JP2009125760A - Arc welding method and arc welding equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem involved in a conventional arc welding method: when false detection of constriction of a welding wire during a short-circuit period is determined, the detection sensibility of constriction during the shot-circuited period is decreased, and when the false detection during the shot-circuited period is eliminated as the result of decreasing the detection sensibility of the constriction, the sensibility of the constriction is returned to the standard sensitivity, consequently the false detection of the constriction during the next short-circuit period is apt to occur. <P>SOLUTION: When the false constriction detection occurs in a certain short-circuit period, and a threshold value is increased by a prescribed value so as to decrease the detection sensibility of the constriction so that the false constriction detection does not occur continuously in a short-circuit period on and after the short-circuit period during which the false constriction detection occurs, and furthermore, when the false constriction detection occurs in a later short-circuit period, the threshold value of the constriction detection is more increased. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an arc welding method and an arc welding apparatus that perform welding by alternately generating a short circuit and an arc while feeding a welding wire that is a consumable electrode.

  In recent years, there has been a demand for higher quality of welding quality such as the amount of spatter generated, bead appearance and penetration state. In particular, reducing the occurrence of spatter improves welding quality and prevents spatter adhesion to the jig, thereby improving the work environment such as improving maintainability.

  As a conventional method of reducing spatter, there is known a method of reducing the short-circuit current to a predetermined current when a constriction at the tip of a welding wire as a consumable electrode is detected at the end of a short-circuit, thereby reducing spatter generated when an arc is regenerated. ing.

  As shown in FIG. 7, the conventional consumable electrode type arc welding method detects the necking of the welding wire that occurs at the end of the short circuit, reduces the current for a predetermined period when the necking is detected, If the arc does not regenerate within one predetermined period, it is determined that the neck is erroneously detected, and the current supplied to the welding wire is increased to a predetermined current value after determining that the neck is erroneously detected. A device that prohibits squeezing detection when it is determined to be erroneous detection is known (see, for example, Patent Document 1).

  When it is determined that the constriction is erroneously detected during the previous or predetermined number of short-circuit periods in the past, the constriction detection unit prohibits the constriction detection during the current short-circuit period.

Further, when it is determined that the constriction is erroneously detected during the previous or predetermined number of short-circuit periods in the past, the squeezing detection sensitivity during the current short-circuit period is lowered.
JP 2006-116585 A

  In the conventional arc welding method, when it is determined that the constriction is erroneously detected during the previous or predetermined number of short-circuit periods in the past, the constriction detection during the current short-circuit period is prohibited or the constriction detection sensitivity is lowered. However, if the detection of squeezing is eliminated during the short-circuit period after the next short circuit due to prohibition of squeezing detection or reduction of the squeezing detection sensitivity, the squeezing detection sensitivity during the short-circuit period is the basic sensitivity. It is something to return to. After that, if it is determined again that the constriction is erroneously detected during the previous or predetermined number of short circuit periods, the constriction detection is prohibited again, or the constriction detection sensitivity is lowered. As described above, when the squeezing detection sensitivity is returned, it becomes easy to repeat squeezing erroneous detection, which may cause arc instability.

  This arc welding method can only deal with sudden phenomena such as irregular vibrations in the molten pool and variations in wire feeding, and the arc voltage between the wire tip and the base metal decreases ( For example, when the torch cable or the ground cable is very long, or when the voltage is lowered too much), the short circuit state becomes strong and the short circuit open current increases, so the current change per unit time di / dt also increases. Since the voltage change dv / dt per unit time also becomes high, there is a tendency that it is easily constricted and erroneously detected.

  Also, in the arc start period, unlike the arc state in the steady welding period, the molten pool is not completely formed in the base metal, so the short circuit state is difficult to stabilize, and the short circuit cycle tends to be irregular, so that the constriction is erroneous. It tends to be easy to detect.

  Therefore, in the conventional arc welding method, it is in a state in which it is easy to repeat the false detection of the constriction during the short circuit period, and since there is no consideration in the arc start period in which arc instability is likely to occur, reduction in spatter generation cannot be maintained. . Furthermore, there is a possibility that welding quality such as bead appearance and penetration cannot be secured due to arc instability.

