JP2861052B2 - Transfer type plasma torch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a transfer type plasma torch that generates a plasma jet and is used for heating, melting, reaction, and the like.

Thermal plasma is widely applied to reactions and surface treatments, including heating and melting, as an ultra-high temperature and high energy source.
In particular, since the energy density is high, the equipment is compact, the atmosphere can be freely controlled by the plasma working gas, and the input power can be freely and responsively adjusted by controlling the current and the plasma length.
Taking advantage of these features, in recent steelmaking processes,
Heating molten steel in a ladle or tundish with plasma to control the temperature of the molten steel or perform a smelting reaction is being studied. In these applications, a transfer-type plasma torch having a heating object as a counter electrode is used in terms of heating efficiency.

[Prior Art] In the conventional transfer type plasma torch, from the viewpoint of directivity and stability, the flow rate of the plasma working gas in the axial direction of the torch is increased to form a stable linear plasma jet. .

On the other hand, the applicant has previously filed an application for an invention of a transfer type plasma torch in which the generated voltage is increased, the heating area is increased, and the ease of maintenance is improved as Japanese Patent Application No. 1-28735. According to the transfer type plasma torch of the invention of Japanese Patent Application No. 1-28735,
The plasma jet is swirled at a high speed to form a plasma spread toward the object to be heated. The proposed plasma torch uses a thermionic emission type cathode as the electrode and fixes the cathode spot to suppress the axial velocity of the plasma jet to such an extent that the magnetic instability of the plasma jet occurs. . For this reason, the tip of the electrode is rounded without being sharpened to suppress the jet flow, or the axial velocity of the plasma jet is reduced by positively flowing the plasma working gas as a swirling flow between the nozzle and the electrode doing.

[Problem to be Solved by the Invention] The improved transfer type plasma torch according to the prior invention is
Utilizing the inherent magnetic instability of plasma,
The plasma jet is fluidly unstable, is rotated at high speed, and is ejected radially from the electrode of the plasma torch. For this reason, the above-mentioned state is formed by suppressing the axial flow velocity of the plasma working gas ejected from the nozzle and flowing between the nozzle and the electrode.

However, if the plasma working gas is supplied in a swirling flow while the axial flow velocity is suppressed, the surrounding atmospheric gas is involved. When a plasma jet swirling in the atmosphere is generated, there is a problem in that oxygen is entrained in the plasma jet, causing oxidation and depletion of the electrode, and the life of the electrode is extremely shortened.

The present invention has been made in order to solve the above-described problems, and has an object to realize a transfer-type plasma torch capable of suppressing oxidative consumption of an electrode and forming a swirling plasma jet. It is assumed that.

[Means for Solving the Problems] In the present invention, two gas flows are combined: a gas flow for suppressing oxidation consumption by sealing the cathode and a gas flow for rotating the plasma jet at high speed.

For this reason, the seal gas flows axially around the electrode,
For example, a transfer type plasma torch provided with a supply nozzle for a plasma working gas containing a radial flow component on the outside thereof.

[Operation] A seal gas flows in the axial direction around the electrode, and a plasma working gas containing a radial flow component is blown out of the supply nozzle outside the seal gas. As a result, while the electrode is surrounded and sealed by the gas curtain of the sealing gas, the plasma working gas blown out from the outer supply nozzle forms a plasma jet which is swirled at a high speed such that the turning radius is enlarged as the electrode is separated from the electrode. Is done.

[Embodiment of the Invention] FIG. 1 is an explanatory view of the configuration of an embodiment of the present invention, and FIG. 2 is an explanatory view of its operation.

In FIG. 1, (1) is a plasma torch, (2) is an electrode (cathode), and (3) is a sealing nozzle. The material of the electrode (2) was pointed using tungsten, which is one of thermionic emission electrodes. The nozzle (3) surrounding the electrode (2) is often made of water-cooled copper or ceramic, and is formed in a substantially straight tube without particularly narrowing the tip. (4) is a plasma working gas such as argon or hydrogen, which is ejected at a rate of about 20 l / min from between the electrode (2) and the nozzle (3). The plasma working gas (4) is not swirled or disturbed by obstacles and flows in the axial direction of the plasma torch (1). (5) is an object to be heated, (6) is a plasma jet to be formed, (7) is an insulating spacer,
(8) is cooling water, and (9) is an electric terminal. The configuration up to this point is almost the same as the conventional device. In addition to the above, particularly in the present invention, another swirling nozzle (10) is attached near the tip of the nozzle (3). The outer nozzle (10) is formed in an annular shape, and the jet outlet is inclined inward in the circumferential direction downward, and the jet flows intersect at a position slightly away from the electrode (2). Then, a plasma working gas (4) containing a radial flow component is blown out from the nozzle (10). FIG. 2 (5) shows an object to be heated (anode).

