# US 11,028,458 B2 · Steel sheet and plated steel sheet

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- Number: US 11,028,458 B2
- Document ID: US11028458B2
- Status: Granted
- Kind: B2
- Application number: 16/481,291
- Filed: 2017-01-27
- Published: 2019-11-07
- Granted: 2021-06-08
- Earliest claimed: 2017-01-27
- Assignees: Nippon Steel Corporation
- Applicants: Nippon Steel Corporation
- Inventors: Yuri Toda; Masafumi Azuma; Akihiro Uenishi; Eisaku Sakurada; Tatsuo Yokoi; Genichi Shigesato
- Web page: https://patentgrep.com/patent/US11028458B2

## CPC

- C21D 9/46: for sheet metals
- B21B 1/02: for rolling heavy work, e.g. ingots, slabs, {blooms, or} billets, in which the cross-sectional form is unimportant {; Rolling combined with forging or pressing}
- B21B 3/02: Rolling special iron alloys {, e.g. stainless steel}
- B32B 15/01: all layers being exclusively metallic {(making layered metal workpieces by pressure cladding B23K20/22; making coatings with a metallic material characterised by its composition C23C30/00)}
- C21D 6/004: {containing Cr and Ni}
- C21D 6/005: {containing Mn}
- C21D 6/008: {containing Si}
- C21D 8/02: during manufacturing of plates or strips (C21D8/12 takes precedence)
- C21D 8/0263: {following hot rolling}
- 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 38/005: {containing rare earths, i.e. Sc, Y, Lanthanides}
- C22C 38/008: {containing tin}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/14: containing titanium or zirconium
- C22C 38/42: with copper
- B21B 2001/028: {Slabs}
- 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)
- B21B: ROLLING OF METAL (auxiliary operations used in connection with metal-working operations covered in B21, see B21C; bending by rolling B21D; manufacture of particular objects, e.g. screws, wheels, rings, barrels, balls, by rolling B21H; pressure welding by means of a rolling mill B23K20/04)
- 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)

## Abstract

When a zone surrounded by a grain boundary that is measured to be 5.0° or more by an EBSD analysis is assumed to be a grain, and when a K value is a value obtained by multiplying an average value of Image Qualities in a grain by 10−3, a Y value is an average crystal misorientation (°) in the grain, a metallic phase 1 is a metallic phase the K value of which is less than 4.000, a metallic phase 2 is a metallic phase the K value of which is 4.000 or more and the Y value of which is 0.5 to 1.0, a metallic phase 3 is a metallic phase the K value of which is 4.000 or more and the Y value of which is less than 0.5, and a metallic phase 4 is a metallic phase that falls under none of metallic phases 1 to 3, there is provided a steel sheet that has a predetermined chemical composition and includes a microstructure including, in area percent, a metallic phase 1: 1.0% or more and less than 35.0%, a metallic phase 2: 30.0% or more and 80.0% or less, a metallic phase 3: 5.0% or more and 50.0% or less, and a metallic phase 4: 5.0% or less. The steel sheet has a strength as high as 590 MPa or more (further, 780 MPa or more) in terms of tensile strength and has an excellent hole-expansion property.

## Claims

### Claim 1

A steel sheet comprising
a chemical composition consisting of, in mass percent:
C: 0.01 to 0.20%;
Si: 0.005 to 0.10%;
Mn: 0.60 to 4.00%;
Al: 0.55 to 3.00%;
P: 0.10% or less;
S: 0.03% or less;
N: 0.01% or less;
O: 0.01% or less;
Ti: 0 to 2.00%;
Nb: 0 to 2.00%;
V: 0 to 0.30%;
Cu: 0 to 2.00%;
Ni: 0 to 2.00%;
Mo: 0 to 1.00%;
Cr: 0 to 2.00%;
B: 0 to 0.01%;
Ca: 0 to 0.010%;
Mg: 0 to 0.010%;
Zr: 0 to 0.050%;
REM: 0 to 0.1%;
Sb: 0 to 0.10%;
Sn: 0 to 0.10%; and
As: 0 to 0.5%,
with the balance: Fe and impurities, and comprising
a microstructure that includes,
when a zone surrounded by a grain boundary that is measured to be 5.0° or more by an EBSD analysis is assumed to be a grain, and when
a K value is a value obtained by multiplying an average value of Image Qualities in a grain by 10−3,
a Y value is an average crystal misorientation (°) in the grain,
a metallic phase 1 is a metallic phase the K value of which is less than 4.000,
a metallic phase 2 is a metallic phase the K value of which is 4.000 or more and the Y value of which is 0.5 to 1.0,
a metallic phase 3 is a metallic phase the K value of which is 4.000 or more and the Y value of which is less than 0.5, and
a metallic phase 4 is a metallic phase that falls under none of metallic phases 1 to 3, and the metallic phase 4 comprises at least one of upper bainite, lower bainite, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.

### Claim 2 (depends on 1)

The steel sheet according to claim 1, comprising a microstructure in which the metallic phase 4 is 0%.

### Claim 3 (depends on 1)

The steel sheet according to claim 1, wherein 60.0% or more of boundaries of the metallic phase 1 with other metallic phases is a boundary of the metallic phase 1 with the metallic phase 2.