  In order to solve the above-mentioned problems, the arc welding method and the arc welding apparatus according to the present invention provide a welding wire as a consumable electrode to a base material to generate a short circuit period and an arc period alternately. An arc welding method for detecting a constriction of the welding wire that occurs at the end of a period, and determining that a constriction is erroneously detected when no arc is generated within a predetermined period after the constriction is detected. In the short-circuit period, squeezing is detected based on the first squeezing detection threshold. If the squeezing is erroneously detected in the first short-circuiting period, the squeezing detection threshold is larger than the first squeezing detection threshold. The squeezing detection threshold is raised, the squeezing is detected based on the second squeezing detection threshold in the second shorting period after the first shorting period, and the squeezing is detected in the second shorting period. If the neck is erroneously detected, the neck detection threshold is raised to a third neck detection threshold that is larger than the second neck detection threshold. If the neck is not erroneously detected during the second short-circuit period, the second The detection threshold is maintained.

  Further, the arc welding method and the arc welding apparatus according to the present invention are the arc welding that occurs at the end of the short-circuit period in arc welding in which a welding wire that is a consumable electrode is fed to a base material to alternately generate a short-circuit period and an arc period. An arc welding method for detecting a constriction of a welding wire and determining that the constriction is erroneously detected when no arc is generated within a predetermined period after the constriction is detected, wherein the first constriction detection threshold value is detected during a short circuit period. Squeezing is detected based on the number of short-circuiting periods in which the squeezing is falsely detected, the squeezing detection threshold is increased to a second squeezing detection threshold that is larger than the first squeezing detection threshold, In the short-circuit period after the short-circuit period when the squeezing detection threshold is raised to the second detection threshold, the squeezing is detected based on the second squeezing detection threshold, When the number of short-circuit periods in which the constriction is erroneously detected in the short-circuit period after the short-circuit period raised to the second detection threshold reaches a predetermined number, the constriction detection threshold is set to be larger than the second constriction detection threshold. The second squeezing detection threshold is maintained until the number of short-circuit periods in which squeezing is erroneously detected reaches the predetermined number of times.

  Further, the arc welding method of the present invention is an arc welding method having a steady welding period after the arc start period in addition to the above arc welding method, and the increase width for increasing the squeezing detection threshold is the short-circuit period of the steady welding period. The increase width of the arc start period is larger than the increase width of the arc start period.

  In addition to the arc welding method, the arc welding method of the present invention raises the squeezing detection threshold when the squeezing is erroneously detected when the squeezing detection threshold is raised during the short circuit period.

  Further, the arc welding method of the present invention, in addition to the arc welding method described above, changes in the squeezing detection threshold per unit time of the welding voltage or a value obtained by dividing the welding voltage by the welding current. It is a quantity.

  In addition to the arc welding method described above, the arc welding method of the present invention prohibits the detection of the constriction from the determination of the constriction misdetection until the occurrence of an arc during the short-circuit period determined as the constriction misdetection. is there.

  As described above, according to the present invention, false detection of constriction during a short circuit period can be prevented at an early stage, and problems such as arc instability, bead defects, increased spatter, poor penetration, etc. when constriction misdetection occurs. It is possible to improve the welding quality by minimizing. In addition, adverse effects on production efficiency and work environment can be suppressed.

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

(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of an arc welding apparatus.

  The electric power supplied from the input power source 1 to the arc welding apparatus is rectified by the primary rectification unit 2, converted into alternating current by the switching element 3, stepped down by the transformer 4, and rectified by the secondary rectification unit 5 and DCL (inductor) 6. And applied between the welding wire 18 and the base material 21.

  Further, a driving unit 7 for controlling the switching element 3, a welding voltage detection unit 8 for outputting a signal corresponding to a detected voltage connected between the welding power supply output terminals to the short circuit / arc detection unit 10, and a welding current It is determined whether the welding output voltage is equal to or higher than a certain value based on a signal from the welding current detection unit 9 and the welding voltage detection unit 8, and the wire 18 is contact-short-circuited to the base material 21 based on the determination result. Or a short-circuit / arc detection unit 10 that determines whether a welding arc is generated in a non-contact state and outputs a determination signal.

  The arc control unit 11 controls the drive unit 7 to perform output control in the arc period when a signal indicating the arc period is input from the short circuit / arc detection unit 10.

  The short-circuit controller 12 controls the driving unit 7 to perform welding output control during the short-circuit period when a signal indicating that the short-circuit period is input from the short-circuit / arc detector 10.

