焼戻しマルテンサイト鋼のナノ領域強度解析

概要

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The relationships between tensile strength and microstructural parameters and between fatigue limit and microstructural parameters were investigated for seven tempered-martensitic steels S45C, SMn443, SCr440, SNCM439, SCM440, SUP7 and SUP12. An optical and atomic force microscopy showed that prior-austenitic grain diameter, d_γ, block width, W_blo, and precipitation spacing, λ, were 18μm, 0.7μm and 0.11〜0.24μm, respectively, as microstructural parameters. A nanoindentation showed that HV=100+Hv^*_dls+Hv^*_pre+Hv^*_bou, where Hv is macro-Vickers hardness, and Hv^*_pre and Hv^*_bou are micro-covered Vickers hardness due to dislocation and solid, precipitation and block boundary strengthening. Hv^*_pre and Hv^*_bou were expressed by the microstructural parameters of λ and W_blo. The constant value of 100 is base hardness of the iron. Based on these results, we proposed that tensile strength σ_B and fatigue limit σ_w, were expressed in the followings. σ_B=3.27{100 + Hv^*_dls + 1.02 × 10^-2λ^-1 + 3.67 × 10^-4λ^-1w^-1/2_blo}…………………………………(A-1) σ_w=1 .6{100 + Hv^*_dls + 1.02 × 10^-2λ^-1 + 1.15(3.67 × 10^-4λ^-1w^-1/2_blo)}…………………………(A-2)
一般社団法人日本機械学会の論文
2002-10-25