Method for the manufacture of a coated steel sheet

Patent metadata

Field	Value
Publication number	US-11680331-B2
Application number	US-201816754011-A
Country	US
Kind code	B2
Filing date	Oct 19, 2018
Priority date	Oct 24, 2017
Publication date	Jun 20, 2023
Grant date	Jun 20, 2023

Abstract

A steel sheet coated with a coating comprising from 10 to 40% of nickel, the balance being zinc, such steel sheet having a microstructure comprising from 1 to 50% of residual austenite, from 1 to 60% of martensite and optionally at least one element chosen from: bainite, ferrite, cementite and pearlite, and the following chemical composition in weight: 0.10<C<0.50%, 1.0<Mn<5.0%, 0.7<Si<3.0%, 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.

First claim

What is claimed is:

1. A steel sheet comprising:
a steel substrate; and
a coating on the steel substrate, the coating comprising from 10 to 40% of nickel, a balance being zinc,
the steel substrate having a microstructure comprising from 1 to 50% of residual austenite, from 1 to 60% of martensite, from 10 to 40% of bainite, such bainite comprising from 10 to 20% of lower bainite, from 0 to 15% of upper bainite and from 0 to 5% of carbide free bainite, and optionally at least one element chosen from: ferrite, cementite and pearlite, and the following chemical composition in weight:
0.10<C<0.50%,
1.0<Mn<5.0%,
0.7<Si<3.0%,
0.05<Al<1.0%,
0.75<(Si+Al)<3.0%,

and on a purely optional basis, one or more elements:
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.

2. The steel sheet as recited in claim 1 wherein the coating includes from 10 to 30% by weight of nickel.

3. The steel sheet as recited in claim 2 wherein the coating includes from 10 to 20% by weight of nickel.

4. The steel sheet as recited in claim 3 wherein the coating consists of zinc and nickel.

5. The steel sheet as recited in claim 1 wherein the coating is directly in contact with the steel sheet.

6. The steel sheet as recited in claim 1 wherein the coating has a thickness between 5 to 15 μm.

7. The steel sheet as recited in claim 6 wherein the coating has a thickness between 5 to 10 μm.

8. The steel sheet as recited in claim 1 wherein the steel sheet microstructure includes from 5 to 25% of residual austenite.

9. The steel sheet as recited in claim 1 wherein the 1 to 60% of martensite includes from 1 to 60% of tempered martensite.

10. The steel sheet as recited in claim 1 wherein the steel sheet microstructure includes from 1 to 25% of ferrite.

11. The steel sheet as recited in claim 1 wherein the 1 to 60% of martensite includes from 1 to 15% of untempered martensite.

12. A spot welded joint of at least two metal sheets comprising: the steel sheet as recited in claim 1 and a second metal sheet, the joint containing less than 2 cracks having a size above 100 μm and wherein the longest crack has a length below 250 μm.

13. The spot welded joint as recited in claim 12 wherein the second metal sheet is a steel sheet or an aluminum sheet.

14. The spot welded joint as recited in claim 12 wherein the second metal sheet includes a second steel substrate; and a second coating on the second steel substrate, the second coating comprising from 10 to 40% of nickel, a balance being zinc, the second steel substrate having a microstructure comprising from 1 to 50% of residual austenite, from 1 to 60% of martensite and optionally at least one element chosen from: bainite, ferrite, cementite and pearlite, and the following chemical composition in weight:
0.10<C<0.50%,
1.0<Mn<5.0%,
0.7<Si<3.0%,
0.05<Al<1.0%,
0.75<(Si+Al)<3.0%,
and on a purely optional basis, one or more elements:
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.

15. The spot welded joint as recited in claim 12 further comprising a third metal sheet being a steel sheet or an aluminum sheet.

16. The spot welded joint as recited in claim 12 wherein the joint contains no cracks having a size above 100 μm.

17. An automobile vehicle part comprising the steel sheet as recited in claim 1 .

18. A method for the manufacture of a coated steel sheet according to claim 1 , comprising the following steps:
providing an annealed steel substrate having the following chemical composition in weight:
0.10<C<0.50%,
1.0<Mn<5.0%,
0.7<Si<3.0%,
0.05<Al<1.0%,
0.75<(Si+Al)<3.0%,

and on a purely optional basis, one or more elements:
Nb≤0.5%,

B≤0.005%,

Cr≤1.0%,

Mo≤0.50%,

Ni≤1.0%,

Ti≤0.5%,

such steel sheet being annealed at a temperature between 600 to 1200° C.;
the steel substrate having a microstructure comprising from 1 to 50% of residual austenite, from 1 to 60% of martensite, from 10 to 40% of bainite, such bainite comprising from 10 to 20% of lower bainite, from 0 to 15% of upper bainite and from 0 to 5% of carbide free bainite, and optionally at least one element chosen from: ferrite, cementite and pearlite; and
coating the annealed steel substrate with a coating comprising from 1 to 40% of nickel, a balance being zinc.

19. A spot welded joint of at least two metal sheets comprising: the coated steel sheet obtained from the method as recited in claim 18 and a second metal sheet, the joint containing less than 2 cracks having a size above 100 μm and wherein the longest crack has a length below 250 μm.

20. The method as recited in claim 18 wherein the steel substrate is annealed in a continuous annealing.

21. The method as recited in claim 18 wherein the annealing is performed in an atmosphere comprising from 1 to 30% of H 2 at a dew point between −10 and −60° C.

22. The method as recited in claim 18 wherein the coating is deposited by vacuum deposition or an electro-plating method.

23. The method as recited in claim 22 wherein the coating is deposited by the electro-plating method.

24. An automobile vehicle part comprising a coated steel sheet obtained by the method as recited in claim 18 .

25. The steel sheet as recited in claim 1 wherein the steel sheet microstructure comprises from 5 to 25% of residual austenite and from 1 to 25% of ferrite.

Assignees

• Arcelormittal

Inventors

• Chakraborty Anirban
• Bertho Pascal
• Ghassemi-Armaki Hassan
• Allely Christian
• Machado Amorim Tiago

Classifications

• B32B7/05

  the layers not being connected over the whole surface, e.g. discontinuous connection or patterned connection (using interposed adhesives or bonding materials applied in spaced arrangements B32B7/14) · CPC title

• C21D6/002

  containing Cr (C21D6/004 takes precedence) · CPC title

• C22C38/06

  containing aluminium · CPC title

• B23K11/11

  Spot welding · CPC title

• B32B2250/02

  2 layers · CPC title