12th International Conference on Zinc & Zinc Alloy Coated Steel Sheet - GALVATECH 2021

This study was carried out to improve the surface quality of galvanized steel, which are widely used in exposed automotive panels. To control zinc grain called as spangle that occurs during solidification of galvanized steel, In view of the metallurgical aspects, we considered a new method increasing the surface area of full hard steel associated with nucleation of molten zinc in the solidification during galvanizing by applying an improved surface treatment in work roll of tandem cold mill(TCM). As a result, among various parameters of surface roughness, we found that RPc(Peak count, cm-1) is associated with surface area more than Ra, moreover, through experiments by hot-dip galvanizing simulator, spangle of galvanized steel based on full hard steel having high surface area was found to be significantly tiny. By using these experimental results, we changed the processing method on final stand work roll of tandem cold mill(TCM) in the site and finally we were able to greatly reduce the spangle size of galvanized steel for exposed automotive panels compared to existing size without any additional facility investment.