METHOD FOR PRODUCING HIGH-STRENGTH SEAMLESS CR-NI ALLOY PIPE

摘要

A method for producing a high-strength Cr-Ni alloy seamless pipe, excellent in hot workability and stress corrosion cracking resistance, without causing the lamination during piercing-rolling, comprising:
preparing an alloy billet that has a chemical composition comprising, by mass%, of C: 0.05% or less, Si: 1.0% or less, Mn: less than 3.0%, P: 0.005% or less, S: 0.005% or less, Cu: 0.01 to 4.0%, Ni: 25% or more and less than 35%, Cr: 20 to 30%, Mo: 0.01% or more and less than 4.0%, N: 0.10 to 0.30%, Al: 0.03 to 0.30%, O (oxygen): 0.01% or less, REM (rare earth metal): 0.01 to 0.20%, and the balance being Fe and impurities, and satisfying the following formula (1);
hot working to make a seamless material pipe on the basis of a cross roll piercing process; subjecting a solution treatment; and
cold working. N × P / REM ‰¤ 0.10
wherein P, N and REM in formula (1) represent the contents (mass%) of P, N and REM, respectively. The Cr-Ni alloy may further contain one or more of W, Ti, Nb, Zr, V, Ca and Mg.