JPS6117360A - Plasma arc welding device - Google Patents

Abstract

PURPOSE:To obtain good weld beads of high quality by controlling the working gas pressure of an welded object to a molten pool to be constant by output signals of a pilot arc voltage comparator. CONSTITUTION:The pilot are is generated at all times continuously while main arc is being generated. When a nonconsumable electrode 2 is consumed by welding, the distance Lp between nonconsumable electrode 2 and a nozzle electrode 3 becomes longer, and pilot arc voltage Vp becomes higher. Then, the voltage is compared with the pilot arc reference voltage set by a pilot arc reference voltage setting device 11 to detect fluctuation of pilot arc voltage, and the result is made to an output signal and sent to a corrector 13. The corrector 13 makes specified operation to make the distance between the nozzle electrode 3 and the object of welding 5 constant for the reference voltage set by a main are reference voltage setting device 9, and corrects the reference voltage set by the setting device 9 to a rather high value.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a plasma arc welding device, and particularly to a plasma arc welding device suitable for controlling a working gas pressure to a molten pool of a workpiece at a constant level. be.

[Background of the invention]

First, a conventional plasma arc welding apparatus having an arc voltage/amount control function will be explained with reference to FIG.

FIG. 5 is a configuration diagram of a conventional plasma arc welding device.

In the figure, 1 is a plasma welding power source, 2 is a non-melting electrode such as a tung or stainless electrode, and 3 is a nozzle electrode.

4 is a resistor for generating a pilot arc of a constant current between the non-electrode type electrode 2 and the nozzle electrode 3.

Reference numeral 5 denotes a workpiece, and a main arc of a plasma arc is generated between the non-molten electrode 2 and the workpiece 5 using a pilot arc as an ignition source to perform welding. Reference numeral 6 indicates a gas flow rate controller for supplying a working gas, 7 indicates a welding torch having a non-electrode type electrode 2 and a nozzle electrode 3, and 8 indicates a welding torch drive device that moves the welding torch 7 up and down.

9 is a main arc reference voltage setter, and 10 is a main arc voltage comparator that compares the main arc voltage with the main arc reference voltage.

If the main arc voltage generated between the non-fusing electrode 2 and the workpiece 5 is different from the reference voltage set by the main arc reference voltage setting device 9, the main arc voltage comparator 10 The output signal of the main arc voltage comparator 1o is sent to the drive motor 8a of the welding torch drive device 8, and the operation of the drive motor 8a moves the welding torch 7 upward or downward, and the non-melting electrode 2
The main arc voltage v,I is kept constant by controlling the distance @r=, between and the workpiece 5.

By the way, in plasma arc welding, the working gas supplied from the gas flow rate controller 6 to the welding torch 7 is ejected from the nozzle electrode 3 at high speed, and the pressure exerted by this working gas on the molten pool of the workpiece 5 increases the welding temperature. Affects bead formation. That is, in order to obtain a good weld bead, it is necessary to control the pressure exerted by the working gas on the molten pool, that is, the working gas pressure with respect to the molten pool, to a constant value.

FIG. 6 is a line showing the relationship between the distance between the nozzle electrode 3 and the workpiece 5 and the working gas pressure P with respect to the molten pool of the workpiece 5 when the working gas flow rate Q is constant. It is a diagram.

As is clear from this figure, the nozzle electrode 3 and the workpiece 5
It can be seen that as the distance Lx between the molten pool and the molten pool increases, the working gas pressure P to the molten pool decreases, and as the distance Lx decreases, the working gas pressure P increases.

Therefore, in the above-mentioned conventional plasma arc welding apparatus, since the distance between the non-molten electrode 2 and the workpiece 5 is kept constant, for example, when welding for a long time, the distance between the non-fusion electrode 2 and the workpiece 5 is When the welding torch drive unit 8 is exhausted, the distance LH between the non-fusing type electrode 2 and the workpiece 5 is kept constant by lowering the welding torch drive device 8 by the main arc voltage/volume control. However, as a result, the distance between the nozzle electrode 3 and the workpiece 5 becomes shorter, and as described in the explanation of FIG. This has the drawback of adversely affecting the formation of weld beads.

