鋼の再熱割れに関する基礎的研究(第 1 報) : 切欠底部の塑性変形能におよぼす冶金学的因子の影響

概要

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It is reported that reheat crackings in steels initiate at stress concentrated regions like a toe of weld. If materials have excellent deformabilities at such stress concentrated regions, no reheat crackings occur. Consequently, the deformability at the stress concentrated region can be used as one of parameters to estimate the reheat cracking susceptibilities of materials. In this study, critical crack opening displacement at the tip of notch (Φ_c) obtained by elevated temperature tensile test was used as a parameter to evaluate the deformability of a material at stress concentrated region. In this report, the effects of peak temperature and cooling time from 800℃ to 500℃ of weld thermal cycle on Φ_c were investigated. The experimental results obtained in this study are as follows; 1) φ_c of HT 80 steel at 600℃ increases with decreasing of the hardness of matrix. 2) Φ_c of HT 80 steel at 600℃ decreases with increasing of the prior austenitic grain size. 3) In HT 60 steel, the deformability at the stress concentrated region at 600℃ is improved by the formation of polygonal ferrites at grain boundaries. These polygonal ferrites are formed when cooling time from 800℃ to 500℃ becomes longer than 10sec.
社団法人溶接学会の論文
1978-03-05