JP2009183988A - Method for controlling arc welding, and arc welding apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that, in a system for controlling the welding output current immediately after the regeneration of the arc to the current according to the short-circuit release current so as to be higher than the welding output current immediately before the regeneration of the arc during the predetermined period, the short-circuit release currents during the welding are less matched but varied, and because the welding output current immediately after the regeneration of the arc also outputs different welding current, the arc length is always different, the arc is relatively unstable, the short-circuit period is fluctuated, and the spatter is increased. <P>SOLUTION: Two control methods can be changed between the control of outputting the welding current for the predetermined time according to the short-circuit release current immediately after detecting the arc, and the control of outputting the welding current of the fixed value for the predetermined period. The amount of spatter is reduced by using two controls according to the identification between the arc start period and the stationary welding period, and the intensity of the short-circuit state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, welding is performed by alternately generating a short circuit and an arc between a welding wire and a base material while feeding a welding wire (hereinafter referred to as a wire) as a consumable electrode to a workpiece (hereinafter referred to as a base material). The present invention relates to an arc welding control method and an arc welding apparatus.

  Conventionally, in the field of welding, it is desired to reduce spatter adhesion to a base material. At present, the amount of spatter generated during welding has been reduced due to technological progress, and the adhesion of spatter to the base material has also been reduced. However, at the time of arc start when performing high-speed welding, or in situations where disturbances such as misalignment of workpieces (hereinafter referred to as base material) and gaps are likely to occur, the arc state becomes unstable and spatter is likely to occur. Become. If the generation of spatter is reduced, the welding quality can be improved. In addition, since the adhesion of spatter to the base material or jig can be reduced, the work environment can be improved, such as improved maintainability.

  A conventional arc welding control method is an arc welding control method in which a base metal is welded by alternately repeating a short-circuit period in which a welding wire is short-circuited with a base material and an arc period in which an arc is regenerated and arc-discharged. It is known to control the welding output current immediately after re-generation so as to be higher than the welding output current immediately before the re-occurrence of arc for a set predetermined period (see, for example, Patent Document 1). Further, in this Patent Document 1, the welding output current is steepened immediately before the arc re-generation before a predetermined period in which the welding output current immediately after the arc re-generation is controlled to be higher than the welding output current immediately before the arc re-generation. It also describes the point of control so that it is lowered.

  FIG. 7 is a diagram illustrating a welding current waveform at the time of short-circuit transition in consumable electrode arc welding, in which the horizontal axis represents elapsed time and the vertical axis represents welding current. In FIG. 7, 101 is a short-circuit period in which the wire and the base material are short-circuited, 102 is an arc period in which an arc is generated between the wire and the base material, and 103 is an arc re-occurrence point at which the short-circuit is released and the arc is re-generated. , 104 is the current immediately before the arc re-generation, 107 is the initial arc current value, and 108 is the initial arc control time. In FIG. 7, the arc is regenerated due to the opening of the short circuit at the time of arc reoccurrence 103. Starting from the arc re-occurrence point 103, the initial control time 108 is measured by a timer unit (not shown).

Then, an arc initial control unit (not shown) performs control so that the welding output current at the arc initial control time 108 becomes the arc initial current value 107. At this time, the arc initial current value 107 set as the control target is set to a value higher than the current 104 immediately before the arc reoccurrence. The arc initial current value 107 is output from a setting unit (not shown). The set current, setting voltage, or other wire feed speed, other types of wire feeding speed, shield gas type, wire type, and wire input to the setting unit are set. It is set based on at least one of diameter, welding method, and the like.
JP 2006-021227 A

  The conventional output control method is such that the welding output current immediately after the arc re-generation is set higher than the welding output current immediately before the arc re-generation for a predetermined period, and a predetermined value is added to the short-circuit open current or a predetermined value is set. Control is performed according to the short-circuit open current, such as multiplying by a coefficient. However, since the short-circuit opening currents at the respective opening time points during welding hardly coincide with each other and vary, the welding output current immediately after the arc is regenerated also outputs different welding currents according to the short-circuit opening current. As a result, the arc length is constantly different, the short-circuit cycle is likely to fluctuate, and the arc is relatively unstable.

  If a large fluctuation in the short-circuit period or a large fluctuation in the arc length occurs, the short-circuited wire cannot be opened smoothly or a short-circuit occurs, resulting in an increase in spatter generation. There is.

  Therefore, in a steady welding period in which stable welding is possible, it is conceivable that the welding current immediately after the arc is regenerated is output as a fixed value (fixed value) for a predetermined time.

  On the other hand, until the molten pool is completely formed in the base metal, during the arc start period where the arc is likely to become unstable, it is necessary to control to output the welding current immediately after the arc is regenerated for a predetermined time according to the short-circuit opening current. It is done.

