Research On Elongation Control System Of Skin Pass Mill

Temper is a final critical process in ensuring the finished quality of cold rolling strip, which is very important to improve quality of product, control the type version, and meet the user’s requirement for appropriate mechanical properties and surface state of steel strip. Elongation is of utmost importance as the only measurement of deformation, and also the unique distortion index of controlling the mechanical properties of steel strip. As a result of the many years practice and constantly perfect, temper technology and finished product quality in steel corporation is certain defect in its elongation constant control, which had restricted the process of normal production and improvement of economic technique targets.The back ground of this thesis is the elongation control system of single stand skin pass mill in A Cold Mill Factory. The paper is based on the digesting of control structure, process characteristic and pertinent process control method. By analyzing of history, current state, further, constituents and theory of this elongation control system one problems effecting on accuracy of elongation and consider of the measurement and calculation method of elongation. Analyze and compare steel strip elongation by regulating the speed of the S roller before and after the automatic control. Achieve automatic control of strip elongation by adjusting the strip tension. Achieve strip elongation automatic control strategy and three types of skin pass mill elongation by adjusting the rolling pressure. Through the analysis of the actual rolling mill, from the point of view of automatic control systems summarize the main issues of the elongation control accuracy:elongation measurement accuracy is not precise enough; process parameters pre-set accuracy is not high; control strategy is not excellent enough; composition of the control system is not perfect and so on. At last, establish two mathematics models, elongation control in roll force mode of SPM (skin pass mill) and elongation control in tension mode of SPM. It comes to the conclusion that elongation integrated control system in SPM is better in all respects. Elongation, rolling force and tension all three closed-loop adopt this system. Rolling force and tension respectively act as the inner loop while elongation acts as the outer loop. Set logic discriminator and dead zone in the channel elongation values and deviation measured values. Based on the elongation bias values, choose to use the rolling force control mode or tension control mode, and gives a logical selection criterion. Finally the paper studies the principles and applications of the PID controller in depth. Propose a fuzzy PID tension-control method based on elongation and rolling force. Establish a mathematics model, design the fuzzy PID controller according to the tension elongation control example, and take many simulations testing under system simulation condition. The theoretic analysis and computer simulation prove that the method can improve dynamic performance and stability of tension, it can also improve the control effect of elongation, help promote product quality.