Collision‐controlled growth of composites in casting nozzles

Abstract

Like the open‐stream nozzles and submerged entry nozzles on c.c. tundishes, ladle nozzles can also become blocked. Accumulations of Al 2 O 3 , CaO · 2Al 2 O 3 , CaO · Al 2 O 3 , MgO · Al 2 O 3 and Ti 3 O 5 particles were observed on five sleeves removed from rotary ladle nozzles. The type of particles suspended in the steel depends on metallurgy. Growth takes place in bushy ramification in a coral‐shaped structure and is controlled by flow separation, interfacial turbulence and gradient collision. Heat transfer on the nozzle wall is impaired. Steel which has infiltrated freezes if a heat sink is present. A stable composite of steel and oxide is formed. CaS depositions in c.c. tundish submerged entry nozzles are also examined. These CaS deposits become coated with viscous aluminates of the (C 12 A 7 + CA) type, prior, here too, to impregnation with steel. The overall result is a reduction in interfacial energy.