Peening method for improving the fatigue characteristics of a welded joint, peening apparatus for improving the fatigue characteristics, and welded structure having excellent anti-fatigue characteristics

摘要

Provided is a peening method for improving the fatigue characteristics of a welded joint, in which the surface of the base metal material near the toe of a welding bead is moved in the weld line direction while pushing a peening pin thereinto, so that the material surface is subjected to a hammer peening treatment or an ultrasonic peening treatment.  The peening method for improving the fatigue characteristics of a welded joint is characterized in that the tip of the peening pin has a curvature radius that is within the range of 2-10 mm and is at most half the thickness of the metal material, in that the distance from the toe of the welding bead to the center of the peening position is 2.5 times or less of the radius of curvature of the tip of the peening pin, and in that the hammer peening treatment or ultrasonic peening treatment is carried out in a manner such that the peening pin induces residual plastic deformation such that the depth of the peening mark falls within the range of 0.1-2 mm, is at least as deep as the radius of curvature of the tip of the peening pin, and is at most one-tenth of the thickness of the metal material while the width of the peening mark falls within the range of 1.5-15 m and is at least five times the aforementioned depth in the surface of the base metal material within a region where the peening pin does not come into contact with the welded metal during peening.