Molten metal is prepared in a variety of furnaces, the choice is determined by the quality, quantity and throughput required.
♦ electric induction furnaces are the most common type used for batch melting ferrous, copper and super alloys. In this method involves the use of an electric current surrounding crucible that holds the metal charge. Furnace sizes range from <100 kg up to 15 tons. For the production of super alloys and titanium, may melt in a vacuum chamber to prevent oxidation.
♦ cupola used solely by iron foundries for continuous production of molten iron. Cupola consists of a bed shaft coking established. Metal, coke and limestone are charged alternately into the furnace from the top. Trickles through the bed of molten metal picking up carbon coke required, although impurities reacts with the limestone to form slag waste. Both metal and slag tapped continuously out at the bottom. Metal throughput of 1 to 45 tonnes per hour to reach the UK.
♦ electric arc furnaces are still used by some UK ferrous foundries, mainly producing, although most have been replaced by induction furnaces. Furnaces are 3-100 tons of capacity in use in the UK. Involves the design used in a bath holding electrodes are inserted. The heat generated causes a charge between the electrodes creating the metal to melt.
♦ Rotary furnaces are relatively rare in the UK but is used in some iron foundries. The furnace consists of a horizontal cylindrical steel shell mounted on rollers and lined with refractory material. The furnace is fired using gas or oil from one head and the body is rotated slowly furnace during melting.
♦ shaft and resistance Gas-fired furnaces used for melting aluminum. A shaft furnaces provide a continuous melting and cracking ability, useful at high production facilities. Resistance furnaces employed to melt the small batches.
♦ Gas and oil-fired crucible furnaces used for melting small batch of copper and aluminum alloys, although oil-fired units as popular now and tend to be limited to smaller foundries. Unlike the main furnace containing molten metal tapped into a ladle for solutions, the crucible is lifted out (or pops out) the heating chamber and the molten metal can be poured directly into the mold.