Teruhiko Hinata

Penetration shape and welding of real joints by a traveling TIG arc (2nd report): Study of low‐speed DC TIG welding

Summary This paper describes an investigation of the penetration shape and welding of real SUS304 joints by travelling TIG arc welding. A weld bead with a large penetration ratio (penetration depth/bead width) can be obtained by low‐speed welding. Since the anode spot is fixed at the centre of the weldpool in He‐DC TIG, deep penetration with a narrow bead width is effectively obtained. The transition current giving a top bead width with the minimum value combined with full penetration bead formation increases in Ar‐DC TIG welding with an increasing base metal thickness. The step movement welding method, whereby a stationary arc is struck after short‐distance travel, is effective to obtain a stable penetration bead at a plate thickness above 6 mm. The stability of penetration bead formation is improved when flux‐cored wire is added.

Penetration form of DC TIG arc welding using flux‐cored wire filler. Study of low‐speed DC TIG welding (3rd Report)

Summary Previous reports have shown that the penetration ratio (penetration depth/bead width = D/W) during DC TIG arc welding of SUS304 stainless steel can be improved by using flux‐cored stainless steel wire for CO2 gas welding. The present paper further examines the effect of flux‐cored wire on penetration, considering the mechanism of penetration forming with regard to changes in arc phenomena. The paper shows that a shrunken anode is formed just under the electrode when flux‐cored wire is used. High D/W welds are then obtained without any penetration effect being caused by small quantities of elements in the base metal. The notion of the high D/W being mainly due to electromagnetic convection generated by electric current concentrating in the shrunken anode is also clarified by the experimental approach. For stable welding with high D/W penetration, the paper proposes a method of intermittent supply of flux cored wire just before step‐movement welding starts.