732 焼戻しマルテンサイト鋼のナノーメゾーマクロ多階層強度解析

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*_<dis>+Hv*_<pre>+Hv*_<blo>, where Hv is macro-Vickers hardness, and Hv*_<dis>, Hv*_<pre> and Hv_<blo> are micro-covered Vickers hardness due to dislocation and solid, precipitation and block boundary strengthening. Hv*_<pre> and Hv_<blo> 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. [numerical formula] [numerical formula]
一般社団法人日本機械学会の論文
2002-10-10