Submerged nozzle for continuous thin-slab casting

Abstract

A submerged nozzle for continuous thin-slab casting by which a high quality thin-slab strand may be stably supplied for a long time in a continuous manner is provided, as a drift current and surface fluctuation of molten steel in the nozzle and a mold are prevented, and adhesion of ground metal to the nozzle, the damages of the nozzle and the like are suppressed even under long time use. In the submerged nozzle for continuous thin-slab casting, which comprises: a molten steel entrance port at the upper end; a molten steel stream channel with a shape of a tube extending downward from the molten steel entrance port; and a molten steel discharge opening at the lower end and in which the molten steel stream channel includes an upper section with a shape of a circular cylinder, an intermediate section with a transforming shape from a shape of a circular cylinder to a shape of a flat cylinder, and a lower section with a shape of a flat and straight tube, a cross sectional area at the flat and straight tube section in the lower section is configured to be equal to or larger than 95% or equal to or less than 105% of a cross sectional area at the cylindrical section in the upper section of the molten steel stream channel.

What claimed is:  
     
         1 . A submerged nozzle for continuous thin-slab casting, which comprises: a molten steel entrance port at the upper end; a molten steel stream channel with a shape of a tube extending downward from the molten steel entrance port; and a molten steel discharge opening at the lower end and in which the molten steel stream channel includes an upper section with a shape of a circular cylinder, an intermediate section with a transforming shape from a shape of a circular cylinder to a shape of a flat cylinder, and a lower section with a shape of a flat and straight tube, wherein 
 a cross sectional area at the flat and straight tube section in the lower section is equal to or larger than 95% or equal to or less than 105% of a cross sectional area at the cylindrical section in the upper section of the molten steel stream channel.    
     
     
         2 . A submerged nozzle for continuous thin-slab casting, which comprises: a molten steel entrance port at the upper end; a molten steel stream channel with a shape of a tube extending downward from the molten steel entrance port; and a molten steel discharge opening at the lower end and in which the molten steel stream channel includes an upper section with a shape of a circular cylinder, an intermediate section with a transforming shape from a shape of a circular cylinder to a shape of a flat cylinder, and a lower section with a shape of a flat and straight tube, wherein 
 the intermediate section of the molten steel stream channel is provided with a taper shape thickened toward the end at the long side and a taper shape diminished toward the end at the short side and has a configuration in which the position of the starting point of the taper at the long side and that of the starting point of the taper at the short side, and that of the terminal point of the taper at the long side and that of the terminal point of the taper at the short side are different from each other with regard to their heights,    a spill port is provided at the bottom center in the bottom wall of the nozzle, and the port area of the spill port is within the range of equal to or larger than 20% through equal to or less than 40% of the cross sectional area at the straight tube section in the lower section of the molten steel stream channel.    
     
     
         3 . The submerged nozzle for continuous thin-slab casting according to  claim 2 , wherein 
 the cross sectional area at the flat and straight tube section in the lower section is equal to or larger than 95% or equal to or less than 105% of the cross sectional area at the cylindrical section in the upper section of the molten steel stream channel.    
     
     
         4 . The submerged nozzle for continuous thin-slab casting according to  claim 1 , wherein 
 at least a section which is submerged in molten steel is formed of a fire resistant material which does not contain silica glass.    
     
     
         5 . The submerged nozzle for continuous thin-slab casting according to  claim 2 , wherein 
 at least a section which is submerged in molten steel is formed of a fire resistant material which does not contain silica glass.    
     
     
         6 . The submerged nozzle for continuous thin-slab casting according to any one of claims  1 , wherein 
 the position of the terminal point of the taper at the long side and that of the terminal point of the taper at the short side are different from each other by equal to or larger than 10 mm with regard to their heights in the intermediate section of the molten steel stream channel.    
     
     
         7 . The submerged nozzle for continuous thin-slab casting according to  claim 2 , wherein 
 the position of the terminal point of the taper at the long side and that of the terminal point of the taper at the short side are different from each other by equal to or larger than 10 mm with regard to their heights in the intermediate section of the molten steel stream channel.    
     
     
         8 . The submerged nozzle for continuous thin-slab casting according to any one of claims  1 , wherein 
 the molten steel discharge opening is formed between the side wall of the nozzle lower end at the short side and the side part of the plane-like bottom wall, and    an angle α between the side wall of the nozzle at the lower end, which forms the molten steel discharge opening and the horizontal plane, and an angle β between the side part of the bottom wall, which forms the molten steel discharge opening and the horizontal plane are as follows:    0°≦α≦60° 30 °≦β≦ 80 °.    
     
     
         9 . The submerged nozzle for continuous thin-slab casting according to  claim 2 , wherein 
 the molten steel discharge opening is formed between the side wall of the nozzle lower end at the short side and the side part of the plane-like bottom wall, and    an angle α between the side wall of the nozzle at the lower end, which forms the molten steel discharge opening and the horizontal plane, and an angle β between the side part of the bottom wall, which forms the molten steel discharge opening and the horizontal plane are as follows:    0°≦α≦60°30°≦β≦80°.    
     
     
         10 . The submerged nozzle for continuous thin-slab casting according to any one of claims  8 , wherein 
 a notch in the direction of the long side at the bottom wall of the nozzle is between equal to or larger than 75% and equal to or less than 200% of the thickness of the sidewall at the short side in length.    
     
     
         11 . The submerged nozzle for continuous thin-slab casting according to  claim 9 , wherein 
 a notch in the direction of the long side at the bottom wall of the nozzle is between equal to or larger than 75% and equal to or less than 200% of the thickness of the sidewall at the short side in length.