Examination of melting characteristics of pure titanium and welding procedure conditions. Welding of pure titanium, and joint performance (Report 1)

摘要

The melting characteristics and the welding procedure conditions for pure titanium using the TIG welding process were investigated and the following features identified:For pure titanium there is a tendency for the melting of the plate surface to progress rather than deep penetration and the melting characteristics were demonstrated with a poor penetration efficiency.One side welding of approximately 1 mm thick plate, for which thickness penetration formation has little relevance, was feasible under conditions very similar to those for he welding of SUS304 material.The risk of developing undercut in high speed welding is low compared with SUS304 material. However, the risk of developing cracks from the undercuts is high; thus, in order to prevent undercut occurrence it is necessary to establish welding procedures which prevent undercut by the use of a drag angle knife edge electrode.For one side welding of approximately 3 mm plate thickness, reverse bead welding is feasible in a stable manner by the formation of a large keyhole by means of a joint with a root gap. When He is employed as a torch shielding gas, one side welding with a narrow surface fusion width is feasible using an I-type joint with approximately 2 mm root gap. Under the circumstances, it is effective to employ a mixed gas containing approximately 20 percent Ar in He to maintain the improvement of penetration and inhibit weld zone periphery oxidation.