Study On Surface Quality And Influencing Factors Of Zinc Coating On Hot Dip Galvanized Steel

In recent years,with the rapid development of Chinese national economy,the demand for galvanized steel is increasing and the quality of galvanized steel is getting more and more important.The purpose of this study is to explore the influencing factors of the surface quality characteristics of hot galvanized strip(thickness of zinc layer and surface consistency of zinc layer)to improve the surface quality of hot galvanized strip.For coating thickness,this paper firstly used the response surface method(RSM)to design experiments including three parameters of air knife and established a polynomial model.Then,this paper used Taguchi methods to do the robustness analysis of air knife and validate the polynomial model.Finally,this paper built asuitable fitness function and used genetic algorithm to find the optimal combination of parameters for a given coating thickness.For the consistency of zinc layer,this paper used BP neural network to establish a network model including 16 input variables,and then used the sensitivity analysis method based on the network model to analyze the influence of all input variables on the output variable.On one hand,the polynomial model achieved a good prediction for the thickness of zinc layer,and the interaction between the range of air knife and strip speed was obvious.Then,this paper found air pressure was the dispersion factor and the range of air knife was the position factor.Finally,combined with the polynomial model and the robustness analysis results,a suitable fitness function is established and used to obtain the optimal combination of parameters.On the other hand,the BP neural network model realized a good prediction for the consistency of zinc layer.In addition,the results of sensitivity analysis showed that the galvanizing pretreatment process had the greatest impact on the final surface quality of zinc coating.Chemical degreasing concentration was the most critical factor affecting the consistency of zinc layer and the sensitivity coefficient was 0.7191.The sensitivity coefficient of electrolytic degreasing concentration,acid concentration,rolling thickness and raw material thickness was more than 0.5.