JP2603406B2 - Molten metal refining equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for refining molten metal, and more particularly, to improving the reaction efficiency by reducing the size of gas bubbles blown into the molten metal by using electromagnetic force. To a refined molten metal refining apparatus.

[0002]

Conventionally, the貯容molten in metal refining vessel, blowing Ar, an inert gas such as N ₂ of porous plug or nozzle mounted on the wall of the container, remove impurity components of the molten metal That is being done. This utilizes a chemical reaction on the surface of the bubble, such as decarburization using an oxidation reaction due to dissolved oxygen on the surface of the bubble. It is desired to increase the total area of the interface between the gas and the molten metal relative to the volume of the gas to be produced. This is achieved by reducing the size of the gas bubbles. As a method for this purpose, electromagnetic force is used to accelerate the separation of bubbles from the nozzle end or the porous plug, and the bubbles are divided and diffused into minute bubbles by electromagnetic force. It has been proposed to.

One of the methods for generating such an electromagnetic force is disclosed in JP-A-4-36415 and JP-A-4-3.
As proposed in Japanese Patent No. 6414 and JP-A-4-48027, an electromagnetic force is applied to the molten metal from the outer periphery of the container, and the blowing gas is generated by utilizing the flow generated thereby. Some of them are miniaturized to increase a reaction interface area between a gas and a metal to promote a reaction. However, according to this method, since an electromagnetic force is applied to the entire container, there is a problem that an electromagnetic force applying device becomes large in order to cause an overall flow.

As a second method for generating an electromagnetic force, as disclosed in Japanese Patent Publication No. Hei 3-30456, there is a method for miniaturizing bubbles of a blown gas by simultaneously applying a magnetic field and a current. In the case of this method, it is necessary to apply a DC magnetic field and a DC current at the same time.
There is a problem that the thickness of the molten metal container in the direction in which the magnetic field is applied must be reduced because the interval between the magnetic poles must be reduced due to the application of the DC magnetic field.
In addition, since a conductive refractory must be used as an electrode for applying a current, durability and stability of the electrode become a problem.

[0005] Therefore, by providing a gas blowing nozzle at an appropriate position in a refining vessel having a relatively small diameter constituted as a bottom chamber or a tube, and supplying an alternating current to an induction coil wound around the refining vessel, a small-sized refining vessel is provided. It has been proposed to miniaturize gas bubbles with a device that consumes less power to promote a chemical reaction at the surface of the bubbles. In such a case, it is desirable to maximize the generated magnetic field for a given current consumption or equipment cost. That is, increasing the input power not only increases the size of the power supply device and the refining device, but also increases the calorific value of the coil current, and further increases the size of the device when water cooling is required. In addition, since the electromagnetic force applied to the coil also increases, structural reinforcement is required, and in addition, electromagnetic interference with surroundings becomes a problem.

[0006]

SUMMARY OF THE INVENTION In view of the problems of the prior art and the knowledge of the inventor, the main object of the present invention is to provide a gas bubble blown into a molten metal for the purpose of refining the molten metal. It is an object of the present invention to reduce the size of a device for promoting a chemical reaction on the surface of a bubble by miniaturizing the size of the bubble and to save power consumption.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a refining vessel for storing a molten metal, wherein a bottom chamber is provided at the bottom of the refining vessel, and a gas outlet provided at an appropriate position in the bottom chamber. And, in a molten metal refining apparatus having a coil wound around the bottom chamber and a power supply for supplying current or voltage to the coil, the bottom chamber and the coil are covered with a magnetic shielding material made of a ferromagnetic material, A first method in which a current or a voltage whose magnitude changes with time is applied to a coil, or a tube through which a molten metal provided with a gas outlet at an appropriate position flows, and the tube is wound around the tube. In a molten metal refining apparatus having a coil and a power supply for supplying a current or voltage to the coil, the tube and the coil are covered with a magnetic shielding material made of a ferromagnetic material, and the size is periodically changed. Changing current Others are achieved by a second method which is adapted to apply a voltage to the coil. Further, the first and second methods further enhance the effect by superimposing a positive current or a positive voltage on the current or the voltage applied to the coil, the magnitude of which changes with time, respectively. be able to.

[0008]

As described above, if the refining container and the coil are covered with the magnetic shielding material made of a ferromagnetic material, the magnetic field generated by the coil is confined by the magnetic shielding material and concentrated in the container. Enhanced. Therefore, it is possible to reduce the size of the device and reduce the power consumption.

