抄録
Hot cracking is a phenomenon that occurs when the tensile strain acting on the liquid film is large within the Brittleness Temperature Range (hereinafter referred to as BTR), where solid and liquid coexist in the weld zone. Since the liquid phase has less strength than the solid phase, strain tends to be concentrated in the liquid phase. Therefore, in addition to considering the strength difference between the solid and liquid phases in the analysis, it is important to visualize the direction of crystal growth and the meeting angle to evaluate hot cracking. In addition, solidification shrinkage strain occurs during solidification of molten metal due to the density difference between the solid and liquid phases, and the effect of this strain cannot be ignored.
Therefore, the authors have developed a weld hot cracking analysis method that can consider metallurgical factors such as solidification shrinkage strain and crystal growth direction, as well as mechanical factors such as strain, deformation and stress. In this study, the proposed method is applied to butt welds to investigate the effects of various factors on the high temperature strain. The effects of the bevel angle on the solidification morphology and the high-temperature strain of the weld zone were examined, and it was shown that hot cracking is more likely to occur in narrow bevel welds with small bevel angles. Furthermore, the effect of the relationship between temperature and solid fraction on the high-temperature strain of the weld zone during cooling was examined, and it was confirmed that the plastic strain increment in BTR was larger where the variation of solid fraction with temperature was large, and that the plastic strain increment in BTR was smaller where the variation of solidus ratio with temperature was small.
