Abstract: A method of producing a high performance stainless steel exhibiting corrosion resistance even under a very severe corrosion environment at temperatures of equal to or higher than 180° C., for example, 220° C., while maintaining strength and toughness by improving the corrosion resistance of a conventional martensitic stainless steel with high strength. The martensitic stainless steel includes, in mass %, C: 0.005% to 0.05%, Si: equal to or less than 1.0%, Mn: equal to or less than 2.0%, Cr: 16 to 18%, Ni: 2.5 to 6.5%, Mo: 1.5 to 3.5%, W: equal to or less than 3.5%, Cu: equal to or less than 3.5%, V: 0.01 to 0.08%, Sol.Al: 0.005 to 0.10%, N: equal to or less than 0.05%, and Ta: 0.01 to 0.06%, and the balance Fe with inevitable impurities.

Abstract: A purpose of the present invention is to provide a martensitic stainless steel tube exhibiting excellent performance even in severe corrosive environments in which a partial pressure of hydrogen sulfide exceeds 0.03 bar. Provided is a low C-high Cr alloy steel tube for OCTG (Oil Country Tubular Goods) having minimum yield strength of 862 MPa and excellent corrosion resistance, wherein the steel tube contains, in percent by mass, 0.005 to 0.05% C, 12 to 16% Cr, 1.0% or less Si, 2.0% or less Mn, 3.5 to 7.5% Ni, 1.5 to 3.5% Mo, 0.01 to 0.05% V, 0.02% or less N, and 0.01 to 0.06% Ta and satisfies the relationship in the following formula (1), and the rest comprises Fe and unavoidable impurities. 25-25 (% Ni)+5 (% Cr)+25 (% Mo)?0??(1).

Abstract: A purpose of the present invention is to provide a martensitic stainless steel applicable in environments involving both wet carbon dioxide gas and wet hydrogen sulfide and excellent in weldability, manufacturability, and resistance to strain age hardening. Provided is a martensitic stainless steel having excellent corrosion resistance and resistance to strain age hardening comprising, in percent by mass, 0.02% or less of C, 0.02% or less of N, 0.1 to 0.5% of Si, 0.1 to 0.5% of Mn, 10 to 13% Cr, Ni exceeding 5.0% but 8% or less, 1.5 to 3% of Mo, 0.01 to 0.05% of V, 0.16 to 0.30% of Zr, 0.01 to 0.05% of Ta, and the balance of Fe and unavoidable impurities, wherein the martensitic stainless steel satisfies the condition that the sum of the carbon and the nitrogen exceeds 0.02% but 0.04% or less.

Abstract: The present invention provides a high performance-stainless steel exhibiting a corrosion resistance even under very severe corrosion environments at temperatures of equal to or higher than 180° C., for example, 220° C. while maintaining strength and a toughness by improving a corrosion resistance of a conventional martensitic stainless steel with high strength. The present invention provides a martensitic stainless steel containing, in mass %, C: 0.005% to 0.05%, Si: equal to or less than 1.0%, Mn: equal to or less than 2.0%, Cr: 16 to 18%, Ni: 2.5 to 6.5%, Mo: 1.5 to 3.5%, W: equal to or less than 3.5%, Cu: equal to or less than 3.5%, V: 0.01 to 0.08%, Sol.Al: 0.005 to 0.10%, N: equal to or less than 0.05%, and Ta: 0.01 to 0.06%, and the balance Fe with inevitable impurities.

Abstract: A martensitic stainless steel for inexpensive seamless pipe having 655 MPa yield strength, high toughness and excellent corrosion resistance in high CO2 environments, and a method for manufacturing thereof is provided. The steel comprises C: 0.005-0.05%, Si: 0.1-0.5%, Mn: 0.1-2.0%, P: ?0.05%, S: ?0.005%, Cr: 10.0-12.5%, Mo: 0.1-0.5%, Ni: 1.5-3.0%, N: ?0.02%, Al: 0.01-0.1%, by weight, while FI value defined by the formula [FI=Cr+Mo?Ni?30(C+N)] being 5.00 to 8.49, and balance of substantially Fe. The method comprises the steps of reheating the cooled steel at temperatures from 780° C. to 960° C., quenching the reheated steel, and then tempering the quenched steel at temperatures from 550° C. to 650° C.

Abstract: A purpose of the present invention is to provide a martensitic stainless steel tube exhibiting excellent performance even in severe corrosive environments in which a partial pressure of hydrogen sulfide exceeds 0.03 bar. Provided is a low C-high Cr alloy steel tube for OCTG (Oil Country Tubular Goods) having minimum yield strength of 862 MPa and excellent corrosion resistance, wherein the steel tube contains, in percent by mass, 0.005 to 0.05% C, 12 to 16% Cr, 1.0% or less Si, 2.0% or less Mn, 3.5 to 7.5% Ni, 1.5 to 3.5% Mo, 0.01 to 0.05% V, 0.02% or less N, and 0.01 to 0.06% Ta and satisfies the relationship in the following formula (1), and the rest comprises Fe and unavoidable impurities.

