Is precision casting defective?

The common shortcomings of precision casting are bubbles. Bubbles refer to the shortcomings of moisturizing holes in some parts of the delicate castings. Air bubbles are generally only detected after machining. After many years of personal experience in the production workshop separated by professional and technical personnel, the reasons for the bubbles in precision casting and the prevention methods are summarized as follows:
1. Reasons for composition:
(1) In most cases, the key to the appearance of bubbles is because the fine cast appearance shell is insufficiently burned. When the molten steel is poured, a lot of vapor can not be discharged completely in the instant, which invades the metal material liquid to form bubbles;
(2) Because of the shell processing technology or shell material, the air permeability of the shell is very poor, and the vapor in the cavity cannot be discharged, and it enters into the metal material liquid to form bubbles; 3. The gas entangled in the molten steel cannot be discharged during pouring. Then the casting bubbles are produced.
2. Prevention method:
(1) When the precision casting standard allows, set the bubble discharge at the highest point of the casting with complicated structure.
(2) When designing the gating system software, fully consider the requirements of the shell exhaust pipe.
(3) The temperature and time for incubation of the shaped shell should be effective, and the heat preservation time should be sufficient.
(4) Clean the wax material completely when dewaxing.
(5) Appropriately reduce the distance between the ladle nozzle and the glue inlet cup, and the pouring rate must be average to ensure that the molten steel is stably stored in the die, and the gas involved in the molten steel is as little as possible, so that the die and the steam in the molten steel can be discharged successfully.