Shrinkage Cavity

shrinkage cavity

[′shriŋ·kij ‚kav·əd·ē]
A cavity resulting from shrinkage during casting.

Shrinkage Cavity


a void in an ingot or shaped metal casting, formed during the solidification of the molten metal as a result of shrinkage. Shrinkage cavities are usually located in the upper portion of an ingot or in those spaces within a casting where the molten metal is last to enter during pouring. During solidification, a shrinkage cavity serves to supply molten metal to all the voids formed underneath the cavity; therefore, steps are taken to maintain a temperature above the point of solidification for as long as possible in the area where the shrinkage cavity is located.

Before ingots are rolled or forged, the upper portion with the shrinkage cavity is generally cut off and discarded. In order to minimize scrap losses, a shrinkage cavity must be as wide and short as possible and extend only a little into the ingot. This is achieved by using an ingot mold that widens toward the top, which gives the shrinkage cavity the shape of a short cone with a peak facing the bottom of the ingot. Steps are also taken to heat the feeder part of the ingot. If solidification of the last portions of the molten metal is not retarded and the shrinkage cavity is not localized, the cavity will spread down into the ingot and its lower, narrower end will branch out; as a result, additional large cavities or small holes (porosity) may form near the shrinkage cavity, usually underneath.

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Depending on its severity, this situation would result in a shrinkage cavity.
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Standard examinations allow detecting fractures of casts and macro-discontinuities like gas cavities, as well as discontinuities connected with contraction phenomena occurring during metal solidification (shrinkage cavity) (Gawdzinska, et al, 2008).
Within recent 10-15 years several mathematical models have been developed, which describe different EBCHM stages: melting of the initial charge, mixing and evaporation of the metal and impurities in the intermediate unit, formation of the ingot in the mould (including withdrawal of the shrinkage cavity), and cooling of the ingot.
A shrinkage cavity is a void left in cast metals as a result of solidification shrinkage and the progressive freezing of metal toward the center.
Effect Of Pouring Temperature And Composition On Shrinkage Cavity In Spheroidal Graphite Cast Iron (06-084)
In addition to the prediction of the temperature field and solidification front, they also found it important to develop a method to compute shrinkage cavity in castings that was cost-efficient.
* decreased shrinkage cavities in castings with thick/thin wall thickness - SVC raises the eutectic temperature by 18F (10C) and stretches the eutectic reaction time to 1 min, which results in simultaneous solidification and less of a shrinkage cavity in the thick walls.
All aluminum ingots and sows are merely unrisered castings and, as such, will contain a probable zone of sponge shrink or even a shrinkage cavity that may contain moisture.
3, rt) shows that a shrinkage cavity also will form at the Y junction.
A shrinkage cavity or a nitrogen fissure appears as an irregularly shaped hole.