Heat Treatment of Precision Steel Casting

Heat Treatment of Precision Steel Casting

Heat Treatment of Precision Steel Casting

1. Annealing: Annealing is to heat the steel castings to 20 to 30 degrees Celsius above Acs, which is suitable for all grades of steel castings.
2. Normalizing: Normalizing is a heat treatment process in which the temperature of the cast steel part is heated to above Ac temperature, 30 to 50 degrees Celsius is kept, so that it is completely austenitized and then cooled in still air. General engineering carbon steel and some thick and complex alloy steel castings are mostly normalized.
3. Quenching: Quenching is a heat treatment process in which the precision steel castings are heated to austenitization and then cooled in an appropriate manner after a certain period of time to obtain martensite or bainite structure. Commonly, there are water quenching, oil quenching and air quenching. The steel castings should be tempered in time after quenching to eliminate the quenching stress and obtain the required comprehensive mechanical properties. .
4, tempering: tempering is the quenching or normalizing of the steel castings after heating to Ac, a selected temperature below, after a certain period of heat preservation, cooling at a suitable rate, so that after quenching or normalizing A heat treatment process that converts stable tissue into stable tissue, eliminates quenching (or normalizing) stress, and improves the ductility and toughness of cast steel.
5. Solution treatment: The solution treatment is a heat treatment process in which the casting is heated to a suitable temperature and kept warm, the excess phase is sufficiently dissolved, and then rapidly cooled to obtain a supersaturated solid solution. The main purpose of the solution treatment is to dissolve the carbide or other precipitation phase in the solid solution to obtain a supersaturated single phase structure.
6. Precipitation hardening treatment: After the solution is solid solution treated or quenched, it is kept at a suitable temperature at room temperature or above, forming a solute atomic segregation zone and/or a dispersed distribution strengthening phase in the supersaturated solid solution to make the metal The hardening treatment is called precipitation hardening treatment.
7. The purpose of stress relief treatment is to eliminate casting stress, quenching stress and stress formed by machining, and to stabilize the size.
8. The purpose of hydrogen removal treatment is to remove hydrogen and improve the plasticity of the cast steel. Heat to l70 ~ 200 degrees Celsius or 280 ~ 320 degrees Celsius, heat treatment for a long time. There are no organizational changes. It is mainly used for low alloy steel castings that are prone to hydrogen embrittlement.