Analysis of coarse stripes of alloyed hot-dip galvanized steel sheets

Zinc iron alloy hot-dip galvanized steel sheet is widely used in the automobile and household appliance industry because of its good weldability, coating property, and corrosion resistance. In the production of alloyed hot-dip galvanized steel sheets, stripe defects are often found on the surface of the strip, which affects the diffusion reaction of iron and zinc and causes the defects to be amplified. Coarse stripes are one of the main ones. In this paper, the coarse stripe defect on the surface of an alloyed hot-dip galvanized steel plate was studied, by means of the Scanning Electron Microscope and Energy Spectrum, combined with the verification of galvanizing production. The results showed that the morphology of the coarse stripes defect area on the surface of the alloyed hot-dip galvanized sheet exhibited concave-convex features, and the average iron content was 1.41% lower, compared with the defect-free area, Indicating that the streak defect region was insufficiently alloyed. It is presumed that there is oxide in the region of the streak defect. By adopting the cleaning zone and adjusting the atmosphere in the furnace, the incidence of defects was reduced by 76%, and the quality of the slab was significantly improved.