# US 10,501,832 B2 · Plated steel sheet

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- Number: US 10,501,832 B2
- Document ID: US10501832B2
- Status: Granted
- Kind: B2
- Application number: 15/567,418
- Filed: 2016-04-22
- Published: 2018-04-19
- Granted: 2019-12-10
- Earliest claimed: 2015-04-22
- Assignees: Nippon Steel Corporation
- Applicants: Nippon Steel & Sumitomo Metal Corporation
- Inventors: Koutarou Hayashi; Akihiro Uenishi; Masaharu Kameda; Jun Haga; Kunio Hayashi; Kohichi Sano; Hiroyuki Kawata
- Web page: https://patentgrep.com/patent/US10501832B2

## CPC

- C22C 38/58: with more than 1.5% by weight of manganese
- C21D 8/0257: {with diffusion of elements, e.g. decarburising, nitriding}
- C21D 9/46: for sheet metals
- 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 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/08: containing nickel {(C22C38/105 takes precedence)}
- C22C 38/12: containing tungsten, tantalum, molybdenum, vanadium, or niobium
- C22C 38/14: containing titanium or zirconium
- C22C 38/16: containing copper
- C22C 38/18: containing chromium
- C22C 38/22: with molybdenum or tungsten
- C22C 38/34: with more than 1.5% by weight of silicon
- C22C 38/38: with more than 1.5% by weight of manganese
- C22C 38/42: with copper
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/48: with niobium or tantalum
- C22C 38/50: with titanium or zirconium
- C22C 38/54: with boron
- C23C 2/02: Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence)
- C23C 2/0224: {Two or more thermal pretreatments}
- C23C 2/024: {by cleaning or etching}
- 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 2211/001: Austenite
- C21D 2211/005: Ferrite
- C21D 2211/008: Martensite
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- 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)
- 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 base material (13) included in a plated steel sheet (1) includes a structure, at a ¼ sheet thickness position, represented by, in volume fraction: tempered martensite: 3.0% or more; ferrite: 4.0% or more; and retained austenite: 5.0% or more. An average hardness of the tempered martensite in the base material (13) is 5 GPa to 10 GPa, and a part or all of the tempered martensite and the retained austenite in the base material form an M-A. A volume fraction of ferrite in a decarburized ferrite layer (12) included in the plated steel sheet (1) is 120% or more of the volume fraction of the ferrite in the base material (13) at the ¼ sheet thickness position, an average grain diameter of the ferrite in the decarburized ferrite layer (12) is 20 μm or less, a thickness of the decarburized ferrite layer (12) is 5 μm to 200 μm, a volume fraction of tempered martensite in the decarburized ferrite layer (12) is 1.0 volume% or more, a number density of the tempered martensite in the decarburized ferrite layer (12) is 0.01/μm2 or more, and an average hardness of the tempered martensite in the decarburized ferrite layer (12) is 8 GPa or less.

## Claims

### Claim 1

A plated steel sheet, comprising:
a steel sheet; and
a plating layer on the steel sheet, wherein:
the plating layer is a hot-dip galvanizing layer or an alloyed hot-dip galvanizing layer;
the steel sheet comprises:
a base material; and
a decarburized ferrite layer on the base material;
the base material includes a chemical composition represented by, in mass %:
C: 0.03% to 0.70%;
Si: 0.25% to 3.00%;
Mn: 1.0% to 5.0%;
P: 0.10% or less;
S: 0.0100% or less;
sol. Al: 0.001% to 1.500%;
N: 0.02% or less;
Ti: 0.0% to 0.300%;
Nb: 0.0% to 0.300%;
V: 0.0% to 0.300%;
Cr: 0% to 2.000%;
Mo: 0% to 2.000%;
Cu: 0% to 2.000%;
Ni: 0% to 2.000%;
B: 0% to 0.0200%;
Ca: 0.00% to 0.0100%;
REM: 0.0% to 0.1000%; and
a balance: Fe and impurities;
the base material includes a structure, at a position at which a depth from a surface of the steel sheet corresponds to ¼ of a thickness of the steel sheet, represented by, in volume fraction:
tempered martensite: 3.0% or more;
ferrite: 4.0% or more; and
retained austenite: 8.3% or more;
an average hardness of the tempered martensite in the base material is 5 GPa to 10 GPa;
a part or all of the tempered martensite and the retained austenite in the base material form a Martensite-Austenite constituent;
a volume fraction of ferrite in the decarburized ferrite layer is 120% or more of the volume fraction of the ferrite in the base material at the position at which the depth from the surface of the steel sheet corresponds to ¼ of the thickness of the steel sheet;
an average grain diameter of the ferrite in the decarburized ferrite layer is 20 μm or less;
a thickness of the decarburized ferrite layer is 5 μm to 200 μm;
a volume fraction of tempered martensite in the decarburized ferrite layer is 1.0 volume % or more;
a number density of the tempered martensite in the decarburized ferrite layer is 0.01/μm2 or more; and
an average hardness of the tempered martensite in the decarburized ferrite layer is 8 GPa or less.

### Claim 2 (depends on 1)

The plated steel sheet according to claim 1, wherein, in the chemical composition,
Ti: 0.001% to 0.300%,
Nb: 0.001% to 0.300%, or
V: 0.001% to 0.300%,
or any combination thereof is satisfied.

### Claim 3 (depends on 1)

The plated steel sheet according to claim 1, wherein, in the chemical composition,
Cr: 0.001% to 2.000%, or
Mo: 0.001% to 2.000%,
or both of them is satisfied.

### Claim 4 (depends on 1)

The plated steel sheet according to claim 1, wherein, in the chemical composition,
Cu: 0.001% to 2.000%, or
Ni: 0.001% to 2.000%,
or both of them is satisfied.

### Claim 5 (depends on 1)

The plated steel sheet according to claim 1, wherein, in the chemical composition, B: 0.0001% to 0.0200% is satisfied.

### Claim 6 (depends on 1)

The plated steel sheet according to claim 1, wherein, in the chemical composition,
Ca: 0.0001% to 0.0100%, or
REM: 0.0001% to 0.1000%,
or both of them is satisfied.