Patent ID: 8637784
Filing Date: 2014-01-28
Classification: B23K,C21D

Abstract:
1. A tubular-body residual-stress improving method for improving residual stress of a cylindrical tubular body by locally irradiating an outer-circumferential surface of a welded portion of the tubular body with laser beams and by moving an irradiation area in a circumferential direction, wherein, a plurality of thermometers are installed on a tubular body to be improved; a temperature history of an outer surface of the tubular body is measured by the plurality of thermometers while the outer surface is irradiated with the laser beams; a highest achieving temperature, a temperature-rising time required for reaching the highest achieving temperature, and a heating length in an axial direction in which the highest achieving temperature stays in a predetermined temperature range are obtained; and a heating width in the circumferential direction is controlled on the basis of a product of the temperature-rising time and a speed of moving the laser beams in the circumferential direction.