Soft Annealing

This annealing process softens the material or makes it easier to be machined. Moreover, soft annealing can be applied to further reduce stresses in the material if stress relieving is not sufficient and to reduce the possibility of cracks during potential hardening treatments.

After this thermal process, the treated steels should have a granular moulded pearlite under the microscope which is the cause of the steel being softened. The process usually runs between only a couple of hours and – depending on the geometry – up to a whole day..

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Solution Annealing 

Solution annealing is a special annealing process that is mainly used for austenitic steels. It serves both to hold constituents in a solid solution and to remove tension.

Like annealing in general, solution annealing consists of 3 phases: heating, holding and cooling. In the case of ferrous materials, the solution temperature is in the range from 950°cto 1200°c. In contrast, the temperature during solution annealing of non-ferrous metals is significantly lower, usually between 460°c and 540°c.After heating and holding, the material is cooled quickly to room temperature. This process takes place using a special cooling gas.

Due to solution annealing, homogeneous material and structural properties can be achieved. Solution annealing is therefore often used as an intermediate treatment. In addition, solution heat treatment is used exclusively to improve the properties of solid solution strengthened alloys.


This annealing process is applied to improve irregular, coarse and inhomogeneous grain structures in, for example, castings, forgings or rolled sheet. This improves the mechanical properties of the material by obtaining a fine-grained structure with grains of roughly equal size and a round shape.

To achieve those results, the material is usually brought up to temperature quickly and held at the target temperature for a certain amount of time. This time at temperature and the temperature itself will vary and is dependent on the base material. Once the material is fully austenitised, cooling needs to take place.

It is of great importance – and in contrast to the hardening in which a rapid cooling (quenching) is required - to force steel to transform into a martensite structure – which in normalising, the cooling occurs in a slow and controlled manner. This will result in a ferrite and pearlite structure for hypoeutectoid steels and a structure of pearlite and cementite at the grain boundaries for hypereutectoid steels.

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