  The reason is that immediately after the arc start, it is difficult to melt the short-circuited wire tip until the melt pool is formed and to open the short circuit, and it is necessary to supply more electric energy than during the steady welding period. Therefore, there are many cases where the short circuit opening current is inevitably increased and the short circuit state becomes stronger. Here, the fact that the short circuit state is strong means that the electric energy which is the area of time × current is high. If a welding current with a fixed value is output for a predetermined time immediately after arc detection in such a state, the size of the droplet formed at the tip of the wire formed during the arc period becomes small, and the short-circuit state at the next short-circuit becomes strong. End up. In the worst case, the wire cannot be completely melted and melts and bounces off, resulting in arc start mistakes such as arc breakage.

  Therefore, it is considered that a method of outputting the welding current immediately after the arc detection corresponding to the strength of the short circuit state for a predetermined time immediately after the arc start and controlling flexibly according to the short circuit state is suitable.

  In addition, even during steady welding in a stable arc state, if there is a disturbance such as a displacement of the workpiece or a gap in the workpiece shape, the short circuit may become strong and weak, and the arc becomes unstable. It is easy to generate spatter. Therefore, even during the steady welding period, it is considered necessary to properly use the control according to the short-circuit open current or the control of the fixed value for the welding current immediately after the arc is regenerated due to the strength of the short-circuit state.

  The reason is the same as the mechanism in which the arc becomes unstable immediately after the arc start. In some cases, the short-circuit open current becomes high due to disturbance in the steady welding period, and the short-circuit state becomes strong. If the control is such that a fixed welding current is output for a predetermined time immediately after the arc detection, the size of the droplet formed at the tip of the wire formed during the arc period becomes small, and the short-circuit state at the next short-circuit becomes strong. This is because, in the worst case, the arc unstable state may be continued after this.

  Therefore, the present invention relates to two types of control, such as a control for outputting a welding current corresponding to a short-circuit release current for a predetermined time immediately after arc detection, and a control for outputting a fixed value welding current for a predetermined time regardless of the short-circuit opening current. By distinguishing between the arc start period and the steady welding period and the strength of the short-circuit state, the two types of control are used separately to reduce spatter and achieve consumable electrode arc welding that is resistant to the effects of disturbances by increasing the welding speed. The purpose is to do.

  In order to solve the above-mentioned problem, the consumable electrode arc welding method of the present invention is a consumable electrode arc welding method in which a short circuit and an arc are alternately repeated between a wire that is a consumable electrode and an object to be welded. The welding current immediately after the arc re-occurrence is controlled to output a current that is the same or increased or decreased as the short-circuit open current according to the short-circuit open current at the time of short-circuit open, and the welding current immediately after the arc re-occurrence is short-circuit open. The welding is performed by switching the control to output a fixed current set in advance for a predetermined time regardless of the short-circuit opening current.

  In addition to the above, the consumable electrode type arc welding method of the present invention outputs, for a predetermined time, a current that is the same or increased or decreased as the short-circuit open current according to the short-circuit open current at the time of short-circuit open as the welding current immediately after the arc re-occurrence. Control and control to output a preset fixed current for a predetermined time regardless of the short-circuit opening current at the time of short-circuit opening as the welding current immediately after arc re-occurrence is switched based on the short-circuit opening current for welding. is there.

  Further, in addition to the above, the consumable electrode type arc welding method of the present invention is based on the short-circuit opening current at the time of short-circuit opening as the welding current immediately after the arc is regenerated when the short-circuit opening current is larger than a preset threshold value. Control is performed to output a current that is the same as or increased or decreased as the short-circuit open current for a predetermined time.If the short-circuit open current is smaller than a preset threshold value, the short-circuit open current at the time of short-circuit open is used as the welding current immediately after the arc is regenerated. Regardless of the control, a preset fixed current is output for a predetermined time.

  In addition to the above, the consumable electrode type arc welding method according to the present invention includes an arc start period and a steady welding period after the arc start period. In accordance with the short-circuit open current, control is performed to output the same or increased current as the short-circuit open current for a predetermined time, and in the steady welding period, the welding current immediately after the arc is regenerated is irrespective of the short-circuit open current at the time of short-circuit open. Control for outputting a preset fixed current for a predetermined time is performed.

  Further, in addition to the above, the consumable electrode arc welding method of the present invention has a short-circuit opening as a welding current immediately after the arc re-occurrence when the short-circuit opening current is larger than a preset threshold value during the steady welding period. In accordance with the short-circuit open current at the time, control is performed to output the same or increased current as the short-circuit open current for a predetermined time, and when the short-circuit open current is smaller than a preset threshold, the welding current immediately after the arc is regenerated Control is performed to output a preset fixed current for a predetermined time irrespective of the short-circuit opening current at the time of short-circuit opening.

  In addition to the above, the consumable electrode type arc welding method of the present invention detects the necking of the wire that occurs in the short-circuit cycle, reduces the welding current from the welding current at the time of detecting the necking, and then reduces the welding current immediately after the arc is regenerated. Control is performed.

