In the foundry, there are cupola, induction furnace, resistance furnace, industrial furnace, electric arc furnace, vacuum furnace, open hearth furnace and crucible furnace for melting metal; there are sand mold drying furnace, ferroalloy drying furnace and casting annealing furnace for baking sand mold; in the forging workshop, there are various heating furnaces for heating ingots or billets before forging, and heat treatment furnaces for relieving stress after forging; in the metal heat treatment workshop, there are many kinds of heating furnaces for baking sand mold, There are various annealing, normalizing, quenching and tempering heat treatment furnaces to improve the mechanical properties of workpieces; in the welding workshop, there are pre welding preheating furnace and post welding tempering furnace for weldments; in the powder metallurgy workshop, there are sintering metal heating furnaces, etc. It is applied in other industries, such as metal smelting furnace, ore sintering furnace and coke oven in metallurgical industry; distillation furnace and cracking furnace in petroleum industry; gas producer in gas industry; cement kiln and glass melting and annealing furnace in silicate industry; baking furnace in food industry, etc.

With the appearance of coreless induction furnace, cupola will be replaced gradually. The melting work of the induction furnace is not limited by any grade of cast iron. It can quickly transfer from melting one grade of cast iron to melting another grade of cast iron, which is conducive to improving the quality of molten iron. Some special alloy steels, such as ultra-low carbon stainless steel, roll and steam turbine rotor, need to refine the molten steel from open hearth furnace or general electric arc furnace by vacuum degassing and argon stirring in refining furnace, so as to further refine high-purity and large capacity high-quality molten steel.

Flame furnace has a wide range of fuel sources and low price. It is convenient to adopt different structures according to local conditions, which is conducive to reducing production costs. However, flame furnace is difficult to achieve accurate control, causing serious environmental pollution and low thermal efficiency. The characteristics of electric furnace are uniform temperature, easy to realize automatic control and good heating quality. According to the way of energy conversion, electric furnace can be divided into resistance furnace, induction furnace and electric arc furnace. The heating capacity of the furnace calculated by unit time and unit bottom area is called furnace productivity. The faster the heating rate of the furnace and the larger the load of the furnace, the higher the productivity of the furnace. In general, the higher the furnace productivity, the lower the unit heat consumption per kilogram of material. Therefore, in order to reduce energy consumption, full load production should be carried out to improve furnace productivity as much as possible. At the same time, automatic proportional adjustment of fuel and combustion air should be implemented for combustion device to prevent excess or insufficient air. In addition, the heat loss from the opening of the furnace, the heat loss from the wall and the radiation loss from the flue gas should be reduced.