JPS62107865A - Ignition method for work plasma - Google Patents

Abstract

PURPOSE:To ignite an arc without impressing high frequency power source, to prevent the wear of an electrode and to prevent the generation of high frequency noises by forming an electric field between the main electrode and main nozzle and by injecting plasma for the cathode of the electric field. CONSTITUTION:A main electrode 2 and nozzle 3 are connected to non-transfer type plasma power source 1 and the plasma nozzle 13 for trigger of a plasma device 10 is fitted to the side wall of a nozzle holder 14. In case of the ignition the electric field for the main nozzle 3 from the main electrode 2 is formed when the power source 1 is turned on by feeding a shielding gas flow 8 and center gas flow 7. A main plasma is ignited between the main electrode 2 and main nozzle 3 when the trigger plasma is enclosed from the nozzle 13 to the main electrode 2 which is the cathode of this electric field. Consequently the ignition is stably performed without impressing the high frequency voltage, the wear of electrodes is prevented and the high frequency noise can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to plasma processing such as plasma welding, cutting, thermal spraying, etc., and particularly relates to a plasma ignition method for igniting processing plasma for the plasma processing.

[Conventional technology]

Plasma machining can be broadly divided into non-transfer plasma machining, in which gas is flowed at high speed between a non-consumable electrode and a plasma nozzle while exciting an arc discharge with high current density, and the resulting plasma flow is ejected onto the workpiece. There are three types of plasma processing: 1, transfer type plasma processing in which arc discharge is directly excited between the non-consumable electrode and the workpiece, and composite type plasma processing in which both are combined.

FIG. 5 shows the configuration of a conventional non-transfer type plasma processing apparatus, and FIG. 6 shows the configuration of conventional transfer type and combined type plasma processing apparatuses.

Non-transfer type plasma processing equipment constricts a non-consumable electrode type natural discharge arc using a plasma nozzle made of copper or the like to form a high-temperature plasma flow using the thermal pinch effect, and has the following characteristics.

■It can easily generate high temperatures that are one order of magnitude higher than natural discharge arcs.

■High concentration of heat.

■Plasma flow velocity can be controlled from subsonic to supersonic speeds.

■Plasma can be generated using gases with various components.

■Since an electric circuit is formed in the plasma torch itself, the workpiece can be either conductive or non-conductive.

Based on the above, non-transferred plasma can be used for welding and cutting conductive and non-conductive materials, and thermal spraying of high melting point materials (metals, etc.).

It is widely used in applications such as ceramics, organic materials, etc.

In this type of non-transfer type plasma device, as shown in FIG. , the cathode side is connected to the tungsten electrode (non-consumable electrode) 2 in the plasma torch 20 via the high frequency power source 4, and the welding power source 1. High frequency power source for plasma ignition 4. Tungsten electrode 2. A non-transfer type plasma generation circuit 21 consisting of a plasma nozzle 3 is formed. 9 is a high frequency bypass capacitor. Inert gas is fed into the shield camp 6 through the shield gas passage 8 as a shield gas.

Similarly, inert gas is fed into the plasma nozzle 3 through the center gas flow path 7 as a center gas. While these shielding gases and center gases were being supplied, a high frequency voltage of several thousand square meters or more was applied between the tungsten electrode 2 and the plasma nozzle 3 using the high frequency power source 4, causing spark discharge and dielectric breakdown. Afterwards, plasma power source 1 is applied to electrode 2 and nozzle 3 to ignite non-transfer type plasma.

In the transfer type and composite type plasma devices, referring to FIG. 6, the high frequency power source 4 and the plasma power source 1 first
The non-transfer type plasma is ignited between the electrode 2 and the nozzle 3, and then the transfer type plasma power supply 22 is turned on to ignite the transfer type plasma between the electrode 2 and the base material 5. Normally, the non-transfer type plasma is turned off after the transfer type plasma is ignited, but a composite type plasma is one in which the non-transfer type plasma is maintained in an ignited state even after the transfer type plasma is ignited. It is used when ensuring the stability of low-voltage plasma.

[Problem that the invention seeks to solve]

In both the non-transfer type plasma device (Fig. 5), the transfer type plasma device, or the composite type plasma device (Fig. 6) described above, plasma is applied between the electrode 2 and the nozzle 3 using the high frequency power source 4. arc

In this type of high-frequency ignition method, the high frequency (alternating current) and high discharge voltage generate large electromagnetic noise, which can cause various peripheral electronic devices, such as microcomputers built into automatic welding equipment, to malfunction. Since the components could be damaged, special measures had to be taken, such as using special noise filters on electronic equipment.

