Numerical Simulation Of Damage Suppression Of Magnesium Alloy Strip Casting Based On Position Control Of Solidification Welding Line

Magnesium alloys are widely used in aerospace and high-end motorcar fields because of their first-class specific tenacity and specific rigidity.The characteristics of magnesium alloy,such as poor plastic forming ability and difficult processing,have become the primary factor that impedes the development of magnesium alloy.Therefore,based on the actual situation of magnesium alloy casting and rolling production,combined with the theory of magnesium alloy rolling edge crack inhibition,this paper studies the magnesium alloy casting and rolling solidification welding line,and reveals the mechanism of the edge crack phenomenon.The main research contents are as follows:(1)Effect of core parameters of roll casting on solidification welding joint of neutral surface.Through the analysis,the following verdicts are drawn: The solidification weld joint moves toward the exit of the casting and rolling zone as the temperature increases(900 to 950 K).Solidification welding point shifts by2% every 10 K,and non-uniformity of slab heat distribution decreases slightly.(2)Study on the influence of casting rolling initial parameters on the feature of Kiss line.Through the analysis,the following verdicts are drawn: Change of casting and rolling process parameters will significantly affect overall melt flow in casting and rolling zone,thus affecting characteristics of solidification welding line.At the same time,the height of solidification welding line increases from21.5 mm to 24.7 mm;position difference between center and edge of solidification welding line along casting direction increases from 6.2 mm to 25.3 mm;The distance between the center position and the edge position of the solidification welding line along the casting rolling direction presents a downward trend,from27.5 mm to 17.3 mm.(3)The effect mechanism of solidification welding line on roll casting plastic forming process was analyzed.By comparing and analyzing the center and both ends of the cast rolled sheet,the mechanism of edge crack in magnesium alloy cast rolling was revealed.Through the analysis,the following verdicts are drawn:non-uniform melt flow in casting rolling zone is main reason for tongue shape of solidification welding line.Because the edge of the slab solidifies before the center of the slab,the actual rolling section of the slab forms a special rolling section with the edge height higher than the middle height.As a result,the actual rolling reduction of the edge is large.On the other hand,due to the low edge temperature of slab,and heat distribution of edge is more uneven.Through numerical simulation,stress of edge of cast rolling plate is about 50% higher than that of center,which is main reason for edge crack of slab.Tongue effect of solidification welding line can be effectively weakened by adjusting process parameters and changing nozzle structure,so as to restrain edge crack.