Hot-dip galvanized steel sheet and method for producing the same

A method for producing a hot-dip galvanized steel sheet, comprising the steps of:

• rough rolling a steel containing 0.04 to 0.12% of C, 0.5% or less of Si, 1.0 to 2.0% of Mn, 0.05% or less of P, 0.005% or less of S, 0.05 to 1.0% of Cr, 0.005 to 0.2% of V, 0.1% or less of sol. Al, and 0.01% or less of N by weight %;
• finish rolling the rough rolled steel at a temperature of the Ar3 point or more;
• coiling the finish rolled steel at a temperature of 700° C. or less;
• and
• hot-dip galvanizing the coiled steel at a pre-plating heating temperature of Ac1 to Ac3.

A hot-dip galvanized steel sheet comprising:

• a steel sheet containing 0.04 to 0.13% of C, 0.5% or less of Si, 1.0 to 2.0% of Mn, 0.05% or less of P, 0.01% or less of S, 0.05% or less of sol. Al, 0.007% or less of N, 0.05 to 0.5% of Mo, and 0.2% or less of Cr by weight %;
• said steel sheet having a structure consisting essentially of ferrite having an average grain size of 20 μm or less and martensite with a volume percentage of 5 to 40%;
• and
• a hot-dip galvanizing layer formed on the steel sheet.

A method for producing a hot-dip galvanized steel sheet, comprising the steps of:

• rolling a steel containing 0.04 to 0.13% of C, 0.5% or less of Si, 1.0 to 2.0% of Mn, 0.05% or less of P, 0.01% or less of S, 0.05% or less of sol. Al, 0.007% or less of N, 0.05 to 0.5% of Mo, and 0.2% or less of Cr by weight % to produce a strip;
• pickling said strip;
• and
• performing a continuous hot-dip galvanizing, said continuous hot-dip galvanizing comprising the steps of:
• soaking the pickled strip at a temperature of 750 to 850° C.;
• cooling the soaked strip to a temperature range of 600° C. or lower at a cooling rate of 1 to 50° C. per second;
• hot-dip galvanizing the cooled strip;
• and
• cooling the galvanized strip so that the residence time at 400 to 600° C. is within 200 seconds.