Furthermore, since the high frequency power source 4 is connected to the plasma power sources 1 and 22, there is also the problem that measuring equipment cannot be connected or disposed in the welding power source circuit, the torch, the base material, or in the vicinity thereof.

Instead of using the high-frequency power source 4, the electrode 2 is of a sliding type, and while the no-load voltage of the plasma power source 1 is applied, the electrode 2 is brought into contact with the nozzle 3 once and pulled, thereby generating an arc. Contact ignition is also considered, but in this case, the transient current that flows when contact arc occurs is large, so the electrode 2 and nozzle 3 are severely worn out and their lifespan is shortened.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma ignition method that does not cause wear and tear on non-consumable electrodes due to plasma ignition and has low electromagnetic noise.

[Means for solving problems]

In the present invention, an electric field is formed between a non-consumable electrode and a plasma nozzle, and a triggered plasma is injected toward the cathode of this electric field.

[Effect]

According to this, positive ions in the injected trigger plasma are accelerated by an electric field and collide with the cathode, thereby raising a part of the cathode to a high temperature. Plasma (main plasma: processing plasma) is generated between the consumable electrode and the plasma nozzle. Trigger plasma acts exactly as a trigger for main plasma ignition, and has a low current (10A).
・A short time (within 1 second) is sufficient.

Regarding ignition of the trigger plasma, even if it is generated using a high frequency ignition method or a contact ignition method, the trigger plasma circuit can be easily noise-shielded as a separate unit from the main plasma power supply circuit 1. Therefore, the level of electromagnetic noise generated is extremely low, and it becomes easy to connect and install electronic control equipment and measuring devices to the main plasma power supply circuit.

〔Example〕

FIG. 1 shows an apparatus configuration for carrying out one embodiment of the present invention. This device configuration is that of a non-transfer type plasma generation device.

In FIG. 1, the same or similar elements as in FIG. 5 are given the same reference numerals. The explanation of this part will be omitted here.

To explain the parts that have been changed to implement the present invention, a circular hole is made in the side wall of the nozzle holder 14 to which the main nozzle 3 is attached, and a trigger plasma nozzle (
A sub nozzle) 13 is attached and faces the side surface of the non-consumable electrode 2. A plasma device 10 that generates trigger plasma is connected to a sub-nozzle 13 and a tungsten electrode (sub-electrode) 12 therein. In this example, sub-electrode 1
2 is a cathode, and the sub nozzle 13 is an anode. The sub nozzle 13 is integrally connected to the nozzle holder 14, and also serves as an anode for the processing plasma power source 1.

In this example, shield gas is supplied to the shield gas passage 8, center gas is supplied to the center gas passage 7, and gas for trigger plasma generation (for example, inert gas) is supplied to the sub nozzle 1.
3, the non-transfer type plasma power source 1 is turned on, and an electric field directed from the main nozzle 3 toward the main electrode 2 is formed between the main electrode 1 and the main nozzle 3. That is, since the sub nozzle 13 is connected to the main nozzle 3, in other words, an electric field directed from the sub nozzle 13 toward the main electrode 2 is formed between the sub nozzle 13 and the main electrode 2.

In this state, the trigger plasma device 10 is turned on to generate trigger plasma. The generated trigger plasma moves toward the main electrode 2 at high speed because a trigger plasma generation gas (for example, an inert gas) is supplied to the sub nozzle 13. At this time, main electrode 2-
The positive ions in the trigger plasma injected into the electric field between the sub nozzles 13 are accelerated by the electric field and collide with the main electrode 2, increasing the humidity in the collision area. Ignition occurs between the electrode 2 and the main nozzle 3.

According to this plasma ignition method, there is a plasma point such as a high frequency power supply in the non-transfer type plasma generation circuit 21. Since it does not have an A mechanism and the main plasma is ignited by an external trigger,
Since electromagnetic noise and transient current fluctuations before and after ignition of the main plasma are small, and since an ignition circuit is not connected to the power source 1, current and voltage measurement equipment, etc. can be connected to the non-transfer type plasma generation circuit 21. Therefore, it is easy to connect and install automatic control equipment.

