Hot Dip Zinc Alloy Plated Steel Sheet Having Excellent Corrosion Resistance and External Surface and Method for Manufacturing Same

• US 20150159253A1
• Filed: 07/23/2013
• Published: 06/11/2015
• Est. Priority Date: 07/23/2012
• Status: Active Grant

• Current Assignee: POSCO Co. Ltd. (Posco Holdings Incorporated)
• Original Assignee: Posco Holdings Incorporated
• Inventors: Oh, Min-Suk, Jin, Young-Sool, Kim, Sang-Heon, Kim, Su-Young, Yoo, Bong-Hwan
• Granted Patent: US 9,745,654 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C22C 18/00 Alloys based on zinc
• CPC Class Codes: C22C 18/04 with aluminium as the next major constituent
• CPC Class Codes: C23C 2/06 Zinc or cadmium or alloys based thereon
• CPC Class Codes: C23C 2/16 using fluids under pressure, e.g. air knives
• CPC Class Codes: C23C 2/20 Strips; Plates
• CPC Class Codes: C23C 2/29 Cooling or quenching
• CPC Class Codes: Y10T 428/12799 Next to Fe-base component [e.g., galvanized]

Abstract

Provided is a hot dip zinc alloy plated steel sheet which is widely used in vehicles, domestic appliances, construction materials or the like and a method for manufacturing the same. A Zn—Al—Mg hot dip zinc alloy plating bath is used for manufacturing the hot dip zinc alloy plated steel strip, and a small amount of Ga or In is added to the plating bath for inhibiting an oxidation reaction of Mg in the plating bath so as to obtain excellent corrosion resistance and external surface of the plated steel sheet which is manufactured at this point.

Claims

1. A hot-dip zinc alloy plated steel sheet having excellent corrosion resistance and an excellent external surface comprising:

a base steel plate; and

a hot-dip zinc alloy plating layer,

wherein a composition of the hot-dip zinc alloy plating layer includes, in % by weight, aluminum (Al);

0.5 to 5.0% and magnesium (Mg);

1 to 5%, one or two types of gallium (Ga);

0.01 to 0.1% and indium (In);

0.005 to 0.1%, and a remainder of zinc (Zn) and unavoidable impurities, and a compositional ratio of the Mg and the Al satisfies a relationship of [Al+Mg≦

7].

2. The hot-dip zinc alloy plated steel sheet having excellent corrosion resistance and an excellent external surface of claim 1, wherein the hot-dip zinc alloy plating layer is attached in a plating amount of 10 to 500 g/m² based on one surface.

3. The hot-dip zinc alloy plated steel sheet having excellent corrosion resistance and an excellent external surface of claim 1, wherein the hot-dip zinc alloy plating layer employs a Zn—

Al—

MgZn₂ ternary eutectic structure as a base structure, and includes a plating structure in which a Zn—

MgZn₂ binary eutectic structure is dispersed, and includes an Al single phase structure and a Zn single phase structure in 20% or less, and includes a MgZn₂ structure as the rest.

4. The hot-dip zinc alloy plated steel sheet having excellent corrosion resistance and an excellent external surface of claim 1, which has surface roughness (Ra) of 1 μ

m or less.

5. A method for manufacturing a hot-dip zinc alloy plated steel sheet having excellent corrosion resistance and an excellent external surface comprising:

preparing a hot-dip zinc alloy plating bath including, in % by weight, aluminum (Al);

0.5 to 5.0% and magnesium (Mg);

1 to 5%, one or two types of gallium (Ga);

0.01 to 0.1% and indium (In);

0.005 to 0.1%, and a remainder of zinc (Zn) and unavoidable impurities, and a compositional ratio of the Mg and the Al satisfies a relationship of [Al+Mg≦

7];

preparing a plated steel sheet by dipping a base steel plate in the hot-dip zinc alloy plating bath and carrying out plating; and

gas wiping and cooling the plated steel sheet.

6. The method for manufacturing a hot-dip zinc alloy plated steel sheet having excellent corrosion resistance and an excellent external surface of claim 5, wherein the hot-dip zinc alloy plating bath plating carries out the plating at a temperature of greater than or equal to melting point to less than or equal to 440°

C.

7. The method for manufacturing a hot-dip zinc alloy plated steel sheet having excellent corrosion resistance and an excellent external surface of claim 5, wherein the gas used in the gas wiping is nitrogen (N₂).

8. The method for manufacturing a hot-dip zinc alloy plated steel sheet having excellent corrosion resistance and an excellent external surface of claim 5, wherein the cooling is carried out at a cooling rate of 10°

C./s or more.