JPS60257973A - Method for maintaining pilot arc - Google Patents

Abstract

PURPOSE:To extend the lives of an electrode and a nozzle and to provide the stabilization of a pilot arc and the reduction in the size of a electric power source for the pilot arc by decreasing the pilot arc current of a plasma torch of a transfer type. CONSTITUTION:The plasma torch arch 10 of the transfer type consists of the pilot power source 40 which superposes the DC output necessary for the pilot arc A and the high-frequency output necessary for firing of the pilot arc A on DC output and supplies the electric power and a main power source 30 which supplies the electric power necessary for the main arc B. The power source 40 is changed over to the DC output necessary for firing the arc A and the DC output decreased to about the output necessary for maintaining the arc A to limit the pilot arc current after firing of the arc A and to control said current so as to maintain the discharge thereof.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention is directed to transfer type plasma arc welding,
This relates to a method of transitioning from a pilot arc to a plasma main arc in cutting, thermal spraying, melting, surface processing, high-temperature processing, etc., and in particular, reduces the current value of the pie 1 small arc at the time of main arc ignition, and The present invention relates to a method for holding a pilot arc of a plasma arc torch, which allows easy re-ignition of the main arc required for work.

[Prior Art] This type of plasma arc torch generates a main arc by applying voltage to gas in a plasma state, and uses the plasma main arc as a heat source to perform welding, cutting, thermal spraying, melting, surface processing, and high-temperature processing. etc.

In general, nozzles (constrained tips) placed at regular intervals around the tungsten electrode where the tungsten electrode
Argon gas is jetted as plasma gas into the gap between
Transfer type plasma arc welding equipment is well known, in which shielding gas is flowed through the gap between the nozzle and the shield nozzle, and welding is performed while preventing oxidation of the welded part. The following description focuses on transfer type plasma arc welding equipment.

The transfer type plasma arc welding device includes:
By applying a high frequency between the tungsten electrode and the nozzle, the argon gas is ionized into a plasma state, and a voltage is applied between the tungsten electrode and the nozzle to generate a pilot arc and generate the pi[] The l-arc ionizes the argon gas into a plasma state, and when it transfers between the materials to be welded, the tungsten electrode and the materials to be welded become substantially electrically conductive. In this state, when a voltage is applied between the tungsten electrode and the workpiece, a high-temperature plasma main arc is generated, and welding is performed using the high-temperature plasma arc.

A conventional example of this type of transfer type plasma arc welding apparatus will be explained with reference to the drawings. Figures 2 and 3 are explanatory diagrams showing the operating status of a conventional 1-Lancef 7 type plasma arc welding device. Figure 2 shows the ignition status of the pilot arc, and Figure 3 shows the ignition status of the main arc. It indicates the condition. In the figure, an electrode 1 is a rod-shaped electrode made of a tangent or the like, and is placed in the center of a nozzle 2.

The nozzle 2 is made of a material such as brass or copper, and a cold IJ1 water channel 3 is formed in the whole or part of the end thereof to cool the nozzle 2 so as to produce a pinch effect. An inert gas flow path 4 such as argon gas for maintaining plasma is formed between the electrode 1 and the nozzle 20, and the electrode 1, nozzle 2, and cooling water channel 3 constitute a plasma arc welding device 10. Note that originally, the plasma arc torge 10 of a transfer type plasma arc welding apparatus has a nozzle part disposed on the outer periphery of the nozzle 2 and injects a powder gas that conveys shielding gas and powder, but the gist of the present invention is not limited to this. This is omitted as it is not directly related.

Between the electrode 1 and the nozzle 2, a parallel circuit of a stabilizing resistor R and a high-frequency bypass capacitor C, a pyrower 1 to a power supply circuit switch S1, and a pyrower 1 to a power supply circuit 20 are connected in series.

The pilot power supply circuit 20 includes a pilot DC power supply circuit 21 consisting of an AC, -DC conversion circuit, etc. for exchanging AC power to DC, a high frequency bypass capacitor C6 connected in parallel, and the pilot DC Power circuit 2
It consists of a high frequency generation circuit 22 that generates a high frequency output that is superimposed on the DC output of 1. The high frequency generating circuit 22 is generally composed of a high frequency generating circuit or a high frequency oscillation circuit having a spark gap or the like, and its output impedance is small even when there is no output from the high frequency generating circuit.

Further, between the electrode 1 and the material to be welded F15 is a DC power source having a voltage and current that generates a plasma main arc.
A main power source 30, which generally includes an AC-DC conversion circuit for converting alternating current into direct current, and a main power switch S2 connected in series with the main power source 30 are connected in series. Then, one end of the high-frequency pipe capacitor C connected in parallel with the material to be welded 5 and the stabilizing resistor R, one end of the pipe [I], one end of the power switch S1, and one end of the main power switch S2 are connected to a common wiring. do.

