Immersion nozzle

Abstract

An immersion nozzle for discharging molten steel supplied from a tundish into a mold for continuous casting of a slab includes a discharge portion that supplies the molten steel to the mold, wherein the immersion nozzle includes two regions divided by a plane in a thickness direction, the plane passing through an axial center, the discharge portion includes: a bottom portion; and a side wall that extends in a height direction from an outer edge of the bottom portion, four discharge holes are formed in the discharge portion, two discharge hole are arranged side by side in a width direction in each of the regions in the bottom portion of the discharge portion.

1 . An immersion nozzle for discharging molten steel supplied from a tundish into a mold for continuous casting of a slab,
 the immersion nozzle comprising a discharge portion that supplies the molten steel to the mold, wherein   the immersion nozzle includes two regions divided by a plane in a thickness direction, the plane passing through an axial center,   the discharge portion includes:   a bottom portion; and   a side wall that extends in a height direction from an outer edge of the bottom portion,   four discharge holes are formed in the discharge portion,   two discharge holes are arranged side by side in a width direction in each of the regions in the bottom portion of the discharge portion,   the discharge portion includes:   an internal barrier that is disposed at the center in the width direction and that distributes the molten steel supplied from the tundish to each of the regions;   a branch flow passage through which a branch flow, which is the molten steel that has been distributed by the internal barrier, flows between the side wall of each of the regions and the internal barrier; and   a distribution block, on a bottom portion side relative to the internal barrier, that further distributes the branch flow that has passed through the branch flow passage to a distribution flow passage in each of the regions to supply the branch flow to each of the discharge holes,   in a case where out of the two discharge holes disposed in each of the regions, the discharge hole disposed on an outer side in the width direction is defined as an outer discharge hole, the discharge hole disposed on an inner side in the width direction is defined as an inner discharge hole, and when either one of the branch flow passages is closed, a relationship between a flow rate Qa of the molten steel to be discharged from the inner discharge hole disposed in a region where the branch flow passage is closed and a flow rate Qb of the molten steel to be discharged from the inner discharge hole disposed in a region in which the branch flow passage is not closed satisfies an equation (1), and   a relationship between a discharge flow rate Q out  of the molten steel to be discharged from the outer discharge hole and a discharge flow rate Q IN  of the molten steel to be discharged from the inner discharge hole satisfies an equation (2).   
       
         
           
             
               
                 
                   
                     
                       Qa 
                       / 
                       Qb 
                     
                     > 
                     1. 
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         
           
             
               
                 
                   
                     
                       0.1 
                     
                     ≤ 
                     
                       
                         Q 
                         IN 
                       
                       / 
                       
                         Q 
                         out 
                       
                     
                     ≤ 
                     
                       1. 
                       . 
                     
                   
                 
                 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
     
         2 . The immersion nozzle according to  claim 1 , wherein
 the immersion nozzle includes a straight body portion that receives the molten steel supplied from the tundish, the discharge portion, and a connection portion that connects the straight body portion with the discharge portion, and   a projection area of the internal barrier, when the immersion nozzle is projected on a horizontal plane, is equal to or larger than a flow passage area of the straight body portion.   
     
     
         3 . The immersion nozzle according to  claim 1 , wherein
 a surface of the internal barrier on a side that receives the molten steel supplied from the tundish includes a recessed portion.   
     
     
         4 . The immersion nozzle according to  claim 1 , wherein
 in each of the regions, an outer discharge angle α1, which is defined by an angle of a wall surface that forms the outer discharge hole, is between equal to or larger than downward 40 degrees and equal to or smaller than downward 75 degrees, and a relationship between α1 and an inner discharge angle α2, which is defined by an angle of a wall surface that forms the inner discharge hole, satisfies an equation (3).
   −5 degrees≤|α2|−|α1|≤15 degrees  (3)
 
   
     
     
         5 . The immersion nozzle according to  claim 2 , wherein
 a value obtained by dividing a flow passage area of the branch flow passage by a flow passage area of the straight body portion is equal to or larger than 0.4 and equal to or smaller than 1.5.   
     
     
         6 . The immersion nozzle according to  claim 2 , wherein
 a value obtained by dividing a flow passage area of the distribution flow passage by a flow passage area of the straight body portion is equal to or larger than 0.3 and equal to or smaller than 1.5.   
     
     
         7 . The immersion nozzle according to  claim 2 , wherein
 a surface of the internal barrier on a side that receives the molten steel supplied from the tundish includes a recessed portion.   
     
     
         8 . The immersion nozzle according to  claim 2 , wherein
 in each of the regions, an outer discharge angle α1, which is defined by an angle of a wall surface that forms the outer discharge hole, is between equal to or larger than downward 40 degrees and equal to or smaller than downward 75 degrees, and a relationship between α1 and an inner discharge angle α2, which is defined by an angle of a wall surface that forms the inner discharge hole, satisfies an equation (3).   
       
         
           
             
               
                 
                   
                     
                       
                         - 
                         5 
                       
                       ⁢ 
                           
                       degrees 
                     
                       
                     ≤ 
                     
                       
                         
                           ❘ 
                           "\[LeftBracketingBar]" 
                         
                         α2 
                         
                           ❘ 
                           "\[RightBracketingBar]" 
                         
                       
                       - 
                       
                         
                           ❘ 
                           "\[LeftBracketingBar]" 
                         
                         α1 
                         
                           ❘ 
                           "\[RightBracketingBar]" 
                         
                       
                     
                     ≤ 
                     
                       15 
                       ⁢ 
                           
                       degrees 
                     
                   
                 
                 
                   
                     ( 
                     3 
                     )