Electromagnetic Field Regulation Of AZ31 Magnesium Alloy Cast-rolled Solidification Welding Numerical Simulation Study On The Characteristics Of The Combined Line

Magnesium alloy is widely used in new energy vehicles,high speed rail,aerospace and other fields because of its low density,high specific strength and high specific stiffness.There are many ways to prepare magnesium alloy sheet and strip,among which the emerging technology of double-roll casting and rolling technology is developing rapidly,which can realize the continuous casting-rolling of sheet and strip,and the automation of sheet and strip production,but the current casting and rolling process of magnesium alloy still has the problems of uncontrollable fluid flow,uneven cooling rate,resulting in the bias of sheet and strip organization and low performance.In this paper,based on the technical bottleneck of edge cracking faced by magnesium alloy casting and rolling production,combined with the research results of the group on the phase of magnesium alloy rolling edge crack suppression theory,through the finite element simulation of multi-physics field regulation of magnesium alloy casting and rolling solidification weld line characteristics,focusing on the investigation of the influence mechanism of electromagnetic field on casting and rolling solidification weld line characteristics,to provide a basic theoretical model for the development and optimization of electromagnetic external field-assisted magnesium alloy casting and rolling process.The main research contents and conclusions are as follows:(1)By investigating the relationship between current density,casting and rolling speed,heat exchange of rolls and the matching of solidification welding point in the edge area of the casting and rolling zone.The results show that:In traditional casting and rolling,the position of solidification and welding point at the edge is the best position of embedded electrode plate in the side sealing plate.When the current density is constant,the electrode plate sectional area and current flux are different at different positions.When the current density increases from4×10~7 A/m~2 to 6×10~7 A/m~2,the maximum temperature in the casting and rolling area increases.When the current density increases by 4×10~6 A/m~2,the temperature of magnesium liquid at the electrode plate increases evenly,and the solidification welding point at the edge area shifts by 2%,and the temperature difference at the plate thickness direction decreases.When the casting and rolling speed increased from 1 m/min to 2.5 m/min,the temperature of magnesium liquid at the electrode plate decreased.When the casting and rolling speed increased by 0.8 m/min,the solidification and welding point in the edge region shifted to the roll gap by more than 10%.When the heat transfer capacity of the roller increases from 3000W/m~2K to 5000 W/m~2K,the temperature of magnesium liquid at the electrode plate increases,and the solidification bonding point at the edge area moves to the inlet from 55.1mm to 37.4mm,and the temperature distribution in the thickness direction of the solidification bonding point increases.(2)The relationship between current density,casting and rolling speed,roll heat exchange and full-plate width solidification weld line feature matching was investigated.The results show that increasing the current density,increasing the casting and rolling speed and decreasing the heat transfer coefficient will cause the overall shift of the solidification line towards the roll seam,changing the current density mainly affects the solution temperature and thus regulates the position of the solidification line,while changing the casting and rolling speed mainly affects the flow field distribution;By increasing the current density,the position difference between the center part and the edge part of the solidification weld line along the casting direction was reduced from 19.4 mm to 3.3 mm;by increasing the casting speed,the position difference increased from 1.5 mm to11.9 mm;by increasing the heat transfer coefficient,the position difference was maintained at 6 mm to 8 mm.By adjusting the three matching relationships,the"(?)"shape of the solidification welding line tends to"1"shape,avoiding the longitudinal uneven extension of the sheet through the roll seam and preventing edge cracking.(3)Study by matching the relationship between the applied magnetic field and the characteristics of the solidified weld line.The results show that:When the fluid flows into and out of the magnetic field,induction current and magnetic field in opposite directions are generated in the melt.Larger magnetic field will affect the flow field distribution of the high-temperature molten magnesium alloy.When a magnetic field is applied to a certain area of the casting and rolling area,the flow velocity of the fluid in the center surface of the plate thickness decreases twice.When the magnetic field intensity increases(0.9-1.4T),the flow velocity of the fluid in the center surface and the edge of the plate thickness in the magnetic field area is higher than that in the middle of the casting and rolling direction,and the difference between the two increases.The magnetic field strength increases(0-1.4 T),the solidification welding point at the edge of the casting and rolling area moves toward the roll seam,and the difference in position between the middle of the solidification welding line and the edge along the casting and rolling direction is reduced from 17.1 mm to 6.8 mm,which is conducive to the straightening of the solidification welding line at the center surface of the plate thickness.In this paper,based on the basic theory of electromagnetic field and flow field,we investigate the relationship between the electromagnetic field,casting and rolling process parameters and the matching of solidification weld line to achieve the synchronous solidification rolling of metal along the plate width and prevent edge cracking by precisely regulating the characteristics of solidification weld line.