JP2016168617A - Arc-welding control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc-welding control method capable of eliminating the drawback which might otherwise be caused by the phenomena that a welding wire is continuously fed backward during a short circuit period, the feed amount of a welding wire is reduced and thus a bead with irregularity is formed if a short circuit period is disturbed to continue a short circuit state by disturbances such as the irregular motions of a molten pool or the fluctuations of an arc length so that a short circuit continues long, and the drawback, in which the disturbance of the short circuit period induces a minute short circuit, and in which a sputter generation rate increases to make it difficult to retain a regular and stable arc state.SOLUTION: When a short circuit period continues for a predetermined time period or longer, the backward wire feeding rate is controlled to a larger absolute value than that of the backward feed at the time instant when said predetermined time period is reached, so that the short circuit can be early opened to prevent the elongation of the short circuit period.SELECTED DRAWING: Figure 1

Description

  According to the present invention, feeding of the welding wire is periodically changed at a predetermined cycle and a predetermined amplitude alternately between a normal feeding performed in the direction of the welding object and a reverse feeding performed in a direction opposite to the normal feeding. The present invention relates to a consumable electrode type arc welding control method in which welding is performed by feeding at a wire feeding speed and repeating an arc period and a short-circuit period.

  In recent years, for the purpose of reducing spatter generated during welding, consumable electrode type arc welding has been performed in which welding wire feeding is repeated between forward feeding and reverse feeding, and welding is performed by alternately generating an arc period and a short-circuit period. It has been put into practical use.

  FIG. 5 is an output waveform diagram showing a conventional arc welding control method in which welding is performed by alternately generating an arc period and a short-circuit period by repeating forward feeding and reverse feeding. FIG. 4A shows the wire feed speed Wf, FIG. 4B shows the welding current Aw, and FIG. 4C shows the time variation of the welding voltage Vw.

  In the figure, during the short circuit period from time t1 to time t2, when a short circuit occurs at time t1, the wire feed speed Wf is changed from the wire feed speed Wfa which is forward feed to the wire feed speed Wfs which is reverse feed. Transition towards. As a result, the welding wire is fed backward. In addition, during the short circuit period, the welding current Aw increases with time due to current control.

  As described above, the feeding amount of the welding wire fed during the short circuit period is reduced by reversing the feeding of the welding wire during the short circuit period. Thereby, compared with the case where the welding wire is fed at a constant feed, the short circuit can be mechanically opened, so that the current at the time of the short circuit can be reduced, and the amount of spatter generated when the short circuit is opened can be reduced (for example, Patent Document 1). reference).

Japanese Patent No. 4211793

  Although the welding wire feed control in the conventional arc welding control method described above leads to a reduction in spatter, it is possible to prevent disturbance of the short-circuit cycle due to disturbance such as irregular movement of the molten pool and fluctuation of the arc length. Can not. If the short-circuit condition continues for a long time due to the short-circuit cycle, the welding wire feed continues to reverse during the short-circuit period, during which the welding wire feed rate is reduced, leading to the formation of uneven uneven beads. . Further, in CO2 welding, spatter due to a short-circuit in a very short time (hereinafter referred to as a micro short-circuit) is likely to occur particularly immediately after the occurrence of an arc in the arc period and immediately before the occurrence of a short-circuit. When the short-circuit cycle is disturbed, the behavior of the molten pool becomes large, so that a short-circuit is likely to occur, and there is a problem that spatter due to the short-circuit increases.

