Atlas of Casting Defects
Negative
These are closely related to oxide fold defects but are typically circular in form rather than linear.
Can be small up to an inch or more in diameter
Generally located on the surface of the casting
Oxidized droplet
Visual or Fluorescent Penetrant Inspection
During casting, droplets of metal detach or are separated from the pouring stream by excessive turbulence, mold design, or metal pouring height. The metal droplet becomes either cooler in temperature or coated with a tenacious oxide film and retains this identity as part of the cast metal.
| Area | Possible Cause | Potential Correction |
|---|---|---|
| Wax | Cold wax at nozzle tip |
Wax cold shot can occur in the wax pattern and be duplicated through the shelling process, thereby resulting in a similar-looking metal defect. (Ensure nozzle tip temperature is adequate to keep wax from solidifying). |
| Other (Mold design) | Bad mold design |
Mold design should promote non-turbulent metal flow |
| Foundry | Bad pouring practice |
Avoid metal splashing during pouring |
| Foundry | Bad pouring practice |
Reducing the distance between the crucible and the mold to be poured to minimum, thereby reducing the chance for splashing |
| Foundry | Pouring practice |
Employ use of a reticulated foam filter to achieve a laminar flow |
| Foundry | Pouring practice |
Formation of a well in the mold to allow the metal to collect and then flow into the mold parts |