, even if grinding, wire machining, electric discharge machining, or the like is performed when manufacturing the nozzle or mold, the machining associated with these machining is performed. Cracks and chipping can be reduced, and members such as the nozzle can be manufactured with high productivity. In addition, since the cemented carbide of the present invention has high strength and high toughness as described above, cracks and chipping hardly occur during use of the above-mentioned various members, and excellent fracture resistance. Hereinafter, the present invention will be described in detail.

＜超硬合金＞
《組成》
本発明超硬合金は、硬質相が主としてWCの粒子から構成され、結合相が主としてCo化合物(CoxWyCz)から構成されるWC-CoxWyCz系超硬合金であり、CoxWyCz及び後述するCrを除く残部がWとCとの二元化合物と不可避的な不純物とにより構成される。更に後述するVを含む場合は、CoxWyCz、Cr及びVを除く残部がWとCとの二元化合物と不可避的な不純物とにより構成される。WとCとの二元化合物には、WC、W2Cが挙げられる。 <Cemented carbide>
"composition"
The cemented carbide of the present invention is a WC-CoxWyCz cemented carbide in which the hard phase is mainly composed of WC particles and the binder phase is mainly composed of a Co compound (CoxWyCz). It is composed of binary compounds of W and C and inevitable impurities. Further, when V described later is included, the remainder excluding CoxWyCz, Cr and V is composed of a binary compound of W and C and unavoidable impurities. Examples of binary compounds of W and C include WC and W 2 C.

[Co]
本発明超硬合金中におけるCoは、CoxWyCzというCoとWとの化合物の状態で存在する。後述する実施例において本発明超硬合金をX線回折により分析した結果、Coを含む成分のピーク波形は、CoxWyCzのピーク波形が得られ、金属Coのピーク波形は検出限界により得られなかった。また、CoxWyCz中にCrやVが固溶されている場合、CoxWyCzのピーク波形からピーク位置がややずれたピーク波形が得られると考えられる。従って、超硬合金をX線回折により分析した場合にCrやVを固溶することによりCoxWyCzのピーク波形がややずれた場合も、金属Coのピーク波形が得られない超硬合金は、本発明の範囲に含有されると解釈する。後述する製造方法によれば、超硬合金中のCoの実質的に全てがCoxWyCzとして存在し、金属Coが存在しない(金属CoのX線回折によるピーク波形が検出限界により得られない)超硬合金を製造することができる。x,y,zは、いずれも正の値をとり、x+y＞zを満たす。 [Co]
Co in the cemented carbide of the present invention exists in the state of a compound of Co and W called CoxWyCz. As a result of analyzing the cemented carbide of the present invention by X-ray diffraction in Examples to be described later, the peak waveform of the component containing Co was obtained as the peak waveform of CoxWyCz, and the peak waveform of metal Co was not obtained due to the detection limit. Further, when Cr or V is dissolved in CoxWyCz, it is considered that a peak waveform having a peak position slightly deviated from the peak waveform of CoxWyCz can be obtained. Therefore, when the cemented carbide is analyzed by X-ray diffraction, even if the peak waveform of CoxWyCz is slightly shifted due to solid solution of Cr or V, the cemented carbide that does not obtain the peak waveform of Co is the present invention. It is interpreted that it is contained in the range. According to the manufacturing method described later, substantially all of Co in the cemented carbide is present as CoxWyCz, and there is no metal Co (the peak waveform due to X-ray diffraction of metal Co cannot be obtained due to detection limit). Alloys can be manufactured. x, y, and z all take positive values and satisfy x + y> z.

本発明超硬合金は、当該超硬合金に対してCoを0.2質量％以上含有することでCoxWyCzを十分に生成して、WCの周囲を覆うことができ、焼結性に優れる。そのため、本発明超硬合金を製造するにあたり、焼結温度を通常の超硬合金と同程度、例えば、通常の減圧焼結と同程度の焼結条件で焼結を行っても緻密な超硬合金とすることができる。Coが0.2質量％未満では、CoxWyCzによりWCの周囲を十分に覆いきれず焼結性が低下するため、焼結温度を高くする必要があり、焼結温度の高温化により、焼結時にWCの粒成長を促進して粗大なWCの発生を招く。そして、粗大な粒子の存在による強度の低下を招く。また、Coが少な過ぎると靭性(例えば、破壊靱性)も極端に低下する。Coが多いほど、靭性の向上、焼結性の向上に効果があるが、0.9質量％を超えると、WCの粒成長が起こり易くなることから硬度(室温から高温に亘る硬度)が低下し、特に、600℃以上の高温域での硬度の低下が著しい。また、WCの粒成長により、超硬合金の組織の均一性も低下することから、強度の低下も招く。Coの含有量を0.2質量％以上0.9質量％以下とすることで、焼結温度の高温化によるWCのオストワルド成長を抑制し、超硬合金中に粗大なWCの発生を低減して、WCの粒度が微粒で均一的なWC-CoxWyCz系超硬合金とすることができる。また、本発明超硬合金は、微細な組織を有することから表面性状に優れる。特にCoの成分を少なめにすると共にその存在状態をCoxWyCzとすることで、高温で使用される場合であっても、超硬合金の表面からCoが溶出し難く、超硬合金の表面の鏡面状態を長く維持することができる。Coの含有量は、0.2質量％以上0.6質量％以下がより好ましい。   The cemented carbide of the present invention contains Co in an amount of 0.2% by mass or more with respect to the cemented carbide, can sufficiently generate CoxWyCz and can cover the periphery of WC, and is excellent in sinterability. Therefore, in producing the cemented carbide of the present invention, even if the sintering temperature is the same as that of ordinary cemented carbide, for example, under the same sintering conditions as that of ordinary reduced pressure sintering, a dense cemented carbide is obtained. It can be an alloy. If Co is less than 0.2% by mass, CoxWyCz cannot sufficiently cover the periphery of WC and the sinterability deteriorates. Therefore, it is necessary to increase the sintering temperature. It promotes grain growth and leads to generation of coarse WC. In addition, the strength is reduced due to the presence of coarse particles. Moreover, when there is too little Co, toughness (for example, fracture toughness) will also fall extremely. The more Co, the more effective to improve toughness and sinterability, but when it exceeds 0.9% by mass, the WC grain growth tends to occur, so the hardness (hardness from room temperature to high temperature) decreases, In particular, the decrease in hardness at a high temperature range of 600 ° C. or higher is remarkable. In addition, the grain growth of WC also reduces the uniformity of the structure of the cemented carbide, resulting in a decrease in strength. By setting the Co content to 0.2 mass% or more and 0.9 mass% or less, the Ostwald growth of WC due to the high sintering temperature is suppressed, and the generation of coarse WC in the cemented carbide is reduced. A uniform WC-CoxWyCz cemented carbide can be obtained. In addition, the cemented carbide of the present invention has a fine structure and thus has excellent surface properties. In particular, by reducing the amount of Co and making its presence state CoxWyCz, even when used at high temperatures, it is difficult for Co to elute from the surface of the cemented carbide, and the specular state of the surface of the cemented carbide Can be maintained for a long time. The Co content is more preferably 0.2% by mass or more and 0.6% by mass or less.

