Edge Porosity Defect
Defects
Porosity at the edges of the casting, near the gates.
Cause
Either shrinkage of the molten metal as it cools and solidifies, or the presence of trapped gases.
Corrections
- Shrinkage porosity correction:
- Enhance cooling in the area near the gates to reduce the formation of loose dendritic structures, which create pathways for gases. However, excessive cooling may be necessary for thin gates.
- Implement long, flat gate ramps to prevent the hot steel from directly contacting the gate.
- Increase the gate's width while decreasing its thickness to spread the heat more effectively. Ensure that the gate velocity remains within the proper range.
- Relocate the gate to a cooler region of the die, if feasible.
- Minimize the fill time to reduce the amount of heat retained at the gate due to the metal stream.
- Gas porosity correction:
- Gas porosity contributes to outgassing, but to a lesser extent than shrinkage porosity.
- Employ the techniques described in the shrinkage porosity correction section to mitigate this issue.
Edge porosity (6.5X).
Please note that the information provided in this article is intended to be a general guide to the causes and corrections of edge porosity 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.