JPH0657343A - Device for blowing gas to molten metal - Google Patents

Abstract

PURPOSE:To provide the device for accelerating the chemical reaction on the surfaces of bubbles of the gas to be blown into a molten metal for the purpose of refining of the molten metal, etc., by forming the finer bubbles with the device which is small in size and consumes less electric power. CONSTITUTION:This device has a gas blow-off port 7 provided at the proper point of a heat resistant container 1 for storing or passing the molten metal 3 and an induction coil 5 wound around this container 1. The bubbles of the gas blown out of the blow-off port 7 are made fine by the vibrating Lorentz force generated in the molten metal 3 by supplying the DC current superposed on AC to the induction coil 5. Electromagnetic force is concd. near the blown gas in the relatively small container in such a manner and, therefore, the efficient formation of the finer bubbles is possible. Particularly, the efficiency of generating the vibrating force is enhanced by superposing the DC current on the AC current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for atomizing gas bubbles blown into a molten metal.

[0002]

2. Description of the Related Art Conventionally, an inert gas such as Ar or N ₂ is blown into a molten metal stored in a refining vessel from a porous plug or a nozzle provided on the wall surface of the vessel to remove impurities in the molten metal. It is being removed.
This utilizes a chemical reaction on the surface of the bubble, such as decarburization on the surface of the bubble by utilizing an oxidation reaction by dissolved oxygen. In order to improve the reaction efficiency, it is injected. It is desirable to increase the total area of the interface between the gas and the molten metal relative to the volume of gas. This is achieved by making the gas bubbles finer, and for that reason, the electromagnetic force accelerates the detachment of the bubbles from the nozzle end or the porous plug, or the bubbles are divided and diffused into fine bubbles by the electromagnetic force. It is suggested to do so.

As one of the methods for generating such an electromagnetic force, there are JP-A-4-36414 and JP-A-4-3.
As proposed in Japanese Laid-Open Patent Application No. 6415 and Japanese Unexamined Patent Publication No. 4-48027, a blowing gas is generated by applying an electromagnetic force from the outer circumference of the container toward the molten metal and utilizing the flow generated thereby. There are some that are miniaturized to increase the reaction interfacial area between the gas and the metal and accelerate the reaction. However, according to this method, since the electromagnetic force is applied to the entire container, there is a problem that the electromagnetic force application device becomes huge in order to cause the entire flow.

As a second method of generating an electromagnetic force, as proposed in Japanese Patent Publication No. 30456/1993, there is a method of making bubbles of blown gas fine by simultaneous application of a magnetic field and an electric current. In the case of this method, since it is necessary to apply the DC magnetic field and the AC current at the same time, firstly, for the convenience of applying the DC magnetic field, it is necessary to reduce the magnetic pole interval, and the melting in the direction of applying the magnetic field is required. There is a problem that the thickness of the metal container must be reduced, and secondly, a conductive refractory must be used as an electrode for applying an electric current, which causes problems of durability and stability of the electrode.

[0005]

In view of the above problems of the prior art, the main object of the present invention is to prevent gas bubbles blown into the molten metal for the purpose of refining the molten metal.
An object of the present invention is to provide a device for promoting a chemical reaction on the surface of bubbles by miniaturizing the device with a small size and low power consumption.

[0006]

According to the present invention, the above-mentioned object is to provide a gas outlet provided at an appropriate position of a heat-resistant container for storing or circulating molten metal, and an induction coil for winding the container. And a cross-flow power supply device for supplying a direct current superimposed on an alternating current to the induction coil, thereby providing a device for blowing gas into a molten metal.

[0007]

By doing so, the gas bubbles blown out from the blow-out port can be made fine by vibrating Lorentz force generated in the molten metal by the current flowing through the induction coil. Further, since the electromagnetic force can be concentrated in the vicinity of the blown gas in a relatively small container, the efficiency of atomizing bubbles can be improved. In particular, by applying a DC electromagnetic field superimposed on an AC magnetic field to the molten metal, a stronger electromagnetic force can be generated as compared with the case where only the AC magnetic field is applied.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

A cylindrical bottom chamber 4 is recessed at the bottom of a refining container 1 formed of refractory bricks 2 as a container for storing molten metal 3, and a refining container containing the bottom chamber 4 is further provided. The outer periphery of 1 is covered with a steel skin 8. An induction coil 5 is wound around the outer periphery of the bottom chamber 4, and the induction coil is connected to an AC power supply 6a and a DC power supply 6b. A porous plug 7 is provided at the bottom of the bottom chamber 4 so that an inert gas such as Ar or N ₂ can be blown toward the molten metal 3 in the bottom chamber 4.

