JP3840060B2 - Plasma heating apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma heating apparatus and method for generating a plasma arc to heat a heated object such as molten steel in a tundish.
[0002]
[Prior art]
Conventionally, plasma heating apparatuses have been put into practical use in various industrial fields. For example, in continuous casting equipment, a tundish is provided between the ladle and the mold, and the molten steel from the ladle is received by the tundish and then poured into the mold. The decrease in temperature has a great influence on the slab quality. Therefore, plasma heating is performed on the molten steel in the tundish in order to prevent the molten steel temperature from decreasing.
[0003]
That is, an anode and a cathode are provided in a tundish, and a high voltage is applied between them to generate a plasma arc between the anode and the molten steel and between the cathode and the molten steel, There is known a plasma heating apparatus that heats molten steel.
[0004]
[Problems to be solved by the invention]
However, in the conventional plasma heating apparatus, not all of the plasma current for generating the plasma arc flows through the molten steel, but a part of the plasma current directly flows between the anode and the cathode through the space between the anode and the cathode. I understood that it would flow. This part of the plasma current (hereinafter referred to as “leakage plasma current”) does not participate in the generation of the plasma arc. Therefore, there is a problem that the heating efficiency with respect to the input power is reduced due to the generation of the leakage plasma current.
[0005]
The present invention has been made in view of the above points, and an object thereof is to improve the heating efficiency by reducing the leakage plasma current flowing in the space between the anode and the cathode.
[0006]
[Means for Solving the Problems]
  The plasma heating apparatus of the present invention includes an anode and a cathode disposed in a space above a heated body, and heats the heated body by applying a voltage to the anode and the cathode to generate a plasma arc. A plasma heating apparatus configured as described above, wherein a gas blowing means blows a gas that increases the electrical resistance of the space into the space between the anode and the cathode. It is configured to suppress the flowing leakage plasma current, and the amount of gas blown out by the gas blowing means is 2 to 20 times the amount of the amount of gas blown from the anode and the amount of gas blown from the cathode It has the characteristics. The gas blown out from the gas blowing means is a gas having a temperature lower than the ambient temperature, for example.
[0013]
Another feature of the plasma heating apparatus according to the present invention is that a gas blowing direction by the gas blowing means is a direction directly hitting a plane formed by the anode torch plasma and the cathode torch plasma. It is in.
[0017]
Another feature of the plasma heating apparatus of the present invention is that the gas blown out from the gas blowing means is the same as the gas existing from the beginning in the space where the anode and the cathode are arranged. It is in.
[0018]
Another feature of the plasma heating apparatus of the present invention is that the gas blown out from the gas blowing means is at room temperature.
[0019]
Another feature of the plasma heating apparatus of the present invention resides in that the gas blown out from the gas blowing means is an inert gas.
[0020]
Another feature of the plasma heating apparatus of the present invention is that the inert gas is argon gas.
[0021]
Another feature of the plasma heating apparatus of the present invention is that it includes a control means for controlling the gas blowing means.
[0022]
Another feature of the plasma heating apparatus of the present invention is that it comprises optical observation means for optically observing the generated plasma arc, and the control means is in accordance with the observation result of the optical observation means. Thus, the gas blowing means is controlled.
[0023]
Another feature of the plasma heating apparatus according to the present invention is that the plasma heating apparatus includes a measuring unit that measures at least one value of a voltage and a current related to at least one of the anode and the cathode at a predetermined position. The control means controls the gas blowing means according to the measurement result of the measurement means.
[0024]
Another feature of the plasma heating apparatus according to the present invention is that the object to be heated is a conductor.
[0025]
Another feature of the plasma heating apparatus according to the present invention is that the anode and the cathode are provided in a tundish to heat the molten steel in the tundish.
[0026]
Another feature of the plasma heating apparatus of the present invention is that a gas supply port for blowing out a gas having a temperature lower than the ambient temperature is provided in the tundish.
