Full annealing

Is the process of slowly raising the temperature about 50 ºC (90 ºF) above the

Austenitic temperature line A₃ or line A_CM in the case of Hypoeutectoid steels (steels with <

0.77% Carbon) and 50 ºC (90 ºF) into the Austenite-Cementite region in the case of

Hypereutectoid steels (steels with > 0.77% Carbon).

It is held at this temperature for sufficient time for all the material to transform into Austenite or

Austenite-Cementite as the case may be. It is then slowly cooled at the rate of about 20 ºC/hr (36

ºF/hr) in a furnace to about 50 ºC (90 ºF) into the Ferrite-Cementite range. At this point, it can be cooled in room temperature air with natural convection. The grain structure has coarse Pearlite with ferrite or Cementite (depending on whether hypo or hyper eutectoid). The steel becomes soft and ductile.