622 高強度鋼のギガサイクル疲労特性 : その 2 : 介在物と組織割れ起点内部破壊

概要

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Fatigue tests were carried out for two spring steels (heat A and D1) and one valve spring steel (heat F) with Vickers hardness HV=518∿528. Heat A, F and D1 were produced in 1986,1997 and 1998. The sizes and compositions of inclusions were controlled in heat F and D1. The internal fracture occurred for all three steel. The fatigue strength σ_w=640,and 720 MPa at (10)^8 cycles for heat A, D1 and F was lower than the estimated on. σ_w=874 MPa from the empirical equation σ_w=1.6HV for the surface fracture. The Al_2O_3 inclusion, and TiN inclusion and matrix crack were observed at the internal crack initiation sites for heat A and F, whereas only the matrix crack was observed for heat D1 where the inclusions were controlled. These results suggest that the fatigue strength σ_w could be improved for heat D1,if the matrix crack is prevented.
社団法人日本機械学会の論文
2000-07-31