Immersion nozzle for continuous casting and continuous casting method using the immersion nozzle

Abstract

An immersion nozzle for continuous casting which enables improvement in quality of a slab surface and increase in the efficiency of casting by suppressing the self-excited oscillation of a flow in a mold without using a complicated mechanism such as a swirl flow generating immersion nozzle is to be provided. A first immersion nozzle for continuous casting is a nozzle comprising a cylindrical body and a pair of outlet ports formed to face each other in a side wall in the vicinity of a bottom part of the cylindrical body, wherein a ridge-shaped projection extending parallel with the discharge direction projected on a cross section of the nozzle is formed on an inner surface of the bottom part, which is formed in a waterfall basin-like recessed shape having a maximum depth of 5 mm to 50 mm. A second immersion nozzle for continuous casting is a nozzle comprising a cylindrical body and a pair of outlet ports formed to face each other in a side wall in the vicinity of a bottom part of the cylindrical body, wherein each sectional area of the outlet ports vertical to a discharge direction projected on a cross section or longitudinal section of the nozzle is decreased toward an exit.

1 . An immersion nozzle for continuous casting, which is a nozzle comprising a cylindrical body and a pair of outlet ports formed to face each other in a side wall in the vicinity of a bottom part of the cylindrical body, wherein a ridge-shaped projection extending parallel with a discharge direction projected on a cross section of the nozzle is formed on an inner surface at the bottom part, which is formed in a waterfall basin-like recessed shape having a maximum depth of 5 mm to 50 mm.  
   
   
       2 . An immersion nozzle for continuous casting according to  claim 1 , wherein a maximum height of the ridge-shaped projection is as same as the maximum depth of the waterfall basin-like recess or is in the range of ±10 mm of the maximum depth of the waterfall basin-like recess, in which the maximum height of the ridge-shaped projection is 5 mm to 50 mm, and the ridge-shaped projection is in one form selected from the group consisting of: 
 a ridge-shaped projection having a peak or a horizontal apex in the central part or in the vicinity thereof on a cross section of the nozzle, in which a ridgeline of the ridge-shaped projection extends from the peak or the horizontal apex to each of two outlet ports by decreasing a height of the projection so as to reach a position at a side wall of a waterfall basin-like recessed shape portion lower than a lower wall of the discharge hall, or in which a ridgeline of the ridge-shaped projection extends from the peak or the horizontal apex to each of two outlet ports by decreasing a height of the projection so as to reach a bottom part and the projection itself is terminated in the vicinity of an outlet port entrance of the cross section of the nozzle; and    a ridge-shaped projection having a horizontal apex in the central part or in the vicinity thereof on a cross section of the nozzle, in which the ridgeline of the ridge-shaped projection extends from the horizontal apex to each of two outlet ports by decreasing a height of the projection or by descending vertically so as to reach the bottom part and the ridge-shaped projection is only provided in the vicinity of the central part on the cross section of the nozzle.    
   
   
       3 . An immersion nozzle for continuous casting according to  claim 1 , wherein the waterfall basin-like recess is in a form of an ellipse or oval larger than an inner diameter of a nozzle body in the discharge direction projected on the cross section of the nozzle.  
   
   
       4 . An immersion nozzle for continuous casting according to  claim 2 , wherein the waterfall basin-like recess is in a form of an ellipse or oval larger than an inner diameter of a nozzle body in the discharge direction projected on the cross section.  
   
   
       5 . An immersion nozzle for continuous casting, which is a nozzle comprising a cylindrical body and a pair of outlet ports formed to face each other in a side wall in the vicinity of a bottom part of the cylindrical body, wherein each sectional area of the outlet ports vertical to a discharge direction projected on a cross section or longitudinal section of the nozzle is decreased toward an exit.  
   
   
       6 . An immersion nozzle for continuous casting according to  claim 5 , wherein an average height of an outlet port exit is 0.5 to 0.9 times of an average width of the outlet port exit.  
   
   
       7 . An immersion nozzle for continuous casting according to  claim 5 , wherein an upper wall of the outlet port is in a circular form having a curvature radius “R” of 30 mm to 150 mm and having a cross section of expanding inner diameter from an inner wall of the body toward the upper wall of the outlet port, and an angle of a lower wall of the outlet port is in the range of 15° upward to 45° downward.  
   
   
       8 . An immersion nozzle for continuous casting according to  claim 6 , wherein an upper wall of an outlet port is in a circular form having a curvature radius “R” of 30 mm to 150 mm and having a cross section of expanding inner diameter an inner wall of the body toward the upper wall of the outlet port, and an angle of a lower wall of the outlet port is in the range of 15° upward to 45° downward.  
   
   
       9 . A continuous casting method using the immersion nozzle for continuous casting defined by  claim 1 , wherein an average descend flow rate of a molten metal “U” of a portion immediately above an outlet port of a body is 1.0 m/s to 2.5 m/s.  
   
   
       10 . A continuous casting method using the immersion nozzle for continuous casting defined by  claim 5 , wherein an average descend flow rate of a molten metal “U” of a portion immediately above an outlet port of a body is 1.0 m/s to 2.5 m/s.