Austenitic stainless steel

• US 20080107559A1
• Filed: 10/10/2007
• Published: 05/08/2008
• Est. Priority Date: 04/11/2005
• Status: Active Grant

• Current Assignee: Nippon Steel Corporation
• Original Assignee: Nippon Steel & Sumitomo Metal Corporation (Nippon Steel Corporation)
• Inventors: Otsuka, Nobuo, Nishiyama, Yoshitaka
• Granted Patent: US 9,150,947 B2
• Time in Patent Office: Days
• US Class Current: 420/38
• CPC Class Codes: C22C 38/001 containing N
• CPC Class Codes: C22C 38/005 containing rare earths, i.e. Sc, Y, Lanthanides
• CPC Class Codes: C22C 38/42 with copper
• CPC Class Codes: F28F 21/083 from stainless steel
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

An austenitic stainless steel having excellent resistance to scale peeling which can suppress peeling of a protective oxide scale which is formed on the steel surface even when the steel undergoes repeated cycles of high temperature heating and cooling and which is suitable for use in a high temperature, humidified gas environment at a high temperature and particularly at 1023 K or above has a steel composition consisting essentially of C: 0.01-0.15%, Si: 0.01-3%, Mn: 0.01-2%, Cu: 0.1-2.5%, Cr: 23-30%, Ni: 16-25%, Al: 0.005-0.20%, N: 0.001-0.40%, P: at most 0.04%, S: at most 0.01%, at least one of Y and Ln series elements: a total of 0.005-0.1%, and a balance of Fe and unavoidable impurities, with the number of inclusions containing Y and Ln series elements in the steel surface being at most 5×10⁻³/μm².

Claims

1. An austenitic stainless steel having a steel composition consisting essentially of, in mass percent, C:

0.01-0.15%, Si;

0.01-3%, Mn;

0.01-2%, Cu;

0.1-2.5%, Cr;

23-30%, Ni;

16-25%, Al;

0.005-0.20%, N;

0.001-0.40%, P;

at most 0.04%, S;

at most 0.01%, at least one rare earth element selected from Y and Ln series elements;

a total of 0.005-0. 1%, Nb, Ti, and V;

0-1.0% each, Ca and Mg;

0-0.010% each, Mo, W, Ta, Re, and Ir;

0-6% each, B, Zr, and Hf;

0-0.10% each, Co;

0-3%, Pd, Ag, Pt, and Au;

0-1% each, and a balance of Fe and unavoidable impurities, with the number of inclusions containing the above-described rare earth elements in the surface of the steel being at most 5×

10<sup>−

3</sup>/μ

m².

2. An austenitic stainless steel as set forth in claim 1 wherein the steel composition contains 0.01-1.0% each of at least one of Nb, Ti, and V.

3. An austenitic stainless steel as set forth in claim 1 wherein the steel composition contains 0.0001-0.010% each of at least one of Ca and Mg.

4. An austenitic stainless steel as set forth in claim 1 wherein the steel composition contains 0.01-6 mass % each of at least one of Mo, W. Ta, Re, and Ir.

5. An austenitic stainless steel as set forth in claim 1 wherein the steel composition contains 0.001-0.10% each of at least one of B, Zr, and Hf.

6. An austenitic stainless steel as set forth in claim 1 wherein the steel composition contains 0.01-3% of Co.

7. An austenitic stainless steel as set forth in claim 1 wherein the steel composition contains 0.005-1% each of at least one of Pd, Ag, Pt, and Au.