Spheroidizing annealing furnaces are mainly used for hypereutectoid carbon steel and alloy equipment steels (such as steel cutting tools, measuring tools, and steel grades used in molds). The key objectives are to reduce hardness, improve machinability, and plan for future quenching. This process facilitates plastic processing and machining, as well as increases mechanical toughness. More and more about bearing steel, equipment steel and other steel grades, such as spheroidizing annealing before quenching, can achieve the following effects:
Bearing steel: uniform quenching effect; reduce quenching deformation; increase quenching hardness; improve workpiece cutting function; improve wear resistance and pitting resistance.
Equipment steel: uniform quenching effect; pressing quenching, quenching and other phenomena; increase wear resistance, sharp edge level and service life.
Usually spheroidizing annealing: the steel is heated between Ac1 and Ac3 (or Acm), fully insulated, and then slowly cooled to 500-600 ° C to be cooled. Usually used for spheroidizing annealing: pre-heat treatment for bearing parts, tools, cold work dies, etc.
Isothermal spheroidizing annealing: heating the eutectoid steel or hypereutectoid steel to Ac1+20～30°C (if the meshed carbide in the original structure is tighter, it needs to be heated to slightly above Acm). The temperature is slightly lower than the temperature of Ar1 until the austenite change is completed, and the furnace is cooled or air cooled. The use of isothermal spheroidizing annealing: commonly used in carbon steel and alloy steel equipment, cold work die steel and bearing parts.
Rapid spheroidizing annealing: The hypereutectoid steel is heated to Acm + 20 ~ 30 ° C, and then air-cooled (normalized) to obtain fine-grained pearlite. Then, spheroidizing annealing or isothermal spheroidizing annealing is performed. Rapidly spheroidized and annealed.
