New stainless steel OCTG (New 15Cr steel pipe : 0.03C-15Cr-6Ni-2Mo-1Cu) with high strength and superior corrosion resistance has been developed and its capability in oil and gas production environment is shown. The yield strength of the new 15Cr steel pipe was higher than 861 MPa (125 ksi), and good Charpy toughness was obtained in extremely low temperature condition. This material showed remarkably high strength even at high temperature of 200 degree C. The CO2 corrosion resistance was significantly improved so that the critical temperature for the developed pipe was more than 200 degree C at 15 MPa CO2 partial pressure. The superior corrosion resistance for revised the new 15Cr steel pipe was obtained by the higher amount of effective Cr in solution. In addition to this, the new 15Cr steel pipe showed good SSC resistance even in its high yield strength in the mildly sour environment. The good SSC resistance for this developed pipe was obtained by the good pitting resistance, induced from high Cr and Mo addition. Introduction Because of its good corrosion resistance in the high carbon dioxide (CO2) and chloride environment, the field application of API 13% Cr (conventional 13Cr) steel pipe is increasing steadily for Oil Country Tubular Goods (OCTG),. However, the conventional 13Cr steel pipe is susceptible to sulfide stress cracking (SSC) in the sour environment containing hydrogen sulfide (H2S)(3, 4) and less corrosion resistant at elevated temperatures. Furthermore high strength OCTG has been required due to the development of deep wells. A number of modified 13Cr steels with high strength and superior corrosion resistance have been proposed.

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