Incomplete annealing is also called incomplete crystallization annealing, which refers to the process of heating steel to 30-50℃ above Ac1, keeping the temperature for a sufficient time, and then slowly cooling with the furnace. Since incomplete annealing is heated in the two-phase region, the structure cannot be completely recrystallized, the shape, size and distribution of ferrite cannot be changed, and the grain refinement effect is not as good as complete annealing. Therefore, incomplete annealing is mainly used for hypoeutectoid steel parts with normal ferrite distribution, but the forging and rolling termination temperature is too low, or the cooling is too fast, in order to reduce hardness, fire internal stress, and improve the structure.
If the final rolling termination temperature of hypoeutectoid steel is appropriate, it does not cause grain coarsening, and there is no abnormal distribution of ferrite and pearlite, incomplete annealing can be used to partially recrystallize, which can refine the grains, improve the structure, reduce the hardness and eliminate internal stress. The incomplete annealing temperature of hypoeutectoid steel is generally 740-780℃, which has the advantages of low heating temperature, good operating conditions, and saving fuel and time.
The purpose of annealing hypereutectoid steel is to refine and homogenize the structure, reduce hardness and eliminate internal stress.
seamless steel pipe
