JP2001167873A - Anode for heating shift type plasma - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anode for heating a shift type plasma with a means of retarding the melt loss rate of a leading end to prolong the lifetime. SOLUTION: In a shift type plasma torch in which direct current is energized to heat melted metal in a container, and Ar plasma is generated while heating the melted metal, the shift type plasma torch comprises an electrode made of conductor metal having inner water cooling structure, a metallic protection body having inner water cooling structure provided at a distance from outside of the anode, and a means for supplying as containing Ar to gaps between the anode and the protection body, wherein a protrusion is provided at a central portion at the end of the cooling structure of the anode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an anode for a transition type plasma, and more particularly to an anode for a transition type plasma heating which is suitably applied for heating molten steel in a tundish.

[0002]

2. Description of the Related Art The outline of a DC twin-torch type plasma heating apparatus for heating molten steel in a tundish is shown in FIG.
It is like. Two plasma torches, ie, an anode 3 and a cathode 4, are inserted into the tundish cover 2, and a plasma arc 6 is generated between each of the torches 3, 4 and the molten steel 5 to heat the molten steel. It is. At this time, the electron flow 7 travels from the cathode 4 to the anode 3 through the molten steel 5.

FIG. 2 shows an example of the anode plasma torch. The figure shows a cross section of the tip of the anode torch. Anode 3
For example, oxygen-free copper is used as the material of the first substrate. The anode torch is a stainless steel or copper outer cylinder nozzle 8 that covers the outside.
And an inner copper anode body 3. The tip of the anode 3 has a flat disk shape, the anode 3 and the nozzle 8 both have a cooling structure, and the cooling water inlet and outlet water channels are separated by cylindrical partition plates 9 and 11, respectively. (In the figure, 1
0 and 12 indicate the flow of cooling water). Further, there is a gap 13 between the nozzle 8 and the anode 3, and the structure is such that plasma gas is blown out from the gap 13.

[0004]

One of the problems with the direct current anode plasma torch is that the anode tip is damaged and the life is short. At the time of plasma heating operation, the anode serves as a recipient of electrons, so that the electrons collide with the outer surface of the tip of the anode, and a large heat load is applied to the outer surface of the tip. The heat load applied to the anode tip is as large as several tens of MW / m ^2, and the heat transfer form on the anode tip cooling side is considered to be forced convection nucleate boiling heat transfer. In the case of forced convection nucleate boiling heat transfer,
The heat transfer coefficient is of the order of 10 ⁵ [W / m ² K], which is about 10 times larger than the heat transfer coefficient of forced convection heat transfer. Temperature rises, and a burnout occurs in which the heat transfer mode shifts to film boiling heat transfer. When transitioning to film boiling heat transfer, the heat transfer coefficient on the heat transfer surface drops sharply and the temperature on the heat transfer surface rises, eventually causing the anode tip temperature to exceed the melting point and cause erosion. There is.

FIG. 2 shows a heat load value causing a burnout—a burnout limit heat flux—in the case of the conventional anode cooling water channel structure shown in FIG. The graph shown in FIG. 21 shows that the cooling end of the anode 3 has a maximum radius Rcool = 2.
The abscissa represents the radius of the anode on the cooling side at the tip end, which is 2 mm, and the ordinate represents the burnout limit heat flux. In addition, the estimation of the burnout limit heat flux
nkevic formula (Zenkevich et al, J. Nuclear En
ergy, Part B, 1-2, 137, 1959), and the burnout limit heat flux w _BO [W / m ² ] is expressed by equation (1). Here, L, σ, G, ν, i, and i _cool in the equation (1) are physical quantities of the cooling water, and each is the heat of evaporation [J / k].
g], surface tension [N / m], weight speed [kg / m
² s], kinematic viscosity coefficient [m ² / s], enthalpy [J / k
g] and the mainstream enthalpy [J / kg]. FIG.
It can be seen from the graph of FIG. 1 that the burnout limit heat flux near the center is low. This is largely due to the flow rate of the cooling water flowing through the anode 3, and the cooling water flowing from above the center of the anode collides with the tip of the anode and the flow velocity is reduced, so that the burnout limit heat flux is also reduced. If the heat load applied to the outer surface of the anode tip exceeds the burnout limit heat flux, it is considered that burnout occurs on the anode tip cooling side and the temperature of the heat transfer surface rises, leading to erosion. The center of the tip is easily melted. In addition, although the burnout limit heat flux at the center of the anode tip is low, in the case of transitional plasma heating, heat tends to concentrate at the center of the outer surface of the anode tip. Further, once a current concentration point (anode spot) is formed on the anode surface, the current tends to be further concentrated on the anode spot. In other words, if the outer surface of the anode tip starts to be damaged by melting, the damage is further promoted, and finally the molten water is melted down to the cooling water side, leading to a life.

