An immersion nozzle comprising: a flange having an axially lower surface; said immersion nozzle being adapted for being exchanged with an exchangeable nozzle by an exchanging apparatus, wherein the exchanging apparatus has a plurality of key plates extending mutually parallel on the exchanging apparatus, the key plates being adapted for supporting said lower flange surface of said immersion nozzle, the exchanging apparatus advancing the exchangeable nozzle against said immersion nozzle for moving said immersion nozzle so that respective opposite sides of said immersion nozzle engage the key plates; said immersion nozzle further comprising: an axially upper end surface, said upper end surface including said flange; a neck disposed axially below said upper end surface; a metal case covering said neck; a molten-metal delivery port spaced axially below said neck; a first projection disposed on said metal case at said neck, said projection spaced axially below said upper end surface by a first predetermined distance, said first projection being axially aligned with said molten-metal delivery port; and a second projection disposed on said metal case and spaced axially below said first projection by a second predetermined distance, said second projection being axially aligned with said molten-metal delivery port; said first and second projections extending cirumferentially about said nozzle and being mutually parallel and parallel to a radially extending axis of said immersion nozzle; and a circumferential length of said projections being equal to or greater than two-thirds of an inner bore diameter of said immersion nozzle.
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