Wire feeding speed in which welding wire feeding is periodically changed at a predetermined cycle and a predetermined amplitude alternately between forward feeding performed in the direction of the welding object and reverse feeding performed in the opposite direction to the normal feeding. Is a consumable electrode type arc welding control method in which welding is performed by repeating an arc period and a short-circuit period, and when the short-circuit period continues for a predetermined period or longer, the wire feed speed is set to The absolute value is controlled to be larger than the reverse feed wire feed speed at the time when the predetermined period is reached. In addition, the wire feeding is performed by periodically changing the welding wire feeding at a predetermined cycle and a predetermined amplitude alternately between the forward feeding performed in the direction of the welding object and the reverse feeding performed in the reverse direction. It is a consumable electrode type arc welding control method in which welding is performed by feeding at a feed rate and repeating an arc period and a short circuit period, and the short circuit period after starting the short circuit is longer than the immediately preceding short circuit period. In this case, the reverse wire feed speed is controlled to a value having a larger absolute value than the reverse wire feed speed at the end of the immediately preceding short-circuit period.
In addition, the wire feeding is performed by periodically changing the welding wire feeding at a predetermined cycle and a predetermined amplitude alternately between the forward feeding performed in the direction of the welding object and the reverse feeding performed in the reverse direction. It is a consumable electrode type arc welding control method in which welding is performed by feeding at a feeding speed and repeating an arc period and a short-circuit period,
If the short-circuit period after the start of the short circuit becomes longer than the average value of one or more previous short-circuit periods, the reverse feed wire feed speed is set to the average reverse feed speed at the end of the previous short-circuit period. Control to a larger absolute value.
In addition, the average value of the short-circuit period and the average speed of the reverse wire feed speed at the end of the short-circuit period are obtained in advance, a predetermined period equal to or greater than the average value of the short-circuit period is set, and the short-circuit after the short-circuit is started When the period becomes longer than the predetermined period, the reverse wire feed speed is controlled to a value having a larger absolute value than the average speed of reverse feed acquired in advance.
When the short-circuit period continues for a predetermined period or longer, the welding current is controlled to a value larger than the welding current when the predetermined period is reached.
Further, the slope of the reverse wire feed speed when the short-circuit period continues for a predetermined period or more is controlled to a value larger than the slope of the reverse wire feed speed before the short-circuit period reaches the predetermined period. .
Further, the inclination of the wire feed speed from the reverse feed to the normal feed is controlled to a different value depending on the time from the time when the short-circuit period reaches the predetermined period to the time when the short-circuit is opened.
The welding wire is made of a material having high thermal conductivity such as aluminum, aluminum alloy, copper, or copper alloy.

  In the present invention, when the short-circuit period continues for a predetermined period or longer, the reverse wire feed speed is controlled to a value having a larger absolute value, so that the short-circuit can be opened early. By preventing the lengthening of the short circuit period and stabilizing the short circuit period, a uniform and flat bead appearance with reduced irregularities can be obtained, and the welding quality is improved. Moreover, generation | occurrence | production of a micro short circuit can also be suppressed, the amount of spatter generations can be reduced, and stable welding can be realized.

The figure of the output waveform by the arc welding control method in Embodiment 1, 2 of this invention The figure which shows schematic structure of the arc welding apparatus in this invention The figure which shows the change of the inclination of the feeding speed in Embodiment 3 of this invention. The figure which shows the output waveform by the arc welding control method in Embodiment 3 of this invention The figure which shows the output waveform in the conventional arc welding control method

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment 1)
First, an arc welding apparatus that performs the arc welding control method of the present embodiment will be described with reference to FIG. FIG. 2 is a diagram showing a schematic configuration of the arc welding apparatus. The arc welding apparatus 20 performs welding by repeating an arc state and a short-circuit state between a welding wire 22 that is a consumable electrode and a workpiece 21.
The arc welding apparatus 20 includes a main transformer 2, a primary side rectification unit 3, a switching unit 4, a DCL (reactor) 5, a secondary side rectification unit 6, a welding current detection unit 7, and a welding voltage detection unit. 8, a short circuit detection unit 9, an output control unit 12, and a wire feed speed control unit 16.

