Casting Defect Catalog: Causes, Identification and Correction
Casting defect catalog for die casting: cold shut, misrun, porosity, hot tear, solder, flash, blister, warpage, inclusion and erosion with cause, identification and correction.
Casting Defect Catalog: Causes, Identification and Correction
Overview
Most die casting rejects trace back to a handful of defect types. Correcting them starts with identifying which one you have, because the same visible symptom can come from opposite causes — a void can be gas porosity (fix the fill) or shrinkage porosity (fix the feeding). This catalog lists the defects most frequently found in aluminum, zinc and magnesium HPDC, with the cause, how to recognize it, and the correction that addresses the root cause rather than the symptom.
The table is the working reference. Pair it with process control guidance in Die Casting Porosity Prevention and Aluminum Die Casting Process Guide.
Defect Catalog
| Defect | Cause | Identification | Correction |
|---|---|---|---|
| Cold shut | Low pour/die temperature or slow fill; two flow fronts meet without fusing | Visible line or shallow crack on surface, often far from gate | Raise melt and die temperature, increase fill rate, improve venting |
| Misrun | Insufficient metal or fill velocity; thin section freezes before complete | Incomplete part, short fill at extremities and ribs | Increase wall/runner size, raise velocity, preheat die |
| Porosity (gas) | Air or moisture entrapment, turbulent fill, excess lubricant gas | Round, smooth-walled voids; porous fracture surface | Reduce entrainment, vacuum assist, control lube, degas melt |
| Porosity (shrinkage) | Localized shrinkage away from feeding path in thick sections | Irregular, dendritic voids at thick sections | Add feeders, chill thick areas, balance wall thickness |
| Hot tear | Constraint during solidification; high-shrinkage alloy at rigid feature | Crack at corners or rib bases near the gate | Increase draft, round corners, reduce die constraint |
| Solder (die) | Alloy welds to die steel at gate or hot spot | Metal stuck to die, rough local surface transfer | Adjust die temperature, apply coating, reduce local heat |
| Flash | Excess metal at parting line; low clamp force or worn shutoff | Thin fin of metal at the die split line | Raise clamp tonnage, maintain shutoff, reduce specific pressure |
| Blister | Subsurface gas expands on heating during plating or paint bake | Domed bubbles after coating or heat treatment | Reduce porosity, lower bake temperature, degas melt |
| Warpage | Uneven cooling, residual stress, asymmetric wall sections | Dimensional distortion after ejection | Balance walls and cooling, redistribute ribbing, stress relieve |
| Inclusion | Oxide, silicon or foreign particle carried in the melt | Hard spot or void with embedded particle, machining defect | Improve melt handling, filtration, degassing |
| Erosion | High-velocity metal washes and erodes die steel at gate | Gouged cavity near gate, progressive dimensional growth | Harden cavity steel, tune velocity, balance gating |
How to use this reference
- Section the suspect part and inspect the fracture: round voids = gas, dendritic voids = shrinkage.
- Match the symptom to the table, then apply the correction to the root cause — do not just raise pressure, which can worsen erosion and solder.
- For porosity specifically, separate gas from shrinkage before acting; the fixes are different. See Die Casting Porosity Prevention.
- Track defect type by cavity and shot to separate tool wear (erosion, solder, flash) from process drift (cold shut, misrun).
- Confirm alloy-related tendencies with Aluminum Die Casting Alloys and Zinc Die Casting Alloys.
Related Articles
- Die Casting Porosity Prevention
- Aluminum Die Casting Process Guide
- Aluminum Die Casting Alloys
- Zinc Die Casting Alloys
References
- NADCA Product Specification Standards for Die Castings — https://www.diecasting.org/
- ASTM E505, Reference Radiographs for Inspection of Aluminum and Magnesium Die Castings