JP2001232475A - Electrode for plasma torch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To predict the destruction of an electrode attached and detached to a plasma torch when a plasma arc is ejected toward material to be cut to cut it. SOLUTION: The electrode A is composed by embedding electrode material 2 from the tip end surface 1a of an electrode material holder 1. The electrode material 2 is made of metal such as hafnium, and a discontinuous part 5 is formed in a prescribed position in the depth direction from the tip end surface 1a. The electrode material 2 is joined to the electrode material holder 1 by brazing. When the consumption of the electrode material 2 reaches the discontinuous part 5, the behavior of the plasma arc (voltage applied to the electrode A in order to form the plasma arc, sound and light of the plasma arc) is changed. An electrode destruction predicting signal is obtained by detecting the change of the behavior. The discontinuous part 5 is composed by connecting electrode materials 2a, 2b consisting of different material, is also composed by forming a notch 2d in the outer periphery and further may be composed by the other structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a plasma torch capable of predicting that the electrode will be broken.

[0002]

2. Description of the Related Art A so-called cutting of a steel sheet by injecting a plasma arc from a plasma torch toward a steel sheet to melt the base material and continuously moving the plasma torch while excluding the molten base material. Plasma cutting has been put to practical use. In such a plasma cutting, the cutting speed can be increased as compared with the gas cutting, so that the cutting length per unit time can be increased, which is advantageous in reducing labor costs.

In performing the above-mentioned plasma cutting, in order to inject a plasma arc from a plasma torch, an oxygen gas is supplied around an electrode attached to the plasma torch, and a discharge is caused between the electrode and a nozzle. By forming an arc and continuing the supply of oxygen gas, a pilot arc is blown out from the nozzle toward the steel sheet, and further, when the pilot arc comes into contact with the steel sheet, a discharge is caused between the steel sheet and the electrode to form a main arc. At the same time as (plasma arc) formation, the discharge between the electrode and the nozzle is stopped to stop the pilot arc.

As described above, the electrodes of the plasma torch used for cutting are exposed to an oxidizing atmosphere of high-purity oxygen gas.
In addition, since the high temperature of the plasma arc acts, the conditions of use are very severe, and electrodes formed of metals such as tungsten and copper are instantaneously melted and cannot be used.
For this reason, recently, hafnium or zirconium is embedded as an electrode material in an electrode material holder made of copper or a copper alloy, and aluminum, gold, a gold alloy, silver, silver alloy, or the like is provided between the electrode material and the electrode material holder. A structure in which a selected metal is interposed is used.

[0005] Even if the electrode for the plasma torch is not consumed at all, the surface of the electrode material is melted and oxidized each time a plasma arc is formed, thereby causing minute consumption of the electrode material. The depth of the electrode material from the tip surface of the electrode is increased. When the consumption of the electrode material progresses and reaches the limit, the electrode material holder is melted down and the plasma arc stops at once, and the cutting work currently in progress is interrupted, and at this time, a notch is formed on the cut surface. The product may be hindered.

[0006]

As described above, when the electrode is broken during the cutting, problems such as damage to the product and interruption of the work arise. For this reason, it is preferable to configure so that destruction can be predicted before the electrode is destroyed.

An object of the present invention is to provide an electrode for a plasma torch capable of predicting breakdown.

[0008]

In order to solve the above-mentioned problems, an electrode for a plasma torch according to the present invention is detachably attached to a mounting portion of a plasma torch, and converts a gas supplied around a tip surface into a plasma. An electrode for a plasma torch to be formed, wherein an electrode material is buried in a center of an electrode material holder and a discontinuous portion is formed at a predetermined position in a depth direction of the electrode material.

In the above-mentioned electrode for a plasma torch (hereinafter simply referred to as an "electrode"), the discontinuous portion formed in the electrode material causes the behavior of the plasma arc when the consumption of the electrode material reaches the discontinuous portion. Is preferably changed. In the electrode configured as described above, the consumption of the electrode material progressed with an increase in the use time, and when the consumption reached a discontinuous portion formed at a predetermined position in the depth direction, the formation of the plasma arc was maintained. In this state, the behavior of the plasma arc changes according to the nature of the discontinuous portion.