FIG. 3 illustrates the pinch effect on the plasma. The plasma 15 has a property (thermal pinch effect) that the plasma 15 tends to concentrate toward the center due to the gas flow 14 whose temperature is sufficiently lower than the plasma blown out from the gap 13 between the nozzle and the anode. The current density in the plasma is generally an increasing function with respect to the temperature, and it can be said that the current density in the plasma center portion 16 is larger than the average of the whole, so that the current density incident on the anode tip outer surface center portion 17 becomes larger. Accordingly, the degree of damage of the center portion 17 of the outer surface of the anode tip is greater than that of the outer peripheral portion 18 of the tip outer surface. In addition, electrons 21 moving toward the anode in the plasma receive a force 22 toward the center due to interaction with the rotating magnetic field 20 generated by the current 19 flowing in the plasma (magnetic pinch effect).

Further, as shown in FIG. 4, the tip of the anode is deformed outwardly convexly due to the pressure of cooling water flowing inside, thermal stress and creep. This convex deformation results in the formation of a projection 23 at the center 17 of the outer surface of the anode tip, and the electric field 32 concentrates on the projection 23. Electrons 21 moving in plasma
Since the current 19 is accelerated in the direction of the electric field 32, the current 19 tends to concentrate on the protrusion 23, which further causes the current to concentrate on the center of the outer surface of the front end of the anode. That is, the central portion 17 of the outer surface of the anode tip is more easily damaged. As the damage to the center portion 17 of the outer surface of the anode tip progresses, the cooling water channel 25 is finally broken at the center portion 17 of the outer surface of the anode tip, resulting in an inoperable state. As described above, the service life of the anode is significantly shortened due to the current concentration on the center of the outer surface of the anode tip.

FIGS. 5a to 5d illustrate the current concentration on the anode spot. In the initial state where the cleanliness of the outer surface of the anode tip is good (FIG. 5A), the electrons 21 enter the anode tip outer surface 26 almost perpendicularly. However, as described above, the current tends to concentrate on the center portion 17 of the outer surface of the anode tip shown in FIG. 4, and the high temperature of the outer surface of the anode tip causes copper to melt and evaporate, thereby causing copper vapor near the center of the outer surface. (FIG. 5b). The electrons in the evaporated copper atoms 28 are excited and ionized by the collision of the electrons 21. At this time, since the electrons 29 ionized from the copper atoms have a small mass and a high mobility, they are immediately incident on the outer surface of the anode tip. However, the copper ions 30 have low mobility and the vapor cloud 2
7, the vapor cloud becomes positively charged (FIG. 5).
c). Due to the positive charge potential of the vapor cloud 27, the electrons 21 in the plasma arc receive an acceleration toward the vapor cloud 27 (FIG. 5D). As a result, anode spot 3
When 1 occurs, the electrons in the plasma arc are concentrated at an accelerated concentration in the center of the outer surface of the anode tip near the outer surface of the anode tip. With such a mechanism, the damage to the tip of the anode proceeds at an accelerated rate. The present invention relates to the shape and material of the anode tip for improving the burnout limit heat flux of cooling, delaying the damage rate of the anode tip as described above, and extending the life of the anode for plasma heating. is there.

