JPS6260194B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic arc welding control method.

In an automatic arc welding apparatus, for example, a vertical electrogas arc welding apparatus, as shown in FIG. The motor 4 feeds the welding wire 5 to the tip 3 at a speed corresponding to the welding voltage, while the head driving motor 6 and chain 7 feed the welding wire 5 along the groove 8a of the base material 8. It is known that both the head 2 and the dowels 9 are raised to automatically weld the groove 8a of the base material 8.

Note that when the welding power source 1 has constant voltage characteristics, the welding wire 5 is fed to the tip 3 at a constant speed.

In the above vertical electrogas arc welding apparatus, welding is started by bringing the tip of the welding wire 5 protruding from the chip 3 into contact with the surface of the groove 8a of the base material 8 for a suitably short time, that is, by short-circuiting the welding wire 5. The wire 5 and the contact portion between the wire 5 and the groove 8a are heated and melted, and the tip of the welding wire 5 and the groove 8a are bonded together.
This is done by generating a welding arc between the

In the automatic arc welding apparatus described above, the relationship between the welding current and the wire feeding speed, that is, the wire melting speed, is determined by the protruding length of the welding wire 5 from the tip 3, the so-called extension, as shown in FIG. It is shown as a curve with l ₁ , l ₂ , and l ₃ as parameters. In FIG. 2, the size relationship of extensions l ₁ , l ₂ , and l ₃ is l ₂ <l ₁ <l ₃ .

Conventionally, as shown in Fig. 3, using the characteristic curve in Fig. 2, the amplification factor α was varied based on the detected value _I1 of the welding current, for example, by using a differential amplifier, etc. The welding current signal V ₁ =α(I ₁ −I ₀ ) is compared with the wire feeding speed signal V ₂ representing the feeding speed v of the welding wire 5 to the chip 3, and the welding current signal
When V ₁ exceeds the wire feed speed signal V ₂ , a high-speed drive command is given to the motor 6 to raise the welding head 2 at high speed, and conversely, the welding current signal V ₁ exceeds the wire feed speed signal When the voltage drops below V ₂ , a low-speed drive or stop command is given to the motor 6 to raise or stop the welding head 2 at a low speed, thereby keeping the extension at a constant length that matches the welding conditions during welding. The tip of the welding wire 5 and the groove 8 of the base material 8 are
A welding control method is known that performs so-called extension control, in which the gap with the surface of a is automatically adjusted to an appropriate distance.

However, in the automatic arc welding device described above, when welding is started after short circuiting as described above, due to the drooping characteristic of the welding power source 1,
The welding current hardly changes, while the welding voltage becomes almost zero. Therefore, the wire feeding speed is also approximately zero. This corresponds to a state in which the welding operation point A, which meets the welding conditions, has moved to the operation point C in FIG. 2. Therefore, in the comparison circuit shown in FIG. 3, it is determined that the welding current signal V ₁ exceeds the wire feed speed signal V ₂ , and therefore, a high-speed increase command is issued to the motor 6 to start welding. Head 2 and cash 9,9 are
As it ascends at high speed, the extension becomes larger.

On the other hand, when the welding power source 1 has constant voltage characteristics, the welding wire 5 is fed at a constant speed when the welding start described above is performed, so the wire feeding speed does not change. The welding power source 1 having constant voltage characteristics is brought into a short-circuited state, and therefore the welding current increases. This corresponds to a state in which the welding has moved from operating point A to operating point B in FIG. 2. That is, assuming that the extension of the welding wire 5 is shorter than the extension _l1 corresponding to the operating point A, in the comparison circuit shown in FIG. 3, the welding current signal _V1 is the wire feed speed signal.
It is determined that the voltage exceeds V ₂ , and the motor 6
A high-speed raising command is issued, and the welding head 2 and the welding pads 9, 9 move up at high speed, and the extension becomes larger. In addition, if there is no time for arc generation due to arc generation failure at the start of welding, the welding head will rise at a slow speed, which may cause the extension to become too long or create a gap at the lower end of the butts 9, 9. do. Arcing occurs in this state, resulting in poor penetration or spillage of molten metal.

The same thing occurs even when arc breakage occurs during welding.

The most common phenomenon at arc start is arc instability, that is, a phenomenon in which short-circuit conditions and no-load conditions occur alternately, which causes the same problems as described above.

