Veining Defects and the Role of Additives

Veining appears as thin fins of metal on casting surfaces, usually on cores. It is caused by sand expansion and cracking.

Causes

• Silica sand expansion at about 573°C
• Rigid cores that crack under heat

Additive solutions

• Iron oxide or special anti-veining additives
• Carbonaceous additives that burn out and give space for expansion
• Finer sand blends

Gilsonite’s contribution

In some core systems, a small amount of gilsonite provides cushioning as it volatilizes. Results depend on the binder system and should be tested.

Typical locations

Veining usually appears on internal surfaces formed by cores, especially in iron castings with thick sections.

Remedies

Trial approach

Change one factor at a time and inspect sectioned castings.

See foundry grade gilsonite. Related: gilsonite in core sand.