Study On Strip Shape Computational Theory Of Strip Mill And Its Application In Wide Strip Rolling

The study on strip shape computational theory of strip mill is a subject which has important theoretical value and practical significance. This paper analyses comprehensively the present status of two main parts of the computational theory of strip shape, which are the deformation of rolls(elastic deformation and thermal deformation) and 3-D plastic deformation of metal. The numerical method of deformation of rolls and the analogue of strip lateral thickness distribution by the spline function are selected as main subject in this dissertation, and the research on theory and engineering application is carried out systematically and deeply.Firstly, this paper carries out theoretical studying to the numerical method of elastic deformation of strip mill's rolls. The characteristic and regularity of elastic deformation of strip mill's rolls are calculated using the large-scale FEM software MARC. The influences of different factors on elastic deformation of rolls are analyzed. It is the first time that the finite strip method is used to establish the elastic deformation model of rolls, which improves the calculating accuracy and decreases the amount of calculation. Secondly, the finite difference model of temperature field in work roll cross section of strip mill is established. It is the first time that the models on axisymmetric temperature field and thermal crown of work roll are established using the spline finite strip method. The thermal deformation characteristic of work roll is studied comprehensively, and the calculating accuracy of thermal crown model is improved. Finally, it is the first time that B3 spline function is used in the analogue of strip lateral thickness distribution. The variational method calculating the lateral flow of metal in roll gap is extended to the asymmetric rolling situations which have local high points. The influence of initial local high point of hot rolled strip and lateral diversity of strip material property on internal stress distribution and thickness of cold rolled strip are quantitatively researched for the first time. These improve the simulating accuracy of strip flatness and profile. Based on the above, the variational method calculating the lateral flow of metal in roll gap is combined with the finite strip method calculating elastic deformation of rolls, the model of compositely calculating flatness and profile of cold rolling strip is established. The experiments which are done on 1220HC cold strip continuous mill and 1420CVC cold strip continuous mill justify the correctness of the model. It is indicated that the model established in this paper improves the calculating accuracy of flatness and profile of strip.In the industrial application, the new calculating model of temperature field and thermal crown of work roll is adopted to establish the thermal crown on-line calculating model of work roll of 1450 hot strip continuous mills. This model can take the influence of the pass schedule, the specs of workpiece, the temperature, the rolling speed, the volume of cooling water and its distribution on work roll thermal crown into account. It can track and calculate the temperature field and the thermal crown of work roll at any time. This model has passed the examination of the production field. For meeting the needs of renovation of 1450 hot strip mill, the optimization design of volume and distribution of work roll cooling water was done using the calculating model of temperature field and thermal crown of work roll. Using the composite calculation model of flatness and profile of cold rolled strip, the strip shape of 1220HC cold strip continuous mill was simulated. This work has important application value to improve the strip shape presetting accuracy of 1220HC cold continuous mills. The simulating computations were conducted to the rolled profile and the rolled shape of 1420CVC cold continuous mills, the influence of initial local high point and local hardness from hot rolling on the distributions of thickness and internal stress of cold rolled strip...