Heat treatment of precision castings

Precision castings have many heat treatment methods because of different heating and cooling conditions, so it has many heat treatment methods, the following is a small introduction to its main heat treatment methods.

　　1.Annealing: annealing is to heat the cast steel parts to 20-30 degrees Celsius above Acs, applicable to all grades of cast steel parts.

　　2. Normalizing: Normalizing is the heat treatment process of heating the cast steel parts Meguchi to above Ac Celsius temperature, 30 to 50 degrees Celsius insulation, so that it is completely austenitized, and then cooled in the still air. General engineering carbon steel and part of the thick, complex shape of alloy steel castings more normalized treatment.

　　3 quenching: quenching is the cast steel parts heated to austenite, held for a certain period of time after cooling in an appropriate manner, to obtain martensite or bainite organization of the heat treatment process. Common are water-cooled quenching, oil-cooled quenching and air-cooled quenching. Cast steel quenching should be tempered in time to eliminate quenching stress and obtain the required comprehensive mechanical properties.

　　4 tempering: tempering is quenched or normalized cast steel parts heated to a selected temperature below Ac, holding a certain time, after cooling at a suitable rate, so that quenching or normalizing the unstable organization into a stable organization, eliminate quenching (or normalizing) stress and improve the plasticity and toughness of cast steel a heat treatment process.

　　5 solution treatment: solution treatment is the casting is heated to the appropriate temperature and insulation, so that the excess phase is fully dissolved, and then rapidly cooled to obtain supersaturated solid solution heat treatment process. The main purpose of solid solution treatment is to dissolve carbide or other precipitation phases in the solid solution, to obtain a supersaturated single-phase organization.

　　6 Precipitation hardening treatment: castings by solution treatment or quenching, at room temperature or higher than room temperature of the appropriate temperature insulation, the formation of solute atoms in the supersaturated solid solution polarization zone and (or) precipitation of diffuse distribution of the reinforced phase and harden the metal treatment is called precipitation hardening treatment.

　　7. Hydrogen removal treatment: The purpose is to remove hydrogen and improve the plasticity of cast steel. Heating to l70 ~ 200 degrees Celsius or 280 ~ 320 degrees Celsius, a long time to hold the treatment. No organizational changes. Mainly used for low-alloy steel castings that are prone to hydrogen embrittlement tendencies.