Box-type resistance furnace. Its working principle is based on the use of electric current passing through heating elements arranged in the furnace chamber to heat the parts through current and radiation. It is a widely used heating equipment in heat treatment workshops. It is suitable for heating annealing, normalizing, quenching, tempering, and solid carburizing of ferrous and non-ferrous materials (non-ferrous metals). It has advantages such as simple operation, accurate temperature control, the ability to introduce protective gas to prevent oxidation of parts during heating, and good working conditions.
Pit-type resistance furnace. The working principle of the pit-type resistance furnace is the same as that of the box-type resistance furnace. Its furnace opening faces upwards, resembling a well, hence the name. Commonly used types include medium-temperature pit furnaces, low-temperature pit furnaces, and gas carburizing furnaces. Pit-type resistance furnaces use cranes to lift parts, reducing labor intensity, and are therefore widely used.
Medium-temperature pit furnaces are mainly used for heat treatment of long and thin parts, such as quenching, annealing, and normalizing. Their maximum operating temperature is 950℃. Compared to box furnaces, pit furnaces offer better heat transfer. A fan can be installed on the furnace top, resulting in more uniform temperature distribution. Vertical placement of slender parts overcomes the bending deformation caused by their own weight when placed horizontally.
Salt bath furnace. A salt bath furnace uses molten salt as the heating medium. Salt bath furnaces are simple in structure, easy to manufacture, inexpensive, provide good heating quality, and have a fast heating speed, making them widely used. However, heating in a salt bath furnace involves processes such as binding and clamping parts, which are complex, labor-intensive, and result in poor working conditions. They also have disadvantages such as long start-up time. Therefore, salt bath furnaces are often used for medium to small-sized parts with high surface quality requirements.
