Pore is one of the common defects in precision casting, which refers to the appearance of smooth hole defects in individual positions of precision castings. Pores are usually only discovered after machining. Based on years of workshop production experience, precision casting technicians have summarized the causes and prevention methods of porosity in precision casting as follows:

1、 Cause of formation: 1. In most cases, the occurrence of pores is mainly due to insufficient roasting of precision casting shell. During the pouring of molten steel, a large amount of gas is generated in the shell instantly and cannot be discharged smoothly, which then invades the metal liquid to form pores; 2. Due to the shell making process or shell material, the air permeability of the shell is too poor, making it difficult to expel gas from the cavity and forming pores in the molten metal; 3. The air trapped in the molten steel during pouring cannot be discharged, resulting in casting porosity.

2、 Preventive method 1. If precision casting conditions permit, set exhaust holes at the highest point of structurally complex castings. When designing the pouring system, full consideration should be given to the exhaust requirements of the mold shell. 3. The roasting temperature and time of the shell should be reasonable, and the insulation time should also be sufficient. 4. When dewaxing, the wax material should be thoroughly removed. 5. Appropriately reduce the distance between the ladle nozzle and the pouring cup, and the pouring speed should be uniform to ensure that the steel is horizontally and stably filled into the mold cavity, and to minimize the involvement of air in the molten steel, so that the gas in the mold cavity and molten steel can be smoothly discharged.