Abstract
The box section welded members were made by using low transformation temperature welding material without preheating and postweld heat treatment. The expansion of weld metal due to the transformation from austenite to marensite around room temperature induced the compressive residual stress of-159 MPa along the weld line. The fatigue strength at 2×106 cycles was improved about 1.3 times as large as that of a usual box section welded member. The blowholes of which size was up to 4.5 mm did not induce the fatigue crack in the compressive residual stress field.
