Stainless steel multifold pipe

摘要

A multifold pipe made by multiple rolling up and turning of a copper coated steel sheet into a multifold pipe, characterized in that said steel sheet is a cold rolled sheet of a super soft austenitic stainless steel comprising by weight: up to 0.05% of C, up to 1.0% of Si, up to 5.0% of Mn, from 9.0% to 15.0% of Ni, from 15.0% to 20.0% of Cr, up to 0.04% of N, up to 5.0% of Cu, the balance being Fe and unavoidable impurities, wherein the alloying elements are further adjusted so that both the two relations (1) and (2) noted below are satisfied: K=20.5+13.0xC+0.99xSi-1.1xMn-Ni-0.4xCu +0.4xCr+117.1xN