pit furnace heating billet of purpose

The purpose of heating billet in pit furnace is an important link in the hot working process of billet

The heating of billet before rolling or forging is an important link in the hot working process of billet. The purpose of heating billet in pit furnace is:

Improve the plasticity of metals

Make the inside and outside temperature of the billet even

Change the crystalline structure of the metal

The quality of billet heating directly affects the quality, output, energy consumption and the life of the mill. The correct heating technology can improve the plasticity of metal, reduce the deformation resistance during hot working, provide the steel billet with good heating quality according to the production rhythm, and ensure the rolling mill production smoothly. On the contrary, such as improper heating process, or pit furnace work with bad, will directly affect the mill production. For example, if the heating temperature is too high, the steel will overheat and burn, and the rolling will result in waste products. Serious oxidation or decarbonization of steel surface will also affect the quality of steel, or even scrap. At present, some mills can not play a full role, often because the heating process of this link is weak.

The correct choice of metal heating process, not only to consider whether the metal heating temperature meet the requirements, but also should consider the temperature difference on the section, namely the uniformity of temperature. The heating system of steel before pressure processing and during heat treatment can be divided into one-stage heating system, two-stage heating system, three-stage heating system and multi-stage heating system according to the change of temperature inside the furnace. Our research object adopts multi-stage heating system. The multi-stage heating system is to heat the steel in four different sections (or periods) with different temperature conditions, namely, the preheating section, the first heating section, the second heating section and the soaking section. Multi-stage heating system is a perfect heating system, which combines the advantages of various heating systems. At first, the billet is preheated in the low-temperature area. In this case, the heating speed is relatively slow and the temperature stress is small, which will not cause danger. When the core temperature of the metal exceeds 500℃ and it enters the plastic range, it can be heated rapidly until the surface temperature rises rapidly to the required temperature from the oven. At the end of the heating period, there is still a large temperature difference on the metal section, which needs to enter the soaking period. At this time, the surface temperature of the pit furnace steel basically does not rise, but the central temperature gradually rises, reducing the temperature difference on the section.