Microstructrual Characterization of the Electromagnetic Stirred Al Alloys

摘要

Thixotropic Al alloy billet has been mostly produced in a continuous casting process utilizing an electromagnetic stirrer, which imparts the necessary motion to the melt in mould during solidification. The thixotropic characteristics of EM stirred billet are determined the size, morphology and distribution of primary crystal, which is affected by a lot of process parameters, i.e. the electromagnetic stirring and continuous casting conditions. In this study the effect of casting speed on microstructure was investigated to establish the quantitative relationship between microstructure and the process parameters in horizontal continuous casting process. A horizontal continuous casting apparatus utilizing electromagnetic stirrer was developed to produce the thixotropic Al alloy billet. An electromagnetic stirrer with a high electrical efficiency and a slim metal mold with a high cooling capacity were designed and developed for horizontal continuous casting process. Al alloy billet was fabricated in the horizontal continuous casting apparatus at a different magnetic flux density and casting speed. A depth of surface defect and a distance between the surface defects of the billet were decreased with increasing the casting speed and a very good smooth surface without any surface defect appeared on the billet produced at a casting speed of 600mm/min. A thickness of the solidifying shell was decreased with increasing the casting speed and the maximum casting speed to produce a sound billet without a breakout was 600mm/min in horizontal continuous caster designed in this study. Both the size and the aspect ratio of primary crystal were decreased with increasing the casting speed in the range of this study.