Strip cooling control for flexible production of galvanized flat steel

The work is devoted to the problem of flexible small-scale production of galvanized steel of various sizes on a continuous hot-dip galvanizing unit with varying productivity. The main focus is on the heat treatment of steel strip, the requirements for which limit productivity. In conditions of disturbances, it is necessary to proactively control the heat treatment using models, or to reduce the speed of the strip to ensure that the requirements are met. Unlike most of the works that focus on heat control, this work focuses on strip cooling. Based on the analysis of production data of the Magnitogorsk Iron and Steel Works, it is shown that violation of the cooling requirements leads to the appearance of defects in the zinc coating. Dependence of the probability of defects occurrence on the strip temperature is given. Problems of cooling predictive control are formulated using models in the absence of temperature control of the cooling section cavity. For each of the tasks, the model structure and the method of its tuning are determined according to the data accumulated over a significant period of the unit operation under conditions of uncontrolled systematic disturbances. The structure of the cooling control system is proposed by estimation of the cooling section cavity temperature as a controlled variable. The temperature estimate is determined from the model. The lack of measurement of the cooling section cavity temperature is not a problem then varying productivity. The results of the models tuning are presented according to the data of the Magnitogorsk Iron and Steel Works continuous hot-dip galvanizing unit. The proposed structures of the models and methods for their adjustment can be applied in the development of models for metal heating in furnaces.

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