JPS6178570A - Arc length control device - Google Patents

Abstract

PURPOSE:To keep the arc length constantly even with the variation in welding conditions by making the arc voltage of after the lapse of a certain time from the rise of the arc voltage a reference voltage and by moving vertically a tungsten electrode based thereupon. CONSTITUTION:An arc 5 is generated between the tungsten electrode 1 of a torch 4 and a base metal 2 and the arc voltage which is in the condition of the arc length l of immediately before a welding head starting to move is measured and stored into an AVC device 13 as the reference voltage of AVC. In this case the effect of the ripple of a power source 3 is removed by measuring the mean voltage for about 0.1-1.0sec by the reference voltage. When the welding is started with moving the head the torch 4 is moved vertically by the driving motor 14 of AVC so as to enter the reference voltage and the arc voltage under welding within the fixed range to control so as to make the arc length constant. A nearly fixed arc length is thus maintained even with the variation in the welding conditions of the shape and diameter of the electrode 1, the shielding gas flow quantity, the quality of the base material 2, etc.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an arc length control device in TIG welding,
In particular, hot wire switching TIG welding (hereinafter simply H)
This relates to an arc length control device for 8T welding.

[Background of the invention]

Figure 8 shows the equipment commonly used in the Li hot wire TIG welding method. In the figure, the tungsten electrode 1 and the base material 2 are connected to an arc current with DC drooping characteristics.
6, the base material 2 is melted by forming an arc 5 in an argon shielding gas with the tungsten electrode 1 as the negative electrode and the base material 2 as the positive electrode. If wire 6 is simply added to this, it is normal T4G welding, but contact tip 7 and base metal 2
Connect between them with a DC or AC wire power supply 9, and connect the wire feeding device r! Wire 6 sent from 19 to the arc generating part
Hot wire TI is a product that increases the melting speed of wire 6 by passing direct or alternating current through it to generate Joule heat.
This is the G welding method. A problem with this method is the magnetic blowing phenomenon of the arc 5 caused by the wire current of the wire 6.

That is, by energizing the wire 6, the arc 5 is swung forward or backward in the direction of movement, making the molten pool unstable and the workability significantly impaired. Even when the wire current is alternating current, there is no time for the arc 5 to be fixed at the center of the molten pool, so the rigidity of the arc 5 is not maintained, resulting in poor melting work. In order to reduce the influence of these magnetic blows during welding, the wire current is usually 2 times the arc current.
The melting rate of the wire 6 is limited to about 20 g/min at most. By the way, the magnetic interference of the arc 5 due to the energization of the wire 6 is eliminated, and the wire 6
The hot wire switching TIG (H8T) m-contact method has been implemented as a method to increase the melting rate of the metal. In this method, as shown in Fig. 9, the arc current α is a pulse current having a peak and a base period (arc peak current αp and arc base current Ibp), and the wire 6 is not energized during the peak period T1. By energizing the wire 6 only during the base period T2, magnetic blowing of the arc 5 is eliminated and a high amount of dissolved M is obtained. According to this method, a melting rate of 1009/min or more can be obtained with almost no influence from magnetic blowing. Note that W in FIG. 9 is the wire current to the wire 6, I
wp indicates wire peak current and T indicates time.

Figure 10 shows the commercially available TIG power supply with GTO (GI0LtgT1).
tr9O//) Thyristor (hereinafter referred to as G'l'O)
The purpose is to perform hot wire switching TIG (I=[ST) welding by adding a switching unit using shape, and in parallel with this, the first
The wire 6 is connected via 0TO10, and the wire 6 is heated periodically by this ON-OFF. i.e.
When lG'l'o10 is in the ON state, the current supplied as an arc current from the welding power source 3 is short-circuited through the wire 6, becomes a wire current, and heats the wire 6. If 5 disappears, welding cannot be continued, so a base electric current i1f[12 is added. In addition, proper heating control of the wire 6 is performed in the 20th TO1
1 is set to 0N-OFF to short-circuit the turtle flow.

On the other hand, as a method to keep the arc length constant in TIG welding, the Aro Voltc method measures the arc voltage and moves the torch 2 up and down until it becomes equal to the reference voltage.
An HHControl (hereinafter simply referred to as AvC) device is often used.

Figure 11 is a characteristic curve diagram of arc voltage and current in TIG welding, where curves A, B, and O indicate the arc length. , points E, F, and G are operating points.