In this way, regardless of whether the welding power source 1 has a drooping characteristic or a constant voltage characteristic, at the start of welding, the dowels 9 and 9 rise together with the welding head 2 at high speed. The molten metal spills from the lower end, and the extension of the welding wire 5 becomes longer, resulting in welding defects where penetration is insufficient, which requires more effort to repair the welding defect, and the efficiency of the welding work is low. There was a drawback.

This invention was made in order to solve the above-mentioned drawbacks, and when performing automatic arc welding while performing extension control, when the welding power source is in a short-circuited state or in a no-load state, the welding head, which is automatically run-controlled, is operated. By stopping the welding wire, the extension of the welding wire is suppressed from increasing, the welding arc is stabilized during the entire period from the start of welding to the end of welding, and the incidence of welding defects such as poor penetration is low, and The purpose of the present invention is to provide an automatic arc welding control method with high welding work efficiency.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 shows an example of a welding control circuit that can be applied to the welding apparatus shown in FIG. 1. In FIG. 4, the component shown surrounded by a dashed line is the same welding wire extension control circuit as that shown in FIG. 3.

In the above extension control circuit, 11
is a current transformer for detecting the welding current, and 12 is a differential amplifier with a variable amplification factor α. Based on the welding current detection signal I ₁ from the current transformer 11, the welding current signal V ₁ =
It transmits α(I ₁ −I ₀ ). Note that the amplification factor α(I ₁ −I ₀ ) is transmitted. Note that the amplification factor α is appropriately selected according to the predetermined extension, and the current I ₀ is determined based on the welding conditions, and corresponds to the coordinate value I ₀ on the horizontal axis in Fig. 2. It is.

13 is a detection circuit for the feeding speed v of the welding wire, and this detection circuit 13 receives, for example, the voltage between the armature terminals of the wire feeding motor 4 of the welding device, and detects the feeding speed v of the welding wire 5. A wire feed speed signal V ₂ representing the speed v is sent out.

14 is a comparison circuit, which compares the welding current signal V ₁ from the differential amplifier 12 and the wire feeding speed signal V ₂ from the detection circuit 13, and determines that the signal V ₁ >V ₂ When , welding head 2
When the signal V ₁ <V ₂ , a low speed rise command signal _{S 2 of} the welding head 2 is sent out.

Comparison circuit 14 of the above extension control circuit
The output command signals S ₁ and S ₂ are applied to the head drive control circuit 15.
Each time it receives the command signal S ₁ or S ₂ from the comparator circuit 14, it sends a drive command signal having a voltage level corresponding to the command via the normally open contact 16-1 of the relay 16 and the amplifier 17. The voltage is applied to a motor 6 for driving the head.

18 is a chip 3 that is supplied with power from the welding power source 1 of the welding apparatus, and is therefore a component, for example, for detecting the welding voltage applied between the tip of the welding wire 5 and the base metal 8. It is a pressure vessel.

19 is a first judgment circuit, 20 is a potentiometer for setting the allowable lower limit voltage V _L of the welding voltage, 21 is a second judgment circuit, and 22 is the allowable upper limit voltage V of the welding voltage.
This is a potentiometer that sets _H.

Only when the detected voltage signal V _x from the voltage divider 18 exceeds the allowable lower limit voltage signal V _L from the potentiometer 20, the first judgment circuit 19 passes the detected voltage signal _V The voltage is applied to the circuit 21. This second determination circuit 21 is similar to the first determination circuit 19.
The detected voltage signal V _x from potentiometer 2
The detected voltage signal V _x is applied to the relay 16 and the relay 16 is turned on only when the detected voltage signal V x is lower than the allowable voltage signal V _H from 2.

As the allowable lower limit voltage V _L , a voltage approximately equivalent to the welding voltage at which the welding arc is reliably ignited when the welding apparatus starts welding is selected.
Further, as the upper limit voltage _VH , an output voltage of the welding power source 1 having the above-mentioned drooping characteristic, in other words, a voltage approximate to the welding voltage under no load when the welding arc is extinguished is selected.

