Method for producing a flat steel product made of a manganese-containing steel, and such a flat steel product

Patent metadata

Field	Value
Publication number	US-11261503-B2
Application number	US-201716333947-A
Country	US
Kind code	B2
Filing date	Sep 13, 2017
Priority date	Sep 16, 2016
Publication date	Mar 1, 2022
Grant date	Mar 1, 2022

Abstract

The invention relates to a method for producing a flat steel product made of a medium manganese steel having a TRIP/TWIP effect. The aim of the invention is to achieve an improvement in the yield strength when a sufficient residual deformability of the produced flat steel product is obtained. This aim is achieved by the following steps: cold rolling a hot or cold strip, annealing the cold-rolled hot or cold strip at 500 to 840° C. for 1 minute to 24 hours, temper rolling or finishing the annealed hot or cold strip to form a flat steel product having a degree of deformability between 0.3% and 60%. The invention further relates to a flat steel product produced according to said method and to a use thereof.

First claim

What is claimed is:

1. A method for producing a flat steel product of medium manganese steel having a TRIP/TWIP effect, said method comprising:
cold rolling a hot or cold strip;
annealing the cold-rolled hot or cold strip at a temperature of 500 to 840° C. for 1 min to 24 h;
temper rolling the annealed hot or cold strip to form a flat steel product having a degree of deformation between 10 to 35%,
wherein the annealed hot or cold strip is temper rolled to form the flat steel product until the flat steel product has a yield strength which is increased by at least 50 MPa compared with prior to the temper rolling; and
wherein the annealed hot or cold strip is temper rolled to form the flat steel product until a metastable austenite thereof is partially converted into deformation twins (TWIP effect) and martensite (TRIP effect), wherein at least a portion of 3% of the metastable austenite is converted into martensite and at least a portion of 10% of the metastable austenite is retained as a face-centred cubic phase.

2. The method of claim 1 , wherein the hot or cold strip is cold roiled in a first rolling pass at a temperature of the hot or cold strip of 60° C. to below AC 3 .

3. The method of claim 2 , further comprising intermediately heating or intermediately cooling the hot or cold strip between rolling passes following the first rolling pass to a temperature of 60° C. to below Ac 3 .

4. The method of claim 1 , wherein the annealed hot or cold strip is temper rolled or skin pass rolled at a temperature of 0 to 400° C.

5. The method of claim 1 , wherein the flat steel product has a tensile strength of greater than 1300 MPa and an elongation at fracture A80 of greater than 3%.

6. The method of claim 1 , wherein the flat steel product comprises, in wt. %:
C: 0.0005 to 0.9,
Mn: 4 to 12,
with the remainder being iron including unavoidable steel-associated elements.

7. The method of claim 6 , further comprising adding to the flat steel product by alloying, in wt. %:
Al: 0 to 10,
Si: 0 to 6,
Cr: 0 to 6,
Nb: 0 to 1,
V: 0 to 1.5,
Ti: 0 to 1.5,
Mo: 0 to 3,
Sn: 0 to 0.5,
Cu: 0 to 3,
W: 0 to 5,
Co: 0 to 8,
Zr: 0 to 0.5,
Ta: 0 to 0.5,
Te: 0 to 0.5,
B: 0 to 0:15,
P: less than 0.1,
S: less than 0.1,
N: less than 0.1.

8. The method of claim 6 , further comprising adding to the flat steel product by alloying, in wt. %:
Al: 0.05 to 5,
Si: 0.05 to 3,
Cr: 0.1 to 4,
Nb: 0.005 to 0.4,
V: 0.005 to 0.6,
Ti: 0.005 to 0.6,
Mo: 0.005 to 1.5,
Sn: less than 0.2,
Cu: less than 0.5,
W: 0.01 to 3,
Co: 0.01 to 5,
Zr: 0.005 to 0.3,
Ta: 0.005 to 0.3,
Te: 0.005 to 0.3,
B: 0.001 to 0.08,
P: less than 0.04,
5: less than 0.02,
N: less than 0.05.

9. The method of claim 6 , further comprising adding to the flat steel product by alloying, in wt. %:
Al: greater than 0.5 less than or equal to 3,
Si: 0.1 to 1.5,
Cr: greater than 0.5 less than or equal to 2.5,
Nb: 0.01 to 0.1,
V: 0.01 to 0.3,
Ti: 0.01 to 0.3,
Mo: 0.01 to 0.6,
Sn: less than 0.05,
Cu: less than 0.1,
W: 0.2 to 1.5,
Co: 0.3 to 2,
Zr: 0.01 to 0.2,
Ta: 0.01 to 0.1,
Te: 0.01 to 0.1,
B: 0.002 to 0.01,
P: less than 0.04,
S: less than 0.02,
N: less than 0.05.

10. The method of claim 1 , further comprising coating the flat steel product metallically, inorganically or organically.

11. The method of claim 1 , wherein the hot or cold strip is cold rolled in a first rolling pass at a temperature of the hot or cold strip of 60° C. to below 450° C.

12. The method of claim 11 , further comprising intermediately heating or intermediately cooling the hot or cold strip between rolling passes following the first rolling pass to a temperature of 60° C. to below 450° C.

13. The method of claim 1 , wherein the flat steel product comprises, in wt. %:
C: 0.05 to 0.35,
Mn: greater than 5 to less than 10,
with the remainder being iron including unavoidable steel-associated elements.

Assignees

• Salzgitter Flachstahl Gmbh

Inventors

• Palzer Peter
• Evertz Thomas
• Otto Manuel
• Köhler Kai

Classifications

• C21D8/02 Primary

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C22C38/18

  containing chromium · CPC title

• C21D8/0268 Primary

  between cold rolling steps · CPC title

• C22C38/28

  with titanium or zirconium · CPC title

• C22C38/38

  with more than 1.5% by weight of manganese · CPC title