Characteristics of Sliver Defects Caused by Mould Flux Entrainment on the Surface of the Hot-Dip Galvanised Automobile Exposed Panel

The characteristics of sliver defects caused by entrained mold fluxes were analyzed after nonaqueous electrolysis. There are three types of entrained mold fluxes, namely the granular, flaky and blocky. When the entrained mold fluxes are small, they are granular or flaky. When the entrained mold fluxes are large, they are blocky or flaky. From the start part of the defect zone, the area fraction of the entrained mold fluxes per unit area decreases exponentially with the length of defect. After the mold fluxes are entrained into the molten steel, SiO2 will react with Al and Ti, resulting in the changes in compositions of mould powders. On the cross-section, the zinc layer thickness in the defect zone, is 22-35 mu m, thicker than that in the non-defect zone. Near the entrained mold fluxes, the randomness of grain orientation and the inhomogeneity of grain size are increased and the local grains are refined.