[0027]
Another feature of the plasma heating apparatus of the present invention is that a gas supply pipe for supplying the gas to the gas supply port is fixed to the tundish.
[0028]
  The plasma heating method of the present invention includes an anode and a cathode disposed in a space above a heated body, and heats the heated body by applying a voltage to the anode and the cathode to generate a plasma arc. A plasma heating method configured as described above, wherein a leakage plasma current flowing between the anode and the cathode is generated by blowing a gas that increases an electrical resistance of the space into the space between the anode and the cathode. It is characterized in that the amount of gas blown out is 2 to 20 times the sum of the amount of gas blown from the anode and the amount of gas blown from the cathode.
[0029]
In the present invention as described above, the temperature of the space between the anode and the cathode can be lowered by blowing, for example, argon gas at room temperature into the space between the anode and the cathode in the tundish. Thus, if the temperature of the space between the anode and the cathode is lowered, the electrical resistance of the space can be increased, and the leakage plasma current flowing through the space between the anode and the cathode can be suppressed.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a plasma heating apparatus and method according to the present invention will be described below with reference to the drawings.
[0031]
FIG. 1 is a diagram schematically showing a configuration of a plasma heating apparatus for heating molten steel in a tundish. In the figure, reference numeral 1 denotes a torch used as a cathode K. At a position above the surface of the molten steel 102 in the tundish 101, its tip is directed to the surface of the molten steel 102, and a predetermined interval (L_K).
[0032]
Reference numeral 2 denotes a torch used as the anode A. The torch 1 is arranged in parallel to the torch 1 with a predetermined interval, and the tip of the torch 1 is located above the surface of the molten steel 102 in the tundish 101. To a predetermined interval (L_A(Here, L_A= L_K)) Is arranged.
[0033]
Reference numeral 3 denotes a power source for applying a high voltage to the anode A and the cathode K. In the present embodiment, the molten steel 102 in the tundish 101 corresponds to the heated object in the present invention.
[0034]
In the plasma heating apparatus configured as described above, a high voltage is applied to the anode A and the cathode K, and a plasma current is passed through the molten steel 102 as indicated by a dotted line in the figure. At this time, plasma arcs (torch plasma) 7A and 7K are generated through the gas existing between the surface of the molten steel 102 and the torches 1 and 2, and the molten steel 102 in the tundish 101 is heated.
[0035]
Here, when the plasma arc is generated, argon gas is blown into the tundish 101 from the anode A and the cathode K, and the argon gas is filled into the space above the surface of the molten steel 102 in the tundish 101 to obtain a positive pressure. I am doing so. This is because if the oxygen is present in the tundish 101, it is difficult for the plasma arc to be generated. Oxygen is discharged from the tundish 101 to facilitate the generation of the plasma arc.
[0036]
FIG. 2 shows an equivalent circuit of the plasma heating apparatus for molten steel in the tundish shown in FIG. In the figure, A, K, and 3 are the anode A, the cathode K, and the power source 3 shown in FIG. 1, and a circuit that is connected by four resistors is configured in an equivalent circuit. Specifically, the resistance R of the molten steel 102 is between the anode A and the cathode K._S, Spatial resistance (plasma resistance) R between the anode A and the surface of the molten steel 102_P, And space resistance (plasma resistance) R between the cathode K and the surface of the molten steel 102_PThe combined resistance due to the three resistances and the space resistance R between the anode A and the cathode K_AKAre connected in parallel.
[0037]
The combined resistance R between the anode A and the cathode K is given by
1 / R = 1 / R_AK+ 1 / (2R_P+ R_S)
That is,
R = R₀・ R_AK/ (R₀+ R_AK)
However, R₀= 2R_P+ R_S
Given by.
[0038]
In consideration of the equivalent circuit shown in FIG. 2, in order to suppress the leakage plasma current represented by the arrow 103 in FIG._AKIt can be seen that the resistance value [Ω] of this should be increased. Hereinafter, in order to suppress the leakage plasma current, the space resistance R between the anode A and the cathode K, which is a resistance against the leakage plasma current._AKAn example of increasing the value will be described.
