US 12,168,808 B2
Degassing method for manufacturing ultra-low carbon, nitrogen, sulfur steel
Yun Li, Murrysville, PA (US); David L. Runner, Louisville, KY (US); Jonathan D. Youngblood, Southaven, MS (US); and Scott R. Story, Pittsburgh, PA (US)
Assigned to United States Steel Corporation, Pittsburgh, PA (US)
Filed by United States Steel Corporation, Pittsburgh, PA (US)
Filed on Aug. 29, 2022, as Appl. No. 17/897,824.
Claims priority of provisional application 63/237,636, filed on Aug. 27, 2021.
Prior Publication US 2023/0093078 A1, Mar. 23, 2023
Int. Cl. C21C 7/068 (2006.01); C21C 5/52 (2006.01); C21C 7/00 (2006.01); C21C 7/06 (2006.01); C21C 7/064 (2006.01); C22C 38/00 (2006.01)
CPC C21C 7/068 (2013.01) [C21C 5/52 (2013.01); C21C 7/0075 (2013.01); C21C 7/06 (2013.01); C21C 7/064 (2013.01); C22C 38/004 (2013.01)] 7 Claims
 
1. A method of making an ultra-low carbon steel product comprising:
tapping liquid steel out of a primary steelmaking furnace;
transferring the liquid steel to a ladle metallurgy furnace;
deoxidizing the liquid steel in the ladle metallurgy furnace producing killed deoxidized liquid steel and removing sulfur from the killed deoxidized liquid steel in the ladle metallurgy furnace to prevent carbon pick up;
adding a slag thickening material and a reducing agent containing aluminum into the killed deoxidized liquid steel prior to transferring the killed deoxidized liquid steel to a RH degasser to prevent sulfur reversion during decarburization at the RH degasser; and
transferring the killed deoxidized liquid steel from the ladle metallurgy furnace to the RH degasser and oxidizing the killed deoxidated liquid steel in the RH degasser to remove carbon from the oxidized liquid steel to produce decarburized liquid steel comprising 0.003 wt. % 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.