[Cr]
Crを超硬合金に対して0.2質量％以上含有することで、WCの粒成長を効果的に抑えて粗大なWCの発生を低減し、微細で均一的な大きさのWCが均一的に存在する超硬合金を安定して製造することができる。また、Crを含有することで、超硬合金の耐酸化性を向上することができる。Crが多いほど、粒成長の抑制効果が高められるが、Crが多過ぎると、Cr炭化物として析出し易くなり、Cr炭化物の存在による強度の低下の要因となる。そこで、本発明超硬合金は、Crの含有量を0.2質量％以上1.5質量％以下とする。より好ましいCrの含有量は、0.2質量％以上0.9質量％以下である。 [Cr]
By containing 0.2% by mass or more of Cr with respect to the cemented carbide, the grain growth of WC is effectively suppressed, the generation of coarse WC is reduced, and fine and uniform size WC exists uniformly. The cemented carbide can be manufactured stably. Moreover, the oxidation resistance of a cemented carbide can be improved by containing Cr. As the amount of Cr is increased, the effect of suppressing grain growth is enhanced. However, when the amount of Cr is excessive, precipitation as Cr carbide tends to occur, which causes a decrease in strength due to the presence of Cr carbide. Therefore, the cemented carbide of the present invention has a Cr content of 0.2 mass% or more and 1.5 mass% or less. A more preferable Cr content is 0.2 mass% or more and 0.9 mass% or less.

Crに加えて、更に、本発明超硬合金は、Vを含有していてもよい。VもCrと同様にWCの粒成長の抑制効果が高く、CrとVとの双方を含有することで、WCの粒成長を更に効果的に抑えられる。Vの含有量が多過ぎると、WCやW2CとCoxWyCzとの濡れ性が悪くなり、焼結性が低下することから超硬合金の強度が低下したり、V炭化物として析出し易くなり、V炭化物の存在による強度の低下の要因となる。そのため、Vの含有量は、超硬合金に対して0.2質量％以下(0質量％を含む)が好ましい。 In addition to Cr, the cemented carbide of the present invention may further contain V. V, like Cr, is highly effective in suppressing grain growth of WC, and by containing both Cr and V, grain growth of WC can be more effectively suppressed. If the V content is too large, the wettability of WC, W 2 C and CoxWyCz will be poor, and the sinterability will be reduced, so the strength of the cemented carbide will be reduced, and it will be easy to precipitate as V carbide, V Causes the strength to decrease due to the presence of carbides. Therefore, the content of V is preferably 0.2% by mass or less (including 0% by mass) with respect to the cemented carbide.

上記Crや上記Vは、実質的に全てがCoxWyCz中やWC中に固溶して、金属成分として存在することが好ましい。後述する実施例において本発明超硬合金をX線回折により分析した結果、Cr炭化物のピーク波形やV炭化物のピーク波形は検出限界により得られない範囲にある。このことから、超硬合金中のCrやVは、CoxWyCz中やWC中に固溶されていると考えられる。従って、超硬合金をX線回折により分析した場合に純粋なCoxWyCzのピーク波形からずれたピーク波形を有する超硬合金は、本発明の範囲に含有されると解釈する。後述する製造方法によれば、超硬合金中のCrやVの実質的に全てがCoxWyCz中やWC中に固溶した金属成分として存在し、CrやVの金属単体、及びCr炭化物やV炭化物が存在しない(Cr炭化物やV炭化物のX線回折のピーク波形が検出限界により得られない)超硬合金を製造することができる。   It is preferable that substantially all of the Cr and V are dissolved as solid components in CoxWyCz or WC and exist as metal components. As a result of analyzing the cemented carbide of the present invention by X-ray diffraction in Examples to be described later, the peak waveform of Cr carbide and the peak waveform of V carbide are in a range that cannot be obtained due to the detection limit. From this, it is considered that Cr and V in the cemented carbide are dissolved in CoxWyCz and WC. Accordingly, when a cemented carbide is analyzed by X-ray diffraction, a cemented carbide having a peak waveform deviated from that of a pure CoxWyCz is interpreted as being included in the scope of the present invention. According to the manufacturing method described later, substantially all of Cr and V in the cemented carbide exist as a metal component dissolved in CoxWyCz and WC, Cr and V simple metals, Cr carbide and V carbide It is possible to produce a cemented carbide that does not exist (the peak waveform of X-ray diffraction of Cr carbide or V carbide cannot be obtained due to the detection limit).

[WとCとの二元化合物]
本発明超硬合金は、CoxWyCz,Cr,(V)を除く残部がWとCとの二元化合物及び不可避的な不純物により構成される。WとCとの二元化合物のうち、特に、WCの含有量が当該超硬合金に対して97質量％以上である。このWCは、超硬合金中に粒状で存在して、硬質相として機能する。特に、WCは、微粒である上に均一的な大きさである。具体的には、WCの平均粒度が0.2μm以上0.7μm以下であり、粒度の標準偏差σが0.25以下である。平均粒度が上記範囲を満たし、かつ標準偏差が上記範囲を満たすことで、微細なWCにより硬度を高められると共に、粗大なWCが少ないことにより強度の低下を低減することができる。平均粒度が0.2μm未満と小さ過ぎると、亀裂が進展し易く、靭性の低下を招き、平均粒度が0.7μm超であると、硬度の低下を招く。より好ましい平均粒度は、0.2μm以上0.4μm以下である。標準偏差σは小さい方が好ましく、特に下限を設けない。 [Binary compound of W and C]
In the cemented carbide of the present invention, the balance excluding CoxWyCz, Cr, (V) is composed of a binary compound of W and C and inevitable impurities. Among the binary compounds of W and C, in particular, the content of WC is 97% by mass or more with respect to the cemented carbide. This WC exists in a granular form in the cemented carbide and functions as a hard phase. In particular, WC is fine and has a uniform size. Specifically, the average particle size of WC is 0.2 μm or more and 0.7 μm or less, and the standard deviation σ of the particle size is 0.25 or less. When the average particle size satisfies the above range and the standard deviation satisfies the above range, the hardness can be increased by fine WC, and the decrease in strength can be reduced by reducing the amount of coarse WC. If the average particle size is too small as less than 0.2 μm, cracks are likely to progress and the toughness is reduced, and if the average particle size is more than 0.7 μm, the hardness is reduced. A more preferable average particle size is 0.2 μm or more and 0.4 μm or less. The standard deviation σ is preferably small, and no lower limit is particularly set.

超硬合金中に粗大なWCが少ないことが好ましい。具体的には、粒度(粒径)が1.0μm以上であるWCの面積割合が、当該超硬合金に対して5％以下であると、上述したように粗大なWCの存在による強度の低下を抑えて、高強度な超硬合金となり得る。上記粗大なWCの面積割合は、小さい方が好ましく、4％以下がより好ましい。   It is preferable that there is little coarse WC in the cemented carbide. Specifically, when the area ratio of WC having a particle size (particle diameter) of 1.0 μm or more is 5% or less with respect to the cemented carbide, the strength is reduced due to the presence of coarse WC as described above. Suppressing, it can become a high strength cemented carbide. The area ratio of the coarse WC is preferably smaller, and more preferably 4% or less.

超硬合金中に存在するW及びCは、その大部分がWCで存在し、W2Cが少ないことが好ましい。上述のようにW2CはWCよりも粒成長し易いため、粗大な粒子が存在する超硬合金となり得る。具体的には、体積割合で、W2C/(WC+W2C)≦0.005以下を満たすことが好ましい。上記W2Cの体積割合は、小さい方が好ましく、存在しない、即ち、WとCとの二元化合物がWCのみであることが望ましい。 Most of the W and C present in the cemented carbide is present in WC, and it is preferable that W 2 C is small. As described above, since W 2 C grows more easily than WC, it can be a cemented carbide containing coarse particles. Specifically, the volume ratio preferably satisfies W 2 C / (WC + W 2 C) ≦ 0.005 or less. The volume ratio of W 2 C is preferably small and is not present, that is, it is desirable that the binary compound of W and C is only WC.

