| 摘要 |
PROBLEM TO BE SOLVED: To provide a backing flux for one side welding capable of making practical use of resources by contriving the reclamation of a welding slug generated after submerged arc welding, excellent in hygroscopic resistance in the one side welding, and capable of forming easily a back bead having the uniform and appropriate excess weld height. SOLUTION: The welding slug generated by crushing the slug of a bond flux used for the submerged arc welding is used as a raw material powder, the welding slug is added in the content of 10 mass% or more against the total amount of other flux raw material and the welding slug, after carrying out granulation and baking using a bonding agent, a thermosetting resin is coated. This backing flux has 3.0 mm or less particle size, 1.20-1.80 g/cc bulk density, and the composition of the other flux raw material is SiO2 : 10-45 mass%, Al2 O3 : 2-25 mass%, MgO: 10-40 mass% and SiO2 +Al2 O3 : 25-50 mass%.
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