  The necking detection unit 13 calculates a welding voltage differential value based on the signal from the welding voltage detection unit 8 when the signal indicating that the short-circuiting period is input from the short-circuit / arc detection unit 10, and detects the necking. Compared with a squeezing detection reference threshold that is a reference voltage differential value from the squeezing detection reference threshold setting unit 16 for setting a reference threshold, it is detected whether or not the welding wire 18 is squeezed.

  The squeezing error detection detecting unit 14 detects the squeezing of the squeezing from the time point when the squeezing is detected based on the signal indicating that the squeezing is detected from the squeezing detecting unit 13 and the signal from the short circuit / arc detecting unit 10. When the period is not reached, it is determined that the constriction is erroneously detected.

  The squeezing detection threshold value control unit 15 receives a signal from the squeezing error detection detection unit 14 and outputs to the squeezing detection unit 13 that if the squeezing error is detected, the squeezing detection threshold value is larger than before. In this short circuit period in which the constriction is erroneously detected, a signal that does not detect the constriction is output to the detection unit 13, and the drive unit 7 is controlled to control the welding output in the short circuit period.

  The squeezing detection unit 13, the squeezing erroneous detection detection unit 14, and the squeezing detection threshold value control unit 15 are configured in the short-circuit control unit 12. Moreover, each component part which comprises the arc welding apparatus shown in FIG. 1 may each be comprised independently, and you may make it comprise combining a some component part.

  The welding wire 18 is fed to the base material 21 by the welding wire feeding device 17 and is supplied with electric power via the tip 19 to generate a welding arc 20 with the base material 21.

  Here, the control in the short circuit period after the determination of the short circuit / arc detecting unit 10 will be described.

  The short-circuit control unit 12 includes a constriction detection unit 13, a constriction erroneous detection detection unit 14, and a constriction detection threshold value control unit 15. The constriction detection unit 13 monitors the welding voltage output from the welding voltage detection unit 8. When the welding voltage differential value, which is the rate of change of the welding voltage with time, becomes larger than the squeezing detection reference threshold (first threshold), the squeezing of the welding wire 18 is detected and the current is reduced to a predetermined low current value IN. If no arc is generated even after the lapse of the predetermined time T1, the voltage rises to a predetermined return current value IS2. Thereafter, in this short-circuit period, the squeezing detection by the squeezing detection unit 13 is prohibited and the generation of an arc is awaited. Further, a squeezing detection threshold value set by the squeezing detection reference threshold setting unit 16 in accordance with an instruction from the squeezing detection threshold control unit 15 is increased by a predetermined value as a new squeezing detection threshold (second threshold).

  During the short-circuit period next to this short-circuit period, since the previous constriction was erroneously detected, the constriction detection unit 13 is constricted based on the constriction detection threshold (second threshold) increased during the previous short-circuit period. Perform detection. When a squeezing error detection is detected even in the next short-circuit period, the squeezing detection threshold (second threshold) is further increased by a predetermined value to obtain a new squeezing detection threshold (third threshold). Such control is repeated until the constriction is no longer detected erroneously. As described above, when the constriction is erroneously detected during the short circuit period, the constriction detection threshold value is increased by a predetermined value. If the constriction is not erroneously detected during the short circuit period, the constriction detection threshold value is maintained without increasing.

  FIG. 2 shows temporal changes in the welding current waveform, the welding voltage waveform, and the squeezing detection threshold in consumable electrode arc welding in which a short circuit and an arc are alternately repeated.

  Note that P1 in FIG. 2 is a time when a short circuit occurs, P2 is a time when necking is detected, P3 is a time when a predetermined time T1 to be described later has elapsed from the occurrence of P2, and P4 is a time when an arc is generated. P9 or P13 is the time when the next short-circuit occurs, P6 or P10 or P14 is the time when necking detection occurs, P7 or P11 is the time when a predetermined time T1 to be described later has elapsed from the occurrence of P6 or P10, P8 or P12 or P15 Indicates the time when the arc occurred, IS1 is the short-circuit current value, IS2 is the return current value to the short-circuit current when the predetermined time T1 has elapsed from the occurrence of P2, and IN is the predetermined low current value that is reduced by detecting the constriction. It is shown.

  In FIG. 2, the short circuit period (for one short circuit period) from the P1 time point to the P4 time point will be described below.

