METHOD FOR CONTROLLING Ti CONCENTRATION IN STEEL, AND METHOD FOR PRODUCING SILICON-DEOXIDIZED STEEL

Abstract

Disclosed is a method for controlling a Ti concentration in a steel when manufacturing a silicon-deoxidized steel comprising 0.1 to 3% by mass of Si and 0.0001 to 0.005% by mass of Al by ladle refining of a molten steel, the method including the step of: adding an oxide including TiO 2 to a slag in a ladle during the ladle refining, wherein the slag produced at end of the ladle refining satisfies formulas (1) to (7) below: 0.5≦CaO/SiO 2 ≦1.8  (1) 4% by mass≦Al 2 O 3 ≦20% by mass  (2) MgO≦15% by mass  (3) 1.5% by mass≦TiO 2 ≦10% by mass  (4) CaO+SiO 2 +Al 2 O 3 +MgO+TiO 2 ≧90% by mass  (5) 0.4≦TiO 2 /MnO≦5  (6) 1≦TiO 2 /T.Fe≦10  (7) where a compound represented by a chemical formula represents the content of the compound in percent by mass; and T.Fe represents the total concentration, in mass ratio, of Fe contained in Fe oxides in the slag.

1 . A method for controlling a Ti concentration in a steel when manufacturing a silicon-deoxidized steel comprising 0.1 to 3% by mass of Si and 0.0001 to 0.005% by mass of Al by ladle refining of a molten steel, the method comprising the step of:
 adding an oxide including TiO 2  to a slag in a ladle during the ladle refining,   wherein the slag produced at end of the ladle refining satisfies formulas (1) to (7) below:
   0.5≦CaO/SiO 2 ≦1.8  (1)
 
   4% by mass≦Al 2 O 3 ≦20% by mass  (2)
 
   MgO≦15% by mass  (3)
 
   1.5% by mass≦TiO 2 ≦10% by mass  (4)
 
   CaO+SiO 2 +Al 2 O 3 +MgO+TiO 2 ≧90% by mass  (5)
 
   0.4≦TiO 2 /MnO≦5  (6)
 
   1≦TiO 2 /T.Fe≦10  (7)
 
   
       where a compound represented by a chemical formula represents the content of the compound in percent by mass; and T.Fe represents the total concentration, in mass ratio, of Fe contained in Fe oxides in the slag. 
     
     
         2 . A method for manufacturing a silicon-deoxidized steel comprising 0.1 to 3% by mass of Si and 0.0001 to 0.005% by mass of Al by ladle refining of a molten steel, wherein a Ti concentration in the steel is controlled by the method for controlling a Ti concentration in a steel according to  claim 1 .