上述したWCの平均粒度、粒度の標準偏差、及び粗大なWCの面積割合は、例えば、EBSD法を利用することで、W2Cの体積割合は、X線回折を利用することで簡単に求められる。これらの測定方法の詳細は後述する。 The average particle size of WC, the standard deviation of particle size, and the area ratio of coarse WC are obtained, for example, by using the EBSD method, and the volume ratio of W 2 C is easily obtained by using X-ray diffraction. It is done. Details of these measurement methods will be described later.

[特性]
本発明超硬合金は、高硬度、高靭性、及び高強度である。具体的には、HRA硬度が94以上96以下、破壊靱性が4MPa・m1/2以上、抗折力が1GPa以上であることが好ましい。HRA硬度が94以上であることで、耐摩耗性に優れ、HRA硬度が96以下であることで、過度な高硬度化による靭性の低下を低減できる。また、破壊靱性が4MPa・m1/2以上及び抗折力が1GPa以上であることで、各種の部材の製造にあたり、加工時の亀裂やチッピングを効果的に抑えられ、かつ高硬度な上に、高靭性及び高強度である超硬合金本来の優れた性能を具える部材を提供することができる。 [Characteristic]
The cemented carbide of the present invention has high hardness, high toughness, and high strength. Specifically, it is preferable that the HRA hardness is 94 or more and 96 or less, the fracture toughness is 4 MPa · m 1/2 or more, and the bending strength is 1 GPa or more. When the HRA hardness is 94 or more, the wear resistance is excellent, and when the HRA hardness is 96 or less, a decrease in toughness due to excessively high hardness can be reduced. In addition, because the fracture toughness is 4 MPa · m 1/2 or more and the bending strength is 1 GPa or more, cracks and chipping during processing can be effectively suppressed and the hardness is high. It is possible to provide a member having excellent performance inherent to a cemented carbide having high toughness and high strength.

＜製造方法＞
超硬合金は、一般に、原料の準備→原料の混合・粉砕→乾燥→成形→焼結という工程で製造される。本発明超硬合金は、上記焼結後に、更にHIP(熱間静水圧焼結)を行うと共に、特定の原料の利用、及び特定の条件での混合・粉砕を行う。 <Manufacturing method>
Cemented carbide is generally manufactured in the process of raw material preparation → mixing and grinding of raw materials → drying → molding → sintering. The cemented carbide of the present invention is further subjected to HIP (hot isostatic pressing) after the above-mentioned sintering, as well as using specific raw materials and mixing / pulverizing under specific conditions.

[原料WC]
原料のWC粉末は、超硬合金中のWCが微細な状態になり易いように、微細なものを利用することが好ましい。具体的には、平均粒度が0.1μm以上0.5μm以下のWC粉末が好ましい。0.1μm未満でも0.5μm超でも粒成長して粗大なWCが存在する超硬合金が形成され易い。 [Raw material WC]
As the raw material WC powder, it is preferable to use a fine one so that the WC in the cemented carbide is likely to be in a fine state. Specifically, WC powder having an average particle size of 0.1 μm to 0.5 μm is preferable. Even if it is less than 0.1 μm or more than 0.5 μm, a cemented carbide having grain growth and coarse WC is easily formed.

特に、原料のWC粉末は、Crを含有したものを使用すると、超硬合金中にCr炭化物が生成され難い。Cr及びVを含有する超硬合金を製造する場合、原料として、Cr及びVを含有したWC粉末を使用すると、超硬合金中にCr炭化物やV炭化物が生成され難い。本発明者らは、原料にCr炭化物やV炭化物の粉末、金属Crや金属Vの粉末を用いると、Cr炭化物やV炭化物が残存したり析出・再析出したりして、強度の低下を招く、との知見を得た。一方、WC粉末自体にCrやVを含有している場合、Cr炭化物やV炭化物が析出され難い、又は実質的に生成されない上に、原料全体に亘りCrやVを均一的に存在させる(分散させる)ことができるため、焼結時のWCの粒成長を超硬合金全体に亘って均一的に抑えられ、微粒で均一的な粒度のWCが均一的に存在する組織の超硬合金を安定して製造できる、との知見を得た。また、WC粉末自体がCrやVを含有していることで、WC中にCrやVが固溶した状態の超硬合金が得られ易い、との知見を得た。更に、VCといった焼結性を低下させる化合物を原料に利用しないことで、焼結性の悪化を回避できる。これらの知見に基づき、CrやVを含有したWC粉末を用いることを提案する。なお、原料のWC粉末中に含有して添加されたCrやVの含有量は、超硬合金中の含有量に実質的に等しい。   In particular, when a raw material WC powder containing Cr is used, it is difficult to produce Cr carbide in the cemented carbide. When manufacturing a cemented carbide containing Cr and V, if WC powder containing Cr and V is used as a raw material, Cr carbide and V carbide are hardly generated in the cemented carbide. When the present inventors use Cr carbide or V carbide powder, metal Cr or metal V powder as a raw material, Cr carbide or V carbide remains, precipitates, or reprecipitates, resulting in a decrease in strength. , And got the knowledge. On the other hand, when the WC powder itself contains Cr and V, Cr carbide and V carbide are hardly precipitated or are not substantially formed, and Cr and V are uniformly present throughout the raw material (dispersion). Therefore, the grain growth of WC during sintering can be uniformly suppressed throughout the cemented carbide, and the cemented carbide with a structure in which fine and uniform grain size WC exists uniformly can be stabilized. And obtained the knowledge that it can be manufactured. In addition, it has been found that the cemented carbide in which WC powder itself contains Cr and V and thus Cr and V are dissolved in WC can be easily obtained. Furthermore, deterioration of sinterability can be avoided by not using as a raw material a compound that lowers sinterability such as VC. Based on these findings, we propose to use WC powder containing Cr and V. Note that the content of Cr and V added in the raw material WC powder is substantially equal to the content in the cemented carbide.

[原料Co]
原料のCo粉末には、微細なWC粉末と均一的に混合され易いように、WC粉末と同程度の微細なものを利用することが好ましい。具体的には、平均粒度が0.2μm以上0.6μm以下のCo粉末が好ましい。0.2μm未満であると、Coが小さ過ぎることで再凝集し易くなってCoが均一的に分散されず、焼結性の低下や、焼結性の低下に伴う焼結温度の高温化によりWCの粒成長を促して、均一的な粒度分布が得られ難くなる。0.6μm超であると、微細なWC粉末と均一的に混合され難くなり、上述のようにCoが不均一に存在することによる焼結性の低下や粒度分布の不均一を招く。 [Raw material Co]
As the raw material Co powder, it is preferable to use a fine powder of the same level as the WC powder so that it can be uniformly mixed with the fine WC powder. Specifically, Co powder having an average particle size of 0.2 μm or more and 0.6 μm or less is preferable. If it is less than 0.2 μm, Co is easy to re-aggregate because Co is too small, and Co is not uniformly dispersed. As a result, sinterability decreases and sintering temperature increases due to decrease in sinterability. It is difficult to obtain a uniform particle size distribution by promoting grain growth. If it exceeds 0.6 μm, it is difficult to uniformly mix with the fine WC powder, and as described above, the non-uniform presence of Co causes a decrease in sinterability and a non-uniform particle size distribution.

