A heat treatment furnace refers to an electric or fuel-fired furnace used for heating materials during heat treatment. Common types include box-type resistance furnaces, pit-type resistance furnaces, gas carburizing furnaces, and salt bath furnaces. Continuous furnaces are widely used—workpieces enter through the loading door, move through the chamber, and exit continuously from the discharge side. Typically, parts are placed on heat-resistant steel rails and transferred by a stepping beam or push-rod mechanism. In recent years, heat-resistant steel conveyor belts have increasingly been used, making furnace operations more efficient and greatly improving automation and the possibility of unattended processing.
Because heat treatment processes and workpiece shapes vary widely, the furnace structures and furnace types are also diverse. Heat treatment furnaces can be classified in multiple ways, with each classification highlighting different characteristics:
Classification Methods
(1) By mechanical operation method:
- Roller-hearth furnace
- Walking-beam furnace
- Bogie-hearth furnace
- Mechanized chamber furnace
- Chain furnace
- Rotary-hearth furnace
- Vibrating-bed furnace
- Bell furnace
(2) By maximum temperature:
- High-temperature furnace: above 1000°C
- Medium-temperature furnace: 650–1000°C
- Low-temperature furnace: below 650°C
(3) By main heat treatment process:
- Solution treatment furnace
- Quenching furnace
- Normalizing furnace
- Tempering furnace
- Annealing furnace
- Chemical heat treatment furnace (e.g., carburizing)
(4) By production mode:
- Batch (periodic) furnaces
- Continuous furnaces
(5) By heating method:
- Direct heating (e.g., open flame furnaces)
- Indirect heating (e.g., radiant tube furnaces, muffle furnaces)
(6) By heat source:
- Fuel-fired furnaces (coal, oil, gas)
- Electrically heated furnaces (resistance furnace, electrode furnace, induction heating furnace)
(7) By heating medium:
- Gas medium (air, flue gas, controlled atmosphere, vacuum)
- Liquid medium (molten salt, molten lead)
- Solid medium (fluidized particle furnace)