Research On Roll Temperature Field Simulation And Spray Cooling Control Of Thermal Crown For Four-High Aluminum Cold Rolling Mill

The work roll's thermal shape is an important influence factor for the strip flatness and profile,its influence factors are various and the boundary conditions are complicated,and it is a weak point in the area of strip shape theory.Therefore,the research on roll's temperature field and thermal crown control is of great importance in strip shape theory and practical production.The axisymmetric simulation model of work roll's temperature field is established to take the alternating heat load boundary and the complex whole 3D transient roll temperature field into consideration.The heat laod boundary equations of Phase Shift Method in the time domain based on the periodic dynamic thermal load and of the Circumferentially Average Method are provided.The rolling force is studied using the model of thin cold rolled aluminum strip based on mixed friction theory which contains adhesion area.Comparison of calculation examples and measurements indicate that the model based on mixed friction is suitable for the calculation of thin cold rolled Aluminum strip.The calorific value calculation formula of deformation heat and frictional heat in the rolling area are established based on the roll force model of mixed friction.Parameters of heat load on boundary of work roll are analyzed.The axisymmetric simulation model of temperature field is established by using the finite element analysis software ANSYS and the programming language APDL.The simulation software of rolls' thermal behavior were programmed based on Phase Shift Method in the time domain and Circumferentially Average Method respectively.Taking 1600 aluminum cold rolling mill as an example,the dynamical change of the transient temperature field and thermal crown curve of roll are analyzed.The wider the strip,the smaller the difference of temperature and thermal expansion in the axial direction.The comparison between simulation results and measured values indicate that the simulation model established is reliable.The Phase Shift Method in time domain has the advantage of calculate more accurately while Circumferentially Average Method has the advantage of compute more faster.The shape control principle and architecture of cooling system of 1600 four-high aluminum cold rolling mill are analyzed,and the control effects on thermal crown of roll of basic cooling mode are studied.The research shows that adjusting the basic cooling flow rate can change the secondary-order crown and fourth-order crown simultaneously,and the latter will reach into saturation when the flow rate is large enough.Analysis of local cooling simulation and control effect on thermal deformation of roll in quarter position and edge position show that thermal deformation changes caused by local cooling nearby cannot be ignored.The control model with sophisticated cooling is established,the method for constructing thermal effect matrix is presented,and the flow rate allocation strategy of differential cooling for correcting quarter buckle and local high spot shape defects are provided.The results of temperature field simulation and differential cooling control of thermal crown provide theoretical foundations for accurate forecasting of thermal behavior and differential cooling control of higher order strip shape defects.