Nippon Steel Corporation

Shohgo Aota

Takahiro Osuki

Yuhei Suzuki

Hirokazu Okada

Hiroyuki Hirata

Kana Jotoku

Mitsuru Yoshizawa

Shinnosuke Kurihara

Masahiro Seto

An austenitic stainless steel material is provided that has high creep strength even when used at an average operation temperature of more than 600 to 750° C. after welding with higher heat input, and furthermore, has excellent stress relaxation cracking resistance even after use for a long time period at the average operation temperature after welding with higher heat input. The steel material has a chemical composition which consists of, in mass %, C: 0.030% 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: 8.00 to 20.00%, N: 0.050 to 0.250%, Nb: 0.10 to 1.00%, Mo: 0.05 to 5.00%, and B: 0.0005 to 0.0100%, with the balance being Fe and impurities, and a ratio of the dissolved N amount (mass %) with respect to the content of N (mass %) in the steel material is 0.40 to 0.90.

Austenitic stainless steel material

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

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

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Tokyo, Japan

Shohgo Aota