JP2003213319A - Method for refining molten metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refining method with which the reaction speed is increased at a low cost in a ladle refining of molten steel including deoxidation, desulfurization, de-nonmetallic inclusion, degassing and reduction. <P>SOLUTION: Downward or upward spiral stream is introduced by setting a spiral rotating magnetic field generating apparatus on the same axis 14 as the center axis of the cylindrical ladle 11 to form circulating streams 7, 7' in the whole vessel, in which the core part and the outer peripheral part are made to flow in vertically reverse direction. Intense bubble-containing tornado streams 20 accelerating the circulating stream, are formed in the core part by applying the downward spiral stream in the gas bubbling under reducing pressure. Non-reacting molten steel at the lower zone is effectively shifted to a reaction range composed of four phases of gas-slag-molten steel-pseudo vacuum at the upper zone, and the improvement in refining speed and the enlargement of refining range are attained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining molten metal, particularly molten steel, and more particularly to a method for stirring molten steel, gas and slag, which has a strong influence on the refining rate and the content of refining reaction.

[0002]

2. Description of the Related Art Stirring of molten steel and slag is an important key for accelerating the reaction in the refining of molten steel such as oxidation, reduction, degassing and demetallized inclusions. The molten steel that has been refined in the melting furnace is transferred to a ladle, and with a slagless or suitable slag, by using a stirring device, a degassing device, a heating device, etc., to meet the product specifications and the next casting process, (1 ) Molten steel composition, temperature uniformity and target, (2) Deoxidation, desulfurization, demetallization, decarburization, degassing, etc. cleaning of molten steel, (3) Reduction and recovery of useful components in slag, etc. Has been refined.

Product quality is mainly related to refining content and its level, and refining cost is related to refining content and refining speed. If the speed is low, the cost will increase due to the necessity of reheating and the consumption of refractory materials. Molten steel in any refining method,
Agitation of the slag and refining medium gas has a great influence on the refining rate.

As a standard for stirring that affects the refining rate, the stirring energy density, that is, the power E per unit mass of molten steel is usually used.
(W / ton) is used.

On the other hand, a reaction rate coefficient k (1 / min) shown in the following equation is used for the reaction rate which is the main factor of refining efficiency. (C−Ce) / (Co−Ce) = exp (−k × t) C; concentration (1/1), Ce; equilibrium concentration, Co; initial concentration,
t: Time (minute) Based on the characteristic values E and k, precedent examples of various stirring methods are compared and examined.

Case (1) The following contents are disclosed in Japanese Examined Patent Publication No. 1-45633 and Document 1. The atmospheric pressure above the ladle is 30 to 1
By blowing gas into the molten steel from the bottom of the container while reducing the pressure to 50 torr, the molten steel upper layer is strongly stirred. Since the ladle capacity is small, the stirring energy density E is 0.2 (kW / ton), and the deoxidation rate coefficient k is 0.4 (1 /
Minutes) and it is quick enough to complete refining in a few minutes.

As a drawback, the gas bubbling under reduced pressure causes intense stirring in the upper layer of molten steel in principle, but extremely weak stirring in the lower layer due to expansion / floating of a limited amount of blown gas. It is rate limiting. Therefore, even if the small-capacity ladle is successful, there is a problem that the large-capacity ladle is inconvenient. Reference 1; The Institute of Metals; 3rd Internation
al Conference on CleanSteel, 1985, June, P.250

Case (2) Japanese Unexamined Patent Publication No. 7-179927 proposes a method of optimizing the processing conditions such as the amount of blown gas and the atmospheric pressure in order to solve the above problems. Although improvement can be made by this method, a decrease in reaction rate in large-capacity ladle cannot be denied.

