1, annealing
The steel is heated to 30℃~ 50℃ above the critical temperature (the temperature that causes the internal structure change of steel within the solid range of steel), and then cooled slowly with the furnace temperature after proper heat preservation.
Its purpose is to reduce the hardness of the material, improve the plasticity, refine the structure and improve the mechanical properties and machinability. 2.
Heat the parts above the critical temperature, keep the temperature for a period of time, and then quickly cool them in water or oil. Due to the change of internal structure, the hardness and wear resistance of the material are improved, but the brittleness and plasticity of the material are also enhanced. Because the quenching temperature changes rapidly. Large quenching stress is formed inside the material, which will lead to deformation or cracking of the parts. Quenching cannot be used as the final heat treatment of parts, and proper tempering is usually needed to eliminate quenching stress.
Quenching can refine the structure, improve the hardness and facilitate cutting.
3, conditioning
Quenching and high temperature tempering are both quenching and tempering. Some important parts, especially those working under variable stress, such as connecting rods, gears and shafts, are often used.
Step 4 temper
Reheat the quenched parts to a certain temperature below the critical temperature, keep the temperature for a period of time, and then cool in the air. The higher the tempering temperature, the more the hardness and strength of the material decrease, while the plasticity and toughness increase significantly.