| 摘要 |
PROBLEM TO BE SOLVED: To drop the interpass temperature by forming unevenness on one side of a backing, directing the side with unevenness to the side opposite to a groove of a member to be welded, bringing the backing close to the member to be welded to achieve the multi-layer welding and to cool a part in the vicinity of a welded part more rapidly. SOLUTION: A cavity part 20 is formed on a lower surface of a backing 2 by a press. An upper side of the backing is brought close to a bottom side of a pair of steels 1, 1 (members to be welded) across a groove part which is a part to be welded, and fixed thereto. A plurality of passes 3 are formed in the groove part, and the steels 1, 1 (members to be welded) are welded. The total thickness of the backing 2 is preferably about 12 mm (±3 mm). The depth of valley of the cavity part 20 is preferably 3 mm (±1 mm). The width of the valley of the cavity part 20 is approximately equal to the depth of the valley, and the face area of the cavity part 20 (the bottom area of the valley) is approximately one half of the face area of the whole backing 2.
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