Case (3) Various methods for induction stirring of molten steel are described in detail in ASEA JOURNAL 4,1971. A model in which a moving magnetic field device is arranged on the side surface of a cylindrical ladle to flow molten steel upward or downward along a wall surface, and a moving magnetic field coil is coaxially arranged on the outer periphery of the ladle to generate an upward flow along the entire circumference of the ladle wall surface. A given type, similarly a type in which a solenoid type single-phase coil is used to apply a pinch force to molten steel to stir it is shown. In either method, the average stirring energy density E is likely to be about 0.1 (kW / ton), and the reaction is accelerated.

One of the problems is that the reaction between the two phases is not strong because the slag is not directly stirred and the contact between the molten steel and the slag is laminar. The second problem is the gentle and irregular flow due to the low frequency, so that the molten steel treated by the slag and the untreated molten steel are mixed with each other, and the refining reaction is gradually reduced. The deoxidation rate coefficient k is usually estimated to be about 0.1 to 0.2 (1 / min). Therefore, when refining by slag such as deoxidation, desulfurization, and demetalization by non-metallic inclusions is the main constituent, shortening of refining time cannot be expected so much and reheating becomes necessary. As a result, a problem called erosion of refractory due to slag also occurs.

Case (4) There is a so-called ASEA-SKF method in which a ladle is provided with the above-mentioned induction stirring device, vacuum degassing device and arc reheating device to perform advanced refining. Equivalent values of E and k are obtained.

In this case, in order to endure refining for a long time, a basic high-grade refractory is used for the slag level on the ladle wall surface. The refractory has a large heat conduction and a large heat capacity and causes a heat loss of the molten steel to increase a reheating load. This promotes the corrosion of refractory materials. High quality can be obtained, but in addition to equipment costs,
Cost problems such as refining time, electric power, electrode rods and refractories are large.

Case (5) In Japanese Patent Laid-Open No. 11-335719, a molten steel in a cylindrical tundish is centrifugally agitated by a horizontal rotating magnetic field and a gas blowing condition is specified to disperse fine air bubbles in a non-metallic material. A method of promoting floating separation of inclusions is proposed.

Stirring is effectively used for air bubble dispersion, but the problem is that centrifugal stirring is not so large in mixing property. That is, since the homogenization time is not small, it is not always effective in many refining reactions. Further, the refining action is limited to adsorption and separation of non-metallic inclusions by bubbles, and it is impossible to obtain another refining effect because it has a single function.

[0015]

In order to solve the above-mentioned problems in the ladle refining process, the present invention uses a synergistic effect of effective induction stirring of molten metal and gas bubbling under reduced pressure to produce molten steel-slag-gas- It is intended to provide a refining method capable of promoting a reaction between pseudo vacuums and performing various refining with high efficiency, that is, in a short time and at low cost.

[0016]

To achieve the above object, the stirring energy density, which is the key to the reaction rate, was reexamined and two guidelines were obtained. One is the empirical relational expression between the known stirring energy density E and the reaction rate coefficient k (see FIG. 4).
Does not necessarily specify the limit of reaction rate. There seems to be a rate-determining process, and it seems that there is a macro mass transfer to the reaction region. The stirring energy applied does not act effectively on this mass transfer.

Another guideline is that various conventional stirring methods are batchwise processed in a container, and even if seemingly regular stirring, the reaction progressing portion, the reacted portion and the unreacted portion are mixed gently. Therefore, the reaction does not proceed efficiently. That is, from the above two points, it was found that there is a possibility of speeding up the reaction depending on the mode of stirring, and this hypothesis could be almost proved by experiments, so the following invention was constructed.

The first aspect of the present invention is to arrange an electromagnetic coil for generating a spiral rotating magnetic field, which is a combination of a rotating magnetic field and a moving magnetic field in the rotating axis direction, on the outer periphery of an upright cylindrical metallurgical container coaxially with the center axis of the container. A molten metal refining method is characterized in that the molten steel in the container is subjected to spiral rotation stirring.

In a second aspect of the invention, in the first aspect, the molten metal is molten steel, the metallurgical container is a ladle, the direction of the thrust of the spiral rotating magnetic field is downward, and a refining gas is blown into the molten steel from the bottom of the ladle. The molten metal refining method is characterized in that by depressurizing the atmosphere above the molten steel, a bubble-containing rising tornado flow is generated in the molten steel, and the molten steel in the lower layer in the ladle is moved / promoted to the upper layer. .

