Submerged nozzle comprising continuous circumferential wavy ribs

A submerged nozzle for casting molten metal into a mould or a tundish, the submerged nozzle comprising,

• a tubular portion (1) made of a first material, wherein the tubular portion,
• extends along a longitudinal axis (Z) over a tube length (L1) between a first end and a second end of the submerged nozzle,
• comprises an inner bore (1b) extending along the longitudinal axis (Z) from an inlet (1i) axially opening at or adjacent to the first end to at least one outlet (1o) opening at or adjacent to the second end,
• an erosion resistant sleeve (2) made of a second material different from, and more resistant to erosion than the first material, wherein the erosion resistant sleeve,
• circumscribes a whole circumference of the tubular portion, and extends along the longitudinal axis (Z) over a sleeve length (L2) lower than the tube length (L1) (i.e., L2<L1),
• comprises a recessed portion (2r) of a thinnest cross-section defined by a major axis (DM) and a minor axis (dm), wherein a ratio (dm/DM) of the minor axis to the major axis is between 0.7 to 1.0,
• characterized in that, the erosion resistant sleeve comprises at least one annular protrusion (2p), extending radially outwards beyond the recessed portion (2r) by a protruding distance (a) over a whole of a circumference of the erosion resistant sleeve (2), wherein the at least one annular protrusion (2p) follows a trajectory around the tubular portion oscillating between one or more tip-points situated closest to the first end and a corresponding number of one or more valley-points situated closest to the second end.