[Purpose of the invention]

The present invention has been made to solve the problems of the prior art described above, and it is possible to control the working gas pressure to the molten pool of the workpiece at a constant level even if the main voltage changes.
The purpose of the present invention is to provide a plasma arc welding device capable of obtaining high quality and good weld beads.

[Summary of the invention]

The configuration of the plasma arc welding apparatus according to the present invention includes a welding torch that generates a main arc by supplying working gas between a non-molten electrode and a workpiece, and a pilot that serves as an ignition source for the main arc. an arc generator; a main arc voltage comparator that compares the main arc voltage between the non-fusing electrode and the workpiece with a preset main arc reference voltage; and the main arc voltage comparator. A plasma arc welding device comprising a welding torch drive device that controls the distance between the non-fusing electrode and the workpiece based on an output signal, the plasma arc welding device being configured to constantly generate a pilot arc even when a main arc is being generated. At the same time, a pilot arc voltage comparator is provided to detect fluctuations in the pilot arc voltage and compare it with a pilot arc reference voltage. No. 5 is configured to control the pressure at a constant level.

Additionally, the idea behind developing the present invention is as follows.

FIG. 7 shows the distance Lx between the nozzle electrode and the workpiece, and
Pilot arc voltage ■A between the non-fusing electrode and the nozzle electrode, and main arc voltage ■ between the non-fusing electrode and the workpiece. This is a relationship diagram between the pilot arc voltage v2 and the main arc voltage v, I shown in FIG.
I thought about taking advantage of the relationship.

That is, when the distance L8 between the nozzle electrode 3 and the workpiece 5 shown in FIG.
Focusing on the fact that the relationship between the distance mL7 between the nozzle electrode 3 and the pilot arc voltage (a) and the main arc voltage vM is linear, we A pilot arc is always generated even while an arc is being generated, and by detecting this pilot arc voltage vr, the relative position of the nozzle electrode 3 with respect to the non-fusing electrode 2 is calculated, and processing is performed based on that information. By doing so, the working gas pressure P to the molten pool of the workpiece 5 is controlled to be constant.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

First, FIG. 1 is a configuration diagram of a plasma arc welding apparatus according to an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 5 are the same parts as those in the prior art, so the explanation thereof will be omitted.

In FIG. 1, the parts numbered 1 to 10 are exactly the same as the conventional device shown in FIG.

Reference numeral 11 indicates a pilot arc reference voltage setting device; 12 indicates a pilot arc voltage generated between the non-fusing electrode 2 and the nozzle electrode 3 and a pilot arc reference voltage set by the pilot arc reference voltage setting device 11; The pilot arc voltage comparator 13 to be compared is a corrector that corrects the main arc reference voltage set by the main arc reference voltage setter 9 using the signal output from the pilot arc voltage comparator 12.

The operation of the plasma arc welding apparatus having such a configuration will be explained.

A pilot arc is generated between a non-fusing electrode 2 and a nozzle electrode 3 by a plasma welding power source 1, and using this as an ignition source, a main arc is generated between the non-fusing electrode 2 and the workpiece 5. Perform welding.

The pilot arc shall be generated continuously even during the main arc generation.

Now, when the non-fusing electrode 2 is worn out due to long-term welding, the distance T between the non-fusing electrode 2 and the nozzle electrode 3 increases, and the pilot arc voltage Va increases accordingly. Then, the pilot arc voltage comparator 12 compares the pilot arc reference voltage with the pilot arc reference voltage set by the pilot arc reference voltage setter 11 to detect the fluctuation of the pilot arc voltage v2, and the result becomes an output signal and is sent to the corrector 13. sent to. The corrector 13 uses the signal to adjust the distance L between the nozzle electrode 3 and the workpiece 5 with respect to the reference voltage set by the main arc reference voltage setting device 9.
Predetermined arithmetic processing is performed so that 8 becomes constant, and the reference voltage set by the main arc reference voltage setting device 9 is corrected to be higher.

