Method for producing grained iron, and grained iron

Patent metadata

Field	Value
Publication number	US-2025243554-A1
Application number	US-202318854104-A
Country	US
Kind code	A1
Filing date	Apr 10, 2023
Priority date	Apr 22, 2022
Publication date	Jul 31, 2025
Grant date	—

Abstract

A method capable of efficiently producing grained iron with a low P concentration includes a first step of melting reduced iron to obtain primary molten iron, a second step of separating the primary molten iron from slag, a third step of subjecting the primary molten iron separated from the slag to dephosphorization to obtain secondary molten iron, and a fourth step of solidifying the secondary molten iron into a grained form to obtain grained iron, in which in the third step, the dephosphorization is performed by supplying an oxygen source and a CaO source to the primary molten iron, and a temperature of the secondary molten iron at the end of the dephosphorization is set to a temperature of the primary molten iron at the start of the dephosphorization or lower.

First claim

1 . A method for producing grained iron, comprising:
a first step of melting reduced iron to obtain primary molten iron; a second step of separating the primary molten iron from slag; a third step of subjecting the primary molten iron separated from the slag to dephosphorization to obtain secondary molten iron; and a fourth step of solidifying the secondary molten iron into a grain form to obtain grained iron, wherein:
in the third step, the dephosphorization is performed by supplying an oxygen source and a CaO source to the primary molten iron, and a temperature of the secondary molten iron at the end of the dephosphorization is set to a temperature of the primary molten iron at the start of the dephosphorization or lower.

2 . The method for producing grained iron according to claim 1 , wherein a temperature T f of the secondary molten iron at the end of the dephosphorization is set higher than a solidifying temperature T m of the secondary molten iron at the end of the dephosphorization by 20° C. or more.

3 . The method for producing grained iron according to claim 1 , wherein a composition of the slag at the end of the dephosphorization is set to have a slag basicity in a range of 1.0 to 4.0, wherein the slag basicity is a ratio of a CaO concentration (% CaO) to a SiO 2 concentration (% SiO 2 ) on a mass basis.

4 . The method for producing grained iron according to claim 1 , wherein
the fourth step is performed using a grained iron producing apparatus including a granulation device that forms the secondary molten iron into droplets, a water-flow control vessel that is disposed at a position for receiving the droplets and accommodates cooling water, and at least one cooling water pipe that is connected to the water-flow control vessel and supplies cooling water to the water-flow control vessel, and the water-flow control vessel includes an inclined surface that is inclined such that a horizontal cross-sectional area of the water-flow control vessel becomes narrower in a downward direction, and a discharge port is provided below the inclined surface.

5 . Grained iron produced from reduced iron with a P concentration of 0.050 mass % or more as a raw material,
wherein
a P concentration of the grained iron is 0.030 mass % or less, and size grain of the grained iron is in the range of 1 mm to 50 mm inclusive.

6 . The method for producing grained iron according to claim 2 , wherein a composition of the slag at the end of the dephosphorization is set to have a slag basicity in a range of 1.0 to 4.0, wherein the slag basicity is a ratio of a CaO concentration (% CaO) to a SiO 2 concentration (% SiO 2 ) on a mass basis.

Assignees

• Jfe Steel Corp

Inventors

• Sugino Tomohiro
• Nakase Kenji
• Ogasawara Futoshi
• Kawabata Ryo

Classifications

• C21C7/0645 Primary

  Agents used for dephosphorising or desulfurising · CPC title

• C21C1/02

  Dephosphorising or desulfurising · CPC title

• C21B13/0006 Primary

  obtaining iron or steel in a molten state · CPC title

• C21B13/00

  Making spongy iron or liquid steel, by direct processes · CPC title

• C21B11/00

  Making pig-iron other than in blast furnaces · CPC title