According to a third aspect of the invention, in the second aspect, the flow rate of the refining gas is 2 to 20 N liter / min / ton of molten steel,
The atmospheric pressure is maintained at 3 to 30 kPa, and the rotation speed of the spiral rotating magnetic field is 0.5 to 20 m / peripheral speed on the inner wall surface of the ladle.
It is a method for refining molten metal, which is characterized by setting to be seconds.

In a fourth aspect based on the first aspect, the molten metal is molten steel, the metallurgical container is a ladle, the refining slag is placed on the molten steel, and refining gas is supplied from the bottom of the ladle to 2
It is blown into the molten steel at a flow rate of ˜20 N liters / minute / tonne of molten steel, the atmospheric pressure above the slag is maintained at 3 to 30 kPa, the direction of the thrust of the spiral rotating magnetic field is upward, and the rotational speed of the vortex is 10 to 60 rpm. As to lower the molten steel of the lower layer in the ladle to the upper layer while suppressing the contact reaction between the molten slag and the refractory on the inner wall surface of the ladle by sinking the upper surface of the molten steel into a parabolic shape. It is a feature of refining molten metal.

A fifth invention is the third or fourth invention, wherein Mn, Cr, Ni, Cu, V, Nb, Mo, W and Z are included.
One or more oxides of n and Pb are contained in the refining slag, and C, Si, Al, Ca, CaC ₂ , S as a reducing agent.
A method for refining a molten metal, which comprises adding one or more kinds of iC to molten steel or slag in an approximately chemical equivalent amount to the oxide of the metal to reduce and recover the metal.

A sixth aspect of the present invention uses the fifth aspect of the invention, from molten steel containing evaporative impurities Zn, Pb, Sb, As or from slag containing oxides of the above metals. A method for refining a molten metal, characterized in that the above metal is removed by evaporation.

[0024]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view illustrating a refining apparatus applied to the first invention.

A cylindrical metallurgical vessel 1 lined with a refractory 2 is erected on the outer surface of a non-magnetic steel plate to hold a molten metal 3. A general rotating magnetic field device 5 is arranged on the outer periphery of the container 1 coaxially with the center axis 4 of the container 1, and the molten metal 3 is dragged by the magnetic field due to the generation of a rotating magnetic field due to energization, thereby causing a rotating motion, that is, a vortex flow. Occurs.

At this time, when the rotating magnetic field device 5 is largely reciprocated up and down by the elevator 6, the molten steel is also similarly subjected to the vertical electromagnetic force. A downward spiral rotating magnetic field is generated intermittently when the current is cut off when rising and energized only when falling. The molten metal 3 spirally descends along the wall surface of the container 1, reaches the bottom surface, and rises from the central portion of the bottom surface. The upper layer portion is attracted to the periphery in sequence, and a circulating flow 7 in the entire container is formed. The circulating flow 7 is not always regular and stable,
The added stirring energy is not wasted in the local mixing so much, and the molten metal parts effectively move to the upper layer part which is the main reaction region.

The method of generating the spiral rotating magnetic field can be considered other than this, but the method will be described as an example.

FIG. 2 is a schematic side view illustrating the structure of an apparatus applied to the refining method of the second invention. The second invention is an example in which the first invention is applied to the ladle refining, and an electromagnetic wave which holds a molten steel 13 in a cylindrical ladle 11 formed of an airtight and non-magnetic iron shell and emits a spiral rotating magnetic field. Coil 1
5 is arranged on the outer periphery of the ladle 11 coaxially with the ladle center shaft 14 and is energized to give the molten steel 13 spiral rotation stirring.

On the other hand, a vacuum cover 17 provided with an exhaust pipe 16
Then, the ladle 11 is sealed and the space inside the ladle is evacuated by the vacuum pump 18, whereby the refining atmosphere can be maintained at a predetermined pressure.

