Nippon Steel & Sumitomo Metal Corporation

Sumitomo Metal Industries, Inc.

Nippon Steel Corporation

Hideki Takabe

Hisashi Amaya

Kunio Kondo

Taro Ohe

Yohei Otome

Yusaku Tomio

Masakatsu Ueda

Kazuhiro Ogawa

Tomohiko Omura

Shinjiro Nakatsuka

Yuji Arai

Kenta Yamada

Keiichi Nakamura

Hiroki Kamitani

Atsushi Soma

Masahiko Hamada

Masayuki Sagara

Daisuke Matsuo

Takahiro Kushida

Toshio Mochizuki

Akira Taniyama

Hajime Osako

Masanao Seo

Toshiharu Abe

Daisuke Motoya

Taro Oe

Nobuaki Komatsubara

Tsutomu Okuyama

Tomoki Mori

Kyohei Kanki

Takuji Nakahata

An alloy material is provided that has a chemical composition consisting of, in mass %, C: 0.030% or less, Si: 0.01 to 1.0%, Mn: 0.01 to 2.0%, P: 0.030% or less, S: 0.0050% or less, Cr: 28.0 to 40.0%, Ni: 32.0 to 55.0%, sol. Al: 0.010 to 0.30%, N: more than 0.30% and not more than 0.000214×Ni−0.03012×Ni+0.00215×Cr−0.08567×Cr+1.927, O: 0.010% or less, Mo: 0 to 6.0%, W: 0 to 12.0%, Ca: 0 to 0.010%, Mg: 0 to 0.010%, V: 0 to 0.50%, Ti: 0 to 0.50%, Nb: 0 to 0.50%, Co: 0 to 2.0%, Cu: 0 to 2.0%, REM: 0 to 0.10%, and the balance: Fe and impurities, and in which Fn1=Mo+(½)W is 1.0 to 6.0, and a yield strength at a 0.2% proof stress is 1103 MPa or more.

Alloy material and oil-well seamless pipe

A steel material according to the present disclosure has a chemical composition consisting of, in mass %: C: 0.15 to 0.45%, Si: 0.05 to 1.00%, Mn: 0.01 to 1.00%, P: 0.030% or less, S: 0.0050% or less, Al: 0.005 to 0.100%, Cr 0.55 to 1.10%, Mo: 0.70 to 1.00%, Ti: 0.002 to 0.020%, V: 0.05 to 0.30%, Nb: 0.002 to 0.100%, B: 0.0005 to 0.0040%, N: 0.0100% or less, O: less than 0.0020%, and the balance being Fe and impurities, and satisfying Formula (1) described in the specification. A grain diameter of a prior-austenite grain is 15.0 μm or less, and an average area of precipitate which is precipitated in a prior-austenite grain boundary is 12.5×10μmor less. A yield strength is 758 to 862 MPa.

Steel material suitable for use in sour environment

A steel bar for a downhole member is provided that is excellent in SCC resistance and SSC resistance. A martensitic stainless steel bar material for a downhole member of the present embodiment has a chemical composition that contains, by mass %, C: 0.020% or less, Si: 1.0% or less, Mn: 1.0% or less, P: 0.03% or less, S: 0.01% or less, Cu: 0.10 to 2.50%, Cr: 10 to 14%, Ni: 1.5 to 7.0%, Mo: 0.2 to 3.0%, Ti: 0.05 to 0.3%, V: 0.01 to 0.10%, Nb: 0.1% or less, Al: 0.001 to 0.1% and N: 0.05% or less, with the balance being Fe and impurities, and satisfies Formula (1) and Formula (2).[Mo]&#x2212;4&#xd7;[total Mo amount in precipitate at R/2 position]&#x2265;1.30&#x2003;&#x2003;(1)[Total Mo amount in precipitate at center position]&#x2212;[total Mo amount in precipitate at R/2 position]&#x2264;0.03&#x2003;&#x2003;(2)

Steel bar for downhole member, and downhole member

A martensitic Cr-containing steel having excellent corrosion resistance, SSC resistance, and IGHIC resistance is provided. A martensitic Cr-containing steel according to the present invention includes: a chemical composition consisting of, by mass %, Si: 0.05 to 1.0%, Mn: 0.1 to 1.0%, Cr: 8 to 12%, V: 0.01 to 1.0%, sol. Al: 0.005 to 0.10%, with the balance being Fe and impurities, wherein an effective Cr amount defined by 'Cr&#x2212;16.6&#xd7;C' is not less than 8%, and an Mo equivalent defined by 'Mo+0.5&#xd7;W' is 0.03 to 2%; a micro-structure wherein a grain size number of prior-austenite crystal grain is not less than 8.0; and a yield strength of less than 379 to 551 MPa, wherein a grain-boundary segregation ratio of Mo and W is not less than 1.5.

