In open hearth furnace, pig iron, steel scrap etc. are melted to obtain steel. This furnace is widely used in American foundries for steel production. The hearth is surrounded by roof and walls of refractory bricks as shown in Figure . The charge is fed through a charging door and is heated to 1650°C mainly by radiation of heat from the burning of gaseous fuels above it. This heat is obtained by the burning of sufficiently pre-heated air and gas. Such pre-heated air of gas is obtained by passing them though arc shaped hot regenerators at a lower level. This contains fire bricks which are arranged to extract heat from exhaust gases. In the furnace air and fuel are passed through a honeycomb of hot firebrick, called checkers. It preheats the air and fuel so that they are ready for combustion when they enter the hearth. The products of combustion at the same time pass through the checkers at the other end of the furnace. The hot gases heat the checkers. The process then reverses itself, and the newly heated checkers now are used to heat the air and the fuel. It is said as a regenerative process. The products of combustion after giving up their heat to the checkers pass up through the stack. On firing of coke, the charge is heated. Part of the heat necessary, results from radiation from the low hot roof of the chamber. The furnace is raised bricked in with the charging platform, at the rear, also raised so that the charge may be put into the furnace. The melt is tapped off the front into large ladles.