凝固過程および凝固後における高クロム鋼の高温変形挙動

概要

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Phase dependence of tensile strength of chromium steel during and after solidification has been studied by a technique for high temperature tensile test. The experimental technique enabled a sample to melt and solidity without crucible, and we can measure a minute load in a solidification temperature range by the experimental technique. A numerical model for the analysis of phase transformation during and after solidification was developed with an assumption of local equilibrium at liquid/solid interface or δ/γ phase interface. The zero strength temperature was in agreement with zero ductility temperature, and both of them appeared at the solid fraction of about 0.8. The tensile strength of chromium steel was dependent on the phase state but not chromium contents. Equations for prediction of tensile strength of δ and γ phases were determined using the experimental results in combination with the previous results for carbon steel and stainless steel. σ_δ=0.014(T_<δ, strat>-T)+1.2, MPa σ_γ=0.067(T_<γ, strat>-T)+6.7, MPa Tensile strength of δ phase state is smaller than that of γ phase, and temperature dependence of tensile strength of δ phase is also smaller than that of γ phase. The tensile strength of δ and γ coexisting phase is predicted from the following equation. σ_<(δ+γ)>=σ_δ・f_δ+σ_γ・f_γ These estimated values are in good agreement with experimental results.
社団法人日本鉄鋼協会の論文