Therefore, by detecting the change in the behavior of the plasma arc, it is possible to recognize that the electrode has reached the discontinuous portion. Therefore, by setting the position of the discontinuous portion on the tip side from the position where the electrode breaks, when the change in the behavior is detected, it is recognized that the currently normally functioning electrode will be broken in the near future. It becomes possible. That is, the electrodes can be replaced at an appropriate timing, and the operation can be performed in a good management state without damaging the product and without abrupt interruption of operation. Here, the change in the behavior of the plasma arc refers to the change in the voltage applied to the electrode to form the plasma arc that occurs at the discontinuous portion of the electrode material, or the sound during the formation of the plasma arc. Changes, or changes in the plasma arc light.

In the above electrode, it is preferable that the discontinuous portion is formed by a change in the cross-sectional area of the electrode material or a change in the material of the electrode material. By configuring the electrode in this way, it is possible to predict the destruction of the electrode by a sudden change in the voltage, or by changing the sound of the electrode material or the light of the plasma arc in addition to the voltage change. Destruction of the electrode can be predicted.

In the above electrode, it is preferable to change the timing until the behavior of the plasma arc changes by changing the position of the discontinuous portion formed in the electrode material. When the electrode is configured in this manner, when a new electrode is used, the timing until the wear reaches the discontinuous portion (the time during which a plasma arc can be formed, the number of times the plasma arc is formed, etc.) can be adjusted. It is possible to use differently according to the case where long-time continuous cutting is performed when cutting large members and the case where short-time cutting is performed when cutting small members. I can do it. For this reason, the remaining portion of the electrode material can be used rationally with a minimum.

In the above-mentioned electrode, it is preferable that the electrode material is joined to the electrode material holder by brazing. By configuring the electrode in this manner, the molten solder flows into the discontinuous portion of the electrode material without losing the conductivity or thermal conductivity, and even if the discontinuous portion exists in the electrode material. Regardless, the cutting performance can be exhibited in a normal state of the electrode.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the above-mentioned electrode will be described below with reference to the drawings. FIG. 1 is a sectional view illustrating the configuration of the electrode according to the first embodiment. FIG. 2 is a view for explaining the process of growing electrode wear. FIG. 3 is a diagram illustrating the configuration of the tip portion of the plasma torch. FIG. 4 is a sectional view illustrating the configuration of the electrode according to the second embodiment.

The electrodes A and B according to the respective embodiments maintain the cutting performance when the time for forming the plasma arc is increased, that is, when the wear reaches the discontinuous part with the increase in the use time, the electrodes A and B maintain the cutting performance. During the operation, a state different from the steady progress of the work (change in the behavior of the plasma arc) is forcibly made to appear, and by detecting this state, it is possible to predict the destruction of the electrode. Things.

The state different from the above-mentioned steady progress of the work is, for example, the electrodes A,
A change in the voltage applied to B, a change in the quality of the sound generated when the plasma arc is ejected, a change in the color of the flame of the plasma arc, and the like can be detected by a sensor assumed in advance.

Therefore, when the sensor detects that a state different from the steady state has been reached, it recognizes that the electrode will be destroyed in the near future, even though the cutting operation is proceeding in a normal state, and an appropriate timing By stopping the operation of the plasma torch and exchanging the electrodes, it is possible to prevent damage that may be caused to the product and abrupt stoppage of the operation, thereby making it possible to perform a favorable operation.

Prior to describing the configuration of the electrodes A and B according to the present embodiment, an example of a plasma torch for attaching these electrodes A and B and cutting a material to be cut such as a steel plate (not shown) with reference to FIG. A brief description will be given. The plasma torch shown in the drawing injects a secondary airflow and a tertiary airflow along the periphery of a plasma arc, and makes the secondary airflow and the tertiary airflow swirl in a desired direction or non-swirl (axial flow). Thus, a stable plasma arc is formed and the quality of the cut surface is improved.

However, this plasma torch is an example of a plasma torch to which the electrodes A and B according to the present embodiment can be attached, and is not limited to this configuration. That is, the electrode according to the present invention has the structure shown in FIG.
Other than the plasma torch configured to be able to inject to the tertiary airflow shown in the above, for example, even a plasma torch configured to be able to inject to the secondary airflow can be used in a preferable state.

