61results about How to "Excellent SSC resistance" patented technology

There is provided a seamless steel pipe for line pipe, wherein a chemical composition consists, by mass percent, of C: 0.03-0.10%, Si: ≦0.50%, Mn: 1.0-2.0%, P: ≦0.050%, S: ≦0.005%, Cr: 0.05-1.0%, Mo: 0.01-0.30%, Al: 0.001-0.10%, N: ≦0.01%, Ni: 0.04-2.0%, Ca: 0.0005-0.0050%, Cu: 0-2.0%, Ti: 0-0.05%, Nb: 0-0.05%, V: 0-0.10%, the balance: Fe and impurities, and satisfies the conditions of Cu+Ni: ≧0.10%, and Mo+V: ≦0.30%, wherein in a scale formed on the surface of the steel pipe, metal particles consisting mainly of Ni or Cu having an average circle-equivalent diameter of 0.1-5 μm exist, and a distance from a boundary between the base metal of the steel pipe and the scale to a region in which the metal particles do not exist is 20 μm or longer.

A high-strength seamless steel pipe for oil country tubular goods comprising, by mass %, C: 0.20% to 0.50%, Si: 0.05% to 0.40%, Mn: more than 0.6% to 1.5% or less, P: 0.015% or less, S: 0.005% or less, Al: 0.005% to 0.1%, N: 0.006% or less, Mo: more than 1.0% to 3.0% or less, V: 0.05% to 0.3%, Nb: 0.001% to 0.020%, B: 0.0003% to 0.0030%, O: 0.0030% or less, and Ti: 0.003% to 0.025%, and wherein Ti / N: 2.0 to 5.0 is satisfied, a volume fraction of a tempered martensitic is 95% or more, prior austenite grains have a grain size number of 8.5 or more, and in a cross-section perpendicular to a rolling direction, the number of nitride-based inclusions having a grain size of 4 m or more is 100 or less per 100 mm2, the number of nitride-based inclusions having a grain size of less than 4 μm is 1000 or less per 100 mm2, the number of oxide-based inclusions having a grain size of 4 μm or more is 40 or less per 100 mm2, and the number of oxide-based inclusions having a grain size of less than 4 μm is 400 or less per 100 mm2, and methods of producing the same.

A steel for an oil well pipe, having high strength and excellent SSC resistance, consists of, by mass %, C: 0.30 to 0.60%, Si: 0.05 to 0.5%, Mn: 0.05 to 1.0%, Al: 0.005 to 0.10%, Cr+Mo: 1.5 to 3.0%, wherein Mo is 0.5% or more, V: 0.05 to 0.3%, Nb: 0 to 0.1%, Ti: 0 to 0.1%, Zr: 0 to 0.1%, N (nitrogen): 0 to 0.03%, Ca: 0 to 0.01%, and the balance Fe and impurities; P 0.025% or less, S 0.01% or less, B 0.0010% or less and O (oxygen) 0.01% or less. The method involves heating the steel at 1150° C. or more; producing a seamless steel pipe by hot working; water-cooling the pipe to a temperature in a range of 400 to 600° C. immediately after finishing the working; and subjecting the pipe to a heat treatment for bainite isothermal transformation in a range of 400 to 600° C.

Provided is a high-strength seamless steel pipe having the composition which contains, by mass %, 0.20 to 0.50% C, 0.05 to 0.40% Si, 0.3 to 0.9% Mn, 0.015% or less P, 0.005% or less S, 0.005 to 0.1% Al, 0.008% or less N, 0.6 to 1.7% Cr, 0.4 to 1.0% Mo, 0.01 to 0.30% V, 0.01 to 0.06% Nb, 0.0003 to 0.0030% B, and 0.0030% or less O (oxygen). The high-strength seamless steel pipe has the microstructure where a volume fraction of a tempered martensitic phase is 95% or more, and prior austenitic grains have a grain size number of 8.5 or more, and a segregation degree index Ps which is defined by a formula Ps=8.1 (XSi+XMn+XMo)+1.2XP relating to XM which is a ratio between a segregated portion content and an average content is set to less than 65.

