| 摘要 |
PURPOSE:To make blowing of steel of a wide range of Cr levels at a good yield of Cr by using a top and bottom blown refining furnace, controlling the flow rate of a bottom blowing gas and oxygen blowing rate from the upper part and quantitatively determining the cross relation between the latter and the transition of the concn. of Cr.C, then executing the blowing. CONSTITUTION:A steel bath of 1,600-1,800 deg.C is subjected to blowing at the flow rate of the bottom blowing gas controlled to >=0.06Nm<3>/min per ton of the molten steel and at the oxygen blowing rate from the upper part controlled to <=3.5 Ko2 (Nm<3>/min/ton of the molten steel) in the stage of producing a high-Cr alloy steel by a top and bottom blown refining method. The blowing is executed by controlling the oxygen blowing rate Ko2 in such a manner that the value of RIDAS expressed by the equation attains 15-30. In the equation, [%Cr], [%C] are respectively the concn. (wt%) of Cr and C in the steel bath. The blowing of the stainless steel in a wide range of Cr levels is thus executed at the good yield of Cr and alloy iron such as ferrosilicon and Al necessary for the reduction of the Cr oxide is reduced. The considerable reduction or elimination of the load of a finish decarburization stage is made possible. |
