Thermal-flow-solidification Simulation In Twin-roll Casting Of Magnesium Alloy And Its Application On Analysis Of Strip Defects

Due to the good properties such as low density, high specific strength andspecific stiffness, good fluidity, high damping and good electromagnetic shieldabilities, magnesium alloy is widely applied in electronic, automobile, military andaviation industries. As a new material manufacturing technology, twin-roll castingtechnique has the advantages of both weight saving and energy saving. It becomesone of the frontier topics in materials and metallurgical fields. During a strip castingprocess, the molten metal solidified in a very short time, it is difficult to keep theprocess in a steady state, and this limits it to realize industrialization. So, studying theprocess parameters such as pouring temperature, casting speed, et al, deeply seems tobe very important to help to improving strip quality.In this paper, studying the process and parameters on a vertical type twin-rollcaster in University of Science and Technology Liaoning has been carried out.3Dthermal-flow numerical simulation has been established first. The influences of keyprocess parameters including casting speed, pouring temperature, nozzle types, poollevel, et al, are discussed. Optimized parameters from the simulation results areselected for experiments. Combining with the simulation results, analyses have beendone on the experiments to help us to optimize the process parameters. During thecasting process, the width of nozzle is shorter than that of the two rolls, and the flowof the molten metal is hindered by the two side-dams, these cause a non-uninformtemperature field and the thermal stress generated. According to the simulation results,the temperature gradient is different at different pool level, it decreases firstly andthen increases. With the increase of pouring temperature, the distribution oftemperature in the strip gets uniformly. If the superheat of the molten metal increasesproperly, the thermal stress could get down. But, this may causes a higher temperaturein the strip, and can easily get oxidized. The simulation results also show that, thetemperature in the strip could get more uniform with the increase of the casting speedas well. So, we can get a better as-cast strip in a higher casting speed. The fluctuationof the pool level causes the movement of the roll, and this will affect the strip quality.