PROCESS FOR PRODUCTION OF HIGH ALLOY STEEL PIPE

摘要

Problem to be Solved There is provided a method for manufacturing a high alloy pipe which can be hot worked for pipe-making, and has an excellent ductility and an excellent corrosion resistance when cold working is further performed to obtain a high strength after pipe-making. Solution 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 not more than 40%, Cr: 20 to 30%, Mo: not less than 0.01% and less than 4.0%, Cu: 0 to 4.0%, Al: 0.001 to 0.30%, N: more than 0.05% and not more than 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 the condition that a working ratio Rd in the reduction of area satisfies formula (2): N × O ‰¤ 0.001 15 ‰¤ Rd % ‰¤ 370 × C + N
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. The high alloy pipe may also contain one or more of Ca, Mg, and rare-earth elements.