鋼の低温域における硬さと引張応力および衝撃値との対応性

抄録

Up to the present, there are many investigations on the temperature dependences of mechanical properties of steels at low temperatures. However, the temperature dependences have been divided into three or four regions by merely thinking of the deformation mechanisms which depend on wavy slip or twinning. As a result, there are unsolved problems such as considerations of the differences in expressive equation and in strain rate and the application of dislocation theory.
In this study, the correlativity between temperature dependences on Vickers hardness, the tensile properties and the impact energy for several kinds of commercial steels was examined, and some considerations were given to the deformation mechanism in each region.
\ oindentThe results obtained are as follows:
(1) σ_0.2% vs T^1⁄2 curve and V^* vs T^1⁄2 curve consist of three straight lines whose gradients change at the temperatures _TT₀, _TT₁ and T_V^*0, T_V^*1. Each region of the three straight lines are named Regions I, II and III, respectively. Region I corresponds to the athermal deformation field, Region II to the cross slip field, and Region III to the Peierls deformation field.
(2) While, both Hv vs T^1⁄2 curve and logHv vs 1⁄T curve have four straight lines, i.e., Regions, I, II, III and IV. Region IV is considered to correspond to the twinning deformation field.
(3) The correspondence between the mutation temperatures _HT₀ and _HT₁ in the logHv vs 1⁄T curve and _VT₁ and _VT₂ in the logE vs 1⁄T curve is very good for the case of 1⁄_HT₀ vs 1⁄_VT₁ and 1⁄_HT₁ vs 1⁄_VT₂ and the correspondence between the transition temperature _VT_rE or _VT_rS in the impact test and _HT₀ or _HT₁ is better at 1⁄_VT_rE or 1⁄_VT_rS vs 1⁄_HT₁.