中，高炭素低合金鋼の溶接熱影響部における低温割れの研究 ＩＩ 焼割れ的低温割れ感受性の評価のための再現熱サイクル低温割れ試験の適用性について

Abstract

Thermal and mechanical testing approach is applied to evaluating the susceptibility to cold cracking of quenching crack type in welds of medium/high carbon low alloy steels. The simulation test was done with notched specimen during cooling of simulated weld thermal cycle by means of high frequency induction heating.The test shows the availability to get the correlation between temperature and fracture stress by applying tensile deformation from just above Ms temperature under different cross-head speeds corresponding to contraction rate in actual welding. The measured fracture stress decreases with increasing peak temperature, and that measured under the condition of peak temperature resulting in grain boundary liquation is nearly the same as that in the RRC test which was discussed in the previous paper. Grain boundary liquation promotes intergranular fracture. Moreover, intergranular facets with definite grain boundary liquation are more brittle, and are more similar to that in the RRC test than that without grain boundary liquation. Therefore, crack susceptibility of these materials can be evaluated with the simulation test using the specimen heated up to the liquating temperature of grain boundary.