Effect of strip entry temperature on interfacial layer and coating microstructure of galvanized sheet

Experiments were carried out to investigate the influence of strip entry temperature on interface reaction and microstructure of alloyed coatings. Industrial IF steel and DP980 steel were used as substrates to simulate hot galvanizing process in a zinc bath containing 0.13%(mass fraction)Al. The experimental results showed that the leakage plating of DP980 steel was severe and became more pronounced with increasing temperature, with the least severe leakage plating at 470 ℃. The IF steel coating quality remained good under all conditions. When the temperature is low, the interface forms dense and fine ζ phase. With the increase of temperature, the ζ phase coarsens and the δ phase increases. The peak value of interface aluminum enrichment decreases with the increase of temperature, and the enrichment degree of IF steel is higher. The interface aluminum enrichment of DP980 steel is weak due to the dense Mn/Si oxide on the surface. After alloying annealing, the interface aluminum enrichment of the low temperature sample is strong, and the alloying is incomplete; with increasing the pot temperature, the iron content of the coating increases, and the iron content is the best at 470 ℃. At 530 ℃, there is too thick Γ phase over-alloying. Experiments show that temperature of strip into pot affects the quality of the coating and the degree of alloying by regulating the interface aluminum enrichment and Fe-Zn phase transformation.