Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Sumitomo Metal Industries, Inc.

Masayuki Sagara

Yusaku Tomio

Kunio Kondo

Masaaki Igarashi

Kazuhiro Ogawa

Kazuhiro Shimoda

Tomio Yamakawa

Kenta Yamada

Hirokazu Okada

Hisashi Amaya

Shinnosuke Kurihara

Akiko Tomio

Hiroyuki Hirata

Takahiro Osuki

Hideki Takabe

Haruhiko Kajimura

Daisuke Matsuo

Yohei Otome

Kyohei Kanki

Hitoshi Suwabe

Shigeki Azuma

Daisuke Motoya

Masahiro Seto

Hiroaki Murakami

Hidenori Shitamoto

Shigemitsu Kimura

Tadashi Douhara

Mikiko Noguchi

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

The seamless steel pipe according to the present disclosure includes a chemical composition consisting of, in mass %, C: 0.030% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.030% or less, S: 0.0050% or less, Al: 0.001 to 0.100%, N: 0.0500% or less, O: 0.050% or less, Ni: 5.00 to 6.50%, Cr: more than 10.00 to 13.40%, Cu: more than 1.50 to 3.50%, Mo: 1.00 to 4.00%, V: 0.01 to 1.00%, Ti: 0.050 to 0.300%, and Co: 0.010 to 0.300%, with the balance being Fe and impurities, and satisfying Formula (1), wherein a depassivation pH of an inner surface is 3.00 or less.Cr+2.0 Mo+0.5 Ni+2.0 Cu+0.5 Co≥20.0  (1)

Martensitic stainless seamless steel pipe

The seamless steel pipe according to the present disclosure includes a chemical composition consisting of, in mass %, C: 0.030% or less, Si: 1.00% or less, Mn: 1.00% or less, P: 0.030% or less, S: 0.0050% or less, Al: 0.001 to 0.100%, N: 0.0500% or less, O: 0.050% or less, Ni: 3.00 to 6.50%, Cr: more than 10.00 to 13.40%, Mo: 0.50 to 4.00%, V: 0.01 to 1.00%, Ti: 0.010 to 0.300%, and Co: 0.010 to 0.300%, with the balance being Fe and impurities, and satisfying Formula (1), and a microstructure containing, in volume ratio, 80.0% or more of martensite, wherein a depassivation pH of an inner surface is 3.50 or less.Cr+2.0Mo+0.5Ni+0.5Co≥16.0  (1)

A duplex stainless steel with good low-temperature toughness is provided. The duplex stainless steel has a chemical composition of, in mass %: up to 0.03% C; 0.1 to 0.8% Si; up to 2.3% Mn; up to 0.040% P; up to 0.010% S; up to 0.040% sol. Al; 3 to 7% Ni; 20 to 28% Cr; 0.5 to 2.0% Mo; more than 2.0% and not more than 4.0% Cu; 0.02 to 0.5% Co; 0.1 to 0.35% N; up to 0.010% O; and other elements, the steel having a microstructure including an austenite phase and a ferrite phase, the ferrite phase having an area percentage of 30 to 60%, the steel satisfying the following Formula, (1);0.70&#xd7;Ni&#x2264;Ni&#x2003;&#x2003;(1),where Niand Niare obtained by using an electron-beam microanalyzer to measure Ni content and, in a distribution of Ni content, determining two maximum frequencies, and treating the one with a higher Ni content as Niand treating the one with a lower Ni content as Ni.

Duplex stainless steel and method of manufacturing duplex stainless steel

An austenitic stainless steel is provided which has a chemical composition that consists, by mass %, of: C: 0.015% or less, Si: 1.00% or less, Mn: 2.00% or less, P: 0.05% or less, S: 0.030% or less, Cr: 16.0% or more and less than 22.0%, Ni: 11.0 to 16.0%, Mo: 2.5 to 5.0%, N: 0.07% or more and less than 0.15%, Nb: 0.20 to 0.50%, Al: 0.005 to 0.040%, Sn: 0 to 0.080%, Zn: 0 to 0.0060%, Pb: 0 to 0.030%, and the balance: Fe and impurities, and that satisfies the formula [Mo/Mo&#x2265;0.98] (Mo: Mo amount dissolved in the steel).

Austenitic stainless steel and production method therefor

A Ni&#x2014;Cr alloy material has a chemical composition that consists of; Si: 0.01 to 0.5%, Mn: 0.01 to less than 1.0%, Cu: 0.01 to less than 1.0%, Ni: 48 to less than 55%, Cr: 22 to 28%, Mo: 5.6 to less than 7.0%, N: 0.04 to 0.16%, sol.Al: 0.03 to 0.20%, REM: 0.01 to 0.074%, W: 0% or more and less than 8.0%, Co: 0 to 2.0%; one or more of Ca and Mg: 0.0003 to 0.01% in total, and one or more of Ti, Nb, Zr, and V: 0 to 0.5% in total, the balance thereof being Fe and impurities. The impurities include C &#xa3; 0.03%, P &#xa3; 0.03%, S &#xa3; 0.001%, and O &#xa3; 0.01%. The dislocation density r of the Ni&#x2014;Cr alloy material expressed in msatisfies a formula [7.0'10&#xa3;r&#xa3;2.7&#x2032;10&#x2212;2.67&#x2032;10&#x2032;REM].

