Causes of warping defects on the surface of galvanized sheet

Aiming at three kinds of typical warping defects in a hot－dip galvanizing production line, the surface morphology and matrix structure of the defects were analyzed by scanning electron microscope, and the composition of the surface and cross section of the defects was analyzed by energy dispersive spectrometer, and then the process of the defects was identified. The results show that there were reduced iron oxide on the surface of No.1 sample, iron oxide and a large number of oxidation dots on the cross section, and high temperature welding in some warping areas, the dots were caused by the surface defects of the slab inherited to the subsequent process. There was reduced iron oxide on the surface of No.2 sample, iron oxide on the cross section, and high temperature welding in some warping areas, the dots were produced by hot rolling process. There was no iron oxide and oxide dots in sample 3, the warping defects were produced in the cold state.