Further, according to the present invention, the trigger plasma generation circuit 18 has the ability to generate a low current trigger plasma of about 10 A at maximum, and injection for a short time of about 0.1 seconds is sufficient to ignite non-transfer type plasma. Moreover, since the gas required to generate the trigger plasma is only the plasma gas and no shielding gas is required, the sub nozzle 13 can be made ultra-small. Furthermore, a sub-electrode 12 and a sub-nozzle 13
Since the discharge gap and each shape and material can be arbitrarily set to facilitate discharge, for example, if the discharge gap is set to a minute value of about 0.1 mm, even if a high frequency power source is used to ignite the trigger plasma. However, a low level voltage (approximately 100 OV) is sufficient, and the electromagnetic noise generated is slight.

Further, since the trigger plasma for igniting the main plasma needs to be used only for a short time with a low current, wear and tear on the sub-electrode 12 and the sub-nozzle 13 can be almost ignored.

Next, a second explanation will be given regarding the ignition method of the trigger plasma device 10 and the trigger plasma generation circuit 18 shown in FIG.
This will be explained with reference to the figures and FIG.

FIG. 2 shows a triggered plasma generation circuit implementing the contact ignition method. In FIG. 2, reference numeral 11 denotes a plasma power source having DC drooping characteristics, and a sub-electrode I2 is connected to its cathode side, and a sub-nozzle 13 is connected to its anode side.
1. A trigger plasma generation circuit 18 consisting of a sub"?!i pole 12 and a sub nozzle 13 is formed.

While the 1-rigger plasma gas is being supplied into the sub nozzle 13, the plasma power source 11 is turned on, and while the no-load voltage is applied, the sub electrode 12 is connected manually, electrically, bimetally, spring-loaded, etc. The purpose is to contact and short-circuit the sub-nozzle 13 using a means to cause a short-circuit transient current to flow, and then separate the sub-electrode 12 from the sub-nozzle 13 to ignite the l-riger plasma. In the conventional contact ignition method for main plasma, there is a problem of wear and tear on the tip of the main electrode 2 due to excessive current during a short circuit, but in trigger plasma, since the current is originally low (maximum 10A), the tip of the sub electrode is worn out. is extremely minor. Moreover, even if it is slightly worn out, it is sufficient to ignite the trigger plasma, and since it is unrelated to the non-transfer type plasma generation circuit 21, it does not cause a problem in welding.

FIG. 3 is a block diagram showing a triggered plasma generation circuit 18 using a high frequency ignition method. 11 is a plasma power supply having DC drooping characteristics, and a high frequency power supply 14 is connected to the cathode side of the plasma power supply 11.
A sub-electrode 12 is connected through the anode, and a sub-nozzle 13 is connected to the anode side. Note that 15 is a high frequency bypass capacitor. Trigger plasma power supply 11. Sub-electrode 12. Sub-nozzle 13° High frequency power supply 14. High frequency bypass capacitor 1
5 forms a trigger plasma generation circuit 18.

In this circuit, a high frequency voltage is applied between a sub-electrode 12 and a sub-nozzle 13 by a high-frequency power source 14 to cause a spark discharge to cause dielectric breakdown, and then a current is supplied by a plasma power source 11 to trigger plasma. This is for ignition.

However, the discharge gap between the sub nozzle 13 and the sub electrode 12 is 0. ], it is also possible to make minute settings on the order of mm, so in that case it is sufficient that the output voltage of the high frequency power supply 14 is about the maximum value, and the level of high frequency noise generated due to this is also low. be.

Therefore, the trigger plasma generation circuit 18 is shielded by I6.
By connecting it to an external power source through the noise filter 17, high frequency noise can be easily and completely suppressed.

Note that the trigger high frequency power source 14 for generating trigger plasma does not need to be connected to the cathode side of the plasma power source 11, and is connected to the sub-electrode 12. Sub-nozzle 13. High frequency power supply 1
4. As long as a circuit is formed using the high frequency bypass capacitor 15, it may be placed anywhere.

In FIG. 3, the high frequency voltage generated by the high frequency power supply 14 is used to ignite the trigger plasma generation circuit 180, but any power supply capable of supplying the same voltage can be incorporated into the trigger plasma generation circuit 18. It is also possible to ignite the trigger plasma in the same way by actually utilizing a capacitor discharge from a capacitor power supply or a surge voltage generated when current is cut off.

Next, an embodiment using the triggered plasma generation circuit 18 shown in FIG. 3 will be described.

Trigger plasma generation circuit 18 (Fig. 3): No-load voltage of power supply 11: 100V.

Trigger plasma current: lOA.

Plasma gas flow rate: 3Q/mj, nAr.

Ds=1.0mm+Lj==1.0mm, Lp=1
．． 2mm.

ds: 1. Omm.

Main plasma generation circuit 21 (Figure 1) Near 1jil
! l no-load voltage: 100V.

