JPS62282779A - Hot wire welding control method and welding equipment - Google Patents

Abstract

PURPOSE:To simplify a control device and curtail a manual operation by control ling the wire heating electric power of after fusing a wire with its overheating so as to repeat to set it lower than the heating power immediately before the wire being melted. CONSTITUTION:The control is performed so as to increase a welding current corresponding to the size of the input voltage by the welding phase control circuit 25 of the inside of a gate pulse forming circuit 20. A wire is welded by increasing the wire heating electric power. The voltage variation at this time is detected by a wire contact state detecting circuit 21 and the output voltage is reduced by the prescribed amount with a welding phase control voltage forming circuit 23 as well. The tip of the wire comes into contact with the base metal again and at the wire welding re-opening time the setting is made to the value slightly lower than the optimum heating power. The efficiency can be realized in this way.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to hot wire welding, and particularly to hot wire welding that allows welding to be performed with substantially no magnetic arc blowing. METHODS AND WELDING APPARATUS.

(Prior Art) FIG. 3 shows the configuration of a welding device that has been commonly used in the hot wire TIG welding method.

Tungsten electrode 2 and base material 3 in TrG welding tool 1
Connect the DC welding arc electric 'tA4 to the argon
An arc 5 is formed in a shielding gas using the tungsten electrode 2 as a negative electrode. An additive wire 6 for welding is guided from a wire feeding device 7 through a conduit 8 and a contact tip 9 connected thereto to an arc forming section and brought into contact with the base material 3.

The contact tip 9 and the wire heating power source 10 are connected, and direct current or alternating current is passed through the additive wire 6 to generate Joule heat, thereby increasing the melting rate of the additive wire 6.

By the way, it is known that in hot wire T I c welding, especially when the wire current is increased, electromagnetic force is generated between the wire and the arc current, which causes arc disturbance due to so-called magnetic blowing, making welding difficult. There is.

As a countermeasure, it is recommended to select the arc current as high as possible to increase the rigidity of the TIG arc, keep the wire heating current to 1/2 or less of the arc current, and heat the wire using alternating current rather than direct current. Good things are known as technical common sense and have been adopted since ancient times. However, in order to increase the wire melting speed, it is necessary to increase the wire current, so if you choose an appropriate arc current for the workpiece and want to obtain a wire melting speed of, for example, 20 g/min, the arc length Unless the length is kept as short as possible, such as 1.5 m or less, magnetic blowing occurs, making welding work difficult.

Therefore, a method has been proposed (Japanese Patent Application No. 60-271343) in which a current having a pulse waveform as shown in FIG. 4 is passed through the wire. In this way, the wire heating current is made into a pulse current,
If the period in which the arc is continuously magnetically blown, that is, the period in which the wire current is continuously flowing, is made as short as possible, the arc will be blown instantaneously but will immediately return to the position directly under the tungsten electrode, which will essentially stiffen the arc. The properties are maintained, and no deterioration in workability due to magnetic blowing is observed. This results in
The workability of hot wire TIG welding has been significantly improved, and its practical application has progressed.

The additive wire 6 is electrically heated at the 0 part of the extension 93 between the contact tip 9 and the base material 3, and it is necessary to control the electric power applied thereto and the amount of wire melting to be balanced. The optimum melting state of the doped wire 6 in hot wire TlG1 contact is that the doped wire 6
The tip of the wire is brought into contact with the molten pool 11, but the wire is already completely melted very close to the contact interface. Most preferably, the additive wire 6 is connected to the molten pool 1.
1. The metal must be completely melted just before it enters 1, and the molten metal must be able to drip continuously without breaking. In such a case, the melting of the wire and the molten pool 1
The transition to full melt bending to 1 progresses as if pouring hot water from a kettle, and a good weld bead 12 is formed. Also,
When the wire heating power is too low relative to the wire feeding speed, the wire penetrates deeply into the molten pool 11 on the base material 3 and is finally melted by heat transfer from the molten metal in the molten pool 11. Welding will proceed in this condition, which is not a very desirable condition. If this control is insufficient and, for example, heating power is insufficient, welding workability will not change in appearance, but as seen in the weld bead cross section shown in Fig. 5, unmelted wire 13 will It remains in the weld metal 14 and forms welding defects. In addition, if the applied load is excessive, the wire 6 will overheat and if the current is continued, spatter will be generated and the wire will be fused and cut into the base material 3.
Then, electricity is passed through the arc between the tip of the additive wire 6 and the base metal 3 or the tungsten electrode 2, causing phenomena such as disturbing the arc 5 and forming large droplets at the tip of the wire. , which will significantly impair welding workability.

