metallostatic

Metallostatic pressure is the hydrostatic pressure exerted by the weight of molten metal in a vessel, furnace, or casting mold. It acts vertically downward from the surface of the liquid metal and increases with depth according to the formula P = ρgh, where ρ is the density of the molten metal, g is gravitational acceleration, and h is the vertical distance below the surface. For steel, which has a density around 7,000 kg/m³ when molten, a column one meter deep exerts roughly 70 kilopascals of pressure at the bottom.

In casting operations, metallostatic pressure drives metal into mold cavities and through feeding systems. The depth of metal above a gate or feeder determines how forcefully the liquid fills that region. This is why risers in sand casting are positioned high above the casting proper, and why the metallostatic head must be maintained above critical sections during solidification to prevent shrinkage porosity. The pressure also influences metal flow rate through runners and gates, which foundry workers and engineers calculate to control filling speed and mold wall erosion.

Measurement and Control

Metallostatic pressure is measured using pressure transducers inserted into the mold wall or vessel at known depths. These readings reveal whether the metal level is stable, whether the mold is filling uniformly, and whether vacuum conditions are developing during solidification. In continuous casting of steel, maintaining steady metallostatic pressure prevents breakout (when molten metal breaches the solidifying shell) and ensures the mold powder film remains stable.

The term appears most often in casting metallurgy literature and in foundry design calculations. It is distinct from ferrostatic pressure, which is sometimes used interchangeably but more properly refers specifically to iron or steel. Metallostatic head is the corresponding term for the vertical height of molten metal that generates the pressure; a foundry worker might say "we need three feet of metallostatic head here to fill the cope properly." The concept is so fundamental that it shapes the entire geometry of gating systems, furnace depth, and feeder placement.