Note that when the welding power source 1 of the welding device has constant voltage characteristics, the voltage divider 18
is replaced, for example, with the above-mentioned shunt 11, and the potentiometer 20 is set to the allowable lower limit current I _L of the welding current, and the potentiometer 22 is set to the allowable upper limit current I _H of the welding current. do it like this.

The above allowable lower limit current I _L is a small current close to zero, corresponding to when the welding arc is extinguished.
As the allowable upper limit current _IH , a current corresponding to the welding current at the start of welding is selected.

Next, the operation of the welding control circuit having the above configuration will be explained.

It is assumed that the welding power source 1 of the welding device has a drooping characteristic.

The potentiometer 20 has an allowable lower limit voltage of welding voltage of, for example, 5V, and the potentiometer 22 has an allowable upper limit voltage of welding voltage of, for example, 5V.
For example, assume that 45V is set.

First, the welding head 2 is set at the welding start position of the groove 8a of the base material 8. Thereafter, the welding power source 1 is turned on, and the wire feeding motor 4 and the head driving motor 6 are turned on.

Now, it is assumed that the tip of the welding wire 5 protruding from the tip 3 of the welding head 2 is brought into contact with the surface of the groove 8a of the base material 8 for a short time, and a welding start operation is performed.

At the start of welding, the welding power source 1 is short-circuited via the tip 3, the tip of the welding wire 5, and the welding start portion of the groove 8a of the base material 8. Therefore, the detection voltage signal V _x of the welding voltage detected by the voltage divider 18 is approximately zero. Therefore, the first
The determination circuit 19 determines that the detected voltage signal V _x is smaller than the allowable lower limit voltage of 5 V, and the detected voltage signal V _x is not applied to the second determination circuit 21 , so the relay 16 is not excited. , the contact 16-1 of this relay 16 is opened.

Therefore, the head drive motor 6 is disconnected from the head drive control circuit 15, and the welding head 2 stops at the position set at the time of welding start described above. In other words, the welding head 2 does not move until the welding arc is reliably ignited, and therefore the dowels 9, 9 attached to the welding head 2 in conjunction do not move either. It is possible to reliably prevent the problem of molten metal spilling out from the bottom end of the machine.

Thereafter, the tip of the welding wire 5 protruding from the tip 3 of the welding head 2 and the groove 8a of the base material 8 that was in contact with the tip of the wire 5 are heated and melted, and the welding wire 5 A welding arc is ignited between the groove 8a of the base material 8 and the groove 8a of the base material 8. That is, the welding voltage between the tip of the welding wire 5 protruding from the chip 3 and the molten pool 8b generated in the groove 8a of the base material 8 is greater than the allowable lower limit voltage V _L and is greater than the allowable upper limit voltage V The voltage increases until it reaches a predetermined voltage that is smaller than _H and is suitable for the welding conditions.

When the welding voltage exceeds 5V and therefore the detection voltage signal V _x output from the voltage divider 18 exceeds 5V, the first determination circuit 19 determines that the detection voltage signal _V It is determined that the voltage is greater than 5V, and the first determination circuit 19 applies the detected voltage signal V _x to the second determination circuit 21 . The second determination circuit 21 determines that the detected voltage signal _{V x} is applied, the relay 16 is turned on, and its contact 16-1 is closed.

On the other hand, the extension control circuit has been operating since the start of welding, and a high-speed rise command signal S ₁ is sent from the comparison circuit 14 to the head drive control circuit 15.
Alternatively, a low speed increase or stop command signal _S2 is applied. Therefore, a drive command signal corresponding to the command signals S ₁ and S ₂ is outputted to the output terminal of the head drive control circuit 15.

Therefore, as mentioned above, contact 1 of relay 16
6-1 is closed, the head drive control circuit 15
A drive command signal corresponding to the command signal _S1 or _S2 is applied to the head drive motor 6 via the contact 16-1 and the amplifier 17, and the welding head 2 moves up at high speed or at low speed. Or stop. In this way, when the welding voltage of the welding device is within the range from the allowable lower limit voltage of 5V to the allowable upper limit voltage of 45V, based on the above-mentioned command signals S ₁ and S ₂ ,
So-called extension control is performed.

