This term describes a heat treatment process that is a production process, whereby optimum material properties are achieved by equalization and subsequent cooling.
A differentiation is made between the following annealing processes:
Normalizing sually takes place after the hot working of components. The workpieces are heated somewhat above the hardening temperature and are then cooled.
Normalizing can be used to convert coarse-grained or non-uniform structures into fine structures.
Das Stress Relieving is intended to reduce the internal stresses in the workpiece during the microstructural transformation, cold forming, or thermal action. It usually takes place under long holding times at temperatures between 450 and 650°C and then much slower (!) Cooling so that significant changes in the material structure or its properties can be avoided.
In Softening (Annealing) too, slow cooling follows the treatment at temperatures below the lower transformation temperature. Here the intention is for the material structure to stay as soft as possible or a grain perlite formed, which ensures optimal working in non-cutting metal forming or machining with metal cutting.
Cementite Spheroidizing is the name for annealing on spherical cementite and also represents a softening annealing process, however, which achieves the highest possible carbide degree of reduction by means of cyclic annealing and subsequent, slow cooling, so that a material structure of cementite grains in a ferritic matrix forms, which can in turn be worked optimally. This process lends itself to subsequent cold massive forming.
Grain Coarsening also called full annealing, takes place at a temperature above the hardening temperature in combination with appropriate cooling, so that, as the name says, a coarser grain can be achieved. Furthermore, the aim is also to improve the machinability of the workpieces, which are exposed to immense metal cutting forming. The holding time must be sufficiently long to ensure the coarsening of the grain. The process functions with temperatures between 950 and 1,200°C. Since the required grain growth involves a worsening of the material properties, the structure must be transformed back into a fine-grained structure by hardening, quenching, and tempering, etc.
Homogenizing means annealing at very high temperatures in the (recrystallization zone) with the objective of partially or completely reversing the changes in material properties or structure resulting from the cold forming.
This process within the temperature range from 1,000 – 1,300°C enables the equalization of the differences in chemical composition of steels and cast materials caused by segregation, whereby transformation of the structure is precluded.
Solution Annealing is usually used for austenitic steels to dissolve precipitated constituents or to eliminate stresses following cold strain hardening. This process is carried out for treating iron with temperatures between 950 and 1,200°C, and non-ferrous metals in the range between 460 – 540 °C.
The aim is to achieve uniform or homogeneous material properties.