Abstract: A purpose of the present invention is to provide a martensitic stainless steel applicable in environments involving both wet carbon dioxide gas and wet hydrogen sulfide and excellent in weldability, manufacturability, and resistance to strain age hardening. Provided is a martensitic stainless steel having excellent corrosion resistance and resistance to strain age hardening comprising, in percent by mass, 0.02% or less of C, 0.02% or less of N, 0.1 to 0.5% of Si, 0.1 to 0.5% of Mn, 10 to 13% Cr, Ni exceeding 5.0% but 8% or less, 1.5 to 3% of Mo, 0.01 to 0.05% of V, 0.16 to 0.30% of Zr, 0.01 to 0.05% of Ta, and the balance of Fe and unavoidable impurities, wherein the martensitic stainless steel satisfies the condition that the sum of the carbon and the nitrogen exceeds 0.02% but 0.04% or less.

Abstract: A martensitic stainless steel for inexpensive seamless pipe having 655 MPa yield strength, high toughness and excellent corrosion resistance in high CO2 environments, and a method for manufacturing thereof is provided. The steel comprises C: 0.005-0.05%, Si: 0.1-0.5%, Mn: 0.1-2.0%, P: ?0.05%, S: ?0.005%, Cr: 10.0-12.5%, Mo: 0.1-0.5%, Ni: 1.5-3.0%, N: ?0.02%, Al: 0.01-0.1%, by weight, while FI value defined by the formula [FI=Cr+Mo?Ni?30(C+N)] being 5.00 to 8.49, and balance of substantially Fe. The method comprises the steps of reheating the cooled steel at temperatures from 780° C. to 960° C., quenching the reheated steel, and then tempering the quenched steel at temperatures from 550° C. to 650° C.

Abstract: A martensitic stainless steel for inexpensive seamless pipe having 655 MPa yield strength, high toughness and excellent corrosion resistance in high CO2 environments, and a method for manufacturing thereof is provided. The steel comprises C:0.005-0.05%, Si:0.1-0.5%, Mn: 0.1-2.0% P: ?0.005%, S: ?0.005%, Cr: 10.0-12.5%, Mo: 0.1-0.5%, Ni: 1.5-3.0%, N: ?0.02%, Al: 0.01-0.1%, by weight, while FI value defined by the formula [FI=Cr+Mo?Ni?30 (C+N)] being 5.00 to 8.49, and balance of substantially Fe. The method comprises the steps of reheating the cooled steel at temperatures from 780° C. to 960° C., quenching the reheated steel, and then tempering the quenched steel at temperatures from 550° C. to 650° C.

Abstract: A high strength martensitic stainless steel contains:0.06 wt. % or less C, 12 to 16 wt. % Cr, 1 wt. % or less Si, 2 wt. % or less Mn, 0.5 to 8 wt. % Ni, 0.1 to 2.5 wt. % Mo, 0.3 to 4 wt. % Cu, 0.05 wt. % or less N, and the balance being Fe and inevitable impurities;said steel having an area ratio of .delta.-ferrite phase of at most 10%; andsaid steel having fine copper precipitates dispersed in a matrix.And further a method for making the stainless steel comprises austenitizing, cooling and tempering.

Abstract: A martensitic stainless steel having good corrosion resistance suitable for use in an oil well having 0.08 to 0.25 wt. % C, 14 to 16 wt. % Cr, 1.0 wt. % or less Si, 2.0 wt. % or less Mn, 0.5 to 3.0 wt. % Ni, 0.03 to 0.10 wt. % N, 0.04 wt. % or less P, 0.01 wt. % or less S, 0.1 to 1.0 wt. % Mo, the balance being Fe and inevitable impurities. The Cr, C, Ni and N being in amounts such that 20 wt. % .gtoreq.Cr-12C+0.75 Ni+10N.gtoreq.13 wt. %. The martensitic stainless steel having a content of .delta.-ferrite of 10% or less. The martensitic stainless steel can contain at least one of 0.05 to 0.30 wt. % V and 0.01 to 0.1 wt. % Nb. Also the martensitic stainless steel can contain 0.5 to 3.0 wt. % Cu. Further the martensitic stainless steel can contain 0.5 to 3.0 wt. % Cu, and at least one of 0.05 to 3.0 wt. % V and 0.01 to 0.1 wt. % Nb.