  The arc welding apparatus of the present invention is an arc welding apparatus that performs welding by alternately repeating short-circuiting and arcing between a wire that is a consumable electrode and an object to be welded, and a switching unit that controls a welding output; A drive unit that controls the switching unit, a welding current detection unit that detects a welding current, a welding voltage detection unit that detects a welding voltage, and a short-circuit state or an arc state based on the output of the welding voltage detection unit A short-circuit / arc detection unit for detecting whether there is a short-circuit control unit for receiving a signal indicating a short-circuit state from the short-circuit / arc detection unit and outputting a welding output control signal at the time of a short-circuit to the drive unit; An arc control unit that receives a signal indicating an arc state from the short-circuit / arc detection unit and outputs a welding output control signal during arcing to the driving unit, and outputs a set arc start period. An arc start period output unit, a predetermined time setting unit that outputs a set predetermined time, and a fixed value current setting unit that outputs a preset fixed value current to an arc current control unit described later, the arc control The unit has an arc current control unit that outputs a welding output control signal to the drive unit, and has a time measuring function, and inputs a signal from the arc start period output unit and a signal from the predetermined time setting unit. The arc current control unit includes a timing unit that outputs whether the arc start period and the predetermined time or not, and in the arc start period, the welding current immediately after the occurrence of the arc is short-circuited when the short-circuit is opened. In accordance with the open current, control is performed to output the same or increased current as the short-circuit open current for the predetermined time, and during the steady welding period after the arc start period, The fixed-value current set in advance regardless welding current raw immediately after the short circuit opening current during short-circuit opening and performs control for outputting the predetermined time.

  The arc welding apparatus of the present invention is an arc welding apparatus that performs welding by alternately repeating short-circuiting and arcing between a wire that is a consumable electrode and an object to be welded, and a switching unit that controls a welding output; A drive unit that controls the switching unit, a welding current detection unit that detects a welding current, a welding voltage detection unit that detects a welding voltage, and a short-circuit state or an arc state based on the output of the welding voltage detection unit A short-circuit / arc detection unit for detecting whether there is a short-circuit control unit for receiving a signal indicating a short-circuit state from the short-circuit / arc detection unit and outputting a welding output control signal at the time of a short-circuit to the drive unit; An arc control unit that receives a signal indicating an arc state from the short-circuit / arc detection unit and outputs a welding output control signal during arcing to the drive unit, and a predetermined output for a set predetermined time And a fixed value current setting unit that outputs a preset fixed value current to an arc current control unit to be described later, and the short circuit control unit is for setting a threshold value for comparison with the short circuit open current. It will be described later whether the short circuit open current is larger than the threshold by comparing the short circuit open current input from the short circuit current threshold setting unit and the short circuit open current input from the welding current detection unit with the threshold set by the short circuit current threshold setting unit. A determination unit that outputs to the arc current control unit, the arc control unit having a timekeeping function and an arc current control unit that outputs a welding output control signal to the drive unit, from the predetermined time setting unit A timing unit that inputs a signal and outputs whether or not the predetermined time has passed to the arc current control unit, and when the short-circuit open current is larger than the preset threshold, welding immediately after the arc is regenerated Current In response to the short-circuit opening current at the time of opening of the loop, control is performed to output the same or increased current as the short-circuit opening current for the predetermined time, and when the short-circuit opening current is smaller than the preset threshold, The welding current is controlled so as to output a preset fixed current for the predetermined time regardless of the short-circuit opening current at the time of short-circuit opening.

  As described above, according to the present invention, it is possible to switch between two types of control immediately after arc detection: control for outputting a welding current corresponding to the short-circuit release current for a predetermined time and control for outputting a fixed value welding current for a predetermined time. A consumable electrode type that is resistant to the influence of disturbances by increasing the welding speed while reducing spatter by distinguishing between the arc start period and the steady welding period, and by using the above two types of controls properly depending on the strength of the short circuit state. Arc welding can be realized.

  Hereinafter, a consumable electrode type arc welding control method and an arc welding apparatus will be described with reference to the drawings.

  FIG. 1 shows a welding current waveform and a welding voltage waveform when a welding current corresponding to the short circuit opening current is output for a predetermined time immediately after the arc is regenerated. The welding current corresponding to the short circuit open current is the same current as the short circuit open current, or a current higher or lower than the short circuit open current. And, regarding the welding current immediately after the re-occurrence of the arc being the same as or increasing or decreasing the short-circuit opening current, it differs depending on various welding conditions, and can be obtained in advance by experiments, for example. FIG. 1 shows an example in which the welding current immediately after the arc is regenerated is the same as the short-circuit opening current. Further, the above-mentioned predetermined time can also be obtained by, for example, experiments.

  FIG. 2 shows the welding current waveform when the welding current immediately after the arc is regenerated does not correspond to the short circuit opening current but is set to a predetermined fixed value (absolute value), and the welding current set to this fixed value is output for a predetermined time. The welding voltage waveform is shown.

  1 and 2, P1, P3, P5, and P7 indicate points in time when a short circuit occurs, and P2, P4, P6, and P8 indicate points in time when an arc is regenerated. The period from P1 to P2 is the short circuit period S1, the period from P2 to P3 is the arc period A1, the period from P3 to P4 is the short circuit period S2, the period from P4 to P5 is the arc period A2, and from P5 The period of P6 is the short circuit period S3, the period of P6 to P7 is the arc period A3, and the period of P7 to P8 is the short circuit period S4. A period during which a predetermined welding current is output immediately after the arc is regenerated is defined as a predetermined time T1.