The transfer type plasma arc welding apparatus constructed in this manner operates as follows.

First, as shown in Fig. 2, the pilot power switch S1
When closed, the output of the high frequency generation circuit 22 is superimposed on the output of the pylon 1-DC power supply circuit 21, and the voltage is applied to the electrode 1.
and is applied between nozzle 2. The output of the high frequency generation circuit 22 is raised by the DC output of the pilot DC power supply circuit 21, and its peak output is large, and the high frequency generation circuit 22 is formed by high frequency bypass capacitors C and C8, Between electrode 1 and nozzle 2, pi [1 point arc 8 ′
ignite. Under the influence of the high-frequency output, the space between the electrode 1 and the nozzle 2 is ignited, and when the arc Δ occurs, the argon gas flowing between them is ionized, and a high-temperature ionized gas flow is emitted from the nozzle 2. It ejects and reaches the material 5 to be welded at a height of 1".

6- After that, as shown in Fig. 3, when the main power switch S2 is turned on, the impedance between the electrode 1 and the material to be welded II 5 is low due to the high temperature ionized gas flow, and the plasma Main arc B occurs. Thereafter, the material to be welded 5 is welded by the ignition state of the main arc B. Then, the pilot arc A that was fired is:
With the pilot power switch S1 turned on, the plasma arctope can be used intermittently by opening and closing the main power switch S2.

[Problems to be Solved by the Invention] In the transfer type plasma arc welding device mentioned in this type of conventional example, the pilot power switch S1 is always turned on during use, and the electrode 1 and nozzle 2 are connected. During this period, Pylon I/Arc 8 is in the ignited state and the main arc is waiting to be re-ignited, so the pilot arc current (usually used in the range of 20 to 50Δ) is It has almost no effect on the material being treated, and the electrode 1 and nozzle 2 are subject to wear and deformation due to heating due to discharge, and depending on the degree of
There may be cases where it is difficult to transition to the main arc. Further, in the case where the pilot arc current is large, there is a drawback that if the pilot arc becomes unstable, the main arc also becomes unstable.

Since a pilot arc current flows even when the main power supply 30 is used, a continuous fixed circuit is required as the pilot power supply 20, which has disadvantages such as the pilot power supply 20 becoming larger and the power supply setting space becoming larger. Ta.

In order to eliminate these drawbacks, the pyrower 1 to the power switch S1 are connected to the platform where the main arc is ignited.
Something that turns off the pilot power supply 20 of pilot arc A.
There is.

However, even in this kind of -carrying main arc A
If the arc is extinguished, it is necessary to ignite from the pilot arc A when re-driving, and if this operation is performed frequently, the high frequency generation circuit 22 will be ignited for each operation. Since a drive is required, radio wave interference caused by high frequencies, electric m-induction, etc. may have an adverse effect on the control device.

In addition, during re-ignition IJ, the electrodes are not heated properly at all times, so there are drawbacks such as abnormal wear of the electrodes in the first 1ffl of arc ignition.

[Problems to be solved by the invention] Therefore, the present invention aims to eliminate the above-mentioned drawbacks. 1. Pyrower of Lance-force type plasma torch 1. By reducing the arc current, the life of the electrode and nozzle is extended, and the arc is reduced. The challenges are stabilization and miniaturization of the pilot power source.

[Means for solving the L problem] The present invention supplies power by superimposing high-frequency output on the DC output necessary for ignition of the arc. In a plasma arc tope consisting of a main power supply, the pyrower 1 to the power supply has the output required to ignite the pilot arc and the reduced output required to maintain the discharge of the pylon 1 arc. The pilot arc is maintained at −0 − by switching.

[Effect] The structure of the present invention described above operates as follows.

When igniting the pilot arc, the high-level output from the pyrower 1 to the power supply is applied at 19, and the high-frequency output superimposed thereon sets the pylon]-arc to the ignition state,
reducing the output from the pilot power source to the reduced current necessary to maintain the pilot arc upon transition from the pi [1 arc ignition state to the main arc state;
Reduces pilot arc current during main arc ignition
).

[Embodiments of the Invention] FIG. 1 is a 3-dimensional diagram of a plasma arc tope of a plasma arc welding apparatus for explaining the present invention in detail. In the figure, 1 to 5.30 and A described in Figures 2 and 3.
, B, R, and C indicate the same parts as those described in the conventional example.

