Annealing in vacuum
Annealing heat treatment is a process where the parts are heated up and then cooled slowly down to obtain a softer structure of the part and to optimize material structure for subsequent forming steps.
Generally speaking, all kinds of annealing processes can be provided by ALD’s HTS division. When annealing under vacuum the following benefits are provided in comparision with treating under atmosphere:
- avoiding intergranular oxidation (IGO) and surface oxidation
- avoiding de-carburized areas
- metallic, blank surfaces
- clean surfaces of parts after heat treatment, no washing of parts necessary
The most popular annealing processes are:
Stress-relief annealing is performed at temperatures about 650°C aiming to reduce the inner stress of the components. These residual stresses are caused by prior process steps such as casting and green machining operations.
Residual stresses can lead to unwanted distortion during the heat treatment process especially for thin-walled components. Therefore it is recommended to eliminate these stresses before the “real” heat treatment operation by stress-relief treating.
Recrystallisation annealing is needed after cold forming operations to gain back the initial microstructure.
Other treatments such as:
- Precipitation hardening or
- Solution annealing
are offered as well by ALD’s HTS division.