  A short circuit occurs at the time P1, and the constriction detection unit 13 detects the constriction of the welding wire 18 that is a consumable electrode. When the constriction occurs at the time P2, the constriction detection unit 13 applies the constriction detection processing to the welding wire 18. The supplied current is reduced from the short-circuit current value IS1 at the time of detecting the squeezing to a predetermined low current value IN lower than that. The predetermined low current value IN may be a fixed value (for example, 50 A), or at least the wire diameter of the welding wire 18 to be fed, the wire type, the wire protrusion length, the shield gas to be supplied, and the set welding current. It may be a function obtained from one, or may be a function of the welding current at the time of detecting the constriction, for example, a value obtained by subtracting 50 A from the welding current IS1 when the constriction is detected. These fixed values, functions, etc. are obtained by experiments.

  The above-mentioned necking detection unit 13 detects a welding voltage differential value (a variation amount of the welding voltage per unit time) that is a differential value of the welding voltage applied between the welding wire 18 and the base material 21. Then, the detected welding voltage differential value is compared with a squeezing detection threshold value that is a predetermined reference voltage differential value that is a squeezing detection threshold value, and when the detected welding voltage differential value is greater than or equal to the reference voltage differential value, squeezing is detected. It is what I did. In addition, instead of the welding voltage differential value, the differential value of the resistance value (resistance value differential value) calculated by dividing the welding voltage by the welding current is detected, and the detected resistance value differential value and a threshold value for detecting the squeezing are predetermined. Necking may be detected when the detected resistance differential value is equal to or greater than the reference resistance differential value. The reference voltage differential value and the reference resistance differential value are obtained in advance by, for example, experiments.

  If the arc does not occur again from the point P2 at which the constriction is detected until the point P3 at which the predetermined period T1 has elapsed, the constriction misdetection detection unit 14 determines that the constriction is erroneously detected, and the short-circuit control unit 12 is used to determine the welding current ( Short-circuit current) is increased to a predetermined return current value IS2 described later. The short-circuit control unit 12 may instruct the drive unit 7 to increase the output current or may instruct the power to increase.

  Note that the above-described predetermined period T1 that is a criterion for erroneous detection of necking may be a fixed value (for example, 0.5 ms) obtained in an experiment, and a function of the welding current (when the necking is detected by the necking detection unit 13) ( (For example, if it is detected at 300 A, it may be set to 1 ms), or at least of the wire diameter of the welding wire 18 to be fed, the wire type, the wire protrusion length, the shield gas to be supplied, and the welding current set current region It may be a function obtained from one, and is the magnitude of the rate of change of the welding voltage over time (for example, if the welding voltage differential value dv / dt value at the time of detecting the constriction is 1 V / ms, set to 1 ms) Or the integrated value of the welding current of the current short circuit (for example, the integrated value of the welding current up to the point when the necking is detected is 300 A · s) , May be obtained from set to 1ms).

  Further, the predetermined return current value IS2 described above may be a fixed value (for example, 350 A), and the wire diameter of the welding wire 18 to be fed, the wire type, the wire protrusion length, the shield gas to be fed, and the set welding current ( A function obtained from at least one of (average welding current), or a function of the welding current when the constriction is detected, for example, a value obtained by adding 50 A to the welding current when the constriction is detected, or It is good also as a short circuit current value estimated that it reached | attained when the constriction detection process did not generate | occur | produce. These fixed values, functions, and the like are obtained in advance through experiments and the like.

  Here, the predetermined return current value IS2 needs to be set to a sufficient value so that the short circuit can be easily opened. Thereby, the transition from the short circuit to the arc is normally performed. As described above, even if the constriction detection at the time point P2 is a false detection, the current control at the time of normal short-circuiting is quickly restored after a predetermined period T1, so that adverse effects on welding stability and bead quality are minimized. Can be suppressed.

  In addition, when a constriction is erroneously detected before the time point P3, the constriction detection process is prohibited even if the constriction is detected in the period from the time point P3 to the time point P4. The prohibition of the squeezing detection process is to prevent the welding current from being reduced even when it is determined that squeezing has occurred in the squeezing detection hand portion 13.

