Superficial and Internal Defects in Die Casting

Several defects can occur during the die casting process that can significantly affect the quality of the finished material. The occurrence of such defects on the casted materials is attributed to the limitations in mold design and numerous other factors involved in the die casting process.

The defects will happen to the material during any stages of the process like die-casting, pre-finishing, machining operations, and surface finishing. Defects that commonly occur during the die casting process are divided into two categories: Internal and Superficial. Described below are some of the types of defects that occur in both these categories.

Superficial Defects

Superficial defects that occur during the die casting process will cause degradation of the component surface and its aesthetic quality. They are visible when compared to internal defects.

  • Cold Laps

These are the most commonly occurring defects in die casting and occur to the irregularities in the flow and low temperatures. It contains many other defects like flow marks or the lack of material as well. This defect can cause the component surface quality to degrade or become incomplete.

  • Laminations

Laminations are defects that arise due to the overlapping of two layers that remain separated in the filling phase. Laminations are difficult to identify after the casting. This defect mostly occurs on the surface during the tumbling and sandblasting operations.

  • Blisters

Blisters are defects that occur during the mold filling phase. The air that remains in the component after ejection through the vents and valves can cause the formation of high-pressure cavities. Blisters can cause the weakening of the strength of the component.

Internal Defects

Internal defects that occur during the die casting process can cause the structural resistance of the component to weaken.

  • Gas Porosity

Gas porosity is a commonly occurring internal defect in the die casting process. It arises due to the generation of turbulences during the filling phase of the process. The high-speed fluid filling will result in the entry of air and gasses that are trapped during solidification. These air trappings create cavities that degrade the module’s interior sections.

  • Shrinkage Porosity

Shrinkage porosity defects occur during the solidification and cooling stages of the die casting process. The materials will often shift towards the colder regions that result in differences in temperature between the casting surface and core, which leads to the formation of cavities inside the die cast product.