The present invention provides a steel which simultaneously satisfies a plurality of characteristics, specifically, a steel for tubes with excellent sulfide stress cracking resistance, including, C: 0.2 to 0.7%; Si: 0.01 to 0.8%; Mn: 0.1 to 1.5%; S: not more than 0.005%; P: not more than 0.03%; Al: 0.0005 to 0.1%; Ti: 0.005 to 0.05%; Ca: 0.0004 to 0.005%; N: not more than 0.007%; Cr: 0. 1 to 1.5%; and Mo: 0.2 to 1.0%; the balance being Fe, Mg and impurities, being characterized in that: the content of Mg is not less than 1.0 ppm and not more than 5.0 ppm; and inclusions of not less than 50% of the total number of those in steel have such a morphology that Mg—Al—O-based oxides exist at the central part of the inclusion, Ca—Al-based oxides enclose the Mg—Al—O-based oxides, and Ti-containing-carbonitrides further exist on a periphery of the Ca—Al-based oxides.

The present invention provides a martensitic stainless steel for oil wells that has good SSC resistance and excellent low-temperature toughness under the coexistence of Cl-, wet CO2 and a small amount of H2S. The steel material contains, by mass %, C: 0.16-0.22%, Si: 0.1-0.8%, Mn: 0.25-1.00%, P: 0.025% or less, S: 0.010% or less, Cr: 12.0-13.5%, Al: 0.010% or less, Ni: 0-0.2%, Cu: 0-0.10%, Mo: 0-0.20%, Ti: 0-0.050%, N: 0.01-0.1%, and the balance is composed of Fe and impurities. It may also contain predetermined amounts of one or more of Nb and V and / or predetermined amounts of one or more of Ca, Mg, La, and Ce.

Low-alloy oil-well steel pipe includes a composition consisting, in mass %, of C: 0.40 to 0.65%, Si: 0.05 to 0.50%, Mn: 0.10 to 1.00%, P: 0.020% or less, S: 0.0020% or less, Cu: 0.15% or less, Cr: 0.40 to 1.50%, Mo: 0.50 to 2.50%, V: 0.05 to 0.25%, Ti: 0 to less than 0.01%, Nb: 0.01 to 0.2%, sol.Al: 0.010 to 0.100%, N: 0.006% or less, B: 0 to 0.0015%, and Ca: 0 to 0.003%, the balance being Fe and impurities. The structure has tempered martensite and 0 to less than 2% volume ratio of retained austenite. A grain size number of prior-austenite grain in the structure is 9.0 or more. An equivalent circular diameter of a sub-structure surrounded by a boundary having a crystal orientation difference of 15° or more from a packet boundary, a block boundary and a lath boundary is 3 μm or less for the tempered martensite.

An oil well steel pipe for embedding-expanding excellent in the SSC resistance after expanding. The pipe is made of a steel consisting of, by mass %, C: 0.05 to 0.45%, Si: 0.1 to 1.5%, Mn: 0.1 to 3.0%, P: 0.03% or less, S: 0.01% or less, sol.Al: 0.05% or less, and the balance being Fe and impurities, with a soluble N content of 40 ppm or less. The steel can comprise one or more selected from V, Ti, Nb, B, Cr, Mo, Ni, Cu and Ca.

The present invention provides a steel which simultaneously satisfies a plurality of characteristics, specifically, a steel for tubes with excellent sulfide stress cracking resistance, including, C: 0.2 to 0.7%; Si: 0.01 to 0.8%; Mn: 0.1 to 1.5%; S: not more than 0.005%; P: not more than 0.03%; Al: 0.0005 to 0.1%; Ti: 0.005 to 0.05%; Ca: 0.0004 to 0.005%; N: not more than 0.007%; Cr: 0.1 to 1.5%; and Mo: 0.2 to 1.0%; the balance being Fe, Mg and impurities, being characterized in that: the content of Mg is not less than 1.0 ppm and not more than 5.0 ppm; and inclusions of not less than 50% of the total number of those in steel have such a morphology that Mg—Al—O-based oxides exist at the central part of the inclusion, Ca—Al-based oxides enclose the Mg—Al—O-based oxides, and Ti-containing-carbonitrides further exist on a periphery of the Ca—Al-based oxides.

