Martensitic stainless steel

Abstract

A martensitic stainless steel which has a chemical composition, in mass %, that C: 0.001 to 0.01 %, Si: 0.5 % or less, Mn: 0.1 to 3.0 %, P: 0.04 % or less, S: 0.01 % or less, Cr: 10 to 15 %, Ni: 4 to 8 %, Mo: 2.8 to 5.0 %, Al: 0.001 to 0.10 %, N: 0.07 % or less, Ti: 0 to 0.25 %, V: 0 to 0.25 %, Nb: 0 to 0.25 %, Zr: 0 to 0.25 %, Cu: 0 to 1.0 %, Ca: 0 to 0.005 %, Mg: 0 to 0.005 %, La: 0 to 0.005 %, Ce: 0 to 0.005 %, and the balance: Fe and impurities, with a proviso that the following formulae (1) and (2) are satisfied, and exhibits a yield stress of 758 to 860 MPa. 922.6 - 554.5C - 50.9Mn +2944.8P + 1.056Cr - 81.1Ni + 95.8Mo - 125.1Ti - 1584.9Al - 376.1N = 600 (1) 30C + 0.5Mn + Ni + 0.5Cu - 1.5Si - Cr - Mo + 7.9 = 0 (2) The above martensitic stainless steel can achieve a yield stress of 758 to 860 MPa with a range of tempering temperature being broader than that in the case of a conventional martensitic stainless steel.

Description

technical field [0001] The present invention relates to martensitic stainless steel, and more specifically, to martensitic stainless steel used in a corrosive environment containing corrosive substances such as hydrogen sulfide, carbon dioxide, and chloride ions. Background technique [0002] With the deepening of oil wells and gas wells, martensitic stainless steel used as steel materials for oil wells such as oil well pipes is required to have high strength and high toughness. For this reason, martensitic stainless steel having a yield stress (0.2% yield strength) of 758 to 860 MPa (hereinafter referred to as 110 ksi grade) and a high-strength martensitic stainless steel of 110 ksi grade or higher are being developed. [0003] Martensitic stainless steel for oil wells also has high corrosion resistance of SCC (stress corrosion cracking) resistance and SSC (sulfurization stress corrosion) resistance. This is because oil wells and gas wells are corrosive environments that c...

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