The characteristic curve diagram in FIG. 11 shows that the arc voltage changes greatly in the low current range, but in the practical current range, if the arc length is constant, it hardly changes even if the current changes. The AVO device utilizes this feature to keep the arc length constant. In other words, when controlling the arc length to be constant on curve B, the arc voltage E2 at this time is
is set as the reference voltage, and if the arc length of arc 5 becomes longer for some reason, the arc voltage becomes the reference voltage E.
2, and when the arc length of arc 5 becomes shorter, the torch 4 is raised to keep the arc length constant on curve B. It is used in automatic TIG welding machines.

However, even if the arc length is constant, the arc voltage varies depending on the shape and diameter of the tip of the tungsten electrode 1, the material of the base material 2, the flow rate of the shielding gas, and the arc power source 3. For example, the tungsten electrode 1 has a sharp tip as shown in FIG. 12(α), and the tungsten electrode 1 has a rounded tip as shown in FIG. 12(b). As shown in C), the voltage increases significantly even with the same arc length. Note that the curve H in Figure @12 is the 12th
The electrode in figure (α), curve I, shows the electrode in figure 12 (b). In this way, each time the above-mentioned conditions change, the relationship between arc length, current, and voltage as shown in FIG. 11 must be experimentally determined, and even if an AVO device is installed, the range of application is narrow.

In addition, there is a difference in voltage between the tungsten electrode 1 immediately after polishing and the electrode once used for welding work, as shown in Figure 12 (6), or changes each time the tungsten electrode 1 is consumed during welding. There are also problems.

On the other hand, Fig. 8 shows a type of automatic T-work G welding with additive wire 6.
This shows hot wire TIG welding in which electricity is fed while being heated. Electric power is supplied from the arc power supply 3 to the tungsten electrode l pole 1 and the base metal 2rJJ, generating an arc 5, and the base metal 2 and wire No. 6 melt. Separately, the wire 6 is fed to the molten pool while being heated by electric power supplied from the wire power source 8 via the tact tip 7, and the amount of welding is larger than in normal TIG welding in which the wire 6 is not heated. is obtained. However, the wire current cannot be made very large because the arc 5 is interfered with when the wire 6 is energized, causing magnetic blow. A hot wire switching TrG (hereinafter abbreviated as H8T) welding method is available as a method for reducing the influence of the magnetic blow of the arc 5 and increasing the welding R.

This is a method in which the arc current Iα is pulsed as shown in FIG. 9, and the wire 6 is exposed only during the base period when the current is low, thereby reducing the influence of magnetic blowing.

fl ST A V OI to keep the arc length constant in T welding
When performing J control, since the arc current is a pulse current, it is necessary to perform AvC control by selecting the base time (Tz) or the peak time T of the arc current factor α, as described above. During the base period α2) of the arc current α, the heating current Iw is applied to the wire 6, causing magnetic blowing of the arc 5, and it is possible to control the arc length by making the voltage at this time correspond to the arc length. Very difficult. On the other hand, the voltage during the peak period 11J (Tz) of the arc current flow α has a tendency 3 to suddenly increase at the rise of the current and then gradually decrease.

This is a waveform when a transistor chopper-controlled power source is used as the welding power source, but this tendency remains the same in Ike's H8T power source, and the voltage during the peak period also has difficulty in corresponding to the arc length.

In this way, in H8T welding, it is difficult to accurately match the voltage and arc length during both the base period and the peak period.
Conventional ATO devices cannot perform stable arc length control.

[Purpose of the invention]

The present invention aims to eliminate such conventional drawbacks,
The purpose of this is to determine the shape and diameter of the tungsten electrode.
The purpose of the present invention is to control the arc length to be approximately constant even if welding conditions such as the shielding gas flow rate and the material of the base metal change. An arc voltage control device is provided which uses the arc voltage after a certain period of time has elapsed since the rise of the arc voltage as a reference voltage, and the tungsten electrode is moved up and down based on this reference voltage.

[Embodiments of the invention]

Figure 1 is a configuration diagram of the H8T welding device according to the present invention, Figure 2 is a diagram explaining the touch start method, and Figure '5 is a diagram of the H8T welding device according to the present invention.
A diagram showing changes in arc voltage during T welding, Figure 4 is A
40 is a block diagram of the control device, FIG. 5 is a diagram showing the change in arc voltage obtained by the AVO control device in FIG. 4, FIG. 6 is a diagram explaining the movement of the relay due to the arc voltage, and FIG. It is a diagram of the family of guns to be controlled.

