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