When the manufacturing of fastener objects and processing technology requirements are basically the same, the normalizing process is more green than the annealing process, which is mainly reflected in energy consumption and processing time.
Low temperature annealing (stress relief annealing): heating temperature <Ac1 carbon steel 550 ~ 650 ° C, eliminating the internal stress during upsetting and cutting process, so that it reaches a steady state.
Recrystallization annealing: heating temperature TR + 150 ~ 250 ° C holding time 0.5 ~ 1h air cooling, recovery and recrystallization process, so that the deformed grains are fine equiaxed grains, eliminating the cold hardening effect and internal stress. The low-carbon steel recrystallization annealing temperature is 600-650 ° C and the hardness is in the range of 75-90 HRB.
Incomplete annealing: heating temperature Ac1 + 30 ~ 50 ° C, carbon steel is generally between 700 ~ 750 ° C, refine the grain, reduce hardness, improve plasticity, remove internal stress.
Spheroidizing annealing: The heating temperature is slightly higher than Ac1. After long-term heat preservation, it is slowly cooled to less than 500 °C air cooling to make the carbide spheroidized, and the hardness can be improved to improve the cold upsetting performance.
Normalizing: low carbon, medium carbon steel heating temperature Ac3+ (50 ~ 70 ° C), low carbon steel to improve hardness, is conducive to cutting, medium carbon steel refinement of grains, uniform tissue destressing.
