Sätt vid tillverkning av ett tjockväggigt rör med liten diameter

摘要

A method of manufacturing a thick-walled small diameter pipe by repeating a process comprising a pipe extension process and a heating process on a pipe to be processed plural times, wherein a machining process on the inner circumferential surface of said pipe to be processed is performed prior to the pipe extension process in the final cycle of said process or a process near the final cycle to remove a black skin layer, cracks and puckers, providing smooth inner surface and excellent proof pressure.