JPS61128499A - Shift type plasma torch - 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 the Invention] The present invention relates to a transitional plasma torch, and more particularly to an electrode structure of a plasma generating portion.

The transitional plasma torch to which the present invention is directed is used to heat an object, for example, to heat molten steel supplied from a converter to a continuous casting mold at a certain stage.

[Prior art]

For example, induction heating or heating with a plasma torch is used to heat molten steel. There are two types of plasma torches: plasma transfer type and non-plasma transfer type. The plasma transfer type uses the object to be heated as an anode and generates a discharge between the cathode of the plasma torch and the object to be heated, while the non-transfer type uses the object to be heated as an anode to generate a discharge between the cathode and the anode of the plasma torch. A discharge is caused, a process gas is supplied between the electrodes, and the gas passing between the cathode and the anode is applied to the object to be heated.

In the transition type plasma torch, N2 y Ar (preferably an inert gas) is used to isolate the electrode from the atmosphere.
However, the consumption of process gas in non-transfer type plasma torches is much higher, and due to this process gas consumption, non-transfer type plasma torches have high operating costs.

As a transition type plasma torch, for example, Japanese Patent Publication No. 56-435
No. 2 or Japanese Patent Application Laid-Open No. 58-223300 is known.

As shown in Fig. 1, the torch of Japanese Patent Publication No. 5B-4352 has an electrode (cathode) l screwed into the cooled main body 3, which flows into the inner chamber 4, at the center of the torch, and around the There is a cylindrical nozzle 2 with a water passage 5, and an electrode 1
A process gas flow path 6 is formed between the nozzle 2 and the nozzle 2 . Ignition of this device is performed by forming a pilot arc between the electrode 1 and the nozzle 2. However, since the tip of the electrode 1 in this shaped plasma torch is pointed, the heating arc concentrates on the tip, The electrode tip wears out rapidly, and the life of the electrode tip is short, especially when increasing the arc current to increase the amount of heating. In addition, with this type of torch that has a sharp electrode tip, the heating arc concentrates at the tip, but the arc may be unstable during ignition, and the main arc may come off the tip of electrode 1 or bend even if it is at the tip. The so-called "Stray Arc"
There is a problem in that the stray arc causes combustion due to the thermal energy generated therein, forming a hole in the nozzle 2 and causing the nozzle 2 to wear out. One method for solving this problem is disclosed in Japanese Patent Application Laid-open No. 58-223300. Japanese Patent Application Publication No. 5
8-223300 is shown in FIG. 1st I! I
Components with the same function are given the same reference numerals. In the one shown in FIG. 2, a high melting point conductive layer 7 of graphite or the like is provided on the outer surface of the nozzle 2 to prevent wear and tear of the nozzle 2 due to stray arcs. That is, the nozzle 2 is protected by attracting stray arcs to this high melting point conductive layer and dispersing the thermal energy generated therein. This conductive layer 7 extends beyond the tip of the outer surface of the nozzle 2 as indicated by a broken line 8.
Alternatively, it extends to the tip so that the tip of the nozzle 2 is also protected.

However, since all of the torches mentioned above have the nozzle 2 around the electrode 1, if the electrode 1 is made larger in order to increase the heating capacity, the diameter of the nozzle 2 will inevitably be made larger, and therefore the overall plasma torch size will be increased. Size 2 Weight increases,
Furthermore, it is necessary to increase the space for installation, which is uneconomical.

[Purpose of the invention]

The present invention has a structure that is fundamentally different from that of the conventional transition type plasma torch described above, thereby eliminating nozzle erosion, making the cathode have a high current capacity, and prolonging the life of the torch. The purpose is to make it as small as possible.

[Structure of the invention]

In order to achieve the above object, in the present invention, the cathode is a cylindrical body whose at least the bottom part is made of a high-melting point metal, and an ignition anode having a rod-like appearance is arranged in the hollow part of the cathode. The process gas is supplied to at least one of the cathode and the ignition anode.

According to this, since the ignition anode does not need to be particularly large, its outer diameter is small, and even if the external shape of the torch is the same as before, the shape of the cathode surrounding the ignition anode can be made larger than before. Current capacity can be increased. Furthermore, as the cathode becomes larger and the ignition anode is located in the center, the main arc no longer damages the ignition anode, and the nozzle is no longer eroded as in the past.

In a preferred embodiment of the present invention, the cathode has a substantially ring-shaped high melting point metal base material and a double cylinder having a cooling medium flow space fixed thereto. The ignition anode is a bottomed double cylinder with a hole in the center of the bottom; the ignition anode is a bottomed cylinder in which a hollow cylinder having a coolant flow space is fixed to a substantially cup-shaped high melting point metal; the cathode is a double cylinder with a bottom;

The area other than the discharge surface for the object to be treated is covered with an outer cylinder with a space provided between the outer cylinder and the cathode, and the space between the cathode and the ignition anode passing through it is used as a process gas flow path. Use as a gas passage.

