JPH0575512B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to hot wire welding, and more particularly to a hot wire welding method and a welding apparatus that allow welding to be performed with substantially no magnetic arc blowing.

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

An arc power source 4 for DC welding is connected to the tungsten electrode 2 and base metal 3 in the TIG welding torch 1, and an arc 5 is formed in an argon shielding gas with 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 metal 3. The contact chip 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 heat, thereby causing the additive wire 6 to heat up.
The melting rate is increased.

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

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 less than 1/2 of the arc current, and heat the wire using alternating current rather than direct current. Good things are known as technical common sense,
It has been used since ancient times. However, in order to increase the wire melting speed, the wire current must be increased, so choose an appropriate arc current for the workpiece, and set the arc length to 1.5 mm to obtain a wire melting speed of 20 g/min, for example. If the welding length is not kept as short as possible, magnetic blowing will occur, making welding work difficult.As a result, its practical use was limited to a limited range.

Therefore, there is a method in which a current with a pulse waveform as shown in Fig. 4 is passed through the wire (Japanese Patent Application No. 60-271343
-130773) has been proposed. In this way, if the wire heating current is made into a pulse current and the period in which the arc is continuously blown magnetically, that is, the period in which the wire current flows continuously, is shortened as much as possible,
Although the arc is momentarily blown, it immediately returns to just below the tungsten electrode, so that the rigidity of the arc is substantially maintained, and there is no decrease in workability caused by magnetic blowing. As a result, 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 extension e between the contact tip 9 and the base material 3, and it is necessary to control the electric power applied thereto to balance the amount of wire melting. The optimal melting state of the additive wire 6 in hot wire TIG welding is when the tip of the additive wire 6 contacts the molten pool 11, but the wire is already completely melted very close to the contact interface. be. Most preferably, the additive wire 6 is completely melted just before entering the molten pool 11, and the molten metal is maintained in a state where it melts down continuously without cutting. In such a case,
The melting of the wire and the transfer of molten metal to the molten pool 11 proceed like pouring hot water from a kettle, and a good weld bead 12 is formed. In addition, when the wire heating power is a little low relative to the wire feeding speed, the wire penetrates deeply into the molten pool 11 on the base material 3 and then receives heat transfer from the molten metal in the molten pool 11. Welding will proceed in a molten state, which is not a very desirable state. If this control is insufficient, for example, when heating power is insufficient, the welding workability will not change much in appearance, but as shown in the cross section of the molten bead shown in FIG.
4 and forms welding defects. In addition, in the case of excessive applied power, the wire 6 is overheated and if the current is continued, spatter is generated and the wire is fused and separated from the base material 3, and the tip of the additive wire 6 and the base material 3 or the tungsten electrode 2 are separated from each other. Disturb the arc 5 by passing current through the arc between the
Phenomena such as the formation of large droplets at the tip of the wire occur, significantly impairing welding workability.

By the way, the conventional control of wire heating power is to keep the extension e as constant as possible during welding, and the welder observes the wire melting state and intuitively determines the appropriate wire current corresponding to the wire feeding speed. It was common practice to continue welding by keeping the wire 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, in JP-A No. 60-822788,
It has been proposed to measure the power applied to the extension e during welding and to control 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 power is output in proportion to the wire feeding speed. At the same time, the proportionality constant is adjusted by the welder, 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, it was still up to the welder's intuitive judgment to determine the proportional multiplier that would result in the optimal heating state. In other words, overheating and fusing of the wire is clearly observed from arc disturbances and spatter formation, so the welder monitors the arc and adjusts the applied power to the maximum that will not cause such disturbances to achieve 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 condition is maintained thereafter, the arc current, arc length, and addition wire 6 to the molten pool 11 are actually 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, and the melting condition changes to some extent, or due to changes in the applied power due to fluctuations in the power supply voltage, etc. Deviations from the state often occur. In this case, if the applied power deviates too much relative to the wire feeding speed, it may cause crackling noises, spatter, or disrupt the arc, requiring the welder to readjust it. Since it can be easily detected, readjustment is troublesome, but 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 arc situation will hardly change, and the welder will not be able to detect the change in the situation and will continue welding. Unmelted wire 13 remains in the deposited metal 14, resulting in welding defects.
Particularly in the construction of narrow gap welding where it is often difficult to monitor the arc, residual unmelted wire tends to occur very easily.