When a refining gas such as Ar gas is blown into the molten steel 13 from the bottom surface of the ladle 11 through a ventilation plug 19 made of a refractory material, the floating bubbles are subjected to the action of spiral rotation stirring. A tornado flow (tornado-like vortex) is formed around the center axis of the ladle, and becomes a strong upward flow, and the circulation flow 7 by spiral rotary stirring is steadily strengthened.

Molten steel in a boiling state due to gas injection,
The appearance of the slag surface changes to foam when the atmospheric pressure decreases due to the operation of the vacuum pump. There, a four-phase mixing region of bubbles-slag-molten steel-pseudo-vacuum due to violent disturbance 2
1 is formed.

In accordance with the refining treatment conditions, various reactions such as deoxidation, desulfurization, denonmetallic inclusions, degassing and reduction rapidly proceed in the mixing zone 21. As is well known, if slagless, it is degassed; if it is non-oxidizing basic slag, it is deoxidized.
For desulfurization, effective refining proceeds for non-metallic inclusions in the case of acidic slag and reduction recovery of useful metal oxides in the case of reducing slag.

FIG. 3 is a schematic side view illustrating the structure of an apparatus applied to the refining method of the fourth invention. The fourth aspect of the present invention is one in which the thrust direction of the spiral rotary stirring is reversed upside down in the second aspect of the invention, and a strong tornado flow is difficult to form, but a circulating flow 7'is formed. Similarly, the phenomenon of foaming in the molten steel upper layer is also accompanied.

If the stirring conditions such as the position of the electromagnetic coil, the magnetic flux density, the number of revolutions, and the thrust are properly set, the powerful eddy current causes the upper surface of the molten steel to sink into a parabolic shape, and the slag having a density lower than that of the molten steel has a centrifugal force. The difference pulls it to the center. The stirring method is effective for suppressing the slag / refractory contact reaction.

When carrying out the third and fourth inventions, Cr, V
When a reducing agent such as C, Si, etc., which is almost chemically equivalent to the oxide of an alloying element having a relatively low affinity for isooxygen, is added to the molten steel or slag, the oxide is rapidly reduced and almost all of the molten steel is dissolved. Will be collected.

As in the previous section, when electric furnace steelmaking dust, which is an industrial waste product, is added, Zn, Pb, etc. contained in a large amount in the dust are rapidly reduced by C, Si, etc. in the molten steel and evaporated.

The vapor is guided to the dust collector 22 while undergoing oxidation treatment in the middle of the exhaust pipe 16 and can be recovered there as high-concentration oxide.

[0038]

Next, it will be explained that a proper spiral flow is extremely effective in the refining reaction. The state of flow and mixing was observed by a water model using a transparent cylindrical container and a rotary stirring blade. In the case of a simple vortex flow, even if the ink is dropped on any part of the vortex, it diffuses concentrically, but the uniformity is unexpectedly slow.

When the spiral guide vanes were partially attached to the inner surface of the container, an ascending or descending spiral flow was easily obtained depending on the rotation direction. A relatively stable and regular circulation flow was observed in the cylinder core and the peripheral part in the upside down direction. In this case, the ink and the suspension rapidly became uniform. The first invention was constructed based on this fact.

When gas was blown into the simple vortex in the cylinder from the bottom, a spiral flow was recognized due to the combination of rotation and ascent, and a circulating flow of core rising and peripheral descending was also obtained. At the same time, although it was unstable, generation of bubble-containing tornado was also observed depending on the situation.

When gas was blown from the bottom of the cylinder while agitating downward with a spiral guide vane, the bubble-containing tornado and the circulating flow were stably maintained.

Next, when the pressure is depressurized above the liquid surface, the liquid surface rises rapidly and changes from boiling to foaming, making the boundaries between the gas phase, liquid phase and bubbles unclear and disturbing. It was observed that the tornado and circulating flow were maintained with the intensity.
The second invention was constructed based on this observation.

