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Metal Casting Technologies : March 2011
34 www.metals.rala.com.au TECHNICAL FEATURE Introduction he developments in nuclear, aerospace & automotive engineering demands materials with improved mechanical properties and service reliability. Electroslag remelting (ESR) helps meet these stringent demands. Electroslag remelting (ESR) and vacuum arc remelting (VAR) are the two commonly used remelting processes. While both these processes can eliminate most of the in homogeneities and defects associated with the solidification process, their refining abilities are different. The equipment and operating costs of vacuum arc remelting are higher than the ESR process. It is a well known fact that ESR process produces high quality clean steels by improving the mechanical properties and eliminating inclusions. There is little published information available on ESR processing of aluminium and its alloys. The success of ESR of steels and super alloys has led to the interest in its application to non ferrous metals and alloys. High strength aluminium alloys which are used in aerospace applications would be benefited from the ESR process. In this experimental investigation ESR process is carried out on aluminium and its properties are determined. Conventionally cast aluminium has defects like porosity, segregation and pipe formation. In the ESR process these defects are eliminated. The process ESR process involves remelting of an electrode which is refined through a layer of molten slag. The metal to be refined is called an electrode. It can be cast or wrought and is known as consumable electrode. The electrode is melted by feeding its bottom end into a molten superheated slag layer. The slag temperature is higher than the melting point of the metal. The droplets of metal melting from the tip of electrode pass through the slag layer and join the molten pool of metal below the slag. The slag dissolves the inclusions from the molten metal and reacts chemically with the molten drops passing through it. Figure 1 shows the schematic diagram of the ESR process. A water cooled mould holds the forming ingot and the slag. The heat required to maintain the slag layer in a molten condition Foundry processing of aluminium chips by Electroslag Remelting Amit Joshi Dept. of Metallurgical Engineering & Materials Science, Indian Institute of Technology -- Bombay, India. Email: email@example.com T Figure 1. Schematic diagram of the ESR process CONVENTIONALLY CAST ALUMINIUM HAS DEFECTS LIKE POROSITY, SEGREGATION AND PIPE FORMATION. IN THE ESR PROCESS THESE DEFECTS ARE ELIMINATED.