Tempering furnaces operate in several modes: continuous hot air tempering, hot air circulation tempering, and nitrate tempering. Each type of tempering furnace has its own application.
Continuous hot air tempering electric furnaces. This type of furnace has been widely used in the spring manufacturing industry in recent years. Its advantages include precise temperature and time control, and energy savings. If placed in front of a spring coiling machine, it can be used to create an automated production line for coiling and stress relief annealing.
Hot air circulation tempering electric furnaces and box-type electric furnaces. The furnace temperature is more uniform, but the holding time is much longer than that of nitrate tempering furnaces.
Nitrate tempering furnaces are generally built by spring manufacturers. The advantages of nitrate tempering furnaces are fast heating and shorter holding times than other furnaces. However, their disadvantages are uneven temperature, and the liquid inside the furnace tends to infiltrate the spring surface, which is particularly detrimental to oil-quenched and tempered spring wire. Therefore, springs treated in a nitrate tempering furnace should be rinsed with water and then immersed in anti-rust water for several minutes to prevent rust.
