JPS6049593A - Heater for molten metal by plasma arc - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to the structure and arrangement of a power supply electrode in a heating device for molten metal using a plasma arc.

BACKGROUND OF THE INVENTION In recent years, plasma arc heating has come to be used to heat molten metals, such as molten steel. Plasma arc heating equipment is basically connected to the negative side of a power supply and creates a current conduction path between the plasma torch (cathode) that generates a plasma arc between the molten metal and the positive side of the power supply and the molten metal. It is equipped with a power supply electrode (anode) for forming the electrode.

However, conventional anodes are used in fixed furnaces such as melting furnaces, where a carbon brick (conductive) is attached to the bottom of the furnace and a lead wire is connected to this to form a current path. A method was adopted in which a part of the furnace was made of the same metal as the molten metal to be heated instead of bricks, and this was brought out from the bottom of the furnace, and a lead wire was connected to it to form a current path.

However, both of the above formulas have the following problems.

That is, in the well-known continuous casting tundish, the main body has to be replaced more frequently than in the above-mentioned fixed furnace, and the bricks have to be reloaded more frequently, and the anode needs to be replaced each time, which increases running costs. At the same time, it complicates all operations such as changing and stacking tanditsh. For this reason, it is more advantageous to use an anode of the type that is immersed above the molten metal in the case of a tundish.

However, with the top immersion type anode, it is impossible to supply power from directly below the plasma arc as with the bottom electrode, and as shown in Figure 1, the effect of the magnetic field formed by the current flowing through the anode 1. , the plasma arc 2 is deflected away from the anode 1. In the figure, 3 is a plasma torch, 4 is a molten metal,
5 indicates an electrical disconnection, and 6 indicates a cable line.

Normally, when heating molten metal with a plasma arc, in order to prevent contamination of the molten metal by controlling the atmosphere and to effectively utilize the radiant energy of the plasma arc,
The plasma arc is generated in a closed chamber (heating chamber), but due to the deflection of the plasma arc, a part of the inner wall of the heating chamber is directly exposed to high temperatures with an average temperature of 3000° or more.

As a result, a problem arises in that the refractories on the walls of the heating chamber fall off and contaminate the molten metal.

Purpose, Structure, and Function of the Invention The present invention has been made in order to eliminate the drawbacks of the above-mentioned upper immersion type one-field electrode. The above-mentioned upper immersion type anode is configured and arranged so that the sum of the forces exerted on the plasma arc by the magnetic field created by the current flowing through each anode is substantially zero in the section up to the molten metal below. It is characterized by preventing deflection of the plasma arc.

First, a concept for reducing the sum of the forces exerted on the plasma arc by the magnetic field created by the currents conducted to the plurality of anodes in the present invention will be described.

N anodes al+a'! +...+ IIN and considering a plane parallel to the molten metal surface, the position vectors on the plane of these anodes with the origin directly below the torch as vil-r,, r2
゜..., rN, the current conducted to its anode is il ・i
2..., iN. If the force f exerted on the arc by the current flowing through the anode aK is taken to be positive on the repulsive force side, it can be expressed as in the following equation.

Here α is a proportionality constant. Therefore, the sum of the forces due to N anodes is zero, which means that the following equation holds true. Here, Σ is considered to be NO, and α is essentially the same, so N anodes cause plasma arc In order to make the sum of the forces applied to zero, the following equation must hold.

Therefore, by setting the position rK of the first field pole aK or the current iK flowing through aK so as to satisfy equation (3), the plasma
Arc deflection can be prevented.

EXAMPLES The present invention will be explained in detail with reference to examples shown in FIGS. 2 to 4.

In FIG. 2 showing one embodiment of the present invention, 7 indicates a shield tank, and 8 indicates molten steel stored therein. Reference numeral 9 denotes a lid of the tandy tour, and a heating chamber 1o is provided in a part of the lid 9, the lower end of which is immersed in molten steel.

