| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for improving toughness in a heat affected zone in a multilayered weld joint, a fillet weld joint and a high-heat input weld joint by one pass or several passes, all of a steel product. <P>SOLUTION: This improving method is characterized by striking treatment with an ultrasonic vibration terminal or shot peening treatment with an ultrasonic vibration steel ball carried out onto the surface of the heat affected zone formed by the final pass for the multilayer weld joint of the steel product, which makes the average value of each major axis of crystals existing in the layer from the surface to 2 mm or deeper of the steel product to be equivalent to the crystal grain size in the base metal before welding in the 1/4 depth of the sheet thickness t from the surface of the steel product, in a metal structure adjacent to a fusion line (FL) between the base metal and a welding metal in the heat affected zone formed by the final pass. <P>COPYRIGHT: (C)2004,JPO |
