JPH0642982B2 - Metal flow control method in continuous casting mold - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to metal flow control in a continuous casting mold that controls / suppresses the flow of molten metal flowing out from a dipping nozzle in a continuous casting conductive static mold by electromagnetic force. Regarding the method.

[Prior Art] In continuous casting, there is a step of supplying molten steel from a dipping nozzle into a copper mold. In this step, the powder is floated for the purpose of keeping the molten steel warm and lubricating it. However, there is a problem that this powder is mixed as an impurity into the solidified slab that is entrained by the flow of molten steel. In particular, when the speed of casting is increased as in recent years, the molten steel flow becomes violent, the molten metal surface wave becomes large, and the mixture of powder may become remarkable.

For this reason, it has been conventionally attempted to dampen the molten steel flow in the mold by utilizing the electromagnetic force of the external magnetic field. There are a static magnetic field method and a moving magnetic field method.

For example, Japanese Patent Application Laid-Open No. Sho 59-59 has been known as a device utilizing a static magnetic field.
No. 101261 and Japanese Utility Model Laid-Open No. 59-85653, a static magnetic field is applied from the outside of the mold by an electromagnet or a permanent magnet that horizontally penetrates the side surface of the mold and orthogonally crosses the molten steel flow. Are known. That is, as shown in FIGS. 4 (a), (b), and (c), the magnetic pole surface is provided near the outlet of the immersion nozzle 2 outside the long side walls 1 a, 1 a of the mold 1 having a rectangular cross section. Towards the pair of electromagnets 3,
4 are arranged so as to face each other with their opposite polar surfaces facing each other. In addition,
The powder 5 is suspended in the molten steel in the mold 1.

In this case, the molten steel flowing out from the immersion nozzle 2 flows as shown by the arrow a in the figure, while the electromagnets 3,
4, a static magnetic field is generated in the direction indicated by arrow C in the figure, and an induced current is generated in the direction indicated by arrow B in the figure. As a result, a force in the direction opposite to the molten steel flow is generated to dampen the molten steel flow, suppress the increase in molten metal surface wave, and prevent the powder 5 from being caught up as much as possible.

Further, as a device utilizing a moving magnetic field, there is a conventional method disclosed in Japanese Patent Laid-Open No. 57-57.
As seen in No. 11756, an electromagnetic coil is installed along the long side wall of the mold, and a moving magnetic field is excited in the molten steel in the mold in the same manner as the principle of so-called electromagnetic stirring.
It is known that the moving direction of the moving magnetic field is set to be opposite to the flowing direction of the molten steel to brake the molten steel flow.

Another example of utilizing a moving magnetic field is JP-A-60-2.
As disclosed in Japanese Patent No. 34754, it is known that a plurality of electromagnetic coils are arranged above the molten metal level in a mold and a moving magnetic field is excited in the molten steel to brake the molten steel flow.

[Problems to be Solved by the Invention] However, in the above-described conventional method using a static magnetic field, the static magnetic field is generated in a direction that horizontally penetrates the side wall of the mold. The current is a current that closes in the molten steel, so that it is greatly affected by the relatively large electric resistance of the molten steel, and the induced current is not efficiently generated. The electric resistance of the molten steel is about 150 × 10 ⁻⁸ Ωm, which is about two orders of magnitude higher than the electric resistance of the copper mold of 2.5 × 10 ⁻⁸ Ωm.

Therefore, a sufficient braking force against the molten steel flow cannot be obtained, and there is a problem that the powder 5 cannot be sufficiently prevented from being mixed into the molten steel.

In addition, the method using the moving magnetic field has a drawback that the apparatus is complicated and large in size, such as an AC power supply device and a connection of a plurality of coils, for generating the moving magnetic field. Also, the former method of this method has a problem that an eddy current is generated in the mold and weakens the magnetic field in the molten steel, so that a structure that generates a large magnetic field must be generated and the apparatus becomes larger. Although it is effective for damping molten steel flow near the molten metal surface, it is difficult to dampen the inside of the mold, and a cooling mechanism is required to protect the electromagnetic coil against secondary heat from the molten metal surface. There was a problem.

As described above, the one using the moving magnetic field has many problems to be solved in practical use, such as the device being complicated and large in size, as compared with the one using the static magnetic field. Therefore, the present invention is based on the use of a static magnetic field, and further aims to provide a metal flow control method in a continuous casting mold capable of efficiently inducing an induced current to obtain a large braking force and maximally preventing mixing of powder. To do.

[Means and Actions for Solving Problems] The present invention relates to the long side direction of a mold when controlling the flow of molten steel metal flowing out of an immersion nozzle into a conductive mold of continuous casting by electromagnetic force. The static magnetic field is applied in a direction parallel to the plane formed by the drawing direction and perpendicular to the molten metal flow direction, whereby the flow of the molten metal is damped.

That is, as shown in FIG. 1, a molten metal is poured from a dipping nozzle 12 into a mold 11 made of, for example, copper and having a rectangular cross section.
For example, by supplying molten steel, molten steel flow indicated by the arrow A is generated in the mold 11. On the other hand, for example, a pair of electromagnets 13, 14, 15 and 16 are arranged outside the long side walls 11a and 11a of the mold 11 so as to face each other, and the slab is pulled out from the outside of the side walls 11a and 11a toward the inside. A static magnetic field (indicated by an arrow C in the figure) is generated in a direction (indicated by an outline arrow in the figure).

