Year

2012

Degree Name

Master of Engineering

Department

Faculty of Engineering

Abstract

Magnesium alloy contains many superior mechanical properties including low density, high specific strength, good die casting performance and better shock resistance. It is extensively applied in the electronic, automobile, military and aviation industries. As a new material manufacturing technology, twin-roll casting not only produces the strip directly, but also improves magnesium alloy properties. Some important process parameters in twin-roll casting are difficult to be obtained in the experiment can be acquired using the numerical simulation.

In this study, the two finite element models are established, which classify as submerged and non-submerged ones according to the nozzle types. Inverse method was used to determine the boundary conditions between the roll and molten pool. The influences of key process parameters including the rolling speed, pouring temperature, submerged nozzle depth and nozzle spray angle are discussed and compared for different cases. The coupling of temperature-flow-thermal stress fields has been carried out in this study. Increasingly casting speed and pouring temperature, the higher strip outlet temperature and uniform temperature distribution can be observed in non-submerged models. Submerged nozzle depth change has a significantly influence on the outlet temperature destitution than the varied nozzle spray angles in submerged models. Furthermore, the raised temperature at outlet decreases the thermal stress of strip. It can avoid thermal cracks generated on the surface to improve the casting strip quality of magnesium alloy. The suitable key process parameters are obtained from the simulation data analysis.

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