The preliminary heat treatment of the girth gears produced by the steel casting manufacturers is the annealing or normalizing process. According to the actual situation, different heat treatment methods are used.
1. Adopt the normalizing treatment process for the low-carbon steel, a relatively uniform ferrite extraction and fine flake pearlite structure can be obtained.
2. Use annealing or isothermally annealing process for the medium carbon steel and alloy steel, ferrite and pearlite structures can also be obtained.
3. For the elimination of the casting stress, low temperature annealing process is also necessary.
4. Dendritic segregation will occur in large castings. Homogenizing annealing can be used, but the homogeneous annealing temperature is relatively high, and the structure will become coarse after processing. After homogenizing annealing, full annealing or normalizing is still required, to refine grains and improve mechanical properties, which can improve the processing performance, to prepare for the final heat treatment.