JPH1190629A - Pulsed arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulsed arc welding method capable of obtaining securely and easily a weld zone of satisfactory welding quality without defects in a pore or the like, even when the environmental change due to disturbances exists. SOLUTION: In a gas shielded MIG pulsed welding method in which welding is performed, while bubbles contained in a molten pool 4 are discharged outside or while the crystals of a molten metal are micronized, by vibrating the molten pool 4 being made to coincide with a natural frequency, the phase of the vibration of the molten pool 4 is detected by a short circuit S, after a delay time Δt1, a peak current is increased by a Δt2 time, and thereby, the electromagnetic force of an arc is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pulse arc welding method such as a consumable electrode type pulse arc welding method such as a MIG pulse welding method and a non-consumable pulse arc welding method such as a TIG pulse welding method.

[0002]

2. Description of the Related Art The inventors of the present invention vibrate a molten pool in accordance with a natural frequency to discharge bubbles (blow holes) contained in the molten pool to the outside, to make molten metal crystals fine, etc. (Japanese Unexamined Patent Publication No. Hei 6-285643, "TOYOTA").
Technical Review "vol. 45
No. 1 May 1995 pp. 116-125).

In this arc welding method, for example, the MIG pulse welding method, a high and narrow first pulse P1 is obtained as a current waveform by setting a welding power source as shown in FIG.
And a group of low and wide second pulses P2. That is, the peak current IH of the first pulse P1 is
And the pulse time tH of the first pulse P1 is shorter than the pulse time tL of the second pulse P2.
Further, by setting the wire feeding device, as shown in FIG. 12B, the wire feeding speed is kept constant, and the fluctuation of the arc length is suppressed. At this time, the first pulse P1 and the second pulse P
The cycle of one pulse of 2 is TP. FIG.
As shown in (1), one droplet 2a is generated from the welding wire 2 with respect to the base material 1 in one pulse (one pulse one droplet transfer condition). Then, as shown in FIG. 12A, switching between the time TH for energizing the group of the first pulses P1 and the time TL for energizing the group of the second pulses P2 is performed at several tens of Hz.
In a swell cycle Tw. Here, as shown in FIG. 13, if the undulation period Tw matches the natural frequency of the molten pool 4 generated in the base material 1, the vibration of the weld line in the molten pool 4 in the front-rear direction (left-right direction on the paper) is amplified,
If the swell period Tw does not match the natural frequency of the molten pool 4, the longitudinal vibration in the molten pool 4 varies.

[0004] For this reason, in such a MIG pulse welding method, the electromagnetic force of the arc 3 is regularly changed in accordance with the swell period Tw corresponding to the natural frequency of the molten pool 4, thereby joining the molten pool 4 to the welding line. Vibrates back and forth. For this reason, the buoyancy of the air bubbles 6 in the molten pool 4 is positively activated by the flow of the molten metal indicated by the arrow, and the bubbles 6 tend to float outside. Further, the crystal of the molten metal is refined by the flow of the molten metal.

[0005] Thus, in this MIG pulse welding method, the bubbles 6 in the molten pool 4 can be discharged to the outside,
In addition, the crystal of the molten metal can be made finer, and a welded portion having good welding quality without pore defects or the like can be obtained.

[0006]

However, during welding,
A jig or the like that supports the base material 1 inevitably vibrates minutely, and the vibration also causes the base material 1 to vibrate minutely. In this regard, in the pulse arc welding method, if there is no disturbance due to minute vibration of the base material 1 or the like, the arc 3 is set by setting the welding power source.
Although a welded part of good welding quality can be obtained only by changing the electromagnetic force of the weld in a regular manner in accordance with the swell period Tw, the weld pool 4 vibrates in accordance with the natural frequency only due to disturbance. When the phase of the vibration of the molten pool 4 due to the period Tw is out of phase with the vibration of the molten pool 4 due to the disturbance,
These vibrations interfere with each other, and the overall vibration of the molten pool 4 is attenuated. In this case, the bubbles 6 in the molten pool 4 may not be effectively discharged to the outside, or the crystal of the molten metal may not be effectively refined.
There is a possibility that a weld having a pore defect or the like may be obtained.

[0007] In some cases, the heat input condition by the welding power source inevitably changes. In this case, since the capacity of the molten pool 4 changes, the natural frequency of the molten pool 4 changes accordingly. In this way, when the natural frequency of the molten pool 4 is different, in order to obtain a welded part of good welding quality, the swell period Tw is individually adjusted in accordance with the natural frequency of the molten pool 4 that cannot be actually measured. It is necessary to reset the current waveform by the welding power source, such as resetting. Such an operation is complicated by trial and error, and in reality, it is very difficult to weld a component having a complicated shape in this way.

