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Common precision casting defects

The common defects of precision casting include air bubble, which refers to the lubrication hole defects in individual positions of fine casting. Bubbles are usually not found until after machining. Jibang precision casting technical personnel separation workshop consumption experience for many years, the reasons and prevention of bubbles in precision casting are summarized as follows:

 

  1. Reasons:
  2. In most cases, bubbles appear mainly because the roasting of the fine casting shell is not enough. When pouring molten steel, a large amount of gas can not be discharged smoothly from the shell, and then invade into the metal liquid to form bubbles.
  3. Due to the shell making process or shell type data, the air permeability of the shell is too poor, and the gas in the cavity is difficult to discharge, and it enters the metal liquid to form bubbles;
  4. Casting bubbles formed when the air involved in the molten steel fails to be discharged during pouring. 1. Under the condition that the precision casting conditions allow, the exhaust bubble is set at the highest point of the casting with complex structure.

 

  1. When designing the pouring system, we should fully consider the exhaust demand of the shell.

 

  1. The roasting temperature and time of shell should be reasonable, and the holding time should be sufficient.

 

  1. Wax material should be thoroughly cleaned when dewaxing.

 

  1. Properly reduce the distance between the sprue nozzle and the sprue cup, and the pouring speed should be even to ensure that the steel degree is stable and fills the cavity, and as little as possible is involved in the air in the molten steel, so that the air in the cavity and the molten steel can be discharged smoothly

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