Examination of Melting Characteristics of Pure Titanium and Welding Procedure Conditions
Nobuyuki FUJII, Yoshimasa FUKUHARA, Teruhiko HINATA, Katsuhiko YASUDA
Recently, the production of products using pure titanium has increased in Japan, and the welding for the pure titanium has attracted the attention. Concerning the welding of titanium, there are many research reports on the oxidation of weld zone in the welding process. However, the research report on practical welding procedure is scarce. In this study, weld property, which arose when the pure titanium was welded by TIG, was examined. As a result, the following was clarified: (1) The melting of the surface is easy to advance further than the penetration to the depth direction. And the weld zone of the shallow penetration is productive. (2) The undercut is hard to generate in the high-speed welding in comparison with a stainless steel 304. But, if there is an undercut, the crack is productive even in the shallow undercut. Therefore, it is proposed that the following countermeasures will be effective for the welding procedure: (1) The plate thickness of the root part should be made at about 1 mm because of the sufficient penetration. (2) Helium-argon mixed gas, in which argon is included at about 20%, should be used as a shielding gas. (3) The joint should have the root gap and be welded using the filler rod. And the knife-edge electrode should be used too.