PROBLEM TO BE SOLVED: To improve fatigue strength and to prevent weld crack by inducing large compressive residual stress in the toe part of weld by executing arc welding to a material to be welded, using shield gas containing carbonic acid gas and an welding material whose martensitic transformation expansion is ended at a room temp. at which welding is completed or at the vicinity of the temperature.
SOLUTION: As welding material whose martensitic transformation expansion is ended at the room temp. or in the vicinity of the temperature, an alloy containing Ni and Cr is preferable. As for the alloy containing Ni and Cr, an iron base alloy containing, by weight, 2-20% Ni, 2-20% Cr, ≤0.5% C, ≤0.5% Si, ≤2% Mn, ≤0.5% Mo and, moreover, ≤0.5% Nb, Ti, Al, W, Ta, V, Hf and Zr is desirable. However, it is desirable that the total percentage of metallic elements except Ni and Cr is ≤5%. An inert gas containing the carbonic acid gas of ≥10% is preferable as the shield gas.