(Embodiment 1)
In FIG. 1, the period from P1 to P3 (one short circuit period) will be described first.
P1 is when a short circuit occurs, P2 is when an arc is regenerated, and P1 to P2 is a short circuit period S1. In this short-circuit period S1, the consumable electrode wire is in contact with the molten pool and short-circuited, and the welding current is gradually increased to release the short-circuit, and the electric energy is supplied to the wire so that the wire is Can be melted. As a result, the wire and the molten pool are separated from each other and a short circuit is opened, and an arc is generated at the point P2.

P2 is the time of arc re-occurrence, P3 is the time of the next short-circuit occurrence, and control is performed so that a welding current corresponding to the short-circuit open current is output for a predetermined time T1 immediately after the P2 arc re-occurrence. In the example of FIG. 1, an example in which the welding current during the predetermined time T1 is the same as the short-circuit opening current is shown. After the predetermined time T1, the current corresponding to the voltage control is output until P3 which is the next short-circuit occurrence point.
The period from P1 to P3 is one short circuit period, and the short circuit period is repeated as in the period from P3 to P5 and the period from P5 to P7.

  As shown in FIG. 1, in the short circuit period S1, an example in which the short circuit open current is 300 A is shown, and the case where this short circuit open current is 300 A is assumed to be an appropriate state. And the short circuit state in this case is made appropriate, and the short circuit state is neither strong nor weak. In addition, when the electrical energy represented by the product of the current and time during the short circuit period is larger than the electrical energy at the time of the short circuit release current 300A, the short circuit state is referred to as strong, and when the electrical energy is small, the short circuit state is referred to as weak. And

  In the arc period A1 after the short-circuit period S1, a welding current having the same value corresponding to the short-circuit opening current 300A is output as the welding current output for a predetermined time T1 immediately after the occurrence of the arc again. Therefore, the electric energy is appropriate, and thereby the size of the droplet at the wire tip is also appropriate. And the arc length tends to be appropriate.

  In the short circuit period S2, the example in which the short circuit time is shorter than the short circuit period S1 and the short circuit opening current is 250A lower than the appropriate value 300A is shown, and the short circuit state is weak. A welding current having the same value corresponding to the short-circuit opening current 250A is output as the welding current output for a predetermined time T1 immediately after the arc is regenerated in the arc period A2. Therefore, since there is little electric energy, the size of a droplet becomes smaller than an appropriate state. Also, the arc length is shortened. Therefore, the timing of the next short circuit tends to be advanced.

  In the short circuit period S3, an example in which the short circuit time is long and the short circuit open current exceeds the appropriate value 300A and reaches 350A is shown, and the short circuit state is strong.

  In the arc period A3, the welding current output for a predetermined time T1 immediately after the reoccurrence of the arc is 350A having the same value corresponding to the short circuit opening current 350A. Therefore, since the electric energy is large, the size of the droplet becomes larger than the appropriate state. In addition, the arc length becomes longer. Therefore, the next short circuit timing tends to be delayed.

  As described above, since the magnitude of the short-circuit opening current is different and the magnitude of the welding current output for a predetermined time T1 immediately after the arc is regenerated is different, the arc length at the time of the arc is different and the short-circuit period is changed. It tends to occur.

  It is to be noted that it is appropriate not to perform control that easily causes fluctuations in the short-circuit cycle when the arc stability such as the steady welding period after the arc start period is obtained. Etc.

Further, the welding current output for a predetermined time corresponding to the short circuit opening current is the same current value as the short circuit opening current in FIG. 1, but is not limited to the same, and may be a value increased or decreased with respect to the short circuit opening current. For example, it is good also as short circuit open current +/- 100A. And whether to make it the same or to increase / decrease can be decided beforehand, for example by conducting an experiment.
Next, control suitable for a state in which arc stability such as a steady welding period is obtained will be described with reference to FIG. In addition, the same code | symbol as FIG. 1 is attached | subjected about the location similar to FIG.

  In the short circuit period S1, it is assumed that the short circuit state is neither strong nor weak, and the short circuit open current is appropriate at 300A. In the arc period A1, a predetermined fixed value of 300A is output as the welding current output for a predetermined time T1 immediately after the reoccurrence of the arc. Therefore, since electric energy is appropriate, the size of melting is also appropriate. Also, the arc length tends to be appropriate.

  In the short circuit period A2, an example in which the short circuit state is weak and the short circuit time is short, and the short circuit opening current is 250A lower than the appropriate value 300A is shown. In the arc period A2 after the short-circuit period A2, 300 A, which is a fixed value similar to the arc period A1, is output as the welding current that is output for a predetermined time T1 immediately after the reoccurrence of the arc. This is also because the electric energy is appropriate due to the output of the fixed value 300A, the size of the melting is also appropriate, and the arc length is likely to be appropriate.

  In the short-circuit period A3, the short-circuit open current has reached 350A, which is higher than the appropriate value 300A, but the welding current output during the predetermined time T1 immediately after the arc re-occurrence in the arc period A3 is the arc period A1 and the arc period A2. Similarly, a fixed value of 300A is output. Again, since the electric energy is appropriate due to the output of the fixed value 300A, the amount of melting is also appropriate, and the arc length is likely to be appropriate.

