| 摘要 |
PROBLEM TO BE SOLVED: To provide a new method of welding, in which nitrogen does not reach the supersaturation in the composition of a welded metal in a molten state, the average composition of the welded metal has a sufficient corrosion resistance under the environment of seawater, and the welded metal has the mechanical characteristics and keeps the corrosion resistance equivalent to those of a base metal. SOLUTION: In a welding work where a base metal is a high nitrogen content stainless steel containing nitrogen corresponding to more than the solubility which becomes equilibrium with N2 at 1 atm when the metal is molten, the welding is executed in a way that the ratio of a cross-sectional area of the molten part of a base material to the cross-sectional area of a welded metal at each welding path is defined as a dilution rate D (SPM/SWM), the concentrations of Cr, Ni, Mo, and N in the base material are denoted by %CrP, %NiP, %MoP, and %NP, respectively, and the concentrations of Cr, Ni, and Mo in the welded material are denoted by %CrF, %NiF, and %MoF, respectively, and the composition of the welding material and the dilutionrate are so decided that these quantities satisfy the following two relations (A) and (B); (A) %NP×D<=0.028×[%CrP×D+%CrF×(1-D)+0.014[%MoP×D+% MoF×(1-D)] -0.0060×[%NiP×D+%NiF×(1-D)-0.26 (B) [%CrP×D+%CrF(1-D)]+3×[% MoP×D+%MoF×(1-D)]+8×%NP×D>=38.
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