冷間鍛造金型用超硬合金の破壊じん性

抄録

The fracture toughness of cemented carbide for cold forging dies is necessary for predicting the fracture of a die insert. It is generally measured by the hardness indentation method. In the present study, it was measured by the three-point bending test using a test piece with a precrack generated by the EC method. Seven types of cemented carbide were used. It was found that the fracture toughness increases with an increase in WC grain size or Co mass percent. It was also found that the bending test using a test piece with a precrack gives good results compared with the hardness indentation method. It was shown that cemented carbides could be destroyed macroscopically under a 160 MPa tensile stress as analyzed by FEM simulation using a test piece model without a precrack.