JPH088094A - Electrode for generating plasma arc - Google Patents

Abstract

PURPOSE:To provide an inexpensive plasma-arc-generating electrode which extends life and is stable. CONSTITUTION:This plasma-arc-generating electrode has an electrode base 11 having a holed portion 13 of a circular cross section open to the outside of its end portion, and has an inserted electrode 12 of a circular cross section which is tightly fitted in place inside the holed portion 13 of the electrode base 11. The inserted electrode 12 has a recessed portion 15 which is located at the center of an exposed end face 14 and recesses in the direction of the axis of the inserted electrode 12. The recessed portion 15 creates a space of a circular cross section perpendicular to the axis and has a diameter 50 to 90% of that of the inserted electrode 12 and a depth of 0.3mm or more along its axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode base having a hole having a circular cross section which is open to the outside of the tip end, and a circular cross section which is tightly fitted and fixed in the hole of the electrode base. And an electrode for generating a plasma arc comprising an electrode.

[0002]

2. Description of the Related Art As is well known, a plasma cutting apparatus cuts a work by generating an arc between an electrode provided on a nozzle and a work and turning a working gas ejected from the nozzle into a plasma. It is a thing. As shown in FIG. 4, an electrode substrate 1 made of copper or a copper alloy is used as an electrode used in this plasma cutting device, that is, an electrode for generating a plasma arc used in an oxidizing atmosphere gas such as oxygen gas or air. The insertion electrode 3 formed of hafnium or zirconium in the shape of a rod having a circular cross-section is insert-molded into the hole 2 having a circular cross-section that is open toward the outside of the tip, and the tips of these hafnium and zirconium are exposed to the outside. The thing of a structure is general. As shown in FIG. 5, this electrode for plasma arc generation has a processing head body 4 of a plasma cutting device in which the insertion electrode 3 is arranged toward the tip opening 5 of the processing head body 4, When the working gas is supplied to the inside of the processing head body 4 through the working gas passage 6 formed outside the plasma arc generating electrode of the body 4, the tip portion of the insertion electrode 3 is wrapped in the working gas. By generating an arc in the state,
The working gas is turned into plasma. The electrode for plasma arc generation has a structure in which the insertion electrode 3 is melted and damaged as it is used, and the state shown in FIG. 6 is reached as the melting and damage progresses.

[0003]

The plasma arc generating electrode, however, has the following problems due to the melting damage of the electrode base 1 as a result of the melting damage of the insertion electrode 3. That is, as a result of the erosion of the insertion electrode 3, the plasma flow P enters the erosion inside of the insertion electrode 3, and in some cases, the exposed portion of the inner peripheral surface of the hole 2 of the electrode base 1 as shown in FIG. A plasma flow P is generated directly from the electrode base 1, and the plasma energy causes the electrode substrate 1 to melt. When the plasma flow P is generated directly from the electrode substrate 1, the plasma flow P is unevenly distributed, so that the machining accuracy of the work is deteriorated. Although the progress of the melting loss of the insertion electrode 3 and the progress of the melting loss of the electrode substrate 1 are not uniform and generally vary, the variation in the progress of the melting loss disturbs the flow of the working gas to form plasma turbulence. However, the work efficiency and the work accuracy of the work are deteriorated. The variation of the progress of the melting loss has a great influence on the life of the plasma arc generating electrode if the portion where the progress of the melting loss progresses is completely melted, and as a result, the life of the plasma arc generating electrode is shortened. At the same time, the life of the plasma arc generation electrode is generally unstable because the part where the melting loss progresses is uncertain, and the processing is interrupted and the plasma arc generation electrode must be replaced. A case has occurred, which has been a cause of reduced retention of product. Further, if the inner peripheral surface of the electrode base 1 is exposed due to the progress of the melting damage of the insertion electrode 3, the cooling effect of the electrode base 1 on the insertion electrode 3 is lost by the heat input to the electrode base 1, and the melting damage of the insertion electrode 3 is lost. When the amount of heat input exceeds the critical state, the electrode base body 1 melts at once and the life of the plasma arc generating electrode is shortened.