When a positive current or a voltage is added to a current or a voltage whose magnitude changes with time, for example, when a DC current is superimposed on a certain AC current, the current becomes positive due to the DC current. Either the cycle that takes the value of or the cycle that takes a negative value becomes longer, and the absolute value of the peak value becomes larger.

On the other hand, the current induced in the conductor (the molten metal in this case) is determined by the time variation of the magnetic flux density due to the alternating current at the place where the induced current flows and the amplitude of the alternating current. Since the force is determined by the product of the induced current and the magnetic flux density, in the conductor, the magnetic flux density, which takes one of the signs longer, and the induced current, which oscillates in the same cycle as the alternating current, both positive and negative, except for the phase difference, , A Lorentz force is generated. Here, if a DC current larger than the amplitude of the AC current is applied, the magnetic flux density does not take a value of zero. Therefore, by superimposing a DC current on an AC current, a larger Lorentz force can be generated by a magnetic flux density having a larger amplitude as compared to a case where an AC current is simply applied. In addition, in an inductive device in which the power of the DC component is relatively much smaller than the power of the AC component, the power for applying the DC current may be smaller than the power for applying the AC current.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a preferred embodiment of the present invention.

As shown in FIG. 1, a refining vessel 1 formed by a refractory brick 2 as a vessel for storing a molten metal 3 therein.
A bottom chamber 4 having a cylindrical shape is recessed at the bottom portion. 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. The outer periphery of the refining vessel 1 including the bottom chamber 4 is covered with an induction coil 5 and an iron shell 8 made of a ferromagnetic material. A porous plug 7 is provided at the bottom of the bottom chamber 4, and Ar, N
An inert gas such as ₂ can be blown out toward the molten metal 3 in the bottom chamber 4.

The gas blown out of the porous plug 7 leaves the porous plug 7 and becomes bubbles 9 rising upward as shown by an arrow 10. The electromagnetic force generated by the alternating current flowing through the induction coil 5 Generates a horizontal oscillating force as indicated by arrow 11. The vibratory force moves the molten metal violently, and serves to shorten the cycle of detachment of bubbles from the porous plug 7 and promote the miniaturization and dispersion of the bubbles once detached.

The electromagnetic force in this embodiment can be obtained by first calculating a magnetic field and an induced current generated by a given current. The equation of the electromagnetic field in this embodiment is as follows.

[0015]

(Equation 1)

Here, all the characters with arrows are vectors having x, y and z components. The physical quantities used are all functions of the coordinates x, y, z and time t.
When the time change has a quasi-stationarity such as an alternating current, the time derivative can be replaced with a complex number, and among the induced magnetic fields, the eddy current density and the electric field are expressed as follows.

[0017]

(Equation 2)

From the magnetic field and the induced current obtained as described above, the time average value of the electromagnetic force, that is, the Lorentz force is obtained by the following equation.

[0019]

(Equation 3)

Although the influence of the flow of the molten metal on the Lorentz force was assumed to be negligible, this assumption holds for all the following embodiments.

As shown in FIG. 1, dimensions of each part (unit: mm)
The maximum current density was 1.0 × 10
An alternating current of ⁶ (AT / m ² ) is applied to the coil 5, and its physical properties are as follows: conductivity σ = 1.0 × 10 ⁶ (S / m), magnetic permeability μ = μ ₀ (vacuum magnetic permeability) = 1.26 × 10 ⁶ (H / m)
Is stored as a molten metal, and as a steel shell, its physical property value is σ = 5.0 × 10 ⁶ (S / m),
μ = 10μ ₀ , 100μ ₀ , 300μ ₀ , 1000μ ₀ (H
/ M) were used.

FIG. 2 shows the maximum value (absolute value) of the time average of the Lorentz force generated when the induction coil 5 is covered with a ferromagnetic material and when the induction coil 5 is not covered with a ferromagnetic material. 50, 100, 300, 500, 1000
It is a graph of the result obtained numerically using the above-mentioned series of equations at (Hz). From FIG. 2, it can be seen that the electromagnetic force generated by shielding with a ferromagnetic material is larger. Also, the required power was comparable or even lower than in the case of no shielding. Therefore, it is understood that, in this embodiment, when the molten metal container and the electromagnetic induction device are shielded by a ferromagnetic material, it is possible to increase the induction electromagnetic force and reduce the power consumption.

