The mechanism and control method of uneven zinc grain on hot rolled steel plate

Abstract

There has long been a certain enterprise that leads the line products of lead and zinc, which is facing inequality problems that seriously affect economic benefits. This study uses a confocal microscope, scanning electron microscope, electron probe, and chemical constant volume method to study the causes of the problem and the mechanism of the main influence factors. The results show that the surface roughness of hot rolled acid-washed substrate and the distribution of carbide in steel are the main factors that cause the zinc flower inhomogeneity. The increase of the nucleation point in the cooling process of the zinc pans with the roughness of the base plate. When the distribution of carbides along the ferrite grain boundary in steel occurs, the formation of Fe2Al5 is restricted. This results in a thinner inhibition layer on the substrate surface, leading to less consumption of aluminum. Consequently, the zinc layer nearby retains more aluminum content. Steel and carbide precipitation occurs in the intercrystalline structure, which inhibits the increase in the thickness of the strip’s surface layer. This leads to a higher consumption of aluminum, resulting in a lower zinc layer with reduced aluminum content. As a consequence, the liquid zinc forms droplets, allowing lead (Pb) and antimony (Sb) in the liquid zinc enough time for dendritic segregation to take place. This process increases dendrite growth and results in the formation of larger zinc grains.