Refractory immersion tube providing laminar flow of molten metal

In a refractory immersion tube for use in discharging molten metal from a metallurgical vessel into a mold under the static pressure of the molten metal, said immersion tube having an inner passage through which passes the molten metal and including an inlet opening for receiving the molten metal and at least one outlet opening extending from said passage for discharging the molten metal into a mold, the improvement comprising means for preventing the flow of molten metal from said outlet opening from being turbulent and for ensuring that said flow is laminar, said means comprising:

• an annular member positioned within said passage and restricting the cross-sectional area thereof, wherein said annular member having therethrough an orifice defined by a curved surface including, in longitudinal section, an upstream first surface portion and a downstream second surface portion, said first surface portion being defined by a smaller radius of curvature than said second surface portion.