  The short circuit detection unit 9 includes a short circuit time detection unit 10 and a short circuit / arc detection unit 11. The output control unit 12 includes a short circuit control unit 13 and an arc control unit 14. The wire feed speed control unit 16 includes a wire feed speed detection unit 17, a calculation unit 18, and a forward / reverse feed switching timing control unit 19. The primary side rectification unit 3 rectifies an input voltage input from an input power supply outside the arc welding apparatus 20. The switching unit 4 controls the output of the primary side rectification unit 3 to an output suitable for welding. The main transformer 2 converts the output of the switching unit 4 into an output suitable for welding. The secondary side rectification unit 6 rectifies the output of the main transformer 2. A DCL (reactor) 5 smoothes the output of the secondary side rectification unit 6 to a current suitable for welding. The welding current detector 7 detects the welding current. The welding voltage detector 8 detects the welding voltage. The short circuit time detection unit 10 detects the time during which the welding wire 22 and the workpiece 21 are short-circuited based on the output of the welding voltage detection unit 8. Based on the output of the welding voltage detection unit 8, the short circuit / arc detection unit 11 determines whether the welding state is a short circuit state in which the welding wire 22 and the workpiece 21 are short-circuited, or the welding wire 22 and the workpiece. It is determined whether the arc is in an arc state where the arc 23 is generated. The output control unit 12 controls the welding output by outputting a control signal to the switching unit 4. The short-circuit control unit 13 controls the short-circuit current that is the welding current during the short-circuit period when the short-circuit / arc detection unit 11 determines that the short-circuit state has occurred. The arc control unit 14 controls the arc current, which is a welding current during the arc period, when the short circuit / arc detection unit 11 determines that the arc state is present. The wire feed speed control unit 16 controls the wire feed unit 25 to control the feed speed of the welding wire 22. The wire feed speed detector 17 detects the wire feed speed. Based on the signal from the wire feed speed detection unit 17, the calculation unit 18 calculates an integrated amount of the feed amount of the welding wire 22 for a predetermined time. The forward / reverse switching timing control unit 19 controls the control signal for delaying the switching timing of the feeding of the welding wire 22 from the normal feeding to the reverse feeding based on the signal from the calculation unit 18 or the reverse feeding to the normal feeding. A control signal for delaying the switching timing to is output.

  A welding condition setting unit 15 and a wire feeding unit 25 are connected to the arc welding apparatus 20. The welding condition setting unit 15 is used for setting welding conditions in the arc welding apparatus 20. The wire feeding unit 25 controls the feeding of the welding wire 22 based on a signal from the wire feeding speed control unit 16.

  The welding output of the arc welding apparatus 20 is supplied to the welding wire 22 via the welding tip 24. Then, welding is performed by generating an arc 23 between the welding wire 22 and the workpiece 21 by the welding output of the arc welding apparatus 20.

  Next, operation | movement of the arc welding apparatus 20 comprised as mentioned above is demonstrated using FIG.

  FIG. 1 is a diagram showing an output waveform by the consumable electrode type arc welding control method in the present embodiment. The time change of the wire feed speed Wf, the welding current Aw, and the welding voltage Vw in the arc welding which repeats a short circuit period and an arc period alternately is shown.

  In FIG. 1, the wire feed speed Wf that is periodically changed with a predetermined cycle and a predetermined amplitude alternately between the forward feed performed in the direction of the welding object and the reverse feed performed in the reverse direction is a predetermined feed rate. Is controlled so as to periodically repeat forward feed and reverse feed, for example, in a trapezoidal waveform, which is a basic waveform, at a frequency F and a predetermined velocity amplitude AV. However, the period T, which is the reciprocal of the frequency, is the sum of the short-circuit period Ts from time t1 to time t2 and the arc period Ta from time t2 to time t3. The wire feed speed Wf in the short-circuit period Ts from the start of the short-circuit to the short-circuit release is controlled so as to shift from the forward feed speed Wfa toward the reverse feed speed Wfs, and the reverse feed speed Wfs. Is reached, it is controlled to be constant at the reverse feed speed Wfs. The wire feed speed Wf in the arc period Ta is controlled so as to shift from the reverse feed speed Wfs to the forward feed speed Wfa. When the forward feed speed Wfa is reached, the reverse feed speed Wf is controlled. The feed speed Wfa is controlled to be constant.