[原料カーボン]
上述したCrやV含有のWC粉末及びCo粉末に加えて、適宜カーボン粉末を添加することなどにより、超硬合金中における炭素(C)の総量を調整する。超硬合金中の炭素の総量を調整すると共に、後述する製造条件で製造することで、Co粉末の実質的に全てをCoxWyCzとすることができる上に、得られた超硬合金中の炭素はWC,CoxWyCzとして存在し易い。超硬合金中の炭素の総量が多過ぎると、金属Coが存在し易くなる。また、超硬合金中の炭素の総量が多過ぎると、フリーカーボンとして超硬合金中に存在したり、Cr炭化物などが析出されて、強度の低下を招く。 [Raw material carbon]
In addition to the above-described Cr and V-containing WC powder and Co powder, the total amount of carbon (C) in the cemented carbide is adjusted by adding carbon powder as appropriate. By adjusting the total amount of carbon in the cemented carbide and manufacturing under the production conditions described later, substantially all of the Co powder can be made CoxWyCz, and the carbon in the obtained cemented carbide is It tends to exist as WC and CoxWyCz. When the total amount of carbon in the cemented carbide is too large, metal Co tends to exist. If the total amount of carbon in the cemented carbide is too large, it will be present in the cemented carbide as free carbon, or Cr carbide will be precipitated, leading to a decrease in strength.

[混合・粉砕]
上述した原料となる粉末を用意し、アトライター、ボールミル、ビーズミルといった回転翼を有する粉砕分散機により、混合・粉砕を行う。混合・粉砕の時間は10時間以上20時間以下が好ましい。特に、混合・粉砕の開始から5時間までの初期工程を高速回転(25r.p.m.以上)で行い、以降の混合・粉砕(以下、後工程と呼ぶ)を低速回転(25r.p.m.未満)で行うことが好ましい。初期工程で概ねの混合・粉砕を完了し、後工程では、主として分散を行う。このように混合・粉砕工程を多段にすることで、均一的な混合、分散を実現し易い。混合・粉砕工程の全体に亘って高速回転で行うと、Coの凝集が生じて分散状態が悪くなり、WCが成長し易くなるなど、組織の不均一化を招く。一方、混合・粉砕工程の全体に亘って低速回転で行うと、粉砕や混合が不十分で組織の不均一化を招く。 [Mixing / Crushing]
The above-mentioned raw material powder is prepared, and mixed and pulverized by a pulverizing / dispersing machine having rotating blades such as an attritor, a ball mill, and a bead mill. The mixing and grinding time is preferably 10 hours or more and 20 hours or less. In particular, the initial process from the start of mixing / pulverization to 5 hours is performed at high speed rotation (25 rpm or more), and the subsequent mixing / pulverization (hereinafter referred to as post-process) is performed at low speed (less than 25 rpm). It is preferable. In the initial step, the mixing and pulverization is generally completed, and in the subsequent step, dispersion is mainly performed. Thus, it is easy to realize uniform mixing and dispersion by making the mixing and pulverization process multistage. If the entire mixing and pulverization process is performed at high speed, Co agglomerates, the dispersion state becomes poor, and WC tends to grow, resulting in a non-uniform structure. On the other hand, if the mixing and pulverization process is performed at a low speed, the pulverization and mixing are insufficient and the structure becomes non-uniform.

上記乾燥、成形、焼結などは、一般的な条件と同等程度の条件を利用することができる。例えば、焼結条件は、焼結温度:1450〜1550℃での減圧焼結(真空焼結、Ar雰囲気焼結、CO雰囲気焼結など)が挙げられる。本発明超硬合金は、上述のように原料に微粒のWC粉末及びCo粉末を用いて上述の組成に配合し、更に上述のように特定の条件で混合・粉砕を行って適切に分散させることで、WCの周囲をCoxWyCzが十分に覆えることから、焼結温度を上記のように比較的低めにすることができる。焼結温度が低いことで、WC(W2C)の粒成長を抑制することができる。 For the drying, molding, sintering, etc., conditions comparable to general conditions can be used. For example, the sintering conditions include sintering under reduced pressure at a sintering temperature of 1450 to 1550 ° C. (vacuum sintering, Ar atmosphere sintering, CO atmosphere sintering, etc.). The cemented carbide of the present invention is mixed with the above composition using fine WC powder and Co powder as raw materials as described above, and further mixed and pulverized under specific conditions as described above to be appropriately dispersed. Then, since CoxWyCz can sufficiently cover the periphery of WC, the sintering temperature can be made relatively low as described above. Since the sintering temperature is low, the grain growth of WC (W 2 C) can be suppressed.

本発明超硬合金の製造では、上記焼結後にHIPを行う。ここで、一般に、Coが比較的少ない超硬合金では、WCの周囲にCoが十分に回り切らないため、焼結し易いように高温で焼結する(特許文献2:1700℃以上、特許文献3:1600℃以上)ことが必要となる。これに対して、本発明超硬合金の製造では、上述のように低温でも十分に焼結性がよく、均一的な組織の超硬合金が得られる。また、焼結後にHIPを行うことで、焼結後の超硬合金中に残存する微細な巣(ポア)を消滅することができ、緻密な超硬合金とすることができる。特に、焼結温度を上述のように比較的低目にすることで、均一的な組織の超硬合金を製造し易い。   In manufacturing the cemented carbide of the present invention, HIP is performed after the sintering. Here, in general, a cemented carbide with a relatively small amount of Co does not sufficiently wrap around Co, so it is sintered at a high temperature to facilitate sintering (Patent Document 2: 1700 ° C. or higher, Patent Document 3: 1600 ° C or higher). On the other hand, in the manufacture of the cemented carbide of the present invention, as described above, a cemented carbide having a uniform structure can be obtained with sufficiently good sinterability even at a low temperature. Also, by performing HIP after sintering, the fine nests (pores) remaining in the sintered cemented carbide can be eliminated, and a dense cemented carbide can be obtained. In particular, by making the sintering temperature relatively low as described above, it is easy to manufacture a cemented carbide with a uniform structure.

上述のように、粒成長の抑制のために金属炭化物を用いず、WC粉末自体にCrやVを含有したものを利用し、Coの含有量を最適化すると共に、微細なCo粉末を利用し、かつ上記製造条件で製造することで、超硬合金中のWCを微細で、均一的な粒度分布とすることができ、粗大な粒子の存在による強度の低下を抑制できる。また、上述のように超硬合金中のCoをCoxWyCzとして存在させることができる。   As described above, not using metal carbide to suppress grain growth, but using WC powder itself containing Cr and V, optimizing the Co content, and using fine Co powder And by manufacturing on the said manufacturing conditions, WC in a cemented carbide alloy can be made into fine and uniform particle size distribution, and the fall of the intensity | strength by presence of a coarse particle can be suppressed. Further, as described above, Co in the cemented carbide can be present as CoxWyCz.

本発明超硬合金は、高硬度、高靭性、及び高強度をバランスよく具えるため、優れた耐摩耗性及び優れた耐欠損性を両立することができる。   Since the cemented carbide of the present invention has a high balance of high hardness, high toughness, and high strength, it is possible to achieve both excellent wear resistance and excellent fracture resistance.

EBSD法を用いて観察した試料No.2のマッピング像である。It is a mapping image of sample No. 2 observed using the EBSD method. 試料No.2の超硬合金中のWCの粒度分布を示すグラフである。4 is a graph showing the particle size distribution of WC in a cemented carbide of sample No. 2. EBSD法を用いて観察した試料No.106のマッピング像である。It is a mapping image of sample No. 106 observed using the EBSD method. 試料No.106の超硬合金中のWCの粒度分布を示すグラフである。4 is a graph showing the particle size distribution of WC in a cemented carbide of Sample No. 106.

