再熱割れにおよぼすV及びTiの影響

Cr-Mo鋼の再熱割れに関する研究(第4報)

抄録

Influences of V and Ti on the reheat cracking sensitivity of Cr-Mo steels were investigated using 13 synthetic 0.06%V-bearing and 9 synthetic 0.07%Ti-bearing Cr-Mo steels, which contained 0 to 2%Cr and 0.25 to 0.8% Mo. Cracking sensitivity was evaluated in term of the critical restraint stress; σAW-crit obtained by the implnat type reheat cracking test. The results are summarized as follows. (1) 0.06%V addition increases the cracking sensitivity especially in the content region of low Mo. (2) 0.07%Ti addition increases the cracking sensitivity especially in the content region of low Cr and high Mo. (3) Two important factors which dominate the critical rsetraint stress are the stress relaxation; R and the grain boundary strength at the time of crack initiation; σpw-crit. V and Ti remarkably decrease R but they hardly decrease σpw-crit. (4) The decrease of the stress relaxation was mainly associated with the strengthening of matrix which was brought by the precipitation of V₄C₃ and TiC during reheating.