(19)
(11) EP 0 322 763 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
07.02.1990 Bulletin 1990/06

(43) Date of publication A2:
05.07.1989 Bulletin 1989/27

(21) Application number: 88121503.2

(22) Date of filing: 22.12.1988
(51) International Patent Classification (IPC)4: C21C 7/072, C21C 1/00, C22B 9/05
(84) Designated Contracting States:
DE FR GB IT

(30) Priority: 25.12.1987 JP 326722/87
25.12.1987 JP 326723/87
12.01.1988 JP 3112/88
12.01.1988 JP 3113/88

(71) Applicant: NKK CORPORATION
Tokyo (JP)

(72) Inventors:
  • Ishii, Toshio c/o Patent & License and
    Marunouchi Chiyoda-ku Tokyo (JP)
  • Okubo, Yutaka c/o Patent & License and
    Marunouchi Chiyoda-ku Tokyo (JP)
  • Fukuda, Shuzo c/o Patent & License and
    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)


(56) References cited: : 
   
       


    (54) Method for cleaning molten metal and apparatus therefor


    (57) A method for cleaning molten metal comprises a bubbling process, wherein the gas soluble in molten metal is bubbled in the molten metal under increased pressure, the inclusions in the molten metal are trapped by the gas bubbles produced by bubbling, and the gas is dissolved in the molten metal; a pressure reduction process, wherein fine gas bubbles are produced in the molten metal by reducing a pressure on the molten metal in which gas is dissolved, and the inclusions suspended in the molten metal are trapped by the fine gas bubbles produced by reduction of the pressure; and an inclusions removing process, wherein inclusions having risen to the surface of the molten metal are removed. An apparatus comprises a first vessel (30) which has an inlet (32) for charging molten metal at the top end thereof and outlet (34) for charging molten metal at the bottom thereof; a second vessel (40) which has an inflow port(38) for pressurized molten metal at the bottom thereof and an outflow port (42) for the pressurized molten metal and in which the pressurized molten metal goes upwardly; a communicating tube (36) connecting the first vessel to the second vessel; and a first bubbling device (44) positioned at the bottom of the first vessel for bubbling the gas soluble in molten metal.







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