Reference numeral 11 indicates a plasma torch for generating a plasma arc provided on the ceiling of the heating chamber 1o, and reference numerals 12 and 13 indicate an upper immersion type anode. In this example, since the two anodes are arranged point-symmetrically with respect to the torch, the conditions for obtaining an undeflected plasma arc are as follows: where the current flowing through the anodes 12 and 13 is its l Ill, respectively. II
It is to be S. Since the electric resistance of the cable 16 and the molten steel 8 is virtually zero, the factor that determines the ratio of the current shunted to the anode 12.13 is the resistance of the anode 12.13 itself, and in this example, even if the resistance is the same. Therefore, the anodes 12 and 13 may be made of the same material and have the same size.

FIG. 3 shows another embodiment of the present invention, which is the same as FIG. 2 except for the anode. In the example in the figure, when the two anodes and the torch are viewed from above, they are on a - straight line, but the torch and the anode 1
9 and the distance rzo between the torch and the anode 20 are different due to the arrangement of the equipment, r! 9: r2゜=10α:
It is 1. At this time, the conditions for obtaining a plasma arc without direction (2) are as follows from equation (3), assuming that the currents flowing through the anodes 19 and 20 are $111 + $20, respectively. The ratio will be 2:1. 2
In order to divide the current into two anodes at this ratio, anode 19.
20 resistors R1G r R2 respectively.

Then, R19: R20=1: (1+α)2.

One way to achieve this is to use a homogeneous cylindrical anode and set the diameter of the anode 19.20 to DlG.
+0110, Dzo: Dzo = 1
An anode satisfying +α21 can be used.

FIG. 4 shows yet another embodiment. This figure is a top view of the apparatus for molten metal, 25 is a container, 26 is molten metal, 2
1 is a plasma torch, 22, 23 and 24 are anodes. In this example, it is assumed that three anodes are located at arbitrary positions with respect to the plasma torch. Current flowing through the anodes 22, 23.24 $22 r z*s l
124, the force that each exerts on the plasma arc is fx
z (i2z) I f23 (j2s)+f24
(tz4), then by equation (3) fat C62z
) ten fzs (jzs) ten, fa4 (iz4) = 0
By adjusting the current flowing through each anode to satisfy
A plasma arc without deflection is obtained. To achieve this, the resistance value of each anode can be adjusted by changing the material, cross-sectional area, etc. of each anode.

In this way, the power supply electrode (anode)' (+: configuration/
Arranging means to appropriately combine the following methods: adjusting the installation position of multiple anodes, adjusting the cross-sectional area of the anode energization path for each anode, and adjusting the anode material for each anode. do.

Effects of the Invention As explained in detail above, according to the present invention, the deflection of the plasma arc, which was a drawback of the top immersion type anode, is eliminated, and a top immersion type anode with excellent operability and maintainability is provided. It can be used without any problems and can perform plasma arc heating with low running costs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the deflection phenomenon of the plasma arc that occurs when one upper immersion type positive 40 is used. FIGS. 2, 3, and 4 are illustrations showing embodiments of the present invention It is a diagram. l... Anode 2... Plasma arc 3... Plasma torch 4... Molten metal 5... Power source 6...
・Cable line 7... Shield tundish 8... Molten steel 9...Tandish lid 10...
Heating chamber 11...Plasma torch 12.13...
Anode 14...Plasma arc 15...Power supply 1
6... Cable line 17... Immersion nozzle 18...
Long nozzle 19.20... Anode 21...]0 Lasma torch 22.23.24... Anode 25... Container 26... Molten steel 45

Claims (1)

[Claims] By immersing multiple power supply electrodes above the molten metal in the container, a conduction path between the molten metal and the positive side of the power source is constructed,
In the apparatus for heating the molten metal by a plasma arc generated between the molten metal and a plasma torch connected to the negative side of the power supply, the current flowing through the plurality of power supply electrodes to each of the power supply electrodes. A device for heating molten metal using a plasma arc, which is characterized by being constructed and arranged so that the magnetic field formed by the plasma arc does not reach the plasma arc, and the sum of the forces becomes substantially zero immediately below the plasma torch.