Nippon Steel Sumitomo Metal Corporation

Sumitomo Metal Industries, Inc.

Nippon Steel Corporation

Mitsuru Yoshizawa

Hiroyuki Hirata

Hirokazu Okada

Hiroyuki Semba

Atsuro Iseda

Kunio Kondo

Masaaki Igarashi

Kazuhiro Ogawa

Yasuyoshi Hidaka

Junichi Higuchi

Yoshitaka Nishiyama

Takahiro Osuki

Sumio Iida

Kana Jotoku

Toshihide Ono

Hidenori Ogawa

Masaaki Terunuma

Katsuki Tanaka

Yuichi Komizo

Masahiro Seto

Tomoaki Hamaguchi

Shohgo Aota

Koji Nakaike

Kana Joutoku

There is provided a duplex stainless steel tube including a chemical composition consisting of, in mass %, C: 0.008 to 0.030%, Si: 0.10 to 0.70%, Mn: 0.80 to 2.60%, P: 0.030% or less, S: 0.0001 to 0.0050%, O: 0.0004 to 0.0150%, Sn: 0.0001% or more to less than 0.0100%, Cu: 0.10 to 2.50%, Ni: more than 2.50 to 5.50% or less, Cr: 21.5 to 25.5%, Mo: 0.10 to 0.50%, N: 0.050 to 0.200%, Al: 0.200% or less, and optional elements, with the balance: Fe and impurities, wherein 4S+8O+Sn is 0.0040 to 0.0900, and 4S+Sn is 0.0180 or less.

Duplex stainless steel tube and welded joint

A Ni-based heat resistant alloy as pipe, plate, rod, forgings and the like consists of C&#x2266;0.15%, Si&#x2266;2%, Mn&#x2266;3%, P&#x2266;0.03%, S&#x2266;0.01%, Cr: 15% or more and less than 28%, Mo: 3 to 15%, Co: more than 5% and not more than 25%, Al: 0.2 to 2%, Ti: 0.2% to 3%, Nd: fn to 0.08%, and O&#x2266;0.4Nd, further containing, as necessary, at least one kind of Nb, W, B, Zr, Hf, Mg, Ca, Y, La, Ce, Ta, Re and Fe of specific amounts, the balance being Ni and impurities, wherein, fn=1.7&#xd7;10d+0.05{(Al/26.98)+(Ti/47.88)+(Nb/92.91)}. In the formula, d denotes an average grain size (&#x3bc;m), and each element symbol denotes the content (mass %) of that element. If the alloy contains W, Mo+(W/2)&#x2266;15% holds. The alloy has improved ductility after long-term use at high temperatures, and cracking due to welding can be avoided.

Ni-based heat resistant alloy

There is provided an austenitic stainless steel pipe excellent in steam oxidation resistance. The austenitic stainless steel pipe excellent in steam oxidation resistance contains, by mass percent, 14 to 28% of Cr and 6 to 30% of Ni, and is configured so that a region satisfying the following Formula exists in a metal structure at a depth of 5 to 20 &#x3bc;m from the inner surface of the steel pipe:(&#x3b1;/&#x3b2;)&#xd7;&#x3b4;/&#x3b5;&#xd7;100&#x2267;0.3where the meanings of symbols in the above Formula are as follows:&#x3b1;: sum total of the number of pixels of digital image in region in which orientation difference of adjacent crystals detected by electron backscattering pattern is 5 to 50 degrees&#x3b2;: the number of total pixels of digital image in region of measurement using electron backscattering pattern&#x3b5;: analysis pitch width of electron backscattering pattern (&#x3bc;m)&#x3b4;: grain boundary width (&#x3bc;m).

Austenitic stainless steel pipe excellent in steam oxidation resistance and manufacturing method therefor

An austenitic heat resistant alloy includes, by mass percent, C: 0.15% or less, Si: 2% or less, Mn: 3% or less, Ni: 40 to 60%, Co: 10.14 to 25%, Cr: 15% or more and less than 28%, either one or both of Mo: 12% or less and W: less than 0.05%, the total content thereof being 0.1 to 12%, Nd: 0.001 to 0.1%, B: 0.0005 to 0.006%, N: 0.03% or less, O: 0.03% or less, at least one selected from Al: 1.36% or less, Ti: 3% or less, and Nb: 3% or less, and the balance being Fe and impurities. The contents of P and S in the impurities are P: 0.03% or less and S: 0.01% or less. The alloy satisfies 1&#x2266;4&#xd7;Al+2&#xd7;Ti+Nb&#x2266;12 and P+0.2&#xd7;Cr&#xd7;B&#x2266;0.035, where an element in the Formulas represents the content by mass percent.

Austenitic heat resistant alloy

A method for surface treating a mandrel bar used for hot rolling of high-alloy seamless steel pipe is provided. The method includes heat treating the mandrel bar to develop a scale, and after heat treatment, rolling ordinary steel comprising 8% or less of chromium for at least 50 passes. This achieves a mandrel bar for rolling high-alloy steel possessing both durability and superior resistance to seizure.

Mandrel bar for high-alloy rolling, method for surface treating a mandrel bar, method for producing mandrel bar, and method for operating seamless pipe mill

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

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Amagasaki, Japan

Mitsuru Yoshizawa