| 摘要 |
PCT No. PCT/JP98/01344 Sec. 371 Date Nov. 3, 1999 Sec. 102(e) Date Nov. 3, 1999 PCT Filed Mar. 26, 1998 PCT Pub. No. WO98/43773 PCT Pub. Date Aug. 10, 1998The weld seam tracking and the welding torch height are controlled, the waveform of the welding voltage or the welding current of the arc is detected, the waveform of the above-described welding voltage or welding current under an appropriate welding condition to a reference gap Gref is stored as a reference waveform, the area | DELTA SG| of a deviation part of the detected waveform to the above-described reference waveform is obtained, DELTA SG is obtained by judging the positive and negative of | DELTA SG|, the relationship between the value of DELTA SG and the root gap G is experimentally determined in advance, and the root gap G is calculated from the value of DELTA SG.
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