| 摘要 |
Problem to be Solved: A high alloy pipe can be produced that has not only a corrosion resistance required for oil well pipes but also has a targeted strength, without excessively adding alloying components, by selecting the working conditions at the time of the cold rolling. Solution: A method for producing a high alloy pipe having a minimum yield strength of 758.3 to 965.2 MPa, comprising:
preparing a high alloy material pipe having a chemical composition consisting, by mass%, of C: 0.03% or less, Si: 1.0% or less, Mn: 0.3 to 5.0%, Ni: 25 to 40%, Cr: 20 to 30%, Mo: 0 to 4%, Cu: 0 to 3% and N: 0.05 to 0.50%, and the balance being Fe and impurities, by a hot working and optionally by a solid-solution heat treatment; and
producing the high alloy pipe by subsequently subjecting the high alloy material pipe to a cold rolling,
wherein the cold rolling is performed under the conditions that the working ratio Rd, in terms of the reduction of area, in the final cold rolling step falls within a range of larger than 30% and equal to or less than 80%, and the following formula (1) is satisfied: Rd % ‰¥ MYS - 520 / 3.1 - Cr + 6 × Mo + 300 × N wherein Rd and MYS signify the working ratio (%) in terms of the reduction of area and the targeted yield strength (MPa), respectively, and Cr, Mo and N signify the contents (mass%) of the individual elements, respectively. |
