Casting defects · sand & mould

Sand inclusion casting defect

A sand inclusion is loose moulding sand trapped in the casting. It points at a mould that shed material - through weakness, erosion or careless closing.

By Versatile Equipments Pvt Ltd · equipment manufacturer & calibration provider · updated 2026-07-15

What it is

A sand inclusion is a pocket of moulding sand embedded in the casting, often just under the surface, leaving a rough cavity when it drops out. The sand came from the mould or core - shed because it was friable, washed loose by the metal stream, or knocked in during closing.

Sand or slag?

Both are non-metallic inclusions. Sand inclusions are gritty and match the moulding sand; slag or dross inclusions are glassy or filmy and come from the melt. Where the inclusion sits helps: sand tends to follow the metal path or gather under loose mould areas; slag rises and collects near the top of a section. Both are worth logging separately, because one points to the mould and the other to the melt.

Root causes

• Weak, friable mould or core. Low green strength, dry edges, poor compaction - numbers to hold with a calibrated strength tester.
• Erosion (cut and wash). A hot, fast or badly directed stream scours sand off the mould.
• Poor closing and handling. Loose grains not blown out, damaged edges, rough core setting.

Prevention checklist

• Hold green strength and compactability in band, verified on calibrated equipment.
• Gate to spread and slow the stream; avoid a jet that scours the mould.
• Blow moulds and cores clean before closing; protect edges; set cores gently.
• Coat or firm vulnerable surfaces where erosion recurs.
• Log sand inclusions by part and location, so a recurring loose edge gets found and fixed.

Frequently asked questions