[0039]
(First embodiment)
Generally, the resistance value R of the conducting wire is expressed by the following formula (1)
R = ρ · L / S (1)
Given by. Note that ρ is the electrical resistivity, and is determined by the substance and temperature of the conductive wire. L is the length of the conducting wire, and the resistance value R is proportional to the length L of the conducting wire. Further, S is a cross-sectional area, and the resistance value R is inversely proportional to the cross-sectional area S of the conducting wire.
[0040]
Spatial resistance R between anode A and cathode K_AKThe resistance value can be expressed in the same manner as in the case of the conducting wire. That is, the following formula (2)
R_AK= Ρ_AK・ L_AK/ S_AK  ... (2)
Can be considered to hold.
[0041]
Therefore, space resistance R_AKIn order to increase the resistance value, the spatial distance L between the anode A and the cathode K_AKIt is conceivable to increase Actually, as shown in FIG. 3, by increasing the spatial distance between the anode A and the cathode K, it was possible to reduce the leakage plasma current and increase the output relative to the input power proportionally.
[0042]
(Second embodiment)
As shown in FIG. 4, in the second embodiment, a solid resistor 8, which is a material with high electrical and low efficiency, is disposed in the space between the anode A and the cathode K. In the figure, the same reference numerals are given to the components described in FIG. 1, and the description thereof is omitted. By arranging the solid resistor 8 in this way, the space resistance R between the anode A and the cathode K is determined._AKCan be increased, the leakage plasma current can be reduced, and the output relative to the input power can be increased proportionally. In addition, space resistance R between anode A and cathode K_AKAs long as the resistance value is increased, the material and shape of the solid resistor 8 are not limited.
[0043]
(Third embodiment)
In FIG. 5, the structure of the plasma heating apparatus of the molten steel in a tundish of a 3rd Example is shown typically. In the figure, the same reference numerals are given to the components described in FIG. 1, and the description thereof is omitted. Reference numeral 4 denotes a gas outlet, which is formed on the ceiling surface of the tundish 101. As will be described in detail later, the gas outlet 4 is formed so as to blow out argon (Ar) gas between the torches 1 and 2.
[0044]
Reference numeral 5 denotes a gas supply device that supplies argon gas into the tundish 101 through the gas outlet 4. A gas supply pipe 6 is fixed to the tundish 101 via the gas supply device 5.
[0045]
The temperature (atmosphere temperature) of the argon gas filled in the tundish 101 is several thousand [K], and when argon gas at room temperature is blown into the argon gas, air is blown between the torches 1 and 2, that is, the anode A and the cathode K. The ambient temperature of the space between them greatly decreases.
[0046]
Here, space resistance R between anode A and cathode K_AKIs expressed by the above equation (2), the electrical resistivity ρ_AKIs determined by the material of the space, in this embodiment, the argon gas filled in the tundish 101. And its electric low efficiency ρ_AKAs shown in FIG. 6, the value is large when the temperature is low, and is small when the temperature is high.
[0047]
Therefore, in this embodiment, the room temperature argon gas is blown out from the gas blowout port 5 to reduce the atmospheric temperature of the space between the anode A and the cathode K, whereby the electric resistivity ρ_AKTo increase the space resistance R_AKThe resistance value is increased. In this way, space resistance R_AKAs the resistance value increases, the leakage plasma current can be reduced, and the output relative to the input power can be increased.
[0048]
If the temperature is lowered by a gas such as argon gas as in the present embodiment, the spatial distance between the anode A and the cathode K is increased as in the first embodiment, or the second embodiment is performed. Compared with the arrangement of the solid resistor 8 as in the example, this is advantageous in terms of downsizing the device and cost.
