Research On The Strip Element Method Of Three Thermo-Mechanical Coupling Of Plate And Strip Rolling And Development Of The Simulation System

Iron and steel industry is one of basic industries in national economy, and the hot rolled plate and strip as one of main steel products, which have high technology content and high attached value, its output and proportion reflects the steel industry level of nation. Impelling our nation from Great Power to Powerful Nation must only depend on the science and technology advancement and innovation. So the three dimensional deformations theory of the hot rolled plate and strip becomes the leading topic of development in point, and how to develop the high precision heat-deformation mathematic control model of the hot rolled plate and strip, which holds the independent intellectual property, becomes the important means to instruct production effectively and improve product quality remarkably.First, aim at the complicated temperature varieties of the plate and strip and the roll in the hot continuous rolling, starting with the boundary conditions, the transient temperature field models of the roll and the plate and these coupled model are built by the finite difference method. In the rolling zone, considering the water cooling, the deformation heat, the friction heat and the heat conduction et al, the three dimensional transient temperature field model of the plate and strip on mapped coordinate and the varying step length transient temperature model of the roll with the dynamic boundary conditions are built respectively. In the non-rolled zone, mainly considering the descaling cooling, the heat radiation, the water cooling and the air cooling et al, the cross section transient temperature distribution of the plate and strip is calculated by the two dimensional temperature fields. The simulation samples of 1580 mm and 2050 mm hot continuous rolling show that the temperature fields realized three dimensional high precision dynamic temperature field analysis of the plate and strip and the roll in the rolling process, and the temperature variety of the plate and strip of the whole finish rolling process and the transient temperature variety of the roll when air cooling after stopping rolling are accurately forecasted. The calculated values are fitted with the measured values well. Second, the B spline strip element method for simulating three dimensional rolling process of the plate and strip is put forward. The distributions of the exit lateral displacement and the exit altitudinal displacement are express as two B spline surface functions respectively, so the deformation of the exit cross section of the plate and strip can be simulated. And the lateral distributions of the entry and exit thickness of the plate and strip are fitted by the B spline curve functions, so the local high points or the edge decrease can be fitted well. Application of the B spline simplifies the complicated deduction process of the strip layer method (SLM) and the stream surface strip element method (SSSEM), and avoid the error resulted from the mapped coordinate. The locations of neutral points is varied along the lateral direction and calculated according to each strip element, so the three-dimensional asymmetric deformations process of the plate and strip is simulated more factually. In addition, the mixing optimum arithmetic of the floating-point genetic algorithm and the Powell algorithm is used, which ensures the whole and local optimal value. And, through looking for the control points of B spline, the calculation error and the instability of counting process, which are made by the spline interpolation method, can be reduced when the strip element is divided so many that the curves or the surface fluctuate seriously. Compared with the SLM and the SSSEM, the B spline strip element method can accurately analyze the deformation state of the exit cross section of the plate and strip and the effect of the local high points or the edge decrease to the metal deformation, and also realize the multivariate global optimization, so the calculation precision and the stability are improved. The simulation for the 1450 mm 4-high 6 stand hot continuous rolling shows that the calculated values are fitted close the measured values and proves the validity of this new model. Therefore, the range of application of the strip element method is enlarged and its engineering practicality is improved.Third, from the conducting heat mechanism of the plate and strip, the three dimensional temperature field models on the mapped coordinate are built. Coupled with the deformation field model by using the flow stress model, the three thermo-mechanical coupling model of the strip element method (SEM) is built. The model improves the theory of SEM, reducing the simplified conditions and the simplification, so the many fields such as the stress, the strain, deformation resistance and the temperature and so on can be determined in the hot rolling process. The simulation of the thermal-mechanical coupling for the 1450 mm 4-high 6 stand hot continuous rolling shows the distributions of the deformation and the unit roll pressure etc accord with the industry practice, while considering the temperature.Lastly, coupled the thermo-mechanical coupling strip element model and the roll system elastic deformation model, and integrated with the microcosmic structure model, the hot rolling simulation system software is programmed. It can be used to predict the hot deformation of the plate and the roll and the evolvement process of the microcosmic grain. Using this system software, the research on the 2050 mm 4-high CVC hot continuous rolling mill is taken. The calculated values is fitted close the results industry experimentation, that illuminates this system can simulate the locale operating condition.