Cold-rolled flat steel product having metal anti-corrosion layer and method for producing same

Patent metadata

Field	Value
Publication number	US-11473160-B2
Application number	US-201816956301-A
Country	US
Kind code	B2
Filing date	Dec 18, 2018
Priority date	Dec 21, 2017
Publication date	Oct 18, 2022
Grant date	Oct 18, 2022

Abstract

A method for producing a cold-rolled flat steel product coated with a metallic anticorrosion layer includes producing a steel melt containing in addition to iron and unavoidable impurities (in % by wt.): C: 0.01-0.35%, Mn: 1-4%, Si: 0.5-2.5%, Nb: to 0.1%, Ti: 0.015-0.1%, P: up to 0.1%, Al: to 0.15%, S: up to 0.01%, N: up to 0.1%, and optionally one or more elements from a group of rare earth metals. The method further includes casting the steel melt to give a preliminary product, hot-rolling the preliminary product to give a hot strip, coiling the hot strip to give a coil, annealing the hot strip, cold-rolling the annealed hot strip to give a cold-rolled flat steel product, finally annealing the cold-rolled flat steel product, and applying a metal anticorrosion layer based on zinc by electrolytic galvanization or hot dip galvanization of the cold-rolled and finally annealed flat steel product.

First claim

The invention claimed is:

1. A method of producing a cold-rolled flat steel product coated with a metallic anticorrosion layer, the method comprising:
producing a steel melt containing in addition to iron and unavoidable impurities (in % by wt.)
C: 0.01-0.35%,
Mn: 2-4%,
Si: 0.5-2.5%,
Nb: up to 0.2%,
Ti: up to 0.2%,
P: up to 0.1%,
Al: up to 1.5%,
S: up to 0.01%,
N: up to 0.1%,
Mo: up to 1%,
Cr: up to 3%,
Zr: up to 1%,
V: up to 1%,
W: up to 1%,
Co: up to 1%,
Ni: up to 2%,
B: up to 0.1%,
Cu: up to 3%, and
Ca: up to 0.015%,
casting the steel melt to give a preliminary product;
hot-rolling the preliminary product to give a hot strip, where the hot rolling end temperature is 820-1000° C.;
coiling the hot strip to give a coil, where the coiling temperature is in the range from room temperature to 750° C.;
annealing the hot strip at an annealing temperature of more than 530° C. and up to 950° C. over an annealing time of 24-50 hours;
cold-rolling the annealed hot strip to give a cold-rolled flat steel product in one or more stages with a total cold rolling level of at least 45%;
finally annealing the cold-rolled flat steel product at a final annealing temperature of 650-920° C. over an annealing time of 240-1500 seconds, the final annealing of the cold-rolled flat steel product generating an Si enrichment layer between a surface and a base material of the cold-rolled and finally annealed flat steel product, the maximum Si content of which is higher by a factor between 3 and 8 than the Si content of the base material, and which has a depth between 10 nm and 1 μm; and
applying a metal anticorrosion layer based on zinc by electrolytic galvanization or hot dip galvanization of the cold-rolled and finally annealed flat steel product.

2. The method as claimed in claim 1 , wherein the annealing of the hot strip is conducted at an annealing temperature of more than 550° C. and up to 730° C.

3. The method as claimed in claim 1 , wherein the annealing of the hot strip is conducted over an annealing time of 30-50 hours.

4. The method as claimed in claim 1 , wherein the annealing of the hot strip generates an initial Si enrichment layer between a surface and a base material of the annealed hot strip.

5. The method as claimed in claim 4 , wherein a minimum Si content of the initial Si enrichment layer is 20% or more above the Si content of the base material.

6. The method as claimed in claim 4 , wherein the initial Si enrichment layer has a depth of not more than 100 nm, 80 nm, 50 nm, 30 nm or 20 nm.

7. The method as claimed in claim 1 , wherein the final annealing of the cold-rolled flat steel product is performed over an annealing time of 240 to 900 seconds.

8. The method as claimed in claim 1 , further comprising:
through-heating or keeping the preliminary product at a preheating temperature of 1000-1300° C. between the casting and the hot rolling.