  As described above, the constriction false detection occurs in a short circuit period, and the constriction false detection does not continuously occur in the short circuit period after the short circuit period in which the constriction false detection occurs, the arc welding method of the present embodiment is If a constriction detection error occurs during the short-circuit period, the constriction detection threshold (dv / dt) is increased by a predetermined value in order to lower the squeezing detection sensitivity, and further, a constriction detection error occurs during the subsequent short-circuit period Further, the constriction detection threshold value is further increased. Note that the increase in the squeezing detection threshold is obtained in advance, for example, through experiments.

  FIG. 2 shows that a constriction misdetection occurs in the short circuit period from the P1 time point to the P4 time point, the short circuit period from the P5 time point to the P8 time point, and the short circuit period from the P9 time point to the P12 time point. The waveforms of the welding current and the welding voltage when no squeezing erroneous detection has occurred during the short-circuiting period up to and including the change in the squeezing detection threshold during each short-circuiting period are shown.

  First, the squeezing detection threshold th2 (second threshold) is increased by a predetermined value from the squeezing detection threshold th1 (first threshold) due to erroneous detection of squeezing during the short circuit period from the P1 time to the P4 time.

  The necking detection threshold th3 (third threshold) is increased by a predetermined value from the necking detection threshold th2 (second threshold) due to erroneous detection of necking again during the subsequent short-circuit period from time P5 to time P8.

  The necking detection threshold th4 (fourth threshold) is increased by a predetermined value from the necking detection threshold th3 (third threshold) because the necking is erroneously detected again in the subsequent short-circuit period from time P9 to point P12.

  In the subsequent short-circuit period from time P13 to time P15, the constriction detection threshold th4 (fourth threshold) remains unchanged without increasing the constriction detection threshold th4 (fourth threshold) due to the fact that no constriction was detected. Continue as. Although not clearly shown in FIG. 2, when the constriction is erroneously detected again in the short-circuit period after P15, the constriction detection threshold is set to be larger than the constriction detection threshold th4 (fourth threshold).

  As described above, increasing the squeezing detection threshold decreases the squeezing detection sensitivity and makes it easier to increase the amount of spatter generated. However, arc instability due to false squeezing detection will not occur, and it is better to suppress arc instability. And the appearance of the bead can be improved.

  As described above, false detection of constriction can be prevented at an early stage, and problems such as arc instability, bead defects, increased spatter, poor penetration, etc. when false detection of constriction occurs can be minimized. It is possible to suppress adverse effects on the environment.

  In addition, when welding is performed from a welding start position to a welding end position in a certain welding line and welding is performed on the next welding line, the welding is performed after returning the squeezing detection threshold value to the squeezing detection threshold value th1 that is the reference squeezing detection threshold value. It may be started.

(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 the squeezing detection threshold is increased when the number of short-circuiting periods in which squeezing is erroneously detected reaches a predetermined number of times.

  FIG. 3 also shows time-dependent changes in the welding current waveform, welding voltage waveform, and squeezing detection threshold in consumable electrode arc welding in which short-circuiting and arc are alternately repeated, as in FIG.

  FIG. 3 shows an example in which the squeezing detection sensitivity is increased by a predetermined value when the short circuit period in which squeezing is erroneously detected is a predetermined number of times. The predetermined number of times is set by a constriction error detection number setting unit (not shown).

  FIG. 3 shows that a constriction error is detected in the short circuit period from the P1 time point to the P4 time point, the short circuit period from the P5 time point to the P8 time point, and the short circuit period from the P9 time point to the P12 time point. The waveforms of the welding current and the welding voltage when no squeezing erroneous detection has occurred during the short-circuiting period up to and including the change in the squeezing detection threshold during each short-circuiting period are shown.

  First, although not shown, the constriction is falsely detected in the short-circuit period before the time P1, and the number of short-circuit periods in which the constriction is falsely detected is counted as one, and then the short-circuit from the time P1 to the time P4. The constriction detection threshold is changed from the constriction detection threshold th1 to the constriction detection threshold th1 because the short-circuit period in which the constriction is erroneously detected in the period becomes the predetermined number of times set by the false constriction detection number setting unit. Raise to th3.

  Thereafter, since the squeezing error is detected again in the short-circuit period from the time point P5 to the time point P8, the squeezing error detection count is counted as one by a not-shown counting unit, but the squeezing detection threshold value is not changed and the squeezing detection threshold value th3 is continued. .