The invention provides a martensitic stainless steel seamless pipe for oil country tubular goods having high strength, and excellent sulfide stress corrosion cracking resistance and a method for manufacturing the same. The martensitic stainless steel seamless pipe for oil country tubular goods has a yield stress of 655 to 758 MPa, and has a composition containing, in mass %, C: 0.10% or less, Si: 0.5% or less, Mn: 0.05 to 2.0%, P: 0.030% or less, S: 0.005% or less, Ni: 4.0 to 8.0%, Cu: 0.02% or more and less than 1.0%, Cr: 10.0 to 14.0%, Mo: 1.0 to 3.5%, V: 0.003 to 0.2%, Co: 0.02% or more and less than 1.0%, Al: 0.1% or less, N: 0.1% or less, Ti: 0.50% or less, and the balance Fe and incidental impurities, wherein C, Mn, Cr, Cu, Co, Ni, Mo, W, Nb, N, and Ti satisfy the predetermined relations.

This high-strength steel material for oil wells has a chemical composition which includes, in mass%, 0.70-1.8% of C, 0.05-1.00% of Si, 12.0-25.0% of Mn, 0.003-0.06% of Al, not more than 0.03% of P, not more than 0.03% of S, not more than 0.10% of N, over 0.5% but not more than 2.0% of V, 0-2.0% of Cr, 0-3.0% of Mo, 0-1.5% of Cu, 0-1.5% of Ni, 0-0.5% of Nb, 0-0.5% of Ta, 0-0.5% of Ti, 0-0.5% of Zr, 0-0.005% of Ca, 0-0.005% of Mg, and 0-0.015% of B, the remainder comprising Fe and impurities, and which satisfies [0.6< / =C-0.18V-0.06Cr<1.44]. The metallographic structure substantially comprises an austenite single phase. V carbides having a circle-equivalent diameter of 5-100 nm are present in a number density of at least 20 / [mu]m2. The yield strength is at least 654 MPa.

An oil well steel pipe for embedding-expanding excellent in the SSC resistance after expanding. The pipe is made of a steel consisting of, by mass %, C: 0.05 to 0.45%, Si: 0.1 to 1.5%, Mn: 0.1 to 3.0%, P: 0.03% or less, S: 0.01% or less, sol.Al: 0.05% or less, and the balance being Fe and impurities, with a soluble N content of 40 ppm or less. The steel can comprise one or more selected from V, Ti, Nb, B, Cr, Mo, Ni, Cu and Ca.

Provided herein is a martensitic stainless steel seamless pipe, intended for oil country tubular goods, having high strength, and excellent sulfide stress corrosion cracking resistance. A method for producing such a martensitic stainless steel seamless pipe is also provided. The martensitic stainless steel seamless pipe for oil country tubular goods has a composition that contains, in mass %, C: 0.035% or less, Si: 0.5% or less, Mn: 0.05 to 0.5%, P: 0.03% or less, S: 0.005% or less, Cu: 2.6% or less, Ni: 5.3 to 7.3%, Cr: 11.8 to 14.5%, Al: 0.1% or less, Mo: 1.8 to 3.0%, V: 0.2% or less, N: 0.1% or less, and the balance Fe and unavoidable impurities, and in which C, Mn, Cr, Cu, Ni, Mo, W, Nb, N, and Ti satisfy the predetermined relations.

Provided is a low alloy oil-well steel pipe having a yield strength of 793 MPa or more, and an excellent SSC resistance. A low alloy oil-well steel pipe according to the present invention includes a chemical composition consisting of: in mass%, C: 0.25 to 0.35%; Si: 0.05 to 0.50%; Mn: 0.10 to 1.50%; Cr: 0.40 to 1.50%; Mo: 0.40 to 2.00%; V: 0.05 to 0.25%; Nb: 0.010 to 0.040%; Ti: 0.002 to 0.050%; sol. Al: 0.005 to 0.10%; N: 0.007% or less; B: 0.0001 to 0.0035%; and Ca: 0 to 0.005%; and a balance being Fe and impurities. In a microstructure of the low alloy oil-well steel pipe, a number of cementite particles each of which has an equivalent circle diameter of 200 nm or more is 100 particles / 100 μm2 or more. The above low alloy oil-well steel pipe has a yield strength of 793 MPa or more.

