Heat deliverance is the primary role of a furnace. Numerous industrial processes require heat processing and this is exactly where furnaces are employed. Furnaces are nothing but closed and insulated chambers within which heat is generated and delivered onto loads enclosed within the furnace. Industries which deal with ferrous metals or with glass require very high temperatures for melting them. Very high temperatures are usually above 1260 degree Celsius. High temperatures are in the range of 1038 to 1260 degree Celsius. Mid-range temperatures are in the range of 593 to 1038 degree Celsius. Low temperatures are usually in the range lesser than 593 degree Celsius.
In the industry, shaping operations on the metal are usually carried out at high temperatures. Such high temperatures are maintained to soften the metal and make them manageable for the various processes like forging, rolling, bending, extruding, pressing, and so forth. The process of treating metals to change its crystalline structures, or otherwise to alter its surface compounds in a chemical manner are usually carried out in the mid-range temperatures. The treating process also involves relieving the strain in the metal, or hardening it, or altering its ductility so that it could be drawn into wires, and so forth. The various treating processes includes sintering, hardening, annealing, martinizing, spheroidizing, tempering, malleablizing, austenitizing, nitriding, carburizing, tempering, and aging. Polymerizing and drying are processes that are carried out under low temperatures.
Furnaces are extensively used by the steel industry, and it does not mean industries dealing with other metals do not use furnaces for their processes. Furnaces are used in very much the same way by other metal industries as industries dealing with steel. Hence most of the processes followed by the steel industry in the use of furnaces strongly applies to other metal industries too.
Furnaces lose much significance when dealing with temperatures below 650 degree Celsius, and in such cases they are referred to as ‘Ovens’ in some parts of the world, especially North America. There is a blur in the line dividing ovens from furnaces if temperature is taken into consideration. For instance, if ‘ovens’ were to be referred to as equipment providing heat below 650 degree Celsius, then Coke oven’s operating temperature is 1478 degree Celsius. Here there is no distinct demarcation between an oven and a furnace. In fact, furnaces are referred to as ovens in the European region. If the ceramic industry is taken into consideration, ‘kiln’ is what they use to denote a furnace. If the petroleum industry is taken into consideration, or industries which are referred to as the chemical process industries, then they refer to a furnace by the words like, destructors, kilns, incinerators, heaters, and so forth. In a different parlance, ‘furnace’ is what a boiler’s heat source is termed to be referred to as. However they are referred to by the industry, furnaces continue to serve their primary objective, which is nothing but the supply of heat!