Research On Temperature Control System Of Cold Rolling Continuous Annealing Furnace

Continuous annealing furnace is the most important equipment on continuous annealing line, which will directly affect the product's quality, quantity and cost of cold strip steel. The research on annealing furnace temperature control system makes sense in increasing productivity and improving product quality. In view of hysteretic nature of temperature control system for heating furnace, it is difficult to achieve good control effect when conventional PID control strategy is employed. So, to study a good performance for temperature control strategies will undoubtedly have a practical significance.This thesis with the annealing furnace of Xinsteel 1550mm continuous annealing line as the background, and focuses on analysis the L1 temperature control system of the continuous annealing furnace, which contains the design of strip temperature control loop, tube temperature control loop and burner control loop, and takes profound research on pulse control strategy of burner in the system. Finally, the advantages and defects of the L1 temperature control system were researched.The heat transfer model inside the furnace is build up by field method. The heating section is divided in 50 calculation units according to its structure characteristics, and precise mathematical models are used to describe the heat transfer and radiation heat balance in each unit. The heat transfer model is divided into 3 parts:strip temperature distribution calculation, radiant tube burning calculation and thermal inertia calculation. Through iterative computation for the heat transfer between the strip and radiant tube in each calculation unit, the results of strip temperature distribution, radiant tube power and furnace heat inertia time will be obtained.The L2 temperature control system based on the furnace heat transfer model is been studied. Four kinds of control strategies are analyzed, which are in steady state, transition state, speed or temperature offset state and speed constraint state, according to the actual production situation. And a representation of the hardware and software structure of the L2 system was made, especially the self-learning process of model was analyzed. The HMI screen of L2 temperature control system is described at end.In the actual production results show that the after the above methods were adopted:both the L1 and L2 system has good performance on the temperature control when the furnace is in the steady state. But when the furnace is in fluctuation state, the strip temperature will be in large fluctuation because of the high hysteretic of continuous annealing furnace. Compared with the alone L1 temperature control system, after L2 temperature control system are added to the system, the system shows better temperature tracking performance, smaller overshoot and shorter adjusting time.