First, in FIG. 1, numerals 1 to 12 are the same as the conventional ones, 16 is an ATO device, 14i, fAVO
A motor driven by device i'213 moves the torch 4 up and down.

In Fig. 1, the arc voltage is measured at the arc length l just before the arc 5 is generated and the welding head shown in Fig. 1 starts to move, and this voltage 'f: A is used as the reference voltage of AVo.
It is stored in the VO device 13. At this time, the reference voltage is 0.
The influence of power supply ripple is removed by measuring the average voltage for 1 to 1.0 seconds.

Once the head has moved and welding has started, adjust the torch 4 so that the difference between the reference voltage and the arc voltage during welding is within a certain range.
The t-ATO drive motor 14 moves it up and down and controls the arc length to be constant.

In this method, the arc voltage at a preset torch height is measured and used as the reference voltage, so there is no need to experimentally determine the relationship between the arc length, current, and voltage as in the conventional method. Therefore, even if the electrode diameter and shape are changed depending on the purpose of welding, or the shielding gas flow rate, base material material, or other welding conditions change, the set arc length can be maintained without being affected by these changes, increasing reliability. .

Arc start methods for TIG welding include a high frequency start method in which a high voltage and high frequency is applied to generate an arc 5, and a touch start method in which an arc 5 is generated by bringing the tungsten electrode 1 into contact with the shell base material 2 and pulling it away again. There is. In the former case, since an arc is generated at the torch height set before welding, the voltage at this arc length is used as the reference voltage of the AVO. In the latter case, it is difficult to determine the arc length because the torch 4 moves when the arc starts, but the method is shown in FIG.

FIG. 2(α) shows the state before welding, FIG. 2(b) shows the state where the tungsten electrode 1 is in contact with the base metal 2, and FIG. 2(c) shows the state where the arc 5 is generated.

The torch 4 starts to descend from the state before welding at No. 312J(α), and when the tungsten electrode 1 contacts the base material 2 and a current is generated, the torch 4 stops as shown in FIG. 12(b). Next, the torch 4 rises, but at this time, the torch 4 is stopped by the amount of rise so that the arc length becomes the set arc length. That is, the Do motor 14 shown in FIG. 1 is used to move the torch 4 up and down, and by controlling the rotational speed or driving time of the motor 14, an arbitrary arc length l can be obtained mechanically.

After the arc length l is determined and the molten pool is in a stable state, the arc voltage is measured and used as a reference voltage to control the arc length.

FIG. 6 shows the reference voltage used in the H8T welding method.

When the arc 5 starts, the arc length reaches a predetermined length, and switching starts, the average value of the voltage during the arc voltage measurement period T8 shown in FIG. 6 is measured.
The reference voltage Vg of 3 is assumed to be Vg. Furthermore, during welding, the average voltage during the arc voltage measurement period T'g is compared with the carefully set reference voltage v1, and by moving the torch 4 up and down so that this difference falls within a certain range of 1ffi, stable arc length control can be achieved. can be carried out.

The reason why the arc voltage is measured only during the arc voltage measurement period Ts and not during the entire arc energization period Tα is because the period (Tα-Tg) immediately after the current is switched from wire 6 to tungsten '211 pole 1 (Illll) is abrupt. This is because the voltage increases and the measured values fluctuate significantly, making arc length control unstable.

FIG. 4 shows a block diagram of the AVC device 16. The arc voltage is taken from J in Figure 4 and applied to voltage divider 1.
5. After being amplified by the amplifier 17 through the noise filter 16, the voltage ripple is removed through the low-pass filter 18. On the other hand, this voltage waveform is shaped by the timing waveform for voltage measurement, and the voltage is measured at a certain time delay from the rise of arc 1 (Tα-Ts in Fig. 6). Compare the voltages with funparators 19, 20, and 21, and compare the voltages with relays 22, 23,
．． Move 24. In conjunction with this, relay 26°27.2
8 is activated, the relay 26 raises the torch 4 and the relay 27 lowers the torch 4.

In addition, the relay 28 is connected to the AVO device 13'fi:0N10
It is a relay that goes FF.

In short, the AVO device 1 performs AVO control by measuring the voltage at a time when the arc voltage is relatively stable.