  It should be noted that the forward feed speed and the reverse feed speed of the wire feed speed Wf, that is, the shape of the feed waveform such as the period, the amplitude, and the inclination are determined in advance for each set current set in the arc welding apparatus.

  The control of the welding current Aw increases the welding current to a predetermined peak current value in the arc period Ta, thereby increasing the melting rate of the tip of the welding wire to form droplets. And the said droplet is made to transfer to a fusion pool by the short circuit period Ts. Welding is performed by repeating this.

  In addition, in short circuit period Ts, in order to open a short circuit state, it controls so that a welding current is increased with progress of time. As an increase mode, for example, as shown in FIG. 1, first, the first current increase slope AWa1 increases, and then the second current increase slope whose slope is gentler than the first current increase slope AWa1. Increase with AWa2. The current value at the time of switching from the first current increase slope AWa1 to the second current increase slope AWa2 is referred to as a bending point.

Note that the waveform of the wire feed speed Wf that repeats forward feeding and reverse feeding may be trapezoidal as shown in FIG. 1 or sinusoidal.
Further, as shown in FIG. 1, the wire feed speed Wf becomes constant when the reverse feed speed Wfs and the normal feed speed Wfa are reached, as shown in FIG. Then, the arrival value of the feeding speed does not necessarily need to be held at a constant value, and may be an amplitude amount corresponding to the backward feeding speed Wfs and the forward feeding speed Wfa.

FIG. 1 is a diagram showing temporal changes in the wire feed speed Wf and the welding current Aw, and is a diagram showing wire feed control when the short-circuit cycle is disturbed or the short-circuit time becomes long. This is especially true when wires made of a material with high thermal conductivity such as aluminum, aluminum alloy, copper, copper alloy, blaze, etc., which are difficult to generate Joule heat, are difficult to open short circuit, and the dispersion of droplet transfer state varies between short circuit periods. It appears as a variation.
Factors that increase the short-circuit period include disturbances such as irregular movement of the weld pool and fluctuations in arc length.

Therefore, in the first embodiment, after the welding wire 22 is short-circuited to the workpiece 21, the short-circuiting time detection unit 10 based on the welding voltage detection unit 8 has a short-circuiting period Ts1 in which the short-circuiting period Ts is less than a predetermined period. Inside, the welding wire is set to a predetermined wire feed speed gradient WFs1 and fed back at a reverse feed speed Wfs.
If the short circuit / arc detection unit 11 does not open the short circuit (arc detection) even after the predetermined period, the wire is fed back at the reverse wire feed speed Wfs ′ having a larger absolute value than the reverse feed wire feed speed Wfs ′. Thus, the welding wire 22 is short-circuited from the workpiece 21 and guided so as to be detached.
The predetermined period is an average short-circuit period from the start of the short-circuit to the end of the short-circuit (short-circuit open), and the wire feed speed is in the reverse feed region (wire feed is in the reverse feed state). It is a period.

  Further, the predetermined period may be the immediately preceding short circuit period or may be an average value of one or more previous short circuit periods. Or it is good also as an average value of the short circuit period which acquired the predetermined period beforehand.

  Further, the predetermined period may be an average short-circuit period that is determined in advance by experiments, experience values, or the like from the start of the short-circuit to the end of the short-circuit (short-circuit open).

  Further, the wire feed speed Wfs ′ for reverse feed at this time can be set to 100 to 200% of the absolute value of the wire feed speed Wfs for reverse feed immediately before. When the average speed of the wire feed speed of reverse feed at the end of the period is acquired, a predetermined period equal to or greater than the average value of the short circuit period is set, and the short circuit period after starting the short circuit becomes longer than the predetermined period, The reverse wire feeding speed may be a value having a larger absolute value than the average speed of reverse feeding acquired in advance.

  As described above, when the short-circuit period becomes longer than the predetermined period, the short-circuit opening can be quickly brought about by setting the reverse wire feed speed to a value having a larger absolute value.

