PURPOSE: To economically, efficiently and uniformly perform welding by electrifying and heating a seam welding part of high tension sheet steels in advance to soften it and subsequently, performing mash seam welding with a specific current value.
CONSTITUTION: In the mash seam welding of the sheet steels having ≥80kg f/mm2 tensile strength, the preceding and succeeding sheet steels 3 and 4 of sheet coils are superposed on each other with a prescribed lap allowance 10 at a lap part 7 via clamps 5 and 6. Said lap part 7 is pressed between upper side and lower side copper electrodes 1 and 2 rolling in the sheet cross direction. A current of 0.2I0-0.8I0 is then applied to the seam welding part of the lap part 7 with respect to a nugget forming minimum current value I0 via both electrodes 1 and 2 in advance to heat and soften the welding part. Afterward, the mash seam welding is performed with the current value of I0-1.6I0 with respect to the current value I0 and the current is applied continuously.
YASUDA KOICHI
NAKANO SHOZABURO
UCHIDA YASUTAKA
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