Martensitic Cr-containing steel and oil country tubular goods

Provided is duplex stainless steel having high strength, SCC resistance and SSC resistance excellent in a high-temperature chloride environment, and capable of suppressing precipitation of a &#x3c3; phase. The duplex stainless steel of the present embodiment includes, in mass %, of: C: at most 0.03%; Si: 0.2 to 1%; Mn: more than 5.0% to at most 10%; P: at most 0.040%; S: at most 0.010%; Ni: 4.5 to 8%; sol. Al: at most 0.040%; N: more than 0.2% to at most 0.4%; Cr: 24 to 29%; Mo: 0.5 to less than 1.5%; Cu: 1.5 to 3.5%; W: 0.05 to 0.2%; the balance being Fe and impurities, wherein the duplex stainless steel satisfies Formula (1): Cr+8Ni+Cu+Mo+W/2&#x2265;65 . . . (1), where a symbol of each element in Formula (1) represents a content of the element (in mass %).

Duplex stainless steel

A stainless steel for oil wells which has excellent high-temperature corrosion resistance and can stably obtain a strength of not less than 758 MPa is provided. The stainless steel for oil wells contains, by masse, C: not more than 0.05%, Si: not more than 1.0%, Mn: 0.01 to 1.0%, P: not more than 0.05%, S: less than 0.002%, Cr: 16 to 18%, Mo: 1.8 to 3%, Cu: 1.0 to 3.5%, Ni: 3.0 to 5.5%, Co: 0.01 to 1.0%, Al: 0.001 to 0.1%, O: not more than 0.05%, and N: not more than 0.05%, the balance being Fe and impurities, and satisfies Formulas (1) and (2):Cr+4Ni+3Mo+2Cu&#x2267;44&#x2003;&#x2003;(1)Cr+3Ni+4Mo+2Cu/3&#x2266;46&#x2003;&#x2003;(2)

Stainless steel for oil wells and stainless steel pipe for oil wells

A process for producing a welded joint, which includes a weld metal having high strength and high toughness, and containing fewer blowholes, includes the steps of: preparing a base material containing, by mass %, not less than 10.5% of Cr; and subjecting the base material to GMA welding using a shielding gas containing 1 to 2 volume % or 35 to 50 volume % of COgas, and the balance being inert gas, thereby forming a weld metal includes, by mass %, C: not more than 0.080%, Si: 0.20 to 1.00%, Mn: not more than 8.00%, P: not more than 0.040%, S: not more than 0.0100%, Cu: not more than 2.0%, Cr: 20.0 to 30.0%, Ni: 7.00 to 12.00%, N: 0.100 to 0.350%, O: 0.02 to 0.11%, sol. Al: not more than 0.040%, at least one of Mo: 1.00 to 4.00% and W: 1.00 to 4.00%, and the balance being Fe and impurities.

[object Object]

The chemical composition of a stainless steel in accordance with the present invention consists of C: not more than 0.05%, Si: not more than 0.5%, Mn: 0.01 to 0.5%, P: not more than 0.04%, S: not more than 0.01%, Cr: more than 16.0 and not more than 18.0%, Ni: more than 4.0 and not more than 5.6%, Mo: 1.6 to 4.0%, Cu: 1.5 to 3.0%, Al: 0.001 to 0.10%, and N: not more than 0.050%, the balance being Fe and impurities, and satisfies Formulas (1) and (2). Also, the micro-structure thereof contains a martensitic phase and a ferritic phase having a volume ratio of 10 to 40%, and the ferritic phase distribution ratio is higher than 85%.Cr+Cu+Ni+Mo &#x2267;&#x2003;&#x2003;()&#x2212;(C+N)+Mn+Ni+Cu/(Cr+Mo) &#x2266;&#x2212;&#x2003;&#x2003;()

Stainless steel for oil well, stainless steel pipe for oil well, and method of manufacturing stainless steel for oil well

A high-strength stainless steel for oil well having corrosion resistance excellent in a high-temperature environment, having excellent SSC resistance at normal temperature, and having better workability than 13% Cr steels has a chemical composition containing, by mass percent, C: at most 0.05%, Si: at most 1.0%, Mn: at most 0.3%, P: at most 0.05%, S: less than 0.002%, Cr: over 16% and at most 18%, Mo: 1.5 to 3.0%, Cu: 1.0 to 3.5%, Ni: 3.5 to 6.5%, Al: 0.001 to 0.1%, N: at most 0.025%, and O: at most 0.01%, the balance being Fe and impurities, a microstructure containing a martensite phase, 10 to 48.5%, by volume ratio, of a ferrite phase and at most 10%, by volume ratio, of a retained austenite phase, yield strength of at least 758 MPa and uniform elongation of at least 10%.