Further, even if the heat input conditions are the same, if the shape of the joint forming the base material 1 is different, the shape of the molten pool 4 also changes, and the natural frequency of the molten pool 4 changes accordingly. Therefore, a similar problem occurs. The present invention has been made in view of the above-described circumstances, and is a pulsed arc capable of reliably and easily obtaining a welded portion having good welding quality without pore defects and the like even if there is an environmental change due to disturbance or the like. It is an object of the present invention to provide a welding method.

[0009]

According to the pulse arc welding method of the present invention, the molten pool is vibrated in accordance with a natural frequency to discharge bubbles contained in the molten pool to the outside or to form a molten metal. In a pulse arc welding method performed while refining a crystal, the phase of vibration of the molten pool is detected to increase the electromagnetic force of the arc.

In the pulse arc welding method according to the present invention, the phase of the molten pool caused by the undulation cycle and the phase of the molten pool caused by disturbance such as minute vibration of the base material are shifted from each other, and the resulting vibrations interfere with each other. Even if the overall vibration of the molten pool is about to be attenuated, the phase of the vibration of the molten pool is detected at that time to increase the electromagnetic force of the arc. In addition, even if the heat input conditions change or the joint shape changes, the natural frequency of the molten pool changes due to these changes. In this case, the phase of the vibration of the molten pool is detected and the electromagnetic force of the arc is increased. . In this case, it is not necessary to reset the current waveform by the welding power source, such as individually resetting the undulation cycle that matches the natural frequency of the molten pool.

In this way, in this pulse arc welding method, the damping of the overall vibration of the molten pool is suppressed, and thus the overall vibration of the molten pool is amplified. The metal crystals are reliably refined. Therefore, according to the pulse arc welding method of the present invention, even if there is an environmental change such as disturbance, a welded portion having good welding quality without pore defects or the like can be obtained reliably and easily.

As means for detecting the phase of the vibration of the molten pool, means for causing the welding wire to come into contact with the molten pool due to the vibration of the molten pool and detecting a short circuit caused thereby as a change in welding current or welding voltage is adopted. I can do it. As another means, a means for detecting a change in the arc length caused by the vibration of the molten pool as a change in the welding voltage may be employed.

As means for increasing the electromagnetic force of the arc, at least one of the following can be used. 1. When a peak current for securing a molten pool in a weld portion and a base current having a smaller heat input than the peak current are used as the first pulse or the second pulse, a peak current that shifts to a droplet of a welding wire or a peak due to a welding electrode is used. Increase the current or voltage of the current.

2. The width of one pulse of the peak current is increased. 3. The time for energizing the first pulse group is increased. 4. Increase the wire feed speed at the tip of the torch. 5. Lower the torch height. 6. Move the torch behind the weld line.

[0015] 7. The angle of the torch is set to the receding angle so that the tip of the welding wire or the welding electrode faces backward of the welding line. In the means 1 to 7, the molten pool is vibrated in the front-rear direction of the welding line, and thus the molten pool is preferably vibrated in the front-rear direction of the welding line. When the short circuit is employed as a means for detecting the phase of the vibration of the molten pool, it is preferable that the electromagnetic force of the arc be increased after a delay time after the detection. This is because the surface of the molten pool where the electromagnetic force of the arc works may rise afterwards depending on the state of vibration of the molten pool. This is because it is difficult to amplify such vibrations. For this reason, the delay time is a period in which the upper limit is almost half of the cycle of the natural frequency of the molten pool according to its capacity. Since the natural frequency is affected by the length, width and depth of the molten pool, the viscosity of the molten metal, the surface tension, and the like, the natural frequency is not a fixed value, but is generally several Hz to several tens of Hz.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 8 embodying the present invention will be described below with reference to the drawings. (Embodiment 1) In Embodiment 1, the gas shield MIG pulse welding method is performed under the heat input conditions of the current waveform shown in FIG. 1A and the wire feeding speed shown in FIG. 1B.

That is, a group of high and narrow first pulses P1 and a group of low and wide second pulses P2 are used depending on the setting of the welding power source. In addition, by setting the wire feeding device, the wire feeding speed is kept constant, and the fluctuation of the arc length is suppressed. Here, as shown in FIG. 2, when the average current A0 is determined corresponding to a constant wire feeding speed, the average current value A1 of the group of the first pulse P1 is larger than the average current A0,
The average current value A2 of the second group is smaller than the average current A0. In addition, the setting is such that the swell period Tw matches the natural frequency of the molten pool.

