| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent cracks that generate in the border between the shaft and blade of a screw by providing a laser irradiation means and a guide mem ber, which maintains a distance constantly against the screw blade, in a second holder part movable upward along the inclined part of a first holder, and heating in a specific temperature range. SOLUTION: After welding in repairing or forming an underwater screw, a laser beam is emitted to a sensitization structure affected by the heat of a weld zone and to a stress concentration part, applying a surface melting heat treatment within the range of 1,500-2,000 deg.C, attaining fusion of fine cracks and stabilization of the internal structure, and thereby within the fine cracks and internal stress. A flange 10 retains an optical system 12 for emitting a laser beam, while a guide pin 11 for holding a space constantly between the optical system 12 and the screw 4 is attached to the lower part of the flange 10. In the melting heat treatment process, the optical system 12 moves vertically while profiling the blade surface of the screw 4 by means of the guide pin 11 as a rotary table 3 rotates, emitting a laser beam along a prescribed position.</p> |
