# US 5,704,997 A · Process for preparing a steel strip and novel steel strip

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- Number: US 5,704,997 A
- Document ID: US5704997A
- Status: Granted
- Kind: A
- Application number: 08/576,368
- Filed: 1995-12-21
- Granted: 1998-01-06
- Earliest claimed: 1994-12-21
- Assignees: Sollac (Societe Anonyme)
- Inventors: Jacques Ouvrard; Michel Chauvire; Jean-Claude Jouvenel
- Web page: https://patentgrep.com/patent/US5704997A

## CPC

- C21D 8/0436: {Cold rolling}
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)

## Abstract

A steel strip and method for its production.

## Claims

### Claim 1

A process for producing a steel strip comprising the steps of:
supplying an ultra-low or low carbon steel hot-rolled strip having carbon content of at most 0.01% by weight,
cold rolling the strip to obtain a blank,
annealing the blank,
cold rolling the annealed blank in at least two runs,
to provide a steel strip having a tensile strength of greater than or equal to 600 MPa.

### Claim 2 (depends on 1)

The process according to claim 1, wherein during the second cold rolling a thickness reduction of at least 35% is obtained.

### Claim 3 (depends on 1)

The process according to claim 1, wherein during the cold rolling of the annealed rough form which is done in two runs a thickness reduction of at least 25% is obtained in the first run and a thickness reduction of at least 5% is obtained during the second run.

### Claim 4 (depends on 1)

The process according to claim 1, wherein overall thickness reduction during the second cold rolling is between 38% and 47%.

### Claim 5 (depends on 1)

The process according to claim 1, wherein the annealing is done between 600.degree. C. and 700.degree. C.

### Claim 6 (depends on 1)

The process according to claim 1, wherein the annealing is done continuously.

### Claim 7 (depends on 1)

The process according to claim 1, wherein the ultra low carbon steel strip has a chemical composition by weight of:
C.ltoreq.0.006%
Si.ltoreq.0.02%
0.15%.ltoreq.Mn.ltoreq.0.35%
S.ltoreq.0.015%
P.ltoreq.0.015%
N.ltoreq.0 006%
0.02%.ltoreq.Al.ltoreq.0.06%,
the remaining part being iron and impurities coming from production.

### Claim 8

An ultra low or low carbon steel strip having:
a thickness of less than 0.2 mm,
a tensile strength greater than or equal to 600 MPa,
an ear rate, C, between 0 and -0.4,
an anisotropy coefficient, r, between 1.5 and 2.5, and
carbon content of at most 0.01% by weight.

### Claim 9 (depends on 8)

The strip according to claim 8, wherein the width of the strip is less than 0.17 mm.

### Claim 10 (depends on 8)

The strip according to claim 8, wherein the steel band has a chemical composition by weight of:
C.ltoreq.0.006%
Si.ltoreq.0.02%
0.15%.ltoreq.Mn.ltoreq.0.35%
S.ltoreq.0.015%
P.ltoreq.0.015%
N.ltoreq.0.006%
0.02%.ltoreq.Al.ltoreq.0.06%,
the remaining part being iron and impurities coming from production.

### Claim 11 (depends on 1)

The process of claim 1, wherein said steel strip comprises 0.15% to 0.35% by weight Mn.

### Claim 12 (depends on 1)

A steel strip produced by the process of claim 1, having a thickness of less than 0.2 mm.

### Claim 13 (depends on 12)

The steel strip of claim 12, comprising 0.15% to 0.35% by weight Mn.

### Claim 14 (depends on 8)

The steel strip of claim 8, comprising 0.15% to 0.35% by weight Mn.