IMPACT TREATMENT METHOD FOR IMPROVING FATIGUE CHARACTERISTICS OF WELDED JOINT, IMPACT TREATMENT DEVICE FOR IMPROVING FATIGUE CHARACTERISTICS FOR SAME, AND WELDED STRUCTURE SUPERIOR IN FATIGUE RESISTANCE CHARACTERISTICS

摘要

An impact treatment method for improving fatiguecharacteristics of a welded joint comprising pressing animpact pin against the surface of a base metal materialnear a toe of a weld bead and making it move relativelyto the weld line direction to apply hammer peeningtreatment or ultrasonic impact treatment, characterizedby using as the impact pin an impact pin having a tipcurvature radius of 1/2 or less of a thickness of themetal material and between 2 to 10 mm and, on a surfaceof a base metal material up to a range where a distancefrom the toe of the weld bead to the center of the impacttreatment position is within 2.5 times the tip curvatureradius of the impact pin and where the impact pin doesnot contact the weld metal during impact treatment,applying hammer peening or ultrasonic impact treatment soas to cause by the impact pin residual plasticdeformation where an impact dent has a groove depth of0.1 to 2 mm, the tip curvature radius of the impact pinor less, and 1/10th or less of the thickness of the metalmaterial and where the impact dent has a width of 1.5 to15 mm and five times or more the groove depth.