In order to prevent this, it has been desirable for welders to use the proportionality constant fine adjustment dial as often as possible during melting to check whether the proper conditions have been deviated from. In other words, the conventional method requires the welder to check as frequently as possible to see if the melting conditions are appropriate.
Furthermore, the judgment as to whether or not the welder was in proper condition depended entirely on the senses of the welder.

The object of the present invention is to provide a means for solving the above problems, that is, without requiring any operations from the welder, and without relying on the welder's senses.
The object of the present invention is to provide a concrete means for completely automatically maintaining the molten state of the additive wire 6 in an optimum state at all times during hot wire welding.

(Means for Solving the Problems) A first aspect of the present invention is a method for controlling a hot wire welding device comprising an arc power source, a wire heating power source, etc. This hot wire welding control method is characterized in that the wire 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. .

The second aspect of the present invention is that in a hot 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 set lower than the heating power immediately before the wire is fused. The hot wire welding apparatus is characterized in that it is equipped with a wire heating power control circuit that repeatedly increases the wire heating power from the set value again until the wire reaches overheating and fusing.

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

(Function) When the wire heating power is slightly excessive with respect to the wire feeding speed, the additive wire 6 is overheated and the base material 3
It fused just before entering the upper weld pool 11,
The base material 3 and the additive wire 6 are separated. At this time, if the wire current is flowing, spatter will be generated with a popping sound, and the tip of the additive wire 6 will be exposed in the plasma column of the arc 5, and the molten pool 11 will be exposed.
Since both are located very close to each other, 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 and form a large droplet at the tip of the wire. This will also severely disturb the arc.
It becomes 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 pulsed 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, that is, the wire is in contact with the base material during the 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 at the next energization period. Since the tip of the wire 6 is simply exposed to the plasma column without continuously forming an arc, the progress of melting is extremely slow, and since the wire continues to be fed at a constant speed during that time, The tip of the wire 6 contacts the molten pool 11 again without forming a large droplet. After confirming that the tip of the addition wire 6 has come into contact with the molten pool 11, the wire current is restarted, and the process of overheating and melting is repeated. In this way, there is less disturbance in the arc, and although a few minute spatters are formed during fusing, they do not reach the point where they actually interfere with welding work, so that the tip of the additive wire 6 is brought into contact with the molten pool 11. Complete melting of the wire near the contacting interface 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 triax system is used as a wire heating power source that outputs a pulsed current, which can be constructed at a very low cost.
This is used as the wire heating power source 10 of the components of the hot wire TIG welding apparatus shown in FIG.

In this embodiment, a wire heating current forming circuit 19 is used in which a triac 16 is connected to the primary side of the main transformer 15, diodes 17 and 18 are connected to the secondary side of the transformer 15, and the wire heating current is output after full-wave rectification.
In this circuit, the triax 16 is controlled by the gate pulse forming circuit 20, and a wire current is obtained by controlling the phase of the commercial frequency AC power supply. , and the application of gate pulses to the triac 16 is controlled so that the period from 180 degrees to 270 degrees is always a non-current period. And tryack 1
The phase control angle for energizing 6 is set between the remaining 90 degrees to 180 degrees and 270 degrees to 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 metal, and when the wire tip is separated from the base metal and comes into contact with the arc plasma. When it is present, the voltage of the plasma column is detected and the voltage is -1V.
The voltage becomes more negative. Special patent application using this property
The wire contact state detection circuit 21 for detecting whether the tip of the wire 6 is in contact with the base material 3 is configured by the circuit of No. 61-030649. its output voltage
Va is H when the wire is in contact with the base metal,
When they are far apart, the voltage is at L level. This signal is the ON− signal in the gate pulse forming circuit 20.
It is applied to the OFF 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. A voltage Vb is output that determines the energization phase of the triac. 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 separates from 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 amount, the wire becomes overheated. It blows out like a fuse. When the wire is fused, it separates from the base material, so the wire contact state detection circuit 21 detects the change in Vw voltage at that time 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.

Since it operates in this way, when the wire feeding speed slows down during welding, the wire becomes slightly overheated, causing frequent wire fusing and gradually lowering 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 the energization phase control voltage forming circuit 2
3 operates, the wire heating power continues to increase, eventually causing a meltdown.

It functions similarly even if the wire extension e changes. In other words, as the extension becomes longer, the resistance value increases, and if the wire heating power source has constant voltage output characteristics, and the current phase remains constant, the peak value of the current will become lower, the output power will decrease, and it will become difficult to cause melting. The higher Vb acts to increase the energization phase, so that the heating power remains at its original value commensurate with the wire feed speed. Conversely, when the extension becomes shorter, the resistance value decreases, and if the current conduction phase is the same, the peak value of the current increases, resulting in excessive applied power and making it easier to blow out, and each time the extension shortens, the voltage Vb decreases and the current conduction phase changes. smaller, so that the wire feed speed and heating power are still kept commensurate with each other.