As a result, the non-fusible electrode 2 is consumed and the workpiece 5
Even if the main arc voltage v,I increases, the distance Lx between the nozzle electrode 3 and the workpiece 5 is maintained constant, and therefore the working gas pressure P with respect to the molten pool of the workpiece 5 is kept constant. can be kept.

Note that depending on the welding result, there may be a case where it is desired to arbitrarily control the working gas pressure P to the molten pool of the workpiece 5, but in that case, the arithmetic processing in the corrector 13 may be changed.

Next, another embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a configuration diagram of a plasma arc welding apparatus according to another embodiment of the present invention. In the figure, the same reference numerals as in FIG. Since there is, I will omit the explanation.

In FIG. 2, parts 1 to 12 are the same as the device in the embodiment shown in FIG. 1, and the corrector 13 shown in FIG.
is not required in this embodiment.

Reference numeral 14 denotes an electrode drive device that can move the non-fuse type electrode 2 up and down.
It constitutes an electrode driving means for raising and lowering the electrode 2 to adjust the distance between the welding object 5 and the welding object 5.

The operation of plasma arc welding i[ having such a configuration will be explained.

In this device as well, the pilot arc is generated continuously during the main arc generation.

If the non-fusible electrode 2 is worn out due to long-term welding, the non-fusible electrode 2. and the distance II between the nozzle electrode 3,
becomes longer, and accordingly the pilot arc voltage V,
becomes higher. Then, the pilot arc voltage comparator 12
compares it with the pilot arc reference voltage set by the pilot arc reference voltage setting device 11, detects the fluctuation of the pilot arc voltage vP, and uses the result as an output signal to drive the electric drive device 14. Sent to motor i4a.

The drive motor 14a has a pilot arc voltage comparator 12.
The electrode drive device 141r9A is activated by the output signal of
workpiece 5 by lowering the non-melting electrode 2 independently.
Adjust the distance L ++ k between the

As a result, the distance between the nozzle electrode 3 and the workpiece 5,
Since the distance mL)1 between the non-fusion electrode 2 and the workpiece 5 can be corrected while keeping constant, the working gas pressure P against the molten pool of the workpiece 5 can be kept constant. I can do it.

In the sixth embodiment shown in FIG. 2, unlike the above-described embodiment shown in FIG. This embodiment has the feature that it is possible to perform more precise control than the embodiment shown in FIG.

In addition, also in this embodiment, it is possible to control the working gas pressure P arbitrarily.

Next, still another embodiment of the present invention will be described with reference to FIGS. 3 and 4.

FIG. 3 is a diagram showing the relationship between the working gas flow rate Q and the working gas pressure P relative to the molten pool, and FIG. 4 is a configuration diagram of a plasma arc welding apparatus according to still another embodiment of the present invention. Fourth
In the drawings, the same reference numerals in FIG. 1 are the same parts as those of the apparatus of the previous embodiment shown in FIG. 1, so their explanation will be omitted.

The embodiment shown in FIG. 4 was developed based on the relationship between the working gas flow rate Q and the working gas pressure P shown in FIG. That is, as the working gas flow rate Q increases, the workpiece 5
Considering that the working gas pressure P for the molten pool increases linearly, the function of the gas flow rate controller 6 is improved.

In FIG. 4, parts 1 to 12 are the same as those in the embodiment shown in FIG. 1, and in this embodiment, the corrector 13 shown in FIG. 1 and the electrode drive device shown in FIG. 14
does not require.

15 is a regulating valve drive motor that opens and closes the regulating valve 6a of the gas flow rate controller 6;
The regulating valve drive motor 15 constitutes gas flow rate control means.

The operation of the plasma arc welding apparatus having such a configuration will be explained.

In this device as well, the pilot arc is generated continuously during the main arc generation.

Now, when the non-fusible electrode 2 is worn out due to long-term welding, the distance ML between the non-fusible electrode 2 and the nozzle electrode 3 becomes longer, and the pilot arc voltage vP increases accordingly. Then, the pilot arc voltage comparator 12 compares it with the pilot arc reference voltage set by the pilot arc reference voltage setting device 11, detects the fluctuation of the pilot arc voltage V, and the result becomes an output signal. It is sent to the regulating valve drive motor 15 of the gas flow rate controller 6.

