Complete annealing
Process: Heat the steel to 20~30℃ above Ac3, keep it warm for a period of time, and then slowly cool it (with the furnace) to obtain a heat treatment process close to the equilibrium structure (complete austenitization).
Isothermal annealing
Process: Heat the steel to a temperature higher than Ac3 (or Ac1), keep it warm for a suitable period of time, and then quickly cool it to a certain temperature in the pearlite zone, and keep it isothermally to transform austenite into pearlite, and then air cool it to room temperature.
Incomplete annealing
Process: Heat the steel to Ac1~Ac3 (hypoeutectoid steel) or Ac1~Accm (hypereutectoid steel), keep it warm, and then slowly cool it to obtain a heat treatment process close to the equilibrium structure.
Spheroidizing annealing
Process: Heat to 20~30℃ above Ac1, the holding time should not be too long, generally 2~4h is appropriate, and the cooling method usually adopts furnace cooling, or isothermal for a long time at about 20℃ below Ar1.
Diffusion annealing (homogenization annealing)
Process: A heat treatment process in which the steel ingot, casting or forging is heated to a temperature slightly below the solidus line, kept at that temperature for a long time, and then slowly cooled to eliminate the chemical composition unevenness.
Stress relief annealing
Process: The steel part is heated to a certain temperature below Ac1 (generally 500~650℃), kept at that temperature, and then cooled with the furnace.
