Abstract
Air knife is the key equipment to determine zinc coating thickness in the hot-dip galvanizing process. The process parameters related to air knife directly determine whether the desired coating thickness can be obtained. Therefore, setting the optimal process parameters is the key step to improve hot dip galvanizing process capability and zinc coating quality. Previous research on zinc layer thickness was based on the principle of physics and simulation to build models and few studies were carried about the interaction between parameters of air knife. In this research, three process parameters (stripe velocity, air pressure and air knife-stripe distance) were considered to optimize coating thickness by Response Surface Method (RSM), Taguchi method and Genetic Algorithm (GA). This paper firstly used response surface method (RSM) to establish polynomial model and discuss interaction effect between air pressure and the range of air knife. Then, this paper used Taguchi method to do the robustness analysis of air knife and validate the polynomial model from response surface method. Finally, this paper built suitable a fitness function and then uses genetic algorithm to find the optimal combination of parameters for a given thickness of zinc layer. This proposed integrated method is a good try to combine RSM, Taguchi method and GA.
Highlights
The optimization of process parameters is routinely performed in the manufacturing industry so as to solve the challenges in product quality and/or optimize the cost effectiveness of manufacturing processes [1]
It was proved that the polynomial model had better fitting effect when the three interaction items were removed; (4) The significance of interaction effect could be seen from Table 5
On the one hand, when the strip speed increased from 40 m/min to 50 m/min, the zinc thickness increased, but the increase was obviously affected by the range of air knife: (1) when the range of air knife was between 23 mm and 24 mm, the zinc thickness increased rapidly with the steel speed; (2) when the range of air knife is over 24 mm, the zinc thickness increased slowly with the steel speed
Summary
The optimization of process parameters is routinely performed in the manufacturing industry so as to solve the challenges in product quality and/or optimize the cost effectiveness of manufacturing processes [1]. In hot-dip galvanizing process, zinc coating thickness is one of the main quality control factors of galvanized steel strip. Whether zinc coating thickness is in line with the needs of customers has critically important effects on the price of galvanized sheet. Zinc coating thickness control is an industrial problem, and an economic concern in modern rolling mills. Zinc coating thickness control includes two aspects: (1) Quality index, the uniformity of strip surface; (2) Cost index, mainly considering the deviation between the target thickness and the actual thickness [2,3]. Whether the zinc thickness reaches the customers’ standard or not is the key to decide the product quality. On the process of hot-dip galvanizing, air knife is the key equipment to control the coating thickness [4]. After strip is pulled out from zinc pot, the impact of the high velocity airflow from air knife will adhere to the strip surface and make the excess zinc liquid blown back to the zinc pot
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