In the figure, electrodes A and B (representatively, electrode A) are detachably mounted on a conductive electrode base 11. A cooling pipe for supplying cooling water is provided inside the electrode base 11.
The cooling water supplied from the cooling pipe 12 contacts the projection 4 and the back surface 1b of the electrode A to cool the cooling water, and then a passage 13 formed between the cooling pipe 12 and the electrode base 11 is provided. Through the passage 13 for cooling the nozzle member, and then discharged outside the plasma S.

The outer periphery of the electrode A has an insulating property and a main body 14.
A detachable centering stone 15 is arranged, and the first centering stone 15 is connected to the first
A nozzle member 16 and a second nozzle member 17 are provided. Further, a third nozzle member 18 is provided on the outer periphery of the second nozzle member 17, and is attached to the main body 14 by a cap 19.

In the plasma torch constructed as described above, the plasma chamber 20 is formed by the electrode A and the first nozzle member 16.
Are formed, a second airflow chamber 21 is formed by the first nozzle member 16 and the second nozzle member 17, and a tertiary airflow chamber 22 is formed by the second nozzle member 17 and the third nozzle member 18. A preset gas containing oxygen gas is supplied to 20 to 22 and injected from the holes of the nozzle members 16 to 18.

Accordingly, by supplying oxygen gas to the plasma chamber 20 and discharging between the electrode A and the first nozzle member 16, it is possible to form a pilot arc by the supplied oxygen gas. This pilot arc passes through the holes of the second nozzle member 17 and the third nozzle member 18 and is blown out to the outside to come into contact with a workpiece (not shown).
At this time, when a voltage is applied between the electrode A and the material to be cut to cause a discharge, a plasma arc is formed between the two, and at the same time, the energization between the electrode A and the first nozzle member 16 is stopped. The pilot arc is stopped, thereby maintaining the plasma arc formed between the electrode A and the workpiece.

With the formation of the plasma arc, an oxygen gas or another gas is supplied to the secondary airflow chambers 21 and 22 so that the secondary airflow chambers 21 and 22 are respectively supplied with the second gas.
By jetting from the holes of the nozzle member 17 and the third nozzle member 18, it is possible to jet the secondary airflow and the tertiary airflow along the plasma arc. When the plasma torch is moved in a predetermined direction while injecting the plasma arc, the secondary airflow, and the tertiary airflow toward the material to be cut, the plasma arc oxidizes the material to be cut in this moving process. It is possible to cut the material to be cut by melting and simultaneously removing the oxide and the melt from the material to be cut to form a continuous groove.

Next, the electrode A according to the first embodiment will be described with reference to FIGS. In the figure, an electrode A is configured by embedding a rod-shaped electrode material 2 made of hafnium in an electrode material holder 1 made of copper or a copper alloy, and between the electrode material holder 1 and the electrode material 2. Is gold, gold alloy, silver,
It is configured with a metal layer 3 made of a metal selected from silver alloys interposed.

The tip surface 1a of the electrode material holder 1, which is the tip surface of the electrode A, is a surface that comes into contact with the plasma gas composed of oxygen gas when forming a plasma arc, and the back surface opposite to the tip surface 1a. A projection 4 is formed on the projection 1b, and the cooling water is brought into contact with the projection 4 and the back surface 1b so that the electrode A can be cooled. The protrusions 4 have a function of increasing the contact area with the cooling water, and can improve the cooling efficiency of the electrode A. Electrode material holder 1
A screw 1c is formed at a portion opposite to the distal end surface 1a of the electrode, and the screw 1c is fastened to a screw portion formed on the electrode base 11, so that the electrode A can be mounted on the plasma torch. Have been.

The electrode material 2 is a starting point of a plasma arc, has extremely high electrical conductivity and thermal conductivity, has a high oxide evaporation temperature, and has extremely stable properties at high temperatures. Material is selected. Examples of such materials include hafnium and zirconium.
Is different depending on the specification of the electrode A, that is, the thickness that can be cut or the value of the current that flows when cutting. For example, 1.6 mm at 200 A (ampere) and 2.4 at 400 A
is set to mm.