Next, the stirring energy will be examined. The blown refining gas forms bubbles on the plug 19 and immediately rises in temperature and expands to generate initial stirring energy. Next, the second due to the rise of bubbles and gentle expansion
When the stirring kinetic energy of (3) approaches immediately below the liquid surface, the third stirring energy is generated due to the rapid expansion due to the sudden decrease in the bubble external pressure (= molten steel static pressure + ambient pressure).

As described above, most of the various reactions proceed in the four-phase mixing region 20 of bubbles-slag-molten steel-pseudo-vacuum in the foaming / disturbing state, and as is well known, the speed of the reaction itself is extremely high. large. This comes from a sufficient amount of the third stirring energy. On the other hand, the fact that the overall reaction rate increases as the stirring energy increases in various processes suggests that the mass transfer to the reaction region is rate limiting.

As described in the preceding case (2), in the gas bubbling simply under reduced pressure, the first and second stirring energy amounts are usually insufficient with respect to the third stirring energy amount. The first invention reinforces the first and second stirring energies.

It is important that the amount of stirring energy as well as how the stirring energy works. That is, it is desirable that the stirring energy applied to the area other than the mixing zone is mainly consumed for the mass transfer. For that purpose, it is necessary that the stirring energy is not consumed for local disturbance and a large stable circulation flow is formed. The first invention not only strengthens the stirring energy, but also embodies the mechanism by which the added stirring energy effectively acts on the mass transfer through the formation of a circulating flow.

Next, the grounds for specifying the processing conditions in the third and fourth inventions will be described. The refining gas flow rate was set to 2 to 20 N liters / minute / ton of molten steel because 2 N liters / minute /
If the molten steel is less than ton, the working force is insufficient, 20N liter / min /
This is because if the molten steel exceeds the ton, blow-through phenomenon easily occurs due to coalescence of bubbles.

The atmosphere pressure is set to 3 to 30 kPa because it is 3
If it is less than kPa, it is advantageous for degassing, but it requires a steam ejector as an exhaust device, which is disadvantageous in terms of energy cost. At 3 kPa or higher, various pumps that are cost-effective for equipment and operation can be used. When it exceeds 30 kPa, the effect of gas bubbling under reduced pressure becomes small.

The reason why the rotation speed of the spiral rotating magnetic field is specified so that the peripheral speed on the outer peripheral surface of the molten steel is 0.5 to 20 m / min is that the induced electromagnetic wave is small when the relative speed of the molten steel and the moving magnetic field is small. This is because if the force is small, on the contrary, if it is large, it is consumed as induction heating in the iron skin or molten steel skin portion due to the skin effect, and the electromagnetic force becomes small. Based on the fact that the above range is practically applicable from cases and experiments.

In the fourth invention, the rotation speed of the vortex is set to 10 to 10.
The reason for specifying 60 rpm is as follows. When the strength of the spiral flow exceeds a certain limit, a vortex is formed. The shape of the vortex surface is parabolic. The depth of the depression is proportional to the square of the product of the inner diameter of the container and the number of rotations according to the forced vortex equation. The vortex causes the slag covering the surface of the molten metal to be centered and separated from the refractory wall. At 10 rpm or less, the depression depth becomes 0.2 m or less even in a large ladle, the centripetal force of the slag is weak, and the slag does not separate from the wall refractory. At 60 rpm or more, the eddy depth exceeds 1 m even with a small ladle, and the risk increases.

The fifth aspect of the invention does not disclose the methods of the cases (1) and (2), but has a strong reduction refining capability that is potentially possessed, that is, reduction and recovery of useful element oxides. It was specifically embodied. As is well known, in the reduction reaction of oxides in slag, mass transfer from the inside of the slag to the molten steel / slag interface is rate-determining. Gas bubbling under reduced pressure is extremely convenient for molten steel / slag disturbance, and the addition of a circulating flow by electromagnetic force enables efficient processing from reduction to finishing.

