介在物を低減させた熱間工具鋼の疲労強度特性

抄録

In this study, it was investigated the fatigue strength characteristic of the hot work die steels. Test material was used the newly development hot work die steel which improved JIS SKD61. “N” sample which improved SKD61, “A” sample to which the production technique of “N” sample was changed and “B” sample which were reduce oxide and a carbide of “N” sample were used. As a result of static bending tests, the “A”, “B” and “N” showed the same strength. Result of four-point bending fatigue tests, fatigue strength of “A” and “B” samples in the low cycle region showed the same value as “N” sample. However fatigue strength of “B” sample in the high cycle region was higher than “A” and “N” samples. As a result of fracture surface observation, the fracture origin was aluminum or oxygen inclusion mainly. As a result of EBSD analysis, the size of the mass having the same crystal orientation in the “B” sample was smaller than that of “N” and ”A” samples.