Sumitomo Metal Industries, Inc.

Sumikin Welding Industries Ltd.

Yuichi Komizo

Kunio Kondo

Masaaki Igarashi

Kazuhiro Ogawa

Hiroyuki Hirata

Takahiro Kushida

Mitsuru Yoshizawa

Junichiro Murayama

Yoshiaki Murata

A martensitic stainless steel provided includes C: 0.01-0.1% and Cr: 9-15%, and the retained austenite phase has a thickness not more than 100 nm in such a manner that the X-ray integral intensities of 111&#x3b3; and 110&#x3b1; satisfy the following formula (a):0.005&#x2266;111&#x3b3;/(111&#x3b3;+110&#x3b1;)&#x2266;0.05&#x2003;&#x2003;(a)Such a metal structure can be obtained by the following procedure: the steel is heated at a temperature of the Acpoint or more, and then cooled from 800&#xb0; C. to 400&#xb0; C. at a cooling rate of not less than 0.08&#xb0; C./sec and further cooled down to 150&#xb0; C. at a cooling rate of not more than 1&#xb0; C./sec. The martensitic stainless steel according to the present invention has a relatively high carbon content and a greater toughness in spite of a high mechanical strength, and further exhibits an excellent corrosion resistance, so that it is particularly effective as the material for constructing a deep oil well.

Martensitic stainless steel and method for manufacturing same

A martensitic stainless steel having a C content of 0.01 to 0.1 mass %, a Cr content of 9 to 15 mass % and a N content of not more than 0.1 mass %, wherein the maximum length of the carbides in the steel is 10 to 200 nm in the direction of the minor axis, or wherein the ratio of the average Cr concentration [Cr] to the average Fe concentration [Fe] in carbides in the steel ([Cr]/[Fe]) is not more than 0.4, or wherein the content of MCtype carbides is not more than 1 volume %, the content of MC type carbides is 0.01 to 1.5 volume % and the content of MN type or MN type nitrides is not more than 0.3 volume % is provided. This stainless steel has a high toughness in spite of both a relatively more C content and a high strength, thereby providing a, wide applicability to pipe material for oil wells containing carbon dioxide and a small amount of hydrogen sulfide, in particular for oil wells having a much greater depth.

Martensitic stainless steel

A welding material for use in a consumable or non-consumable electrode welding of stainless steels, capable of forming a weld metal with excellent corrosion resistance and mechanical properties, being drawn into a welding wire easily. The welding material is a composite welding wire composed of a steel shell and a filler material enveloped by the said steel shell and not containing slag forming agent. The welding material, as a whole, has the chemical composition as follows (by weight %): Not more than 0.3% C, not more than 1.0% Si, not more than 1.5% Mn, not more than 0.04% P, not more than 0.01% S, not more than 0.5% Al, 8.0 to 10.0% Mo, 22.0 to 26.0% Cr, 2.0 to 5.0% Mo, 0.12 to 0.24% N, not more than 3.0% Co, not more than 5.0% W, not more than 2.0% Cu, not more than 1.5% V and the equivalent PREW of the welding material is not smaller than 42.0 and ferrite volume index Ph of the welding material is 0.12 to 0.25, in which PREW and Ph are defined by the following formula 1 and formula 2 respectively: ##EQU1##

Welding material for stainless steels

A diffusion bonding method for corrosion resistant materials comprises: disposing an insert material having a melting point of at most 1150 degrees C. and a thickness of 10-80 micrometers between the bonding interfaces of two members to be joined, the insert comprising, by weight %,

Diffusion bonding method for corrosion-resistant materials

A titanium-clad steel and a method for its manufacture are disclosed. The titanium-clad steel comprises a steel base metal, a nickel insert which is bonded to the steel base metal, a low-carbon ferrous metal insert which contains at most 0.01 weight % of carbon and which is bonded to the nickel insert, and cladding of a titanium-based metal which is bonded to the low-carbon ferrous metal insert. A manufacturing method therefor comprises preparing a 4-layer clad assembly comprising the above materials, sealing the outer seams of the clad assembly by shielded arc welding, performing degassing treatment on at least the confronting surfaces of the inserts, heating the clad assembly to a temperature of 500.degree.-1050.degree. C., and performing hot rolling. The resulting titanium-clad steel has a high bonding strength.

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Nishinomiya, Japan

Yuichi Komizo