Method for manufacturing galvanized steel sheet

Patent metadata

Field	Value
Publication number	US-9809884-B2
Application number	US-201414761133-A
Country	US
Kind code	B2
Filing date	Jan 14, 2014
Priority date	Jan 16, 2013
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

There is provided a method for manufacturing a galvanized steel sheet that has low sliding resistance in press forming and good degreasing property even under severe alkaline degreasing treatment conditions due to low temperature and short process line length. An oxide layer formed on the surface of a galvanized steel sheet is subjected to neutralization treatment using an alkaline aqueous solution containing 0.01 g/L or more of P ions and 0.01 g/L or more of colloid dispersed particles, wherein the alkaline aqueous solution preferably contains at least one phosphorus compound selected from phosphates, pyrophosphates, and triphosphates and at least one type of colloid dispersed particles selected from Ti, silica, Pt, Pd, Zr, Ag, Cu, Au, and Mg.

First claim

The invention claimed is:

1. A method for manufacturing a galvanized steel sheet that includes an oxide layer on the surface thereof, comprising:
an oxide layer forming step of bringing a galvanized steel sheet into contact with an acidic solution for 1 to 60 seconds, and then washing the galvanized steel sheet with water; and
a neutralization treatment step of bringing a surface of an oxide layer, formed in the oxide layer forming step, into contact with an alkaline aqueous solution for 0.5 seconds or more, washing the surface of the oxide layer with water, and drying the surface of the oxide layer;
wherein the alkaline aqueous solution contains 0.01 g/L or more of P ions and 0.01 g/L or more of colloid dispersed particles.

2. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the alkaline aqueous solution contains at least one phosphorus compound selected from phosphates, pyrophosphates, and triphosphates and at least one type of colloid dispersed particles selected from Ti, silica, Pt, Pd, Zr, Ag, Cu, Au, and Mg.

3. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the alkaline aqueous solution has a pH in the range of 9 to 12 and a temperature in the range of 20° C. to 70° C.

4. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the acidic solution has a pH buffering action and a degree of pH increase in the range of 0.003 to 0.5, the degree of pH increase being the amount (L) of 1.0 mol/L sodium hydroxide solution required to increase a pH of 1′L of the acidic solution to 2.0 to 5.0.

5. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the acidic solution contains 5 to 50 g/L in total of at least one salt selected from acetates, phthalates, citrates, succinates, lactates, tartrates, borates, and phosphates, has a pH in the range of 0.5 to 5.0, and a temperature in the range of 20° C. to 70° C.

6. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the amount of acidic solution deposited on the surface of the galvanized steel sheet after contact with the acidic solution in the oxide layer forming step is 15 g/m 2 or less.

7. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the galvanized steel sheet is a galvannealed steel sheet.

8. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the galvanized steel sheet is a hot-dipped galvanized steel sheet.

9. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the galvanized steel sheet is an electrogalvanized steel sheet.

10. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the galvanized steel sheet is subjected to skin pass rolling before the oxide layer forming step.

11. The method for manufacturing a galvanized steel sheet according to claim 1 , wherein the galvanized steel sheet is brought into contact with an alkaline aqueous solution to activate the surface thereof before the oxide layer forming step.

Assignees

• Jfe Steel Corp

Inventors

• Hoshino Katsuya
• Taira Shoichiro
• Tanimoto Wataru
• Nagoshi Masayasu

Classifications

• C23C22/53

  Treatment of zinc or alloys based thereon · CPC title

• C23C22/78

  Pretreatment of the material to be coated · CPC title

• C23C22/07 Primary

  containing phosphates · CPC title

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• C23C22/83

  Chemical after-treatment · CPC title