End surface 1a of electrode material holder 1 of electrode material 2
And a discontinuous portion 5 is formed at a predetermined depth position. In the discontinuous portion 5, the electrode material 2 is formed by joining different kinds of materials and joining portions of different materials. That is, as for the electrode material 2 in the electrode A, an electrode material 2a made of, for example, hafnium is disposed on the tip end surface 1a side of the electrode material holder 1, and the electrode material 2a is connected to the back surface 1b side, for example, zirconium or tungsten. And the like.

The length of the electrode material 2a has a dimension corresponding to the position of the discontinuous portion 5 in the electrode material 2. In this embodiment, the length of the electrode material 2a is Tip surface 1
It is set to 1.5 mm from a.

The metal layer 3 has a function of integrating the electrode material 2 (2a, 2b) with the electrode material holder 1.
It is necessary to use a metal that is rich in malleability and ductility, or a metal that can exhibit high fluidity when melted, and preferably has high electrical conductivity and thermal conductivity. Examples of such metals include gold, silver, and alloys thereof. In the present embodiment, as the metal constituting the metal layer 3, a silver alloy selected from gold, gold alloy, silver, and silver alloy is used. I have.

The method of forming the metal layer 3 between the electrode material holder 1 and the electrode material 2 is closely related to the method of manufacturing the electrode A. As this manufacturing method,
The electrode material 2 is fitted in the electrode material holder 1 and a hole for forming the metal layer 3 is formed in advance, and the electrode material 2 wound with a thin metal (silver) plate is driven into the hole. There is a method of integrating, and a method of driving and integrating the electrode material 2 fitted into a silver pipe or a silver cup-shaped member.

According to these methods, it is possible to manufacture the electrode A relatively easily without applying heat to the members 1 to 3 constituting the electrode A. However, even when the dimensions of the hafnium used as the electrode material 2 and the dimensions of the silver thin plate, the pipe, the cup, and the like are within the tolerance ranges set in advance, respectively, the force at the time of the driving is changed or after the integration. The holding power may fluctuate.

For this reason, when forming the metal layer 3, it is preferable to employ a brazing method using a metal selected from the above metals as a braze. That is, by fitting the electrode material 2 into the hole formed in the electrode material holder 1 in advance and soldering with silver, the thickness of hafnium fluctuates within the tolerance range, and the thickness of the hole formed in the electrode material holder 1 is changed. Even if the gap fluctuates, the electrode A can be manufactured by integrating the electrode A with the electrode material holder 1 regardless of the fluctuation. Therefore, it is possible to manufacture the electrode A having stable quality.

In this embodiment, the electrode members 2a and 2b constituting the electrode A are joined to the electrode member holder 1 by brazing. In this way, even if a slight difference in outer diameter between the two electrode materials 2a and 2b occurs by joining the plurality of types of electrode materials 2a and 2b having different materials by brazing, this method can be used. It is possible to fill a gap that sometimes occurs between the electrode material holder 1 and achieve good bonding. In addition, both electrode materials 2a, 2
Similarly, when a gap is formed in a portion where b faces, similarly, it is possible to realize good bonding by allowing the row to flow into this gap.

Next, the consumption of the electrode A configured as described above will be described. When a plasma arc is formed by attaching to the plasma torch in the initial state shown in FIG. 2A, the surface of the electrode material 2a constituting the electrode material 2 melts while the plasma arc is formed, and the surface of the electrode material 2a is melted. The material evaporates as it oxidizes.

In particular, when stopping the plasma arc, evaporation of the electrode material 2a may be promoted. In any case, the electrode material 2a is consumed from the surface as the plasma arc formation time and the number of times of formation increase, and a curved concave (crater) 2c is formed on the surface as shown in FIG. Is done.

As shown in FIG. 3C, when the recess 2c grows and reaches the discontinuous portion 5 which is a joint with the electrode material 2a, the material changes from the electrode material 2d to the electrode material 2e. Accordingly, the voltage applied to the electrode A changes. The changed voltage does not return to the initial value, but maintains the changed value.

