Full Annealing:
- In full Annealing the steel is heated above the critical temperature and then cooled very slowly.
- In full Annealing steel is heated to its 500C above the austenitic temperature and held for sufficient time to allow the material to fully form austenite or austenite-cementite grain structure. The material is then allowed to cool slowly so that the equilibrium microstructure is obtained.
The Purpose of Full Annealing:
- to relieve internal stresses
- to reduce hardness and increase ductility
- for refining of grain size
- for making isotropic in nature in mechanical aspects
- for making the material having homogeneous chemical composition
- for making the material suitable for high machining processes
- to make steel suitable for undergoing other heat treatment processes like hardening, normalizing etc.
- the grain structure has coarse pearlite with ferrite or
cementite (depending on whether hypo or hyper eutectoid). The steel becomes
soft and ductile.
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