The elements to be reduced are Mn, Cr, Ni,
Cu, V, Nb, Mo, W, Zn, Pb and the like can be mentioned. Since Zn and Pb have a large vapor pressure at the steelmaking temperature, they are not recovered in the molten steel, but are discharged outside the system as steam, and are recovered by the dust collector 22, for example. C, Si, A as the reducing agent
1, Ca, CaC ₂ , SiC and the like are practical.

When a large amount of low-grade scrap is used as an iron source, impurities such as Zn, Pb, Sb and As in molten steel and their oxides in slag remain and increase, but the quality deteriorates. By the application of the third and fourth inventions, it is removed by reduction and evaporation.

[0054]

EXAMPLES Experiment 1 (Verification of Third Invention) The same ladle having a capacity of 30 tons was used for high carbon steel, and the deoxidation rate coefficient was compared as a comparative example between the method of case (1) and the method of the present invention. did. The processing conditions and results of the comparative example of several tens of charges are as follows:
70 to 1590 ° C., non-oxidizing basic slag is placed on undeoxidized molten steel, the dissolved oxygen amount is 65 to 85 ppm, the atmospheric pressure is about 14 to 21 kPa, and the Ar gas blowing amount is 15
0-200 N liters / minute, processing time 3-9 minutes. The amount of dissolved oxygen at the end of refining is 18 to 32 ppm, and the molten steel temperature is 1
535 to 1540 ° C, deoxidation rate coefficient k is 0.36 on average
It became (1 / min).

The downward spiral rotary stirring of the present invention was applied under the same conditions as above. Input 160kVA, frequency 1
A 2-pole rotating magnetic field of Hz was applied to the lower 1/3 region of the ladle. Since it is difficult to accurately calculate or actually measure the electromagnetic force, the stirring energy density was estimated to be about 0.2 kW / ton by roughly estimating from the measured value of the magnetic flux density distribution and the magnetic field moving speed. The processing time is 2.5 to 6.0 minutes, and the amount of dissolved oxygen at the end is 13 to 2
4 ppmm, molten steel temperature was 1540 to 1550 ° C, deoxidation rate coefficient k was increased to about 0.5 to 0.7, and refining efficiency was improved. Not only deoxidation due to the increase of deoxidation rate coefficient,
For desulfurization and other refining, a basis for improving efficiency is established.

Experiment 2 (Verification of Fourth and Fifth Inventions) Under the same conditions as in Experiment 1 for spring steel, both Cr ore equivalent to 1.0% by Cr content and V content by V content at the time of tapping. 0.15% equivalent was added to the slag immediately before refining.
A chemical equivalent amount of Si powder required for reduction of Cr and V was added.

In both cases, the Cr concentration in the slag was about 3 at the initial stage.
Although it was reduced from 0% to 0.4 to 0.7% and the reduction and recovery of Cr was sufficient, it took 8 minutes or more in the comparative example, and the present invention could be processed within 5 minutes.

Experiment 3 (Verification of Sixth Invention) The Zn removal reaction was confirmed and compared in the same manner as above. In the electric furnace melting step, electric furnace dust was inserted by about 1% of the molten steel amount. The composition of dust is about 25% ZnO and about 55% FeO. In the comparative example, Zn was added to the slag after ladle refining at 0.
01 to 0.03%, 10 to 30 ppm remaining in molten steel, 0.01 to 0.02% and 8 to 16 pp in the present invention, respectively.
Therefore, Zn was efficiently removed.