By the way, conventional wire heating power control involves keeping the extension e as constant as possible during welding, observing the wire melting state during welding, and intuitively determining the appropriate wire current corresponding to the wire feeding speed. It was normal to continue welding work by keeping the current constant. However, this method has a problem in that when the extension e changes during welding, the resistance value there changes, so the amount of heat generated changes. Therefore, Japanese Patent Laid-Open No. 60-822788 proposed measuring the power applied to the extension e during welding and controlling the applied power to a value commensurate with the wire feeding speed. When the thermal influence from the arc 5 and the molten pool 11 is not considered, the wire melting speed is in principle proportional to the applied power, so the applied force is output in proportion to the wire feeding speed. In addition, the proportionality constant is adjusted during welding, so that even if the extension changes significantly or the wire feed speed changes over a considerable range, it can be automatically accommodated to a considerable extent. However, even in this case, determining the proportional multiplier that would result in the optimal heating state was still left to intuitive judgment during welding. In other words, overheating and fusing of the wire can be clearly observed from arc disturbances and spatter formation, so while welding, monitor the arc and adjust the applied power to the maximum that will not cause such disturbances to maintain the optimum melting state. This has been the easiest and most practical method to find.

(Problems to be Solved by the Invention) Even if the proper conditions are determined in this way and the intention is to maintain the conditions thereafter, in reality, the arc current, arc length, and addition wire 6 to the molten pool 11 are The amount of heat applied to the additive wire 6 from the arc 5 and the molten pool 11 changes depending on the insertion position and insertion angle, resulting in a slight change in the melting state, or deviation from the proper state due to changes in the applied power due to fluctuations in the power supply voltage, etc. often occurs. In this case, if the applied power deviates in the direction of excessive power relative to the wire feeding speed, it may generate a crackling sound, generate spatter, or disturb the arc, requiring readjustment during welding. Since it can be easily detected, although it is troublesome to re-tmm, if readjusted immediately, it will not result in a welding defect. However, if the applied power deviates in the direction of insufficient power, the apparent condition of the upper arc will hardly change, and since the change in condition cannot be detected during welding, welding will continue, as shown in Figure 5. Often, unmelted wire 13 remains in the deposited metal 14, creating weld defects. Particularly in narrow gap welding where it is often difficult to monitor the arc, unmelted wire tends to remain unmelted.

In order to prevent this, it is desirable to use a proportional constant fine adjustment dial as often as possible during welding to check whether the proper conditions have been deviated from. In other words, the conventional method requires checking as frequently as possible during welding whether or not the melting state is appropriate, and the judgment of whether or not the melting state is appropriate depends entirely on the feeling during welding. It was something.

The object of the present invention is to provide a means to solve the above-mentioned problems, that is, to improve the molten state of the additive wire 6 in real wire welding without requiring any operations during welding and without relying on sensation during welding. The object of the present invention is to provide a concrete means for completely automatically maintaining the system in an optimal state at all times.

(Means for Solving the Problems) The first aspect of the present invention is to provide a control method for a real wire welding device comprising an arc power source, a wire heating power source, etc., in which wire heating is performed after overheating and fusing the wire. The method is characterized in that the heating power is set lower than the heating power immediately before the wire melts, and the wire heating power is gradually increased from the set value again to cause the wire to overheat and melt.

This is a welding control method for twin wires.

The second aspect of the present invention is that in a real wire welding device consisting of an arc power source, a wire heating power source, etc., the wire heating power after overheating and fusing the wire is lower than the heating power immediately before the wire is melted. This hot wire welding apparatus is characterized in that it is equipped with a wire heating power control circuit that repeats setting the wire heating power and gradually increasing the wire heating power again from the set value to bring the wire to overheating and fusing.

Typically, in the wire heating power source of a hot wire welding device, after heating and fusing the wire, the wire heating power is set lower than the heating power immediately before the wire is fused, and the wire heating power is then turned on again. This is achieved by controlling the wire heating power in a manner that gradually increases from that value until the wire reaches overheating and fusing.

