Heat Sinks Defect
Defects
Heat sinks (shrinkage porosity)
Cause
Shrinkage cracks just under the surface.
Corrections
- See the corrections for shrinkage porosity, as those techniques will work here.
- Cool the hot spot directly where the heat sink occurs. Use one of the following methods:
- Fountain (first choice)
- Die spray
- Thin biscuits and improve plunger conditions (hot or cold chamber).
- Heat the opposite side of the casting. To do this, shut off the water and stop the spray.
- Check for uneven temperatures between the die halves, especially in the area of the heat sink.
- Use pressure to feed more metal to the area where the sink occurs during solidification. To do this, you can:
- Adjust the intensifier.
- Move the gate.
- Change the static pressure.
- Check for a dragging tip (low pressure).
- Check the accumulator pre-charge (low pressure).
Heat sink – typical appearance on a smooth surface (1X).
Fracture through a heat sink – the original shrink porosity under the skin is visible (7X).
Heat sink where some eutectic material oozed through the skin to par-tially fill the sunken area (5X).
Please note that the information provided in this article is intended to be a general guide to the causes and corrections of heat sinks in metal castings. However, it is important to note that the specific cause and correction of any particular defect will vary depending on the specific casting process, alloy, and other factors. Therefore, it is important to consult with an experienced and professional engineer to ensure that the correct diagnosis is made and the most suitable correction is chosen.