Inclusions (Ceramic)
Technical Support
Struggling with a specific casting defect or just need general technical support?
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Missing areas of metal in the casting; appearing as small, round, irregular or angular craters, depressions or cavities of various sizes; typically superficial with traces of ceramic and refractory material
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Indicates that something is present in the mold cavity that prevents the casting from fully filling to the shell; typically ceramic shell debris, bits of the pour cup, or the inner mold surface broke off into the molten metal during pouring and were left behind on the casting surface
Causes of this defect are evident in the wax, shell and other portions of the process; to cure, R&R recommends taking the following actions:
Wax
Poor wax assembly – undercuts.
When patterns are attached to the sprue and the connection is not completely filled or contains undercuts, these undercuts fill with slurry. When the shell is dewaxed, this ceramic extends into the shell cavity and can be dislodged when metal is poured resulting in a ceramic inclusion.
Shell
Cracks in mold.
Shell formed pour cups, jagged rim.
Invested pour cup is brittle, jagged and/or fragile.
As a result, the invested pour cup is breaking when the metal is being poured, becoming entrapped as inclusions.
The primary coat layer is spalling.
Inadequately dried shells.
Out of control slurry.
Other
Housekeeping.
Molds are being fired with the cup upright, entrapping dust or ash from residual wax residue.
Dust particles are trapped in the shell cavity.