# US 12,110,570 B2 · Cold rolled, coated and post batch annealed steel sheet

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- Number: US 12,110,570 B2
- Document ID: US12110570B2
- Status: Granted
- Kind: B2
- Application number: 18/135,962
- Filed: 2023-04-18
- Published: 2023-08-17
- Granted: 2024-10-08
- Earliest claimed: 2015-02-25
- Assignees: ArcelorMittal
- Applicants: ArcelorMittal
- Inventors: Hyun Jo Jun
- Web page: https://patentgrep.com/patent/US12110570B2

## CPC

- C21D 9/46: for sheet metals
- B32B 15/013: {one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium}
- C21D 1/20: Isothermal quenching, e.g. bainitic hardening
- C21D 1/25: Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- C21D 8/0226: {Hot rolling}
- C21D 8/0236: {Cold rolling}
- C21D 8/0247: characterised by the heat treatment
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/06: containing aluminium
- C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/26: with niobium or tantalum
- C22C 38/38: with more than 1.5% by weight of manganese
- C23C 2/02: Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence)
- C23C 2/022: {by heating}
- C23C 2/06: Zinc or cadmium or alloys based thereon
- C23C 2/28: Thermal after-treatment, e.g. treatment in oil bath
- C23C 2/29: {Cooling or quenching}
- C23C 2/40: Plates; Strips
- C21D 2211/002: Bainite
- C21D 2211/005: Ferrite
- C21D 2211/008: Martensite
- 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)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)

## Abstract

A cold rolled, coated and post batch annealed steel sheet produced by a method is provided. The method includes cold rolling a steel sheet; coating the cold rolled steel sheet with a zinc or zinc alloy coating, the cold rolled, coated steel sheet having an initial hole expansion and an initial yield strength and post batch annealing the cold rolled, coated steel sheet at a tempering temperature in a range from 150 to 650° C., the post batch annealed steel sheet having a final hole expansion and a final yield strength. The steel sheet includes (in wt. %) C—0.1-0.3%, Mn—1-3%, Si—0.5-3.5%, Al—0.05-1.5% and Mo+Cr being between 0-1.0%. The final hole expansion is at least 80% greater than the initial hole expansion and the final yield strength is at least 30% greater than the initial yield strength.

## Claims

### Claim 1

A cold rolled, coated, annealed and post tempered steel sheet comprising:
a steel sheet including in wt. %:
C 0.1-0.3%;
Mn 1-3%;
Si 0.5-3.5%;
Al 0.05-1.5%;
Mo+Cr being between 0-1.0%; and
a zinc or zinc alloy coating on the cold rolled steel sheet;
the cold rolled, coated, annealed and post tempered steel sheet having a hole expansion from 15 to 33.7%,
a yield strength from 700 to 969 MPa; and
a tensile strength from 1100 to 1240 Mpa;
the cold rolled, coated, annealed and post tempered steel sheet formed from a steel sheet that is cold rolled and zinc coated to define a coated cold rolled steel sheet having a hole expansion that is <15%, and a yield strength that is at least 30% less than the yield strength of the cold rolled, coated and post tempered steel sheet, the coated cold rolled steel sheet annealed to define a cold rolled, coated and annealed steel sheet, the cold rolled, coated and annealed steel sheet then post tempered at a temperature between 150-650°, thereby forming the cold rolled, coated, annealed and post tempered steel sheet.

### Claim 2 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the post tempering is performed at a temperature between 150-450° C.

### Claim 3 (depends on 2)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 2 wherein the post tempering is performed at a temperature between 200-400° C.

### Claim 4 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the post tempering is performed for a period of time sufficient to increase the yield strength of the coated cold rolled steel sheet by at least 40%.

### Claim 5 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the post tempering is performed for a period of time sufficient to increase the hole expansion of the coated cold rolled steel sheet by at least 95%.

### Claim 6 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein a total elongation of the cold rolled, coated, annealed and post tempered steel sheet is from 12 to 17, a total elongation of the coated cold rolled steel sheet is at least 25% less.

### Claim 7 (depends on 6)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 6 wherein the post tempering is performed for a period of time sufficient to increase the total elongation of the coated cold rolled steel sheet by at least 40%.

### Claim 8 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the steel sheet comprises C 0.15-0.25%.

### Claim 9 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the steel sheet comprises Mn 2-2.5%.

### Claim 10 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the steel sheet comprises Si 1.5-2.5%.

### Claim 11 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the steel sheet comprises Al—0.05-1.0%.

### Claim 12 (depends on 1)

The cold rolled, coated, annealed and post tempered and steel sheet as recited in claim 1 wherein the yield strength of the coated cold rolled steel sheet is from 550 to 580 MPa.

### Claim 13 (depends on 1)

The cold rolled, coated, annealed and post tempered annealed steel sheet as recited in claim 1 wherein the steel sheet comprises Mo+Cr between 0.2-0.5%.

### Claim 14 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the cold rolled steel sheet is hot rolled before the zinc coating is applied, a hot rolling finishing temperature is in a range from 840 to 890° C. and a coiling temperature is in a range from 500 to 650° C.

