| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high performance cemented carbide having high hardness and furthermore high in fracture toughness, in the case the saturation magnetism theoretical ratio in cemented carbide contg. WC with the specified average grain size as the hard phase is specified value, by regulating its coercive force to specified value. SOLUTION: The average grain size of the hard phase is regulated to 0.1 to 1.0μm, preferably to 0.1 to 0.4μm. The saturation magnetism theoretical ratio of the cemented carbide is regulated to 0.75 to 0.90, preferably to 0.8 to 0.9. Its coercive force Hc at this time is regulated to 200 to 340 Oe, preferably to 270 to 340 Oe. It is preferable that its hardness is regulated to 1,600 to 2,300 kg/mm<2> , its fracture toughness is regulated to 5 to 15 MPam<1/2> , Cr and the carbides of Cr are contained by <=3.0%, and V and the carbides of V are contained by <=0.1 wt.%. Cr and the carbides of Cr are preferably subjected to compounding treatment at the time of producing raw material WC powder. Raw material mixed powder 1 is set to the space between an upper pressure ram 4 and a lower pressure ram 5 via a graphite die 3 and is electrically sintered at 1,050 to 1,300 deg.C under 150 to 500 kg/cm<2> for 1 to 20 min. It is optimum as the material of a precision die.
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