(試験例)
種々の原料粉末を用意して超硬合金を作製し、得られた超硬合金の組成、組織、機械的特性を調べた。また、この超硬合金から高圧水流加工用ノズルを作製し、ノズルの寿命を調べた。 (Test example)
Various raw material powders were prepared to prepare cemented carbide, and the composition, structure and mechanical properties of the obtained cemented carbide were examined. Moreover, a nozzle for high-pressure water flow processing was produced from this cemented carbide, and the life of the nozzle was examined.

[試料No.1〜5]
原料として、平均粒度が0.5μmのWC粉末、平均粒度が0.2μm及び0.6μmのCo粉末、及びカーボン粉末を用意した。上記WC粉末として、当該WC粉末に対して、Crを0.2〜1.5質量％含有するもの、Crを0.2〜1.5質量％及びVを0.2質量％含有するものを用意した。上記CrやVを含有するWC粉末、Co粉末、及びカーボン粉末の合計質量に対して、Co粉末:0.2〜0.9質量％となるように、カーボン粉末:上記合計質量に対して炭素の含有量が、、製造される各組成の超硬合金の理論炭素量に対してそれぞれプラス0.05質量％以上0.1質量％未満となるように添加量を調整し、残部をWC粉末とした。これらの原料粉末は、いずれも市販のものが利用できる。なお、試料No.1,2には、平均粒径が0.2μmのCo粉末、試料No.3〜5には、平均粒径が0.6μmのCo粉末を用いた。 [Sample Nos. 1-5]
As raw materials, WC powder having an average particle size of 0.5 μm, Co powder having an average particle size of 0.2 μm and 0.6 μm, and carbon powder were prepared. As the WC powder, a WC powder containing 0.2 to 1.5 mass% Cr, 0.2 to 1.5 mass% Cr, and 0.2 mass% V was prepared. The content of carbon relative to the total mass of the carbon powder: the total mass is such that the Co powder is 0.2 to 0.9 mass% with respect to the total mass of the WC powder, Co powder, and carbon powder containing Cr and V. The amount of addition was adjusted so that it would be 0.05 mass% or more and less than 0.1 mass% with respect to the theoretical carbon content of the cemented carbide of each composition to be produced, and the balance was made WC powder. Any of these raw material powders can be used commercially. Sample Nos. 1 and 2 used Co powder with an average particle size of 0.2 μm, and Samples No. 3 to 5 used Co powder with an average particle size of 0.6 μm.

上記原料粉末に、粉末状のパラフィン(原料粉末に対して1質量％)を加えて、アトライター又はボールミルを用いて、混合・粉砕を行った。アトライター、ボールミルのいずれも、メディアに直径φ5mmの超硬合金製ボールを用いた。表1に、用いた粉砕分散機の種別、混合・粉砕時間を示す。特に、試料No.1〜5では、混合・粉砕開始から5時間を高速回転(25r.p.m.以上)で行い、5時間以降の残りの時間を低速(5r.p.m.)で行った。   Powdered paraffin (1% by mass with respect to the raw material powder) was added to the raw material powder, and mixing and pulverization were performed using an attritor or a ball mill. Both the attritor and the ball mill used cemented carbide balls with a diameter of 5 mm for the media. Table 1 shows the types of pulverizing and dispersing machines used, and the mixing and pulverizing time. In particular, in Sample Nos. 1 to 5, 5 hours from the start of mixing and pulverization was performed at a high speed (25 r.p.m. or more), and the remaining time after 5 hours was performed at a low speed (5 r.p.m.).

上記混合・粉砕の後、造粒乾燥機を用いて原料粉末を顆粒状に造粒してから乾燥した。得られた造粒粉末をゴム型に所定の量だけ投入して、静水圧プレスを行った後、得られたプレス体の外周に機械加工を施し、直径φ8mm×長さL:80mmの丸棒材を作製した。得られた丸棒材を焼結炉内に配置し、1450℃〜1550℃×1時間、真空中で保持することにより焼結し、上記加熱温度から冷却した後、焼結炉から取り出した。得られた焼結体に1320℃、1000気圧(約101MPa)のAr雰囲気中でHIPを行い、超硬合金を得た。   After the mixing and pulverization, the raw material powder was granulated into granules using a granulation dryer and then dried. A predetermined amount of the obtained granulated powder is put into a rubber mold and subjected to isostatic pressing, and then the outer periphery of the obtained press body is machined to obtain a round bar having a diameter of 8 mm × length L: 80 mm. A material was prepared. The obtained round bar was placed in a sintering furnace, sintered by being held in a vacuum at 1450 ° C. to 1550 ° C. for 1 hour, cooled from the above heating temperature, and then taken out from the sintering furnace. The obtained sintered body was subjected to HIP in an Ar atmosphere at 1320 ° C. and 1000 atmospheres (about 101 MPa) to obtain a cemented carbide.

得られた超硬合金に、研削加工及び放電加工を施し、外周形状の形成、水を導入する箇所のテーパー部の形成を行うと共に、超硬合金の中央に、その長手方向に延びる貫通孔(直径φ0.5mm)を形成し、高圧水流加工用ノズルを製作した。   The obtained cemented carbide is subjected to grinding and electric discharge machining, forming an outer peripheral shape, forming a tapered portion where water is introduced, and a through-hole extending in the longitudinal direction in the center of the cemented carbide ( A nozzle for high-pressure water flow processing was manufactured.

[試料No.101〜106]
比較として、原料にCr3C2,VC,Mo2Cを用いた試料、Cr3C2,VC,Mo2Cを用いていない試料を作製した。具体的には、原料として、平均粒度が0.7μmのWC粉末(CrやVを含有しないもの)、及びCo粉末、Mo2C粉末、VC粉末、Cr3C2粉末(いずれも平均粒度:0.7〜1.5μm)、並びにカーボン粉末を用意した。これらの原料粉末の添加量を適宜調整して、試料No.1〜5と同様に、混合・粉砕→造粒→乾燥→静水圧プレス→丸棒材の作製→焼結→HIPという工程を経て、超硬合金を得た。試料No.101〜106では、混合・粉砕の全時間に亘って、高速回転(25r.p.m.以上)で混合・粉砕を行い、焼結条件やHIP条件は、試料No.1〜5と同様とした。得られた超硬合金に試料No.1〜5と同様の加工を施して、高圧水流加工用ノズルを製作した。 [Sample Nos. 101-106]
For comparison, samples using Cr 3 C 2 , VC, and Mo 2 C as raw materials and samples not using Cr 3 C 2 , VC, and Mo 2 C were prepared. Specifically, as a raw material, WC powder having an average particle size of 0.7 μm (containing no Cr or V), Co powder, Mo 2 C powder, VC powder, Cr 3 C 2 powder (all average particle size: 0.7 ˜1.5 μm) and carbon powder were prepared. Adjust the addition amount of these raw material powders as appropriate, and go through the steps of mixing and crushing → granulation → drying → hydrostatic pressure → production of round bar → sintering → HIP in the same way as sample Nos. 1-5 A cemented carbide was obtained. In sample Nos. 101 to 106, mixing and pulverization were performed at high speed (over 25 rpm) over the entire mixing and pulverization time, and the sintering conditions and HIP conditions were the same as in sample Nos. 1 to 5 did. The obtained cemented carbide was processed in the same manner as Sample Nos. 1 to 5, and a nozzle for high-pressure water flow processing was manufactured.

