Disadvantages of precision casting

The defect of precision casting is bubble, which refers to the defect of smooth hole in single direction of precision casting. Bubbles are usually found after machining. Precision casting technicians have years of experience in workshop consumption. The causes and methods to avoid bubbles in precision casting are summarized as follows:

I. causes:

1. In most cases, bubbles appear mainly because the precision cast outer shell is not fully roasted, and a lot of gas can't be discharged smoothly in the case of pouring steel, and then intrude into the metal liquid to form bubbles;

2. Due to the shell making technology or shell material, the permeability of the shell is too poor, and the gas in the cavity is difficult to be discharged and enter the metal liquid to form bubbles;

3. Air trapped in the molten steel during pouring fails to drain out and forms casting bubbles.

  Two, avoid method

1. Exhaust bubbles shall be placed at the top of the disordered castings where precision casting conditions permit.

2. When planning the casting system, fully consider the demand for shell exhaust.

3 shell baking temperature, time to be reasonable, insulation time to meet.

4. Thoroughly clean the wax when dewaxing.

5. Properly drop the distance from the ladle nozzle to the pouring cup, and the pouring speed should be even to ensure the steel degree is stable and full of the cavity, and as little as possible to be sucked into the air in the molten steel, so that the air in the cavity and the molten steel can be discharged smoothly.