Method for the manufacture of a galvannealed steel sheet

Patent metadata

Field	Value
Publication number	US-11578378-B2
Application number	US-201816754589-A
Country	US
Kind code	B2
Filing date	Oct 19, 2018
Priority date	Oct 24, 2017
Publication date	Feb 14, 2023
Grant date	Feb 14, 2023

Abstract

Method for the manufacture of a galvannealed steel sheet includes the following steps: A) the provision of a pre-coated steel sheet coated with a first coating comprising iron and nickel, such steel sheet having the following chemical composition in weight percent 0.10<C<0.40%, 1.5<Mn<3.0%, 0.7<Si<2.0%, 0.05<Al<1.0%, 0.75<(Si+Al)<3.0% and on a purely optional basis, one or more elements such as Nb≤0.5%, B≤0.005%, Cr≤1.0%, Mo≤0.50%, Ni≤1.0%, Ti≤0.5%, the remainder of the composition making up of iron and inevitable impurities resulting from the elaboration, B) the thermal treatment of such pre-coated steel sheet at a temperature between 600 to 1000° C., C) the hot-dip coating of the steel sheet obtained in step B) with a second coating based on zinc and D) an alloying treatment to form a galvannealed steel sheet.

First claim

The invention claimed is:

1. A method for the manufacture of a galvannealed steel sheet comprising the following steps:
providing a pre-coated steel sheet coated with a first coating comprising iron and nickel, such steel sheet having the following chemical composition in weight percent:
0.10<C<0.40%,
1.5<Mn<3.0%,
0.7<Si<2.0%,
0.05≤Al<1.0%,
0.75<(Si+Al)<3.0%, and on a purely optional basis, one or more elements such as
Nb≤0.5%,
B≤0.005%,
Cr≤1.0%,
Mo≤0.50%,
Ni≤1.0%,
Ti≤0.5%, a remainder of the composition making up of iron and inevitable impurities resulting from processing;
thermally treating the pre-coated steel sheet at a temperature between 600 to 1000° C.; hot-dip coating of the steel sheet obtained by the thermally treating step with a second coating based on zinc; and
providing an alloying treatment to form a galvannealed steel sheet, wherein the first coating includes from 10% to 75% by weight of iron.

2. The method as recited in claim 1 wherein the first coating includes from 25.0 to 65.0% by weight of iron.

3. The method as recited in claim 2 wherein the first coating includes from 40 to 60% of weight of iron.

4. The method as recited in claim 1 wherein the first coating includes from 25 to 90% by weight of nickel.

5. The method as recited in claim 4 wherein the first coating includes from 35 to 75% by weight of nickel.

6. The method as recited in claim 5 wherein the first coating includes from 40 to 60% by weight of nickel.

7. The method as recited in claim 1 wherein the first coating consists of iron and nickel.

8. The method as recited in claim 1 wherein the first coating has a thickness equal or above 0.5 μm.

9. The method as recited in claim 8 wherein the first coating has a thickness between 0.8 and 5.0 μm.

10. The method as recited in claim 9 wherein the first coating has a thickness between 1.0 and 2.0 μm.

11. The method as recited in claim 1 wherein the second coating includes above 70% by weight of zinc.

12. The method as recited in claim 11 wherein the second coating includes above 80% by weight of zinc.

13. The method as recited in claim 12 wherein the second coating includes above 85% by weight of zinc.

14. The method as recited in claim 1 wherein the second coating consists of zinc.

15. The method as recited in claim 1 wherein the thermally treating step is a continuous annealing.

16. The method as recited in claim 1 wherein the thermally treating step is performed in an atmosphere comprising from 1 to 10% of H 2 at a dew point between −30 and −60° C.

17. The method as recited in claim 1 wherein the alloying treatment is performed by heating the coated steel sheet obtained after the thermally treating step at a temperature between 460 and 550° C.

18. The method as recited in claim 1 wherein the first coating consists of iron and from 25% to 90% by weight of nickel.

Assignees

• Arcelormittal

Inventors

• Chakraborty Anirban
• Ghassemi-Armaki Hassan

Classifications

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• C23C2/0224

  Two or more thermal pretreatments · CPC title

• C21D1/76

  Adjusting the composition of the atmosphere · CPC title

• C23C2/29

  Cooling or quenching · CPC title

• C23C2/40

  Plates; Strips · CPC title