# US RE44,940 E1 · Coated hot- and cold-rolled steel sheet comprising a very high resistance after thermal treatment

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- Number: US RE44,940 E1
- Document ID: USRE44940E1
- Status: Granted
- Kind: E1
- Application number: 13/863,100
- Filed: 2013-04-15
- Granted: 2014-06-10
- Earliest claimed: 1998-07-19
- Assignees: ArcelorMittal France; ArcelorMittal Atlantique et Lorraine
- Applicants: Arcelormittal France; Arcelormittal Atlantique Et Lorraine
- Inventors: Jean-Pierre Laurent; Jean-Paul Hennechart; Dominique Spehner; Jacques Devroc
- Web page: https://patentgrep.com/patent/USRE44940E1

## Abstract

Hot-rolled steel sheet which then can be cold-rolled, coated, the steel in the sheet having the following composition by weight: 0.15%<carbon<0.5% 0.5%<manganese<3% 0.1%<silicon<0.5% 0.01%<chromium<1% titanium<0.2% aluminum<0.1% phosphorus<0.1% sulfur<0.05% 0.0005%<boron<0.08%, the remainder being iron and impurities inherent in processing, the shoot ensuring a very high mechanical resistance after thermal treatment and the aluminum-based coating ensuring a high resistance to corrosion.

## Claims

### Claim 1

A hot-rolled coated steel sheet comprising a hot-rolled steel sheet coated with an aluminum or aluminum alloy coating, wherein the steel in the sheet comprises the following composition by weight:
0.15%<carbon<0.5%
0.5%<manganese<3%
0.1%<silicon<0.5%
0.01% <chromium<1%
titanium<0.2%
aluminum<0.1%
phosphorus<0.1%
sulfur<0.05%
0.0005%<boron<0.08%, the remainder being iron and impurities inherent in processing, and the steel sheet has a very high mechanical resistance after thermal treatment and the aluminum or aluminum alloy coating provides a high resistance to corrosion of the steel sheet.

### Claim 2 (depends on 1)

The coated steel sheet according to claim 1, wherein the composition by weight of the sheet further comprises the following:
0.20%<carbon<0.5%
0.8%<manganese<1.5%
0.1%<silicon<0.35%
0.01%<chromium<1%
titanium<0.1%
aluminum<0.1%
phosphorus<0.05%
sulfur 0.03%
0.0005%<boron<0.01%, the remainder being iron and impurities inherent in processing.

### Claim 3 (depends on 2)

A heat treated coated steel sheet prepared by subjecting the coated steel sheet according to claim 2, to an increase in temperature at a speed in excess of 600° C./second.

### Claim 4 (depends on 2)

A process for producing a casting comprising
shaping the coated steel sheet of claim 2,
subjecting the shaped coated steel sheet to an increase in temperature at a speed in excess of 5° C./sec.

### Claim 5 (depends on 1)

The coated steel sheet according to claim 1, wherein the ratio of titanium to nitrogen in the steel sheet in weight % is in excess of 3.42.

### Claim 6 (depends on 5)

A process for producing a casting comprising
shaping the coated steel sheet of claim 5,
subjecting the shaped coated steel sheet to an increase in temperature at a speed in excess of 5° C./sec.

### Claim 7 (depends on 1)

The coated steel sheet according to claim 1, wherein the aluminum or aluminum alloy coating comprises from 9% to 10% silicon by weight, from 2% to 3.5% iron by weight, the remainder being aluminum.

### Claim 8 (depends on 7)

A process for producing a casting comprising
shaping the coated steel sheet of claim 7,
subjecting the shaped coated steel sheet to an increase in temperature at a speed in excess of 5° C./sec.

### Claim 9 (depends on 1)

The coated steel sheet according to claim 1, wherein the coating comprises from 2% to 4% iron by weight, the remainder being aluminum.

### Claim 10 (depends on 9)

A process for producing a casting comprising
shaping the coated steel sheet of claim 9,
subjecting the shaped coated steel sheet to an increase in temperature at a speed in excess of 5° C./sec.

### Claim 11 (depends on 1)

A process for producing a casting comprising
shaping the coated steel sheet of claim 1,
subjecting the shaped coated steel sheet to an increase in temperature at a speed in excess of 5° C./second.