According to this, the cathode and the ignition anode are each cooled inside, and the process gas passes through the inside and outside of the cathode to isolate the cathode from the inside and outside, thereby protecting the outer cylinder and the ignition anode. In addition, the process gas causes the outer cylinder side of the main arc to be squeezed inward (to the cathode side) with a thermal pinch, and the main arc separates from the outer cylinder and converges on the cathode, ensuring protection of the outer cylinder and high stability of the main arc. Ru. The inside of the main arc is squeezed outward (toward the cathode) by the process gas passing between the cathode and the ignition anode, and the main arc separates from the ignition anode and converges on the cathode, protecting the ignition anode. High stability of the main arc is ensured.

Fig. 3 shows the appearance of an embodiment of the present invention, Fig. 4 shows the bottom surface,
FIG. 5 shows a vt-vt line cross section (vertical cross section).

An ignition anode 12 corresponding to a nozzle (conventionally 2 in FIGS. 1 and 2) which serves as an anode when a pilot arc is generated is provided at the center, and a cathode 11 is provided around it.

The ignition anode 12 is a conductive bottomed cylinder with a cup-shaped high melting point metal fixed to its tip, and the outer shape of the 6 ignition anode 12, through which the cooling water 13 is passed, is approximately rod-shaped.

The cathode 11 surrounding this anode 2 has a bottom surface (Fig. 4).
When viewed from above, it has a ring shape, and when viewed from the vertical section (Figure 5), it is a conductor bottomed double cylinder with a convex blind hole and a high melting point metal fixed to the tip.
An ignition anode 12 passes through the center hole of this cathode 11. Cooling water 13 is passed inside the cathode 11 .

As shown in FIG. 5, the cathode 11 is surrounded by an outer cylinder 15 having an opening at the bottom. A process gas 14 is passed through the space between the outer cylinder 15 and the cathode 11 and the space between the cathode 11 and the ignition anode 12, and exits downward from the lower end of the torch.

At the time of ignition, a high frequency high voltage is first applied between the cathode 11 and the anode 12 to generate a discharge between them, and then a DC voltage is applied with the cathode 11 as the negative pole and the anode 12 as the positive pole to create a pilot arc. 6 Next, a DC voltage is applied with the cathode 11 as the negative pole and the object to be heated as the positive pole, a main arc is generated between them, and then the cathode 11. The application of DC voltage between the anodes 12 is stopped, and the pilot arc is extinguished.

The process gas 14o exiting downward through the space between the outer cylinder 15 and the cathode 11 shields the space between the cathode 11 and the outer cylinder 15, and causes a thermal pinch that directs the main arc from the outside to the inside. On the other hand, the cathode 11 and the ignition anode 1
The process gas 14i exiting downward through the space between the ignition anode 12 and the cathode 11 shields the ignition anode 12 and the cathode 11 and causes a thermal pinch that directs the main arc from the inside to the outside. These process gases protect the outer cylinder 15 and the ignition anode 12, and the main arc is stabilized at the lower end surface of the cathode 11 due to the above-mentioned internal and external thermal pinch. This lower end surface has a large area, so it has a large heat capacity and is less consumed by high arc currents.

〔Effect of the invention〕

As described above, according to the present invention, even if the outer shape of the torch is the same as that of the conventional torch, the shape of the cathode can be made larger than that of the conventional torch, and the arc current can be increased.

Also, nozzle erosion is eliminated.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views (longitudinal cross-sectional views) of a conventional transition type plasma torch. FIG. 3 is a front view showing the appearance of essential parts of an embodiment of the present invention, FIG. 4 is a bottom view, and FIG. 5 is a sectional view (vertical sectional view) taken along the line Vl-VI. 11: Cathode 12: Anode for ignition 13: Water flow 14. l 40.14i: Process gas flow 15: Outer cylinder Fig. 1 Fig. 2 Fig. 3 Town - Fig. 4 Fig. 5

Claims (5)

[Claims] (1) In a transitional plasma torch that is equipped with a cathode and an ignition anode, and after a trigger discharge is generated between the cathode and the ignition anode, a discharge is generated between the cathode and the object with the object to be treated as the anode. , the cathode is a cylindrical body made of a high melting point metal at least at the bottom, an ignition anode having a rod-like appearance is arranged in the hollow part of the cathode, and at least one side of the outside of the cathode or between the cathode and the ignition anode is disposed. A transition type plasma torch characterized by being configured to supply process gas to. (2) The cathode is a bottomed double cylinder with a hole in the center of the bottom, with a substantially ring-shaped high melting point metal as the bottom material and a double cylinder with a coolant flow space fixed thereto. The transitional plasma torch according to item (1). (3) The transition type plasma torch according to claim (2), wherein the ignition anode is a bottomed cylinder in which a hollow cylinder having a cooling medium flow space is fixed to a substantially cup-shaped high melting point metal. . (4) The cathode, other than the discharge surface facing the object to be treated, is covered with an outer cylinder with a space therebetween, and a process gas flow path is provided between the outer cylinder and the cathode. Transitional plasma torch. (5) The space between the cathode and the ignition anode passing through it is a process gas passageway.
) The transitional plasma torch described in section 2.