  However, in the arc start period before the steady welding period, there is a strength of the short circuit state until the molten pool in the arc start period is completely formed, and the arc tends to become unstable. In a state where the arc is likely to become unstable, it is appropriate to perform the control according to the short-circuit open current instead of the fixed value for the welding current output for a predetermined time T1 immediately after the arc is regenerated.

  The reason for this is that if the welding current output at the predetermined time T1 immediately after the arc is regenerated is a welding current corresponding to the short circuit opening current, the arc is regenerated when the short circuit is strong and the size of the droplet at the tip of the wire is increased. It is because the next short circuit state can be relieved by increasing the length.

  On the other hand, when the welding current has a fixed value, the size of the droplet at the tip of the wire is small and cannot be burned up, the next short-circuit state becomes strong, and the arc is unlikely to reoccur. In the worst case, it is possible that the tip of the wire cannot be melted and flies off due to wire fusing.

  Therefore, when the arc is likely to become unstable as in the arc start period, it is appropriate to output a welding current corresponding to the short-circuit open current for a predetermined time, and the arc is likely to be stable during the steady welding period. In this case, it was found through experiments and the like by the inventors that a control for outputting a fixed welding current for a predetermined time is appropriate.

  FIG. 3 shows a control for outputting a welding current corresponding to the short-circuit opening current for a predetermined time in the arc start period TS in a state where the arc is likely to be unstable, and a fixed value in the steady welding period TN in which the arc is likely to be stable. An example of the timing of proper use of control for performing a control for outputting a welding current for a predetermined time is shown.

  In FIG. 3, the welding current output for a predetermined time T1 immediately after the arc is regenerated is short-circuited at the time when the wire feeding speed WF reaches the steady feeding speed that is the feeding speed during the steady welding period. An example is shown in which two types of control are switched, such as a welding current corresponding to an open current or a current having a fixed value. That is, until the steady feeding speed is reached, the welding current output for a predetermined time T1 immediately after the re-occurrence of the arc is set as the current corresponding to the short-circuit opening current as the arc start period TS, and the steady feeding speed is reached after the steady feeding speed is reached. The welding current output for a predetermined time T1 immediately after the arc is regenerated as the welding period TN is set to a fixed value.

  However, the control switching timing is not limited to this. For example, as shown in FIG. 3, the current at the start of welding is detected, the time from this current detection is counted, and a predetermined elapsed time is used as a trigger. Two types of control may be switched.

  Next, the arc welding apparatus in the present embodiment that performs the above control will be described with reference to FIG. FIG. 4 is a diagram showing a schematic configuration of the arc welding apparatus in the present embodiment.

  The electric power from the input power source 1 is rectified by the primary rectification unit 2, converted into alternating current by the switching element 3, stepped down by the transformer 4, rectified by the secondary rectification unit 5 and DCL (inductance, coil) 6, and wire 20 and the base material 23. Also, a drive unit 7 for controlling the switching element 3, a welding voltage detection unit 8 connected between the power supply output terminals for welding and detecting the welding voltage, a welding current detection unit 9 detecting the welding current, A short-circuit / arc detection unit 10 that determines whether it is a short-circuit period or an arc period based on a signal from the welding voltage detection unit 8, a short-circuit control unit 11 that outputs a signal for controlling a current during the short-circuit period, and an arc An arc control unit 15 that outputs a signal for controlling the current during the period, and an arc start period output unit 18 that outputs a preset arc start period for the arc control unit 15 are provided. The short-circuit control unit 11 includes a short-circuit current control unit 12 that outputs a current control signal to the drive unit 7. The arc control unit 15 includes a time measuring unit 16 that measures time, and an arc current control unit 17 that outputs a current control signal for the arc period to the driving unit 7 based on a signal from the time measuring unit 16. Further, a predetermined time setting unit 24 for setting the predetermined time T1 and a fixed value current setting unit 25 for setting a current to be output during the predetermined time T1 are provided. Further, the wire 20 is fed in the direction of the base material 23 by the wire feed motor 19, and the wire 20 is supplied with power through the chip 21, and an arc 22 is generated between the wire 20 and the base material 23.

  In addition, each component which comprises the arc welding apparatus shown in FIG. 4 may each be comprised independently, and you may make it comprise combining a some component.

Next, arc control after determination by the short circuit / arc detection unit 10 will be described.
The short-circuit control unit 11 includes a short-circuit current control unit 12 that controls a current during a short-circuit period in order to supply the wire 20 with a welding current for opening a short-circuit state in which the wire is in contact with or short-circuited with the molten pool. ing.

  The arc start period output unit 18 outputs the arc start period (time) to the timer unit 16. The time measuring unit 16 obtains the time of the arc start period from the arc start period output unit 18 and further measures, for example, the elapsed time since the torch switch of the welding torch (not shown) is turned on, and the arc start period based on these information Or whether it is a steady welding period is output to the arc current control unit 17. In addition, the time measuring unit 16 obtains a predetermined time from the predetermined time setting unit 24, further measures the time from the occurrence of the arc based on the signal from the short circuit / arc detection unit 10, and based on the information, the predetermined period T1. Is output to the arc current control unit 17.

