Physico Chemical Aspects of Alumino-Thermic Reduction in the Production of Low Carbon Ferro-Alloys

Abstract

No doubt Carbon is the oldest, most extensively used and cheapest reducing agent for the extraction of metals, and ferro-alloys, but due to its high affinity for many metals it results in the formation of undersirable carbides. The growing demand of carbon free alloys has generated considerable interest in aluminothermic reduction of various .oxides. A common example of aluminothermic reduction is the thermit welding of rails and repair of steel castings. As early as in 1898, Goldschmidt (1) demonstrated the use of aluminium as a reducing agent in the production of refractory metals. Subscquently, alumino-thermic reduction has been extensively used to produce pure metals such as chromium, manganese and master alloys such as carbon free chromium-aluminium, titanium - alumin-ium, ferro-chrome, ferro-molybdenum, ferrocolumbium, ferro-tungsten and ferro-titanium of high purity. Alumino-thermic techniques have led to notable developments in the field of high purity special steels. The objective of aluminothermic reduction is to utilise the exothermic heat of the reaction for smelting purposes. Aluminothermic reduction did not generate much interest till 1950's due to various reasons such as high cost of pure aluminium and lack of available means for the removal of residual ele-ments and oxides. The interest in alumino-thermic reduc-tion , revived in 1960's and onwards. Since then extensive research work has been, carried out on aluminothermic reduction for producing low carbon ferro-alloys by obtain-ing 95-96% pure metals from their pure oxides and also metallic values from their oxides available as secondary sources.