| (19) |
 |
|
(11) |
EP 0 325 242 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
|
14.02.1990 Bulletin 1990/07 |
| (43) |
Date of publication A2: |
|
26.07.1989 Bulletin 1989/30 |
| (22) |
Date of filing: 19.01.1989 |
|
| (51) |
International Patent Classification (IPC)4: C21C 7/10 |
|
| (84) |
Designated Contracting States: |
|
DE FR GB IT |
| (30) |
Priority: |
21.01.1988 JP 9675/88
|
| (71) |
Applicant: NKK CORPORATION |
|
Tokyo (JP) |
|
| (72) |
Inventors: |
|
- Ishii, Toshio,
c/o NKK Corporation
Marunouchi,
Chiyoda-ku, Tokyo (JP)
- Okubo, Yutaka,
c/o NKK Corporation
Marunouchi,
Chiyoda-ku, Tokyo (JP)
- Fukuda, Shuzo,
c/o NKK Corporation
Marunouchi,
Chiyoda-ku, Tokyo (JP)
- Kawai, Yoshihiko,
c/o NKK Corporation
Marunouchi,
Chiyoda-ku, Tokyo (JP)
|
| (74) |
Representative: Füchsle, Klaus, Dipl.-Ing. et al |
|
Hoffmann, Eitle & Partner,
Patentanwälte,
Postfach 81 04 20
81904 München
81904 München (DE) |
|
| |
|
| (54) |
Method for refining molten steel in a vacuum |
(57) A method for refining molten steel in a vacuum comprises an immersion process, wherein
two immersion nozzles (5) (6) arranged at the lower portion of a vacuum vessel (4)
are immersed in molten steel (2) in a ladle (1); a dissolving process, wherein gases
are dissolved in molten steel by blowing gases containing at least gas soluble in
the molten steel from a gas blow-in opening (3) arranged in a ladle (1) in the molten
steel; a first degassing process, wherein the molten steel is degassed by keeping
the the vacuum vessel evacuated, having the molten steel circulated between the ladle
and the vacuum vessel by injecting gases containing at least an inert gas from the
middle (7) of the rising tube (5) and blowing gases containing at least gas soluble
in the molten steel from a gas blow-in opening (3) arranged in the ladle (1); and
a second degassing process, wherein the molten steel is degassed by keeping the vacuum
vessel evacuated, stopping a gas blow-in from the gas blow-in opening (3) arranged
in the ladle (1) and having the molten steel circulated between the ladle and the
vacuum vessel by injecting gases containing at least an inert gas from the middle
(7) of the rising tube (5) in the molten steel (1).
