Method for manufacturing hot dip galvanized steel sheet

Patent metadata

Field	Value
Publication number	US-9260774-B2
Application number	US-201113638188-A
Country	US
Kind code	B2
Filing date	Mar 14, 2011
Priority date	Mar 31, 2010
Publication date	Feb 16, 2016
Grant date	Feb 16, 2016

Abstract

An object of the present invention is to make it possible, without necessitating an alkali pretreatment, to form a zinc oxide layer having excellent sliding properties on a hot dip galvanized steel sheet not subjected to alloying after galvanizing and thus having a relatively low degree of surface activity. Another object of the present invention is to make it possible to manufacture a hot dip galvanized steel sheet having higher area ratio of Zn oxide layer formed on a coating surface and larger thickness of the Zn oxide layer. Specifically, the present invention provides a method for manufacturing a hot dip galvanized steel sheet comprising: subjecting a steel sheet to hot dip galvanizing and subsequent temper rolling; bringing the steel sheet into contact with acidic solution having pH buffering capacity; retaining the steel sheet for 1 second to 60 seconds after the contact with the acidic solution; and rinsing the steel sheet with water, to form a zinc oxide layer on a coating surface of the steel sheet, characterized in that the method further comprising:
carrying out the temper rolling by either rolling the steel sheet first with a dull roll having Ra≧2.0 μm at rolling reduction rate ≦5% and then with a bright roll having Ra≦0.1 μm at rolling reduction rate ≦3% or rolling the steel sheet first with a bright roll having Ra≦0.1 μm at rolling reduction rate ≦3% and then with a dull roll having Ra≦2.0 μm at rolling reduction rate ≦5%.

First claim

The invention claimed is:

1. A method for manufacturing a hot dip galvanized steel sheet comprising: subjecting a steel sheet to hot dip galvanizing and subsequent temper rolling; bringing the steel sheet into contact with acidic solution having pH buffering capacity; retaining the steel sheet for 1 second to 60 seconds after the contact with the acidic solution; and rinsing the steel sheet with water, to form a zinc oxide layer on a coating surface of the steel sheet, wherein the method further comprising:
carrying out the temper rolling by either rolling the steel sheet first with a dull roll having Ra≧2.0 μm at rolling reduction rate ≦5% and then with a bright roll having R≦0.1 μm at rolling reduction rate ≦3% or rolling the steel sheet first with a bright roll having Ra≦0.1 μm at rolling reduction rate ≦3% and then with a dull roll having Ra≧2.0 μm at rolling reduction rate 5%.

2. The method for manufacturing a hot dip galvanized steel sheet of claim 1 , wherein the acidic solution having pH buffering capacity is an acidic solution containing at least one substance selected from acetic acid salt, phthalic acid salt, citric acid salt, succinic acid salt, lactic acid salt, tartaric acid salt, boric acid salt, phosphoric acid salt and sulfuric acid salt, and pH of the acidic solution is in the range of 1.0 to 5.0.

3. The method for manufacturing a hot dip galvanized steel sheet of claim 1 or 2 , further comprising:
setting coating weight of liquid film of the acidic solution having pH buffering capacity on the coating surface of the steel sheet when contact of the steel sheet with the acidic solution is completed to be 15 g/m 2 or less.

4. The method for manufacturing a hot dip galvanized steel sheet of claim 1 or 2 , further comprising:
subjecting a coating layer of the galvanized steel sheet to alloying treatment and then the temper rolling as described in claim 1 .

5. The method for manufacturing a hot dip galvanized steel sheet of claim 1 , wherein the temper rolling is carried out by rolling the steel sheet first with a dull roll having Ra≧2.0 μm at rolling reduce rate ≦5% and then with a bright roll having Ra≦0.1 μm at rolling reduction rate 3%.

Assignees

• Hoshino Katsuya
• Kubota Takahiro
• Tada Masahiko
• Nagoshi Masayasu
• Tanimoto Wataru
• Kijima Hideo
• Higai Kazuhiko
• Jfe Steel Corp

Inventors

• Hoshino Katsuya
• Kubota Takahiro
• Tada Masahiko
• Nagoshi Masayasu
• Tanimoto Wataru
• Kijima Hideo
• Higai Kazuhiko

Classifications

• C23C28/025

  with at least one zinc-based layer · CPC title

• C23C2/26 Primary

  After-treatment (C23C2/14 takes precedence) · CPC title

• B21B1/22

  for rolling {plates, strips,} bands or sheets of indefinite length (B21B1/42 takes precedence) · CPC title

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• B21B2001/228

  skin pass rolling or temper rolling · CPC title