  The arc current control unit 17 receives the signal from the time measuring unit 16 and sets the welding current output for a predetermined time T1 immediately after the re-occurrence of the arc due to short circuit opening to a current corresponding to the short circuit opening current, or short circuit opening. Control whether to set a fixed value regardless of current. The fixed value of the welding current is based on a signal from the fixed value current setting unit 25.

  Then, immediately after the arc is regenerated, a welding current corresponding to the short-circuit opening current is output during the arc start period, and a fixed welding current set in advance regardless of the short-circuit opening current during the steady welding period. Will be output.

  As described above, during the arc start period when the arc is likely to become unstable, control is performed to output a welding current according to the short-circuit open current, and during the steady welding period when the arc is likely to be stable, a fixed value is set. It is possible to suppress adverse effects on the production efficiency and work environment by controlling the output of the welding current and using different control methods in this way.

(Embodiment 2)
In the present 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 in the steady welding period, when the arc is likely to be stable, control is performed so that the welding current has a fixed value for a predetermined time T1 immediately after the reoccurrence of the arc. Even during the period, only when the arc becomes unstable due to disturbance or the like, during the predetermined time T1 immediately after the re-occurrence of the arc, the control is performed so as to output the welding current corresponding to the short-circuit opening current. The point is that the control is switched during the period. Specifically, a short circuit open current threshold is set, and control is switched depending on whether or not the short circuit open current exceeds this threshold.

FIG. 5 shows a welding current waveform in consumable electrode arc welding in which a short circuit and an arc are alternately repeated. FIG. 5 shows that the magnitude of the short-circuit open current is different when the arc becomes unstable due to disturbances such as misalignment and gap of the base material 23 in the steady welding period in which the arc is likely to be stable. It is a figure explaining the example which switches and controls two types of control when it generate | occur | produces.
P11 is when a short circuit occurs, P12 is when an arc is regenerated, and P11 to P12 are the short circuit period S11. The arc period A11 is from P12 to P13 when a short circuit occurs.

First, the arc shown in FIG. 5A is in a stable state. In the short circuit period S11, the short circuit state is weak, so the short circuit time is short, and the short circuit open current is 200A. Therefore, since it does not exceed the preset short-circuit current threshold of 250A, the welding current output during the predetermined time T1 immediately after the arc re-occurrence in the arc period A11 is a preset fixed value regardless of the short-circuit open current. Of 300A is output.
Similarly, since the arc is stable without exceeding the short-circuit current threshold 250A after the short-circuit period S12, the same control is performed in the short-circuit period S11 and the arc period A11.

  Next, in the case where the unstable state of the arc shown in FIG. 5B occurs, the short circuit period is long in the short circuit period S11 because the short circuit condition is strong, and the short circuit open current reaches 350A. Therefore, since it exceeds 250 A which is a preset short-circuit current threshold, the welding current output for a predetermined time T1 immediately after the arc re-occurrence in the arc period A11 outputs 350 A corresponding to the short-circuit open current.

  In the next short circuit period S12, since the short circuit state is weak, the short circuit open current is 200A. Since the short-circuit current threshold value 250A is not exceeded, the welding current output for a predetermined time T1 immediately after the arc re-occurrence in the arc period A12 outputs a preset fixed value 300A regardless of the short-circuit open current.

  In the next short circuit period S13, since the short circuit state is strong, the short circuit time is long, and the short circuit open current also reaches 400A. Therefore, since it exceeds the short-circuit current threshold 250A, the welding current output for a predetermined time T1 immediately after the occurrence of the arc again in the arc period A13 is output 400A according to the short-circuit open current.

  In addition, although the welding current output for a predetermined time according to the short circuit open current shows the same current as the short circuit open current in FIG. 5B, it may be increased or decreased with respect to the short circuit open current (for example, short circuit open). Current ± 100 A).

  Moreover, although the example of the control which outputs the welding current according to the short circuit open current during the predetermined time T1 when exceeding the short circuit current threshold is shown, the following control can be substituted. For example, a second fixed value welding current that is higher than a normal fixed value welding current by control for outputting a fixed value welding current for a predetermined time may be provided (for example, with respect to the normal welding current 300A, 2 fixed value welding current 400A).

  As described above, the welding state is not always stable, and may become unstable due to disturbance or the like. Even in the steady welding period, in a state where there is a strength of a short-circuit state and the arc is likely to become unstable, the control for setting the welding current output for a predetermined time T1 immediately after the occurrence of the arc to a predetermined fixed value is performed. However, it is appropriate to control the welding current to be output for a predetermined time according to the short circuit opening current.

  The reason is that if the welding current output for a predetermined time T1 immediately after the arc re-generation is a fixed value of the welding current, the size of the droplet at the tip of the wire becomes smaller at the time of the arc re-generation when the short circuit is strong, It cannot be burned up and the next short circuit condition cannot be relaxed.

