US 12,276,002 B2
Molten steel production method
Koji Tokuda, Kobe (JP); and Tsuyoshi Mimura, Kobe (JP)
Assigned to Kobe Steel, Ltd., Kobe (JP)
Appl. No. 17/777,071
Filed by Kobe Steel, Ltd., Kobe (JP)
PCT Filed Dec. 11, 2020, PCT No. PCT/JP2020/046303
§ 371(c)(1), (2) Date May 16, 2022,
PCT Pub. No. WO2021/131799, PCT Pub. Date Jul. 1, 2021.
Claims priority of application No. 2019-234093 (JP), filed on Dec. 25, 2019.
Prior Publication US 2022/0396844 A1, Dec. 15, 2022
Int. Cl. C21C 7/068 (2006.01); C21C 5/52 (2006.01)
CPC C21C 7/068 (2013.01) [C21C 5/527 (2013.01); C21C 2300/08 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A method for producing a molten steel using a solid-state direct reduced iron as a raw material,
the method comprising:
a slag separation comprising heating and melting the solid-state direct reduced iron in an electric furnace without introducing oxygen to separate into a molten steel and a slag, and continuously discharging the slag from the electric furnace; and
a decarburization comprising blowing, in the electric furnace, a total amount of oxygen introduced into the electric furnace to the molten steel to decarburize after the slag separation,
wherein the decarburization is started when 50% to 80% of a total time for performing the slag separation and the decarburization has elapsed from a start of the slag separation,
wherein the solid-state direct reduced iron comprises 3.0% by mass or more of SiO2 and Al2O3 in total and 1.0% by mass or more of carbon,
wherein a ratio of a metallic iron to a total iron content comprised in the solid-state direct reduced iron is 90% by mass or more, and
wherein an excess carbon content Cx specified by formula (1) to the carbon comprised in the solid-state direct reduced iron is 0.2% by mass or more:
Cx=[C]−[FeO]×12÷(55.85+16)÷0.947  (1)
wherein, in the formula (1),
Cx is excess carbon content in mass %, [C] is carbon content of solid-state direct reduced iron in mass %, and [FeO] is FeO content of solid-state direct reduced iron in mass %.