Model Optimization And Application Of Hot Strip Mill Shape Controlling

Shape control of hot rolling strip is the focal point and key problem in the field of strip rolling. The model of shape controlling has been numerically and experimentally investigated and the basic theory of shape controlling is deeply analyzed by the equipment of 1750 hot strip mill for the purpose of improving the quality of hot rolling strip. The technology and equipment of shape control have been researched by field test and simulation program.The main research contents and the results are as follows:Shape controlling theory is studied by means of the model structure and algorithm. Technology and equipment influence factors of the shape control in the production field have been analyzed. The changing process of the thermal crown joggle between upper and bottom work rolls is analyzed by the contrast test. Several improvements were presented and water supply system of work roll has been reformed, which solved successfully the problem of the crown abrasion excessively among ahead three stands, keeping the steady rolling, decreasing the middle wave, and getting good quality of crown. The technique of CVC roll shape for finish back roll is proposed, which matches up work roll shape. So, the results show that the back roll failure accident decreases and the abrasion degree reduces 32.7% by contrast with flat back roll shape, which also prolongs the back roll service time and improves the shape quality.The simulation models of the bend force (BF) and rolling force (RF) prediction have been developed by the program platform of Matlab software and the technology of artificial neural networks (ANN).By this way, the results present that the precision of model prediction is improved by a large margin by using of ANN instead of traditional model prediction way and the prediction accuracy of bend force is improved 78.04%, and prediction accuracy of roll force is improved 36.71%, and this model accurate prediction of ANN is highly close to the actual results in hot rolling .One of the important factors of influencing strip shape control is the CVC roller model curve. Combined with the actual roller curve in production field, the equation of CVC roller model curve is computed and got fit curve in arithmetic model:y = 4.0326×10^-2-2.045×10^-3x+1.4522×10^-6x²-3.8045×10^-10x³The equation of the arithmetic model improves and optimizes the roll shape curve and improves remarkably shape controlling in the process of producing.The effect of the work roll and back roll abrasion on the crown controlling of strip was analyzed by collecting a lot of data from the spot. By roller abrasion testing, the abrasion law and degree of work roll in a rolling period time has been got. The abrasion quantity of upper work roll is more than that of bottom work roll, and the abrasion quantity of bottom back roll is more than that of upper back roll. The gross trend of the roller grinding and fatigue abrasion in all rolling machines is coincidence with that of rolling process. The abrasion quantity is related with the strip coil length, temperature, grade of steel, slip forward, slip back, cross flow, etc. In hot mill, the roll grinding and fatigue abrasion trend is similar to the actual technological parameters, which decreases the roll consuming and improves the technology of roll strategy management and roll grinding optimization.The load assignment of the rolling schedule and the technology parameters have been optimized to design and apply to the rolling schedule in the process of shape controlling and calculated by dynamic programming. The test results show that the gross power of load assignment has the superiority by dynamic programming in the case of the thickness fluctuation or other disturbance. Optimal rolling schedule can be got by coordinating the original one, and the flatness or straightness accuracy is improved. After redistributing load assignment and adjusting the thickness value of 6 stands, the gross power averagely decreases 3.37% by contrast with original condition, and decreases the load, and alleviates the abrasion degree. As the result, the shape controlling quality is improved effectively. This scheme is applied in hot strip mill to reduce the load of the rolling mill and improve the whole stands shape controlling ability.