As described above, according to the present invention, since the power supply capacity can be suppressed, the device can be downsized, the power consumption can be reduced, and the electromagnetic field is shielded.
Induction heating and electromagnetic interference of external devices can be prevented.

In this embodiment, the iron cover 8 covering the refractory brick 2 defining the flow path is made of a ferromagnetic material, and the induction coil 5 is also surrounded by this. Further, the induction coil 5 is directly surrounded around the refractory brick 2 without any ferromagnetic material interposed between the induction coil 5 and the refractory brick 2 defining the flow path. However, if necessary, a steel shell made of a non-magnetic material such as stainless steel may be provided between the refractory brick 2 and the induction coil 5. Further, the induction coil 5 and the magnetic shielding material can be divided as a device that can be attached to and detached from the integrated bottom chamber, and the induction coil 5 can be water-cooled if necessary. Further, a similar effect can be obtained by connecting a DC voltage power supply in parallel to the AC power supply 6a instead of the DC power supply 6b.

FIG. 3 shows a second embodiment of the present invention. In the present embodiment, an AC power supply 6a and a DC power supply 6b are connected in series to the induction coil 5 in the first embodiment shown in FIG. Since there is no change, the description is omitted.

Also in this embodiment, Ar, N ₂ blown out from the porous plug 7 toward the molten metal 3 in the bottom chamber 4.
Microbubbles and dispersion of inert gas bubbles are promoted by the oscillating force of the electromagnetic force generated by the AC and DC currents flowing through the induction coil 5, as in the first embodiment.

Here, when the DC current from the DC power supply 6b is superimposed on the AC current from the AC power supply 6a, either the period in which the current takes a positive value or the period in which the current takes a negative value due to the DC current becomes longer. And the absolute value of the peak value increases.

On the other hand, the current induced in the molten metal as the conductor is determined by the time change of the magnetic flux density due to the alternating current and the amplitude of the alternating current at the place where the induced current flows, and the Lorentz force in the conductor is In the conductor, the product of the magnetic flux density, which takes one of the signs longer, and the induced current, which oscillates in the same cycle as the alternating current in both positive and negative, except for the phase difference, is determined by the product of the induced current and the magnetic flux density. Generates the Lorentz force. Here, if a DC current larger than the amplitude of the AC current is applied, the magnetic flux density does not take a value of zero. Therefore, if a DC current is superimposed on an AC current, a Lorentz force larger by a magnetic flux density having a larger peak value can be generated as compared to a case where an AC current is simply applied. Moreover, in an inductive device in which the DC component power is relatively very small as compared with the AC component power, the power for applying the DC current is smaller than the power for applying the AC current. I can do it.

The steel shell 8 in the apparatus shown in FIG. 3 has physical properties of conductivity σ = 5.0 × 10 ⁶ (S / m) and magnetic permeability μ = 300 μ ₀ (H / m). When a current of 1.0 × 10 ⁶ (cos ωt + 1) (AT / m ² ) is applied to the induction coil 5 using a ferromagnetic material, the Lorentz force changes as shown in FIG. It can be seen that the efficiency is dramatically improved by covering the induction coil and the refining vessel with a ferromagnetic material and applying a current obtained by superimposing a DC current on an AC current to the induction coil. In this case, the third
The calculation is performed by replacing the expression and the fourth expression with the following expression.

[0030]

(Equation 2)

FIG. 5 shows a third embodiment of the present invention. In this embodiment, the gas blowing device for the molten metal is not a bottom chamber, but, for example, a tap hole or a ladle of a converter. It is provided in a pipe through which molten metal flows, such as a nozzle from a to a tundish.

The gas blowing device for the molten metal 21 configured as the secondary refining device has an outer peripheral wall 22 made of a refractory brick defining a flow path and a porous for blowing an inert gas into the flow path. Plug 26 is outer wall 22
Are provided at a plurality of positions. Furthermore, the outer peripheral wall 22
Is provided, and an AC current from an AC power supply 24 is supplied to the induction coil. The outer peripheral wall 22 is covered with an iron shell 27 made of a ferromagnetic material together with the induction coil 23.

