Research on Surface Defect Control Technology for Advanced High Strength Hot Dip Galvanized Automobile Sheet

Abstract

For expanding the application in the automotive field, the surface defect control technology for advanced high strength hot dip galvanized automobile sheet was studied. Results showed that the oxygen potential of alloy element was lower than that of Fe during hot rolling, annealing and hot galvanizing processes, resulting in an “internal oxidation” phenomenon, which made defects easily to occur on the surface of galvanized products. Focusing on such four main surface defects as iron leakage, chicken claw print, color difference and pockmarked surface, the main factors causing the defects and the mechanisms for the formation of defects were determined. Through the measure of corresponding production control processes, the commuted rates of defects declined to below 0.58%, 0.19%, 0.52% and 0.15% respectively.

Keywords

• advanced high strength steel|automobile sheet|hot dip galvanized|surface defect