# US 11,898,252 B2 · Aluminum-based alloy-plated steel sheet having excellent workability and corrosion resistance, and manufacturing method therefor

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- Number: US 11,898,252 B2
- Document ID: US11898252B2
- Status: Granted
- Kind: B2
- Application number: 17/786,452
- Filed: 2020-12-18
- Published: 2023-01-26
- Granted: 2024-02-13
- Earliest claimed: 2019-12-20
- Assignees: Posco
- Applicants: Posco
- Inventors: Suk-Kyu Lee; Hyeon-Seok Hwang; Myung-Soo Kim; Kwang-Tai Min; Dae-Young Kang
- Web page: https://patentgrep.com/patent/US11898252B2

## CPC

- C23C 2/12: Aluminium or alloys based thereon
- 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)
- C22C 21/00: Alloys based on aluminium
- C22C 21/10: with zinc as the next major constituent
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C23C 2/02: Pretreatment of the material to be coated, e.g. for coating on selected surface areas (C23C2/30 takes precedence)
- C23C 2/26: After-treatment (C23C2/14 takes precedence)
- C23C 2/261: {in a gas atmosphere, e.g. inert or reducing atmosphere}
- C23C 2/28: Thermal after-treatment, e.g. treatment in oil bath
- C23C 2/29: {Cooling or quenching}
- C23C 2/40: Plates; Strips
- C23C 28/02: only coatings {only including layers} of metallic material
- C23C 28/023: {only coatings of metal elements only}
- C23C 28/322: {only coatings of metal elements only}
- C23C 28/345: {with at least one oxide layer}
- 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)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

The present disclosure relates to an aluminum alloy-plated steel sheet having excellent workability and corrosion resistance and a method for manufacturing the same, and more particularly, to an aluminum alloy-plated steel sheet preventing microcracks generated during hot forming and has excellent seizure resistance and corrosion resistance, and a method for manufacturing the same.

## Claims

### Claim 1

An aluminum alloy-plated steel sheet comprising:
a base steel sheet; and
a single alloy-plated layer formed on the base steel sheet,
wherein the alloy-plated layer contains, by wt %, 35 to 50% of Fe, 1 to 20% of Zn, 5% or less of Mn, less than 0.1% of Si, and a balance of Al and unavoidable impurities, and
a ratio of an area occupied by the base steel sheet in a region from a surface roughness center line of the alloy-plated layer to 3/4t is 30% or more, where t is a distance from the surface roughness center line of the alloy-plated layer to the lowest line of the alloy-plated layer.

### Claim 2

An aluminum alloy-plated steel sheet comprising:
a base steel sheet; and
an alloy-plated layer formed on the base steel sheet,
wherein the alloy-plated layer includes:
a first alloy-plated layer that contains, by wt %, 35 to 50% of Fe, 1 to 20% of Zn, 5% or less of Mn, less than 0.1% of Si, and a balance of Al and unavoidable impurities; and
a second alloy-plated layer that contains, by wt %, 30 to 40% of Fe, 1 to 22% of Zn, 2% or less of Mn, less than 0.1% of Si, and a balance of Al and unavoidable impurities, and
a ratio of an area occupied by the base steel sheet in a region from a surface roughness center line of the alloy-plated layer to 3/4t is 30% or more, where t is a distance from the surface roughness center line of the alloy-plated layer to the lowest line of the alloy-plated layer.

### Claim 3 (depends on 1)

The aluminum alloy-plated steel sheet of claim 1, wherein a thickness of the alloy-plated layer is 5 to 25 μm.

### Claim 4 (depends on 1)

The aluminum alloy-plated steel sheet of claim 1, wherein the alloy-plated layer contains 80% or more of an Fe2Al5 alloy phase.

### Claim 5 (depends on 1)

The aluminum alloy-plated steel sheet of claim 1, wherein a content of Al in the alloy-plated layer is 40 to 60%.

### Claim 6 (depends on 2)

The aluminum alloy-plated steel sheet of claim 2, wherein a content of Zn in the second alloy-plated layer is higher than a content of Zn in the first alloy-plated layer.

### Claim 7 (depends on 2)

The aluminum alloy-plated steel sheet of claim 2, wherein a content of Zn in the first alloy-plated layer is 1 to 20%, and
a content of Zn in the second alloy-plated layer is 1.5 to 22%.

### Claim 8 (depends on 2)

The aluminum alloy-plated steel sheet of claim 2, wherein a content of Al in the first alloy-plated layer is 40 to 60%, and
a content of Al in the second alloy-plated layer is 40 to 65%.

### Claim 9 (depends on 2)

The aluminum alloy-plated steel sheet of claim 2, wherein a thickness of the first alloy-plated layer is 1 to 25 μm, and
a thickness of the second alloy-plated layer is 4 to 20 μm.

### Claim 10 (depends on 2)

The aluminum alloy-plated steel sheet of claim 2, wherein the first alloy-plated layer contains 80% or more of an Fe2Al5 alloy phase, and
the second alloy-plated layer contains 80% or more of an FeAl3 alloy phase.

### Claim 11 (depends on 1)

The aluminum alloy-plated steel sheet of claim 1, wherein the base steel sheet contains, by wt %, 0.05 to 0.3% of C, 0.1 to 1.5% of Si, 0.5 to 8% of Mn, 50 ppm or less of B, and a balance of Fe and unavoidable impurities.

### Claim 12

A method for manufacturing an aluminum alloy-plated steel sheet used for hot press forming, the method comprising:
preparing a base steel sheet;
dipping the base steel sheet in an aluminum plating bath that contains, by wt %, 3 to 30% of Zn, less than 0.1% of Si, and a balance of Al and unavoidable impurities to obtain an aluminum-plated steel sheet;
performing cooling by supplying air heated to 200 to 300° C. to the aluminum-plated steel sheet after the aluminum plating to form an oxide film on a surface of the aluminum-plated steel sheet; and
obtaining an aluminum alloy-plated steel sheet by on-line alloying in which heat treatment is performed after the cooling while maintaining the aluminum-plated steel sheet in a heating temperature range of 650 to 750° C. for 1 to 20 seconds.

### Claim 13 (depends on 12)

The method of claim 12, wherein an alloying temperature is controlled to satisfy the following Relational Expression 1:
150−0.4×[T]+3.3×10−4×[T]2−0.38×[wt % Zn]≤[wt % Fe]≤180−0.4×[T]+3.3×10−4×[T]2−0.38×[wt % Zn] [Relational Expression 1]
wherein [T] represents an alloy heat treatment temperature (° C.), [wt % Zn] represents a content of Zn wt % in the plating bath, and [wt % Fe] represents a content of Fe wt % in an alloy-plated layer.

### Claim 14 (depends on 12)

The method of claim 12, wherein the oxide film is formed on the surface of the aluminum-plated steel sheet at a thickness of 10% or more of the entire thickness of a hot-dip aluminum-plated layer.

### Claim 15 (depends on 1)

A hot-formed member obtained by subjecting the aluminum alloy-plated steel sheet of claim 1 to hot press forming.