JPH06170497A - Apparatus for continuously casting molten metal - Google Patents

Abstract

PURPOSE:To stably produce a cast slab having good surface characteristic by solidifying molten metal poured into a continuous casting mold while lightly floating up the molten metal by electromagnetic pinch force. CONSTITUTION:A cross current surrounding the continuous casting mold 3 is directly supplied to the mold and the molten metal 16 poured together with lubricant 11 is solidified while lightly floated up by the electromagnetic pinch force. Further, at the time of conducting the current to the mold 3, through the insulation between the molten metal 16 and the mold including a coil 13 is needed, since the electric conductivity of the mold lubricant 11 ordinarily used is low, by the method impressing the current at the time when the flowing of the lubricant becomes a stationary condition, the short circuit of the impressed current can be avoided. By this method, the cast slab having good surface characteristic can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for continuously casting molten metal.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 52-32824 discloses a continuous casting method in which a molten metal 16 is poured together with a lubricant 11 into a water-cooled mold 3 which is vibrated at a constant cycle, and continuously drawn downward. Induction coil 1 provided around the mold
A method has been proposed for improving lubrication between the mold and the slab by raising the molten metal into the convex shape 18 by utilizing the pinch force due to the AC electromagnetic field generated by No. 3 (FIG. 1). According to this method, it is possible to drastically improve defects such as oscillation marks and cracks caused by the vibration mold and the lubricant, which are found in continuous casting of steel, which occur on the surface of the slab.

[0003]

According to the above method,
It is possible to manufacture a slab with good surface properties, but since the induction coil is installed on the outer periphery of the mold, eddy current loss due to the mold itself occurs and the frequency of the alternating current is lowered to reduce this. There was a need. However, in this case, the electromagnetic force raised the meniscus in a convex shape and at the same time generated an electromagnetic stirring flow in the molten metal, which made the meniscus unstable and varied the suppression of generation of the defects in the circumferential direction of the cast piece. Further, there is a method of increasing the frequency of an alternating electromagnetic field as a method of obtaining such a convex bulge of a meniscus by suppressing such an electromagnetic stirring flow to a low level, but the eddy current loss in the mold increases and a sufficient electromagnetic force is applied to the molten metal. To give to
It is necessary to use a cold crucible method in which a mold is provided with slits penetrating in the vertical direction, or to configure the mold with ceramics of low electric conductivity. However, even in such a case, there is a problem that the life of the mold is short such as melting or mechanical damage of the refractory or cold crucible type such as pouring into the slit and deformation due to repeated fatigue.

[0004]

DISCLOSURE OF THE INVENTION The present invention has solved the above-mentioned problems, and its gist is to maintain a constant vertical direction for injecting a molten metal together with a lubricant that also serves as an insulating agent to solidify the molten metal. It is a continuous casting apparatus for molten metal, which has a water-cooled mold that vibrates in a cycle of, and an alternating current circulating around the mold is directly supplied to the mold.

In particular, the mold is composed of four plates, and an alternating current is directly applied to the two plates which form the long sides of the molds facing each other, and another set of the short sides of the mold which forms the opposite sides of the mold is formed. The plate is 2
It is preferable that the width of the slab can be changed by being insulated from the plate forming the long side of the mold to be movable in the width direction of the slab.

Further, it is preferable that the mold is divided into two or more parts in the casting direction and they are insulated from each other so that the alternating current supplied to the mold is supplied only near the molten metal meniscus. The present invention has a structure intended to form a stable and stable molten metal meniscus swell by directly supplying an electric current to the mold.

A specific configuration of the device of the present invention will be shown below with reference to FIG. 2 together with its embodiment. The molten metal stored in the tundish is injected into the water-cooled mold 3 through the injection nozzle 2. An alternating current 4 is directly supplied to the mold 3. The alternating current 4 flowing through this mold raises the molten metal surface 5 in the mold in a convex shape.

