Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Masahiro Seto

Takahiro Osuki

Kenta Yamada

Hirokazu Okada

Yoshitaka Nishiyama

Masayuki Sagara

Katsuki Tanaka

Mitsuru Yoshizawa

Yuhei Suzuki

Shohgo Aota

An austenitic stainless steel material is provided that has excellent sensitization resistance properties even after use for a long time period at an average operation temperature of 400 to 700° C. after welding with higher heat input. The steel material of the present disclosure has a chemical composition which contains, in mass %, C: 0.020% or less, Si: 1.50% or less, Mn: 2.00% or less, P: 0.045% or less, S: 0.0300% or less, Cr: 15.00 to 25.00%, Ni: 9.00 to 20.00%, N: 0.05 to 0.15%, Nb: 0.1 to 0.8%, Mo: 0.10 to 4.50%, and W: 0.01 to 1.00%, and satisfies Formula (1). The content of Nb in a residue obtained by an extraction residue method is, in mass %, 0.050 to 0.267%, and the content of Cr in the residue is, in mass %, 0.125% or less.21.9Mo+5.9W−5.0≥0  (1).

Austenitic stainless steel material and welded joint

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

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

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Tokyo, Japan

Masahiro Seto