JPS61193755A - Electromagnetic stirring method - Google Patents

Abstract

PURPOSE:To provide an improvement in quality of an ingot, etc. by providing a static magnetic field generator to decrease the flow rate of molten steel flow and disposing an electromagnetic stirrer on the down stream thereof. CONSTITUTION:The static magnetic field generator 5 is disposed to the outside on the long side of a casting mold with the molten steel flow 2 in-between. The electromagnetic stirrer 6 is disposed on the down stream of the device 5 to stir the molten steel within the horizontal plane. The force to decrease the flow rate of the molten steel flow 2 is generated by the mutual effect of the static magnetic field generated by the generator 5 and the molten steel flow, by which the collision energy to a solidified shell 3 is decreased. The remelting and the delay in the development of the shell 3 and therefore prevented. The shifting magnetic field is further generated in parallel with the long side direction of the casting mold by the stirrer 6, by which the floating of non-metallic inclusions is accelerated. The quality of the ingot is improved and the stability of the operation is improved as well by the above-mentioned method.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a static magnetic field generating device C: which further reduces the flow velocity of a molten steel flow supplied from a submerged nozzle into a mold of a continuous casting facility, and a downstream C unit thereof. Installed mobile magnetic flux generator I: It relates to an electromagnetic stirring method for stirring molten steel and reducing non-metallic inclusions inside the slab to improve the quality of the slab and ensure stable operation.

[Technical background of the invention and its problems] In the recent steel manufacturing industry, continuous casting has become commonplace, and in recent years, continuous casting has become more common in the steel manufacturing industry. ing.

In continuous casting, molten steel is injected into the mold from a tamp push through an immersion nozzle, and the self-melting steel in the mold is cooled from its surroundings to form and develop a solidified shell, while casting continues. At this time, in the mold, as shown in Fig. 4, the molten steel 2 injected from the tundish (not shown) flows out from the discharge port of the immersion nozzle 1, and this molten steel flow 2 flows from the short side wall of the slab (-collision). Then, the flow is divided into a downward flow and an upward flow C.

04, whose downward flow becomes the main stream of the melt chamber flow and penetrates deeply into the slab, is a flux that is coated on the surface of the molten steel slab to prevent oxidation. Here, when the casting speed rises C, that is, when the number of molten steel caps injected per unit time increases, the discharge flow rate of the molten steel increases proportionally if the discharge hole diameter of the immersion nozzle is the same. The increase in the discharge flow rate of molten steel causes the following problems in terms of operation and slab quality.

1) The impact energy of the molten steel flow on the short side of the slab increases, causing a delay in the development of the solidified shell and remelting.
Non-uniform solidified shell thickness occurs, resulting in breakouts and cracking.

2) Furthermore, the delay in the development of the solidified shell near the corners causes the liquid phase to be confined and causes cross-sectional defects.

3) The penetration depth of the descending molten steel flow discharged from the immersion nozzle into the slab increases, and as a result, it becomes difficult for nonmetallic inclusions to float, and the amount of trapped nonmetallic inclusions increases significantly.

4) Also, in the case of a double bending machine, which has become particularly popular in recent years, non-metallic inclusions accumulate in the upper surface layer C of the Jt slab, causing quality deterioration.

In order to solve the above-mentioned problems, the conventional idea was to use a large-hole immersion nozzle as a means of not increasing the flow rate of molten steel discharged from the immersion nozzle even when the casting amount increased. However, due to the falling energy from the tundish, the flow velocity of the molten steel cannot be effectively reduced by 1 unit, and it also increases the cost of the refractory material for the immersion nozzle, which is not a good idea. Install an electromagnetic stirring device,
Solidified shell 1: Non-metallic inclusions are difficult to capture by stirring the molten steel in a horizontal plane, and a plan to float the non-metallic inclusions has been proposed, but the molten steel discharge flow rate in the case of a slab casting machine is 100a+ /sec i2, so it is not valid. When an attempt is made to raise the non-metallic inclusions by increasing the stirring force using an electromagnetic stirring device (-), the flow rate of molten steel increases in the horizontal plane due to the stirring force, and the flow of molten steel changes suddenly at the corners of the mold. A waving phenomenon occurs, and this waving phenomenon causes scratches on the surface of the slab and causes the flux floating on the surface of the molten steel to get caught up in the slab, resulting in a decrease in quality.

It also causes a delay in the development of the solidified shell, causing breakout.