[0049]
In FIG. 5, reference numeral 9 denotes a control unit that controls the gas supply device 5. Reference numeral 10 denotes an optical observation unit such as a CCD for optically observing plasma arcs (torch plasma) 7A and 7K generated between the surface of the molten steel 102 and the torches 1 and 2. In this way, the plasma arcs 7A and 7K are observed, and the results are fed back to the control unit 9, thereby controlling the timing and amount of blowing out the argon gas. For example, when the plasma arcs 7A and 7K with respect to the input power are weak under the same conditions, it is determined that a leakage plasma current is generated, and the argon gas is controlled to be blown out from the blowing port 4. That's fine. By performing feedback control in this way, it is possible to eliminate wasteful use of argon gas and reduce running costs. In addition, for example, the control may be performed by measuring the input voltage and the total current value and feeding back the measurement result to the control unit 9.
[0050]
FIG. 7 shows a specific example of a plasma heating apparatus for molten steel in tundish. In the figure, 201 is a tundish, 202 is a tundish cover, and 203 is an opening formed in the tundish cover 202. A heating chamber is formed in the tundish 201 by a weir 204.
[0051]
205 and 206 are long cylindrical plasma torches, and 207 is a part of the moving device of the plasma torches 205 and 206. Although not specifically shown, there are other cooling water pipes, gas pipes, energizing cables, etc. is set up. The plasma torches 205 and 206 are moved from the horizontal state to the standing state shown in FIG. Then, as shown by the arrows in the figure, the sheet is moved up and down and inserted into the tundish 201 from the opening 203. In this state, a plasma arc is generated. The tip length of the plasma torches 205 and 206 is changed to adjust the arc length and adjust the output.
[0052]
Reference numeral 208 denotes a gas blowing port formed in the tundish cover 202, which blows out argon (Ar) gas from a gas supply source (not shown) between the plasma torches 205 and 206 in the heating chamber of the tundish 201.
[0053]
Although the so-called twin torch type plasma heating apparatus has been described with reference to FIG. 5, as shown in FIG. 8, a so-called single torch type (provided only with a torch used as the cathode K, the anode A terminal is connected to the side wall of the tundish 1). Or a plasma heating apparatus provided in the above. Also in this case, the electrical resistivity ρ is reduced by blowing the argon gas at room temperature as described above to lower the ambient temperature between the anode A and the cathode K._AKTo increase the space resistance R_AKThe resistance value can be increased.
[0054]
Further, the gas outlet 4 may be one or plural. For example, as shown in FIG. 9, a plurality of gas outlets 4 may be arranged in a line at a substantially central position between the anode A and the cathode K on the ceiling of the tundish 101. Further, as shown in FIG. 10, gas blowing ports 4 may be arranged on the anode A side and the cathode K side, respectively, on the ceiling of the tundish 101.
[0055]
Hereinafter, with reference to FIGS. 11 to 13, the blowing direction and the blowing amount of a gas having a temperature lower than the ambient temperature (room temperature argon gas) will be described. First, the gas blowing direction will be described. As shown in FIGS. 11 and 12, the gas is made to directly contact a plane formed by the torch plasma 7A of the anode A and the torch plasma 7K of the cathode K. This effectively increases the direct resistance between the anode A and the cathode K and increases the plasma output.
[0056]
In FIG. 11, in the blowing direction indicated by arrows 41 and 43, the gas does not directly contact the plane formed by the torch plasma 7 </ b> A of the anode A and the torch plasma 7 </ b> K of the cathode K. In the blowing direction indicated by 42, the gas directly hits the plane formed by the torch plasma 7A of the anode A and the torch plasma 7K of the cathode K, so that the plasma output increases.
[0057]
Similarly, in FIG. 12, in the blowing direction indicated by arrows 44 and 46, since the gas does not directly hit the plane formed by the torch plasma 7A of the anode A and the torch plasma 7K of the cathode K, the increase in plasma output is small. In the blowing direction indicated by the arrow 45, the gas directly hits the plane formed by the torch plasma 7A of the anode A and the torch plasma 7K of the cathode K, so that the plasma output increases.