The power supply 40 to pylon 1 is the pylon described in the conventional example] 1
The difference is that the pyroluminescence source 20 described in the conventional example usually superimposes a high frequency output as a pilot current to the ignition current to 20 to 50.
The pilot power supply 40 used in this embodiment is connected to the pi[1
When the arc Δ is ignited, the setting terminal 1-11, which conducts the same current value of about 20 to 50 A, is connected to the setting terminal 1-11, which conducts the same current value of about 20 to 50 A, and the -loss pi [1-1-arc 8 is ignited, and the main arc B is transferred to I. In, the pilot arc A(7)? u The point is that the current value has a setting terminal (-0) that supplies current to the pylon 1 with a current value reduced to the limit sufficient to maintain the arc 8, that is, about 5A.

Switching between the setting terminal 11i and 1-0 is performed by the drive unit 5.
1, and the drive section 51 is controlled by the controller 50. The main power source 30 is opened and closed by the main power switch section S4, and the main power source 30 is opened and closed by the main power switch section S4.
4 is driven by a drive unit 52, and the drive unit 52 is controlled by one unit 50.

Next, the operation of each component of an embodiment of the present invention configured as shown in FIG. 1 will be explained using FIG. 4. FIG. 4 shows the time interval <7-1- of one embodiment shown in FIG.

First, in response to a start signal given to the controller 50, the controller 50 drives the switch drive section 51 to drive the pyrolamilumi source 40 and set the output of the pilot power source 40 to a high level at the 1" 1 side terminal. Then close the power switch S3. When the piston 1 to the arc 8 are ignited between the electrode 1 and the nozzle 2 by the output of the pilot power supply 40 superimposed with high frequency power, a pilot arc current II+ flows. The high frequency output may be generated for an arbitrary time τ after the arrival of the start signal. Of course, the pilot arc is ignited on pylon 1.
This may be confirmed by detecting the arc current, and upon confirmation, the high frequency output may be controlled to be turned off. - Turn on the in-power switch S4, apply voltage to the main power source 30 between the electrode 1 and the workpiece 115, generate the main arc B, and the main current IH flows.During the time T1, the controller 50 This is sufficient time to ignite the pilot arc Δ with the star 1 to signal 19.Then, the controller 50 controls the main power switch S4.
After a period of time T2 has elapsed since the time when the pilot power source 40 was turned on, the pilot power supply selector switch S3 is switched to the 1-0 side terminal output determined by the pilot arc maintenance current of the pyrolamilmi source 40. Due to the output of the LO side terminal of the source 40, a reduced pilot arc current I flows between the electrode 1 and the nozzle 2. In this state,
Plasma 1--chi performs welding work. Welding work time t1
When the welding work is completed by turning on the main power switch S4 after , the main current 18 is cut off and the main arc B is extinguished at the same time.

During the stop time t2 from when the main arc B stops until the plasma torch starts working again, the pilot power supply Δ is ignited by the pilot current I[. When a restart signal is given to the controller 50 to start the next work, the controller 50 switches the pilot power supply selector switch S3 to the 1-11 side terminal side, and switches the arc current from pylon 1 of the pi[]t arc A to the 1-11 side terminal. Then, after 11 hours have elapsed, the main power switch S4 is closed and welding work using the main arc B can be started. 1 after main power switch S4 is closed
After 2 hours, change the current of pie 1 tip 1 to arc A to 11-
After the welding work using the main arc A is completed, the current I is maintained until a restart signal is input to the controller 50.
, continues.

The specific control circuit of the controller 50 may be a contraceptive means such as a timer since the controller 50 performs sequential delay operations.

Incidentally, when the plasma torch used in the plasma arc welding apparatus according to the embodiment of the present invention shown in FIG. 1 is controlled by a microprocessor, it is preferable to control the plasma torch as shown in FIG. 5. FIG. 5 shows an embodiment of the present invention shown in FIG. 1 which is controlled by a microprocessor.

The controller 50 having a built-in microprocessor performs control as follows. First, this system is started by Star 1 to Isu. In step 71, the main power supply 30
And the pilot power supply 40 etc. are activated. At step 72, the pilot power switch S3 is turned on.
As a part, DC output electrode 1 and nozzle 2
The output of the high frequency intervening circuit is superimposed on the output of the DC power supply circuit to facilitate the initiation of discharge between the two. When the time limit τ, which is set to a time sufficient to generate arc A to pilot 1, has elapsed, the output of the high frequency generation circuit is cut off in step 74. In step 75, arc A flows to pilot 1 with a high temperature ionized gas flow. After a time T1 sufficient to form the main power supply switch S4 is closed. By closing the main power switch S4, the main arc B
occurs, the switch S4 is closed in step 77, and as time T2 elapses, the power switch S3 is switched to the 1, O side terminal in step 78, and the pyrolamy is switched to the O side terminal. Reduce the current 15-. In this state, welding work is performed in step 79. When the welding work is completed, the main power switch S4 is turned off in step 81. And the pilot [・
If the work is to be restarted with arc A ignited, step 82 will lead to step 75 and step 1]-. If you do not want to start working again, proceed to step 8.
Step 3 terminates the plasma 1 hege control system used in the plasma arc welding device.

