Incomplete annealing and complete annealing

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Incomplete annealing, also known as incomplete crystallization annealing, is a process of heating the steel to a certain temperature between AC1 and AC3 or AC1 and ACM, and cooling it down slowly after heat preservation, so that the steel structure undergoes incomplete recrystallization.

Complete annealing refers to the process of heating hypoeutectoid steel to 20 ~ 30 ℃ above AC3 and cooling slowly with furnace after heat preservation, so as to obtain a heat treatment process close to the equilibrium structure (pearlite structure), also called recrystallization annealing.

The main differences between incomplete annealing and complete annealing can be summarized from the following three points:

(1) Incomplete annealing is also called incomplete crystallization annealing. It is a temperature between AC1 and AC3 or AC1 and ACM in the heating channel of steel, which is cooled down slowly after heat preservation, so that incomplete recrystallization occurs in the steel structure.

(2) Incomplete annealing is to heat the workpiece to semi austenitizing for annealing, while complete annealing is to heat the workpiece to fully austenitizing for annealing.

(3) Incomplete annealing is generally used for hypereutectoid steel and hypoeutectoid steel, while complete annealing is generally used for hypoeutectoid steel only.

(4) In general, lamellar pearlite is obtained by complete annealing, while spherical pearlite is obtained by incomplete annealing.

Learn More: Vacuum Annealing Furnace