# US 11,078,564 B2 · Hot-dip galvanized steel sheet with excellent surface quality and resistance to low temperature brittle fracture

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- Number: US 11,078,564 B2
- Document ID: US11078564B2
- Status: Granted
- Kind: B2
- Application number: 16/062,945
- Filed: 2016-12-22
- Published: 2018-12-20
- Granted: 2021-08-03
- Earliest claimed: 2015-12-22
- Assignees: Posco
- Applicants: Posco
- Inventors: Sang-Heon Kim
- Web page: https://patentgrep.com/patent/US11078564B2

## CPC

- C23C 2/06: Zinc or cadmium or alloys based thereon
- 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}
- C22C 18/00: Alloys based on zinc
- C22C 18/04: with aluminium as the next major constituent
- C22C 38/00: Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00)
- C23C 2/0222: {in a reactive atmosphere, e.g. oxidising or reducing atmosphere (C23C2/024 takes precedence)}
- C23C 2/024: {by cleaning or etching}
- C23C 2/26: After-treatment (C23C2/14 takes precedence)
- C23C 2/40: Plates; Strips
- C21D 9/46: for sheet metals
- Y10T 428/12799: Next to Fe-base component [e.g., galvanized]
- 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)
- 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)
- 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)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Provided is a hot-dip galvanized steel sheet including a base steel sheet and a hot-dip zinc-based plating layer formed on the base steel sheet. The hot-dip zinc-based plating layer includes a Zn single phase having an average equivalent circular diameter of 120 μm or less as a microstructure. In the Zn single phase, a Zn single phase having a crystal structure of which a {0001} plane is parallel to a surface of the steel sheet, is provided in an area fraction of 70% or less.

## Claims

### Claim 1

A hot-dip galvanized steel sheet comprising:
a base steel sheet; and a hot-dip zinc-based plating layer formed on a surface of the base steel sheet,
wherein the base steel sheet includes: concave-convex portions formed on the surface thereof, and the concave-convex portions form a wave having a wavelength of 0.1 μm to 1 μm and a wave height of 0.1 μm to 0.5 μm, and
wherein the hot-dip zinc-based plating layer includes a Zn single phase having an average equivalent circular diameter of 20 μm to 120 μm as a microstructure, and
in the Zn single phase, a Zn single phase having a crystal structure of which a {0001} plane is parallel to the surface of the base steel sheet, is provided in an area fraction of 70% or less.

### Claim 2 (depends on 1)

The hot-dip galvanized steel sheet of claim 1, wherein the average equivalent circular diameter is 20 μm to 100 μm.

### Claim 3 (depends on 1)

The hot-dip galvanized steel sheet of claim 1, wherein the hot-dip zinc-based plating layer comprises, by wt %, Al: 0.15% to 0.4%, at least one of Mg, Ca, and Mn: 0.05% to 0.2% in total, and a balance of Zn and inevitable impurities.

### Claim 4 (depends on 3)

The hot-dip galvanized steel sheet of claim 3, wherein the hot-dip zinc-based plating layer further comprises, by wt %, Be: 0.0001% to 0.002%.

### Claim 5 (depends on 1)

The hot-dip galvanized steel sheet of claim 1, wherein the area fraction is 65% or less.