Since the investment casting involves a complicated process, there’s no shortage of opportunities for some things to go wrong. When certain undesirable irregularities in a metal casting process result in defects, the manufacturer can decide whether these defects are tolerable, repairable or need to be eliminated altogether. However, before a decision is to be made, the nature of the defect must be clearly understood. Moreover, the location of the defect, its appearance, dimension, and shape must be taken into account as well. These investment casting defects fall into these categories:
Hot Tear or Shrinkage Crack
When the ceramic shell mold restricts the molten metal from contracting during the process of solidification or cooling, a hot tear defect may present itself. This usually looks like a jagged crack that has an irregular path. Manufacturers often modify the investment casting design to address this problem.
Inclusions
These are classified as negative defects that appear as small, round, angular or irregular craters often as a result of foreign non-metallic particles within the casting. They can also be superficial cavities or depressions in various shapes and sizes with traces of refractory material. A possible cause of inclusions can be wax mold cracks that allow bits of ceramic to get into the cavity of the mold.
Misrun
A misrun is a type of negative defect that can take place when the mold cavity isn’t completely filled by the molten metal. This usually occurs when the shell is too cold, metal is too cold or the fill rate is too slow.
Porosity or Gas
This can present itself as a formation of bubbles within the investment casting during the cooling process. Since liquid materials tend to hold large amounts of dissolved gas, these materials expel the gas as they solidify.
Need More Information About Investment Casting Defects?
Understanding investment casting defects is critical in the management of casting quality. Contact Ferralloy, Inc. today to get more information about it.