High strength cold rolled steel sheet

Patent metadata

Field	Value
Publication number	US-10227683-B2
Application number	US-201314380956-A
Country	US
Kind code	B2
Filing date	Apr 2, 2013
Priority date	Mar 30, 2012
Publication date	Mar 12, 2019
Grant date	Mar 12, 2019

Abstract

The present invention relates to high strength cold rolled steel sheet suitable for applications in automobiles, construction materials and the like, specifically high strength steel excellent in formability. In particular, the invention relates to cold rolled steel sheets having a tensile strength of at least 780 MPa.

First claim

The invention claimed is:

1. A high strength cold rolled steel sheet comprising:
a) a composition consisting of the following elements, in wt. %:

C
0.1-0.3

Mn
1.4-2.7

Si
0.4-0.9

Cr
0.1-0.9

Si + Cr
0.9-1.4

Si/Cr
1-5

Si
>10 Al

Al
≤0.6

Nb
<0.1

Mo
<0.3

Ti
<0.2

V
<0.2

Cu
<0.5

Ni
<0.5

S
≤0.01

P
≤0.02

N
≤0.02

B
<0.005

Ca
<0.005

Mg
<0.005

REM
<0.005

balance Fe apart from impurities,
b) a multiphase microstructure consisting of, in vol. %

retained austenite
5-22

bainite + bainite ferritie+ tempered martensite
≤80

polygonal ferrite
>5

wherein a maximum size of the retained austenite (RA) is ≤6 μm,
c) the following mechanical properties

a tensile strength (R m )
≥780
MPa

an elongation (A 80 )
≥12
%

and optionally fulfilling the following condition

R m × A 80
≥13 000 MPa %.

2. The high strength cold rolled steel sheet according to claim 1 , wherein at least one of the following elements is in the composition, in wt. %:

C
0.13-0.25

Mn
1.5-2.5

Cr
 0.2-0.6.

3. The high strength cold rolled steel sheet according to claim 1 , wherein at least one of the following elements is in the composition, in wt. %:

Nb
 0.02-0.08

Mo
0.05-0.3

Ti
 0.02-0.08

V
0.02-0.1

Cu
0.05-0.4

Ni
0.05-0.4

B
0.0002-0.003

Ca
0.0005-0.005

Mg
0.0005-0.005

REM
 0.0005-0.005.

4. The high strength cold rolled steel sheet according to claim 1 , wherein, in wt. %:

Ti
>3.4N.

5. The high strength cold rolled steel sheet according to c

Assignees

• Voestalpine Stahl Gmbh

Inventors

• Hebesberger Thomas
• Krizan Daniel
• Paul Stefan
• Pichler Andreas

Classifications

• C21D8/0247

  characterised by the heat treatment · CPC title

• C22C38/32

  with boron · CPC title

• C21D2211/002

  Bainite · CPC title

• C22C38/46

  with vanadium · CPC title

• C22C38/50

  with titanium or zirconium · CPC title