HIGH-STRENGTH STAINLESS STEEL FOR OIL WELL AND HIGH-STRENGTH STAINLESS STEEL PIPE FOR OIL WELL

• Main Authors: AMAYA, HISASHI, OTOME, YOHEI, TAKABE, HIDEKI, KONDO, KUNIO, OHE, TARO
• Format: Patent
• Language: English; French; German
• Published: 06.03.2013
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TREATMENT OF ALLOYS OR NON-FERROUS METALS

There is provided a high-strength stainless steel for oil well having corrosion resistance excellent in a high-temperature environment, having excellent SSC resistance at normal temperature, and having better workability than 13% Cr steels. The high-strength stainless steel for oil well according to the present invention has a chemical composition containing, by mass percent, C: at most 0.05%, Si: at most 1.0%, Mn: at most 0.3%, P: at most 0.05%, S: less than 0.002%, Cr: over 16% and at most 18%, Mo: 1.5 to 3.0%, Cu: 1.0 to 3.5%, Ni: 3.5 to 6.5%, Al: 0.001 to 0.1%, N: at most 0.025%, and O: at most 0.01%, the balance being Fe and impurities, a microstructure containing a martensite phase, 10 to 48.5%, by volume ratio, of a ferrite phase and at most 10%, by volume ratio, of a retained austenite phase, yield strength of at least 758 MPa and uniform elongation of at least 10%.