[0009]

Means for Solving the Problems To solve the above problems, the gist of the present invention is as follows: (1) A direct current is applied to the molten metal in the vessel to generate an Ar plasma, and the molten metal is discharged. A transfer-type plasma torch for heating, comprising an anode made of a conductive metal having an internal water-cooling structure, a metal protector having an internal water-cooling structure provided at a fixed interval outside the anode, and the anode and the protector A gas supply means for supplying a gas containing Ar to the gap, and a projection at the center on the cooling side at the tip of the anode. (2) The transfer-type plasma heating anode according to (1), wherein the center of the outer surface of the anode tip is concave inward. (3) The transition-type plasma heating anode according to any one of (1) and (2), wherein the entire outer surface of the anode tip is depressed inward. (4) The transfer type plasma torch according to any one of (1) to (3), wherein a rib is provided on a cooling side of the anode tip. (5) having a second gas supply means inside the anode;
(5) The transfer-type plasma heating anode according to any one of (1) to (4), wherein the gas supply means has a function of blowing gas from an outer surface of the anode tip. (6) The method according to (1), wherein the whole and / or center of the outer surface of the anode tip is concave and one or more permanent magnets rotatable in the circumferential direction are provided inside the anode. (5) The transfer-type plasma heating anode according to any one of (5). (7) The transition-type plasma heating anode according to any one of (1) to (6), wherein the anode tip material is a copper alloy containing Cr or Zr. It is.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the causes of damage to the center of the anode tip include burnout of the heat transfer surface on the anode tip cooling side, current concentration due to the pinch effect on plasma, and the like.
The convex deformation of the anode tip and the formation of the anode spot accelerate the current concentration. In the present invention, in order to prevent the occurrence of such burnout, current concentration, convex deformation and formation of the anode spot, the shape of the anode tip is changed, and a high-strength alloy is applied to the anode tip to prevent anode spot formation. A disturbance generator for the operation. In order to prevent burnout on the cooling heat transfer surface, it is conceivable to increase the effective area of the anode. However, there is a case where the effective area of the anode cannot be sufficiently increased due to a problem in the arrangement of the facilities and a problem of the limit of the torch holding facility because the mass of the torch is increased by enlarging the anode. Therefore, it is necessary to prevent the occurrence of burnout by making the tip of the anode an appropriate shape. FIG. 22 shows an example of the present invention according to the above (1) having such a shape.

In FIG. 22, a projection 51 for smoothing the flow of cooling water 10 is provided at the center on the cooling side of the anode tip. The projection 51 has a substantially conical shape, and its side surface is streamlined with respect to the flow 10 of the cooling water. This projection 5
By means of 1, it is possible to prevent a decrease in the flow rate of the cooling water at the center portion of the cooling water side on the tip of the anode, and to improve the burnout limit heat flux. In order to effectively increase the cooling water flow rate, the radius Rp of the bottom surface of the projection and the height Hp of the projection are respectively set to the partition plate 9.
It is preferable that the inner diameter Rin is 1/1 to 2/1 and 1/1 to 3/1.

[0012] By forming the tip of the anode into an appropriate shape, the anode
Aimed to prevent current concentration at the center of the outer surface of the tip
FIG. 6 shows an example of the present invention according to the above (2). Figure 6
Then, the center part 17 of the outer surface of the anode tip is depressed. Figure 7
Since the electric field 32 is incident perpendicularly to the conductor surface,
Compared to the comparative example shown in FIG.
Lowers the electric flux density at the center of the outer surface of the anode tip
The current concentration can be prevented. The area of the depression is the current
From the center of the anode tip to the anode tip to secure the concentration prevention area
A circle whose radius is 1/5 to 3/4 of the end radius Ra
Is desirable. In addition, the center height Hd of the concave portion depends on the current diffusion effect.
1/3 to 2/1 of the concave region radius Rd
It is desirable that Concave area radius Rd is outside the anode tip
It is preferably 1/3 to 3/4 of the table radius Ra. Ma
In the present invention, the gas supplied from the gas supply means
Is 100% by volume of Ar or 75% by volume or more of Ar
N due to voltage rise _Two0.1 to 25 vol%
It may be an unavoidable impurity. Also, the center of the outer surface of the anode tip
By recessing the portion, the protrusion 51 is installed.
The increase in thickness at the center of the tip can be reduced and the distance from the cooling surface can be reduced.
It also reduces the temperature of the outer surface of the tip
The effect can be aimed at.

