Reprocessing of AW2007, AW6082 and AW7075 aluminium chips by using sintering and forging operations

Abstract

Since its discovery in the late Nineteenth century aluminium becomes an important construction material due to its good mechanical properties such as sufficient strength at low density. Additional advantages are high corrosion resistance as well as low manufacturing forces. Apart from this, aluminium is still very expensive to produce. The energy consumption of the production process is at least twice as much as for steel. Most of the energy consumption takes place at the electrolyse process while aluminium oxide (Al₂O₃)—recovered from natural bauxite—is divided into unalloyed aluminium named “primary aluminium” and CO₂. Contrary to the expensive production of primary aluminium the energy consumption of the recycling process of used aluminium also known as “secondary aluminium” is considerably lower. Given this huge effort in producing primary aluminium, the recycling of aluminium is an important economic and ecological approach. The common recycling method for aluminium is to melt it in a furnace. Except from small-sized scrap like chips, this is an overall efficient recycling method for most aluminium scraps. It can be observed that especially chips suffer high material losses mostly due to contaminants from the production process (cooling lubricant, oil etc.), fire losses (oxidation), slag and unadapted furnace settings. For this reason, several researches examine alternative recycling processes to avoid a melting process and minimize material losses. In this investigation a new non-melting aluminium recycling approach will be validated. For this purpose various chip pressings (turning, milling, sawing) are forged with an upsetting press. It will be shown that it is possible to generate a solid consolidation without pores in areas of high material movement. Furthermore, the effect of a previous sintering operation will be examined.