The applied AC current is preferably 0.05 Tesla or more and 0.20 Tesla or less at the upper end position of the coil at the center of the mold. The frequency is preferably 50 Hz or more and 200 kHz or less. Further, in the case of a device capable of changing the width with a rectangular mold, as shown in FIG.
The mold plates 6 facing each other to form the long sides of the mold are connected so as to form one coil, and the other set of mold plates 7 facing to the short side of the mold are provided with an appropriate supporting structure. It is composed of a conductive block, and is insulated from the mold plate forming the long side of the mold and can move between them to change the width of the pool of molten metal.

Further, since the action of electromagnetic force is required only near the meniscus, it is also possible to configure the mold with two or more plates insulated from each other in the casting direction in order to concentrate the current (FIG. 4). .

[0010]

The molten metal injected into the mold is held in a predetermined shape by the induction electromagnetic field and buoyancy (gravity). At this time, a balance between electromagnetic pressure and gravity is generated on the surface of the molten metal as shown in FIG. 5, and the electromagnetic pinch force causes the molten metal to float and solidify. In addition, it is necessary to insulate between the molten metal and the mold that is a coil when passing an electric current through the mold, but the lubricant inflow became a steady state because the electric conductivity of the mold lubricant that is normally used is low. It is possible to avoid the short circuit of the applied current by the method of applying the current at the time point.

Next, the width changing action in the case of a rectangular mold will be described. FIG. 6 shows the current distribution at a certain moment in a cross section orthogonal to the mold. At this time, an induced current 14 that is approximately in the opposite direction to the current 4 around the conductor flows through the conductor. Therefore,
If a pair of opposing conductive blocks are arranged as shown in the figure while keeping the insulating state, the surroundings of the molten metal having a rectangular cross section will have a current due to the forced current 4 and the induced current 14 surrounding it. A ring is generated, and the electromagnetic force 10 as shown
To the molten metal 16. By moving this conductive block, the width can be changed in the same mold.

[0012]

As described above, by using the apparatus of the present invention, it is possible to stably produce a slab having a good surface quality, which cannot be obtained by the conventional casting of the mold structure.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional continuous casting method using an alternating electromagnetic field.

FIG. 2 is a diagram showing a specific configuration of the device of the present invention.

FIG. 3 is a diagram showing a specific configuration of the apparatus of the present invention in the case of a rectangular mold.

FIG. 4 is a diagram showing a specific configuration in the case of a split mold of the apparatus of the present invention.

FIG. 5 is a diagram showing the balance of meniscus forces.

FIG. 6 is a view showing a current distribution of a rectangular cross-section mold and an electromagnetic force applied to a molten metal.

[Explanation of symbols]

 1 Tundish 2 Injection Nozzle 3 Mold 4 AC Current (Forced Current) 5 Molten Metal Surface 6 Energized Mold Plate 7 Movable Mold Plate 8 Cooling Water 9 Water Box 10 Electromagnetic Force 11 Lubricant 12 Induction Magnetic Field 13 Coil 14 Induction Current 15 Electromagnetic Force Induction Flow 16 Molten metal 17 Oscillation 18 Raised surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keisuke Fujisaki Inventor Keisuke Fujisaki 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Koji Ueyama 20-1 Shintomi, Futtsu-shi, Chiba Shin-Nihon Steel Engineering Co., Ltd.

Claims (3)

[Claims] 1. A water-cooled mold for vertically pouring a molten metal together with a lubricant to solidify the liquid metal, and an alternating current circulating around the mold is directly supplied to the mold. A continuous casting apparatus for molten metal, characterized in that 2. A mold is composed of four plates, and an alternating current is directly applied to the two plates that form the long sides of the two plates facing each other, and another pair of the two plates that form the short sides of the two plates facing each other are formed. 2. The continuous casting apparatus for molten metal according to claim 1, wherein the two plates are insulated from the plates forming the long sides of the two molds and are movable in the width direction of the slab. 3. The mold is divided into two or more parts in the casting direction and they are insulated from each other, and the alternating current supplied to the mold is supplied only near the molten metal meniscus. The continuous casting device for molten metal according to claim 1 or 2.