[0058]
Next, the amount of gas blowout will be described. In FIG. 13, an amount q obtained by adding the amount Q of gas blown from the anode A and the amount of gas blown from the cathode K to the amount Q of blown gas (room temperature argon gas) lower than the ambient temperature. This represents the relationship between the ratio k (= Q / q) and the rate of increase in plasma output.
[0059]
When the ratio k is small, the increase in the direct resistance between the anode A and the cathode K is small, so the increase in the output increase rate is small and almost ineffective, but the output increase rate is around when k exceeds 2. The effect becomes significant.
[0060]
The output increase rate is saturated when the ratio k exceeds 20. In this state, the leakage plasma current directly flowing between the anode A and the cathode K becomes almost zero, and hardly contributes to the increase in output. Therefore, even if more gas is blown out, the effect of increasing the output is small, and the running cost by applying the gas is increased. Therefore, no further gas blowing is required.
[0061]
Considering the above, the ratio k, that is, the amount Q of the gas (room temperature argon gas) lower than the ambient temperature, the amount of gas blown from the anode A, and the amount of gas blown from the cathode K It can be said that it is desirable that the ratio to the amount q obtained by adding to be a value between 2 and 20.
[0062]
(Fourth embodiment)
In the fourth embodiment, the space resistance R between the anode A and the cathode K using a gas such as argon gas is the same as the third embodiment._AKThe resistance value is made larger, but the configuration is different from that of the third embodiment. FIG. 14 is a diagram schematically showing the configuration of the torch 1 (2) used in the plasma heating apparatus for molten steel in the tundish according to the fourth embodiment.
[0063]
The overall configuration of the plasma heating apparatus is the same as that described with reference to FIG. 1, but as shown in FIG. 14, an annular opening 11 is formed at the tip of the torch 1 (2). The argon gas is blown out so as to surround the plasma arc (torch plasma) 7A (7K). Thus, by blowing out argon gas so as to surround the plasma arc 7A (7K), the plasma arc 7A (7K) is prevented from being disturbed, and energy loss due to the disturbance is suppressed to a low level, thereby obtaining a stable plasma arc 7A (7K). It becomes possible.
[0064]
In the configuration as described above, in the present embodiment, an annular gas outlet 12 is also provided outside the annular opening 11. From the gas outlet 12 thus configured, as indicated by an arrow Y, the argon gas is blown out so as to further surround the argon gas (arrow X) blown out so as to surround the plasma arc 7A (7K). The argon gas blown out from the gas outlet 12 is water-cooled when passing through the annular passage 13 through which the gas outlet 12 communicates.
[0065]
In this way, the torch 1 (2) is formed into a double tube shape, and argon gas having a temperature lower than the ambient temperature is blown out along the argon gas surrounding the plasma arc 7A (7K). The atmospheric temperature of the space between K can be lowered. Therefore, electrical resistivity ρ_AKBecomes larger and space resistance R_AKCan be increased, the leakage plasma current can be reduced, and the output relative to the input power can be increased. Further, by blowing out argon gas from the gas blowing port 12, the argon gas blown out from the annular opening 11 can be blocked from the surroundings to extend the reach distance. Thereby, the effect | action which suppresses disorder of plasma arc 7A (7K) can be improved.
[0066]
In addition, in the 4th Example, although the gas blower outlet 12 was cyclic | annular, it is not limited to the shape. For example, as shown in FIG. 15, not all of the argon gas indicated by the arrow X is surrounded, but only a part, that is, only the cathode K side in the anode A and only the anode A side in the cathode K are cut off. Thus, the blowout port 12 may be provided so as to blow out argon gas having a temperature lower than the ambient temperature (see arrow Y).
[0067]
However, as shown in FIG. 14, if argon gas having a temperature lower than the ambient temperature is blown out so as to surround all of the argon gas indicated by the arrow X, the following effects can be obtained. That is, in addition to the leakage plasma current that flows directly through the space between the anode A and the cathode K, a plasma current that leaks from the anode A and the cathode K to the wall of the tundish 101 may be generated. In this case, if the argon gas is blown out so as to surround all of the argon gas indicated by the arrow X, such a plasma current can be suppressed.
