The reasons which improving the quality of aluminium metal and corresponding improvements were discussed on 70 kA HSS aluminium electrolytic cell with purified returns being main feed in Baotou Aluminium Co.

However,the size and amount of microporosity increase with the recycle material proportion,and the microporosity in 100% recycled alloy is much more than that in the virgin alloy.

The microstructures of the corrosive surface of the alloy molten in atmosphere using recycled alloy have been analyzed.

For alloy K444,the results show that the revert proportion increment induces the formation of microporosities,coars- ening of dendrite,gather of eutectics,agglomeration of carbides,as well as the augment of N content in the revert alloys.

The results showed that the relationship between length of main crack and thermal cycle index could be described as L=bN~a for both virgin and revert alloys.