[0059]

According to the present invention, in the first aspect of the present invention, a spiral electromagnetic induction stirring flow along the inner surface of the cylinder is generated in the molten metal in the cylindrical container, so that mass transfer from the non-reaction region to the reaction region is promoted. And accelerate the refining reactions. In the second invention, the interaction between the downward spiral flow and the gas bubbling under reduced pressure synergistically acts on the circulating flow accompanied by the bubble-containing tornado flow in the region of the intense contact reaction between the gas-slag-molten steel-pseudo vacuum. Therefore, various refining reactions are further promoted. The third aspect of the invention presents the specific conditions of the second aspect of the invention. Using the fifth invention, the Cr added in the slag
Oxides of alloying elements such as ores can be reduced and recovered at high speed and with a good yield, and the melting loss of refractory material is small, which is advantageous in terms of cost. In the sixth invention, Z in molten steel or slag
The harmful oxides such as n are easily evaporated and removed. This effect is extremely effective in terms of cost, such as expansion of use of low-grade scrap and dissolution treatment of electric furnace dust, which is an industrial waste.

[Brief description of drawings]

FIG. 1 is a schematic side view illustrating a refining device applied to a first invention.

FIG. 2 is a schematic side view illustrating a refining device applied to a second invention.

FIG. 3 is a schematic side view illustrating a refining device applied to a third invention.

FIG. 4 is a diagram showing a relationship between a stirring energy density E and a deoxidation rate coefficient k.

[Explanation of symbols]

1: Metallurgical container 2: Refractory material 3: Molten metal 4: Central axis 5: Rotating magnetic field device 6: Elevator 7, 7 ': Circulating flow
11: Ladle 13: Molten Steel 14: Central Axis 15: Electromagnetic Coil 16: Exhaust Pipe 17: Vacuum Cover 18: Vacuum Pump 19: Vent Plug 20: Tornado Flow 2
1: 4 phase mixing area 22: Dust collector

Claims (6)

[Claims] 1. Melting in a container by arranging an electromagnetic coil for generating a spiral rotating magnetic field, which is a combination of a rotating magnetic field and a moving magnetic field in the rotating shaft direction, on the outer circumference of an upright cylindrical metallurgical container coaxially with the central axis of the container. A method for refining a molten metal, which comprises applying spiral rotation stirring to the metal. 2. The molten metal is molten steel, the metallurgical container is a ladle, the direction of the thrust of the spiral rotating magnetic field is downward, a refining gas is blown into the molten steel from the bottom of the ladle, and the atmosphere above the molten steel is depressurized. The molten metal refining method according to claim 1, wherein an ascending bubble-containing tornado flow is generated in the molten steel, and the molten steel in the lower layer in the ladle is moved / promoted to the upper layer. 3. The refining gas flow rate is set to 2 to 20 N liters / minute / ton of molten steel, the atmospheric pressure is maintained at 3 to 30 kPa, and the rotational speed of the spiral rotating magnetic field is set to 0.5 to about the peripheral speed on the inner surface of the ladle. The method for refining molten metal according to claim 2, wherein the refining method is set to 20 m / sec. 4. The molten metal is molten steel, the metallurgical container is a ladle, the refining slag is placed on the molten steel, and the refining gas is supplied from the bottom of the ladle at a flow rate of 2 to 20 Nl / min / ton of molten steel in the molten steel. And maintain the atmospheric pressure above the slag at 3 to 30 kPa, make the direction of the thrust of the spiral rotating magnetic field upward, and set the rotating speed of the vortex to 10 to 60 rpm to sink the molten steel upper surface into a parabolic shape and float. The method for refining molten metal according to claim 1, wherein the molten steel in the lower layer in the ladle is moved and promoted to the upper layer while suppressing the contact reaction between the slag and the refractory on the inner wall surface of the ladle that are being formed. . 5. Mn, Cr, Ni, Cu, V, Nb, M
One or more oxides of o, W, Zn and Pb are contained in the smelting slag, and C, Si, Al, Ca and C are used as a reducing agent.
The one or more kinds of aC ₂ and SiC are added to the molten steel or slag in an approximately chemical equivalent amount to the oxide of the metal to reduce and recover the metal. Method for refining molten metal. 6. A vaporizable impurity such as Zn, Pb, Sb,
A method for refining a molten metal, comprising vaporizing and removing the metal from a molten steel containing As or from a slag containing an oxide of the metal according to the method of claim 3 or 4.