Casting defects · sand & mould

Metal penetration casting defect

Penetration is metal forced into the spaces between sand grains, leaving a rough, knobbly metal-and-sand crust. It is a sand-strength and temperature problem.

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

What it is

Metal penetration happens when liquid metal is pushed into the interstices between sand grains before the mould face has frozen it off. The result is a rough, hard crust of mixed metal and sand, usually at hot, heavy sections and re-entrant corners where the mould stays hot longest.

Penetration or burn-on?

Both roughen the surface. In penetration the metal goes between the grains and the crust is knobbly and hard to remove. In burn-on a thinner sand layer adheres to the surface. Both trace to sand and temperature, and both are worth logging where fettling time is a cost.

Root causes

• Coarse sand or soft ramming. Large or open pores let metal in; hold compaction and grain fineness.
• High pouring temperature and metallostatic head. Hotter metal and taller sections push harder into the sand.
• Weak mould face at hot spots, sometimes worsened by inadequate coating.

Prevention checklist

• Control grain fineness and ramming; keep the mould face dense and firm (calibrated sand tests).
• Lower and control pouring temperature where penetration recurs.
• Apply and dry a suitable mould/core coating at hot sections.
• Review the method at heavy, re-entrant areas that stay hot; add chills where useful.
• Track penetration by part and location so the fettling burden points to a real sand or method fix.

Frequently asked questions