Research On Asymmetric Shape Control Method Of Four High Cold Strip Mill

The strip shape is important qualitative index of the high-level cold-strip steel. The shape control is the core technology of cold rolling mill. The majority of cold strip rolling mill has only symmetric shape control means. The asymmetric shape defects can only be eliminated by stepped cooling. Stepped cooling can improve the quality of shape greatly, but there is a serious time lag. Therefore, it is very necessary to develop online asymmetric shape control means. In this dissertation, a four-high cold strip mill is taken as researching object, whose the influence on shape of shape control under the asymmetrical bending force, asymmetrical shifting and tilting roll are analyzed fully and provide the basis for the formulation of the shape control strategy.According to the characteristics of four-high mill asymmetric rolling, rolls system model is established on base of the influence function method. Strip element method is selected for establishing metal deformation model. The whole model of asymmetrical rolling is established for four- high mill. The calculation flow chart of the three are given, emulation software of asymmetrical rolling is developed depending on C++ language.In order to increases the precision of flatness pattern recognition and refines flatness control target, linear, quadratic, cubic and biquadratic Legendre orthogonal polynomials are used as basic patterns. The flatness pattern recognition model is building based on least square theory. MATLAB language is applied to write software of flatness pattern recognition.The simulated results of contact pressure between rolls,roll gap’s shape, bearing rolling force and front tension stress transverse distribution is carried out corresponding variable asymmetrical bending force, asymmetrical middle roll’s shifting and tilting roll. Flatness pattern recognition model developed in this thesis are applied for the identification of the calculated residual stress, then get various order components of various regulating means. The result opens out the effective rules of various regulating means on various order components and provides the theory foundation for asymmetrical shape on-line control.