[0068]
Further, as shown in FIG. 16, if an annular blowing port 12 is provided, and several walls 14 are provided in the circumferential direction of the blowing port 12 and the inner annular passage 13, they are separated as required. Thus, argon gas having a temperature lower than the ambient temperature can be blown out only at a desired location.
[0069]
In the third and fourth embodiments described above, an example using argon gas has been described. However, other types such as helium gas, neon gas, etc. may be used as long as they are monoatomic molecular gas which is an inert gas. Good.
[0070]
The embodiment of the present invention has been described above. Considering the equivalent circuit shown in FIG. 2 again, as described above, the combined resistance R between the anode A and the cathode K is
R = R₀・ R_AK/ (R₀+ R_AK)
However, R₀= 2R_P+ R_S
Given by.
[0071]
Here, the resistance value R_AKRatio m to resistance R
R_AK= M ・ R
, The ratio m and the combined resistance value R have a relationship as shown in FIG. That is, when the ratio m = 3 or less, the value of the combined resistance R is small, and it is difficult to increase the output. Therefore, in practice, about 3 ≦ m is practical, and if m ≦ 10000, the space resistance value R is more than that._AKIs increased so that it hardly contributes to the increase in output. Therefore, the resistance value R is in the range of 3 ≦ m ≦ 10000 by the various methods described in the first to fourth embodiments._AKShould be increased.
[0072]
Thus, the space resistance value R_AKAlthough some specific examples for increasing the value have been described, various other methods can be considered. For example, the distance L between the anode A (cathode K) and the molten steel 102_A(L_K) Is reduced to reduce the space resistance R_AKCan be made relatively large, so that the leakage plasma current can be suppressed.
[0073]
In the above-described embodiment, the leakage plasma current that directly flows in the space between the anode A and the cathode K has been described. However, the suppression means of the present invention can reduce the space between the anode A and the cathode K. Indirectly, for example, those that suppress leakage plasma current flowing through a tundish or the like are included. That is, in the example of using a gas such as argon gas, what has been described with reference to FIGS. 9 and 10 is merely an example, and the gas outlet 4 is formed at an arbitrary position depending on the location where the argon gas is to be blown out. do it.
[0074]
【The invention's effect】
  As described above, according to the present invention, the leakage plasma current flowing through the space between the anode and the cathode is generated by blowing the gas that increases the electrical resistance of the space into the space between the anode and the cathode. Since it was made to suppress, the heating efficiency with respect to input electric power can be improved. In addition, the plasma heating apparatus can be stably operated, and a stable plasma arc can be generated to perform good plasma heating.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of a plasma heating apparatus for molten steel in a tundish.
FIG. 2 is a diagram illustrating an equivalent circuit of the plasma heating apparatus described in FIG.
FIG. 3 is a diagram showing a relationship between a distance between an anode A and a cathode K and an output with respect to input power.
FIG. 4 is a diagram schematically showing a configuration of a plasma heating apparatus for molten steel in a tundish according to a second embodiment.
FIG. 5 is a diagram schematically showing a configuration of a plasma heating apparatus for molten steel in a tundish according to a third embodiment.
Fig. 6 Low electrical efficiency ρ_AKIt is a figure which shows the relationship between temperature.
FIG. 7 is a diagram showing a specific example of a plasma heating apparatus for molten steel in a tundish.
FIG. 8 is a diagram schematically showing the configuration of another plasma heating apparatus for molten steel in tundish.
FIG. 9 is a view showing an arrangement example of the gas outlets 4;
FIG. 10 is a view showing an arrangement example of gas outlets 4;
FIG. 11 is a diagram for explaining a gas blowing direction.
FIG. 12 is a diagram for explaining a gas blowing direction.