In view of the above problem, as shown in FIG. 4, a technique is known in which a conical recess 7 having a depth of about 0.05 mm is provided on the distal end surface of the insertion electrode 3, but this technique uses plasma. It is a means that contributes to stabilization of the plasma flow P and uniform melting loss of the insertion electrode 3 only in the initial state of use of the arc generating electrode, and is effective in terms of protection of the electrode base 1 and stability of melting loss. I was dissatisfied.

On the other hand, as a technique for protecting the inner peripheral surface of the electrode base 1 against the melt damage of the insertion electrode 3 to stabilize and extend the life of the electrode for generating plasma arc, a technique between the electrode base 1 and the insertion electrode 3 is used. A technique of interposing a third substance is also proposed. This technique uses a material having excellent thermal conductivity and electrical conductivity such as a gold alloy, a silver alloy, and an aluminum alloy as the third substance, and uses the third member as a cylindrical member to form the hole portion. Although it is inserted into the electrode 2 or is diffusion-bonded to the electrode substrate 1, there is a problem that the material is expensive and the work is troublesome, which causes an increase in cost and a decrease in manufacturing efficiency.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an inexpensive plasma arc generating electrode having an extended life and stability.

[0007]

According to a first aspect of the present invention, there is provided an electrode base having a hole having a circular cross section, which is open toward the outer end of the tip, and the electrode base is tightly fitted and fixed in the hole. The insertion electrode having a circular cross-section is formed, and a concave portion that is located in the center of the tip surface exposed to the outside of the insertion electrode and is recessed in the axial direction of the insertion electrode is formed. In the plasma arc generating electrode that is consumed so that the recess becomes deeper in the axial direction, the recess has a circular cross section in a direction orthogonal to the axis, and the diameter thereof is the diameter of the insertion electrode. 50-95% of
The electrode for plasma arc generation characterized in that

According to a second aspect of the present invention, the plasma arc generating electrode according to the first aspect is characterized in that the recess has a depth of 0.3 mm or more in the axial direction. .

[0009]

According to the plasma arc generating electrode of the first aspect, when the plasma arc generating electrode is used, the insertion electrode is melted and damaged in the axial direction while leaving the outer peripheral portion thereof.

According to the plasma arc generating electrode of the second aspect, even in the state in which the melting loss of the insertion electrode progresses,
The insertion electrode can be stably melted inward in the axial direction while leaving the outer peripheral portion thereof.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 10 in the drawing is a plasma arc generating electrode of the present invention, 11 is an electrode substrate, and 12 is an insertion electrode.

The plasma arc generating electrode 10 is arranged in the processing head body 4 shown in FIG. 5, and has an electrode base 11 having a hole 13 having a circular cross section which is open toward the outer end of the tip. And the hole 1 of the electrode substrate 11
3, and an insertion electrode 12 having a circular cross section which is tightly fitted and fixed. The electrode base body 11 is made of copper or a copper alloy, and is arranged in the processing head body 4 with the hole portion 13 being directed toward the opening 5 of the processing head body 4. The insertion electrode 12 is a member made of hafnium or zirconium and has a tip surface 14 exposed to the outside.
A recess 15 is formed at the center of the insertion electrode 12 and is recessed in the axial direction of the insertion electrode 12. By using the insertion electrode 12, the recess 15 is consumed so as to become deep in the axial direction. The recess 15 has a circular cross section in a direction orthogonal to the axis, has a diameter of 50 to 95% of the diameter of the insertion electrode 12, and has a depth X of 0.3 mm or more in the axis direction. It is a hole and is formed coaxially with the electrode base 11. Further, the diameter dimension Y of the recess 15 is, for example, 250 A of working current, the insertion electrode 12
When the diameter φ is 2.0 mm, it is set to 1.0 to 1.9 mm.

