Ｃｒ‐Ｍｏ鋼の再熱割れに関する研究 第８報 １Ｃｒ‐１／２Ｍｏ銅の再熱割れにおよぼすいおうとマンガンの複合作用

Abstract

The relation between parameter of the concentration of dissolved sulfur, and reheat cracking sensitivity was examined on 1%Cr-0.5%Mo steel by following experiment and metallurgical considerations. (1) The reheat cracking sensitivity of each steel specimen was compared by critical restraint stress to produce cracking, σAW-crit obtained by modified implant test. Seventeen steels were used for test; they contained 0.015 to 0.09%S and 0.1 to 1.3%Mn. (2) The sulfide was extracted by electrolysis, and (S) was calculated by reducing weight of sulfur in extracted sulfide from that in bulk steel. (3) The critical restraint stress, σAW-crit was plotted against (S); there is a critical value of (S), (S) crit, from which σAW-crit begins to decrease with increasing (S) value. (4) A nomograph was proposed to estimate content of dissolved sulfur by sulfur and manganese contents in steel. This informs that manganese reduces (S) remarkably when manganese exceeds critical value. (5) Sulfide will render much smaller effect on reheat cracking than dissolved sulfur did.