Also in this case, when a current is applied to the coil 23, a Lorentz force acts on the molten metal 21 flowing in the direction shown by the arrow 29 in the radial direction as shown by the arrow 30. That is, since this force acts on the portion where the bubble 28 is generated or on the bubble 28 itself, the bubble is detached at twice the frequency of the alternating current. Here, by appropriately selecting the frequency and the current value or the voltage value of the alternating current, a desired bubble dispersing and refining action can be obtained, so that the decarburization reaction by dissolved oxygen in the molten steel is promoted,
Efficient secondary refining becomes possible.

In this apparatus, when the dimensions of each part are set as shown in FIG. 5 (unit: mm), and the conditions of each physical property value, current density and frequency are the same as in the first embodiment, Lorentz The result of the force is the same as in the first embodiment, and the frequency dependence is also consistent with FIG.

FIG. 6 shows a fourth embodiment of the present invention. This device is the same as the guiding core in the third embodiment shown in FIG.
The AC power supply 24 and the DC power supply 25 are connected in series to the file 23 , and the other matters are not different from those of the third embodiment, so the description thereof is omitted. Also in this apparatus, when the Lorentz force was obtained under the same physical property values, current densities and frequency conditions as in the second embodiment, the result is that the Lorentz force increases dramatically as in the second embodiment. In this embodiment, the same effect can be obtained even if the power supply section is configured by connecting an AC power supply and a DC voltage power supply in parallel.

In each of the above embodiments, mercury is used as an example of the molten metal. However, the present invention is not limited to this, and can be applied to metals such as aluminum, titanium, and copper. Needless to say, the present invention can be applied to other processes using electromagnetic force.

[0037]

As described above, according to the present invention, the bubbles of the gas to be blown are miniaturized and dispersed, so that the area of the interface between the molten metal and the gas is increased and the reaction rate is increased. I do. Accordingly, it is possible to shorten the processing time and improve the productivity in the refining process and the like. Moreover, by covering the coil and the container with a ferromagnetic material,
Since the magnetic field generated by the coil is confined and concentrated in the container, the efficiency of using electric power is increased.
In addition, power consumption can be reduced. Also, if a DC current is superimposed on an AC current, a large Lorentz force can be generated by a magnetic flux density having a large amplitude as compared with a case where an AC current is simply applied. In addition, power consumption can be reduced at a higher level.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view showing a first embodiment of a bubble miniaturization apparatus according to the present invention.

FIG. 2 is a graph comparing electromagnetic force when an induction coil is covered with a ferromagnetic material and when it is not covered.

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

FIG. 4 is a graph showing a time change of Lorentz force according to a second embodiment of the present invention.

FIG. 5 is a view similar to FIG. 1, showing a third embodiment of the present invention.

FIG. 6 is a view similar to FIG. 1, showing a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION 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 shell 9 Bubble 10.11 Arrow 18 Iron shell 21 Molten metal 22 Outer wall 23 Induction coil 24 AC power supply 25 DC Power supply 26 Porous plug 27 Iron skin 28 Bubbles 29/30 Arrow

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyoshi Wajima 20-1 Shintomi, Futtsu-shi Nippon Steel Corporation Technology Development Division (72) Inventor Eiichi Takeuchi 20-1 Shintomi, Futtsu-shi Nippon Steel Corporation Technology Within the Development Division (72) Inventor Takehiko Fuji 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Division

Claims (4)

(57) [Claims] A bottom chamber recessed at the bottom of a refining vessel for storing molten metal; a gas outlet provided at an appropriate position in the bottom chamber; a coil wound around the bottom chamber; In a molten metal refining apparatus having a power supply for supplying current or voltage to a coil, the bottom chamber and the coil are covered with a magnetic shielding material made of a ferromagnetic material, and the power supply is And a means for applying a current or voltage of which the size changes. 2. The power supply device according to claim 1, wherein the power supply device has means for superimposing a positive current or a positive voltage on the current or the voltage whose magnitude changes with time, respectively. Molten metal refining equipment. 3. A molten metal refining system comprising: a pipe having a gas outlet in a proper position for flowing molten metal; a coil wound around the pipe; and a power supply for supplying a current or voltage to the coil. In the device, the tube and the coil are covered with a magnetic shielding material made of a ferromagnetic material, and the power supply device has means for applying a current or a voltage whose magnitude changes with time. A molten metal refining apparatus, characterized in that: 4. The power supply device according to claim 3, wherein said power supply device has means for superimposing a positive current or a positive voltage on a current or a voltage whose magnitude changes with time, respectively. Molten metal refining equipment.