The MIG pulse torch connected to the welding power source is held by a welding robot, and the torch is provided with a welding wire 2 shown in FIG. In the method of the first embodiment, the molten pool 4 vibrates as a whole. When the group of the second pulse P2 is energized, the wire feeding speed is higher than the speed at which the welding wire 2 drops the droplet 2a.
As shown in (A), when the surface immediately below the welding wire 2 in the molten pool 4 rises, the welding wire 2 comes into contact with the molten pool 4 and a short circuit S occurs almost regularly. Such a short circuit S is detected as a change in welding current or welding voltage.

For this reason, a jig or the like that supports the base material 1 inevitably vibrates minutely, and the base material 1 vibrates minutely due to the vibration.
And the vibration of the molten pool 4 due to the minute vibration of the base material 1 are out of phase, and the vibrations caused by the two interfere with each other to attenuate the overall vibration of the molten pool 4. The electromagnetic force of the arc 3 is increased by detecting the phase of the vibration of the molten pool 4.

That is, after the short-circuit S is detected, the process waits until the delay time Δt1 has elapsed, and when the surface immediately below the welding wire 2 in the molten pool 4 enters a descending process, FIG.
As shown in (B), a change is made to the heat input conditions of the welding power source. Here, even if the second pulse group P2 is energized, the first pulse P1 having the increased peak current is set to Δt2
Energize only for time.

Even if the natural frequency of the molten pool 4 changes due to a change in heat input conditions or a change in the shape of the joint, the phase of the vibration of the molten pool 4 is detected at that time. Increase the electromagnetic force of 3. In this case, the molten pool 4
It is not necessary to reset the current waveform by the welding power source, such as individually setting the swell period Tw that matches the natural frequency of the welding power source.

Thus, in the method of the first embodiment, as shown in FIG. 3C, the arc 3 pushes the molten pool 4 with a large electromagnetic force, so that the surface of the molten pool 4 immediately below the welding wire 2 descends. Then, the entire molten metal is flowed backward. The speed is affected by the volume and viscosity of the molten metal. At that time, the molten pool 4
The hot water flows backward also at the bottom of the. Note that FIG.
As shown in (D), after the first pulse P1 has been energized for Δt2 hours, the molten metal flows countercurrently in half the cycle of the natural frequency of the molten pool 4. At that time, the driving force is the surface tension and gravity of the molten metal, and the resistance is the viscosity of the molten metal. Thus, the attenuation of the overall vibration of the molten pool 4 is suppressed, and the overall vibration of the molten pool 4 is amplified. For this reason, the bubbles in the molten pool 4 surely rise to the outside, and the crystal of the molten metal is surely miniaturized.

Thereafter, the heat input condition of the welding power source is returned to the original,
Continue welding. Then, such a series of operations is repeated. Therefore, according to the method of the first embodiment, even if there is an environmental change such as disturbance, a welded portion having good welding quality without pore defects or the like can be obtained reliably and easily.

When the peak current is increased by Δt2 as in the first embodiment, the average current is increased, the melting amount of the welding wire 2 is increased, and one pulse and one droplet transfer for obtaining a suitable welding quality are performed. It is easy to damage the conditions.
For this reason, in this case, in order to reduce the variation in the amount of fusion of the welding wire 2, the pulse time may be reduced at the same time so that the area of the pulse is not reduced. Embodiment 2 In Embodiment 1, as shown in FIG. 4, the average current value A2 of the group of the second pulse P2 is
It may be larger than zero. For example, there are errors in setting, changes in heat input conditions, and changes in the shape of the joint. In this case, even when the group of the second pulse P2 is energized, the wire feeding speed is not necessarily higher than the speed at which the welding wire 2 drops the droplet 2a, so that the short circuit S
Will not occur.

For this reason, according to the method of the second embodiment, as shown in FIG. 5, the average current value A2 of the group of the second pulses P2 is reduced with time. Other configurations, conditions, and the like are the same as those in the method of the first embodiment. In this way, the speed at which the welding wire 2 drops the droplets 2a during energization of the group of the second pulses P2 gradually decreases, and the short circuit S can be reliably generated.

Therefore, in the method of the second embodiment, the same operation and effect as those of the method of the first embodiment can be obtained even if there is an error in the setting or the like. Embodiment 3 In Embodiment 3, as shown in FIG. 6, instead of increasing the peak current, the period TP of one pulse of the peak current is increased. Other configurations, conditions, and the like are the same as those in the method of the first embodiment.

