RAW PIPE OF Fe-Ni ALLOY AND METHOD FOR PRODUCTION THEREOF

摘要

A raw pipe made of an Fe-Ni alloy, which has a chemical composition that C: 0.04 % or less, Si: 0.50 % or less, Mn: 0.01 to 6.0 %, P: 0.03 % or less, S: 0.01 % or less, Cr: 20 to 30 %, Ni: 30 to 45 %, Mo: 0 to 10 %, W: 0 to 20 %, Cu: 0.01 to 1.5 %, Al: 0.01 % or less, N: 0.0005 to 0.20 % and the balance: substantially Fe, with the proviso that Mo(%) + 0.5W(%) is more than 1.5 % and not more than 10 %, wherein 1440 - 6000P - 100S - 2000C = 1300, Ni + 10(Mo + 0.5W) + 100N = 120, (Ni - 35) + 10(N - 0.1) - 2(Cr -25) - 5(Mo + 0.5W - 3) + 8 = 0 are satisfied. The above raw pipe made of the Fe-Ni alloy is excellent in the property of the inner surface thereof and thus can be finished into a seamless pipe by the use of Mannesman piercer, and the resultant seamless pipe has excellent mechanical properties and also excellent in the corrosion resistance under a sour gas circumstance. Accordingly, the above raw pipe made of the Fe-Ni alloy can be utilized as a raw pipe for an oil well pipe and a line pipe, and further as a raw pipe for various structural members in a nuclear power plant and a chemical industry plant.