In the present invention having such a configuration, a plasma jet (6) is generated between the tip of the electrode (2) and the object (5) to be heated, but when the nozzle (10) is closed, the plasma working gas is generated. By (4), a stable linear plasma jet (6) having strong axial directivity is formed near the electrode (2) (see FIG. 2 (a)).

However, a plasma working gas (4) containing a radial flow component is blown out of the outer nozzle (10). Therefore, the flow of the swirling gas blown out from the nozzle (10) hits the plasma jet (6) in the vicinity of the intersection position, which promotes its magnetic instability. As a result, a swirling flow is generated from this vicinity in a direction of rotation about the axis of the plasma jet (6), and swirling plasma is formed. The state at this time is shown in FIG. That is, a plasma jet (6) is generated near the electrode (2) in a column shape surrounding the electrode, and the turning radius increases as the distance from the electrode (2) increases.

In this way, by flowing the plasma working gas (4) around the electrode (2) from the nozzle (3), a cylindrical gas curtain is formed, and the electrode (2) is shielded from the swirling plasma jet (6). Is done. Therefore, even if the plasma jet (6) swirling entrains oxygen in the atmosphere, the electrode (2) is not oxidized and its consumption can be suppressed.

FIG. 3 and FIG. 4 are explanatory diagrams of the configuration of another embodiment of the present invention.

In FIG. 3, a nozzle (11) for generating plasma turbulence is constituted by one or a plurality of simple tubes whose tips are bent in the radial direction instead of the annular nozzle (10) shown in FIG. Things.

In the embodiment shown in FIG. 4, a coil (13) is attached to the outside of the tip of the nozzle (3).
A DC power supply (14) for exciting the power supply is provided. When the coil (13) is excited by the exciting current of the DC power supply (14), a DC magnetic field is formed below the nozzle (3).
Therefore, the formed magnetic flux of the DC magnetic field interlinks with the current flowing through the plasma jet (6) as shown in FIG. 2 (A). As a result, the magnetic instability of the plasma jet (6) is promoted, and a plasma jet (6) that rotates at a high speed as shown in FIG. even here,
The electrode (2) is shielded by the plasma working gas (4) blown in the axial direction from the nozzle (3), and the oxidative consumption of the electrode (2) is suppressed. In this embodiment, if necessary, a ring-shaped magnetic shield can be provided around the electrode (2). By providing a magnetic shield, the electrode (2) can be shielded from the DC magnetic field and isolated from the swirling plasma jet (6).

In the embodiment of FIG. 5 described above, the case where the coil is wound around the nozzle is described. However, the nozzle may be incorporated in the main body, and the position and shape of the coil are not limited to each embodiment. .

[Effects of the Invention] As described above, according to the present invention, a plasma jet swirling below the electrode (cathode) while being sealed from the atmospheric gas by the inert gas blown in the axial direction near the electrode (cathode). Is formed. As a result, it is possible to reduce the oxidative consumption of the electrode despite the large generated voltage and the increase of the heating area as in the conventional plasma torch.

Therefore, according to the present invention, it is possible to realize a transfer-type plasma torch having features such as easy maintenance and a large heating area, and suitable for a heating source for controlling the temperature of molten steel.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the configuration of an embodiment of the present invention, FIG. 2 is an explanatory view of its operation, and FIGS. 3 and 4 are explanatory views of the configuration of another embodiment of the present invention. In the figure, (1) is a plasma torch, (2) is an electrode,
(3) a nozzle, (4) a plasma working gas, (5) an object to be heated, (6) a plasma jet, (7) an insulating spacer, (8) cooling water, (9) an electric terminal, (Ten)
Is an annular swirling nozzle, (11) is a tube swiveling nozzle, (13) is a coil, and (14) is a DC power supply.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-128499 (JP, A) JP-A-63-30180 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05H 1 / 32,1 / 40 B23K 10/00

Claims (1)

(57) [Claims] 1. A transfer type plasma torch for generating a plasma jet between an object to be heated and an electrode provided at a central portion of the plasma torch, wherein a plasma working gas provided around the electrode is axially moved. A nozzle for flowing to seal the surface of the electrode from the atmospheric gas, and a plasma provided outside the nozzle and formed at a position distant from the electrode to form a plasma jet which promotes magnetic instability of the plasma and rotates at high speed. A transfer type plasma torch characterized by comprising a jet forming means.