In order to make metal workpieces have the required mechanical properties, physical properties and chemical properties, in addition to the reasonable selection of materials and various forming processes, heat treatment processes are often indispensable.
Heat treatment of metal materials is a process that uses appropriate methods to heat, preserve and cool solid metals or alloys to change the internal structure of the material, thereby improving the properties of the material. It is called heat treatment.
Heat treatment generally does not change the shape and overall chemical composition of the workpiece, but gives or improves the performance of the workpiece by changing the microstructure inside the workpiece or changing the chemical composition of the workpiece surface. Its characteristic is to improve the intrinsic quality of the workpiece, which is generally not visible to the naked eye. The function of heat treatment is to improve the mechanical properties of materials, eliminate residual stress and improve the machinability of metals.
Relieve stress, improve cutting, reduce hardness (cooling in furnace)
Fast cooling (cooling in air)
Increase hardness, toughness, and plasticity. (cooled in water or oil), must be used with tempering.
Improve toughness
Tempering includes low temperature tempering, medium temperature tempering and high temperature tempering.
Low temperature: the internal stress is reduced, the brittleness is reduced
Medium temperature: improve elasticity and strength
High temperature: improve overall performance.
Tempering = quenching + high temperature tempering.
Classification of heat treatment furnaces | ||
Principle of classification | Heat source | Operating temperature |
Furnace profile | Resistance furnace Fuel furnace Gas stove Oil stove Coal stove | High temperature furnace (>1000℃) Medium temperature furnace (650~1000℃) Low temperature furnace (<650℃) |
Principle of classification | Furnace condition | Process use |
Furnace profile | Box-type furnace Pit furnace Bell furnace Through furnace Rotary hearth furnace Tubular furnace | Annealing furnace Quenching furnace Tempering furnace Carburizing furnace Nitriding furnace Experimental furnace |
Principle of classification | Mode of operation | Medium used |
Furnace profile | Batch furnace Continuous furnace Sphygmatic type Continuous type | Air medium furnace Flame furnace Controlled atmosphere furnace Salt bath furnace Oil bath furnace Lead bath furnace Fluidized furnace Vacuum furnace |
Principle of classification | Mechanical form | Control form |
Furnace profile | Trolley type furnace Elevating bottom furnace Push-rod furnace Conveyor belt furnace Roll-bottom furnace Vibrating bottom furnace Walking furnace | Temperature control furnace Process control furnace Computer simulation control furnace |