Ni&#x2014;Cr alloy material and seamless oil country tubular goods using the same

The high alloy for oil well according to the present embodiment consists of, in mass %, C: 0.03% or less, Si: 1.0% or less, Mn: 0.05 to 1.5%, P: 0.03% or less, S: 0.03% or less, Ni: 26.0 to 40.0%, Cr: 22.0 to 30.0%, Mo: 0.01% or more to less than 5.0%, Cu: 0.1 to 3.0%, Al: 0.001 to 0.30%, N: more than 0.05% to 0.30% or less, O: 0.010% or less, and Ag: 0.005 to 1.0%, wherein the alloy satisfies the following Formula (1) and (2), wherein the high alloy for oil well has yield strength of 758 MPa or more:5&#xd7;Cu+(1000&#xd7;Ag)&#x2265;40&#x2003;&#x2003;(1)Cu+6&#xd7;Ag&#x2212;500&#xd7;(Ca+Mg+REM)&#x2264;3.5&#x2003;&#x2003;(2)

High alloy for oil well

A stainless steel contains, by mass %, C: 0.005% to 0.03%, Si: 0.05% to 1.0%, Mn: 0.1% to 4.0%, Ni: 3% to 8%, Cr: 20% to 35%, Mo: 0.01% to 4.0%, Al: 0.001% to 0.30%, N: 0.05% to 0.60%, one or more selected from Re: 2.0% or less, Ga: 2.0% or less, and Ge: 2.0% or less, and a balance consisting of Fe and impurities.

Duplex stainless steel

A method for manufacturing a high alloy pipe comprises hot working, a high alloy material pipe having controlled amounts of C, Si, Mn, P, S, Ni, Cr, Mo, Cu, Al, N, O, and optionally Ca, Mg, and rare earth elements, with the balance Fe. The pipe composition satisfies the formula N&#xd7;O&#x2266;0.001. The pipe is subjected to cold working to form the high alloy pipe, wherein the final cold working process is performed under the condition that a working ratio Rd in the reduction of area satisfies 15&#x2266;Rd (%)&#x2266;370&#xd7;(C+N), where N, O and C are the contents (by mass percent) of the respective elements, and Rd is the working ratio (%) in the reduction of area. The pipe has an excellent ductility and an excellent corrosion resistance when cold working is performed to obtain a high strength after pipe-making.

Method for manufacturing a high alloy pipe

A starting material to be extruded made of a high alloy comprising, in mass %, Cr: 20 to 30% and Ni: more than 22% and 60% or less is heated to a temperature predetermined according to the contents of Mo and W and is subjected to a hot-extrusion process, the heating temperature T (&#xb0; C.) satisfying a relationship of Formula (1), (2), or (3), which is expressed in terms of the average cross-sectional area A (mm) of the starting material to be extruded, the extrusion ratio EL (&#x2212;), and the extrusion speed V (mm/s). As a result, a high-alloy seamless tube can be produced without generating cracking and/or seam flaws.When 0%&#x2266;Mo+0.5W&#x3c;4%:&#x2266;1343&#x2212;0.001322&#xd7;&#x2212;1.059&#xd7;&#x2212;0.129&#xd7;&#x2003;&#x2003;(1)When 4%&#x2266;Mo+0.5W&#x3c;7%:&#x2266;1316&#x2212;0.001322&#xd7;&#x2212;1.059&#xd7;&#x2212;0.129&#xd7;&#x2003;&#x2003;(2)When 7%&#x2266;Mo+0.5W:&#x2266;1289&#x2212;0.001322&#xd7;&#x2212;1.059&#xd7;&#x2212;0.129&#xd7;&#x2003;&#x2003;(3)

Process for producing high-alloy seamless tube

This invention relates to a welded line pipe structure for transporting corrosive petroleum or natural gas. It is constituted by martensitic stainless steel pipes containing 8&#x2013;16% Cr and at most 0.05% C. By suitably controlling the welding conditions at the time of girth welding of the steel pipes so as to ensure that the Cr concentration in grain boundary Cr-depleted portions existing immediately beneath a weld oxide scale is at least 5%, the occurrence of SCC in a high temperature COenvironment can be prevented.

Welded structure having improved resistance to stress corrosion cracking

An austenitic stainless steel of the present invention has the following chemical composition based on percent by weight: C: 0.05% or less, Si: 1.0% or less, Mn: 2.0% or less, P: 0.04% or less, S: 0.01% or less, Ni: from 12 to 27%, Cr: from 15 to 26%, Cu: over 3.0 to 8.0%, Mo: over 2.0 to 5.0%, Nb: 1.0% or less, Ti: 0.5% or less, W: 5.0% or less, Zr: 1.0% or less, Al: 0.5% or less, N: under 0.05%, Ca: 0.01% or less, B: 0.01% or less, rare earth elements: 0.01% or less in total, and the balance Fe and unavoidable impurities. The austenitic stainless steel has excellent sulfuric acid corrosion resistance and excellent workability.

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Tokyo, Japan

Masayuki Sagara