### Claim 12 (depends on 11)

The process according to claim 11, wherein the casting is heated to a temperature in excess of 750° C.

### Claim 13 (depends on 1)

A heat treated coated steel sheet prepared by subjecting the coated steel sheet according to claim 1 to an increase in temperature at a speed in excess of 600° C./second.

### Claim 14 (depends on 13)

A land motor vehicle comprising the heat treated coated steel of claim 13.

### Claim 15 (depends on 1)

A land motor vehicle comprising the coated steel sheet of claim 1.

### Claim 16 (depends on 1)

A heat treated coated steel sheet prepared by subjecting the coated steel sheet according to claim 1 to a temperature in excess of 750° C.

### Claim 17

A hot-rolled coated steel sheet comprising a hot-rolled steel sheet coated with an aluminum or aluminum alloy coating, wherein said coated steel sheet is in the form of a delivery coil and the steel in the sheet comprises the following composition by weight:
0.15%<carbon<0.5%
0.5%<manganese<3%
0.1%<silicon<0.5%
0.01%<chromium<1%
titanium<0.2%
aluminum<0.1%
phosphorus<0.1%
sulfur<0.05%
0.0005%<boron<0.08%, the remainder being iron and impurities inherent in processing, and the steel sheet has a very high mechanical resistance in excess of 1500 MPa after thermal treatment and the aluminum or aluminum alloy coating provides a high resistance to corrosion of the steel sheet.

### Claim 18 (depends on 17)

The coated steel sheet of claim 17 that is manufactured by a process comprising providing said hot rolled sheet; and coating said hot rolled sheet with an aluminum coating or aluminum alloy coating.

### Claim 19 (depends on 18)

The coated steel sheet of claim 18 wherein said aluminum or aluminum alloy coating is obtained by hot-dipping and comprises, before said thermal treatment, a first alloy layer in contact with the surface of the steel, and a second alloy layer on top of the first alloy layer.

### Claim 20 (depends on 19)

The coated steel sheet of claim 19 wherein the first coating layer comprises iron.

### Claim 21 (depends on 19)

The coated steel sheet of claim 19 wherein the second coating layer comprises iron.

### Claim 22 (depends on 17)

The coated steel sheet of claim 17 wherein the aluminum coating or aluminum alloy coating has a thickness of about 20 micrometers.

### Claim 23 (depends on 17)

The coated steel sheet of claim 17 wherein the steel in the sheet is treated with calcium.

### Claim 24 (depends on 17)

A coated steel sheet according to claim 17, manufactured by a process comprising a step of cold-rolling before said aluminum or aluminum alloy coating.

### Claim 25 (depends on 24)

The coated steel sheet of claim 24 that is composed predominately of martensite.

### Claim 26 (depends on 24)

The coated steel sheet of claim 24 wherein said subsequent thermal treatment includes hot-shaping the coated steel sheet, and cooling the hot-shaped sheet at a rate that produces martensitic structures, ferrite-martensitic structures , or ferrite-bainitic structures.

### Claim 27

A hot-rolled coated steel sheet comprising a hot-rolled steel sheet coated with an aluminum or aluminum alloy coating, wherein the steel in the sheet comprises the following composition by weight:
0.15%<carbon<0.5%
0.5%<manganese<3%
0.1%<silicon<0.5%
0.01%<chromium<1%
titanium<0.2%
aluminum<0.1%
phosphorus<0.1%
sulfur<0.05%
0.0005%<boron<0.08%, the remainder being iron and impurities inherent in processing, and the steel sheet has a very high mechanical resistance in excess of 1500 MPa after a subsequent thermal treatment, and the aluminum or aluminum alloy coating provides a high resistance to corrosion and prevents decarburization during said subsequent thermal treatment of the steel sheet.

### Claim 28 (depends on 27)

The coated steel sheet of claim 27 that is composed predominately of martensite.

### Claim 29 (depends on 27)

The coated steel sheet of claim 27 wherein said subsequent thermal treatment includes hot-shaping the coated steel sheet, and cooling the hot-shaped sheet at a rate that produces martensitic structures, ferrite-martensitic structures, or ferrite-bainitic structures.