Method for the manufacturing of liquid metal embrittlement resistant zinc coated steel sheet

Patent metadata

Field	Value
Publication number	US-12139782-B2
Application number	US-202218091794-A
Country	US
Kind code	B2
Filing date	Dec 30, 2022
Priority date	Nov 17, 2017
Publication date	Nov 12, 2024
Grant date	Nov 12, 2024

Abstract

The present invention relates to a method for the manufacture of a coated steel sheet comprising the following successive steps: A. the coating of the steel sheet with a first coating consisting of nickel and having a thickness between 600 nm and 1400 nm, the steel sheet having the following composition in weight: 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 making up of iron and inevitable impurities resulting from the elaboration, B. the recrystallization annealing at a temperature between 820 to 1200° C., C. the coating with a second coating based on zinc not comprising nickel.

First claim

What is claimed is:

1. A coated steel sheet made from a method comprising the following successive steps: coating of a steel sheet with a first coating consisting of nickel and having a thickness between 600 nm and 950 nm, the steel sheet having the following composition in weight: 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 including: Nb≤0.5%, B≤0.010%, 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; recrystallization annealing of the coated steel sheet at a temperature between 820 to 1200° C.; and coating the steel sheet obtained in recrystallization annealing with a second coating based on zinc not comprising nickel, the coated steel sheet comprising:
a diffusion coating comprising nickel and iron formed through diffusion of nickel into a steel sheet, the diffusion coating being directly topped by a zinc based coating not comprising nickel;
the coated steel sheet having an LME crack resistance determined using 3-layer stack-up conditions of 2 cracks or less having a size above 100 μm and wherein the longest crack has a length below 450 μm.

2. The steel sheet as recited in claim 1 wherein the steel sheet comprises a decarburized layer having a depth of maximum 40 μm from the steel sheet surface.

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

4. The coated steel sheet according to claim 1 , wherein the thickness is between 600 nm and 900 nm.

5. The coated steel sheet according to claim 1 , wherein the thickness is between 650 nm and 900 nm.

6. A spot welded joint comprising:
at least two metal sheets, a first of the metal sheets being the coated steel sheet as recited in claim 1 , the joint containing 2 cracks or less having a size above 100 μm and wherein the longest crack has a length below 450 μm.

7. The spot welded joint as recited in claim 6 wherein a second of the metal sheets is a steel sheet or an aluminum sheet.

8. The spot welded joint as recited in claim 6 wherein a second of the metal sheets is a second coated steel sheet including a second diffusion coating including nickel and iron formed through diffusion of nickel into a second steel sheet, the second diffusion coating being directly topped by a second zinc based coating not comprising nickel.

9. The spot welded joint as recited in claim 6 wherein the at least two metal sheets include a third metal sheet being a steel sheet or an aluminum sheet.

Assignees

• Arcelormittal

Inventors

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

Classifications

• C23C2/022

  by heating · CPC title

• C23C2/0224

  Two or more thermal pretreatments · CPC title

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• C22C38/54

  with boron · CPC title

• C22C38/50

  with titanium or zirconium · CPC title