[組成及び組織]
得られた各超硬合金について、ICP(inductively-coupled plasma)分光分析及びX線回折を行い、組成及び組織を調べた。その結果を表1に示す。全ての試料のCoの含有量、試料No.1〜5におけるCr及びVの含有量、及び試料No.101〜106におけるCr,V,Moの含有量は、超硬合金に対する質量割合である。X線回折により、WC,W2C,及びCoxWyCzのピーク波形のみが得られ、かつCr炭化物、V炭化物のピーク波形が検出限界により得られない場合、Cr,VはWC,W2C,CoxWyCz中に固溶した状態で存在すると判断する。また、X線回折により、WCのピーク波形が得られ、かつW2Cのピーク波形が検出限界により得られない場合、WとCとの二元化合物は全てWCとして存在すると判断する。更に、X線回折により、CoxWyCzのピーク波形(Crなどの固溶により純粋なCoxWyCzのピーク波形から若干ずれたピーク波形である場合を含む)が得られ、かつ金属Coのピーク波形が検出限界により得られない場合、CoはCoxWyCzとして存在すると判断する。なお、超硬合金の組成の分析は、上記ICP分光分析の他、Co滴定などを利用することができる。また、配合原料の組成は、超硬合金の組成に実質的に等しい。 [Composition and structure]
Each cemented carbide obtained was subjected to ICP (inductively-coupled plasma) spectroscopic analysis and X-ray diffraction to examine the composition and structure. The results are shown in Table 1. The Co content of all the samples, the Cr and V contents in the sample Nos. 1 to 5, and the Cr, V, and Mo contents in the sample Nos. 101 to 106 are mass ratios relative to the cemented carbide. When only the peak waveforms of WC, W 2 C, and CoxWyCz are obtained by X-ray diffraction, and the peak waveforms of Cr carbide and V carbide are not obtained due to the detection limit, Cr and V are WC, W 2 C, CoxWyCz Judged to exist as a solid solution. Further, when the peak waveform of WC is obtained by X-ray diffraction and the peak waveform of W 2 C is not obtained due to the detection limit, it is determined that all binary compounds of W and C exist as WC. Furthermore, the peak waveform of CoxWyCz is obtained by X-ray diffraction (including the case where the peak waveform is slightly deviated from the peak waveform of pure CoxWyCz due to solid solution of Cr, etc.), and the peak waveform of metal Co depends on the detection limit. If not obtained, it is determined that Co exists as CoxWyCz. The analysis of the composition of the cemented carbide can utilize Co titration in addition to the above ICP spectroscopic analysis. Moreover, the composition of the compounding raw material is substantially equal to the composition of the cemented carbide.

原料にCrやVを含有するWC粉末を用いて作製した試料No.1〜5では、表1に示すように試料No.4を除き、超硬合金中にCr炭化物やV炭化物がX線回折により検出されず、存在していないと言える。試料No.4も、Cr3C2が若干検出されたに過ぎない。試料No.4において、Cr3C2が若干検出された理由の一つとして、Crに加えてVを含有することで、結合相などに固溶しきれずに析出されたためであると考えられる。一方、原料にCr3C2粉末などの炭化物粉末を用いて作製した試料No.102〜104,106は、Cr炭化物(Cr3C2)、V炭化物(VC)、Mo炭化物(Mo2C)が検出され、炭化物が存在すると言える。従って、原料にCrやVを含有したWC粉末を利用することで、超硬合金中にCrなどが炭化物の状態で存在しないようにすることができると言える。なお、試料No.1〜3,5のCr、試料No.4の大部分のCr及びVは、CoxWyCz中やWC中に固溶していると考えられる。試料No.1〜5においてCoxWyCzのx,y,zの値は、超硬合金中の炭素の含有量が異なることで変化した。 In sample Nos. 1 to 5 prepared using WC powder containing Cr and V as raw materials, Cr carbide and V carbide are X-ray diffracted in the cemented carbide except sample No. 4 as shown in Table 1. It can be said that it is not detected and does not exist. In sample No. 4, Cr 3 C 2 was only slightly detected. One of the reasons why Cr 3 C 2 was slightly detected in Sample No. 4 is considered to be that it was precipitated without being completely dissolved in the binder phase or the like by containing V in addition to Cr. On the other hand, sample Nos. 102 to 104,106 produced using carbide powder such as Cr 3 C 2 powder as raw materials were detected as Cr carbide (Cr 3 C 2 ), V carbide (VC), and Mo carbide (Mo 2 C). It can be said that carbide exists. Therefore, it can be said that by using WC powder containing Cr or V as a raw material, Cr or the like can be prevented from being present in the carbide state in the cemented carbide. In addition, it is considered that Cr of sample Nos. 1 to 3 and 5 and most of Cr and V of sample No. 4 are dissolved in CoxWyCz or WC. In sample Nos. 1 to 5, the values of x, y, and z of CoxWyCz changed due to different carbon contents in the cemented carbide.

また、試料No.1〜5はいずれも、金属CoがX線回折により検出されなかったことから、試料No.1〜5の超硬合金中のCo成分は、CoxWyCzの状態で存在していると言える。更に、試料No.1〜4はいずれもW2CがX線回折により検出されず、X線回折の検出限界を考えると、体積割合でW2C/(WC+W2C)≦0.005であると考えられる。試料No.5は、配合時のカーボン粉末の添加量を試料No.3よりも少なく設定したことで超硬合金中の炭素量が低い合金となったため、W2Cが若干検出されたが、W2C/(WC+W2C)が0.01以下であると考えられる。 Further, in all of the sample Nos. 1 to 5, since the metal Co was not detected by X-ray diffraction, the Co component in the cemented carbide of the sample Nos. 1 to 5 exists in the state of CoxWyCz. It can be said. Furthermore, in all of sample Nos. 1 to 4, W 2 C was not detected by X-ray diffraction, and considering the detection limit of X-ray diffraction, the volume ratio was W 2 C / (WC + W 2 C) ≦ 0.005. It is believed that there is. Sample No.5, since the carbon content in the cemented carbide by an amount of carbon powder in formulation set smaller than that of the sample No.3 was a low alloy, but W 2 C is detected slightly W 2 C / (WC + W 2 C) is considered to be 0.01 or less.

