HANS – Recycling of aluminium chips

The purpose of the project was to test and evaluate methods to increase the internal use of chips in order to minimize transport and avoid additional remelting. The goal is to achieve equivalent mechanical properties to the cast component currently. The methods to achieve this goal were initially a literature study followed by briquetting trials and casting trials.

Centrifugation of chips before briquetting has not affected the final moisture content in the briquettes. Pre-drying at elevated temperature has also no effect on the final result. The pressing of briquettes drives out so much cutting fluid that no difference in the moisture content of the briquettes has been measured regardless of whether the chips have been centrifuged or not.

In experiments with the addition of briquettes to a small melt (10 kg), the amount of inclusions increased significantly as the relative amount of briquettes increased from 10% to 20%. Even in full-scale experiments with a larger melt (850 kg), a clear difference was seen in terms of inclusions between a reference melt and after the addition of about 8% briquettes. After degassing the melt with added briquettes, however, there is a considerable reduction in the amount of inclusions, both in terms of number and size.

The addition of briquettes produces a noticeable difference in density of the cast material. Degassing and proper slagging significantly reduced the amount of porous inclusions and gases, even in comparison with the reference melt without briquette addition. This is also confirmed in studies of fracture surfaces where the deviations that occur are at a microscopic level.

In the full-scale melt, no direct differences in mechanical properties between the reference melt and the melt with added briquettes have been detected, neither before nor after degassing. Based on this work, it seems that the addition of chips in the form of briquettes can be a good and manageable solution from a sustainability perspective, not negatively affecting the resulting cast material. However, further tests should be conducted to verify this, especially for material applications with higher requirements.