Setting current: 50A.

Center gas flow rate: 1. OQ/min Ar.

Shielding gas flow rate: 20Q/min Ar.

La=1mm, Lb=5111m, Lc=10mm
.

Inject trigger plasma for 0.1 seconds under the conditions of d m = 2.4n + m, Dm = 1.0 mm or more, and inject 100 times continuously.
I tried to ignite the main plasma several times. In both cases, the main plasma was ignited extremely stably. Moreover, the main electrode 2. Main nozzle 3. Sub-electrode 12. Sub nozzle 13
No wear and tear was observed. In addition, there was almost no voltage fluctuation of the external power supply when high frequency was generated, and although the measuring equipment or control device used at this time was a built-in microcomputer type, no malfunctions due to high frequency noise occurred. .

In the above, ignition of non-transfer type plasma has been explained, but ignition of non-transfer type plasma or composite type plasma (Fig. 6:
In the case of the conventional example), the process up to ignition of the main plasma between the main electrode 2 and the main nozzle 3 is the same as in the case of the non-transfer type plasma described above. Therefore, the conventional transfer type plasma generator shown in FIG. 6 was improved to implement the present invention as shown in FIG. 4, and in this (FIG. 4) the trigger plasma generator 10 was changed to Using the trigger plasma generation circuit shown in Figure 3, under the same conditions as above, trigger plasma was injected for 0.1 seconds and repeated 100 times.
An attempt was made to ignite the main plasma. In both cases, the main plasma was ignited extremely stably. Moreover, the main electrode 2.
Main nozzle 3. No wear was observed on the sub-electrode 12 and sub-nozzle 13. In addition, there was almost no voltage fluctuation of the external power supply when high frequency was generated, and although the measuring equipment or control device used at this time was a built-in microcomputer type, no malfunctions due to high frequency noise occurred. .

Note that the above explanation relates to a plasma torch for plasma welding, but it does not apply to plasma cutting.

The principle of plasma ignition is the same in other plasma processing that generates similar plasma for processing, such as plasma spraying, and the present invention can be implemented in the same manner.

〔Effect of the invention〕

As detailed above, according to the present invention, a welding device is used.

Non-migration type for cutting, thermal spraying, etc. In ignition of transfer type and composite type plasmas, it is not necessary to use means that cause high power noise generation, such as a high frequency power supply, in the processing plasma generation circuit, so measurement and control equipment using electronic equipment such as microcomputers is required. There is no need to take noise countermeasures that are particularly burdensome.

Furthermore, unlike the contact ignition method in which the main electrode is brought into contact with the main nozzle and then separated, there is no wear and tear on the main electrode because it is a non-contact type. In addition, since the high voltage for ignition is not superimposed on the non-transfer type plasma generation circuit and the transfer type plasma generation circuit, voltage and current detection means are connected to the non-transition type plasma generation circuit and the transfer type plasma generation circuit, and the voltage and current detection means are connected to this detection means. It is possible to connect equipment, etc., and there is no risk of damage to measuring equipment, etc. since no noise current is generated.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an outline of the configuration of a non-transfer type plasma torch for welding that implements one embodiment of the present invention, and FIG.
A block diagram showing an example configuration of the trigger plasma generation circuit 18 shown in the figure, FIG.
It is a block diagram which shows another example. FIG. 4 is a block diagram showing a general configuration of a welding transition type plasma torch that implements another embodiment of the present invention. FIG. 5 is a block diagram showing an outline of the configuration of a conventional transition type plasma torch for welding, and FIG. 6 is a block diagram showing an outline of the configuration of a conventional transition type plasma torch for welding. 1: Non-transfer type plasma power source 2: Main electrode 3: Main nozzle 4 High frequency power source for main plasma arc 5: Base material (work material) 6: Shield cap 7
: Center gas flow 8: Shield gas flow 9: High frequency bypass capacitor 10 Nidoriger plasma generator 11 Nidoriger plasma power supply 12: Sub-electrode ] 3: Sub-nozzle 14 Two-nozzle holder 18 Nidoriga-plasma generation circuit 20 = Plasma torch for welding 21: Non-transfer type plasma generation circuit 22: Transfer type plasma power supply 23: Transfer type plasma generation circuit

Claims (1)

[Claims] In plasma processing in which processing plasma is formed between a non-consumable electrode and a plasma nozzle or a base material: an electric field is formed between the non-consumable electrode and the plasma nozzle, and trigger plasma is injected toward the cathode that forms this electric field. 1. A method for igniting processing plasma, comprising: forming the processing plasma.