### Claim 4 (depends on 3)

The steel sheet according to claim 3, wherein a thickness of the steel sheet is 0.8 to 3.6 mm.

### Claim 5 (depends on 4)

The steel sheet according to claim 4, wherein
the steel sheet has a tensile strength of 780 MPa or more, and comprises a microstructure including, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and less than 35.0%; and
the metallic phase 4: 5.0% or less.

### Claim 6 (depends on 4)

The steel sheet according to claim 4, wherein
the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa, and comprises a microstructure including:
the metallic phase 1: 1.0% or more and less than 30.0%;
the metallic phase 2: 35.0% or more and 70.0% or less;
the metallic phase 3: 35.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.

### Claim 7 (depends on 3)

The steel sheet according to claim 3, wherein
the steel sheet has a tensile strength of 780 MPa or more, and comprises a microstructure including, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and less than 35.0%; and
the metallic phase 4: 5.0% or less.

### Claim 8 (depends on 3)

The steel sheet according to claim 3, wherein
the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa, and comprises a microstructure including:
the metallic phase 1: 1.0% or more and less than 30.0%;
the metallic phase 2: 35.0% or more and 70.0% or less;
the metallic phase 3: 35.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.

### Claim 9 (depends on 1)

The steel sheet according to claim 1, wherein a thickness of the steel sheet is 0.8 to 3.6 mm.

### Claim 10 (depends on 9)

The steel sheet according to claim 9, wherein
the steel sheet has a tensile strength of 780 MPa or more, and comprises a microstructure including, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and less than 35.0%; and
the metallic phase 4: 5.0% or less.

### Claim 11 (depends on 9)

The steel sheet according to claim 9, wherein
the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa, and comprises a microstructure including:
the metallic phase 1: 1.0% or more and less than 30.0%;
the metallic phase 2: 35.0% or more and 70.0% or less;
the metallic phase 3: 35.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.

### Claim 12 (depends on 1)

The steel sheet according to claim 1, wherein
the steel sheet has a tensile strength of 780 MPa or more, and comprises a microstructure including, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and less than 35.0%; and
the metallic phase 4: 5.0% or less.

### Claim 13 (depends on 1)

The steel sheet according to claim 1, wherein
the steel sheet has a tensile strength of 590 MPa or more and less than 780 MPa, and comprises a microstructure including:
the metallic phase 1: 1.0% or more and less than 30.0%;
the metallic phase 2: 35.0% or more and 70.0% or less;
the metallic phase 3: 35.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.

### Claim 14 (depends on 1)

A plated steel sheet comprising a galvanized layer on a surface of the steel sheet according to claim 1.

### Claim 15 (depends on 1)

A plated steel sheet comprising a galvannealed layer on a surface of the steel sheet according to claim 1.

### Claim 16

A steel sheet comprising
a chemical composition comprising, in mass percent:
C: 0.01 to 0.20%;
Si: 0.005 to 0.10%;
Mn: 0.60 to 4.00%;
Al: 0.55 to 3.00%;
P: 0.10% or less;
S: 0.03% or less;
N: 0.01% or less;
O: 0.01% or less;
Ti: 0 to 2.00%;
Nb: 0 to 2.00%;
V: 0 to 0.30%;
Cu: 0 to 2.00%;
Ni: 0 to 2.00%;
Mo: 0 to 1.00%;
Cr: 0 to 2.00%;
B: 0 to 0.01%;
Ca: 0 to 0.010%;
Mg: 0 to 0.010%;
Zr: 0 to 0.050%;
REM: 0 to 0.1%;
Sb: 0 to 0.10%;
Sn: 0 to 0.10%; and
As: 0 to 0.5%,
with the balance: Fe and impurities, and comprising
a microstructure that includes,
when a zone surrounded by a grain boundary that is measured to be 5.0° or more by an EBSD analysis is assumed to be a grain, and when
a K value is a value obtained by multiplying an average value of Image Qualities in a grain by 10−3,
a Y value is an average crystal misorientation (°) in the grain,
a metallic phase 1 is a metallic phase the K value of which is less than 4.000,
a metallic phase 2 is a metallic phase the K value of which is 4.000 or more and the Y value of which is 0.5 to 1.0,
a metallic phase 3 is a metallic phase the K value of which is 4.000 or more and the Y value of which is less than 0.5, and
a metallic phase 4 is a metallic phase that falls under none of metallic phases 1 to 3, and the metallic phase 4 comprises at least one of upper bainite, lower bainite, in area percent:
the metallic phase 1: 1.0% or more and less than 35.0%;
the metallic phase 2: 30.0% or more and 80.0% or less;
the metallic phase 3: 5.0% or more and 50.0% or less; and
the metallic phase 4: 5.0% or less.

### Claim 17 (depends on 16)

The steel sheet according to claim 16, comprising a microstructure in which the metallic phase 4 is 0%.

### Claim 18 (depends on 16)

The steel sheet according to claim 16, wherein
60.0% or more of boundaries of the metallic phase 1 with other metallic phases is a boundary of the metallic phase 1 with the metallic phase 2.

### Claim 19 (depends on 16)

The steel sheet according to claim 16, wherein a thickness of the steel sheet is 0.8 to 3.6 mm.