In the method according to the third embodiment, the electromagnetic force of the arc 3, that is, the force for pushing down the surface of the molten pool 4 increases with an increase in the width of one pulse. Therefore, the method of the third embodiment can provide the same operation and effect as the method of the first embodiment. Embodiment 4 In Embodiment 4, as shown in FIG. 7, instead of increasing the peak current, the time TH for energizing the group of peak currents is shortened. Other configurations, conditions, and the like are the same as those in the method of the first embodiment.

In the method of the fourth embodiment, the number of pulses increases and the electromagnetic force of the arc 3 increases. Therefore, the method of the fourth embodiment can provide the same operation and effect as the method of the first embodiment. Embodiment 5 In Embodiment 5, as shown in FIGS. 8A and 8B, instead of increasing the peak current, the torch 8 is used.
Roller 1 for feeding welding wire 2 downward from the tip of
The wire feeding speed according to 0a is set to be high. Other configurations,
Conditions and the like are the same as in the method of the first embodiment.

In the method of the fifth embodiment, the action of the electromagnetic force of the arc 3 is concentrated on the surface of the molten pool 4 immediately below the welding wire 2. Also, in this case, the self-control action of the welding power source acts to promote the melting of the welding wire 2 and the current increases, so that the electromagnetic force of the arc 3 increases. Therefore, the method of the fifth embodiment can provide the same operation and effect as the method of the first embodiment. Embodiment 6 In Embodiment 6, as shown in FIGS. 9A and 9B, instead of increasing the peak current, the torch 8 is used.
Height is small. Other configurations and conditions are the same as those in the first embodiment.
It is the same as the above method.

In the method of the sixth embodiment, as in the method of the fourth embodiment, the electromagnetic force of the arc 3 is concentrated on the surface of the molten pool 4 immediately below the welding wire 2 and the arc 3 is controlled by the self-control action of the welding power source. The effect of increasing the electromagnetic force is obtained. Therefore, the method of the sixth embodiment can provide the same operation and effect as the method of the first embodiment. (Embodiment 7) In Embodiment 7, FIGS.
As shown in FIG. 7, the torch 8 is moved backward instead of increasing the peak current. Other configurations, conditions, and the like are the same as those in the method of the first embodiment.

In the method of the seventh embodiment, the molten metal 4 is shifted to a position where the molten pool 4 is recessed by the electromagnetic force of the arc 3, whereby a backward flow of the molten metal can be caused. Therefore, the method of the seventh embodiment can provide the same operation and effect as the method of the first embodiment. Embodiment 8 In Embodiment 8, FIGS. 11A and 11B
As shown in FIG. 7, instead of increasing the peak current, the torch 8 is set to the receding angle, and the tip side is directed backward. Other configurations, conditions, and the like are the same as those in the method of the first embodiment.

In the method of Embodiment 8, the molten metal can be pushed backward by the electromagnetic force of the arc 3.
Therefore, the method of the eighth embodiment can provide the same operation and effect as the method of the first embodiment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a current waveform and a wire feeding speed which are heat input conditions set in a welding power source according to a method of Embodiment 1.

FIG. 2 is a schematic diagram showing an average current according to the method of the first embodiment.

FIG. 3 is a schematic sectional view of a current waveform, a voltage waveform, and a welded portion according to the method of the first embodiment.

FIG. 4 is a schematic diagram showing an average current due to an error or the like.

FIG. 5 is a schematic diagram showing an average current according to the method of the second embodiment.

FIG. 6 shows a current waveform and a voltage waveform according to the method of the third embodiment.

FIG. 7 shows a current waveform and a voltage waveform according to the method of the fourth embodiment.

FIG. 8 is a schematic sectional view of a torch and a welded portion according to a method of Embodiment 5.

FIG. 9 is a schematic sectional view of a torch and a welded part according to the method of Embodiment 6.

FIG. 10 is a schematic sectional view of a welding wire and a welded portion according to the method of the seventh embodiment.

FIG. 11 is a schematic sectional view of a welding wire and a welded portion according to a method of an eighth embodiment.

FIG. 12 is a schematic diagram showing a current waveform and a wire feeding speed as heat input conditions set in a welding power source according to a conventional method.

FIG. 13 is a schematic sectional view of a welded portion according to a conventional method.

[Explanation of symbols]

 2 ... welding wire 4 ... molten pool 6 ... bubble S ... short circuit 3 ... arc

Claims (1)

[Claims] 1. A pulse arc welding method in which a molten pool is vibrated in accordance with a natural frequency to discharge bubbles contained in the molten pool to the outside or to refine crystals of a molten metal. A pulse arc welding method characterized by detecting the phase of vibration of a molten pool and increasing the electromagnetic force of an arc.