In the present invention according to the above (3), the shape of the outer surface of the anode tip for preventing convex deformation of the anode tip can be improved.
An example is shown in FIG. In FIG. 8, in order to cancel convex deformation due to water pressure and thermal stress applied to the anode tip, a concave (crown) is formed inside the entire outer surface 33 of the anode tip.
The height Hc of the crown is 100 to 100 because the outer surface of the tip of the anode maintains a horizontal plane due to deformation during plasma heating.
Desirably, it is 500 μm.

In order to prevent convex deformation of the anode tip, it is necessary to maintain high rigidity of the anode tip even in a high temperature state. In the present invention according to the above (4), as one of the techniques for maintaining high rigidity, a rib is provided on the cooling surface side of the anode tip. FIG. 9 is a cross-sectional view of an anode in which ribs 34 are provided on the outer peripheral portion on the anode tip cooling surface side. One or more ribs are provided in the circumferential direction, preferably four or more ribs are arranged at equal intervals. The height Hr of the rib, the length Lr in the radial direction, and the width Dr are each 1/5 to 2/3 of the anode tip radius Ra, and the anode tip to maintain high rigidity and not to obstruct the flow of cooling water. It is preferable to set the radius Ra to １ ／ to ／ and the anode tip cooling water channel width Dc to 先端 to 1/1. But,
When ribs are installed in the cooling surface, it is necessary to change the shape of the cooling water channel and the partition plate. Therefore, in order to maintain high rigidity, high strength such as Cr-Cu, Zr-Cu or Cr-Zr-Cu is used. It is desirable to apply a material. From the above, it is possible to prevent current concentration on the center of the outer surface of the anode tip. However, as described above, when the anode spot is formed, further current concentration occurs on the anode spot. Even if an anode spot is formed, there is a possibility that current concentration may also occur in the anode spot.
An example of a disturbance generating device for preventing anode spot formation is shown in FIGS.

In FIG. 10 showing the example of the present invention according to the above (5), a second gas for blowing out a plasma working gas from the outer surface 26 of the anode tip to cause disturbance or swirl in the gas flow near the outer surface of the anode tip. By providing the supply means 43, the anode spot 31 can be moved. The second gas supply means 43 is preferably a cylindrical tube penetrating the outer surface of the anode tip, and the outer diameter of the cylindrical tube is set to 1 mm to 5 mm so as to reliably supply gas without obstructing the flow of the cooling water. The material is preferably stainless steel, copper or copper plated with corrosion prevention for corrosion prevention.
In addition, the effect can be obtained even by one line.
As shown in FIG. 0 and FIG. 20, it is preferable to install one at the center of the anode and 4 to 10 at equal intervals in the circumferential direction inside the cooling channel partition plate 9 installed inside the anode.

In FIG. 11 showing the example of the present invention according to the above (6), a permanent magnet 36 is embedded in the anode, and an external magnetic field 38 which fluctuates with time by rotating the permanent magnet.
(FIG. 19) to move the anode spot. As shown in FIG. 13, the blades 46 connected to the permanent magnets are provided in the cooling water channel, and the rotation of the permanent magnets can be performed by the flow of the cooling water.

