Method for manufacturing a steel sheet with a ZnAlMg coating, corresponding coated steel sheet, part and vehicle

Patent metadata

Field	Value
Publication number	US-12325893-B2
Application number	US-202118036352-A
Country	US
Kind code	B2
Filing date	Nov 15, 2021
Priority date	Nov 16, 2020
Publication date	Jun 10, 2025
Grant date	Jun 10, 2025

Abstract

A method for manufacturing a steel sheet provided with a coating included from 0.80 to 1.40 wt. % of Al, from 0.80 to 1.40 wt. % of Mg, unavoidable impurities and optionally one or more additional elements selected from Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi, the weight content of each additional element in the coating being less than 0.3%, the remainder being Zn, the outer surface of the coated steel sheet having a waviness Wa 0.8 before skin-pass of less than or equal to 0.50 μm; the coated steel sheet obtained by this method; the part obtained by deformation of a steel sheet and a land motor vehicle comprising a body, the body including the part.

First claim

What is claimed is:

1. A method for manufacturing a steel sheet provided with a coating including from 0.80 to 1.40 wt. % of Al, from 0.80 to 1.40 wt. % of Mg, unavoidable impurities and optionally one or more additional elements selected from Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi, the weight content of each additional element in the coating being less than 0.3%, a remainder being Zn, the method comprising the following successive steps:
A. providing the steel sheet,
B. cold rolling the steel sheet, at least a last rolling pass being achieved with rectified and non-etched work rolls for which the work surfaces have a roughness Ra 2.5 of less than or equal to 0.5 μm,
C. annealing of the steel sheet in a continuous annealing line,
D. depositing the coating by dipping the steel sheet in a molten bath,
E. running the coated steel sheet through a confinement zone including wiping nozzles projecting a wiping gas, through at least one outlet, on each side of the sheet along a main ejection direction (E), so that a wiping satisfies at least one of the following equations:

V
P

×

(

Z
d

)

2

≤
0.6566

(
1
)

p

O
2

≤

[

200
×

V
P

ln
[

1.523
×

V
P

×

(

Z
d

)

2

]

]

2

(
2
)

wherein:
V is the running speed of the steel sheet in front of the nozzle, V being expressed in m·s −1 ,
P is the pressure of the wiping gas in the nozzle, P being expressed in Pa,
Z is the distance between the steel sheet and the nozzle along the main ejection direction (E), Z being expressed in mm,
d is the average height of the outlet of the nozzle along the running direction(S) of the steel sheet in front of the nozzle, d being expressed in mm,
p O2 is the partial pressure in oxygen in the confinement zone;

F. solidifying the coating; and
G. skin-passing the coated steel sheet with work rolls having a roughness Ra 2.5 below 5 μm.

2. The method as recited in claim 1 wherein the skin-passing of the coated steel sheet is performed with EDT work rolls having a roughness Ra 2.5 from 1.70 to 2.95 μm.

3. The method as recited in claim 1 wherein at least one of the following equations is further satisfied:

V
P

×

(

Z
d

)

2

≤
0.4887

(
3
)

p

O
2

≤

[

200
×

V
P

ln
[

2.046
×

V
P

×

(

Z
d

)

2

]

]

2

.

(
4
)

Assignees

• Arcelormittal

Inventors

• Jacqueson Eric
• Mataigne Jean-Michel
• Agrizzi Ronqueti Larissa
• Kieffer Marine

Classifications

• C23C2/40

  Plates; Strips · CPC title

• C23C2/20 Primary

  Strips; Plates · CPC title

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• C21D8/0273

  Final recrystallisation annealing · CPC title

• C21D8/0236

  Cold rolling · CPC title