As a result, the induced current shown by the arrow B in the figure flows through the long side walls 11a, 11a of the mold 11 and through the molten steel. That is, a closed circuit passing through the side wall of the mold 11 is formed. And since the electric resistivity of the copper constituting the mold 11 is 2 orders of magnitude smaller than that of 2.5 × 10 ^-8 Ωm and the molten steel in electrical resistivity 150 × 10 ^-8 Ωm electrical resistance of the closed circuit is conventional static The magnetic field can be made considerably smaller than that generated in a direction that penetrates the mold side wall horizontally and induces an induction current that closes in molten steel. Therefore, the induced current is efficiently induced and a large braking force is generated. Therefore, fluctuations in the molten metal surface are reliably prevented, and the powder 17 can be prevented from being mixed into the molten steel to the maximum extent.

Further, the cause of the fluctuation of the molten metal surface in the vicinity of the short side wall of the mold 11 is due to the upward flow inside the molten steel (indicated by the arrow A in the figure). From this, as shown in FIG.
In the figure, for example, an electromagnet 18 is arranged outside the short side wall 11b to generate a static magnetic field (indicated by arrow C in the figure) in the drawing direction of the slab from the outside to the inside of the side wall. As shown by the arrow B, it is possible to generate an induced current passing through the short side wall of the mold 11. Therefore, even in this case, the induced current can be efficiently generated, a large braking force can be obtained, and the mixture of the powder 17 into the molten steel can be prevented as much as possible.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. In addition, this Example describes what applied this invention to casting of a slab continuous casting machine.

As shown in FIG. 3, molten steel is supplied from a dipping nozzle 22 into a copper mold 21 having a rectangular cross section, and a pair of electromagnets 23 are provided outside the long side walls 21a and 21a of the mold 21, respectively. , 24, 25, 26 are arranged to face each other,
A static magnetic field is generated from the outside of the side walls 21a, 21a toward the inside in the drawing direction of the slab (the direction indicated by the white arrow in the drawing).

Further, the electromagnets 28 and 29 are arranged to face each other outside the short side walls 21b and 21b of the mold 21, respectively.
A static magnetic field is generated in the pull-out direction of the slab from the outside to the inside of 21b. In the figure, 27 is a powder suspended in molten steel.

The short side wall 21b of the mold 21 has a movable structure and is separated from the long side wall 21a. Therefore, electrolytic corrosion due to an induced current may occur at the contact surface between the short side wall 21b and the long side wall 21a. In order to prevent this, the short side wall 21b and the long side wall 21a are electrically connected by an electric wire 30 to secure an induced current path.

With such a structure, for example, the thickness is 235 mm and the width is 1800 mm.
A slab having a cross section of 5 is cast at a casting speed of 0.95 m / min, and the magnetic field generated by the electromagnets 23 to 26 is 2 at maximum.
When the magnetic field generated by the electromagnets 28 and 29 is set to 500 gauss and the maximum is set to 1800 gauss, and either one of the electromagnets 23 to 26 or the electromagnets 28 and 29 is operated, large braking is applied and fluctuations in the molten metal surface are suppressed, It was possible to reduce the amount of the powder 27 to be mixed with the conventional powder by half as compared with the conventional amount.

Further, when the electromagnets 23 to 26 and the electromagnets 28 and 29 were operated at the same time, even greater braking was applied, the fluctuation of the molten metal level was further suppressed, and the amount of the powder 27 mixed in the molten steel could be further reduced.

Further, in an actual facility, it is possible to arrange only a pair of electromagnetic coils so that a magnetic field is applied to the immersion nozzle portion in order to facilitate the facility. The action in this case is the first
It can be understood that 13 and 14, and 15 and 16 in FIG.

[Effects of the Invention] As described in detail above, according to the present invention, an induced current can be efficiently induced by generating a static magnetic field from the outside of the mold in the drawing direction of the slab, which results in a large braking force against the molten metal flow. It is possible to provide a method for controlling the metal flow in a continuous casting mold, which can prevent the mixture of powder to the maximum extent.

[Brief description of drawings]

1 and 2 are diagrams for explaining the basic principle of the present invention, FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention, and FIG. 4 is a schematic configuration diagram showing a conventional example. 11, 21 ... Mold, 12, 22 ... Immersion nozzle, 13
~ 16,18,23 ~ 26,28,29 ... Electromagnet, 1
7,27 ... Powder.

Claims (4)

[Claims] 1. A method for controlling / suppressing the flow of molten metal flowing out of a dipping nozzle into a continuous casting conductive mold by an electromagnetic force, wherein the melting is performed in parallel with a plane formed by the long side direction and the drawing direction of the mold. A method for controlling metal flow in a continuous casting mold, which comprises applying a static magnetic field in a direction perpendicular to the metal flow direction. 2. A method for applying a static magnetic field is a method in which at least one pair of U-shaped electromagnetic coils are provided in the vicinity of an immersion nozzle, and at least one pair is installed so that the mold is sandwiched and the same kind of magnetic poles face each other. The method for controlling metal flow in a continuous casting mold according to claim 1. 3. The method of applying a static magnetic field is a method of arranging an electromagnetic coil outside a short side of a mold.
Item 6. A method for controlling metal flow in a continuous casting mold according to item. 4. A method for applying a static magnetic field is such that at least a pair of U-shaped electromagnetic coils are provided in the vicinity of an immersion nozzle so that the mold is sandwiched and the same kind of magnetic poles face each other, and The method for controlling metal flow in a continuous casting mold according to claim 1, which is a method of disposing an electromagnetic coil outside the short side of the mold.