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Reasons and solutions for precision casting porosity
Porosity is one of the common precision casting defects, which refers to smooth hole defects in individual locations of precision castings. The stomata are usually not found after machining. Scorpion Hardware Accessories technicians combined with years of workshop production experience, the reasons for the occurrence of pores in precision casting and prevention methods are summarized as follows:
First, the reasons for formation: 1. In most cases, the occurrence of pores is mainly due to insufficient sintering of the precision casting shell. When the molten steel is poured, a large amount of gas is instantaneously discharged from the shell, and the pores are intruded into the molten metal; 2. Because of the shell For the reason of the process or the shell material, the gas permeability of the shell is too poor, the gas in the cavity is difficult to discharge, and the pores are formed in the molten metal; 3. The air that is caught in the molten steel during pouring is not discharged, thereby causing the pores of the casting.
Second, the prevention method 1. In the case of precision casting conditions, the vent hole is provided at the highest part of the casting with complex structure. 2. When designing the gating system, fully consider the casing exhaust requirements. 3. The calcination temperature and time of the shell should be reasonable, and the holding time should be sufficient. 4. The wax should be completely removed when dewaxing. 5. Properly reduce the distance between the pouring spout and the sprue cup, and the pouring speed should be uniform to ensure that the molten steel fills the cavity smoothly, and the air in the molten steel is trapped as little as possible, so that the gas in the cavity and the molten steel can be smoothly discharged.