| 摘要 |
PURPOSE:To obtain the seamless composite pipe of high quality with simple process by forming a dissimilar metal layer by building up dissimilar meal on the inner peripheral face or outer peripheral face of a steel pipe and by obtaining a composite pipe with seamless steel pipe rolling process by heating the dissimilar metal layer. CONSTITUTION:A stainless steel 2 is built up on the inner face of a seamless ordinary steel pipe 1 and the seamless composite steel blank pipe 3 thus obtd. is heated. The pipe expanding rolling with the forging in the peripheral direction which destroys the casting structure of the welding built-up part 2 of the composite steel blank pipe 3 as the main body is performed between a plug 6 and slant rolls 4, 4' by the pipe expanding rolling mil having the slant rolls 4, 4'. Thereafter, the rolling in the pipe axial direction is performed by a plug mill and the seamless composite steel pipe of the perfect inner face stainless steel that the stainless steel layer is elongated is obtd.
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