Causes and Solutions of Pore Formation in Precision Casting

Porosity 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 discovered after machining. Based on years of workshop production experience, Yanzi's precision casting technicians have summarized the causes and prevention methods of porosity in precision casting as follows:

1、 Causes of formation: 1. In most cases, the occurrence of air holes is mainly due to insufficient roasting of precision casting shell, which causes a large amount of gas generated by the shell during pouring of molten steel and cannot be smoothly discharged, thereby invading the metal liquid to form air holes; 2. Due to the shell making process or shell material, the air permeability of the shell is too poor, making it difficult to exhaust 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 complex castings. When designing the pouring system, it is necessary to fully consider the exhaust needs of the mold shell. 3. The shell baking temperature and time should be reasonable, and the insulation time should also be sufficient. 4. When dewaxing, the wax material should be thoroughly removed. 5. Properly reduce the distance between the ladle nozzle and the pouring cup, and ensure that the pouring speed is uniform to ensure that the steel is horizontally and stably filled with the mold cavity, and to minimize the involvement of air in the molten steel, so that the gas in the mold cavity and the molten steel can be smoothly discharged.