The amount by which Vb decreases each time a blowout occurs, or the rate at which Vb gradually increases thereafter, is determined by the voltage gradual increase rate.
The adjustment volume provided in the reduction width setting circuit 24 selectively adjusts and determines the appropriate value before or during welding.

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

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. Although this wire overheating and fusing may be extremely small, it may be accompanied by spatter, so it is desirable to reduce the frequency of this occurrence if possible. Therefore, when it is necessary to respond quickly to rapid changes in the wire feeding speed or extension, increase the rate of increase and decrease in the voltage Vb to increase the frequency of wire fusing, and also increase the rate of increase and decrease in the voltage Vb. When the extension does not change much, it is also possible to reduce the rate of increase and decrease width of the voltage Vb to reduce the frequency of overheating and melting of the wire. The increase/decrease state of the power applied to the wire is normally determined by the voltage gradual increase speed/decrease width setting circuit 24 before and during welding.
determined by manually adjusting the volume. 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 wire heating power increases gradually, and conversely, when the cycle is shorter than the specified value, the wire heating power increases gradually. In order to slow down the rate at which the wire heating power increases gradually,
This can also be done automatically by providing a circuit that controls the wire heating power so that the period at which the wire overheats and melts approaches a specified value.

Incidentally, if a high wire current is flowing at the moment the wire is overheated and fused, spatters are likely to form, but if a relatively low wire current of 100A or less is flowing, or if no current is flowing at all, spatters will not form. Not formed. 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. The formation of spatter can be greatly reduced. This can be done by specifying the cycle of wire overheating and blowing out, and by controlling the period in which the wire is not energized when the blowout is most likely to occur. In the case of a wire heating power supply using a triax 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 the time the wire energization resumes until the next melting occurs, and if the count exceeds a preset value, the heating power is reduced slightly. If the count does not reach the preset value, the heating power is controlled to decrease slightly. When controlled in this way, a blowout occurs immediately before the preset number of pulses ends, that is, after the instantaneous value of the wire heating current becomes 100A or less, or when the pulse current is completed and the wire current is 0. As a result, no spatter occurs at all during overheating and melting. Normally, with a 120 Hz pulse current obtained by full-wave rectification of a 60 Hz power supply frequency, 6 to 30 pulses are preset when feeding a 1.2 mm diameter wire at a speed near 0.5 to 4 m/min. 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, and if it is too short, the wire feeding speed will be relatively slow and heating will occur. This is because it cannot cope with a case where the electric 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 triax, 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 inverter type using transistors. 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 any manual operation 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 feeding speed, wire extension, arc current, arc length, wire insertion position and insertion angle, and all of these condition changes are involved. This makes it possible to always maintain an appropriate wire heating power state stably and automatically. As a result, 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 extremely easy to form especially 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. I can do it.

In addition, in the conventional control method for supplying wire heating power commensurate with the wire feeding speed, in addition to the wire feeding speed detection device, a power supply consisting of a Hall element, etc. for detecting the wire heating power is used. A detection device was required. In addition, in order to obtain the most accurate heating power possible, it was necessary to detect the wire voltage as close as possible to both ends of the extension, and the wiring became troublesome 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 is extremely simple. Therefore, it can be constructed at low cost.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. In a method of controlling a hot wire welding device comprising an arc power source, a wire heating power source, etc., the wire heating power after overheating and fusing the wire is greater than the heating power immediately before the wire is melted. A hot wire welding control method characterized by repeatedly setting the wire heating power to a low value and gradually increasing the wire heating power again from the set value to bring the wire to overheating and fusing. 2. In a hot 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 set lower than the heating power immediately before the wire melts, and the wire heating power is set again. 1. A hot wire welding device comprising a wire heating power control circuit that repeatedly increases the power from a set value until the wire reaches 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, a wire heating power source that outputs a pulse current based on a control signal from a circuit that determines a reference wire energization suspension period and a wire energization period is used as a wire heating power source. 1. A hot wire welding device comprising a circuit for controlling overheating so that overheating occurs when the instantaneous value of the wire current is 100 A or less or during a corresponding 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 proportional constant is gradually increased over time to prevent wire overheating and melting. A hot wire welding device characterized in that the proportional constant value is reset to the value immediately before the wire overheating and melting occurs.