As one of means for maintaining high rigidity, in the present invention according to the above (7), a copper alloy capable of maintaining high strength is applied to the tip of the anode. However, in order to keep the temperature of the outer surface of the anode tip low, the thermal conductivity of the copper alloy needs to be equal to or higher than that of oxygen-free copper which is a conventional material. As an example of a copper alloy satisfying such conditions, Cr-
There are Cu, Zr-Cu and Cr-Zr-Cu. For example,
In Cr-Zr-Cu, commercially available Cr 0.5-
There is 1.5%, Zr 0.08 to 0.30%, and the balance is copper.

[0018]

Embodiments of the present invention will be described below. 12, 13, 17, and 18 are cross-sectional views showing one embodiment of the present invention. The features of the anode shown in FIGS. 12 and 17 are as follows (1) to (6). FIG. 12 is a vertical sectional view of the present invention, and FIG. 17 is a horizontal sectional view of the present invention. (1) Anode tip outer surface radius Ra = 25 mm, anode tip cooling side radius Rcool = 22 mm, anode tip thickness Da = 3
mm. (2) Conical projection 5 installed at the center of the anode tip cooling side
1 has a bottom radius Rp = 15 mm and a height Hp = 20 mm, and the side surface has a streamline shape along the flow of the cooling water.

The graph shown in FIG. 23 is obtained by plotting the radius on the tip cooling side of the anode where the maximum cooling radius Rcool = 22 mm on the tip cooling side of the anode is plotted on the horizontal axis, and the burnout limit heat flux is plotted on the vertical axis. A broken line 52 in the drawing indicates a burnout limit heat flux on the tip cooling side heat transfer surface of the conventional anode (see FIG. 2), and a solid line 53 in the drawing indicates a burnout limit heat flux on the tip cooling side heat transfer surface in the embodiment of the present invention. Show. FIG. 23 shows that in the embodiment of the present invention, the burnout limit heat flux is improved as compared with the conventional anode, and the burnout limit heat flux is kept constant at a high level in the radial direction of the anode tip. Sex decreased.
Further, it is conceivable that the provision of the projection 51 increases the thickness of the central portion of the distal end and increases the temperature of the central portion of the outer surface of the distal end. However, there is no problem because the cooling heat transfer area of the projection 51 is large.

(3) The depression (crown) on the entire outer surface of the anode tip is a spherical surface having a curvature Rc of 1041 mm, and the height at the center of the tip is Hc = 300 μm. Due to this crown, the outer surface of the tip of the anode during the plasma heating operation becomes substantially flat due to thermal stress deformation. (4) Radius rd formed at the center 17 of the outer surface of the anode tip =
A spherical recess 40 having a curvature Rd of 15 mm in a range of 10 mm is provided. The height of the recess 40 at the center of the tip is Hd = 4 mm. As shown in FIG. 16, the electric field 32 incident on the center portion 17 of the outer surface of the anode tip is dispersed and the current density is reduced as compared with the conventional type having no concave portion 40. However, it is necessary to smoothly connect the boundary 41 between the concave portion on the outer surface of the anode tip and the outside thereof so as not to form a large convex portion. The curvature of the boundary 41 is desirably Rb = 30 mm or more. In the case of this embodiment, Rb = 50 mm.

(5) Since the outer surface of the anode tip is exposed to a high temperature of 500 ° C. or more, the conventional anode using oxygen-free copper may be deformed by creep. In particular, as the outer surface of the anode tip progresses and the tip thickness decreases, creep deformation increases and the anode tip deforms into a convex shape. Therefore, a copper alloy containing 0.08% of Cr and 0.15% of Zr was applied to the material of the anode. FIG. 14 shows the amount of creep deformation at the center (hc [mm] shown in FIG. 15) with respect to the thickness of a copper (or copper alloy) disk having a radius of 25 mm. In contrast to oxygen-free copper indicated by the straight line 49 in the figure, Cr-Zr-Cu indicated by the straight line 50 in the figure has a small creep deformation, and is particularly three orders of magnitude smaller when the anode tip thickness is 1.5 mm. In other words, Cr-Zr-Cu is less susceptible to creep deformation than oxygen-free copper, and can suppress convex deformation at the tip of the anode.