  Therefore, with a fixed welding current, the next short-circuit state becomes strong and the arc is less likely to reoccur. In the worst case, the tip of the wire cannot be melted and it is possible that the wire will blow off due to the wire fusing.

  From the above, when the arc is likely to be unstable, the welding current corresponding to the short-circuit open current is controlled from the control that outputs a fixed value welding current that is performed when the arc is likely to be stable during the steady welding period. It has been found through experiments by the inventors that switching to the output control is more appropriate.

  Next, an arc welding apparatus that performs the above-described control in the present embodiment will be described with reference to FIG.

  FIG. 6 is a diagram showing a schematic configuration of the arc welding apparatus in the present embodiment. Parts similar to those in FIG. 4 described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The main point in which the configuration of FIG. 6 is different from the configuration of FIG. The short-circuit control unit 11 includes a short-circuit current control unit 12 that outputs a current control signal to the drive unit 7 during the short-circuit period, a short-circuit current threshold setting unit 13 for setting a short-circuit current threshold, and a short-circuit current threshold setting unit 13. And a determination unit 14 that determines whether or not the short-circuit open current exceeds a short-circuit current threshold based on the signal and the signal from the welding current detection unit 9 and outputs the determination result to the arc current control unit 17.

  Next, short-circuit control after determination by the short-circuit / arc detection unit 10 will be described.

  The short-circuit control unit 11 includes a short-circuit current control unit 12, a short-circuit current threshold setting unit 13, and a short-circuit current threshold detection unit 14. The determination unit 14 inputs the threshold value from the short-circuit current threshold setting unit 13 and monitors the current by a signal from the current detection unit 9, and the welding current exceeds a predetermined threshold set in the short-circuit current threshold setting unit 13. It is determined whether or not. Then, the arc current control is performed by determining whether the welding current output for a predetermined time T1 immediately after the re-occurrence of the arc due to the short circuit opening is a current output corresponding to the short circuit opening current or a fixed current output. This is output to the unit 17.

  Then, depending on the strength of the short circuit state when the disturbance occurs, a welding current corresponding to the short circuit open current is output if the short circuit current threshold is exceeded, and a fixed value welding current is output if the short circuit current threshold is exceeded.

  As described above, during the steady welding period in which the arc is likely to be stable, a fixed value welding current is output for a predetermined time. It is possible to selectively use the control to output a welding current according to the predetermined time, and to suppress adverse effects on the production efficiency and work environment.

  The present invention can switch between two types of control immediately after arc detection: a control for outputting a welding current corresponding to a short-circuit release current for a predetermined time and a control for outputting a fixed value welding current for a predetermined time. Sputtering can be reduced by distinguishing between the steady welding period and the strength of the short circuit state by using the above two types of control properly, which is industrially useful as a welding method and welding apparatus for performing short circuit welding using a consumable electrode.

The figure which shows the welding current waveform and welding voltage waveform in Embodiment 1 The figure which shows the welding current waveform and welding voltage waveform in Embodiment 1 The figure which shows the time change of the arc start period, steady welding period, and wire feeding speed in Embodiment 1. The figure which shows schematic structure of the arc welding apparatus in Embodiment 1. FIG. The figure which shows the welding current waveform in Embodiment 2. The figure which shows schematic structure of the arc welding apparatus in Embodiment 2. Diagram showing welding current waveform in conventional arc welding

Explanation of symbols

T1 Predetermined time TN Steady welding period TS Arc start period 1 Input power supply 2 Primary rectification unit 3 Switching element 4 Transformer 5 Secondary rectification unit 6 DCL (inductance, coil)
7 Drive unit
DESCRIPTION OF SYMBOLS 8 Welding current detection part 9 Welding voltage detection part 10 Short circuit / arc detection part 11 Arc control part 12 Short circuit control part 13 Short circuit current threshold value setting part 14 Judgment part 15 Arc control part 16 Timekeeping part 17 Arc current control part 18 Arc start period output Part 19 Wire feed motor 20 Wire 21 Tip 22 Welding arc 23 Base material 24 Predetermined time setting part 25 Fixed value current setting part

Claims (8)

