Method for producing duplex stainless steel pipe, method for straightening, method for regulating strength, and method for operating straightener

Abstract

In straightening a duplex stainless steel pipe on a multi-roll pipe straightener, the value of A defined by the formula (1) is set to not more than 2.0% when it is not necessary to improve the mechanical strength of the pipe, and the value of A is set to more than 2.0% but not more than 3% when it is necessary to improve the mechanical strength of the pipe. Thereby, the mechanical strength of the duplex stainless steel pipe is regulated, A=(Di−Hi)/Di  (1) where each of the symbols in the formula (1) indicates the following: Di: the outer diameter (mm) of the pipe at an entry side of an i-th stand in the straightener, and Hi: the gap (mm) between groove bottom portions of the rolls at an i-th stand in the straightener.

Dependencies are inferred from the claim text.