  After that, since the constriction error was detected in the short-circuit period from the time point P9 to the time point P12, the number of constriction detection errors was counted twice, and the predetermined number of constrictions was detected. Therefore, the constriction detection threshold value was changed from the constriction detection threshold value th3 to the constriction detection threshold value th5. Raise to.

  Thereafter, since the constriction was not erroneously detected in the short circuit period from the time point P13 to the time point P15, the constriction detection threshold th5 is not increased and the constriction detection threshold th5 is continued.

  Then, in the case of continuously detecting false detection of the constriction, the control as described above is performed to increase the constriction detection threshold and decrease the constriction detection sensitivity.

  In the present embodiment, the configuration of the arc welding apparatus is the same as that described in the first embodiment.

  As described above, according to the present embodiment, similarly to the first embodiment, false detection of necking is prevented at an early stage, and arc instability, bead defects, increased spatter, and poor penetration at the time of erroneous necking detection occur. It is possible to minimize problems such as these, and to suppress adverse effects on production efficiency and the work environment.

  A constriction error detection number setting unit (not shown) and a count unit (not shown) are provided in the short-circuit control unit 12. In addition, this count unit is provided with a register, and counts the number of short-circuit periods in which the constriction is erroneously detected based on the output from the constriction erroneous detection detection unit 14. When the count reaches the predetermined number set by the constriction error detection number setting unit, the fact that the predetermined number has been reached is output to the constriction detection threshold value control unit 15 and the contents of the register are reset. .

  Note that the number of short-circuit periods in which the constriction is erroneously detected may be counted by the constriction detection threshold value control unit 15.

(Embodiment 3)
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 difference from the first embodiment is that, with respect to the steady welding period TN after the arc start period TS, the increase in the squeezing detection threshold when a squeezing error is detected in the arc start period TS, the squeezing detection threshold value in the steady welding period TN. It is a point larger than the raising width.

  FIG. 4 shows an example of the change over time of the welding current waveform in consumable electrode arc welding in which a short circuit and an arc are alternately repeated.

  In the arc start period TS from the welding start point PS to the welding point PN, which is an intermediate point during welding, the increase in the squeezing detection sensitivity due to erroneous detection of the squeezing is made larger than the steady welding period TN after the welding point PN. It is. It should be noted that the increase width of the squeezing detection sensitivity at this time is obtained in advance by experiments or the like, for example, and may be, for example, twice the increase width of the squeezing detection sensitivity during steady welding.

  In the arc start period TS, unlike the arc state in the steady welding period TN, the formation of the molten pool on the base material 21 is not completed completely, the short-circuit state is difficult to stabilize, and the short-circuit cycle tends to be irregular.

  Therefore, since the constriction erroneous detection is likely to occur, when the constriction is erroneously detected, the increase in the constriction detection threshold is increased in order to prevent the constriction erroneous detection from occurring at an early stage.

  FIG. 5 is a diagram showing a schematic configuration of the arc welding apparatus in the present embodiment, which is configured as follows.

  The difference from FIG. 2 showing the schematic configuration of the arc welding apparatus in the first and second embodiments is that an arc start period output unit 22 that outputs a signal that causes the constriction detection threshold value control unit 15 to recognize that it is the arc start period TS. This is the point.

  Upon receiving a signal from the arc start period output unit 22 that the arc start period TS is in progress, the squeezing detection threshold value control unit 15 determines the increase in the squeezing detection threshold value in the arc start period TS during the steady welding period TN. Make it larger than the amount of increase. For example, the arc start period TS may be increased by about twice the increase during the steady welding period TN.

  FIG. 6 shows changes over time in the welding current waveform, welding voltage waveform, and squeezing detection threshold in consumable electrode arc welding in which the short circuit and the arc are alternately repeated in the present embodiment.

  In the steady welding period TN, the squeezing detection threshold th is increased from the squeezing detection threshold th3 to the squeezing detection threshold th4, and from the squeezing detection threshold th4 to the squeezing detection threshold th5. In the arc start period TS, the increase amount is increased. The squeezing detection threshold th1 that is twice that of the steady welding period TN increases from the squeezing detection threshold th3.

  As described above, according to the present embodiment, constriction false detection is prevented at an earlier stage than in the first embodiment, and arc instability, bead defects, increased spatter, poor penetration, etc. when constriction misdetection occurs. Problems can be minimized and adverse effects on production efficiency and work environment can be suppressed.

