鋼溶接部の再熱割れに関する冶金学的研究(第4報)

再熱割れ感受性におよぼす不純物元素の影響と再熱割れ機構に関する考察

抄録

Effect of the impurity elements P, S, Sb, As, Sn on the sensitivity of steel to reheat cracking have been studied at the stress relaxation test. Furthermore, in the sample after reheat treatment, the segregation of impurity elements have been investigated at the Auger electron spectrometer.
The results of the study obtained are summarized as follows:
1) The increase of impurity elements P, S, Sb, As, Sn in steel was decreased extremely the plastic deformability Δlp', as measured at the time of occurrence of cracking, and was increased very the sensitivity to cracking.
2) It has become apparent that the remarkable segregation to grain boundary of impurity elements P, S, Sb in steel occur in the range of temperature at the occurrence of reheat cracking.
3) The mechanism of reheat cracking can be considered as follows:
Toe of weld that occur the reheat cracking remain high tensile stress in order to stress concentration, and segregation to grain boundary of impurity elements P, S, Sb in steel is accelerated by its tensile stress, and as a result, grain boundary well be embrittlement. Farthermore, the plastic deformation in toe of weld has little in order to remain hardened structure and coarse grain. Consequently, it is considered that reheat cracking caused by the embritllement in grain boundary, hardened structure and coarse grain.