Patent ID: 8701455

Claim:
A method for manufacturing a high alloy pipe, characterized by comprising forming, by hot working, a high alloy material pipe which has a chemical composition that consists of, by mass percent, C: 0.03% or less, Si: 1.0% or less, Mn: 0.05 to 1.5%, P: 0.03% or less, S: 0.03% or less, Ni: more than 22% and less than 35%, Cr: 20 to 30%, Mo: not less than 0.01% and less than 4.0%, Cu: 0.1 to 4.0%, Al: 0.001 to 0.30%, N: 0.06 to 0.30%, and O: 0.010% or less, the balance being Fe and impurities, and that satisfies formula (1) for the product of the N content and the O content, and thereafter performing cold working to form the high alloy pipe, wherein the final cold working process is performed under a condition that a working ratio Rd in the reduction of area satisfies formula (2): N×O≦0.001 (1) 15≦ Rd (%)≦370×(C+N) (2) where N, O and C are the contents (by mass percent) of the respective elements, and Rd is the working ratio (%) in the reduction of area.