History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c13.s2.t4.101

v1.c13.s2.t4.101

During the operation of the furnace the bellows were worked at controlled pace to maintain the furnace temperature of 1000 to 1100°C.It took about 6 hours to complete one heat on small furnaces. During the last campaign of the heat the rate of air blowing was increased and a maximum temperature of 1500°C was achieved at the tuyere level. At this stage a small hole was made in the front wall to tap out the molten Fayalite slag. During this period the reduced sponge iron got consolidated in the hearth by partial fusion. The out flow of liquid iron-carbon alloy (C 2%) was considered to be a bad omen. After tapping out the final slag the tuyere and bellows were removed and the front wall was broken to take out the hot sponge iron block.