2, the heating temperature is one of the important process parameters of heat treatment process, is also one of the important parameters of precision casting process.Selection and control of heating temperature, it is important to ensure the quality of heat treatment.Heating temperature is processed metal material and heat treatment for the purpose of different and different, but generally is heated to a temperature above, disguised in order to obtain high temperature.Another change will take time, so when the heating temperature of metal surface is achieved, the need to maintain a certain temperature in this time, make internal and external temperature, the microstructure change completely, this paragraph of time is called the heat preservation time.Heating with high energy density and surface heat treatment and heating speed, generally there is no heat preservation time, and the chemical heat treatment of the holding time is usually long.3, precision casting, its product precision, complex, close to the final shape, can not machining or rarely used directly, so the investment casting is an advanced technology of formed near net shape.