| 摘要 |
PURPOSE:To make the formation of a superior welded joint by high speed welding possible in the stage of one side welding of members to be welded having a narrow groove by decreasing a welding heat input and performing MIG welding from the initial layer without burn-through and formation of recesses. CONSTITUTION:In the stage of butt welding of thick walled pipes 1, 2, an initial layer is formed round the pipes along a narrow groove 3. Here, in the beginning end part of the initial layer, a root face 5 is melted and solidified beforehand to form a welded layer 6 for the beginning end part by MIG welding. The 1st layer is welded by MIG welding of about 12,000-17,000J/cm welding heat input to form a weld zone 12 of good quality quickly. In succession the welding from the 2nd layer up to excess metal is accomplished by MIG welding at about >=17,000J/cm welding heat input. According to this method, the welded joint part of high quality is formed in the narrow groove in the shorter time than by the prior art which forms the 2nd layer by TIG welding. |
