The Research On Loads And Their Preset Of Hot Strip Tandem Mill

In modern computer controlled hot strip tandem mill production, the preset of rolling load is very important, which is the kernel of computer preset model in hot strip tandem mill. The precision of rolling load will directly affect the preset of roll gap, and then affect the stability of strip threading, the accuracy of strip thickness and the quality of strip shape. Presently, there is still a wide gap between our country and the advanced level of the world in the preset of rolling load. In addition, high demands of the thickness accuracy and shape quality are put forward by customers. Therefore, to research the preset of rolling load is very significant both in theory and practicality.Based on the steel samples and data which were from the 2050mm hot strip rolling plant of Baoshan steel, this thesis systematically researched the preset of rolling load by using the method which combined numerical simulation with physical simulation and referring to the concept of robustness design.Firstly, the steel samples were conducted compression deformation experiment at high temperature with Gleeble-1500D thermo-mechanical simulator. After this experiment, the influences of temperature, strain and strain rate on the deformation resistance were detailedly analyzed and the deformation resistance tabular data were obtained. Meanwhile, aimed at the influence of the phase transformation on the deformation resistance, the rolling loads were modified by the modifying factors. The result shows that the accuracy of rolling load at each pass is improved remarkably, especially at the third pass, the accuracy of rolling load upgrades 5.7%.Secondly, based on the rolling parameters and the deformation resistance tabular data obtained by the experiment, the finite element model of hot strip tandem mill process was established by using DEFORM-2D software. The variation of temperature and rolling loads were mainly analyzed and the simulated values were contrasted with the calculated values of Baoshan steel model and measured values. The result indicates that the simulated rolling forces are closer to the measured values, their errors are less than 5.5%; meanwhile, the accuracy of finite element method is higher than that of Baoshan steel model, especially at the third pass, the accuracy of rolling force is 4.3% higher than that of Baoshan steel model.Lastly, according to the principle and method of rolling schedule, the traditional schedule and the new rolling schedule with large reduction at the last pass were respectively formulated. Subsequently, regarding the roll eccentricity as the "noise" factor and regarding the variation of rolling load as the response of product by referring to the concept of robustness design, the hot strip tandem mill processes under different rolling schedules were simulated by using DEF0RM-2D software. After the simulation, the variations of rolling loads of different rolling schedules were analyzed and contrasted, and then the fluctuation ranges of rolling loads at the last pass were respectively calculated. The result displays that the fluctuation of rolling load of the new schedule is remarkably less than that of traditional schedule and the fluctuation range of the new one is also less than that of the traditional one. Accordingly, rolling load of the new schedule is able to restrain the influence of roll eccentricity better. In other words, the rolling load of the new schedule has a better robustness.In a word, the conclusion of this thesis can supply important reference to the hot strip tandem mill production.