(6a) Eight outlets 42a to 42h for blowing the working gas to the outer surface of the anode tip are provided on the circumference of the outer surface of the anode tip and one outlet 42i.
Is placed at the center of the outer surface of the anode tip.
Inner pipe 43a for passing the working gas connected to 2a to 42h
To 43h inside the partition plate 9 and an inner tube 43i connected to the outlet 42i on the central axis of the anode. Further, the inner tubes 42a to 42h are slanted below the anode in order to cause swirling of the working gas. Outlets 42a-4
By causing the flow of the working gas near the outer surface of the tip of the anode to swirl by the working gas blown out from 2i, the anode spot can be moved. FIG.
The life of the transfer-type plasma heating anode according to the present invention was increased 1.5 to 2 times as compared with the conventional transfer-type plasma heating anode shown in FIG. 13 and 18 have the same features as (1) to (4) of the anode shown in FIGS.
The fifth feature has the following features, and the fifth feature has the following features. FIG. 13 is a vertical sectional view of the present invention, and FIG. 18 is a horizontal sectional view of the present invention.

(6b) The partition plate 9 inside the anode has two permanent magnets 36. These two permanent magnets 36a, 36
b is installed at a position symmetrical with respect to the anode symmetry axis, and is connected by a connecting rod 44. The connecting rod 44 is connected to a rotating shaft 45 installed vertically 5 mm above the center of the anode tip cooling side, and is permanently mounted. The magnets 36a and 36b are rotatable in a circumferential direction about a rotation axis. By installing the wings 46 fixed to the connecting rods 44 in the cooling water passage 47, the permanent magnets 36a and 36b rotate in the circumferential direction by the flow 48 of the cooling water. Near the outer surface of the anode tip, a permanent magnet 36
a, 36b form a permanent magnet 36
As a and b rotate, they fluctuate periodically with respect to time. Since the moving particles interact with the magnetic field, the movement of ions and electrons in the plasma is also affected by the time-varying magnetic field 38 (see FIG. 19). Therefore, even if an anode spot is formed on the outer surface of the anode tip, the charged particles are disturbed by a magnetic field that fluctuates with time, and can move the anode spot. As compared with the conventional transfer-type plasma heating anode shown in FIG. 2, the life of the transfer-type plasma heating anode according to the present invention is increased by 1.5 to 2 times.

[0024]

According to the present invention, the damage speed of the anode tip of the direct current twin torch type plasma heating apparatus can be delayed and the service life can be extended.

[Brief description of the drawings]

FIG. 1 is a schematic view of a tundish and a plasma torch.

FIG. 2 is a schematic view of a transfer type plasma anode for heating molten steel in a tundish according to the prior art.

FIG. 3 is an explanatory diagram of a pinch effect of plasma.

FIG. 4 is an explanatory diagram of current concentration due to convex deformation of the anode tip.

FIG. 5 is an explanatory diagram of current concentration due to formation of an anode spot.

FIG. 6 is a vertical sectional view of one example of a transfer-type plasma heating anode according to the present invention.

FIG. 7 is a schematic diagram of an electric field emerging from the tip of one example of the transfer-type plasma heating anode shown in FIG. 6;

FIG. 8 is a vertical sectional view of one example of a transfer-type plasma heating anode according to the present invention.

FIG. 9 is a vertical sectional view of one example of a transfer-type plasma heating anode according to the present invention.

FIG. 10 shows one of the transfer-type plasma heating anodes according to the present invention.
FIG. 4 is a vertical sectional view of an example.

FIG. 11 shows one of the transfer-type plasma heating anodes according to the present invention.
FIG. 4 is a vertical sectional view of an example.

FIG. 12 shows one of the transfer-type plasma heating anodes according to the present invention.
FIG. 4 is a vertical sectional view of an example.

