Nozzle for continuous casting of aluminum killed steel and continuous casting method

Abstract

The present invention provides a technique of applying a CaO-containing material to a nozzle unit for casting of aluminum-killed steel, in such a manner that the amount of large-size alumina inclusions in slabs can be reduced irrespective of nozzle type, such as single-part type or multi-part type. The amount of large-size alumina inclusions in slabs obtained using a single-part type or multi-part type nozzle unit, which has an inner hole to be used for pouring molten steel from a tundish to a mold therethrough and CaO-containing refractories applied to a surface of the inner hole, has a strong correlation with the entire surface area of the inner hole of the nozzle unit and the amount of CaO contained in the employed refractories. According to the present invention, 50% or more of the entire surface area of the inner hole of the nozzle unit is formed of refractories containing 20 mass % or more of CaO to allow the amount of large-size alumina inclusions to be reduced.

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       6 . A method for providing to a continuous casing nozzle unit a function of preventing the attachment of alumina and a function of reducing large-size inclusions in slabs, comprising applying CaO-containing refractories to a surface of an inner hole of said continuous casting nozzle unit, while correlating said function of preventing the attachment of alumina and said function of reducing large-size inclusions in slabs, with the ratio of a surface area of said inner hole to be defined by said CaO-containing refractories to the entire surface area of said inner hole and the amount of CaO to be contained in said CaO-containing refractories, wherein according to said correlation, said amount of CaO to be contained in said CaO-containing refractories is set at 20 mass % or more, and said ratio of a surface area of said inner hole to be defined by said CaO-containing refractories to the entire surface area of said inner hole is set at 50% or more.  
   
   
       7 . The method as defined in  claim 6 , wherein said CaO-containing refractories are sleeve-shaped sintered refractories, wherein said method includes inserting said sleeve-shaped sintered refractories into said inner hole.  
   
   
       8 . A continuous casting nozzle unit comprising CaO-containing refractories applied to a surface of an inner hole of said continuous casting nozzle unit so as to provide a function of preventing the attachment of alumina and a function of reducing large-size inclusions in slabs, wherein said function of preventing the attachment of alumina and said function of reducing large-size inclusions in slabs are provided in correlation with the ratio of a surface area of said inner hole to be defined by said CaO-containing refractories to the entire surface area of said inner hole, and the amount of CaO to be contained in said CaO-containing refractories, wherein according to said correlation, said amount of CaO to be contained in said CaO-containing refractories is set at 20 mass % or more, and said ratio of a surface area of said inner hole to be defined by said CaO-containing refractories to the entire surface area of said inner hole is set at 50% or more.  
   
   
       9 . The continuous casting nozzle unit as defined in  claim 8 , wherein said CaO-containing refractories are sleeve-shaped sintered refractories.  
   
   
       10 . The continuous casting nozzle unit as defined in  claim 9 , which is a multi-part type or single-part type nozzle unit for continuous casting of aluminum-killed steel.  
   
   
       11 . A method of continuous casting of aluminum-killed steel using a continuous casting nozzle unit which has a function of preventing the attachment of alumina and a function of reducing large-size inclusions in slabs, wherein large-size inclusions in slabs to be caused by pouring molten steel from a tundish to a mold through an inner hole of said continuous casting nozzle unit having CaO-containing refractories applied to a surface of said inner hole is reduced in correlation with the ratio of a surface area of said inner hole to be defined by said CaO-containing refractories to the entire surface area of said inner hole, and the amount of CaO to be contained in said CaO-containing refractories.  
   
   
       12 . The method as defined in  claim 11 , wherein said amount of CaO to be contained in said CaO-containing refractories is 20 mass % or more, and said ratio of a surface area of said inner hole to be defined by said CaO-containing refractories to the entire surface area of said inner hole is 50% or more.  
   
   
       13 . The continuous casting nozzle unit as defined in  claim 8 , which is a multi-part type or single-part type nozzle unit for continuous casting of aluminum-killed steel.