| 摘要 |
PROBLEM TO BE SOLVED: To provide a stable technique capable of producing a highly reliable joint having high fatigue strength and suitable for real operation in spot welding for high strength steel sheets. SOLUTION: In the plasma spot welding method for steel sheets, steel sheets each having a yield stress of≥270 MPa and also having a sheet thickness of 1.0 to 3.6 mm are superimposed to form a through hole in a joint from one side by plasma, and thereafter, a weld metal in which the volume fraction of martensite is≥50%, and also, the average nominal diameter D of the equivalent circle in the superimposed faces of the steel sheets is≥3.5√t1mm to the steel sheet thickness t1 on the thin side is formed inside the through hole. COPYRIGHT: (C)2006,JPO&NCIPI
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