Method for the manufacturing of liquid metal embrittlement resistant galvannealed steel sheet

Patent metadata

Field	Value
Publication number	US-12134245-B2
Application number	US-202318131622-A
Country	US
Kind code	B2
Filing date	Apr 6, 2023
Priority date	May 5, 2017
Publication date	Nov 5, 2024
Grant date	Nov 5, 2024

Abstract

The present invention relates to a method for the manufacture of a galvannealed steel sheet including the steps of A.) coating of the steel sheet with a first coating consisting of nickel and having a thickness between 150 nm and 650 nm, the steel sheet having the following composition in weight percentage 0.10<C<0.40%, 1.5<Mn<3.0%, 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≤0.010%, Cr≤1.0%, Mo≤0.50%, Ni≤1.0%, Ti≤0.5%., the remainder of the composition is made up of iron and inevitable impurities resulting from the elaboration, B.) annealing of the coated steel sheet being annealed at a temperature between 600 to 1200° C., C.) coating of the steel sheet obtained in step B.) with a second coating based on zinc and D.) an alloying heat treatment to form a galvannealed steel sheet.

First claim

What is claimed is:

1. A galvannealed steel sheet obtainable from a method for the manufacture of a galvannealed steel sheet having the following successive steps:
A) coating a steel sheet with a first coating consisting of nickel and having a thickness between 150 nm and 650 nm, said steel sheet having the following composition in weight percentage:
0.10<C<0.40%,
1.5<Mn<3.0%,
0.7<Si<3.0%,
0.05<Al<1.0%,
0.75<(Si+Al)<3.0%,

and optionally one or more of the following elements:
Nb≤0.5%,

B≤0.010%,

Cr≤1.0%,

Mo≤0.50%,

Ni≤1.0%,

Ti≤0.5%,

a remainder of the composition being iron and inevitable impurities resulting from the processing;
B) annealing the coated steel sheet at a temperature between 600 to 1200° C.;
C) coating the steel sheet obtained in step B) with a second coating based on zinc; and
D) subjecting the steel sheet obtained in step C) to an alloying heat treatment to form a galvannealed steel sheet,
the galvannealed steel sheet comprising:
a first layer comprising nickel directly topped by a second layer based on zinc, the first and second layers being alloyed through diffusion such that the second alloy layer comprises from 8 to 50 wt. % of iron, from 0 to 25 wt. % of nickel, and a balance being zinc.

2. A spot welded joint of at least two metal sheets comprising:
a first metal sheet according to claim 1 ;
a second metal sheet; and
a spot welded joint connecting the first and second steel sheets, the joint containing less than 3 cracks having a size above 100 μm and a longest crack has a length below 300 μm.

3. The spot welded joint according to claim 2 , wherein the second metal sheet is a steel sheet or an aluminum sheet.

4. A spot welded joint of at least two metal sheets comprising:
a first metal sheet as recited in claim 1 ;
a second metal sheet as recited in claim 1 ; and
a spot welded joint connecting the first and second steel sheets, the joint containing less than 3 cracks having a size above 100 μm and a longest crack has a length below 300 μm.

5. A spot welded joint according to claim 4 , further comprising a third metal sheet being a steel sheet or an aluminum sheet and connected to the joint.

6. An automotive vehicle comprising:
a galvannealed steel sheet as recited in claim 1 .

7. An automotive vehicle comprising:
a spot welded joint as recited in claim 2 .

8. A spot welded joint of at least two metal sheets comprising:
at least a steel sheet as recited in claim 1 ;
a second metal sheet; and
a spot welded joint connecting the first and second steel sheets, the joint containing less than 3 cracks having a size above 100 μm and a longest crack has a length below 300 μm.

9. The spot welded joint as recited in claim 8 wherein the second metal sheet is a steel sheet or an aluminum sheet.

10. A spot welded joint of at least two metal sheets comprising:
at least a steel sheet as recited in claim 1 ;
a second metal sheet as recited in claim 1 ; and
a spot welded joint connecting the first and second steel sheets, the joint containing less than 3 cracks having a size above 100 μm and a longest crack has a length below 300 μm.

11. A spot welded joint as recited in claim 10 further comprising a third metal sheet being a steel sheet or an aluminum sheet and connected to the joint.

12. An automotive vehicle comprising:
a spot welded joint according to claim 10 .

13. The galvannealed steel sheet as recited in claim 1 wherein the steel sheet is obtained from the method.

14. The galvannealed steel of claim 1 , wherein the second layer consists of zinc.

15. The galvannealed steel of claim 1 , wherein the second layer consists of zinc, aluminum and optionally magnesium.

16. The galvannealed steel of claim 15 , wherein the second layer consists of zinc, from 0.01 to 8.0% Al, and optionally 0.2-8.0% Mg.

17. The galvannealed steel claim 1 , wherein the galvannealed steel, when spot welded with another metal sheet, has a spot welded joint containing less than 3 cracks having a size above 100 μm and a longest crack has a length below 300 μm.

Assignees

• Arcelormittal

Inventors

• Allely Christian
• Bertho Pascal
• Chakraborty Anirban
• Ghassemi-Armaki Hassan

Classifications

• C23C2/0224

  Two or more thermal pretreatments · CPC title

• C23C2/28

  Thermal after-treatment, e.g. treatment in oil bath · CPC title

• C25D5/50

  by heat-treatment · CPC title

• C25D5/12

  at least one layer being of nickel or chromium · CPC title

• C25D3/22

  of zinc · CPC title