(Function) When the wire heating power is slightly excessive with respect to the wire feeding speed, the additive wire 6 is overheated and the molten pool 11 on the base material 3 is heated.
The base material 3 and the additive wire 6 are melted just before entering the wire.
and are separated. At this time, if the wire current is flowing, spatter will be generated with a cracking sound, and the tip of the additive wire 6 is exposed to the plasma column of the arc 5 and is also in a position extremely adjacent to the molten pool 11. , a current flows between the tip of the additive wire 6 and the molten pool 11 or the tungsten electrode 2, which causes the tip of the wire to melt rapidly, forming large droplets at the tip of the wire, and also violently disturbs the arc. This makes it difficult to continue welding work. These phenomena that significantly impair weldability occur because the wire current continues to flow even immediately after the wire is fused. Therefore, a power source that outputs a pulse current as shown in Fig. 4 is used as the wire heating power source, and the control means of Japanese Patent Application No. 61-030649 is used to check whether the wire is in contact with the base material during the applicable period when the wire is not energized. If the wires are in contact, the wire is energized during the next energization period, and if there is no contact, the wire is not energized even in the next energization period. Since the tip of the doped wire 6 is simply exposed to the plasma column without continuously forming an arc, the progress of melting is extremely slow. The tip contacts the molten pool 11 again as it is without forming a large droplet. After confirming that the tip of the additive wire 6 has contacted the molten pool 11, the wire current is restarted.
Repeat heating and fusing again. In this way, there is less disturbance of the arc, and although a few fine spatters are formed during arc fusing, they do not reach the point where they actually interfere with welding work, so that the tip of the additive wire 6 is placed in the molten pool 1.
Complete melting of the wire near the interface where it contacts 1 can proceed smoothly.

(Example) FIG. 1 shows an example of a wire heating power source and control circuit according to the present invention. In this embodiment, a triac system, which can be constructed at a very low cost, is used as a wire heating power source that outputs a pulse current.

This is used as the wire heating power source 10 of the components of the hot wire TTG welding apparatus shown in FIG.

In this embodiment, there is a triac on the primary side of the main transformer 150.
6 is connected, and a diode 17.6 is connected to the secondary side of the transformer 15.
18 is connected to a wire heating current forming circuit 19 which performs full-wave rectification and outputs the result.

In this circuit, the triac 16 is controlled by the gate pulse forming circuit 20, and a wire current obtained by controlling the phase of the commercial frequency AC power source is obtained. The gate pulse application to the triac 16 is controlled so that the period from 180 degrees to 270 degrees is always a non-current period. The phase control angle for energizing the triac 16 is the remaining 90
The wire is heated between 180 degrees and 270 degrees and 360 degrees, and the wire is energized to obtain wire heating power commensurate with the wire feeding speed.

By the way, the wire terminal voltage (output terminal voltage) indicated by Vw when the wire is not energized is approximately oV when the wire is in contact with the base material, and when the wire tip is separated from the base material and comes into contact with the arc plasma. When the voltage of the plasma column is detected, the voltage becomes more negative than -1■. A wire contact state detection circuit 21 for detecting whether the tip of the wire 6 is in contact with the base material 3 was constructed by the circuit disclosed in Japanese Patent Application No. 61-030649 that utilizes this property. The output voltage Va becomes an L level voltage when the wire is in contact with the base material and when the wire is separated by H1.

This signal is 0N-O in the gate pulse forming circuit 20.
It is applied to the FF control circuit 22, and operates so as not to form the next energizing pulse when the wire is out of contact.

On the other hand, the energization phase control voltage forming circuit 23 receives the output voltage Va of the wire contact state detection circuit 21 and a signal from the voltage gradual increase speed/voltage drop width setting circuit 24, and receives the signal from the energization phase control circuit 25 in the gate pulse forming circuit 20. The voltage ■b that determines the energization phase of the triac is output. This voltage vb gradually increases when the voltage Va is H, that is, when the wire is in contact with the base material, and decreases by a predetermined value when the voltage Va becomes L, that is, when the wire leaves the base material. I try to do that.

FIG. 2 schematically shows the temporal changes in these voltage signals and output current. The energization phase control circuit 25 in the gate pulse forming circuit 20 controls the firing angle so that the energization current increases in accordance with the magnitude of the input voltage vb. As the applied current increases, the wire heating power determined from the resistance in the extension e and the current applied to it naturally increases, and when the applied wire heating power increases compared to the wire feed rate, the wire becomes overheated and Fuse it like a fuse blows.

When the wire is fused, it separates from the base metal, so the V
The wire contact state detection circuit 21 detects the lightning voltage change and sets the output Va to L. As a result, wire energization is prohibited, and the energization phase control voltage forming circuit 23 lowers the output voltage vb by a predetermined amount. Then, when the tip of the wire 6 comes into contact with the base material again and the voltage Va becomes H and the wire energization is resumed, the electric power applied to the wire is adjusted to the optimum heating required in accordance with the wire feeding speed. It is set to a value slightly lower than the power.

