Molten steel refining method

Patent metadata

Field	Value
Publication number	US-2024287633-A1
Application number	US-202218570789-A
Country	US
Kind code	A1
Filing date	May 26, 2022
Priority date	Jun 23, 2021
Publication date	Aug 29, 2024
Grant date	—

Abstract

A molten steel refining method. The method includes performing a gas stirring process for stirring molten steel in a ladle by blowing a stirring gas into the molten steel contained in the ladle. In the gas stirring process, a surface of the molten steel, which is in a flow state due to the gas stirring process, in the ladle is subjected to a plasma treatment in which the surface of the molten steel is exposed to a hydrogen gas or an inert gas containing a hydrogen gas in the form of plasma gas from plasma generators above the molten steel in the ladle under conditions that satisfy a specified formula, and the plasma treatment reduces an amount of at least one element selected from oxygen, nitrogen, and sulfur, contained in the molten steel.

First claim

1 . A molten steel refining method comprising:
performing a gas stirring process that stirs molten steel in a ladle into a flow state by blowing a stirring gas into the molten steel contained in the ladle, wherein in the gas stirring process, a surface of the molten steel in the ladle is subjected to a plasma treatment in which the surface of the molten steel is exposed to a hydrogen gas or an inert gas containing a hydrogen gas in a form of plasma gas from a plasma generator above the molten steel in the ladle under conditions that satisfy formula (1):

G
p

×

(

H
2

)

Q

≥
0.05

(
1
)

where G P is a flow rate (Nm 3 /min) of the plasma gas, (H 2 ) is a hydrogen gas concentration (vol %) in the plasma gas, and Q is a molten steel circulation flow rate (ton/min) of the molten steel in the ladle, and
the plasma treatment reduces an amount of at least one element selected from the group consisting of oxygen, nitrogen, and sulfur, contained in the molten steel.

2 . The molten steel refining method according to claim 1 , wherein the molten steel circulation flow rate (Q) of the molten steel in the ladle is calculated according to formulas (2), (3), and (4):

Q
=

W
m

/

t
C

(
2
)

t
C

=

0.555
×

[

(

D
2

/
H

)

2

/
ε

]

0.337

(
3
)

ε
=

6.18
×

G
B

×

T
L

W
m

×

[

In
(

1
+

H

1.95
×

10

-
3

×

P
0

)

+

0.06

(

1
+

298

T
L

)

]

(
4
)

where W m is a mass (ton) of the molten steel in the ladle, t c is a molten steel circulation time (min) of the molten steel in the ladle, D is an average diameter (m) of a molten steel bath in the ladle, H is a depth (m) of the molten steel bath in the ladle, ε is a stirring power (W/ton), G B is a total stirring gas blowing flow rate (Nm 3 /min) into the molten steel in the ladle, T L is a molten steel temperature (K) of the molten steel in the ladle, and P 0 is a pressure (torr) of an atmosphere in a plasma-exposed region.

3 . The molten steel refining method according to claim 1 , wherein the gas stirring process is performed by blowing the stirring gas into the molten steel in the ladle through at least one gas blowing section located at a bottom of the ladle, and a stirring power (ε) in the gas stirring process is 25 W/ton or more, the stirring power ( 8 ) being calculated according to formulas (2), (3), and (4):

Assignees

• Jfe Steel Corp

Inventors

• HARADA Akifumi
• Nakai Yoshie

Classifications

• C21C7/10

  Handling in a vacuum · CPC title

• C21C7/0075

  Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle · CPC title

• C21C7/064

  Dephosphorising; Desulfurising · CPC title

• C21C7/068

  Decarburising · CPC title

• Y02P10/20

  Recycling · CPC title