On the other hand, a device that generates a static magnetic field in a direction perpendicular to the direction of the molten steel flow is installed, and the static magnetic field and the molten steel flow generate a C uprecking force that is opposite to the flow direction of the molten steel. A method has been proposed to solve the above problems by reducing the velocity of the molten steel flow.
Reduction of non-metallic inclusions or prevention of non-uniformity of σ solidified shell C
Although it has two effects, it is not effective in floating nonmetallic inclusions with small diameters (approximately 200 microns or less), and they are inevitably trapped in the solidified shell. In the case of machines, the problem remains that nonmetallic inclusions with small diameters accumulate on the upper surface layer of the slab.

[Object of the Invention] Therefore, in consideration of the above-mentioned drawbacks, the present invention aims to provide an electromagnetic stirring method capable of reducing nonmetallic inclusions, achieving high quality, and improving stable operation. do.

[Summary of the Invention] In order to achieve the above object, the present invention provides a continuous casting mold with an outer surface on the long side side that sandwiches the molten steel flow discharged from the immersion nozzle in a direction perpendicular to the direction of the molten steel flow. The general idea is to provide a device that generates a static magnetic field, and a device that generates a moving magnetic field parallel to the long side direction at least on one of the long sides downstream of the device.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1, the molten steel flow 2 discharged from the discharge hole of the immersion nozzle 1 collides with the shorter side of the mold and is divided, as described above, and the downward flow penetrates deeply into the slab. In order to reduce the flow velocity of this molten steel flow, in the present invention, as shown in FIG. Direction 1: Perpendicular direction C: A static magnetic field generating device 5 that generates a static magnetic field is provided, and by driving the static magnetic field generating device 5, the static magnetic field generated by the static magnetic field generating device [5+-] and A force is generated from the molten steel flow 21 in the direction opposite to the flow direction of the molten steel flow 2 to reduce the flow velocity of the molten steel flow 2 discharged from the discharge hole,
The impact energy on the solidified shell 3 is reduced, preventing remelting of the solidified shell 3 and delay in development, and promoting the improvement of non-metallic inclusions having a large diameter. At the same time C
:, Downstream of the static magnetic field generator 5 (- An electromagnetic stirring device 6 that generates a moving magnetic field parallel to the long side direction is provided, and the electromagnetic stirring device 6 is driven to stir the molten steel in a horizontal plane. However, the cleaning action of the stirred molten steel prevents nonmetallic inclusions with small diameters from being captured on the surface of the solidified shell 3, and promotes floating of the nonmetallic inclusions.

do.

Here, the static magnetic field generator 5 is as shown in FIG.
The electromagnetic stirring device 6 that needs to be provided on each of the long side surfaces C of the slab so as to sandwich the molten steel flow discharged from the immersion nozzle 1 is shown in FIG. As shown in FIG. 3, it is preferable to dispose a C-unit downstream of the static magnetic field generator e5, and a C-unit parallel to the long side of the C-shape as shown in FIG.

Further, the installation positions of the static magnetic field generator 5 and the electromagnetic stirring device 6 may be determined by considering the flow direction or flow velocity of the molten steel flow 2 discharged from the immersion nozzle 1.

"Effects of the Invention" As explained above, according to the present invention, the flow velocity of the molten steel flow discharged from the discharge hole of the immersion nozzle is reduced, the growth delay of the solidified shell is prevented or the remelting is prevented, and It is possible to prevent non-metallic inclusions from adhering to the surface of the solidified shell and promote flotation (-, it is possible to prevent breakouts, etc., and to improve operational stability or slab quality. can.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a mold part for carrying out the present invention, Fig. 2
This figure is a plan view of the same mold section, FIG. 3 is a diagram showing the flow direction of molten steel in FIG. 2, and FIG. 4 is a sectional view of the conventional mold section.

Claims (1)

[Claims] In continuous casting equipment that continuously casts molten steel from a tundish into a mold to obtain a steel ingot, a static magnetic field generating device that generates a static magnetic field is installed at a position surrounding the molten steel flow discharged from the discharge port of the immersion nozzle. A force is generated perpendicularly to the molten steel flow to reduce the flow velocity of the molten steel flow, and an electromagnetic stirring device is provided to surround the molten steel flow at a position downstream of the generation of the static magnetic field of the molten steel flow. An electromagnetic stirring method characterized by stirring the molten steel flow horizontally.