Because it operates in this way, when the wire feeding speed slows down during welding, the wire tends to overheat, which causes the wire to melt frequently and gradually lower the voltage Vb, resulting in a reduction in the wire heating power. . On the other hand, when the wire feeding speed increases, the wire heating power tends to be insufficient, so wire fusing does not occur, but then the v
energization phase control voltage forming circuit 2 so that b gradually increases.
3 operates, so eventually the wire heating power continues to increase,
Eventually, it will melt.

It functions similarly even if the wire extension e changes. In other words, if the extension is long (the resistance value there increases), and when the wire heating power source has constant voltage output characteristics, if the current phase is constant, the peak value of the current will be lower, the output power will decrease, and it will be difficult to cause a blowout. vb increases and functions to increase the energizing phase, and as a result, the heating power is kept at the original value commensurate with the wire feeding speed.On the other hand, if the extension is short (if the extension is short), the resistance value decreases and the same energizing phase is maintained. The peak value of the current increases, resulting in excessively applied power, which tends to cause fusing (and each time a fusing occurs, the voltage vb decreases and the energization phase becomes smaller, and as a result, the original heating power commensurate with the wire feeding speed) is maintained.

The width by which vb decreases each time a melt blows, or gradually after that, vb
The rate at which the voltage is increased is determined by selective adjustment using an adjustment volume provided in the voltage gradual increase rate/decrease width setting circuit 24 so as to obtain an appropriate value before or during welding.

In this way, the wire heating power during welding is controlled to follow changes in the wire feeding speed and extension, so it can always be automatically maintained at a value extremely close to the appropriate wire heating power. Ta.

In the apparatus shown in FIG. 1, the period at which the wire melts due to overheating is determined mainly by the increase/decrease state of the power applied to the wire and the wire feeding speed. This overheating of the wire may be accompanied by spatter, although it is very small, so it is desirable to reduce the frequency of this occurrence if possible. Therefore, when it is necessary to respond immediately to rapid changes in the wire feeding speed or the wire tension, increase the rate of increase and decrease width of the voltage vb to increase the frequency of wire fusing, and It is also possible to reduce the frequency of overheating and melting of the wire by reducing the increase rate and decrease width of the voltage vb when the change in the extension does not occur much. The increase/decrease status of the power applied to this wire is
Usually, it is determined by manually adjusting the volume of the voltage gradual increase speed/decrease width setting circuit 24 before and during welding. However, this adjustment specifies the cycle at which the wire overheats and melts, and when the cycle of melting that actually occurs is longer than the specified value, the speed at which the wire heating power gradually increases is increased; conversely, when the cycle is shorter than the specified value, This can also be done automatically by providing a circuit that controls the wire heating power so that the wire heating power gradually increases at a slower rate so that the period at which the wire overheats and melts approaches a specified value.

By the way, if a high wire current is flowing at the moment when the wire is overheated and fused, spatter is likely to be formed.
Spatter is not formed when a relatively low wire current, such as less than A, is flowing, or when no current is flowing. Therefore, when using a wire heating power source that outputs a pulsed current, a circuit is provided to control the wire so that the overheating and fusing of the wire occurs during the wire current stop period or the period immediately before the wire current is sufficiently low. Spatter formation can be significantly reduced. This can be achieved by specifying the cycle of wire overheating and blowing out, and by controlling the wire so that the blowout occurs just at the beginning of the wire energization stop period. In the case of a wire heating power supply using a triac as shown in Figure 1, for example, after the wire separates from the base material due to overheating and melting, the tip of the wire comes into contact with the base material again, and this contact is detected. A preset counter counts the number of energization pulses from when the wire energization resumes until the next fusing occurs, and if the count exceeds the precent value, the heating power is increased slightly. Conversely, if the count does not reach the precent value, the heating power is controlled to be slightly reduced. When controlled in this way, a blowout occurs just before the preset number of pulses ends, that is, after the instantaneous value of the wire heating current becomes 100 A or less, or when the pulse current is completed and the wire current is O. It became like this,
Spatter will not be generated at all during overheating and melting. Usually 6
With a 120 Hz pulse current obtained by full-wave rectification of a 0 Hz power supply frequency, a wire with a diameter of 1.2 mm is
When delivering at speeds near /min, 6 to 30 pulses are preset. If this preset value is too large, the instability of the wire melting phenomenon will easily cause fusing even when the instantaneous value of the wire current is high.If this preset value is too short, the wire feeding speed will be relatively slow. This is because it cannot cope with a case where the heating power is small.