High-strength stainless steel for oil well and high-strength stainless steel pipe for oil well

The chemical composition of a stainless steel in accordance with the present invention consists of C: not more than 0.05%, Si: not more than 0.5%, Mn: 0.01 to 0.5%, P: not more than 0.04%, S: not more than 0.01%, Cr: more than 16.0 and not more than 18.0%, Ni: more than 4.0 and not more than 5.6%, Mo: 1.6 to 4.0%, Cu: 1.5 to 3.0%, Al: 0.001 to 0.10%, and N: not more than 0.050%, the balance being Fe and impurities, and satisfies Formulas (1) and (2). Also, the micro-structure thereof contains a martensitic phase and a ferritic phase having a volume ratio of 10 to 40%, and the ferritic phase distribution ratio is higher than 85%.Cr+Cu+Ni+Mo&#x2267;25.5&#x2003;&#x2003;(1)&#x2212;8&#x2266;30(C+N)+0.5Mn+Ni+Cu/2+8.2&#x2212;1.1(Cr+Mo)&#x2266;&#x2212;4&#x2003;&#x2003;(2)

The problem to be solved is the provision of a high-strength stainless steel pipe having a sufficient corrosion resistance in a high-temperature carbonic acid gas environment and having an excellent sulfide stress cracking resistance at normal temperature. A high-strength stainless steel pipe consist of, by mass %, C: 0.05% or less, Si: 1.0% or less, P: 0.05% or less, S: less than 0.002%, Cr: more than 16% and 18% or less, Mo: more than 2% and 3% or less, Cu: 1% to 3.5%, Ni: 3% or more and less than 5%, Al: 0.001% to 0.1% and O: 0.01% or less, Mn: 1% or less and N: 0.05% or less, and Mn and N in the above ranges satisfy formula (1), and the balance being Fe and impurities; and the metal micro-structure of the stainless steel pipe mainly includes a martensitic phase and comprises 10 to 40% of a ferritic phase by volume fraction and 10% or less of a retained &#x3b3;-phase by volume fraction.[Mn]&#xd7;([N]&#x2212;0.0045)&#x2266;0.001&#x2003;&#x2003;(1)wherein the symbols of elements in formula (1) respectively represent the contents (unit: mass %) of the elements in the steel.

High-strength stainless steel pipe excellent in sulfide stress cracking resistance and high-temperature carbonic-acid gas corrosion resistance

A martensitic stainless steel for welded structures including by mass %, C: 0.001 to 0.05%, Si: 0.05 to 1%, Mn: 0.05 to 2%, P: 0.03% or less, REM: 0.0005 to 0.1%, Cr: 8 to 16%, Ni: 0.1 to 9% and sol. Al: 0.001 to 0.1%; and further including one or more elements selected from among Ti: 0.005 to 0.5%, Zr: 0.005 to 0.5%, Hf: 0.005 to 0.5%, V: 0.005 to 0.5% and Nb: 0.005 to 0.5%; and O: 0.005% or less, N: 0.1% or less, with the balance being Fe and impurities; and the P and REM content satisfies: P&#x2266;0.6&#xd7;REM. This steel possesses excellent SCC (stress corrosion cracking) resistance in welded sections in Sweet environments.

Martensitic stainless steel for welded structures

An oil country tubular good for expansion according to the invention is expanded in a well. The oil country tubular good for expansion has a composition containing, in percentage by mass, 0.05% to 0.08% C, at most 0.50% Si, 0.80% to 1.30% Mn, at most 0.030% P, at most 0.020% S, 0.08% to 0.50% Cr, at most 0.01% N, 0.005% to 0.06% Al, at most 0.05% Ti, at most 0.50% Cu, and at most 0.50% Ni, and the balance consisting of Fe and impurities, and a structure having a ferrite ratio of at least 80%. The oil country tubular good for expansion has a yield strength in the range from 276 MPa to 379 MPa and a uniform elongation of at least 16%. Therefore, the oil country tubular good according to the invention has a high pipe expansion characteristic.

Oil country tubular good for expansion in well and manufacturing method thereof

A steel for oil well pipe, which has excellent resistance to localized corrosion in CO,environments and corrosion in seawater, and a seamless pipe made of the steel. The steel includes, in weight %, more than 0.10 to 0.30% C, 0.10 to 1.0% Si, 0.1 to 3.0% Mn, 2.0 to 9.0% Cr, 0.01 to 0.10% Al and optionally 0.05 to 0.5% Cu, and the balance including Fe and incidental impurities including not more than 0.03% P and not more than 0.01% S. The steel has a substantially single phase martensitic structure in the as-quenched or as-normalized condition, and yield strength of not lower than 552 MPa in the as-quenched-tempered or as-normalized-tempered condition.

Growing community of inventors

Osaka, Japan

Hideki Takabe