Head or slide plate for a molten-metal slide gate

A molten metal slide gate comprising head and slide plates, one of said plates comprising a refractory plate having a circular opening and a refractory ring positioned in the opening, one side of the plate and ring cooperatively forming a flat slide surface, the respective peripheries of the opening and ring being shaped so as to cooperatively form an annular chamber spaced between the opposite sides of said one of the plates and the slide surface and an annular passage extending axially from the chamber to the slide surface, a tar ring positioned in the chamber and which vaporizes when the refractory ring is heated by molten metal, and porous refractory filling the annular passage and through which the vaporized tar can migrate to the slide surface.