When the plasma arc generating electrode 10 is used for plasma cutting or the like, as shown in FIG. 1, the plasma flow P is stably held in a normal position by the action of the recess 15, and the plasma flow P is maintained. While holding the
The melting loss of the insertion electrode 12 progresses from 5 toward the inner side of the insertion electrode 12 in the axial direction. As the erosion progresses, the insertion electrode 12 eventually becomes a cylindrical shape, leaving only the outer peripheral portion of the insertion electrode 12, as shown in FIG. At this time, the insertion electrode 12 does not expose the electrode base 11 and the hole portion 1 of the electrode base 11 is not exposed.
Since the entire inner peripheral surface of 3 is covered, the plasma flow P is not directly generated from the electrode base 11, and the plasma flow P is stably maintained even when the melting loss progresses considerably.

Therefore, in the plasma arc generating electrode 10 of the present invention, the plasma flow P is always maintained stably even when the insertion electrode 12 is melted and damaged, so that the machining accuracy and the machining efficiency of the work are improved. Further, since the plasma flow P is constantly generated, local melting loss and wear of the insertion electrode 12 are prevented, and for example, as shown in FIG. 3, the wear depth of the insertion electrode with respect to the number of arc occurrences under the same conditions. When the results of the experiments are compared, it can be seen that the life is greatly extended as compared with the conventional plasma arc generating electrode.

Further, since the plasma flow P is stabilized and the life of the plasma arc generating electrode 10 is stabilized, the replacement time of the plasma arc generating electrode 10 can be predicted, and the work of the workpiece can be efficiently performed. be able to. The plasma arc generating electrode 10 does not require the interposition of the third substance between the electrode base 11 and the insertion electrode 12, and the recess 15 can be easily formed, so that the cost can be reduced. can get.

The shape of the concave portion 15 is not limited to the above-mentioned shape, but may be a tapered shape in whole or in part, or a conical shape.

[0017]

As described above, according to the plasma arc generating electrode of the present invention, when the insertion electrode is melted, only the outer peripheral part of the electrode is left and only the central part is melted, and the insertion electrode remains. Since the exposed portion covers the entire inner peripheral surface of the electrode base without exposing the electrode base, the plasma flow is not directly generated from the electrode base, and the plasma flow is stably maintained even when the melting loss progresses considerably. In addition, the machining accuracy and the machining efficiency of the work are improved, and the plasma flow is stabilized, so that the life of the plasma arc generation electrode is extended and stabilized, and the stabilization of this life allows the replacement time of the plasma arc generation electrode. It can be predicted and the work of the workpiece can be efficiently performed.

According to the plasma arc generating electrode of the second aspect, even in the state where the insertion electrode is melted and damaged,
The insertion electrode remains stable at the axial depth while leaving the outer periphery of the insertion electrode, and the plasma flow is stably maintained, resulting in an even longer life and stabilization of the electrode replacement period. Play.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an electrode of the present invention.

FIG. 2 is a side sectional view showing a plasma generation state when the insertion electrode melts in the electrode of FIG.

FIG. 3 shows a conventional insertion electrode and an insertion electrode of the present invention,
It is a graph which shows the relationship of the consumption depth with respect to the frequency | count of arc generation on the same conditions.

FIG. 4 is a side sectional view showing a conventional electrode.

FIG. 5 is a side sectional view showing a processing head body.

FIG. 6 is a side sectional view showing melting damage of an insertion electrode of a conventional electrode.

[Explanation of symbols]

 10 Electrode 11 Electrode Base 12 Insertion Electrode 13 Hole 14 Tip Surface 15 Recess

Claims (2)

[Claims] 1. An electrode base having a hole having a circular cross section that is open toward the outside of the tip, and an insertion electrode having a circular cross section that is closely fitted and fixed in the hole of the electrode base. , A concave portion is formed on the tip end surface exposed to the outside of the insertion electrode, the concave portion being located at the center of the insertion electrode and recessed in the axial direction of the insertion electrode. In the plasma arc generating electrode described above, the concave portion is a space having a circular cross section in a direction orthogonal to the axis, and the diameter thereof is 50 to 95% of the diameter of the insertion electrode. Electrode for plasma arc generation. 2. The electrode for plasma arc generation according to claim 1, wherein the recess has a depth of 0.3 mm or more in the axial direction.