ZINC-BASED METAL PLATED STEEL SHEET TREATED WITH PHOSPHATE BEING EXCELLENT IN FORMABILITY AND METHOD FOR PRODUCTION THEREOF

摘要

The aim of the present invention is to provide a phosphate treated zinc coated steel sheet with excellent workability. A steel sheet coated with a zinc based alloy has a phosphate treated coating on the surface thereof. The phosphate treated coating comprises mainly granulated crystals, specifically, crystals in which the average ratio of the major axis to the minor axis is not less than 1.00 and not more than 2.90. Moreover, the method for producing the phosphate treated coating uses a phosphate treatment solution in which the amount of Mg ions is >/= 6 g/l and the amount of Zn ions is >/= 0.5 g/l, or a phosphate treatment solution in which the amount of Mg ions is >/= 10 g/l, the amount of Zn ions is 0 /= 40 g/l. Moreover, the phosphate treated zinc coated steel sheet also has excellent corrosion resistance as the amount of Mg in the phosphate treated coating is not less than 10 mg/m<2>, and has excellent weldability as the coating amount is controlled to 0.5 to 3.0 g/m<2>.