Study And Optimization For The Width Control Of Hot Rolled Strips

In order to improve the width control and crop loss in hot strip roughing mill, HV rolling process(H: horizontal, V:vertical) are studied and optimized for roughing mill of 2050mm tandem hot strip line in Bao Steel. The main achievements contain:1) A 3D thermo-mechanical coupled model for vertical/horizontal rolling is established using a rigid-plastic FEM software, which is applied to simulate the rolling processes on 2050mm roughing mill of Bao steel. The calculated width of strip using the actual parameters is in good agreement with the measured value at the exit of roughing mill, thus the model is effective. Aiming at the question that the strip width is controlled difficultly, in this study, the spread law is investigated by FEM simulation. The law of the strip spread (natural spread, dogbone spread and combined spread) is obtained.2) Using the 3D thermal-mechanical coupled rigid-plastic FEM model, we simulated the rolling processes on 2050mm hot roughing mill of Baosteel company. The calculated tail shapes of st rip are in good agreement with actual pictures, thus the model is validated. Based on FEM simulation, the forming mechanism of fish-tail on the strip tail end was investigated, and the distribution of tail cropping at each pass was obtained. A negative tension control between vertical and horizontal rollers was brought forward, which could reduce the crop loss offish-tail according to calculated results.3) The 3D thermal-mechanical coupled FEM model for edging and horizontal rolling also has been used to investigate the SSC model for controlling head and tail shape in the roughing mill of 2050mm hot mill of Baosteel. The law of width shrinkage on head and tail ends is analyzed, and a new SSC model is induced by the function of both the steel width and the draught of edging. By comparison of calculation results of the original model and the new model, it can be seen that the width shrinkage of the head and tail ends is well decreased using the SSC model established.4) Particle Swarm Optimization(PSO) algorithm is applied in model optimization more and more frequently and it was used to optimize the mathematical model for the width expansion. The result from the computer simulation demonstrated the algorithm’s validity and effectiveness.5) Under the analysis of the main factor influencing on the width spreading at finishing mill(FM),a integrated width spreading and narrowing prediction model has been established based on the the recursive least square method(RLSM), The result from the computer simulation and actual production demonstrated that the accuracy of width spreading prediction was improved.In a sentence, the series of research works have brought to light the laws of HV rolling process, some technics methods have been brought forward, which could reduce the crop loss of the strip head and tail ends, and developed the relevant programs,and a better SSC polynomial curve is obtained,also the algorithm’s validity and effectiveness is proved,finally,a integrated width spreading and narrowing prediction model is established.It has been proved that these obtained results are reasonable by applications in Baosteel.