| 简介 |
The invention provides a process for the production of a high alloy steel 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. A process for the production of high alloy steel pipes by making a high alloy steel pipe stock having a chemical composition which contains by mass C : 0.03% or below, Si : 1.0% or below, Mn : 0.05 to 1.5%, P : 0.03% or below, S : 0.03% or below, Ni : more than 22% to 40%, Cr : 20 to 30%, Mo : 0.01% to less than 4.0%, Cu : 0 to 4.0%, Al : 0.001 to 0.30%, N : more than 0.05% to 0.30%, and O : 0.010% or below with the balance consisting of Fe and impurities and in which the product of N content and O content satisfies the relationship (1) by hot working and then subjecting the pipe stock to cold working, characterized in that the final step of the cold working is conducted under such conditions that the reduction ratio (Rd) in terms reduction of sectional area satisfies the relationship (2), the pipe stock containing Ca, Mg and/or rare earth elements optionally : N Œ O ≤ 0.001 ...(1) 15 ≤ Rd(%) ≤ 370 Œ (C + N) ... (2) [wherein N, O andC represent their respective contents (% by mass) and Rd represents a reduction ratio (%) in terms of reduction of sectional area]. |
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