### Claim 15 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the coated cold rolled steel sheet is subjected to heating at a rate of 25° C./h, isothermal tempering at a desired temperature for 5 hours and then cooling at a rate of 25° C./h.

### Claim 16 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the post tempering occurs for at least 5 hours.

### Claim 17 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the hole expansion of the cold rolled, coated, annealed and post tempered steel sheet is from 15 and 25%, the yield strength of the cold rolled, coated, annealed and post tempered steel sheet is from 700 to 850 MPa, the tensile strength of the cold rolled, coated, annealed and post tempered steel sheet is from 1100 to 1200 MPa, and the total elongation of the cold rolled, coated, annealed and post tempered steel sheet is from 12 to 17%.

### Claim 18 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the microstructure consists of ferrite, bainitic ferrite and martensite including MA islands.

### Claim 19

A cold rolled, coated, annealed and post batch annealed steel sheet formed by a method comprising the steps of:
cold rolling a steel sheet comprising (in wt. %):
C 0.1-0.3%;
Mn 1-3%;
Si 0.5-3.5%;
Al 0.05-1.5%; and
Mo+Cr being between 0-1.0%;
coating the cold rolled steel sheet with a zinc or zinc alloy coating to form a cold rolled, coated steel sheet;
annealing the cold rolled, coated steel sheet to form a cold rolled, coated and annealed steel sheet; and
post batch annealing the cold rolled, coated and annealed steel sheet at a tempering temperature in a range from 150 to 650° C. to form the cold rolled, coated, annealed and post batch annealed steel sheet;
the cold rolled, coated, annealed and post batch annealed steel sheet having a hole expansion from 15 to 33.7%, a yield strength from 700 to 969 MPa, a tensile strength from 1100 to 1240 Mpa and a total elongation from 12 to 17%;
the hole expansion of the cold rolled, coated, annealed and post batch annealed steel sheet being at least 80% greater than a hole expansion of the cold rolled, coated steel sheet, and the yield strength of the cold rolled, coated, annealed and post batch annealed steel sheet being at least 30% greater than a yield strength of the cold rolled, coated steel sheet.

### Claim 20 (depends on 19)

The cold rolled, coated, annealed and post batch annealed steel sheet as recited in claim 19 wherein the method further includes coiling the cold rolled, coated steel sheet into at least one coil, after the coating step and prior to the post batch annealing step; and wherein the coating is by hot dip galvanizing in a bath of molten zinc or zinc alloy.

### Claim 21 (depends on 19)

The cold rolled, coated, annealed and post batch annealed steel sheet as recited in claim 19 wherein the tempering temperature in a range from 150 to 500° C.

### Claim 22 (depends on 19)

The cold rolled, coated, annealed and post batch annealed steel sheet as recited in claim 19 wherein the cold rolled, coated, annealed and post batch annealed steel sheet and the cold rolled, coated and annealed steel sheet have different microstructures.

### Claim 23 (depends on 22)

The cold rolled, coated, annealed and post batch annealed steel sheet as recited in claim 22 wherein a carbon concentration in phases of the cold rolled, coated and annealed steel sheet is different from a carbon concentration in phases of the cold rolled, coated, annealed and post batch annealed steel sheet.

### Claim 24 (depends on 23)

The cold rolled, coated, annealed and post batch annealed steel sheet as recited in claim 23 wherein the microstructures of the cold rolled, coated, annealed and post batch annealed steel sheet and the cold rolled, coated and annealed steel sheet both comprise ferrite, martensite and austenite.

### Claim 25 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the steel sheet comprises (in wt. %):
C 0.15-0.25%;
Mn 2-2.5%;
Si 1.5-2.5%; and
Al 0.05-1.0%.

### Claim 26 (depends on 25)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 25 wherein the steel sheet comprises C 0.18-0.25%.

### Claim 27 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the microstructure of the cold rolled, coated, annealed and post tempered steel sheet consists of 38 to 72% ferrite, including bainitic ferrite, and 28 to 62% martensite including MA islands.

### Claim 28 (depends on 1)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 1 wherein the hole expansion of the coated cold rolled steel sheet is <10%.

### Claim 29 (depends on 2)

The cold rolled, coated, annealed and post tempered steel sheet as recited in claim 2 wherein the post tempering is performed at a temperature between 150-300° C.

### Claim 30 (depends on 19)

The cold rolled, coated, annealed and post batch annealed steel sheet as recited in claim 19 wherein the cold rolled, coated, annealed and post tempered steel sheet and the cold rolled, coated and annealed steel sheet have microstructures comprising ferrite, martensite and austenite, and a carbon concentration in the ferrite, martensite and austenite of the cold rolled, coated and annealed steel sheet being different from a carbon concentration in the ferrite, martensite and austenite of the cold rolled, coated, annealed and post tempered steel sheet.

### Claim 31 (depends on 19)

The cold rolled, coated, annealed and post batch annealed steel sheet as recited in claim 19 wherein the hole expansion of the coated cold rolled steel sheet is <10%.