Thereafter, when the welding arc ignited as described above is extinguished for some reason, that is, the welding power source 1 is brought into a no-load state, the output voltage of the welding power source 1 increases. Therefore, the detected voltage signal V _x output from the voltage divider 18 also increases, and when the detected voltage signal V _x exceeds the allowable upper limit voltage of 45 V, the second determination circuit 21 sends the detected voltage signal V _x to the relay 16. The relay 16 is turned off and its contact 16-1 is opened. Therefore, the head drive motor 6 is cut off from the head drive control circuit 15, as in the case immediately after the welding start described above.
The motor 6 stops driving. Therefore, the welding head 2 stops at the welding position when the welding arc is extinguished.

In this way, in the welding control circuit, the welding voltage is set to the allowable lower limit voltage V _L corresponding to the short circuit state.
If the pressure is not within the range from V _H to the allowable upper limit pressure corresponding to the no-load condition, the motor 6
is disconnected from the head drive control circuit 15 and therefore from the extension control circuit. Therefore, the extension control circuit does not act on the welding apparatus in a short-circuit condition and in a no-load condition in which the welding arc is inadvertently extinguished.

Note that even when the welding power source 1 has constant voltage characteristics, as described above, based on the detected current signal _I By controlling the relay 16 via the first judgment circuit 19 and the second judgment circuit 21 in the same manner as in the case, the welding current changes from the allowable lower limit current I _L corresponding to the no-load condition to the short-circuit condition. When the current is not within the range up to the allowable upper limit current _IH , the motor 6 can be disconnected from the extension control circuit.

In addition, a delay timer (not shown) is used in place of the contact 16-1 of the relay 16, and the time from the start of welding until the welding arc is stably ignited is set in the delay timer. You may also do so. In this way, the operation of the extension control circuit can be stopped at the start of welding, that is, when the welding power source 1 is in a short-circuited state.

Note that the automatic arc welding equipment to be controlled by the welding control circuit is not limited to the vertical electrogas welding equipment described above, but also includes, for example, a CO ₂ downward automatic welding equipment, a submerged arc welding equipment, etc., in short, a welding head or The present invention may be an automatic arc welding device that automatically feeds a welding wire to a welding torch and automatically performs arc welding while automatically moving the welding head or welding torch.

As explained above, according to the present invention, arc welding is automatically performed while controlling the traveling speed of the welding head so that the extension of the welding wire is kept approximately constant during welding, and the welding current is Or, when the detected value of the welding voltage is not within the range from the lower limit value to the upper limit value determined depending on the short-circuit state and no-load state of the welding power source, the welding head stops running; By increasing the extension of the welding wire when the welding power source is short-circuited or under no load, the risk of welding arc becoming unstable and poor penetration can be reduced. , has the excellent advantage of increasing the efficiency of welding work.

In particular, when performing vertical electrogas arc welding, if the control method of the present invention is used, it is possible to reliably prevent molten metal from falling from the lower end of the welding metal when the welding power source is short-circuited.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main components of a vertical electrogas welding device that can use the welding control method of the present invention, and FIG. 2 is a diagram showing the relationship between welding current and wire feeding speed in an automatic arc welding device. of,
FIG. 3 is a block circuit diagram showing a conventional extension control circuit, and FIG. 4 is a diagram showing an example of a welding control circuit using the control method of the present invention. DESCRIPTION OF SYMBOLS 1... Welding power source, 2... Welding head, 3... Chip, 4... Motor for wire feeding, 5... Welding wire, 6... Motor for driving head, 8... Base material, 8a... ...Bevel, 8b... Molten pool, 9... Welding metal, 11... Current transformer, 12... Differential amplifier, 13
...Detection circuit, 14...Comparison circuit, 15...Head drive control circuit, 16...Relay, 18...Voltage divider for detecting welding voltage, 19...First judgment circuit, 2
0...Potentiometer, 21...Second judgment circuit, 22...Potentiometer, _l1 , _l2 , _l3 ...
extension.

Claims (1)

[Claims] 1. Detect the welding wire feeding speed and the welding current, and based on these two detected values,
In an automatic arc welding control method that keeps the extension of the welding wire almost constant by controlling the traveling speed of the welding head, the welding current or welding voltage is detected, and the detected value is used to determine whether the welding power source is short-circuited. and an automatic arc welding control method, characterized in that traveling of the welding head is stopped when the welding head does not exist within a range from a lower limit value to an upper limit value set for determining a no-load state.