Alternative charge materials: prospects & availability

Abstract

Electric arc steel making in India initially started with dual purpose of making essential steel castings and to produce pencil ingots for making merchant sections for building industry. The furnaces adopted double slag process. The productivity and the production were never critical at that time. Heat treated steel castings were very scarce in the country and the casting makers could ask for fabulus price for the product. Casting makers never felt any problem of charge because the yield of steel castings was never more than 55% and therefore 45% scrap was available to them from their own returns. The gap between selling cost and production cost being high they could manage the inputs at preferential prices. To quote an example in the present days steel castings are selling anywhere from Rs. 40 to Rs. 60 per kg. cast with ordinary methods. The same becomes Rs. 250/- to Rs. 450/- per kg. if they arc precision cast. The bulk of castings manufacture even till date is around 0.25 million tonnes an year. Picture for the steel ingots required for forging is noway different. Forging ingots have strigent requirement of quality. Forging process requires quality ingots with gases like H. 0, N below prescribed limits with inclusions at minimum. Forging requires a careful reheating cycle before the ingot is sent for forging. The ingots higher than ST weight are essentialy given vacum treatment to bring down gases and inclusions within prescribed limits. In reheating prolonged anti flaking cycle is given. The final heat treatments are also cumbersome. All these make forgings scrace and difficult. The selling price being in the range of Rs. 60/- to Rs. 125/ - per kg. the impact on charge materials can be absorbed.