A consumable electrode arc welding method in which welding is performed by alternately repeating short-circuiting and arcing between a wire that is a consumable electrode and a workpiece,
A control for outputting a current that is the same as or increased or decreased to the short-circuit open current according to the short-circuit open current at the time of short-circuit open as a welding current immediately after arc re-occurrence, and
A consumable electrode type arc welding method in which welding is performed by switching between a control for outputting a preset fixed current for a predetermined time regardless of a short-circuit opening current at the time of short-circuit opening as a welding current immediately after arc re-occurrence. Control that outputs the same or increased current as the short-circuit opening current according to the short-circuit opening current at the time of short-circuit opening as the welding current immediately after the arc re-generation, and short-circuit opening at the time of short-circuit opening as the welding current immediately after the arc re-generation The consumable electrode type arc welding method according to claim 1, wherein welding is performed by switching between a control for outputting a preset fixed current regardless of the current for a predetermined time based on a short circuit opening current. When the short-circuit opening current is larger than a preset threshold value, a control is performed to output a current equal to or increased from the short-circuit opening current for a predetermined time in accordance with the short-circuit opening current at the time of short-circuit opening as the welding current immediately after the arc is regenerated. Done
When the short-circuit opening current is smaller than a preset threshold value, control is performed to output a preset fixed current for a predetermined time regardless of the short-circuit opening current at the time of short-circuit opening as the welding current immediately after arc re-occurrence. 3. The consumable electrode type arc welding method according to 1 or 2. In the steady welding period after the arc start period and the arc start period,
In the arc start period, a control is performed to output a current that is the same or increased or decreased as the short-circuit open current according to the short-circuit open current at the time of short-circuit open as the welding current immediately after the arc re-generation,
2. The consumable electrode arc welding method according to claim 1, wherein during the steady welding period, control is performed to output a preset fixed current for a predetermined time regardless of a short-circuit opening current at the time of short-circuit opening as a welding current immediately after arc re-occurrence. . When the short-circuit opening current is larger than a preset threshold value during the steady welding period, the welding current immediately after the arc re-occurrence is set to a current equal to or increased from the short-circuit opening current according to the short-circuit opening current at the time of short-circuit opening. Control to output time,
When the short-circuit opening current is smaller than a preset threshold value, control is performed to output a preset fixed current for a predetermined time regardless of the short-circuit opening current at the time of short-circuit opening as the welding current immediately after the arc is regenerated. 4. The consumable electrode type arc welding method according to 4. The arc according to any one of claims 1 to 5, wherein the control of the welding current immediately after the arc is regenerated is performed after detecting the necking of the wire that occurs in the short-circuit cycle and reducing the welding current below the welding current at the time of detecting the necking. Welding method. An arc welding apparatus that performs welding by alternately repeating short-circuiting and arcing between a wire that is a consumable electrode and an object to be welded,
A switching unit for controlling the welding output;
A drive unit for controlling the switching unit;
A welding current detector for detecting a welding current;
A welding voltage detector for detecting the welding voltage;
A short-circuit / arc detection unit for detecting whether a short-circuit state or an arc state based on an output of the welding voltage detection unit;
A short-circuit control unit that receives a signal indicating a short-circuit state from the short-circuit / arc detection unit and outputs a welding output control signal at the time of a short-circuit to the drive unit;
An arc control unit that receives a signal indicating an arc state from the short-circuit / arc detection unit and outputs a welding output control signal during arcing to the drive unit;
An arc start period output unit for outputting the set arc start period;
A predetermined time setting unit for outputting the set predetermined time;
A fixed value current setting unit that outputs a preset fixed value current to an arc current control unit described later;
The arc control unit
An arc current control unit that outputs a welding output control signal to the drive unit;
It has a time measuring function and inputs a signal from the arc start period output unit and a signal from the predetermined time setting unit to determine whether the arc current control unit is in the arc start period and whether it is the predetermined time. And a timing unit that outputs whether or not
In the arc start period, the welding current immediately after the re-occurrence of the arc is controlled to output a current that is the same or increased or decreased as the short-circuit open current according to the short-circuit open current at the time of short-circuit open,
In the steady welding period after the arc start period, the arc welding apparatus performs control to output the preset fixed current for the predetermined time regardless of the short-circuit open current at the time of short-circuit open for the welding current immediately after the arc re-occurrence . An arc welding apparatus that performs welding by alternately repeating short-circuiting and arcing between a wire that is a consumable electrode and an object to be welded,
A switching unit for controlling the welding output;
A drive unit for controlling the switching unit;
A welding current detector for detecting a welding current;
A welding voltage detector for detecting the welding voltage;
A short-circuit / arc detection unit for detecting whether a short-circuit state or an arc state based on an output of the welding voltage detection unit;
A short-circuit control unit that receives a signal indicating a short-circuit state from the short-circuit / arc detection unit and outputs a welding output control signal at the time of a short-circuit to the drive unit;
An arc control unit that receives a signal indicating an arc state from the short circuit / arc detection unit and outputs a welding output control signal during arcing to the drive unit;
A predetermined time setting unit for outputting the set predetermined time;
A fixed value current setting unit that outputs a preset fixed value current to an arc current control unit described later;
The short-circuit controller is
A short-circuit current threshold setting unit for setting a threshold for comparison with the short-circuit open current;
The short-circuit open current input from the welding current detection unit is compared with the threshold set by the short-circuit current threshold setting unit, and whether or not the short-circuit open current is larger than the threshold is output to an arc current control unit described later. A determination unit,
The arc control unit
An arc current control unit that outputs a welding output control signal to the drive unit;
A time measuring unit that has a time measuring function and inputs a signal from the predetermined time setting unit and outputs whether or not the predetermined time is the arc current control unit;
When the short-circuit opening current is larger than the preset threshold value, a current that is the same as or increased or decreased from the short-circuit opening current according to the short-circuit opening current at the time of short-circuit opening is output for the predetermined time. Control
When the short-circuit opening current is smaller than the preset threshold value, the welding current immediately after the arc is regenerated is controlled to output a preset fixed current for the predetermined time regardless of the short-circuit opening current at the time of short-circuit opening. Arc welding equipment.

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