  In addition, if the predetermined period is the immediately preceding short-circuit period, the recovery from the extension of the short-circuit period is accelerated, and if the predetermined period is an average value of one or more previous short-circuit periods, the short-circuit period is stabilized. . Further, if the predetermined period is an average value of the short-circuit periods acquired in advance, it is possible to realize an appropriate short-circuit period stabilization according to different welding wires and workpieces.

(Embodiment 2)
The second embodiment relates to an increase in welding current at the time of a short circuit when the short circuit period is prolonged.

  In the second embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The main difference from the first embodiment is that the third current increase becomes a value larger than the second current increase slope AWa2 as shown in FIG. 1 when the short circuit is not opened (arc detection) beyond a predetermined period. This is the point at which the welding current is increased at the inclination AWa3. By increasing the welding current at the time of a short circuit, the welding wire 22 is easily melted and the effect of promoting the opening of the short circuit is caused, and an electromagnetic pinch force is applied to the droplet to form a constriction and promote separation.

  As described above, when the short-circuit period continues for a predetermined period or longer, the welding current is set to a value larger than the welding current at the time when the predetermined period is reached, thereby further promoting short-circuit opening (leading to short-circuit opening at an early stage). )be able to.

(Embodiment 3)
The third embodiment relates to the suppression of the decrease in the wire feed amount due to the prolonged short circuit period. In the third embodiment, the same parts as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. The main difference from the first and second embodiments is that when the reverse feed is performed at the reverse feed wire feed speed Wfs ′, which is larger in absolute value than the reverse feed wire feed speed Wfs ′ until the short circuit is opened. The short-circuit period becomes longer and the forward wire feed amount decreases for the period in which the reverse feed is continued at the wire feed speed Wfs ′. In order to prevent this, the inclination WFs2 of the wire feed speed when the wire feed speed Wfs ′ having a large absolute value is reached from the reverse feed wire feed speed Wfs is changed from the forward feed wire feed speed Wfa to the reverse feed. The absolute value is larger than the slope WFs1 of the wire feed speed that reaches the wire feed speed Wfs. Further, as shown in FIG. 3, the wire feed speed gradient WFa2 as the acceleration / deceleration of the wire feed speed that shifts from the reverse feed wire feed speed Wfs' to the forward feed wire feed speed Wfa is detected as a short circuit. It is controlled to a different value depending on the time when the short circuit is opened, such as T1 to T3, which are the elapsed time after. As shown in FIG. 3 (B), when the short circuit is opened is the elapsed time T1 after the detection of the short circuit, the wire feed speed at which the reverse feed wire feed speed Wfs ′ shifts to the forward feed wire feed speed Wfa. The slope WFa2 is WFT1. Similarly, when the time when the short circuit is opened is the elapsed time T2 after the detection of the short circuit, the wire feed speed gradient WFa2 for shifting from the reverse feed wire feed speed Wfs ′ to the forward feed wire feed speed Wfa is defined as WFT2. At the elapsed time T3 after the detection of the short circuit, the slope WFa2 of the wire feeding speed at which the wire feeding speed Wfs ′ of reverse feeding shifts to the wire feeding speed Wfa of normal feeding is defined as WFT3. This prevents the next arc period from being lengthened due to the lengthening of the short circuit period, and suppresses the disturbance of the short circuit period. Further, the method of controlling the reverse feed wire feeding speed to a large absolute value when the short-circuit is not opened beyond the predetermined period is, for example, from the forward feed wire feed speed Wfa as shown in FIG. Backward feeding is performed at the wire feeding speed gradient WFs2 that shifts to the wire feeding speed Wfs, and after the transition to the constant feeding wire feeding speed Wfs ′, a short circuit is opened at the constant feeding wire feeding speed Wfs ′. The reverse feed may be continued until Alternatively, for example, as shown in FIG. 4, reverse feeding may be continued with the wire feeding speed gradient WFs2 until the short circuit is opened.

