Refinement of steel

Abstract

A cast low carbon steel formed by a method of forming and refining molten silicon-bearing steel by addition of a calcium-containing silicon additive. Determine when the amount of calcium in the calcium-containing silicon additive is more or less than the amount of calcium desired in the finished steel. When it is more than the amount of calcium desired in the finished steel, add the amount of calcium-containing silicon additive corresponding to the excess calcium early during steel deoxidation or in refining to combine with oxygen, sulfur and other impurities in refining, and add the calcium-containing silicon additive containing the total amount of calcium desired in the finished steel after the desulfurization of the molten steel and before casting. When the amount of calcium in the calcium-containing silicon additive does not provide the total amount of calcium desired in the finished steel, add an additional amount of calcium after desulfurization of the molten steel and before casting to the molten steel during refining.

1 . A cast low carbon steel made by the method comprising the steps of:
 a) refining molten steel to make a silicon-bearing steel having a silicon content between 0.1% and 1.5% by weight by addition of a calcium-containing silicon additive;   b) determining the amount of calcium content in the calcium-containing silicon additive;   c) determining whether the amount of calcium in the calcium-containing silicon additive is more or less than the amount of calcium desired in the finished steel;   d) when the amount of calcium in the calcium-containing silicon additive is more than the amount of calcium desired in the finished steel, adding the amount of calcium-containing silicon additive corresponding to the excess calcium early in the refining to combine with sulfur and other impurities in the steel during the refining;   e) desulfurizing the molten steel;   f) adding the calcium-containing silicon additive containing the total amount of calcium desired in the finished steel after desulfurization of the molten steel and before casting;   g) when the amount of calcium in the calcium-containing silicon additive does not provide the total amount of calcium desired in the finished steel, adding an additional amount of calcium after desulfurization of the molten steel and before casting to the molten steel during refining; and   h) casting the finished steel into slabs of steel.   
     
     
         2 . The cast low carbon steel as claimed in  claim 1  where the silicon-bearing steel contains between 0.003 and 0.5% of carbon. 
     
     
         3 . The cast low carbon steel as claimed in  claim 1  made by the method further comprising the steps of:
 i) determining an amount of aluminum in the calcium-containing silicon additive; and   j) utilizing the amount of aluminum in the calcium-containing additive in deoxidizing the molten silicon-bearing steel in refining.   
     
     
         4 . The cast low carbon steel as claimed in  claim 1  where the silicon-bearing steel is selected from the group consisting of Al-killed steel and Al—Si dual killed steel. 
     
     
         5 . The cast low carbon steel as claimed in  claim 1  made by the method further comprising adding a manganese-containing additive early in the refining. 
     
     
         6 . The cast low carbon steel as claimed in  claim 1  where the silicon content is between 0.1% and 0.5% by weight.