Furthermore, the method of appropriate heating power control using the overheating phenomenon according to the present invention is applicable to conventional heating power control, that is, a control device that outputs wire heating power in proportion to the wire feeding speed. It goes without saying that the proportionality constant can be gradually increased over time to cause wire overheating and melting, and then being reset to the value of the proportionality constant immediately before the wire overheating and melting occurs. Although this makes the control device considerably more complex, it has the advantage of further improving its responsiveness, particularly to sudden changes in extension and wire feed speeds.

So far, we have mainly described a wire heating power source using a triac, but the wire heating power source is not limited to this type, and may be a wire heating power source using other circuit types such as an impark type using a transistor. Moreover, it goes without saying that the present invention is not limited to pulse current, and can also be applied to, for example, a continuous DC current power source.

(Effects of the Invention) According to the present invention, there is almost no need for human operations to maintain the optimum wire heating power state in hot wire welding. In other words, welding condition factors in hot wire welding include wire material, wire shape, wire feed speed, wire extension, arc current, arc length, wire insertion position and insertion angle, and all of these condition changes (, it becomes possible to always maintain an appropriate wire heating power state stably and automatically. This allows
In particular, it is possible to completely eliminate defects caused by unmelted wire remaining in the weld metal as shown in FIG. 5, which is said to be very likely to be formed in hot wire welding. In addition, since it automatically maintains the appropriate heating power in response to such various changes in welding conditions, semi-automatic hot wire welding, which was previously quite difficult to perform, is now extremely easy to perform. Can be done.

In addition, in the conventional control method that supplies wire heating power commensurate with the wire feeding speed, the wire feeding speed detecting device uses an electric power composed of a Hall element etc. to detect the wire heating power. A detection device was required. In addition, in order to obtain the most accurate heating power possible, it is necessary to detect the wire voltage as close as possible to both ends of the extension, making the wiring cumbersome during welding work. However, according to the present invention, there is no need to detect the wire heating power, and it is only necessary to detect the output terminal voltage of the wire heating power source instead of the voltage across the extension, so the control device becomes very simple. , can be constructed at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a circuit configuration of a wire heating power source and its control circuit according to the present invention, FIG. 2 is a diagram explaining control in an embodiment of the present invention, and FIG. 3 is a diagram showing a conventional hot wire TIG. FIG. 4 is a diagram showing the equipment configuration of the welding device.
A diagram showing a wire current waveform of a conventional wire heating power source,
FIG. 5 is a diagram showing a cross section of a weld bead. 15...Main transformer, 16...Triac, 17
．． 18... Diode, 19... Heating current forming circuit, 20... Gate pulse forming circuit, 21... Wire contact state detection circuit, 22... -0N-OFF control circuit,
23... Energization phase control voltage forming circuit, 24... Voltage gradual increase speed and decrease width setting circuit, 25... Energization phase control circuit. Agent Patent Attorney Takenaga Kawakita Figure 3 Figure 4 Figure 5

Claims (5)

[Claims] (1) In a method of controlling a hot wire welding device consisting of an arc power source, a wire heating power source, etc., the wire heating power after the wire is overheated and fused is set to be lower than the heating power immediately before the wire is fused. A hot wire welding control method characterized by repeatedly increasing wire heating power gradually from the set value again to bring the wire to overheating and fusing. (2) In a hot wire welding device consisting of an arc power source and a wire heating power source, the wire heating power after overheating and fusing the wire is set lower than the heating power immediately before the wire melts, and then the wire is heated again. A hot wire welding device comprising a wire heating power control circuit that repeatedly increases wire heating power from a set value to bring the wire to overheating and fusing. (3) In claim 2, when the period in which the wire overheats and melts is longer than a specified value, the speed at which the wire heating power gradually increases is increased, and when it is shorter, the speed at which the wire heating power gradually increases is slowed down. 1. A hot wire welding device comprising: a circuit for controlling wire heating power so that the period at which the wire overheats and melts approaches a specified value. (4) In claim 3, using a wire heating power source that outputs a pulse current based on a control signal from a circuit that determines a wire energization suspension applicable period and a wire energization applicable period, which serve as a reference as a wire heating power source, 1. A hot wire welding device comprising a circuit for controlling overheating and fusing of the wire to occur when the instantaneous value of the wire current is 100 A or less or during a period corresponding to the period when the wire is not energized. (5) In any one of claims 2 to 4, the wire heating power is output in proportion to the wire feeding speed, and the proportionality constant is gradually increased as time passes. A hot wire welding device characterized by causing overheating and then resetting the proportional constant value to the value immediately before the wire overheating and cutting occurred.