# US 10,370,737 B2 · High-strength galvanized steel sheet

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- Number: US 10,370,737 B2
- Document ID: US10370737B2
- Status: Granted
- Kind: B2
- Application number: 15/543,271
- Filed: 2015-11-24
- Published: 2018-02-01
- Granted: 2019-08-06
- Earliest claimed: 2015-01-15
- Assignees: Jfe Steel Corporation
- Applicants: Jfe Steel Corporation
- Inventors: Hiroshi Hasegawa; Hideyuki Kimura; Yoshimasa Funakawa; Yoichi Makimizu; Yoshitsugu Suzuki
- Web page: https://patentgrep.com/patent/US10370737B2

## 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}
- B32B 15/04: comprising metal as the main or only constituent of a layer, {which is} next to another layer of {the same or of} a {different material (next to a bituminous or tarry layer B32B11/08; next to a water-setting substance layer B32B13/06; next to a glass layer B32B17/061; next to a cellulosic plastic layer B32B23/042)}
- B32B 15/043: {of metal (B32B15/01 takes precedence)}
- B32B 15/18: comprising iron or steel {(B32B15/011, B32B15/012 and B32B15/013 take precedence)}
- C21D 6/001: {containing Ni (C21D6/004 takes precedence)}
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- 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 8/0263: {following hot rolling}
- C21D 8/0463: {following hot rolling}
- C21D 8/0473: {Final recrystallisation annealing}
- C22C 38/00: Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00)
- 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 38/24: with vanadium
- C22C 38/26: with niobium or tantalum
- C22C 38/38: with more than 1.5% by weight of manganese
- C22C 38/58: 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 2/0224: {Two or more thermal pretreatments}
- C23C 2/06: Zinc or cadmium or alloys based thereon
- C23C 2/12: Aluminium or alloys based thereon
- C23C 2/28: Thermal after-treatment, e.g. treatment in oil bath
- C23C 2/285: {for remelting the coating}
- C23C 2/40: Plates; Strips
- C23C 30/00: Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process (C23C26/00, C23C28/00 take precedence)
- C23C 30/005: {on hard metal substrates}
- C21D 2211/001: Austenite
- C21D 2211/005: Ferrite
- C21D 2211/008: Martensite
- Y10T 428/12757: Fe
- Y10T 428/12799: Next to Fe-base component [e.g., galvanized]
- Y10T 428/12951: Fe-base component
- Y10T 428/12958: Next to Fe-base component
- Y10T 428/12972: Containing 0.01-1.7% carbon [i.e., steel]
- 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)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A high-strength galvanized steel sheet and method for producing the same. The high-strength galvanized steel sheet including a specified chemical composition and a microstructure comprising, in terms of area fraction, a tempered martensite phase: 30% or more and 73% or less, a ferrite phase: 25% or more and 68% or less, a retained austenite phase: 2% or more and 15% or less, and other phases: 10% or less (including 0%), the other phases comprising a martensite phase: 3% or less (including 0%) and a bainitic ferrite phase: less than 5% (including 0%), the tempered martensite phase having an average grain size of 8 μm or less, the ferrite phase having an average grain size of 5 μm or less, and the retained austenite phase having a C content less than 0.7% by mass.

## Claims

### Claim 1

A high-strength galvanized steel sheet having a chemical composition comprising, by mass %:
C: 0.15% or more and 0.25% or less;
Si: 0.50% or more and 2.5% or less;
Mn: 2.3% or more and 4.0% or less;
P: 0.100% or less;
S: 0.02% or less;
Al: 0.01% or more and 2.5% or less;
at least one element selected from the group consisting of Nb: 0.005% or more and 0.1% or less, Ti: 0.005% or more and 0.1% or less, V: 0.01% or more and 1.0% or less, and Mo: 0.005% or more and 2.0% or less; and
the balance being Fe and inevitable impurities,
wherein the steel sheet has a microstructure comprising, in terms of area fraction, a tempered martensite phase: 30% or more and 73% or less, a ferrite phase: 25% or more and 68% or less, a retained austenite phase: 2% or more and 15% or less, other phases: 10% or less (including 0%) in total, the other phases comprising, in terms of area fraction, a martensite phase: 3% or less (including 0%), and bainitic ferrite phase: 0%,
the tempered martensite phase having an average grain size of 8 μm or less,
the ferrite phase having an average grain size of 5 μm or less, and
the retained austenite phase having a C content less than 0.7% by mass.

### Claim 2 (depends on 1)

The high-strength galvanized steel sheet according to claim 1, wherein the galvanized steel sheet includes a galvannealed steel sheet.

### Claim 3 (depends on 2)

The high-strength galvanized steel sheet according to claim 2, wherein the galvanized steel sheet has a tensile strength of 1180 MPa or more.

### Claim 4 (depends on 1)

The high-strength galvanized steel sheet according to claim 1, wherein the galvanized steel sheet has a tensile strength of 1180 MPa or more.

### Claim 5 (depends on 1)

The high-strength galvanized steel sheet according to claim 1, wherein the chemical composition further comprises at least one group selected from the group consisting of:
group A: by mass %, at least one element selected from the group consisting of Cr: 0.01% or more and 2.0% or less, Ni: 0.01% or more and 2.0% or less, and Cu: 0.01% or more and 2.0% or less,
group B: by mass %, B: 0.0002% or more and 0.0050% or less, and
group C: by mass %, at least one element selected from the group consisting of Ca: 0.001% or more and 0.005% or less and REM: 0.001% or more and 0.005% or less.

### Claim 6 (depends on 5)

The high-strength galvanized steel sheet according to claim 5, wherein the galvanized steel sheet includes a galvannealed steel sheet.

### Claim 7 (depends on 6)

The high-strength galvanized steel sheet according to claim 6, wherein the galvanized steel sheet has a tensile strength of 1180 MPa or more.

### Claim 8 (depends on 5)

The high-strength galvanized steel sheet according to claim 5, wherein the galvanized steel sheet has a tensile strength of 1180 MPa or more.