Patent ID: 9260774
Filing Date: 2016-02-16
CPC Classification: B21B,C23C

Claim Text:
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%.