59results about How to "Excellent SSC resistance" patented technology

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 (X_Si+X_Mn+X_Mo)+1.2X_P relating to X_M which is a ratio between a segregated portion content and an average content is set to less than 65.

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 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.

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 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 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.