Oliff PLC
Method of resistance spot welding of high tensile strength steel sheet and welding joint manufactured by the method
Provided is a method of resistance spot welding of welding a sheet set including a high strength steel sheet with which a high joint strength can be achieved even for a high Ceq material. A method of resistance spot welding a sheet set of two or more lapped steel sheets by weld the sheet set while clamping and pressing the sheet set between a pair of welding electrodes includes a first welding step of applying an weld current Im (kA) and forming a nugget having a nugget diameter d (mm) that satisfies the following inequality (1); a cooling step, subsequent to the foregoing first welding, of cooling the sheet set while continuing to press the sheet set; and a second welding step of performing two-step welding,3×√tm≦d≦6×√tm  (1),where tm is the thickness (mm) of the thinnest one of the foregoing two or more steel sheets.
JFE STEEL CORPORATION
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B23K B23K B23K B23K
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Koichi Rinsei Yasuaki
Taniguchi Ikeda Okita