Hot Profile Extrusion of Aluminum Chips
A global reduction of CO2 emissions is becoming more and more important to prevent global warming caused by greenhouse gas production. Due to this, the need for a decrease in energy consumption in every field of industrial processes as well as transportation and production engineering is a major factor in today’s industrial world. In the area of cutting and forming technology, typically, the major amount of energy is not used for the manufacturing process, but for the production of the primary material, made from first melting after mining, or secondary material, made from melting after recycling. In case of cold or hot extrusion of steel, approximately 90 to 93 percent of the energy used is needed for the material production, 3 percent for thermal treatment, and only 1 percent for the forming process. Due to the energy consuming electrolytic production of aluminum, the amount of energy needed for the production process is even larger. These facts indicate, that from an economic and ecologic point of view reducing the production of primary material is the most efficient way to reduce energy consumption and, thus, CO2 production. An innovative process chain, combining optimized primary material usage and a reduction of process steps, is the direct conversion of aluminum by combining hot profile extrusion with subsequent turning or machining and, again, hot extrusion of the produced machining chips for semi-finished-parts (figure 1).
- Figure 1: Process chain
A major advantage of this process can be seen in an energy need of only 5 % compared to the conventional process chain including a re-melting step of the scrap to produce new extrusion billets. Furthermore, up to 95 % of the primary material can be used by avoiding an average metal loss of approximately 20 % during the re-melting phase by preventing intensive oxidation on the molten metal surface, burning and mixture with the slag removed from the surface of the ladle. Based on these advantages, the combination of machining and extrusion can lead to a reduction of energy needed for recycling from 16-19 GJ/t to 5-6 GJ/t. Although no final products have been presented, intensive studies comprising AlWx, AlMg2Wx and Al Cu4Wx proved that for the alloy used, relative densities and strength values up to those of solid materials could basically be reached. These works have shown that the principle of direct conversion of aluminum scrap offers a great economic and ecological potential for semi-finished products.