"DEVELOPMENT OF ALLOYED MALLEABLE. IRON CASTINGS

Abstract

The review of literature has indicated that although extensive data is available in case of plain carbon and chromium alloyed cast iron, practically little data is available in case of niobium, Copper and misch metal. In the present investi-gation the possibility of their use as beneficial addition to malleable cast iron has been explored from the standpoint of better structure, machtnability, better properties and economic consideration. The whole investigation was carried out with a view to develop standard production and annealing conditions in the case of alloyed cast irons. The mechanical tests include hardness, shear, compression and toughness under dynamic conditions. Chip thickness ratio, shear angle 0 and rate of metal removal were taken as indices for the quantitative measure-ment of machinability. The study was made under varying tempera-tures of malleabilization and rate of malleabilization was studied metallographically. It was established that copper addition decreases the time of malleabilization drastically and improves the machinability and mechanical properties. Larger saving in the unit cost was obtained from the standpoint of cost of raw material because of possibility of use of increased amount of steel scrap, cost of heat treatment and machining the finished product inclusive of cost of labour, power and tool. Beneficial effect of niobium addition to malleable cast iron was observed from mechanical properties and cost consideration. However, the alloy treated with misch metal was found to have superior mechanical properties, having machinability comparable with cast iron. An attemptwas made to correlate the mechanical properties, structure, machinability and production cost under varying alloying and malleabilizatioh conditions.