Method for refining molten iron

Patent metadata

Field	Value
Publication number	US-2024271233-A1
Application number	US-202218289918-A
Country	US
Kind code	A1
Filing date	Apr 19, 2022
Priority date	May 26, 2021
Publication date	Aug 15, 2024
Grant date	—

Abstract

A method for refining molten iron that can stably produce low-nitrogen steel is proposed. In this method for refining molten iron, untreated molten iron with a carbon concentration [C] i between 0.5 mass % and 3.0 mass %, both inclusive, is placed into a vessel, and oxygen is blown onto the untreated molten iron under atmospheric pressure while a hydrogen gas, a hydrocarbon gas, or a mixture gas of these gases is blown in to perform a decarburization and denitrification treatment of the untreated molten iron. It is preferable, for example, that a nitrogen concentration [N] f in treated molten iron after being subjected to the decarburization and denitrification treatment be 30 mass ppm or lower; that treated molten iron after being subjected to the decarburization and denitrification treatment be further subjected to a vacuum degassing treatment; that the untreated molten iron include molten iron obtained by melting a cold iron source; that the untreated molten iron be a mixture of primary molten iron obtained by melting a cold iron source in a melting furnace and molten pig iron having a carbon concentration of 2.0 mass % or higher; that the cold iron source include reduced iron; and that the vessel be a converter.

First claim

1 . A method for refining molten iron, wherein
untreated molten iron with a carbon concentration [C] i between 0.5 mass % and 3.0 mass %, both inclusive, is placed into a vessel, and oxygen is blown onto the untreated molten iron under atmospheric pressure while a hydrogen gas, a hydrocarbon gas, or a mixture gas of these gases is blown in to perform a decarburization and denitrification treatment of the untreated molten iron.

2 . The method for refining molten iron according to claim 1 , wherein a nitrogen concentration [N] f in treated molten iron after being subjected to the decarburization and denitrification treatment is 30 mass ppm or lower.

3 . The method for refining molten iron according to claim 1 , wherein
treated molten iron after being subjected to the decarburization and denitrification treatment is further subjected to a vacuum degassing treatment.

4 . The method for refining molten iron according to claim 1 , wherein
the untreated molten iron includes molten iron obtained by melting a cold iron source.

5 . The method for refining molten iron according to claim 1 , wherein
the untreated molten iron is a mixture of primary molten iron obtained by melting a cold iron source in a melting furnace and molten pig iron having a carbon concentration of 2.0 mass % or higher.

6 . The method for refining molten iron according to claim 4 , wherein
the cold iron source includes reduced iron.

7 . The method for refining molten iron according to claim 1 , wherein
the vessel is a converter.

8 . The method for refining molten iron according to claim 2 , wherein
treated molten iron after being subjected to the decarburization and denitrification treatment is further subjected to a vacuum degassing treatment.

9 . The method for refining molten iron according to claim 2 , wherein
the untreated molten iron includes molten iron obtained by melting a cold iron source.

10 . The method for refining molten iron according to claim 3 , wherein
the untreated molten iron includes molten iron obtained by melting a cold iron source.

11 . The method for refining molten iron according to claim 8 , wherein
the untreated molten iron includes molten iron obtained by melting a cold iron source.

12 . The method for refining molten iron according to claim 2 , wherein
the untreated molten iron is a mixture of primary molten iron obtained by melting a cold iron source in a melting furnace and molten pig iron having a carbon concentration of 2.0 mass % or higher.

13 . The method for refining molten iron according to claim 3 , wherein
the untreated molten iron is a mixture of primary molten iron obtained by melting a cold iron source in a melting furnace and molten pig iron having a carbon concentration of 2.0 mass % or higher.

14 . The method for refining molten iron according to claim 8 , wherein
the untreated molten iron is a mixture of primary molten iron obtained by melting a cold iron source in a melting furnace and molten pig iron having a carbon concentration of 2.0 mass % or higher.

15 . The method for refining molten iron according to claim 5 , wherein
the cold iron source includes reduced iron.

Assignees

• Jfe Steel Corp

Inventors

• Ogasawara Futoshi
• Kawabata Ryo

Classifications

• C21C7/10 Primary

  Handling in a vacuum · CPC title

• C21C7/072

  Treatment with gases (C21C7/06, C21C7/064, C21C7/068 take precedence) · CPC title

• C21C5/28 Primary

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

• C21C7/068 Primary

  Decarburising · CPC title

• C21C5/35

  Blowing from above and through the bath · CPC title