Sumitomo Metal Industries, Inc.

Nippon Steel Sumitomo Metal Corporation

Masakatsu Ueda

Kunio Kondo

Hisashi Amaya

Kazuhiro Ogawa

Hideki Takabe

Masaaki Igarashi

Keiichi Nakamura

Takahiro Kushida

Yasuto Fukada

Tomoki Mori

Yuuichi Komizo

Hiroyuki Hirata

Masahiko Hamada

Toshiro Anraku

Akira Taniyama

Taro Ohe

Toshiharu Abe

Kazuyo Kushida, Legal Representative

Nobuhiko Hiraide

A martensitic stainless steel oil country tubular good contains, by mass, 0.005% to 0.1% C, 0.05% to 1% Si, 1.5% to 5% Mn, at most 0.05% P, at most 0.01% S, 9% to 13% Cr, at most 0.5% Ni, at most 2% Mo, at most 2% Cu, 0.001% to 0.1% Al, and 0.001% to 0.1% N, with the balance being Fe and impurities, and the pipe has a Cr-depleted region under the surface. The martensitic stainless steel oil country tubular good according to the present invention does not have a passive film on the surface and corrodes wholly at low speed. In addition, the Ni content is reduced, which allows uneven corrosion to be prevented. Therefore, SCC can be prevented from being generated in spite of the presence of a Cr-depleted region.

Martensitic stainless steel oil country tubular good

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

A martensitic stainless steel comprising C: 0.01-0.10%, Si: 0.05-1.0%, Mn: 0.05-1.5%, P: not more than 0.03%, S: not more than 0.01%, Cr: 9-15%, Ni: 0.1-4.5%, Al: not more than 0.05% and N: not more than 0.1% in mass %, and further comprising at least one of Cu: 0.05-5% and Mo: 0.05-5%, the residual being Fe and impurities, is provided, wherein the contents of Cu and Mo satisfy the following formula (a) or (b),0.2%&#x2266;Mo+Cu/4&#x2266;5%&#x2003;&#x2003;(a)0.55%&#x2266;Mo+Cu/4&#x2266;5%&#x2003;&#x2003;(b)and wherein the hardness is 30-45 in HRC and the carbide amount in grain boundaries of the prior austenite is not more than 0.5 volume %. The marensitic stainless steel has excellent properties regarding the sulfide stress cracking resistance, the resistance to corrosive wear and the localized corrosion.

Martensitic stainless steel

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.

Steel for oil well pipe with high corrosion resistance to wet carbon dioxide and seawater, and a seamless oil well pipe

A martensitic stainless steel pipe comprises, on the weight basis, C: 0.005 to 0.2%, Si: 1% or below, Mn: 0.1 to 5%, Cr: 7 to 15%, and Ni: 0 to 8%, wherein a wall thickness t (mm) and contents of C and Cr satisfy the relationship represented by the following equation (1).

Martensitic stainless steel pipe and method for manufacturing the same

High-strength welded steel structures having excellent corrosion

The present invention provides (1) diffusion bonding methods for joining metallic materials like carbon steels or stainless steels,interposing a bonding material, such as 10 to 80 .mu.m thick Ni-based alloy with the melting point of 1150.degree. C. or lower,between base materials, heating so that the length heated at 800.degree. C. or above measures from 3 to 20 mm, in case of joining stainless steels a bonded layer, further, being heated between the both melting points, and applying the compressive stress, for example 0.5 to 2 kgf/mm.sup.2, so that a lateral expansion ratio is made within 1.0 to 1.1, and (2) a joined structure having the bonded joint formed thereby.

Method for joining metallic materials by diffusion bonding and joined

The method provides a diffusion-bonding of dual-phase stainless steel material having excellent strength and corrosion. The method includes: cold-working a material to be bonded so as to enhance the proof stress; inserting into the bonding portion an insert material; applying pressure thereto while performing shielding by mixed nitrogen/argon gas; heating the restricted bonding portion; cooling at a restricted rate; so as to form a bonded portion having the ferritic phase percentage of 30-70% by volume.

Method for bonding dual-phase stainless steel

Hydrogen sulfide corrosion resistant high-Cr and high-Ni alloys

Duplex stainless steel

A low corrosion resistant pipe 1 is jointed with a high corrosion resistant pipe 2 directly or via a coupling 3. An insulating ceramic film having a thickness of 0.4 .mu.m and a resistivity of 10.sup.8 .OMEGA. cm or more is formed on the outer and inner surfaces of the pipes 1 and 2 at a length L of 60 mm or more from the end of the pipe and on the surface which forms a space when the pipes 1 and 2 are jointed at a coverage ratio of 90% or more to less than 100%.

Galvanic corrosion resistant insulating pipe having excellent film

A martensitic stainless steel for use in oil wells has improved stability in strength and good resistance to sulfide stress corrosion cracking The steel has a chemical composition consisting essentially, on a weight basis, of: Si: not greater than 1.0%, Mn: not greater than 1.0%, Cr: 10.0-14.0%, Mo: 0.5-7.0%, Ni: 4.0-8.0%, Al: 0.001-0.1%, either Ti in an amount satisfying the following inequality (1) or Zr in an amount satisfying the following inequality (2), optionally one or both of Mg: 0.001-0.05% and Ce: 0.001-0.05%, and a balance of Fe and incidental impurities in which the contents of C, P, S, N, and V as impurities are limited to 0.05% or less, 0.04% or less, 0.005% or less, 0.05% or less, and 0.2% or less, respectively, the composition further satisfying the following inequalities (3) and (4):

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Osaka, Japan

Masakatsu Ueda