PREVENTION OF ARC WANDERING IN TIG TREATMENT

摘要

PURPOSE:To eliminate the generation of a crack in the outside circumferential edge part of a recessed spherical surface to be subjected to a TIG treatment by blowing side gas to the part near said edge part and an electrode thereby preventing the arc wandering to be caused by the high frequency during arc generation. CONSTITUTION:The electrode 9 of a TIG torch 8 is directed to the recessed spherical surface 5 of an arm 1 and shielding gas 11 is fed thereto from a nozzle 10 to generate an arc. An arm 1 is rotated around the axial center of the surface 5 to form a bead 12. A side nozzle 16 is directed, with the surface 5 backward, to the part near an outside circumferential edge part 13 and the electrode 9, and the same side gas 17 as the gas 11 is ejected in about 2-3sec before the impression of the high frequency during the arc generation. The gas is stopped in about 0.5sec after striking. The impact of the ion generated in the above-mentioned proximity part and the release of thermion are thus obviated and the generation of arc wandering in the part 13 is prevented. The crack likely to be generated in the outside circumferential edge part 13 in the stage of a hot coining treatment is thus eliminated.