Further, FIG. 6 shows a plasma arc welding apparatus according to an embodiment of the present invention. Further, FIG. 7 is a flowchart for controlling another embodiment of the present invention shown in FIG. 6 by the microphone [1 processor'.

To describe only the differences between the plasma arc welding apparatus of the embodiment shown in FIG. 1 and the plasma arc welding apparatus of the embodiment shown in FIG. Main arc current is detected between material 5 and main power switch S4. +116"ll□.73F. A, 7, A, 7'1" current path of arc, i.e. presence or absence of high frequency current between nozzle 3, pilot 1 to 16-, power switch S3, and value of pilot current A current detector 62 is connected to the fish to detect the current.

Therefore, the [1-chart in FIG. 7] also differs in the following points. In step 733 of FIG. 5, the 6-frequency output is cut off with a time limit of τ, but in the corresponding step 93 of this embodiment, the pilot arc is determined by the presence or absence of the DC current of the pilot arc of the current detector 62. This is for determining ignition. In addition, the step 77
- The time required for the arc current IH to form an ionized gas flow high enough to ignite the main arc B was set as T2, but in this embodiment, the current detector 6
The ignition of the main arc B is confirmed by the output of 1, and T is set as the time limit for the main arc to become stable in step 97.
It is set in .

In the plasma arc welding apparatus of this embodiment, the plasma arc tope can also be controlled by the controller 60 according to the same flow chart as in the previous embodiment.

= 17- In the above embodiments, the plasma arc tope of plasma arc welding H'FI is described. , Transfer of the present invention 1) J type plasma arc used for cutting, melting, melting, surface processing, high temperature processing, etc. Similarly, in the plasma arcs 1 to 1 of the embodiments described in nQ, Maintenance methods can be adapted.

[Effects of the Invention] As described above, the present invention provides a transfer type plasma torch in which the pilot
By switching between the DC output required to ignite the arc and the DC output as low as necessary to maintain the pyrower 1-2 hair,
Since the arc current is limited and controlled to maintain the discharge of
Providing a long life for the electrode and nozzle also stabilizes the arc. In addition, it is possible to limit the par 18 = pilot arc current after the arc ignition, and there is no need to base the pilot power supply on the continuous rating of the DC output necessary for ignition of the arc. - The power supply can be made smaller.

Furthermore, since the high-frequency power used when igniting the pilot arc is the same as that used at the beginning of plasma 1hage use, the effects of radio interference, electrical induction, etc. caused by high-frequency waves should be minimized as much as possible. I can do it.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a plasma arc 1--1 according to an embodiment of the present invention, and Fig. 2 shows the ignition state of the pyrower 1--arc.
An explanatory diagram, FIG. 3 is an explanatory diagram showing the ignition state of the main arc, and FIG. 4 is an explanatory diagram showing the timer 1 to 1 of the embodiment shown in FIG.
, FIG. 5 shows the example 71 shown in FIG. 1.
1-1 FIG. 6 is an explanatory diagram of a plasma arc 1 hedge that illustrates another embodiment of the present invention, and FIG. 7 is a flowchart of the embodiment shown in FIG. ... Pi [Arc to 1 1, -19 = B... Main arc, 10... Plasma arc i... -chi 20, 40... Power to pilot 1, 30... Main power, 50. 60...] controller, In addition, in the figure, the same line and the same part 6 indicate the same or corresponding parts. Patent applicant: Daido Steel Co., Ltd. 1 Agent: Patent attorney Takesho-20 - Tokukai Sho GO-257973 (9)

Claims (2)

[Claims] (1) From a pilot power supply that supplies power by superimposing the DC output necessary for the pilot arc and the high frequency output necessary for ignition of the pilot arc on the DC output, and from the main power supply that supplies the power necessary for the main arc. In the transfer type plasma arc torch, the pilot power supply is switched between a DC output necessary for igniting the pilot arc and a DC output reduced to the extent necessary to maintain the pilot arc. 1. A method for maintaining a PI arc, which comprises controlling the PI 1 arc current to maintain its discharge by limiting the PI 1 arc current after the PI arc ignition. (2) The pilot arc retaining method described in Patent No. 1, wherein the control is performed by a microphone [1 browser].