Method for producing molten steel

Patent metadata

Field	Value
Publication number	US-2022389527-A1
Application number	US-202017775502-A
Country	US
Kind code	A1
Filing date	Nov 11, 2020
Priority date	Nov 21, 2019
Publication date	Dec 8, 2022
Grant date	—

Abstract

In a method for producing a molten steel according to one aspect of the present invention, the solid-state direct reduced iron contains 3.0% by mass or more of SiO2 and Al2O3 in total and 1.0% by mass or more of carbon. A ratio of a metallic iron to the total iron content contained in the solid-state direct reduced iron is 90% by mass or more, and an excess carbon content Cx is 0.2% by mass or more to the carbons contained in the solid-state direct reduced iron. The method includes a step in a first furnace of melting 40 to 100% by mass of the solid-state direct reduced iron, and separating a molten pig iron having a carbon content of 2.0 to 5.0% by mass and a temperature of 1350 to 1550° C. and a slag having a basicity of 1.0 to 1.4 and a step in a second furnace of melting a remainder of the solid reduced iron together with the molten pig iron separated in the first furnace and blowing oxygen onto the molten material to decarburize into a molten steel.

First claim

1 . A method for producing a molten steel using a solid-state direct reduced iron as a raw material, wherein
the solid-state direct reduced iron contains 3.0% by mass or more of SiO 2 and Al 2 O 3 in total and 1.0% by mass or more of carbon, a ratio of a metallic iron to the total iron content contained in the solid-state direct reduced iron is 90% by mass or more, and an excess carbon content Cx specified by the following formula (1) to the carbons contained in the solid-state direct reduced iron is 0.2% by mass or more, the method comprising: a step in a first furnace of melting 40 to 100% by mass of the solid-state direct reduced iron, and separating a molten pig iron having a carbon content of 2.0 to 5.0% by mass and a temperature of 1350 to 1550° C. and a slag having a basicity of 1.0 to 1.4 and a step in a second furnace of melting a remainder of the solid-state direct reduced iron together with the molten pig iron separated in the first furnace, and blowing oxygen onto the molten material to decarburize into a molten steel,
Cx=[C]−[FeO]×12÷(55.85+16)÷0.947  (1)

in the formula, Cx: excess carbon content (% by mass), [C]: carbon content of solid-state direct reduced iron (% by mass), [FeO]: FeO content of solid-state direct reduced iron (% by mass).

2 . The method for producing a molten steel according to claim 1 , wherein the solid-state direct reduced iron is melted by an arc in the first furnace, and the molten pig iron and the slag are continuously discharged respectively from the first furnace.

Assignees

• Kobe Steel Ltd

Inventors

• Tokuda Koji
• Mimura Tsuyoshi

Classifications

• C21C1/00

  Refining of pig-iron; Cast iron · CPC title

• C21B11/10 Primary

  in electric furnaces · CPC title

• C21C7/068

  Decarburising · CPC title

• C21B13/143

  Injection of partially reduced ore into a molten bath · CPC title

• C21C5/52 Primary

  Manufacture of steel in electric furnaces {(C21C5/005 takes precedence)} · CPC title