METHOD FOR MANUFACTURING ZINC-BASED COATED STEEL SHEET

• US 20190093206A1
• Filed: 02/16/2017
• Published: 03/28/2019
• Est. Priority Date: 03/11/2016
• Status: Active Grant

• Current Assignee: JFE Steel Corporation (JFE Holdings Incorporated)
• Original Assignee: JFE Steel Corporation (JFE Holdings Incorporated)
• Inventors: Hoshino, Katsuya, Furuya, Shinichi, Matsuda, Takeshi, Tsuchimoto, Kazuaki, Matsuzaki, Akira
• Granted Patent: US 10,443,116 B2
• Time in Patent Office: Days
• CPC Class Codes: C23C 2/06 Zinc or cadmium or alloys based thereon
• CPC Class Codes: C23C 2/26 After-treatment C23C2/14 takes precedence
• CPC Class Codes: C23C 22/34 containing fluorides or complex fluorides
• CPC Class Codes: C23C 22/82 After-treatment
• CPC Class Codes: C23C 22/83 Chemical after-treatment

Abstract

Provided is a method for manufacturing a zinc-based coated steel sheet having excellent press formability. The method includes an oxide layer-forming step of bringing the zinc-based coated steel sheet into contact with an acidic solution, holding the zinc-based coated steel sheet for 1 second to 60 seconds, and then water-washing the zinc-based coated steel sheet and a neutralization step of holding a zinc-based oxide layer formed in the oxide layer-forming step for 0.5 seconds or more in such a state that a surface of the zinc-based oxide layer is in contact with an alkaline aqueous solution, water-washing the zinc-based oxide layer, and then drying the zinc-based oxide layer. The acidic solution contains HF₂Na and/or HF₂K in a total amount of 0.10 g/L to 5.0 g/L.

Claims

1. A method for manufacturing a zinc-based coated steel sheet having a zinc-based oxide layer on a surface thereof, the method comprising:

an oxide layer-forming step of bringing the zinc-based coated steel sheet into contact with an acidic solution, holding the zinc-based coated steel sheet for 1 second to 60 seconds, and then water-washing the zinc-based coated steel sheet; and

a neutralization step of holding a zinc-based oxide layer formed in the oxide layer-forming step for 0.5 seconds or more in such a state that a surface of the zinc-based oxide layer is in contact with an alkaline aqueous solution, water-washing the zinc-based oxide layer, and then drying the zinc-based oxide layer,

wherein the acidic solution contains HF₂Na and/or HF₂K in a total amount of 0.10 g/L to 5.0 g/L.

2. The method for manufacturing the zinc-based coated steel sheet according to claim 1, wherein the acidic solution contains at least one or more of surfactants among cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants.

3. The method for manufacturing the zinc-based coated steel sheet according to claim 1, wherein the zinc-based oxide layer contains a crystalline structure substance represented by Zn₄(SO₄)_1-x(CO₃)_x(OH)₆.nH₂O.

4. The method for manufacturing the zinc-based coated steel sheet according to claim 2, wherein the zinc-based oxide layer contains a crystalline structure substance represented by Zn₄(SO₄)_1-x(CO₃)_x(OH)₆.nH₂O.