STRATEGIES TO REDUCE INCLUSION INPUT DURING LIQUID METAL TRANSPORTATION AND MELT DISTRIBUTION DURING DC CASTING OF AL ALLOYS

摘要

For the production of high quality rolling ingots, the quality of aluminum melts must be improved along the whole process chain (process layout discussed in [1]). Furthermore it is absolutely necessary to avoid re-entry of impurities after the last melt refinement step in the launder. The inclusion re-entry can be related to oxides which are generated by surface turbulences in the launder and the melt distribution system of the mould. The most critical phase is the start-up of the DC casting process, which leads to excessive oxide contamination. Finally, the melt distribution bag in the mould has a significant impact on the resulting ingot quality. This paper deals with a reliable methodology to investigate the inclusion input during casting with ultra sonic testing, PreFil and metallographic analysis, as well as strategies to reduce inclusion re-entry by improved melt flow in the launder. The paper also includes the presentation of special designs of melt distribution systems.