  In FIG. 6, the squeezing detection threshold th is increased up to the squeezing detection threshold th3 during the arc start period TS, but the squeezing detection threshold th is used as the reference squeezing detection when the arc start period TS reaches the steady welding period TN. The threshold value may be lowered to the detection threshold value th1 and then the squeezing detection threshold value may be raised when squeezing detection occurs.

  The consumable electrode arc welding method of the present invention prevents constriction misdetection, and suppresses problems such as arc instability, bead defects, increased spatter, poor penetration, etc. even when constriction misdetection occurs. The adverse effect on the working environment can be suppressed, and the present invention is industrially useful as a welding apparatus and a welding method for performing welding with a short circuit.

The figure which shows schematic structure of the arc welding apparatus in Embodiment 1 of this invention. (A) The figure which shows the welding current waveform in Embodiment 1, (b) The figure which shows the welding voltage waveform in Embodiment 1, (c) The figure which shows the squeezing detection threshold value in Embodiment 1. (A) The figure which shows the welding current waveform in Embodiment 2, (b) The figure which shows the welding voltage waveform in Embodiment 2, (c) The figure which shows the squeezing detection threshold value in Embodiment 2. The figure which shows the arc start period and steady welding period in Embodiment 3 of this invention The figure which shows schematic structure of the arc welding apparatus in Embodiment 3 of this invention. (A) The figure which shows the welding current waveform in Embodiment 3, (b) The figure which shows the welding voltage waveform in Embodiment 3, (c) The figure which shows the squeezing detection threshold value in Embodiment 3. Diagram showing welding current waveform in conventional arc welding

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input power supply 2 Primary rectification part 3 Switching element 4 Transformer 5 Secondary rectification part 6 DCL (inductor)
DESCRIPTION OF SYMBOLS 7 Drive part 8 Welding voltage detection part 9 Welding current detection part 10 Short circuit / arc detection part 11 Arc control part 12 Short circuit control part 13 Constriction detection part 14 Constriction false detection detection part 15 Constriction detection threshold value control part 16 Constriction detection reference threshold value setting part 17 Welding wire feeding device 18 Welding wire 19 Tip 20 Welding arc 21 Base material 22 Arc start period output part P1, P5, P9, P13 Short-circuit occurrence time P2, P6, P10, P14 Neck detection time P3, P7, P11 Constriction error Detection time P4, P8, P12, P15 Arc generation time T1 Predetermined time IS1 Short-circuit current value IS2 Return current value IN Low current value TN Steady welding period TS Arc start period PS Welding start point PN Welding point

Claims (8)

