低合金鋼の溶接割れに及ぼす予・後熱の効果に関する研究(第2報)

化学組成及び組織から見た予・後熱条件

抄録

The Application of supplementary heat to a weld joint befor or after welding have been studied using a mild steel, medium carbon steels, 50 to 100 kg/mm² high tensile steels, low alloy steels, martensitic stainless steels and cast steels.
The results indicate that (1) When preheating is applied for preventing cold cracking in heat-affected zone, a new carbon equivalent, i.e. Pre. Ceq.=C+0.06Mn+0.03Ni+0.06Cr+0.10Mo, is useful in predicting the cracking susceptibility of a wide variety of steels above-mentioned, (2) the critical preheat and interpass temperatures are reduced by using postheating, (3) these temperatures must be held till postheating at the temperatures above the critical point (T_2c) at which hydrogen-induced cracking can not occur, (4) the T_2c depends on the chemistry of steel, and the T_2c values may be given by T_2c(°C)=455 Post Ceq. -110, Post Ceq.=C-0.08Si+0.20Mn+0.03Ni+0.05Cr+0.12Mo+0.84V, and (5) it is desirable for avoiding hot cracking that the preheat and interpass temperatures are lower than Ms point.