As described above, by forming the discontinuous portion 5 in the electrode material 2, it is possible to recognize that the consumption of the electrode material 2 reaches the discontinuous portion 5 as a voltage change. Therefore, by detecting the change in the voltage and generating a signal (electrode breakdown prediction signal), it is possible to recognize that the electrode A is destroyed in a preset time by the electrode breakdown prediction signal. . As described above, what can be recognized by the electrode breakdown prediction signal is not that the electrode A has been destroyed, but that the electrode A will be destroyed in a preset time thereafter.

Therefore, the discontinuous portion 5 of the electrode material 2 is
Is changed, the time until the electrode A is broken after the electrode material 2 is consumed to the discontinuous portion 5 can be set in a range of several minutes to several tens of minutes. When a predictive signal is generated, without stopping the work immediately, by finding a good place to stop the work and stopping and replacing the electrode A, the product being cut is not damaged and suddenly. The cutting operation can be advanced without lowering the operation rate due to the stoppage of the operation.

For this reason, the present invention can be applied to, for example, a case where a long cutting line is continuously cut at a time and a case where a short cutting line is intermittently cut at a time.
It is possible to proceed with a rational operation by associating the consumption of the electrode A with the cutting operation time.

During the formation of the plasma arc, a sound is generated from the plasma torch, and the plasma arc is colored. These sounds and colors are peculiar to each metal used as the electrode material 2, and as in the present embodiment, the electrode material 2 is made of a plurality of types of electrode materials 2a and 2b having different materials.
In this case, the electrode material 2a is consumed and the electrode material 2a is consumed.
When a plasma arc is formed from b, the generated sound and color change. For this reason, it is possible to recognize whether or not the consumption of the electrode material 2 has progressed to a certain value by providing a microphone near the plasma torch and constantly monitoring the sound of the plasma arc. . Similarly, the state of the plasma arc (brightness,
By providing a sensor for detecting the light wavelength) and constantly monitoring the color of the plasma arc, it is possible to recognize whether or not the consumption of the electrode material 2 has progressed to a certain value. When a change in the sound generated from the plasma torch or a change in the color of the plasma arc is detected, a signal (electrode destruction prediction signal) is generated, whereby the destruction of the electrode can be predicted.

Next, referring to FIG. 4, the electrode B according to the second embodiment
Will be described. In the drawing, the same portions and portions having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the figure, the electrode B has an electrode material 2 made of hafnium embedded at the center of an electrode material holder 1.
The electrode material holder 1 and the electrode material 2 are integrated via a metal layer 3. A discontinuous portion 5 is formed at a predetermined depth position in the electrode material 2 from the tip end surface 1a of the electrode material holder 1 by a notch 2d formed on the outer periphery of the electrode material 2.
The position where the notch 2d is formed depends on whether the electrode material 2 is consumed and the electrode A
Is a position before breaking, and is a position where the initial cutting performance can still be maintained.

The position of the notch 2 d in the electrode material 2 differs depending on the specification of the electrode A. However, the electrode material 2 is notch 2
It is premised that destruction will occur in a relatively short time (several minutes to several tens of minutes) after exhaustion to d, and is set in consideration of the results of experiments and the like for each electrode according to specifications. . In this embodiment, a depth of 1.5 mm from the front end surface 1a of the electrode material holder 1 is set.
A notch 2d is formed at the position of. In addition, the length of the electrode material 2 has a value sufficiently longer than the position of the notch 2d, and when the electrode material 2 is consumed beyond the notch 2d, the electrode material 2 returns to the initial thickness. I do.

In the electrode B configured as described above, when the wear grows and reaches the notch 2d, the sectional area of the electrode material 2 decreases according to the size of the notch 2d, so that the electric resistance increases and the plasma arc increases. The voltage applied to maintain the voltage increases. Therefore, by detecting a voltage increase and generating a signal, it is possible to recognize that the consumption of the electrode material 2 has reached the notch 2d.

When the consumption of the electrode material 2 further grows and exceeds the notch 2d, the cross-sectional area of the electrode material 2 returns to the initial value, whereby the voltage for forming the plasma arc is reduced. It decreases to a nearly normal value. Thus, by forming the notch 2d as a discontinuous portion in the electrode material 2, it is possible to recognize that the consumption of the electrode material 2 reaches the notch 2d as a change in voltage. Therefore, by detecting a change in the voltage and generating a signal (electrode breakdown prediction signal), the electrode B
Can be recognized as being destroyed in a preset time.

