Degassing method for manufacturing ultra-low carbon, nitrogen, sulfur steel

Abstract

The present disclosure provides a method of making low carbon steel. The method includes tapping the liquid steel out of a primary steelmaking furnace. Deoxidizing the liquid steel. Transferring the deoxidized liquid steel to a ladle metallurgy furnace. Removing sulfur at the ladle metallurgy furnace. Adding fluxes and arcing the liquid steel to prevent sulfur reversion. Transferring the liquid steel from the ladle metallurgy furnace to an RH degasser for carbon removal. The removal of oxygen and sulfur prior to transferring the liquid steel to the RH degasser facilitates nitrogen removal and prevents carbon pick up during the step sulfur removal.

What is claimed is: 
     
         1 . A method of making low carbon steel, comprising:
 tapping the liquid steel out of a primary steelmaking furnace;   deoxidizing the liquid steel producing killed steel;   transferring the killed deoxidized liquid steel to a ladle metallurgy furnace;   removing sulfur from the killed deoxidized liquid steel at the ladle metallurgy furnace;   adding fluxes and arcing the killed deoxidized liquid steel to prevent sulfur reversion; and   transferring the killed deoxidized liquid steel from the ladle metallurgy furnace to an RH degasser for carbon removal to produce decarburized liquid steel comprising 0.003 weight percent or less carbon, wherein the removal of oxygen and sulfur prior to transferring the liquid steel to the RH degasser facilitates nitrogen removal and prevents carbon pick up during the step of removing sulfur.   
     
     
         2 . The method of making low carbon steel of  claim 1 , wherein the sulfur is removed to 0.003 weight percent or less. 
     
     
         3 . The method of making low carbon steel of  claim 1 , further comprising removing nitrogen while the liquid steel is in the RH degasser. 
     
     
         4 . The method of making low carbon steel of  claim 3 , wherein the nitrogen is removed to 0.003 weight percent or less. 
     
     
         5 . The method of making low carbon steel of  claim 3 , wherein the low sulfur weight percent obtained at the ladle metallurgy furnace accelerates nitrogen removal at the RH degasser. 
     
     
         6 . The method of making low carbon steel of  claim 1 , further comprising removing hydrogen while the liquid steel is in the RH degasser. 
     
     
         7 . The method of making low carbon steel of  claim 1 , further comprising removing aluminum and silicon by blowing oxygen through a top lance or tuyeres of the RH degasser. 
     
     
         8 . The method of making low carbon steel of  claim 7 , further comprising removing carbon while the liquid steel is in the RH degasser after the step of removing aluminum and silicon through oxidation. 
     
     
         9 . The method of making low carbon steel of  claim 7 , wherein the amount of oxygen blown into the RH degasser is approximately 200 ppm to prevent sulfur reversion from slag. 
     
     
         10 . The method of making low carbon steel of  claim 1 , adding alloys to the liquid steel in the RH degasser. 
     
     
         11 . The method of making low carbon steel of  claim 1 , further comprising the step of adding a reducing agent to prevent the sulfur reversion. 
     
     
         12 . A steel sheet product produced by the method of  claim 1 .