Metal Casting Technologies : MCT DEC 2018 (4TH QRT)
METAL Casting Technologies 4th Quarter 2018 25 TECHNICAL FEATURE Introduction ecycling of aluminium is the process of re-using scrapped aluminium. Whereas aluminium produced from its ores is primary aluminium, the recycled aluminium is also known as secondary aluminium. The process of recycling involves re-melting of the scrapped aluminium and casting into ingots or other valuable products. It is far less expensive and energy intensive than extracting primary aluminium from bauxite ore. Generally speaking, there are two types of Al scraps: new scrap and old scrap. The new scrap is that surplus material that is generated during the manufacturing and fabrication of Al alloys. The examples of new scrap are extrusion discards, turning and millings and other products of metal cutting. On the other hand, old scrap are that parts of Al that are recovered from Al components already produced, used and finally discarded for recycling. The examples of old Al scrap are Al beverage can, components from old aircraft, automobiles, bicycles, household appliances, window frame and electric conductor etc. These scraps are recycled, as secondary Al requires only about 2.8 kwh/kg of Al produced whereas primary Al production requires about 45 kwh/kg of Al produced. The recycling process of Al There are several steps in the recycling of Al scrap to transform it into ingots and other products. These are discussed below. 1. Collection of scrap Al Al beverage cans, Al foil and aerosol cans are to be collected from various sources such as homes, streets and garbage collection centers by hired persons or agents. Other heavy Al parts are collected from metal junkyard. These scrap Al is then transported to the treatment plant. 2. Sorting The mixed metals (aluminum and steel cans) are taken to a materials recovery facility where they are cleaned, sorted into different metal streams and the thin sheet Al products are compressed into bales. This step is very important in ensuring that the aluminum is separated from other metals, since some of the drink cans and certain food cans are made out of steel. Thicker parts are directly processed in magnetic separator. 3. Shredding The aluminum blocks bales are later transported to the shredder. The shredder then cuts the cans into tiny pieces. This is done to make it easier to get rid of all the paintings and coatings that are used for decoration and protection purposes. Additionally, it makes it easier for the metal to melt quickly in the furnace. 4. Magnetic separation This process aims at completely eliminating traces of steel. Since steel is magnetic, it is easy to separate it from aluminum once it is passed under a magnet. This ensures that the recycled aluminum contains no steel and meets the quality standards set. 5. De-coating The aluminum shreds then are taken by the conveyor system into a specialized decoater. This is where all the decorations R Recycling of aluminium and its alloys Dr P.C . Maity Metal Casting and Materials Engineer E: firstname.lastname@example.org THE PROCESS OF RECYCLING INVOLVES RE-MELTING OF THE SCRAPPED ALUMINIUM AND CASTING INTO INGOTS OR OTHER VALUABLE PRODUCTS. IT IS FAR LESS EXPENSIVE AND ENERGY INTENSIVE THAN EXTRACTING PRIMARY ALUMINIUM FROM BAUXITE ORE.
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