  As described above, when the short-circuit period is longer than the predetermined period, the reverse-feed wire feed speed is set to a value having a larger absolute value, thereby preventing the short-circuit period from being prolonged. Further, the inclination of the wire feeding speed from the reverse feed after the short-circuit opening to the normal feed is opened according to the time from the time when the short-circuit period reaches the predetermined period to the time when the short-circuit is opened. By controlling to a different value depending on the time, it is possible to prevent the next short-circuit period from being prolonged, to suppress disturbance of the short-circuit period, and to help stabilize the short-circuit period.

  According to the present invention, in arc welding that repeats forward feeding and reverse feeding as the wire feed speed, by stabilizing the short-circuit cycle, it is possible to improve welding quality and reduce the amount of spatter generated due to micro short-circuit, The present invention is industrially useful as an arc welding control method and an arc welding apparatus for performing arc welding while continuously feeding a welding wire as a consumable electrode.

1 Input power 2 Main transformer (transformer)
3 Primary side rectification part 4 Switching part 5 DCL (reactor)
6 Secondary side rectification unit 7 Welding current detection unit 8 Welding voltage detection unit 9 Short circuit detection unit 10 Short circuit time detection unit 11 Short circuit / arc detection unit 12 Output control unit 13 Short circuit control unit 14 Arc control unit 15 Welding condition setting unit 16 Wire Feeding speed control unit 17 Wire feeding speed detection unit 18 Calculation unit 19 Forward feed / reverse feed switching timing control unit 20 Arc welding apparatus 21 Work piece 22 Welding wire 23 Arc 24 Welding tip 25 Wire feeding unit

Claims (7)

Wire feeding speed in which welding wire feeding is periodically changed at a predetermined cycle and a predetermined amplitude alternately between forward feeding performed in the direction of the welding object and reverse feeding performed in the opposite direction to the normal feeding. Is a consumable electrode type arc welding control method in which welding is performed by repeating an arc period and a short-circuit period, and when the short-circuit period continues for a predetermined period or longer, the wire feed speed of reverse feed is An arc welding control method for controlling to a value having a larger absolute value than a wire feeding speed of reverse feeding when the predetermined period is reached. Wire feeding speed in which welding wire feeding is periodically changed at a predetermined cycle and a predetermined amplitude alternately between forward feeding performed in the direction of the welding object and reverse feeding performed in the opposite direction to the normal feeding. Is a consumable electrode type arc welding control method in which welding is performed by repeating an arc period and a short-circuit period,
If the short-circuit period after starting the short circuit is longer than the previous short-circuit period, the absolute value of the reverse wire feed speed is greater than the reverse wire feed speed at the end of the previous short-circuit period. Arc welding control method to control to value. Wire feeding speed in which welding wire feeding is periodically changed at a predetermined cycle and a predetermined amplitude alternately between forward feeding performed in the direction of the welding object and reverse feeding performed in the opposite direction to the normal feeding. Is a consumable electrode type arc welding control method in which welding is performed by repeating an arc period and a short-circuit period,
If the short-circuit period after the start of the short circuit becomes longer than the average value of one or more previous short-circuit periods, the reverse feed wire feed speed is set to the average reverse feed speed at the end of the previous short-circuit period. An arc welding control method in which the absolute value is controlled to a larger value. The arc welding control method according to any one of claims 1 to 3, wherein when the short-circuit period continues for a predetermined period or longer, the welding current is controlled to a value larger than the welding current at the time when the predetermined period is reached. The slope of the reverse wire feed speed when the short circuit period continues for the predetermined period or more is an absolute value of the slope of the reverse wire feed speed when the short circuit period reaches the predetermined period. The arc welding control method according to claim 1, wherein the arc welding control method is controlled to a large value. The slope of the wire feed speed from reverse feed to forward feed is controlled to a different value depending on the time from when the short-circuit period reaches the predetermined period to when the short-circuit is opened. The arc welding control method according to any one of the above. The arc welding control method according to claim 1, wherein the welding wire is made of a material having high thermal conductivity such as aluminum, aluminum alloy, copper, or copper alloy.

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