Atlas of Casting Defects
Negative
Metallic oxides are thin black sub-surface streamers forming an irregular pattern or agglomeration on the surface of the casting.
Varies
Surface and subsurface
Oxide Folds, Dross, Slag, Oxide Film
Metallic oxide indications tend to be thin, irregular, randomly placed or located, strings of materials containing oxygen and reactive elements. Metallic oxide indications can be determined by visual or EDS inspection.
During casting a refractory oxide skin is formed in the melt through the exposure of reactive elements to oxygen. Certain elements are more reactive than others and will preferentially oxidize. The metallic oxide that is formed can be aggravated with turbulent filling.
| Area | Possible Cause | Potential Correction |
|---|---|---|
| Foundry | Impure melting stock |
Use oxide-free melting stock or filters |
| Foundry | Oxidation of reactive elements |
Prevent oxidation of the melt through the use of vacuum or protective atmosphere |
| Foundry | Prevent oxidation of the melt through the use of vacuum or protective atmosphere |
Allow time for deoxidation adds to be effective, agitate melt and de-slag for improved deoxidation |
| Foundry | Turbulence |
Reduced filling speed |