The notch 2d formed on the outer periphery of the electrode material 2
May be formed in a ring shape over the entire circumference of the electrode material 2, or may be an arc-shaped groove cut into the outer circumference. Further, the depth of the notch 2d is
Due to the change in the cross-sectional area of the electrode material 2 at the portion where d is formed,
It must be a value that can clearly recognize the voltage difference.

In each of the above embodiments, the discontinuous portion 5 formed in the electrode material 2 is formed by a joint of a plurality of electrode materials 2a and 2b having different materials as shown in the first embodiment. And the case of the notch 2d as shown in the second embodiment has been described. However, the present invention is not limited to these structures, but uses different electrode materials and changes the cross-sectional area at the joint between the two. And a structure in which the same kind of metal is used as a different member as the electrode material 2 and a metal of a different material is sandwiched between these members, and further, a member formed using the same kind of metal and formed with different thicknesses And so on.

In any case, the present invention does not limit the shape and structure of the discontinuous portion 5, and the voltage applied to the electrodes A and B when the electrode material 2 is exhausted and reaches the discontinuous portion 5. The purpose of the present invention is to provide a discontinuous portion 5 that causes changes such as changes in the sound generated from the plasma torch, changes in the color of the plasma arc, and the like.

[0050]

As described above in detail, in the electrode according to the present invention, the discontinuity is formed in the depth direction of the electrode material buried in the electrode material holder, so that the electrode material is consumed and the electrode material is consumed. When reaching the continuous portion, a signal corresponding to the configuration of the discontinuous portion can be generated. For this reason, by setting the position of the discontinuous portion to a predetermined position, that is, a position where the electrode maintains the initial performance but leads to the destruction in a short time, the destruction of the electrode can be predicted by the signal. Therefore, it is possible to prevent the product from being damaged due to the stoppage of the plasma arc due to the destruction of the electrode generated during the work, and the operation rate from being lowered due to the sudden stop of the work.

By setting the discontinuous portion formed on the electrode to a change in the cross-sectional area of the electrode material or a change in the material of the electrode material, the voltage applied to the electrode when the exhaustion of the electrode material reaches the discontinuous portion. The change in the sound generated from the plasma torch can be regarded as a change in the color of the plasma arc, and the destruction of the electrode can be easily and reliably predicted.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an electrode according to a first embodiment.

FIG. 2 is a view for explaining the relationship between the growth of the consumption of electrode material in the electrode and the discontinuous portion.

FIG. 3 is a diagram illustrating a configuration of a tip portion of a plasma torch.

FIG. 4 is a cross-sectional view illustrating a configuration of an electrode according to a second embodiment.

[Explanation of symbols]

 A, B Electrode 1 Electrode material holder 1a Tip surface 1b Back surface 2 Electrode material 2a, 2b Electrode material 2c Depression (crater) 2d Notch 3 Metal layer 4 Projection 5 Discontinuous portion 11 Electrode stand 12 Cooling pipe 13 Passage 14 Main body 15 Centering stone 16 First nozzle member 17 Second nozzle member 18 Third nozzle member 19 Cap 20 Plasma chamber 21 Secondary airflow chamber 22 Tertiary airflow chamber

Claims (5)

[Claims] 1. An electrode for a plasma torch which is detachably attached to an attachment portion of a plasma torch and converts a gas supplied around a tip surface into a plasma, wherein an electrode material is embedded in a center of an electrode material holder. An electrode for a plasma torch, wherein a discontinuous portion is formed at a predetermined position in a depth direction of the electrode material. 2. The plasma processing apparatus according to claim 1, wherein the discontinuous portion formed in the electrode material changes the behavior of the plasma arc when the consumption of the electrode material reaches the discontinuous portion. Electrode for the plasma torch. 3. The plasma torch according to claim 1, wherein the discontinuous portion is formed by a change in a sectional area of an electrode material or a change in a material of the electrode material. electrode. 4. The plasma according to claim 1, wherein the timing until the behavior of the plasma arc changes is adjusted by changing the position of the discontinuous portion formed in the electrode material. Electrode for torch. 5. The electrode for a plasma torch according to claim 1, wherein said electrode material is joined to an electrode material holder by brazing.