Shell zone analysis of the aluminum alloys produced by means of semicontinuos casting

The "shell zone" is the inner part of the lamination plates close to the surface, it is characterized by a structural and chemical non-uniformity. The risk of gaseous inclusions caused by the solubilisation of hydrogen is significant in this volume. Industrial processes are aimed to reducing the thickness of the "shell zone" to lower it within a few millimetres so that it can be completely removed by the subsequent mechanical milling operation. The parameters that influence the formation of the "shell-zone" are: i) the alloy chemical composition, ii) the casting speed, iii) the amount of the metal in the mould, iv) the temperature, v) the water flow used for the plate cooling. In this study, the effect of the variation of some of the parameters above was evaluated to minimize the thickness of the "shell zone" for plates obtained from a semi-continuous casting of AA1200 e AA8006.