A seamless steel pipe produced by heating a steel billet, which has a chemical composition C: 0.15 to 0.20%, Si: not less than 0.01% to less than 0.15%, Mn: 0.05 to 1.0%, Cr: 0.05 to 1.5%, Mo: 0.05 to 1.0%, Al≦0.10%, V: 0.01 to 0.2%, Ti: 0.002 to 0.03%, B: 0.0003 to 0.005% and N: 0.002 to 0.01%, further optionally one or more of Ca, Mg and REM in a specific amount, under the provision that the conditions “C+(Mn / 6)+(Cr / 5)+(Mo / 3)≧0.43” and “Ti×N<0.0002−0.0006×Si” are satisfied, with the balance being Fe and impurities, wherein P≦0.025%, S≦0.010% and Nb<0.005% among the impurities, to a temperature of 1000 to 1250° C. followed by pipe-making rolling at a final rolling temperature 900 to 1050° C., and then quenching the resulting steel pipe directly from a temperature not lower than the Ar3 transformation point followed by tempering at a temperature range from 600° C. to the Ac1 transformation point, or instead of the above after the said pipe-making rolling, complementarily heating the resulting steel pipe in a temperature range from the Ac3 transformation point to 1000° C. in-line, and then quenching it from a temperature not lower than the Ar3 transformation point followed by tempering at a temperature range from 600° C. to the Ac1 transformation point, has high strength and excellent toughness and at the same time has a high yield ratio and is excellent in SSC resistance as well.

A seamless steel pipe for line pipe has a chemical composition consisting, by mass percent, of C: 0.03-0.15%, Si: ≦0.50%, Mn: 1.0-2.0%, P: ≦0.050%, S: ≦0.005%, Cr: 0.1-1.0%, Al: 0.001-0.10%, N: ≦0.01%, Ni: 0.05-2.0%, B: 0.0003-0.0015%, Ca: 0.0002-0.0050%, Mo: 0.10-0.50%, Ti: 0.001-0.05%, Cu: 0-2.0%, Nb: 0-0.05%, V: 0-0.10%, the balance: Fe and impurities, and satisfying the conditions of 2Nb+4V+Mo≦0.50, wherein a metal micro-structure of the steel pipe contains 50% or more of bainite, in an area fraction, a wall thickness of the steel pipe is 25 mm or larger, and in a scale formed on the surface of the steel pipe, metal particles consisting mainly of Ni or Cu having an average circle-equivalent diameter of 0.1-5 mm exist. A distance from a boundary between the base metal of the steel pipe and the scale to a region in which the metal particles do not exist is 20 mm or longer.

A steel material for oil country tubular goods that has a high strength and excellent SSC resistance is provided. The steel material according to this invention contains, in mass %, C: more than 0.45 to 0.65%, Si: 0.10 to 1.0%, Mn: 0.1 to 1.0%, P: 0.050% or less, S: 0.010% or less, Al: 0.01 to 0.1%, N: 0.01% or less, Cr: 0.1 to 2.5%, Mo: 0.25 to 5.0%, and Co: 0.05 to 5.0%, and satisfies expressions (1) and (2), and contains 90% or more of tempered martensite by volume ratio:C+Mn / 6+(Cr+Mo+V) / 5+(Cu+Ni) / 15−Co / 6+α≥0.70  (1)(3C+Mo+3Co) / (3Mn+Cr)≥1.0  (2)Effective B=B−11(N−Ti / 3.4) / 14  (3)where, α in expression (1) is 0.250 when effective B (mass %) defined by expression (3) is 0.0003% or more, and is 0 when effective B is less than 0.0003%.

