Method for manufacturing cold-rolled, welded steel sheets, and sheets thus produced

Patent metadata

Field	Value
Publication number	US-11220723-B2
Application number	US-201716088287-A
Country	US
Kind code	B2
Filing date	Feb 27, 2017
Priority date	Mar 25, 2016
Publication date	Jan 11, 2022
Grant date	Jan 11, 2022

Abstract

A method for the manufacture of a cold-rolled steel sheet of thickness ef between 0.5 mm and 3 mm is provided. At least two hot-rolled sheets of thickness ei are supplied and butt welded, so as to create a welded joint (S1) with a direction perpendicular to the direction of hot rolling. The at least two hot-rolled sheets are pickled by continuous passage through a bath, then the assembly is cold rolled, in a step (L1), to an intermediate thickness eint, the direction of cold rolling (DL1) coinciding with the direction of hot rolling. The cold rolling is carried out with a reduction ratioɛ1=Ln⁡(eieint)such that:0.3⁢5≤Ln⁢⁢(eie⁢⁢int)Ln⁢⁢(e⁢ie⁢f)≤0.6⁢5,then the welded joint (S1) is removed so as to obtain at least two intermediate cold-rolled sheets. Then the two intermediate cold-rolled sheets are butt welded, so as to create a welded joint (S2), the direction of which is perpendicular to the direction of hot rolling, then the assembly of the at least two intermediate cold-rolled and welded sheets is cold-rolled, in a step (L2), to the final thickness ef, the direction (DL2) of the cold rolling step (L2) coinciding with the direction of rolling (DL1).

First claim

The invention claimed is:

1. A method for the manufacture of a cold-rolled steel sheet having a thickness e f between 0.5 mm and 3 mm comprising the following successive steps:
supplying at least two hot-rolled sheets having a thickness e i ;
butt welding the at least two hot-rolled sheets to create a first welded joint (S1) with a direction perpendicular to a direction of hot rolling;
pickling the at least two hot-rolled sheets by continuous passage through a bath;
cold rolling the at least two hot-rolled and welded sheets to an intermediate thickness e int , a direction of cold rolling (DL 1 ) coinciding with the direction of hot rolling, the cold rolling being carried out with a reduction ratio

ɛ
1

=

L
⁢

⁢

n
⁡

(

e
i

e
int

)

such that:

0.35
≤

L
⁢

n
⁡

(

ei

e
⁢
int

)

L
⁢

n
⁡

(

ei

e
⁢
f

)

≤
0.65

,

then
removing the first welded joint (S1) to obtain at least two intermediate cold-rolled sheets;
butt welding the at least two intermediate cold-rolled sheets to create a second welded joint (S2) having a direction perpendicular to the direction of hot rolling;
further cold rolling the at least two intermediate cold-rolled and welded sheets to a final thickness e f , a direction of the further cold rolling (DL 2 ) coinciding with the direction of rolling (DL 1 ).

2. The manufacturing method according to claim 1 , wherein

0.4
≤

ɛ
1

=

L
⁢

⁢

n
⁡

(

e
i

e
int

)

≤

0.8
.

3. The manufacturing method according to claim 1 , wherein a composition of the steel is that of a dual-phase steel having a tensile strength Rm greater than 600 MPa.

4. The manufacturing method according to claim 3 , wherein the composition of the steel includes, the contents being expressed as weight percent:
0.05%≤C≤0.17%;
1.1%≤Mn≤2.76%;
0.07%≤Si≤0.7%;
S≤0.008%;
P≤0.030%;
0.015%≤Al≤0.61%;
Mo≤0.13%;
Cr≤0.55%;
Cu<0.2%;
Ni≤0.2%;
Nb≤0.050%;
Ti≤0.045%;
V≤0.010%;
B≤0.005%;
Ca<0.030%; and
N≤0.007%;
a remainder being iron and unavoidable impurities due to processing.

5. The manufacturing method according to claim 1 , wherein a composition of the steel is that of a high-formability steel having tensile strength Rm greater than 690 MPa.

6. The manufacturing method according to claim 5 , wherein the composition of the steel includes, the contents being expressed as weight percent:
0.13%≤C≤0.3%;
1.8%≤Mn≤3.5%;
0.1%≤Si≤2%;
0.1%≤Al≤2%;
1%≤Si+Al≤2.5%,
N≤0.010%;
Ni+Cr+Mo<1%;
Ti≤0.1%;
Nb≤0.1%; and
V≤0.1%;
a remainder being iron and unavoidable impurities due to processing.

7. The manufacturing method according to claim 1 , wherein the steel is a steel for press-hardening for the manufacture of parts having a tensile strength Rm greater than 1000 MPa.

8. The manufacturing method according to claim 7 , wherein a composition of the steel includes, the contents being expressed as weight percent:
0.15%≤C≤0.5%;
0.4%≤Mn≤3%;
0.1≤Si≤1%;
Cr≤1%;
Ti≤0.2%;
Al≤0.1%;
B≤0.010%;
a remainder being iron and unavoidable impurities due to processing.

9. The manufacturing method according to claim 8 , wherein a composition of the steel includes, expressed as weight percent: 0.25%≤Nb≤2%.

10. The manufacturing method according to claim 8 , wherein a composition of the steel includes, expressed as weight percent: Nb≤0.060%.

11. The manufacturing method according to claim 1 , wherein a composition of the steel is that of a martensitic steel having tensile strength Rm between 1200 MPa and 1700 MPa.

12. The manufacturing method according to claim 11 , wherein the composition of the steel includes, the contents being expressed as weight percent:
0.10%≤C≤0.30%;
0.40%≤Mn≤2.20%;
0.18%≤Si≤0.30%;
0.010%≤Al≤0.050; and
0.0025≤B≤0.005%;
a remainder being iron and unavoidable impurities due to processing.

13. The manufacturing method according to claim 12 , wherein the composition of the steel includes at least one of, the contents being expressed as weight percent:
0.020%≤Ti≤0.035%;
Cu≤0.10%;
Ni≤0.10%; and
Cr≤0.21%.

14. The manufacturing method according to claim 1 , further comprising, after the step of removing the first welded joint and prior to the step of butt welding the at least two intermediate cold-rolled sheets to create a second welded joint, the step of:
coiling, storing and uncoiling the at least two intermediate cold-rolled sheets.

15. The manufacturing method according to claim 1 , wherein at least one of the first or second welded joints (S1, S2) is made by flash welding.

16. The manufacturing method according to claim 1 , wherein at least one of the first or second welded joints (S1, S2) is made by Laser welding.

Assignees

• Arcelormittal

Inventors

• Dechassey Emmanuel
• Silvy-Leligois Christophe
• Chicharro Herranz Francisco
• Polo Mestre Vicente
• Theyssier Marie-Christine
• Celotto Thierry
• Kaczynski Christine
• Dupuy Thomas
• Ngo Quang-Tien

Classifications

• C22C38/02

  containing silicon · CPC title

• C21D8/0236 Primary

  Cold rolling · CPC title

• C22C38/001

  containing N · CPC title

• C21D8/0226

  Hot rolling · CPC title

• B21B1/28

  by cold-rolling {, e.g. Steckel cold mill} · CPC title