FIG. 13 is a graph showing an amount Q of a gas blown from the anode A and an amount q of a gas blown from the cathode K combined with a blowout amount Q of a gas (room temperature argon gas) lower than the ambient temperature. It is a figure showing the relationship between ratio k (= Q / q) and the output increase rate of plasma.
FIG. 14 is a diagram schematically showing a configuration of a torch used in a plasma heating apparatus for molten steel in a tundish according to a fourth embodiment.
FIG. 15 is a diagram schematically showing a torch of another configuration example.
FIG. 16 is a view schematically showing a cross section of a torch of another configuration example.
FIG. 17 shows a resistance value R_AKIt is a figure which shows the relationship between ratio m of resistance value R, and synthetic resistance value R.
[Explanation of symbols]
1, 2 torch
3 Power supply
4 Gas outlet
5 Gas supply device
6 Gas supply piping
7A, 7K plasma arc
8 Solid resistors
9 Control unit
10 Optical observation part
11 Annular opening
12 Gas outlet
13 Annular passage
A anode
K cathode
101 tundish
102 Molten steel

Claims (15)

A plasma heating apparatus comprising an anode and a cathode disposed in a space above a heated body, and configured to heat the heated body by generating a plasma arc by applying a voltage to the anode and the cathode. And
By blowing out a gas that increases the electrical resistance of the space into the space between the anode and the cathode by the gas blowing means, the leakage plasma current flowing between the anode and the cathode is suppressed,
The plasma heating apparatus characterized in that the amount of gas blown by the gas blowing means is 2 to 20 times the total amount of the gas blown from the anode and the gas blown from the cathode.   The plasma heating apparatus according to claim 1, wherein the gas blown out from the gas blowing means is a gas having a temperature lower than an ambient temperature.   3. The plasma heating apparatus according to claim 1, wherein a gas blowing direction by the gas blowing means is a direction directly hitting a plane formed by the anode torch plasma and the cathode torch plasma. 4.   The plasma heating apparatus according to claim 2, wherein the gas blown out from the gas blowing means is the same as the gas existing in the space in which the anode and the cathode are arranged.   The plasma heating apparatus according to claim 2, wherein the gas blown out from the gas blowing means is at room temperature.   The plasma heating apparatus according to claim 1, wherein the gas blown out from the gas blowing means is an inert gas.   The plasma heating apparatus according to claim 6, wherein the inert gas is argon gas.   The plasma heating apparatus according to any one of claims 1 to 7, further comprising a control unit that controls an amount of gas blown from the gas blowing unit and a blowing timing. An optical observation means for optically observing the generated plasma arc;
The plasma heating apparatus according to claim 8, wherein the control unit controls the gas blowing unit according to a result observed by the optical observation unit. For voltage and current related to at least one of the anode and the cathode, a measuring means for measuring at least one of the values at a predetermined location,
The plasma heating apparatus according to claim 8, wherein the control unit controls the gas blowing unit according to a measurement result of the measurement unit.   The plasma heating apparatus according to claim 1, wherein the object to be heated is a conductor.   The plasma heating apparatus according to any one of claims 1 to 11, wherein the anode and the cathode are provided in a tundish and the molten steel in the tundish is heated.   The plasma heating apparatus according to claim 12, wherein a gas supply port for blowing out a gas having a temperature lower than the ambient temperature is provided in the tundish.   The plasma heating apparatus according to claim 13, wherein a gas supply pipe for supplying the gas to the gas supply port is fixed to the tundish. A plasma heating method comprising an anode and a cathode disposed in a space above a heated body and applying a voltage to the anode and the cathode to generate a plasma arc to heat the heated body. And
By blowing out a gas that increases the electrical resistance of the space into the space between the anode and the cathode, the leakage plasma current flowing between the anode and the cathode is suppressed, and the amount of gas blowout is reduced. The plasma heating method is characterized in that the amount of gas blown from the anode and the amount of gas blown from the cathode is 2 to 20 times the total amount.

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