FIG. 13 shows a transfer-type plasma heating anode 1 according to the present invention.
FIG. 4 is a vertical sectional view of an example.

FIG. 14 is a material comparison of the amount of creep deformation.

FIG. 15 is an explanatory diagram of the graph shown in FIG. 14;

FIG. 16 is a schematic view of an electric field emerging from the tip of the transfer plasma heating anode according to the prior art shown in FIG. 2;

FIG. 17 is a horizontal sectional view of the transfer-type plasma heating anode shown in FIG. 12;

FIG. 18 is a horizontal sectional view of the transfer-type plasma heating anode shown in FIG. 13;

FIG. 19 is a schematic diagram of a magnetic field in the present invention shown in FIG.

FIG. 20 is a horizontal sectional view of the transfer-type plasma heating anode shown in FIG. 10;

FIG. 21 shows a distribution of a critical heat flux of a burnout on a conventional heat transfer surface on the tip cooling side of an anode.

FIG. 22 shows a transfer-type plasma heating anode 1 according to the present invention.
FIG. 4 is a vertical sectional view of an example.

FIG. 23 shows the distribution of the critical heat flux of the burnout on the conventional anode and the conventional heat transfer surface on the cooling side of the tip of the conventional anode in the embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tundish 3 Anode 5 Molten steel 6 Plasma arc 7 Electron flow 9 Partition plate 10 Flow of cooling water 17 Central part of anode tip outer surface 19 Current 21 Electrons in plasma 23 Anode tip convex deformation part 26 Anode tip outer surface 31 Anode spot 29 Anode tip outer surface crown 32 Electric field 34 Rib 36, 36a, 36b Permanent magnet 38 Magnetic field 40 Anode tip concave part 42 Working gas outlet 43 Second gas supply means (small tube for working gas outlet) 51 Projection

Continued on the front page (72) Inventor Hiroyuki Mitake 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Junichi Kinoshita 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Inside the Kimitsu Works (72) Inventor Katsuhiro Imanaga 1 Kimitsu, Kimitsu City, Chiba Prefecture Inside Nippon Steel Corporation (72) Inventor Masahiro Toki 1 Kimitsu City, Kimitsu City, Chiba Prefecture Kimitsu Corporation Inside the steelworks (72) Inventor Yoshiaki Kimura 1 Kimitsu, Kimitsu-shi, Chiba F-term in the Nippon Steel Corporation Kimitsu Works (reference) 3K084 AA08 AA12 CA02 CA09 CB03 CC07 DA14

Claims (7)

[Claims] 1. A method according to claim 1, wherein a direct current is applied to the molten metal in the container.
A transfer type plasma torch for heating a molten metal while generating r plasma, comprising: an anode made of a conductive metal having an internal water-cooled structure; and a metal protection having an internal water-cooled structure provided at a predetermined interval outside the anode. A transfer-type plasma heating anode, comprising: a body; and gas supply means for supplying a gas containing Ar to a gap between the anode and the protection body, and a projection at a center of the anode tip cooling side. 2. The transfer-type plasma heating anode according to claim 1, wherein the center of the outer surface of the tip of the anode is recessed inward. 3. The transfer-type plasma heating anode according to claim 1, wherein the entire outer surface of the anode tip is depressed inward. 4. The transfer type plasma torch according to claim 1, wherein a rib is provided on a cooling side of the tip of the anode. 5. The anode according to claim 1, further comprising a second gas supply unit inside the anode, wherein the second gas supply unit has a function of blowing gas from an outer surface of a front end of the anode. Item 2. The transfer-type plasma heating anode according to Item 1. 6. The anode according to claim 1, wherein the whole and / or center of the outer surface of the tip of the anode is concave and one or more permanent magnets rotatable in the circumferential direction are provided inside the anode. 6. The transfer plasma heating anode according to any one of 1 to 5. 7. The transfer plasma heating anode according to claim 1, wherein the material of the anode tip is a copper alloy containing Cr or Zr.