[WCの粒度]
得られた各超硬合金について、組織観察を行い、WCの平均粒度、粒度の標準偏差σ、粒度(粒径)が1.0μm以上であるWCの面積割合を求めた。その結果を表2に示す。組織観察は、以下のように行った。各超硬合金を任意に切断して断面をとり、この断面を研削した後、#3000までのバフ研磨を施した。研磨した面を約5000倍の倍率で、FESEM(Field Emission Scanning Electron Microscope)によるEBSD(Electron Back-Scatter Diffraction)法を用いて観察した。観察は、研磨した面に対して任意の複数の視野(ここでは、1視野:180μm2で3視野)を選択して、視野ごとに行った。各視野中に存在する全てのWCの結晶粒について、結晶方位毎に色別(マッピング)を行い、結晶粒径を視覚的に把握できるようにした。得られたマッピング像に画像解析を行い、3つの視野に存在する全てのWCについてそれぞれ面積の円相当径を求め、この円相当径をWCの粒度(直径)とし、3つの視野に存在する全てのWCの粒度の平均を超硬合金の平均粒度とする。上記粒度の測定には、市販のEBSD装置を用いることができる。また、3つの視野に存在する全てのWCについて粒度の標準偏差を求め、この標準偏差を超硬合金の標準偏差σとする。更に、3つの視野に存在する全てのWCについて、粒度が1.0μm以上であるWCの合計面積S1.0WCを求め、3つの視野の合計面積Sfに対する面積割合R(％)=(S1.0WC/Sf)×100を求め、この割合Rを超硬合金におけるWCの面積割合Rとする。 [WC grain size]
The obtained cemented carbide was subjected to structure observation, and the average particle size of WC, the standard deviation σ of the particle size, and the area ratio of WC having a particle size (particle size) of 1.0 μm or more were determined. The results are shown in Table 2. Tissue observation was performed as follows. Each cemented carbide was arbitrarily cut to take a cross section, and after grinding this cross section, buffing up to # 3000 was performed. The polished surface was observed using an EBSD (Electron Back-Scatter Diffraction) method by FESEM (Field Emission Scanning Electron Microscope) at a magnification of about 5000 times. Observation was performed for each field by selecting an arbitrary plurality of fields (here, one field: three fields at 180 μm 2 ) on the polished surface. All WC crystal grains present in each field of view were color-coded (mapped) for each crystal orientation so that the crystal grain size could be grasped visually. Image analysis is performed on the obtained mapping image, and the equivalent circle diameter of each area is obtained for all WCs present in the three fields of view, and the equivalent circle diameter is defined as the WC grain size (diameter). The average particle size of WC is the average particle size of the cemented carbide. A commercially available EBSD apparatus can be used for the measurement of the particle size. Also, the standard deviation of the grain size is obtained for all WCs present in the three fields of view, and this standard deviation is defined as the standard deviation σ of the cemented carbide. Further, for all WCs present in the three visual fields, the total area S 1.0WC of WC having a particle size of 1.0 μm or more is obtained, and the area ratio R (%) = (S 1.0WC ) with respect to the total area S f of the three visual fields. / S f ) × 100, and this ratio R is defined as the area ratio R of WC in the cemented carbide.

作製した試料を代表して、試料No.2及び試料No.106について、EBSD法を用いて観察したマッピング像、及びWCの粒度分布を図1〜4に示す。図1は試料No.2のマッピング像、図2は、試料No.2の粒度分布、図3は、試料No.106のマッピング像、図4は、試料No.106の粒度分布である。図1,3では、グレースケールで示しているが、実際には、各WCにそれぞれ、赤〜青〜緑が施されている。図1,3において、白色から灰色の各塊はWCであり、図1において黒い塊はCoxWyCzであり、図3において黒い塊は金属Coである。   As representative of the prepared samples, FIGS. 1 to 4 show the mapping images observed using the EBSD method and the particle size distribution of WC for sample No. 2 and sample No. 106. 1 is a mapping image of sample No. 2, FIG. 2 is a particle size distribution of sample No. 2, FIG. 3 is a mapping image of sample No. 106, and FIG. 4 is a particle size distribution of sample No. 106. Although shown in gray scale in FIGS. 1 and 3, each WC is actually given red to blue to green. In FIGS. 1 and 3, each white to gray mass is WC, in FIG. 1, the black mass is CoxWyCz, and in FIG. 3, the black mass is metallic Co.

表2に示すように、試料No.1〜5はいずれも、WCが平均粒度:0.2〜0.7μmの範囲で微粒である上に、WCの粒度の標準偏差σが0.25以下であり、粒度のばらつきが小さく、均一的である。特に、試料No.1〜5はいずれも、1.0μm以上の粗大なWCが少ない。また、図1からも超硬合金中のWCはいずれも微細で均一的な大きさであることが分かる。更に、図1に示す超硬合金は、当該超硬合金中に微細なCoxWyCzが均一的に分散していることが分かる。   As shown in Table 2, in each of sample Nos. 1 to 5, WC is fine in the average particle size range of 0.2 to 0.7 μm, and the standard deviation σ of WC particle size is 0.25 or less. Variation is small and uniform. In particular, all of sample Nos. 1 to 5 have a small amount of coarse WC of 1.0 μm or more. Also from FIG. 1, it can be seen that the WC in the cemented carbide has a fine and uniform size. Furthermore, it can be seen that in the cemented carbide shown in FIG. 1, fine CoxWyCz is uniformly dispersed in the cemented carbide.

これに対して、図3に示すように試料No.106は、原料にCr3C2を利用していても、粗大なWCの粒子が局所的に存在している。このことは、図4のグラフからも裏付けられている。また、試料No.106は、図3に示すように局所的にCoが固まって存在し、超硬合金中のCoの厚さが不均一になっている。 On the other hand, as shown in FIG. 3, sample No. 106 has coarse WC particles locally even when Cr 3 C 2 is used as a raw material. This is supported by the graph in FIG. Further, in Sample No. 106, Co is locally solidified as shown in FIG. 3, and the thickness of Co in the cemented carbide is not uniform.

なお、試料No.105の組織観察を行ったところ、巣(ポア)が多く存在した。   When the structure of sample No. 105 was observed, there were many nests (pores).

[機械的特性]
得られた各超硬合金について、HRA硬度、破壊靭性(KIC)、抗折力を測定した。その結果を表2に示す。HRA硬度及び抗折力は、室温で市販の装置を用いて測定した。破壊靱性(KIC)は、ビッカース法に基づく測定が可能な市販の装置を用いて測定した。 [Mechanical properties]
About each obtained cemented carbide, HRA hardness, fracture toughness (KIC), and bending strength were measured. The results are shown in Table 2. HRA hardness and bending strength were measured using a commercially available apparatus at room temperature. Fracture toughness (KIC) was measured using a commercially available apparatus capable of measurement based on the Vickers method.

表2に示すように試料No.1〜5はいずれも、試料No.101〜106と比較して、硬度(HRA硬度)、靭性(破壊靭性)、強度(抗折力)をバランスよく具えている。特に、試料No.1〜3はいずれも、HRA硬度が94〜96と高硬度であり、破壊靱性が4MPa・m1/2以上と高靭性であり、抗折力が1GPa以上と高強度である。Cr3C2が若干検出された試料No.4は、試料No.1〜3と比較して靭性及び強度が若干小さくなったものの、WCが微細であり、比較的高硬度である。W2Cが若干検出された試料No.5は、試料No.1〜3と比較して硬度が若干小さくなったものの、比較的大きなWCが存在することで、高靭性及び高強度である。また、試料No.1,2は、試料No.3〜5と比較してCoが少ないことで、焼結中におけるWのCoへの溶解及びWCの再析出が抑制されたため、WCが微粒になり高硬度である。 As shown in Table 2, each of sample Nos. 1 to 5 has a better balance of hardness (HRA hardness), toughness (fracture toughness), and strength (bending strength) than sample Nos. 101 to 106. Yes. In particular, sample Nos. 1 to 3 all have a high hardness of 94-96 HRA, a high toughness of fracture toughness of 4 MPa · m 1/2 or higher, and a high bending strength of 1 GPa or higher. is there. Sample No. 4 in which Cr 3 C 2 was slightly detected had slightly smaller toughness and strength than Sample Nos. 1 to 3, but had a fine WC and a relatively high hardness. Sample No. 5 in which W 2 C was slightly detected has a slightly lower hardness than Samples No. 1 to 3, but has a relatively large WC, and thus has high toughness and high strength. Samples Nos. 1 and 2 have less Co than Samples Nos. 3 to 5, so that dissolution of W into Co and reprecipitation of WC during sintering were suppressed. High hardness.