FIG. 5 shows the voltage waveform at each position of the J-N point in the block diagram of FIG. , the fifth point is passed through the low-pass filter 18.
The arc voltage waveform is shown in Figure (b). From the arc voltage waveform at this point, the reference waveform of the timing waveform shown in FIG. 5(6) is shaped by waveform shaping 29. At point M in Figure 4,
The waveform f of @5rIIJ(d) is created by the one-shot 30 which is delayed by a certain time T (1 to 10 m5ec) from the rise of the timing waveform of FIG. 5(c),
At point N in FIG. 4, the sample-and-hold signal is outputted by the sample-hold 25 by the one-shot 31 at the falling edge of FIG. 5(d), and the arc voltage shown in FIG. 5(6) is held. That is, by always measuring the voltage after a certain period of time (Tα-Tg) has elapsed since the rise of the waveform of the pulsed arc voltage, drastic voltage changes due to switching can be absorbed.

The voltage measured at the timing of 5th FXJ (e) is compared with the reference voltage by comparators 19, 20.21 and operates the relays 22, 23.24, but Figure 6 shows the state of the relays. be.

The sampled and held measurement voltage V1 reference voltage is Vj
Then, in the funparator 19, (V-Vs)〉
When ΔV(7), the relay 22 is turned on. ΔV is the voltage margin when moving the torch 4 up and down, and is usually 0.1 to 0.
．． 5(7). In the comparator 20, (V-Vg
)≧0, the relay 23 is turned on. Comparator 2
1 turns on the relay 24 when (V-Vs)<, -ΔV(7).

FIG. 7 is a diagram illustrating the movement of the relays 26°27.28 which move the torch 4 up and down in accordance with the movement of the relays 19 to 21. In this figure, relay 26 raises the torch 4, relay 27 lowers the torch 4, IJ lz
-2F3 is a relay for AYO device 13t-ONloFF. When the measured voltage V is low and the relays 22, 23.24 are all OFF, the contacts 33.34 are closed, so the relay 26 is turned ON and the torch 4 is raised.

As the torch 4 rises, the measured voltage V increases and the relay 24
When turned on, the contact 34 opens, but the contact 65 remains closed, so the torch 4 continues to rise.

When the relay 23 is turned ON, the contacts 33 and 34 are opened, the relay 26 is turned OFF, and the torch 4 is stopped. When the measured voltage V further increases, the relay 22 is turned on, contacts 32 and 33 are closed, the relay 27 is turned on, and the torch 4 is lowered. The lowering of the torch 4 continues until the measured voltage V becomes low and the relays 22, 23 are turned off. AvC
ON-OFF of the device 13 is performed by a relay 28. Therefore, for example, by connecting the relay 28 to a current detection terminal of a welding machine, A V CIIJ can be controlled only when an arc occurs.

〔Effect of the invention〕

In the present invention, an arc voltage control device is provided which uses the arc voltage after a certain period of time has elapsed from the rise of the arc voltage as a reference voltage, and the tungsten electrode is moved up and down based on this reference voltage. The arc length can always be controlled regardless of welding conditions such as diameter, base material material, etc., and stable arc length control is possible.

[Brief explanation of the drawing]

Figure 1 is a diagram of the H8T welding device according to the present invention, Figure 2 is a diagram explaining the touch start method, and Figure 3 is a diagram of the H8T welding device according to the present invention.
A diagram showing fluctuations in arc voltage during welding, Figure 4 is Av
A block diagram of the C control device, Figure 5 is a diagram of changes in arc voltage obtained by the ATO device in Figure 4, Figure 6 is a diagram explaining the movement of the relay due to arc voltage, and Figure 7 is a diagram that controls the movement of the torch. No. 8 r Basic diagram of wire switching TIG welding, Figure 11 is a characteristic curve diagram of arc voltage and '1 flow in TIG welding,
FIG. 12 is a diagram showing changes in arc voltage due to differences in the shape of the tip of the electrode. 1...Tungsten electrode, 4...Torch, 13...
- AvC device, 14... motor, Vx... reference voltage. Fig. 1 Fig. 2 Fig. 3 □ Time Fig. 4 Fig. 5 Fig. 6 Fig. Ryo 7 Torch rising Fig. 10 Fig. 11 → t3 circle 1 (C)

Claims (1)

[Claims] In a device equipped with an arc voltage control device that measures the arc voltage during hot wire switching TIG welding and controls the arc length, arc voltage control using the arc voltage after a certain period of time from the rise of the arc voltage as a reference voltage. What is claimed is: 1. An arc length control device characterized in that a device is provided and a tungsten electrode is moved up and down based on the reference voltage.