In arc welding in which a welding wire, which is a consumable electrode, is fed to the base material to alternately generate a short circuit period and an arc period,
Detecting the constriction of the welding wire that occurs at the end of the short circuit period;
An arc welding method for determining that the constriction is erroneously detected when no arc occurs within a predetermined period after detecting the constriction,
Constriction is detected based on the first constriction detection threshold in the first short-circuit period,
If the neck is erroneously detected during the first short-circuit period, the neck detection threshold is raised to a second neck detection threshold that is greater than the first neck detection threshold;
Detecting a constriction based on the second constriction detection threshold in a second short circuit period after the first short circuit period;
If the necking is erroneously detected during the second short-circuit period, the necking detection threshold is raised to a third necking detection threshold that is larger than the second necking detection threshold, and the necking is not erroneously detected during the second short-circuiting period. In some cases, the arc welding method maintains the second detection threshold. In arc welding in which a welding wire, which is a consumable electrode, is fed to the base material to alternately generate a short circuit period and an arc period,
Detecting the constriction of the welding wire that occurs at the end of the short circuit period;
An arc welding method for determining that the constriction is erroneously detected when no arc occurs within a predetermined period after detecting the constriction,
Constriction is detected based on the first squeezing detection threshold during the short circuit period,
When the number of short-circuit periods in which the constriction is erroneously detected reaches a predetermined number, the constriction detection threshold is raised to a second constriction detection threshold that is larger than the first constriction detection threshold,
In the short-circuit period after the short-circuit period when the squeezing detection threshold is raised to the second detection threshold, the squeezing is detected based on the second squeezing detection threshold;
When the number of short-circuit periods in which the constriction is erroneously detected in the short-circuit period after the short-circuit period in which the constriction detection threshold is raised to the second detection threshold becomes a predetermined number, the constriction detection threshold is set to the second constriction detection threshold. An arc welding method in which the second squeezing detection threshold is maintained until the number of short-circuiting periods in which squeezing is erroneously detected reaches the predetermined number of times. An arc welding method in which a steady welding period is provided after an arc start period, and a raising range for raising a squeezing detection threshold is larger in a raising range in the arc starting period than in a short circuit period in the steady welding period. Or the arc welding method of 2. The arc welding method according to any one of claims 1 to 3, wherein when the squeezing detection threshold is raised during the short-circuit period, the squeezing detection threshold is raised when the squeezing is erroneously detected. 5. The arc welding according to claim 1, wherein the squeezing detection threshold value is a change amount per unit time of the welding voltage or a change amount per unit time of a value obtained by dividing the welding voltage by the welding current. Method. The arc welding method according to any one of claims 1 to 5, wherein, during a short-circuit period determined to be erroneous detection of necking, detection of the necking is prohibited until an arc is generated after determination of erroneous detection of necking. An arc welding apparatus that performs welding by repeatedly generating and short-circuiting an arc between a welding wire that is a consumable electrode and a base material,
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;
A squeezing detection reference threshold setting unit for outputting a squeezing detection reference threshold for squeezing detection during a short circuit period;
In the short-circuit control unit,
A squeezing detection unit for detecting a squeezing of the welding wire that occurs at the end of a short circuit period based on the welding voltage detection unit and / or the output of the welding current detection and the squeezing detection reference threshold value setting unit;
A constriction detection detection unit that determines that the constriction is erroneously detected when no arc occurs within a predetermined period after detecting the constriction in the constriction detection unit;
A constriction detection threshold value control unit that outputs to the constriction detection unit that a constriction detection threshold value is larger than the constriction detection reference threshold value when the constriction is erroneously detected;
In the first short-circuit period, the squeezing is detected based on the first squeezing detection threshold that is the squeezing detection reference threshold.
If the neck is erroneously detected during the first short-circuit period, the neck detection threshold is raised to a second neck detection threshold that is greater than the first neck detection threshold;
Detecting a constriction based on the second constriction detection threshold in a second short circuit period after the first short circuit period;
If the necking is erroneously detected during the second short-circuit period, the necking detection threshold is raised to a third necking detection threshold that is larger than the second necking detection threshold, and the necking is not erroneously detected during the second short-circuiting period. In some cases, the arc welding apparatus maintains the second detection threshold. An arc welding apparatus that performs welding by repeatedly generating and short-circuiting an arc between a welding wire that is a consumable electrode and a base material,
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;
A squeezing detection reference threshold setting unit for outputting a squeezing detection reference threshold for squeezing detection during a short circuit period;
In the short-circuit control unit,
A squeezing detector that detects a squeezing of the welding wire that occurs at the end of a short circuit period based on the welding voltage detector and / or the output of the welding current detection and the squeezing detection reference threshold value setting unit;
A constriction detection detection unit that determines that the constriction is erroneously detected when no arc occurs within a predetermined period after detecting the constriction in the constriction detection unit;
A counting unit that counts the number of short-circuit periods in which the constriction is erroneously detected based on the output of the constriction erroneous detection detection unit;
Constriction error detection number setting section for setting the number of constriction false detection,
Constriction for outputting to the constriction detection unit that the constriction detection threshold is larger than the constriction detection reference threshold when the number of short circuits counted by the counting unit reaches the number set in the constriction error detection number setting unit A detection threshold value control unit,
When the number of short-circuit periods in which the constriction is erroneously detected reaches a predetermined number, the constriction detection threshold is raised to a second constriction detection threshold that is larger than the first constriction detection threshold that is the constriction detection reference threshold,
In the short-circuit period after the short-circuit period when the squeezing detection threshold is raised to the second detection threshold, the squeezing is detected based on the second squeezing detection threshold;
When the number of short-circuit periods in which the constriction is erroneously detected in the short-circuit period after the short-circuit period in which the constriction detection threshold is raised to the second detection threshold becomes a predetermined number, the constriction detection threshold is set to the second constriction detection threshold. An arc welding apparatus that raises the second squeezing detection threshold to a larger third squeezing detection threshold and maintains the second squeezing detection threshold until the number of short-circuit periods in which squeezing is erroneously detected reaches the predetermined number of times.

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