PROCESS FOR PRODUCTION OF HIGH ALLOY STEEL PIPE

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PROBLEM TO BE SOLVED : To provide a process for the production of a high alloy steel pipe which permits pipe making by hot working and which exhibits satisfactory ductility in cold working conducted after pipe making for the purpose of attaining higher strength and is excellent in corrosion resistance. SOLUTION : The process for the production of the high alloy steel pipe by making a high alloy steel pipe stock having a chemical composition which contains by mass ≤0.03% C, ≤1.0% Si, 0.05-1.5% Mn, ≤0.03% P, ≤0.03% S, >22-40% Ni, 20-30% Cr, 0.01-0.05-0.30% N, ≤0.010% O and the balance Fe with impurities and in which the product of N content and O content satisfies expression (1), by hot working and then subjecting the pipe stock to cold working, is characterized in that the final step of the cold working is conducted under conditions that the reduction ratio (Rd) in terms of reduction of a sectional area satisfies expression (2), the pipe stock containing Ca, Mg and rare-earth metal elements optionally : N×O≤0.001...(1), 15≤Rd(%)≤370×(C+N)...(2), wherein N, O and C represent the content (mass%) of respective elements and Rd represents the reduction ratio (%) in terms of reduction of the sectional area. COPYRIGHT : (C)2009, JPO&INPIT