Patent ID: 7641081

Claim:
An immersion nozzle, comprising: a pipe-shaped straight nozzle body which is formed to extend in a substantially vertical direction and have an inlet port at an upper end thereof, and adapted to allow molten steel to pass downwardly from said inlet port therethrough; and a pair of discharge portions each including a respective one of a pair of outlet ports which are provided in a lower portion of said straight nozzle body bilaterally symmetrically with respect to said straight nozzle body, and adapted to discharge molten steel from a lateral side of said straight nozzle body therethrough in laterally opposite directions, each of said outlet ports being defined by an inner wall surface formed in a corresponding one of said discharge portions, said pair of discharge portions being structurally configured such that said molten steel, when passed downwardly from said inlet port, is exclusively dischargeable through said pair of outlet ports, wherein: said inner wall surface defining said outlet port in each of said discharge portion is formed to extend parallel to a longitudinal direction of an axis of said outlet port in such a manner as to define a length of said discharge portion at 45 mm or more; a ratio of S 1 /S 2 is in the range of 0.8 to 1.8, wherein S 1 is a total transverse vertical cross-sectional area of said outlet ports, and S 2 is a cross-sectional area of an inner hole of said straight nozzle body taken along a plane which includes a line connecting respective uppermost positions of inwardmost edges of said outlet ports and extends in perpendicular relation to an axial direction of said straight nozzle body; and said axis of each of said outlet ports extends laterally outwardly and downwardly at an angle θt falling within the following range with respect to a horizontal direction: 0°≦θt≦20°.