The difficult with the annealing and normalizing
Annealing is the process of heating steel to a temperature at which it is kept warm and then slowly cooled to room temperature.
Annealing includes complete annealing, spheroidal annealing and stress relieving annealing.
- complete annealing occurs when the steel is heated to a predetermined temperature, held for a period of time, and then slowly cooled with the furnace. The aim is to reduce the hardness of steel and eliminate the uneven structure and internal stress.
- b. Heat the steel to 750 degrees, keep it warm for a period of time, slowly cool it to 500 degrees, and finally cool it in the air called spheroidal annealing. The purpose is to reduce the hardness of steel and improve the cutting performance, mainly used for high carbon steel.
- c. Stress-relieving annealing is also called low-temperature annealing. The steel is heated to 500 ~ 600 degrees, kept warm for a period of time, then cooled to below 300 degrees with the furnace, and then cooled at room temperature. The structure does not change during annealing, which mainly eliminates the internal stress of the metal
The heat treatment process of heating steel pieces to 30-50℃ above the critical temperature and cooling them in static air after proper insulation time is called normalizing.
The main purpose of normalizing is to refine the micro-structure, improve the properties of steel, and obtain the micro-structure close to the equilibrium state.
3.The difficult with the annealing and normalizing
Compared with annealing process, the main difference is that the cooling speed of normalizing is a little faster, so the normalizing micro-structure is finer than that of annealing, and its mechanical properties are also improved.
On the other hand, the production cycle of normalizing treatment is short, so when annealing and normalizing can also meet the performance requirements of parts, normalizing should be used as much as possible.
In addition, the outside cooling of normalizing furnace does not take up the equipment, and the productivity is high, so normalizing is adopted to replace annealing as far as possible in production.