1. annealing
  2. The steel is heated to a certain temperature and at that temperature, and then slowly cooled to room temperature. Annealing has fully annealed, spheroidized annealing, stress relief annealing several.
  3. Normalizing
  4. The steel is heated to above the critical temperature 30-50 ℃, after holding the appropriate time, in still air cooling heat treatment process called normalizing. The main purpose of normalizing is to refine the organization, to improve the properties of steel, get close to the equilibrium state of the organization. Compared with normalizing annealing process, the main difference is normalizing cooling slightly faster, so the short production cycle of normalizing heat treatment. Therefore, when the annealing and normalizing parts to achieve the same performance requirements as the choice of normalizing.
  5. Quenching
  6. The steel is heated to a temperature above the critical point, to maintain a certain time, and then cooling at an appropriate speed in water (oil) heat treatment process to obtain a martensite or bainite structure called quenching. Quenching and annealing, normalizing the main difference is in the process of cooling fast, the purpose is to obtain martensite.
  7. Tempering
  8. After hardened steel, reheated to a temperature below the critical temperature, holding a certain time, and then cooled to room temperature heat treatment process called tempering. Steel after quenching generally can not be used directly, before use must be tempered. By tempering can eliminate or reduce stress, reduce the brittleness, improve toughness; on the other hand you can adjust the mechanical properties of hardened steel, to use the properties of the steel. Depending on the tempering temperature, tempering can be divided into low-temperature tempering, tempering temperature and tempering three.