A seamless steel pipe contains, (mass %), C: 0.02 to 0.15%; Si: 0.05 to 0.5%; Mn: 0.30 to 2.5%; Al: 0.01 to 0.10%; Ti: 0.001 to 0.010%; N: up to 0.007%; Cr: 0.05 to 1.0%; Mo: not less than 0.02% and less than 0.5%; Ni: 0.03 to 1.0%; Cu: 0.02 to 1.0%; V: 0.020 to 0.20%; Ca: 0.0005 to 0.005%; and Nb: 0 to 0.05%, where carbon equivalent is not less than 0.430% and less than 0.500%, the microstructure main phase from the surface to an in-the-wall portion is tempered martensite or tempered bainite, prior austenite grain size is lower than 6.0, a portion between 1 mm from the inner surface and 1 mm from the outer surface has Vickers hardness of 250 Hv or lower, and yield strength is 555 MPa or higher.

The seamless steel pipe of the present embodiment consists of in mass %, C: 0.21 to 0.35%, Si: 0.10 to 0.50%, Mn: 0.05 to 1.00%, P: 0.025% or less, S: 0.010% or less, Al: 0.005 to 0.100%, N: 0.010% or less, Cr: 0.05 to 1.50%, Mo: 0.10 to 1.50%, Nb: 0.010 to 0.050%, B: 0.0003 to 0.0050%, and Ti: 0.002 to 0.050%, the balance being Fe and impurities. In a main body region of the seamless steel pipe, a grain size number of prior-austenite grain conforming to ASTM E112 is 7.0 or more, a difference between a maximum value and a minimum value of the grain size number is 1.0 or less, yield strength is 655 to less than 862 MPa, and a difference between a maximum value and a minimum value of tensile strength is 27.6 MPa or less.

A thick-wall oil-well steel pipe has a wall thickness of 40 mm or more, excellent SSC resistance and high strength. The thick-wall oil-well steel pipe has a composition containing, in mass %, C: 0.40 to 0.65%, Si: 0.05 to 0.50%, Mn: 0.10 to 1.0%, P: 0.020% or less, S: 0.0020% or less, sol. Al: 0.005 to 0.10%, Cr more than 0.40 to 2.0%, Mo: more than 1.15 to 5.0%, Cu: 0.50% or less, Ni: 0.50% or less, N: 0.007% or less, and O: 0.005% or less. The number of carbide which has a circle equivalent diameter of 100 nm or more and contains 20 mass % or more of Mo is 2 or less per 100 mm2. The thick-wall oil-well steel pipe has yield strength of 827 MPa or more. A difference between a maximum value and a minimum value of the yield strength in the wall-thickness direction is 45 MPa or less.

Provided is a high-strength seamless steel pipe having the composition which contains, by mass %, 0.20 to 0.50% C, 0.05 to 0.40% Si, 0.3 to 0.9% Mn, 0.015% or less P, 0.005% or less S, 0.005 to 0.1% Al, 0.008% or less N, more than 0.6% and 1.7% or less Cr, more than 1.0% and 3.0% or less Mo, 0.01 to 0.30% V, 0.001% or more and less than 0.01% Nb, 0.0003 to 0.0030% B, and 0.0030% or less O (oxygen). The high-strength seamless steel pipe has the microstructure where a volume fraction of a tempered martensitic phase is 95% or more, and prior austenitic grains have a grain size number of 8.5 or more, and a segregation degree index Ps which is defined by a formula Ps=8.1 (XSi+XMn+XMo)+1.2XP is set to less than 65.

A low-alloy steel pipe includes C: 0.15% to less than 0.30%, Si: 0.05 to 1.00%, Mn: 0.05 to 1.00%, P: at most 0.030%, S: at most 0.0050%, Al: 0.005 to 0.100%, O: at most 0.005%, N: at most 0.007%, Cr: 0.10% to less than 1.00%, Mo: 1.0% to not more than 2.5%, V: 0.01 to 0.30%, Ti: 0.002 to 0.009%. Nb: 0 to 0.050%, B: 0 to 0.0050%, Ca: 0 to 0.0050%, Mo / Cr≥2.0, and the balance being Fe and impurities. The pipe has a crystal grain size number of 7.0 or more, 50 or more particles of cementite based on equivalent circle diameter and area of the matrix, M2C-based alloy carbide in a number density of not less than 25 / μm2, and a yield strength of 758 MPa or more.