Nippon Steel Sumitomo Metal Corporation

Akihiro Uehira

Yasuhiro Masaki

Manabu Kanzaki

Yasuyoshi Hidaka

Osamu Miyahara

Masahito Tasaka

Shoji Kinomura

There is provided a Cr-containing austenitic alloy having a chromium oxide film with a thickness of 5 nm or larger on the surface, wherein the content of Mn in a base metal is, by mass percent, less than 0.1%. The chemical composition of the base metal desirably consists of, by mass percent, C: 0.15% or less, Si: 1.00% or less, Mn: less than 0.1%, P: 0.030% or less, S: 0.030% or less, Cr: 10.0 to 40.0%, Ni: 8.0 to 80.0%, Ti: 0.5% or less, Cu: 0.6% or less, Al: 0.5% or less, and N: 0.20% or less, the balance being Fe and impurities.

Cr-containing austenitic alloy and method for producing the same

There is provided a chromium-containing austenitic alloy wherein at least one surface of the surfaces of the alloy has a continuous chromium oxide film with a thickness of 5 nm or more and less than 50 nm. A maximum current density determined by a critical passivation current density method is 0.1 &#x3bc;A/cmor less when the chromium oxide film is continuous. A chemical composition of a base metal preferably consists of, by mass percent, C: 0.15% or less, Si: 1.00% or less, Mn: 2.0% or less, P: 0.030% or less, S: 0.030% or less, Cr: 10.0 to 40.0%, Ni: 8.0 to 80.0%, Ti: 0.5% or less, Cu: 0.6% or less, Al: 0.5% or less, and N: 0.20% or less, the balance being Fe and impurities.

Chromium-containing austenitic alloy

There is provided a Cr-containing austenitic alloy tube, wherein a chromium oxide film with a thickness of 0.05 to 1.5 &#x3bc;m having the relationship defined by Formula (i) is formed on the inner surface of the tube, wherein the average concentration of C in the depth range of 5 to 10 &#x3bc;m from the inner surface is lower than the concentration of C in a base metal;0.4&#x2266;&#x3b4;1/&#x3b4;2&#x2266;2.5&#x2003;&#x2003;(i)wherein &#x3b4;1 and &#x3b4;2 are thicknesses (&#x3bc;m) of the chromium oxide film at both ends of tube, respectively.

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Tokyo, Japan

Akihiro Uehira