9. The method as claimed in claim 1 , further comprising:
pickling the hot strip between the coiling and the annealing of the hot strip.

10. The method as claimed in claim 1 , wherein the cold-rolled and finally annealed flat steel product is descaled with alternating current.

11. A cold-rolled, finally annealed and coated flat steel product, wherein
the flat steel product contains in addition to iron and unavoidable impurities (in % by wt.):
C: 0.01-0.35%,
Mn: 2-4%,
Si: 0.5-2.5%,
Nb: up to 0.2%,
Ti: up to 0.2%,
P: up to 0.1%
Al: up to 1.5%,
S: up to 0.01%,
N: up to 0.1%,
Mo: up to 1%,
Cr: up to 3%,
Zr: up to 1%,
V: up to 1%,
W: up to 1%,
Ni: up to 2%,
B: up to 0.1%,
Cu: up to 3%, and
Ca: up to 0.015%,
the cold-rolled, finally annealed and coated flat steel product is produced by casting the steel melt to give a preliminary product;
hot-rolling the preliminary product to give a hot strip, where the hot rolling end temperature is 820-1000° C.;
coiling the hot strip to give a coil, where the coiling temperature is in the range from room temperature to 750° C.;
annealing the hot strip at an annealing temperature of more than 530° C. and up to 950° C. over an annealing time of 24-50 hours;
cold-rolling the annealed hot strip to give a cold-rolled flat steel product in one or more stages with a total cold rolling level of at least 45%; and
finally annealing the cold-rolled flat steel product at a final annealing temperature of 650-920° C. over an annealing time of 240-1500 seconds, and wherein
the cold-rolled and finally annealed flat steel product
contains an Si enrichment layer between a surface and a base material of the cold-rolled and finally annealed flat steel product that has a depth between 10 nm and 1 μm and has a maximum Si content higher by a factor between 3 and 8 than the Si content of the base material, and
has been coated with a metallic anticorrosion layer based on zinc that has been produced by electrolytic galvanization or hot dip galvanization of the cold-rolled and finally annealed flat steel product.

12. The cold-rolled, finally annealed and coated flat steel product as claimed in claim 11 , wherein the Si enrichment layer has a depth of not more than 500 nm, 300 nm, 100 nm, 80 nm, 50 nm, 30 nm or 20 nm.

13. The cold-rolled, finally annealed and coated flat steel product as claimed in claim 11 , wherein a maximum Si content of the Si enrichment layer is higher by a factor between 4 and 6 than the Si content of the flat steel product in the region of the base material.

14. The cold-rolled, finally annealed and coated flat steel product as claimed in claim 11 , wherein
Si: 0.6-2.0%.

15. The cold-rolled, finally annealed and coated flat steel product as claimed in claim 11 , wherein
C: 0.15-0.25%.

16. The cold-rolled, finally annealed and coated flat steel product as claimed in claim 11 , wherein
Mn: 2.25-3%.

17. The cold-rolled, finally annealed and coated flat steel product as claimed in claim 11 , wherein
Nb: up to 0.1% and/or
Ti: 0.001-0.1% and/or
Al: up to 0.5%.

18. The cold-rolled, finally annealed and coated flat steel product as claimed in claim 11 , wherein
Cr: up to 0.1% and/or
Co: up to 0.1% and/or
Ni: up to 0.1% and/or
Cu: up to 0.1%.

19. The method as claimed in claim 1 , wherein finally annealing the cold-rolled flat steel product is carried out over an annealing time of 300-1500 seconds.

20. The cold-rolled, finally annealed and coated flat steel product as claimed in claim 11 , wherein finally annealing the cold-rolled flat steel product is carried out over an annealing time of 300-1500 seconds.

Assignees

• Voestalpine Stahl Gmbh

Inventors

• Mraczek Klemens
• Muhr Andreas
• Haneder Bernhard

Classifications

• C22C38/14

  containing titanium or zirconium · CPC title

• C22C38/26

  with niobium or tantalum · CPC title

• C21D9/48

  deep-drawing sheets · CPC title

• C22C38/02

  containing silicon · CPC title

• C21D8/0463

  following hot rolling · CPC title