Patent ID: 8604382

Claim:
A method for manufacturing a laser welded steel pipe in which a steel strip is formed into a cylindrical open pipe with a forming roll and then the longitudinal edge of the open pipe is welded by irradiating the outer surface of the open pipe with a laser beam while compressing the longitudinal edge of the open pipe with a squeeze roll, comprising: a step of monitoring an irradiation point of the laser beam, with which the longitudinal edge is irradiated, from the side of the inner surface of the open pipe, and an assessment step in which conditions of welding with the laser beam are kept unchanged if a keyhole is found penetrating out of the inner surface of the open pipe, or modified if no keyhole is found penetrating out of the inner surface of the open pipe, so that welding can be performed with a keyhole penetrating from the outer surface to the inner surface of the open pipe captured at the irradiation point of the laser beam.