The invention concerns a nozzle mainly consisting, when viewed in vertical position and in the forward movement of the liquid steel from the top downwards, of a vertical conduit (5) comprising in its upper part a distributing member, arranged substantially at the intake of said conduit and including a dome (6) for deflecting the metal penetrating into the nozzle, which is also provided with means for injecting a gaseous, liquid or solid finely divided material beneath said dome (6) into a so-called inner zone (11). The dome (6) of said distributing member is provided with means for separating liquid steel into two jets (B, C), a jet (B) flowing into the so-called inner zone (11) and penetrating into the ingot mould (1) through a first orifice (9) at the lower base of said conduit (5) and a jet (C) flowing into a so-called outer zone (12) and penetrating into the ingot mould (1) through lateral orifices (8) located in the vertical wall of said conduit (5).