Study On Multi-field Coupling Analysis And Center-line Segregation Control Strategy In Magnesium Alloy Casting-rolling Process

Magnesium alloy is the lightest metal material in industrial application.It has excellent comprehensive characteristics and has great development potential in the fields of electronic information,aerospace,communication and so on.Twin roll continuous casting is a high-efficiency and short process near net shape magnesium alloy plate and strip preparation technology.It has always been a research hotspot and frontier in the field of magnesium alloy plate and strip preparation.However,it has strict requirements for process conditions.There will be serious uneven distribution of alloy elements and segregation in the central layer to form the central layer segregation defect.In the process of casting and rolling,the process parameters such as roll surface cooling coefficient,casting and rolling speed,roll gap and casting temperature have a significant impact on the formation of central layer segregation.In order to obtain appropriate process parameters to inhibit central layer segregation,this paper takes the inclined double roll casting and rolling process as the research object,and uses ANSYS FLUENT software to simulate the magnesium alloy double roll casting and rolling process:(1)Firstly,the solidification,heat transfer,flow and mass transfer behaviors in the process of twin roll strip casting and rolling are analyzed.The liquid-solid phase line,solidification latent heat and effective viscosity in the casting and rolling model are treated,and a two-dimensional finite element model suitable for the casting and rolling process of magnesium alloy is established.(2)The two-dimensional model is used to compare and study the different roll surface cooling coefficient,casting speed,casting temperature,temperature field,flow field,total solidification point position and the distribution characteristics of Al and Zn elements in the molten pool area under the roll gap.The causes of central layer segregation of cast rolling strip are systematically analyzed from the perspective of the combination of three fields,and the best parameters to inhibit central layer segregation are obtained.(3)Considering the influence of the side seal plate,a three-dimensional model is established to study the difference between the flow field,solute field and total solidification point in the width direction of the strip,and the characteristics of the molten pool area after the optimization of the side seal plate are analyzed.(4)The actual AZ31 B magnesium alloy cast and rolled strip is analyzed by metallographic structure and the content of solute elements Al and Zn.It is compared with the results of the established finite element model to verify the correctness of the simulation results.