US2003172999A1PendingUtilityA1
Ferritic-austenitic stainless steel
Priority: Sep 27, 2000Filed: Sep 18, 2001Published: Sep 18, 2003
Est. expirySep 27, 2020(expired)· nominal 20-yr term from priority
C22C 38/58C21D 2211/001C21D 2211/005C22C 38/42C22C 38/44C22C 38/001C22C 38/002C22C 38/02C22C 38/06C22C 38/46C22C 38/48C22C 38/50C22C 38/54
40
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Claims
Abstract
A ferritic-austenitic stainless steel having a microstructure which essentially consists of 35-65 vol-% ferrite and 35-65 vol-% austenitc has a chemical composition which contains in weight-%: 0.005-0.07 C, 0.1-2.0 Si, 3-8 Mn, 19-23 Cr, 0.5-1.7 Ni, optionally Mo and/or W in a total amount of max 1.0 (Mo+W/2), optionally Cu up to max 1.0 Cu, 0.15-0.30 N, balance iron and impurities. The following conditions shall apply for the chromium and nickel equivalents: 20<Cr eq <24.5, 10<Ni eq , where (Cr eq =Cr+1.5 Si+Mo+2 Ti+0.5 Nb, and Ni eq =Ni+0.5 Mn+30 (C+N)+0.5 (Cu+Co).
Claims
exact text as granted — not AI-modified1 . A ferritic-austenitic stainless steel having a microstructure which essentially consists of 35-65 vol-% ferrite and 35-65 vol-% austenite, characteried in that the steel has a chemical composition which contains in weight-%:
0.005-0.07 C 0.1-2.0 Si 3-8 Mn 19-23 Cr 0.5-1.7 Ni optionally Mo and/or W in a total amount of max 1.0 (Mo+W/2) optionally Cu up to max 1.0 Cu 0.15-0.30 N balance iron and impurities, and that the following conditions shall apply for the ferrite- and austenite formers of the alloy, respectively, i.e. for the chromium and nickel equivalents: 20<Cr eq <24.5 10<Ni eq , where Cr eq =Cr+1.5 Si+Mo+2Ti+0.5 Nb Ni eq =Ni+0.5 Mn+30 (C+N)+0.5 (Cu+Co)
2 . A steel according to claim 1 , characteried in that it contains at least 0.01, preferably at least 0.015, suitably at least 0.02 C.
3 . A steel according to claim 1 or 2 , characteried in that it contains max 0.05, preferably max 0.04 C.
4 . A steel according to any of claims 1 - 3 , characteried in that it contains at least 0.2, preferably at least 0.35 Si.
5 . A steel according to any of claims 1 - 4 , characteried in that it contains max 1.5, preferably max 1.0 Si.
6 . A steel according to any of claims 4 and 5 , characteried in that it contains 0.35-0.80 Si.
7 . A steel according to any of claims 1 - 6 , characteried in that it contains at least 4, suitably at least 4.5 Mn.
8 . A steel according to any of claims 1 - 7 , characteried in that it contains max 6 Mn.
9 . A steel according to any of claims 7 and 8 , characteried in that it contains 4.5-5.5 Mn.
10 . A steel according to any of claims 1 - 9 , characteried in that it contains at least 20, preferably at least 20.5 Cr.
11 . A steel according to any of claims 1 - 10 , characteried in that it contains max 23, suitably max 22.5 Cr.
12 . A steel according to any of claims 10 and 11 , characteried in that it contains 21.0-22.0, preferably 21.2-21.8 Cr.
13 . A steel according to any of claims 1 - 12 , characteried in that it contains at least 0.8, preferably at least 1.1 Ni.
14 . A steel according to claim 13 , characteried in that it contains 1.35-1.70 Ni.
15 . A steel according to any of claims 1 - 14 , characteried in that it contains at least 0.1, preferably at least 0.15 Mo.
16 . A steel according to claim 15 , characteried in that it contains max 0.8 Mo, preferably max 0.65 Mo.
17 . A steel according to any of claims 15 and 16 , characteried in that it contains 0.15-0.54 (Mo+W/2).
18 . A steel according to claims 1 - 17 , characteried in that it contains at least 0.1, preferably at least 0.15, suitably at least 0.24 Cu.
19 . A steel according to claim 18 , characteried in that it contains max 0.7 Cu.
20 . A steel according to any of claims 18 and 19 , characteried in that it contains 0.25-0.54 Cu.
21 . A steel according claim 20 , characteried in that it contains at least 0.18 N.
22 . A steel according to any of claims 1 - 21 , characteried in that it contains max 0.26 N.
23 . A steel according to any of claims 21 and 22 , characteried in that it contains 0.20-0.24 N.
24 . A steel according to any of claims 1 - 23 , characteried in that it contains 0.001-0.005 B.
25 . A steel according to any of claims 1 - 24 , characteried in that it contains max 0.10 S.
26 . A steel according to claim 25 , characteried in that it contains max 0.002 S.
27 . A steel according to any of claims 1 - 26 , characteried in that the coordinates of the Cr- and Ni-equivalents lie within the frame of the area A B C D A in the Schaeffler diagram in FIG. 1, the coordinates of said points being:
Cr eq
Ni eq
A
20.8
11.8
B
23.0
15.0
C
24.0
14.5
D
23.0
10.4
28 . A steel according to claim 27 , characteried in that the coordinates of the Cr- and Ni-equivalents lie within the frame of the area D E F G H D in the Schaeffler diagram in FIG. 1, the coordinates of said points being:
Cr eq
Ni eq
D
23.0
10.4
E
22.0
11.0
F
22.0
13.5
G
22.3
14.0
H
23.0
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