Method for producing a press-hardened laser welded steel part and press-hardened laser welded steel part

Patent metadata

Field	Value
Publication number	US-11911847-B2
Application number	US-201916976392-A
Country	US
Kind code	B2
Filing date	Feb 26, 2019
Priority date	Feb 27, 2018
Publication date	Feb 27, 2024
Grant date	Feb 27, 2024

Abstract

A method for producing a part includes providing a first and a second precoated sheet (1,2), butt welding the first and second precoated sheets (1) to obtain a blank (15), and heating the blank (15) to a heat treatment temperature at least 10° C. lower than the full austenitization temperature of the weld joint (22) and at least 15° C. higher than a minimum temperature Tmin:Tmin⁡(°⁢⁢C.)=AC⁢⁢3⁢(WJ)-αICmax100⁢(Ac⁢⁢3⁢(WJ)-673-40×Al).whereAc3(WJ) is the full austenitization temperature of the weld joint (22)αICmax=(1-(1+ρ)⁢(max⁡(1⁢;⁢ρ)⁢Ts2-350)(1-β)⁢(ρ⁢⁢Ts2+Ts1)+β⁡(1+ρ)⁢(3130⁢⁢CFW+750)-350×(1+ρ))×100,whereTS1 and TS2 are the ultimate tensile strengths of the strongest and the weakest substrate after press-hardeningCFW is the carbon content of the filler materialβ is the proportion of filler materialρ is the ratio between the thicknesses of the weakest and the strongest substrateThe method also includes holding the blank (15) at the heat treatment temperature for a time between 2 and 10 minutes; and press-forming the blank (15) into a part and cooling.

First claim

What is claimed is:

1. A method for producing a press-hardened laser welded steel part comprising the following successive steps:
providing a first precoated steel sheet and a second precoated steel sheet, each of the first and second precoated steel sheets comprising a steel substrate, at least one of the first and second precoated steel sheets having, on at least one of its main faces, an aluminum-containing precoating comprising at least 50% by weight of aluminum,
the first precoated steel sheet having a first thickness and the second precoated steel sheet having a second thickness,
the steel substrate of the first precoated steel sheet having, after press-hardening, an ultimate tensile strength greater than the ultimate tensile strength, after press-hardening, of the steel substrate of the second precoated steel sheet, and
the product of the first thickness by the ultimate tensile strength, after press-hardening, of the first precoated steel sheet being greater than the product of the second thickness by the ultimate tensile strength, after press-hardening, of the second precoated steel sheet; then
butt welding the first precoated steel sheet and the second precoated steel sheet using laser welding so as to obtain a weld joint between the first and second precoated steel sheets thereby obtaining a welded blank, the butt welding step optionally including using a filler material;
heating the welded blank to a heat treatment temperature, the heat treatment temperature being at least 10° C. lower than the full austenitization temperature of the weld joint and at least 15° C. higher than a minimum temperature T min , where

T
min

(

°
⁢

C
.

)

=

A
⁢
C
⁢
3
⁢

(
WJ
)

-

α
IC
max

1
⁢
0
⁢
0

⁢

(

A
⁢
c
⁢
3
⁢

(
WJ
)

-

6
⁢
7
⁢
3

-

40
×
Al

)

,

where
Ac3(WJ) is the full austenitization temperature of the weld joint, in ° C. and Al is the content of aluminum in the weld joint, in wt. %,
and α IC max is the maximum intercritical ferrite content of the weld joint, calculated using the following formula:

α
IC
max

=

(

1
-

(

1
+
ρ

)

⁢

(

max
⁡
(

1
;
ρ

)

⁢

Ts
2

-

3
⁢
5
⁢
0

)

(

1
-
β

)

⁢

(

ρ
⁢

Ts
2

+

T
⁢

s
1

)

+

β
⁡
(

1
+
ρ

)

⁢

(

3
⁢
130

Assignees

• Arcelormittal

Inventors

• Schmit Francis
• Poirier Maria
• Gaied Sadok

Classifications

• C22C38/48

  with niobium or tantalum · CPC title

• B23K26/322 Primary

  involving coated metal parts (using absorbing layers on the workpiece B23K26/18) · CPC title

• B23K26/123

  in an atmosphere of particular gases · CPC title

• B23K26/32

  taking account of the properties of the material involved · CPC title

• B23K26/323

  involving parts made of dissimilar metallic material · CPC title