Solidification shrinkage

Decrease

in volume during the transition from the liquid to the solid state (s.

Solidification), the direct consequence of which is a volume deficit in

the form of porosity and pores (Figure 1).

The

volume deficit caused by shrinkage is compensated for by post-feeding

in the casting process, under the condition that all areas of the

casting are not yet blocked by already solidified melt. The casting

should be designed in such a way the localized accumulation of material

in remote parts is avoided. Today, such areas can be identified using

simulation calculations of the solidification process and can be removed

by changing the gate technology. However, production control for pores (partly radioscopic) is necessary for high-quality parts.

  • Figure 1: Temperature dependency of the solidification of a casting alloy (TS solid temperature; TL liquid temperature; α  volume contraction)
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