IMPROVEMENT OF RESIDUAL STRESS ON WELDED JOINT OF STEEL PIPE

摘要

PURPOSE:To apply a large residual compressive stress to a surface to be treated by locally heating the surface opposite from the surface to be treated to apply the stress exceeding the elastic limit to a metallic wall then cooling the heated point. CONSTITUTION:Cooling water is passed in a steel pipe 1 so that the cooling water is made to exist at all times on the surface 3 to be treated if the inside surface side of a welded joint 2 of the steel pipe 1 is the surface 3 to be treated. A tungsten electrode 4 is thereupon operated to locally heat the surface opposite from the surface 3 to be treated by arc heat, thereby applying the stress exceeding the elastic limit onto the metallic wall in the heated part. The heated point is then cooled, by which the stress in the opposite direction is applied to the plastically deformed part generated in the metallic wall. The 2nd and subsequent heating and cooling stages are added if the intended residual compressive stress is not obtd. by the 1st heating and cooling treatment.