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 a granular molded pearlite under the microscope which is the cause of the steal being softened. The process usually runs between only a couple of hours and – depending on the workpiece – up to a whole day.
A special type of soft annealing is GKZ annealing (Glühen auf kugeligen Zementit) where annealing is performed to obtain spherical cementite in the material structure.