The welding wire is made Daido steel WSR35K. Moreover, the seed gas in that case is made argon 94〜98% and oxygen 2〜6%. Moreover, correspond as follows as the item outside the instruction sheet description content. The sensitization in the weld must correspond as follows as the technical order. ・The sensitization in the weld is clause 10 of technological book No.01204-00090;Evaluate, and judge by the sensitization in the weld. ・The oil related to the welding defect must not adhere to the welding front goods.