Prevention of End Cracking in One Side Automatic Welding (1st Report)

Abstract

The application of one side automatic welding has contributed to promotion of conveyor process for assembly stage of ship construction.In this process of one side automatic welding, however, it is observed that cracking appears in the center of weld metal mainly near the end of weld joints. To prevent this cracking, many experiments and investigations have been done from the viewpoint of dynamics and metallurgy and many useful methods have been developed and put into practice.Preventing method adopted in actual assembly stage is to restrain the opening displacement of the groove at end of weld joints by sealing bead. In this method, backing bead at end of weld joints is not always complete and has to be repaired.The authors confirmed formerly that end cracking in one side automatic welding occurred in relation between displacement and its rate at end of weld joints. In this paper, it is discussed on the improvement of deformation capacity of weld metal by changing of welding conditions on the basis of their fundamental experiments and it is clarified that the control of displacement and its rate at end of weld joints by means of special device gives vital effect on prevention of this end cracking.This preventing method was applied to actual weld joints in assembly stage. It was confirmed that this method was very useful.