The regulating valve drive motor 15 is operated by the output signal of the pilot arc voltage comparator 12, and adjusts the valve opening degree of the regulating valve 6a of the gas flow rate controller 6, thereby regulating the supply gas flow rate Q.

As a result, the main arc reference voltage setting device 9. The welding torch drive device 8 is actuated by the main arc voltage amount control by the main arc voltage comparator 10, and the nozzle voltage @3 is activated.
Even if the distance between the workpiece 5 and the workpiece 5 changes, the working gas pressure P relative to the molten pool of the workpiece 5 can be kept constant.

In addition, also in this embodiment, it is possible to control the working gas pressure P arbitrarily.

Further, in each of the above embodiments, when the welded electrode 2 is worn out and the distance between the non-fused electrode 2 and the nozzle electrode 3 becomes long, the molten pool of the welded object is Although the control of the working gas pressure P relative to y has been described above, the present invention is applicable not only to changes in the main arc voltage vM caused by other factors, but also to changes in the main arc voltage vM caused by other factors. , it is possible to control the working gas pressure P to the molten pool at a constant level.

〔Effect of the invention〕

As described above, according to the present invention, even if the main arc voltage changes, the working gas pressure against the molten pool of the workpiece can be controlled to be constant, and a good quality weld bead can be obtained. It is possible to provide a plasma arc welding device capable of

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a plasma arc welding apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of a plasma arc welding apparatus according to another embodiment of the present invention, and FIG. 3 is a block diagram of a plasma arc welding apparatus according to another embodiment of the present invention. A relationship diagram between flow rate and working gas pressure, FIG. 4 is a configuration diagram of a plasma arc welding apparatus according to yet another embodiment of the present invention, and FIG. 5 is a configuration diagram of a conventional plasma arc welding apparatus.
FIG. 6 is a relationship diagram between the distance between the nozzle electrode and the workpiece and the working gas pressure when the working gas flow rate is constant;
FIG. 7 is a diagram showing the relationship between the distance between the nozzle electrode and the workpiece, and the pilot arc voltage and main arc voltage. 1... Plasma welding power source, 2... Non-melting electrode, 3
. . . Nozzle electrode, 5. Object to be welded, 6. Gas flow rate controller. 6a... Regulating valve, 7... Welding torch, 8... Welding torch drive device, 9... Main arc reference voltage setting device, ]0... Main arc voltage comparator, 11... Pyro Tsukuarc reference voltage setter, 12... Pilot voltage comparator, 13... Corrector, 14... Electrode drive device, 14a... Drive motor, 5... Adjustment valve drive motor.

Claims (1)

[Claims] 1. A welding torch that generates a main arc by supplying a working gas between a non-fusing electrode and a workpiece, and a pilot arc generator that serves as an ignition source for the main arc;
a main arc voltage comparator that compares the main arc voltage between the non-melting electrode and the object to be welded with a preset main arc reference voltage; In a plasma arc welding device equipped with a welding torch drive device that controls the distance between a polar electrode and the workpiece, the plasma arc welding device is configured to constantly generate a pilot arc even during main arc generation, and the pilot arc A pilot arc voltage comparator is provided to detect voltage fluctuations and compare with a pilot arc reference voltage, and the working gas pressure to the molten pool of the workpiece is kept constant based on the output signal of the pilot arc voltage comparator. A plasma arc welding device characterized in that it is configured to control. 2. A plasma arc welding apparatus according to claim 1, which is provided with a corrector for correcting the set value of the main arc reference voltage based on the output signal of the pilot arc voltage comparator. 3. The product described in claim 1 is provided with an electrode drive means for adjusting the distance between the non-fusing electrode and the workpiece by the output signal of the pilot arc voltage comparator. A plasma arc welding device. 4. Plasma arc welding according to claim 1, which is provided with gas flow rate control means for adjusting the flow rate of working gas supplied to the welding torch based on the output signal of the pilot arc voltage comparator. Device.