Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1996-05-09
1998-05-05
Lin, Kuang Y.
Metal founding
Process
Shaping liquid metal against a forming surface
164504, B22D 2702
Patent
active
057462682
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a continuous casting method and apparatus for forming a metal slab with no surface defect, such as a vertical crack, when continuously casting a metal slab made of steel, for example.
BACKGROUND ART
FIG. 1 is a sectional view showing a conventional apparatus for continuously casting a metal slab. In FIG. 1, molten metal 1 is injected from a dipping nozzle 2 to a mold 3. The molten metal is cooled down progressively from the wall surface of the cooled mold 3 to its inner portion. The cooled metal is made to be a coagulated shell 4, which is pulled out of the mold 3 as a metal slab.
FIG. 2 is a plan view showing the apparatus viewed downwardly on the A--A plane of FIG. 1. In FIG. 2, the dipping nozzle 2 is located on the central portion of the horizontal plane of the mold. The molten metal 1 is ejected from a nozzle outlet into the mold and is circulated in the mold as viewed by arrows of FIG. 1. As indicated by real-line arrows of FIGS. 1 and 2, the molten metal is inversely flown from a short side 11 of the mold 3 to the dipping nozzle 2 on the meniscus 5 (top surface of the molten metal).
In the foregoing apparatus for continuously casting a metal slab, a vertical crack is likely to form on the coagulated shell 4 if the temperature of the molten metal varies at substantially the same height of the mold wall surface. To prevent this vertical crack, the JP-A-1-228645 has disclosed that the molten metal is circulated on the meniscus 5 and an electromagnetic stirring method is used as the means for circulating the molten metal.
FIG. 3 shows the conventional electromagnetic stirring device disclosed in this publication. This stirring device includes a pair of electromagnetic stirring coils 6a and 6b provided along long sides 10a and 10b of the mold, respectively. This device is actuated to apply a uniform electromagnetic stirring thrust force to the molten metal contained in-the mold 3 through the effect of the stirring coils 6a and 6b so that the molten metal is circulated along the mold wall. That is, the electromagnetic stirring coil 6a includes plural magnetic cores 12a ranged along the long side 10a of the mold, and a coil 14a wound around a slot 13a formed thereon. The other stirring coil 6b has the same arrangement. The coil 14a is connected to a three-phase current power supply 8 through a wiring box 7a. Likewise, the coil 14b is connected to the three-phase current power supply 8 through a wiring box 7b. A representative wiring arrangement is illustrated in FIG. 3. In this wiring arrangement, a shifting field type electromagnetic stirring thrust force is applied to the molten metal on the meniscus as viewed by arrows of FIG. 2.
In the conventional electromagnetic stirring device shown in FIG. 3, the distribution of the thrust force on the meniscus is shown in FIG. 4 on the assumption that the three-phase current power supply 8 has a frequency of 2 Hz and a current of 400 A. The distribution shown in FIG. 4 is analyzed by universal software used for analyzing electromagnetic field numerical values. In this figure, the arrow direction indicates the direction of the thrust force of each cell and the arrow length indicates the magnitude of the thrust force. As will be understood from FIG. 4, the components of the thrust force along the long side 10 of the mold are kept substantially constant at each location of the long side.
As mentioned above, the in-mold electromagnetic stirring device provided in the conventional continuous casting apparatus for casting a metal slab operates to apply uniform electromagnetic stirring force to the molten metal along the long side of the mold. Hence, the circulating flow of the molten metal on the meniscus is made stronger when the molten metal flows from the short side 11 of the mold to the dipping nozzle 2 or made weaker when the molten metal flows from dipping nozzle 2 to the short side 11 of the mold.
On the other hand, on the meniscus, non-metallic inclusion or powder is floating. If the circulating flow of the mo
REFERENCES:
Fujisaki et al., Fundamental Electromagnetic Characteristics Of In-Mold Electromagnetic Stirring In Continuous Casting, Oct. 1994, pp. 272-277.
Fujisaki et al., Flow Control Of Molten Metal In Mold Using Linearmotors, May 1994, pp. 57-66.
Fujisaki Keisuke
Okazawa Kensuke
Okumura Yasushi
Sawada Kenzo
Toh Takehiko
Lin Kuang Y.
Nippon Steel Corporation
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