The furnace in rolling mill is a device that heats the material or workpiece. According to the heat source, there are fuel heating furnace, resistance heating furnace, induction heating furnace, microwave heating furnace, and so on. Applications include petroleum, chemical, metallurgy, machinery, heat treatment, surface treatment, building materials, electronics, materials, light industry, daily chemical, pharmaceutical and many other industries.

The purpose of heating furnace is to heat the billet to the temperature that is uniformly suitable for rolling. After the temperature is increased, the plasticity of the steel is firstly increased, the deformation resistance is lowered, and the steel is easily deformed. For example, the deformation resistance of T12 steel at room temperature is about 600Mpa. When heated to 1200°C, the deformation resistance drops to about 30Mpa, which is only one-twentieth of the deformation resistance at room temperature.

Steel with suitable heating temperature can be used for rolling, which can reduce the equipment accident caused by wear and impact, improve the productivity and operation rate of the rolling mill, and reduce the rolling energy consumption. Second, heating can improve the internal structure and properties of the billet. The uneven structure and non-metallic inclusions are homogenized by the diffusion of high temperature heating. The heating temperature and uniformity are the marks of the heating quality. When the steel of good quality is heated, it is easy to obtain the finished product with the correct cross-sectional shape and accurate geometrical dimensions.

According to the furnace temperature distribution, the furnace is divided into preheating section, heating section and soaking section along the length direction; the furnace temperature at the feeding end is preheating section, and the function is to utilize the heat of the furnace gas to improve the thermal efficiency of the furnace. The heating section is the main heating section, and the furnace gas temperature is higher to facilitate rapid heating. The soaking section is located at the discharge end, and the difference between the furnace gas temperature and the metal material temperature is small, and the cross-section temperature of the discharged billet is uniform. The furnace for heating the small broken fabric blank has only the preheating section and the heating section. It is customary to divide the furnace section according to the supply of the burner in the furnace, and the furnace is called one-stage, two-stage type, even five-stage type, six-stage type, etc. according to the number of the supply to the tropics.

In the 1950s and 1960s, due to the increased capacity of the rolling mill, the length of the push-type furnace was not too long due to the length of the push-pull steel. Therefore, the supply of tropical water to the feed end was started, and the preheating section without heating was removed. Increase the productivity of the unit bottom area. The slab is heated by the furnace, and the output per unit area of the furnace bottom is 900-1000 kg/(m2·hr), and the heat consumption is about (0.5-0.65)×106 kcal/ton. Since the 1970s, due to the need for energy saving, and because the emerging stepping furnace allows to increase the length of the furnace, a preheating section without heating is added, and the optimum unit area per unit area is 600-650 kg/(m2·hr), the heat consumption is about (0.3 ~ 0.5) × 106 kcal / ton.