抄録
Hot cracking is one of the most serious welding defects that can significantly reduce the strength of structures, and it is important to prevent hot cracking. In the Japanese shipbuilding industry, one-sided submerged arc welding with multiple electrodes is used to improve the production efficiency of welding large steel plate joints for ships, and it has been reported that hot cracking may occur at the termination. From the viewpoint of the mechanism of hot cracking, if tensile strain does not act within the Brittleness Temperature Range (BTR), the possibility of cracking is negligible. In other words, any hot cracking problem can be solved if compressive strain can be applied within the BTR during welding.
In this study, a new “parallel heating method” is proposed to prevent hot cracking by using the thermal expansion caused by simultaneous additional heating to the welding torch. In the analysis of bead-on-plate welding, the effect of the parallel heating method in reducing high-temperature strain and its appropriate conditions were investigated. It was confirmed that the proposed method reduced high-temperature strain not only at the steady state but also at the beginning and end of the weld. It was also confirmed that the effect of reducing high-temperature strain varies depending on the position of the additional torch, and that there is an appropriate heating position depending on the target weld. In the analysis of multi electrode single side submerged arc welding, it was confirmed that the proposed method has little effect on the weld penetration shape, and it was shown that the proposed method can ensure weldability. It was also confirmed that the proposed method has a significant reduction effect on high-temperature strain generated by localized opening deformation, demonstrating the usefulness of the proposed method.
