Hot-Dip Galvanized Sheet Steel with Excellent Press Formability and Surface Quality for the Automotive Panels

摘要

A new type of a hot-dip galvanized steel sheet (GI steel sheet), excellent in press formability, weldability and surface appearance, for automotive bodies has been developed. As for press formability, through the optimization of surface roughness effected by texture control with skin-pass rolling and by the use of a high-lubricating oil, sliding characteristics has been improved. Concerning an advantage in weldability, with the suitable selection of coating and substrate chemistry, the life of welding electrode has been extended. Improved surface quality for the better exterior appearance was achieved through the introduction of such measures as the prevention of bath wrinkle patterns by adjusting a wiping condition, the avoidance of dross adherence with the use of bath exclusive for GI use, and the substantial reduction of spangles by using cooling rate control after galvanizing. The hot-dip galvanized steel sheet demonstrates distinguished characteristics as a material sheet for automotive outer panels. The newly developed GI sheets are put into commercial production.