Stainless steel, cold strip produced from this steel, and method for producing a flat steel product from this steel
A stainless steel and a flat cold product produced therefrom, which can be easily produced in an economical manner. A steel according to the invention, in the cold-rolled state, has a microstructure with 5-15% by volume δ-ferrite and austenite as the remainder. It contains (in % by weight): C: 0.05-0.14%, Si: 0.1-1.0%, Mn: 4.0-12.0%, Cr: >17.5-22.0%, Ni: 1.0-4.0%, Cu: 1.0-3.0%, N: 0.03-0.2%, P: max. 0.07%, S: max. 0.01%, Mo: max. 0.5%, optionally one or more elements from the group consisting of Ti, Nb, B, V, Al, Ca, As, Sn, Sb, Pb, Bi, and H wherein Ti: max. 0.02%, Nb: max. 0.1%, B: max. 0.004%, V: max. 0.1%, Al: 0.001-0.03%, Ca: 0.0005-0.003%, As: 0.003-0.015%, Sn: 0.003-0.01%, Pb: max. 0.01%, Bi: max. 0.01%, H: max. 0.0025%, and remainder Fe and unavoidable impurities.
1. A stainless steel having a microstructure in the cold-rolled state of 8.5-13% by volume δ-ferrite and austenite as the remainder, and comprising (in % by weight):
C: 0.05-0.14%;
Si: 0.1-1.0%;
Mn: 7.5-10.5%;
Cr: >17.5-22.0%;
Ni: 1.0-4.0%;
Cu: 1.0-3.0%;
N: 0.03-0.2%;
P: max. 0.07%;
S: max. 0.01%;
Mo: max. 0.5%;
optionally one or more elements from the group consisting of Ti, Nb, B, V, Al, Ca, As, Sn, Sb, Pb, Bi, and H wherein
Ti: max. 0.02%;
Nb: max. 0.1%;
B: max. 0.004%;
V: max. 0.1%;
Al: 0.001-0.03%;
Ca: 0.0005-0.003%;
As: 0.003-0.015%;
Sn: 0.003-0.01%;
Pb: max. 0.01%;
Bi: max. 0.01%;
H: max. 0.0025%; and
remainder Fe and unavoidable impurities.
2. The stainless steel according to claim 1 , wherein for
t
=
%
Cr
+
2
%
Mo
+
1.5
%
Si
+
3
%
Al
-
5
0.3
%
Mn
+
%
Ni
+
0.5
%
Cu
+
15
(
%
C
+
%
N
)
+
2
t≦1.3,
wherein % C designates the C content, % N the N content, % Si the Si content, % Al the Al content, % Mn the Mn content, % Cr the Cr content, % Ni the Ni content, % Mo the Mo content and % Cu the Cu content of the respective steel composition.
3. The stainless steel according to claim 1 , wherein the Si content is 0.1-0.4% by weight.
4. The stainless steel according to claim 1 , wherein the Cr content is max. 20.0% by weight.
5. The stainless steel according to claim 1 , wherein the Cr content is at least 17.7% by weight.
6. The stainless steel according to claim 1 , wherein the Ni content is at least 1.5% by weight.
7. The stainless steel according to claim 1 , wherein the steel contains at least 1.5% by weight Cu.
8. The stainless steel according to claim 7 , wherein the Cu content is at least 2.0% by weight.
9. The stainless steel according to claim 1 , wherein the N content is 0.03-0.10% by weight.
10. A cold-rolled flat steel product comprising the steel according to claim 1 .
11. The cold-rolled flat steel product according to claim 10 , wherein elongation A80 is at least 35%.
12. The cold-rolled flat steel product according to claim 10 , wherein the limiting draw ratio when deep-drawing a rationally symmetrical cup is 2.00.
13. A method for producing a flat steel product, comprising steel strip or steel sheet, comprising the following working steps:
melting a stainless steel composed according to claim 1 ,
casting the molten steel in a twin-roller to form a cast strip;
hot rolling the cast strip inline following the casting of the cast strip to form a hot strip.
14. The method according to claim 13 , wherein the hot rolling takes place in a single hot rolling pass.
15. The method according to claim 13 , wherein the total degree of forming ε achieved during the hot rolling is at most 50%.
16. The method according to claim 13 , wherein the cast strip runs into the first rolling pass at a hot rolling starting temperature in the range of 1050-1200° C.
17. The method according to claim 13 , wherein the thickness of the cast strip is at most 4 mm.
18. The method according to claim 13 , further comprising cold-rolling the hot strip to form a cold strip.
19. The stainless steel according to claim 1 , wherein the Cr content is at least 18.0% by weight.