| 摘要 |
PURPOSE:To provide a clad steel pipe consisting of an external pipe having high strength and an internal pipe having corrosion resistance by irradiating a laser beam to a double pipe which is slowly cooled after cladding and of which the external pipe is heat treated so as to maintain strength, thereby subjecting the surface of the internal pipe to a soln. heat treatment. CONSTITUTION:A tainless steel inside pipe 2 is superposed relatively on an external carbon steel pipe 1 and hot drawn to obtain a clad steel pipe 3 which is then heat treated by hardening and tempering to maintain the strength. The external pipe 1 is imparted with strength by such treatment. The pipe 3 is set on support rolls 6 and a motor 7 is started to rotate and advance the pipe. At the same time, a laser beam irradiation device 12 is started to radiate a laser beam 14 from a gun 13. The beam is reflected by a reflection mirror 11 to irradiate the inside surface of the internal pipe 2 of the pipe 3, thereby the inside surface is melted to undergo solution treatment. The chromium carbide deposited on the pipe 2 is eliminated and the corrosion resistance is restored and maintained. |
