Hot dip Galvanized steel plate excellent in balance of strength and ductility and in adhesiveness between steel and plating layer

A method of producing a hot dip Zn galvanized steel sheet having excellent balance between tensile strength and ductility and excellent coating adhesion, comprising the steps of:

• preparing hot-rolled steel sheet or cold-rolled steel sheet having a steel sheet average composition which includes:
• 0.05-0.25 mass % of C;
• not more than 2.0 mass % Si;
• 1.0-2.5 mass % of Mn;
• and 0.005-0.10 mass % of Al;
• heating the hot-rolled steel sheet or cold-rolled steel sheet in an atmosphere which satisfies the following formula at a temperature of 800-1000° C.:
• log(H2O/H2)≧2.5[C]−3.5
• wherein H2O/H2 represents the ratio of the partial pressure of moisture in the atmosphere with respect to the partial pressure of hydrogen gas, and [C] represents the amount of C in the steel (mass %);
• cooling the hot-rolled steel sheet or cold-rolled steel sheet;
• pickling the surface of the steel sheet, so that a decrease in the weight of the steel sheet due to pickling, when it is expressed as a Fe converted value, is 0.05-5 g/m2;
• heating the steel sheet again in a continuous-type hot dip Zn galvanizing line to a temperature of 700-850° C.;
• and
• subjecting the steel sheet to a hot dip Zn galvanizing process.