The gas blown from the porous plug 7 leaves the porous plug 7 and forms a bubble 9 rising upward as shown by an arrow 10, which is caused by alternating and direct currents flowing through the induction coil 5. The electromagnetic force generates a horizontal vibrational force as indicated by an arrow 11. This oscillating force has a function of shortening the period of bubble separation from the porous plug 7 and dispersing the once separated bubbles.

FIG. 2 shows a second embodiment of the present invention. Parts corresponding to those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. In the case of the present embodiment, the porous plug 7 is arranged not on the bottom of the bottom chamber 4 but on the outer periphery of the bottom chamber 4.

The installation location of the bottom chamber 4 is not limited to the above embodiment, and instead of the bottom surface of the refining vessel, a side wall adjacent to the bottom surface of the refining vessel can be laterally recessed.

FIG. 3 shows a third embodiment of the present invention. In the case of this embodiment, the apparatus for injecting the gas into the molten metal is not the bottom chamber but is, for example, the tap hole or ladle of the converter. It is provided in the pipe line through which the molten metal flows, such as the nozzle from the tundish to the tundish.

The device for injecting gas into the molten metal, which is constructed as a secondary refining device, has an outer peripheral wall 22 made of refractory bricks defining a flow path, and an iron skin 27 covering the outer peripheral wall 22.
Porous plug 2 for blowing out inert gas into the channel
6 are provided at a plurality of positions on the outer peripheral wall 22. Further, an induction coil 23 winding the outer peripheral wall 22 is provided, and a current obtained by superimposing a DC current from the DC power supply 25 on an AC current from the AC power supply 24 is supplied to the induction coil 23. It

Also in this case, when a current is applied to the coil 23, a Lorentz force acts on the molten metal flowing in the direction indicated by the arrow 29 in the radial direction, as indicated by the arrow 30. When only the alternating current is applied to the coil 23, the Lorentz force acts on the portion where the bubble 28 is generated or the bubble 28 itself, so that the bubble is removed at a frequency twice that of the alternating current. When the direct current is superimposed and applied, the desorption is performed at the frequency of the alternating current, and the temporal variation of the Lorentz force becomes substantially positive and negative, so that the efficiency is further enhanced. Here, by appropriately selecting the frequency and current value of the alternating current, the desired bubble dispersion refining action can be obtained, so the decarburization reaction by the dissolved oxygen in the molten steel is promoted, and efficient secondary refining is possible. Becomes

Instead of the porous plug used in the above embodiment, a nozzle may be used to blow the inert gas into the bottom chamber. Also, the number of porous plugs or nozzles can be arbitrarily determined as needed. Further, the alternating current is not limited to a sine wave, and if the facility allows, a rectangular wave or the like can be used to further improve the bubble dispersion refining action.

[0017]

As described above, according to the present invention, by supplying the induction coil with the current in which the alternating current and the direct current are superposed, the alternating magnetic field due to the alternating current power of the coil and the coil Compared with the case where only a DC current is applied to the coil by superimposing a DC magnetic field due to a DC current, a term of DC magnetic field × AC magnetic field is newly added, and the vibrating force can be effectively applied to the molten metal. . Further, by refining the bubbles of the gas to be blown, the area of the interface between the molten metal and the gas is increased and the reaction rate is increased, so that the processing time in the refining process etc. is shortened and the productivity is improved. An improvement can be achieved. In addition to this, by micronizing the bubbles, the action of floating and separating impurities can be improved.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view showing a first embodiment of an air bubble refining device according to the present invention.

FIG. 2 is a view similar to FIG. 1 showing a second embodiment of the present invention.

FIG. 3 is a view similar to FIG. 1 showing a third embodiment of the present invention.

[Explanation of symbols]

 1 Molten Metal 2 Refractory Brick 3 Molten Metal 4 Bottom Chamber 5 Induction Coil 6a AC Power Supply 6b DC Power Supply 7 Porous Plug 8 Iron Skin 22 Outer Wall 23 Induction Coil 24 AC Power Supply 26 Porous Plug 27 Iron Skin 29, 30 Arrows

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Ueyama 20-1 Shintomi, Futtsu City Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Keisuke Fujisaki 20-1 Shintomi, Futtsu City Nippon Steel Co., Ltd. Corporate Technology Development Division (72) Inventor Kiyoshi Kijima 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technical Development Division

Claims (1)

[Claims] 1. A gas outlet provided in a suitable position of a heat-resistant container for storing or circulating molten metal, an induction coil for winding the container, and a direct current superimposed on an alternating current in the induction coil. A cross-flow power supply device for supplying the gas, and a device for injecting gas into the molten metal.