Are there any disadvantages in precision casting?

The common defects of precision casting are bubbles. Bubbles refer to the defects of lubricating holes in some positions of delicate castings. Bubbles are generally found after machining and manufacturing. After many years of production line consumption real experience extracted by technical professionals and professional technicians, the reasons for the appearance of bubbles in precision casting and the ways to avoid them are summarized as follows:
1. Constituent reasons:
(1) In most cases, the main reason for the appearance of bubbles is that the delicate cast outer shell is not adequately burned. When the molten steel is poured, the shell will cause a lot of vapor to be unable to be discharged completely, and then invade the metal composite liquid to form bubbles;
(2) Due to the manufacturing process of the shell or the raw materials of the shell, the air permeability of the shell is very poor, and the vapor in the cavity cannot be discharged, and enters into the metal composite material liquid to form bubbles; 3. Entangled in the molten steel during pouring The steam cannot be discharged, which causes bubbles in the casting.
2. Ways to avoid:
(1) Under the conditions permitted by the precision casting specifications, set the bubble discharge at the highest point of the casting with complex structure.
(2) When designing the gating system, it is necessary to fully consider the regulations of the shell exhaust pipe.
(3) The temperature and time for incubation of the mold shell should be reasonable, and the heat preservation time should be sufficient.
(4) Thoroughly clean up the wax material when dewaxing.
(5) Reduce the distance between the ladle nozzle and the glue inlet cup appropriately, and the pouring speed should be average to ensure that the molten steel is stably stored in the concave mold, and try to avoid getting involved in the molten steel vapor, which is conducive to the completeness of the concave mold and the vapor in the molten steel. Discharged.