| 摘要 |
PROBLEM TO BE SOLVED: To provide a butt welding method by which penetration beads are stably formed without using a special welding method and an advanced welding condition control method, a thick member can be welded by one run and the welding can be performed at high speed and with high efficiency. SOLUTION: The tip part of a preceding welding torch i0 is bent almost in parallel with the plate surface of a member 6 to be welded, the tip part of a succeeding welding torch 20 is made to incline and a shielded gas nozzle 23 is mounted at the tip part of the succeeding welding torch 20. A lower backing 9 preventing melted metal from dropping is installed on the lower surface of the groove of the member 6 to be welded and an upper backing 14 having the exhaust port 16 of shielded gas is installed on the upper surface of the groove so that they slide according to the progress of the welding. After inserting the tip part of the preceding welding torch 10 into the inside of a groove 7 surrounded by the lower backing 9 and the upper backing 14 in the weld line direction and after arranging the succeeding welding torch 20 so that welding is performed on preceding welding beads 4 in the rearward of the upper backing 14, welding is performed simultaneously by the two welding torches 10, 20, making a preceding electrode 1 a positive polarity, whose wire is negative.
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