Causes and Prevention of Bubbles in Silica Sol Casting

Bubbles are lubrication hole imperfections in the part of precision castings that are usually found only after machining. My company after years of production experience on the reasons for the emergence of bubbles in the casting and prevention summarized as follows:

1. Structural reasons

1) Bubbles in most cases are mainly due to inadequate roasting of the shell of the fine castings, large amount of gas generated by the shell instantaneously when the molten steel is poured can not be discharged smoothly, and then invade into the liquid metal to form bubbles. 2) As a result of the shell making process or the shell type Data reasons, poor permeability of the shell, the cavity of the gas is difficult to discharge, into the liquid metal bubble; 3) pouring into the molten steel in the air can not be discharged to form the casting bubbles.

2. Prevention methods

1) Exhaust holes are to be provided at the highest point of the complicated castings under the condition of precision casting. 2) In the design of casting system, to take into account the type of shell exhaust needs. 3) type shell temperature, time should be reasonable, holding time should be adequate. 4) dewaxing wax should be thoroughly cleaned. 5) properly reduce the casting interval, the casting speed to be average, to ensure the stability of the steel filled overflow cavity, as little as possible into the molten steel in the air, so that the cavity and the molten steel can be successfully discharged.


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