一方、Cr3C2などを用いなかった試料No.101は、粒度が1.0μm以上の大きなWCが多く存在したことで、特に硬度が低い。超硬合金中にCr3C2が存在した試料No.102は、特に靭性及び強度が低い。試料No.103,104は、粒度が1.0μm以上の大きなWCが多く存在したものの、WCよりも高硬度なVCやMo2Cが存在したことで硬度が高い反面、靭性や強度が低い。試料No.105は、Coが少な過ぎることで焼結中のWのCoへの溶解やWCの再析出が抑制されてWCが微粒であるものの、合金全体としては靭性及び強度が低い。試料No.106は、Coが多過ぎることで、特に、硬度が低い。 On the other hand, Sample No. 101, which did not use Cr 3 C 2 or the like, has particularly low hardness due to the presence of large WC having a particle size of 1.0 μm or more. Sample No. 102 in which Cr 3 C 2 was present in the cemented carbide has particularly low toughness and strength. Samples Nos. 103 and 104, although many large WCs having a particle size of 1.0 μm or more exist, have high hardness due to the presence of VC and Mo 2 C, which are harder than WC, but have low toughness and strength. Sample No. 105 has low toughness and strength as a whole alloy although the amount of Co is too small, so that dissolution of W into Co during sintering and reprecipitation of WC are suppressed and WC is fine. Sample No. 106 has particularly low hardness due to too much Co.

更に、試料No.2の超硬合金について、室温(20℃)〜800℃までの温度域について、ビッカース硬度Hv(GPa)を測定した。その結果、室温では24.6GPaであり、600℃以上でも硬度の低下度合いが少なく、800℃でも15GPa程度を有していた。また、上記600℃以上の温度域に曝した超硬合金の表面を観察したところ、Coの溶出も見られず、表面性状に優れていた。このことから、試料No.1〜5の超硬合金は、高温域においても、高硬度を維持することができる上に表面性状が優れていることから、高温域で使用され、良好な仕上げ面品位が望まれる部材、例えば、ガラスレンズ用の金型の構成材料に好適に利用できると期待される。   Furthermore, Vickers hardness Hv (GPa) of the cemented carbide of sample No. 2 was measured in the temperature range from room temperature (20 ° C.) to 800 ° C. As a result, it was 24.6 GPa at room temperature, the degree of hardness decrease was small even at 600 ° C. or higher, and it was about 15 GPa even at 800 ° C. Further, when the surface of the cemented carbide exposed to the temperature range of 600 ° C. or higher was observed, no Co elution was observed and the surface properties were excellent. From this, the cemented carbides of Sample Nos. 1 to 5 can maintain high hardness even at high temperatures and have excellent surface properties. It is expected that the material can be suitably used as a constituent material of a member for which quality is desired, for example, a mold for a glass lens.

[ノズルの寿命]
作製したノズルを用いて、以下のようにして寿命を調べた。その結果を表2に示す。砥粒に#120のガーネットを用い、水圧:300MPaで鉄板を切断する。一定時間ごとにノズルの貫通孔の直径を測定し、摩耗による上記直径の変化を調べる。初期の貫通孔の直径φ0.5mmに対して0.1mm増加するまで、即ち、貫通孔の直径が0.6mmになるまで鉄板を切断し、直径φが0.6mmになった時点の時間を寿命として評価した。 [Nozzle life]
Using the prepared nozzle, the lifetime was examined as follows. The results are shown in Table 2. Use a # 120 garnet as the abrasive and cut the steel plate at a water pressure of 300 MPa. The diameter of the nozzle through-hole is measured at regular intervals, and the change in diameter due to wear is examined. The steel plate is cut until the initial diameter of the through hole is increased by 0.1 mm, that is, until the diameter of the through hole is 0.6 mm, and the time when the diameter becomes 0.6 mm is evaluated as the life. did.

表2に示すように、試料No.1〜5はいずれも、試料No.101〜106に比較して寿命が非常に長い。特に、Cr炭化物やW2Cが検出されなかった試料No.1〜3では、非常に長寿命である。一方、硬度が低い試料No.101,105,106は、耐摩耗性に劣っていた。金属炭化物が存在した試料No.102〜104では、寿命試験中に欠けが生じた。 As shown in Table 2, sample Nos. 1 to 5 all have a very long life compared to sample Nos. 101 to 106. In particular, Sample Nos. 1 to 3 in which Cr carbide and W 2 C were not detected have a very long life. On the other hand, Samples Nos. 101, 105, and 106 having low hardness were inferior in wear resistance. In sample Nos. 102 to 104 in which metal carbide was present, chipping occurred during the life test.

なお、上述した実施の形態は、本発明の要旨を逸脱することなく、適宜変更することが可能であり、上述した構成に限定されるものではない。例えば、超硬合金の組成や、原料粉末の平均粒径などを適宜変更することができる。   The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the composition of the cemented carbide, the average particle diameter of the raw material powder, and the like can be changed as appropriate.

本発明超硬合金は、耐摩耗性に優れることが望まれる各種の耐摩部品、例えば、高圧水流加工用ノズル、金型(パンチやダイ)などの構成材料に好適に利用することができる。また、本発明超硬合金は、表面性状に優れ、高品位な部材の形成が望まれるカメラなどのガラスレンズ用金型の構成材料に好適に利用することができる。   The cemented carbide of the present invention can be suitably used as a constituent material for various wear-resistant parts that are desired to be excellent in wear resistance, for example, a nozzle for high-pressure water flow processing, a die (punch or die), and the like. Further, the cemented carbide of the present invention can be suitably used as a constituent material of a glass lens mold for a camera or the like, which is excellent in surface properties and requires formation of a high-quality member.

Claims (6)

Coを0.2質量％以上0.9質量％以下、Crを0.2質量％以上1.5質量％以下含有し、残部がWとCとの二元化合物及び不純物からなり、
前記Coは、CoxWyCzの状態で存在しており、
前記WとCとの二元化合物のうち、WCの平均粒度が0.2μm以上0.7μm以下であり、
前記WCの粒度の標準偏差σがσ≦0.25であることを特徴とする超硬合金。 Co is contained in an amount of 0.2% by mass or more and 0.9% by mass or less, Cr is contained by 0.2% by mass or more and 1.5% by mass or less, and the balance is composed of a binary compound of W and C and impurities.
Co is present in the state of CoxWyCz,
Among the binary compounds of W and C, the average particle size of WC is 0.2 μm or more and 0.7 μm or less,
Cemented carbide characterized in that standard deviation σ of grain size of WC is σ ≦ 0.25. 粒度が1.0μm以上であるWCの面積割合が当該超硬合金に対して5％以下であることを特徴とする請求項1に記載の超硬合金。   2. The cemented carbide according to claim 1, wherein an area ratio of WC having a particle size of 1.0 μm or more is 5% or less with respect to the cemented carbide. 前記WとCとの二元化合物は、主としてWCであり、
W2Cを含む場合、体積割合で、W2C/(WC+W2C)≦0.005以下であることを特徴とする請求項1又は2に記載の超硬合金。 The binary compound of W and C is mainly WC,
3. The cemented carbide according to claim 1, wherein, when W 2 C is contained, the volume ratio is W 2 C / (WC + W 2 C) ≦ 0.005 or less. 前記超硬合金のHRA硬度が94以上96以下、破壊靱性(KIC)が4MPa・m1/2以上、抗折力が1GPa以上であることを特徴とする請求項1〜3のいずれか1項に記載の超硬合金。 The cemented carbide has an HRA hardness of 94 or more and 96 or less, a fracture toughness (KIC) of 4 MPa · m 1/2 or more, and a bending strength of 1 GPa or more. The cemented carbide described in 1. 更に、Vを0.2質量％以下含有することを特徴とする請求項1〜4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, further comprising 0.2 mass% or less of V. Cr炭化物及びV炭化物が、X線回折により検出されないことを特徴とする請求項1〜5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 Cr carbide and V carbide are not detected by X-ray diffraction.
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