JP4620519B2 - Consumable electrode arc welding end control method - Google Patents

Description

  The present invention relates to a consumable electrode arc welding end control method for suppressing spatter generation during a welding end control period in consumable electrode arc welding.

  FIG. 5 is a diagram showing current / voltage waveforms and droplet transfer in consumable electrode arc welding in which the short-circuit period Ts and the arc period Ta are repeated. FIG. 4A shows the change over time in the welding current Iw for energizing the consumable electrode (hereinafter referred to as welding wire 1), and FIG. 4B shows the time of the welding voltage Vw applied between the welding wire 1 and the base material 2. FIG. FIGS. 3C to 3E show the transition of the droplet 1a. Hereinafter, a description will be given with reference to FIG.

  During the short-circuit period Ts from time t1 to t3, the droplet 1a at the tip of the welding wire 1 is short-circuited with the base material 2, and as shown in FIG. As shown in B), since the welding voltage Vw is in a short circuit state, the welding voltage Vw becomes a low value of about several volts. As shown in FIG. 5C, the droplet 1a comes into contact with the base material 2 at a time t1 to enter a short circuit state. Thereafter, as shown in FIG. 4D, a constriction 1b is generated at the upper part of the droplet 1a by an electromagnetic pinch force generated by a welding current Iw for energizing the droplet 1a. And this constriction 1b advances rapidly, and as shown to the same figure (E) at the time t3, the droplet 1a transfers from the welding wire 1 to the molten pool 2a, and the arc 3 regenerates.

  When the above-mentioned constriction phenomenon occurs, the short circuit is released after a very short time of about several hundred μs, and the arc 3 is regenerated. That is, this constriction phenomenon is a precursor phenomenon of short circuit cancellation. When the constriction 1b occurs, the conduction path of the welding current Iw becomes narrow at the constricted portion, and the resistance value of the constricted portion increases. The increase in the resistance value increases as the constriction progresses and the constricted portion becomes narrower. Therefore, the occurrence and progress of the constriction phenomenon can be detected by detecting the change in resistance value between the welding wire 1 and the base material 2 during the short-circuit period Ts. This change in resistance value can be calculated by (welding voltage Vw) / (welding current Iw). Further, as described above, since the constriction occurrence time is extremely short, the change in the welding current Iw during this period is small as shown in FIG. For this reason, the occurrence of the constriction phenomenon can be detected by the change of the welding voltage Vw instead of the change of the resistance value. As a specific necking detection method, a change rate (differential value) of the resistance value or the welding voltage value Vw during the short-circuit period Ts is calculated, and the necking detection is performed when the rate of change reaches a predetermined necking detection reference value. There is a way to do. As another method, as shown in FIG. 5B, a voltage increase value ΔV from a stable short-circuit voltage value Vs before occurrence of constriction during the short-circuit period Ts is calculated, and this voltage increase value ΔV is calculated at time t2. There is a method of detecting the squeezing when the squeezing reaches a predetermined squeezing detection reference value Vtn. In the following description, a case in which the squeezing detection method is based on the above-described voltage increase value ΔV will be described, but other methods that have been proposed in the past may be used. Detection of arc reoccurrence at time t3 can be easily performed by determining that the welding voltage Vw has become equal to or greater than the short circuit / arc determination value Vta. Incidentally, the period of Vw <Vta is the short circuit period Ts, and the period of Vw ≧ Vta is the arc period Ta. When the arc is regenerated at time t3, the welding current Iw increases rapidly as shown in FIG. 6A, and then decreases gradually. As shown in FIG. 5B, the welding voltage Vw is about several tens of volts. Arc voltage value. During the arc period Ta from time t3 to t4, the tip of the welding wire 1 is melted to form a droplet 1a. Thereafter, the operation in the period from time t1 to t4 is repeated.

  In the welding with the short circuit described above, when the arc regeneration current value ia when the arc 3 is regenerated at time t3 is a large current value, the arc force from the arc 3 to the molten pool 2a increases sharply. A large amount of spatter is generated. That is, the amount of spatter generated increases substantially in proportion to the current value Ia at the time of arc re-generation. Therefore, in order to suppress the occurrence of sputtering, it is necessary to reduce the current value Ia at the time of arc re-occurrence. As a method for this, various welding power sources have been proposed in which a constriction detection control method is added to detect the occurrence of the above-mentioned constriction phenomenon, to rapidly reduce the welding current Iw and to reduce the current value Ia at the time of arc reoccurrence. . Hereinafter, this prior art will be described.

  FIG. 6 is a block diagram of a welding power source employing a squeezing detection control method of the prior art. The power source main circuit PM receives a commercial power source such as a three-phase 200V as an input, performs output control such as inverter control and chopper control according to a drive signal Dr described later, and outputs a welding voltage Vw and a welding current Iw suitable for arc welding. . The transistor TR is inserted in series with the output, and a resistor R is connected in parallel therewith. The squeezing detection control circuit ND outputs a squeezing detection signal Nd that is at a high level when the welding voltage Vw is input to detect the occurrence of squeezing of the droplet during the short-circuiting period by increasing the voltage. The transistor drive circuit DRT outputs a transistor drive signal Drt that turns on the transistor TR when the squeezing detection signal Nd is at a low level (when non-necking is detected). Therefore, the transistor TR is turned off when the squeezing detection signal Nd is at a high level (when squeezing is detected). The welding wire 1 is fed at a feeding speed Wf [m / min] by a feeding motor M, and an arc 3 is generated between the welding wire 1 and the base material 2.

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the welding voltage Vw at the normal time. The anti-stic voltage setting circuit VAR outputs a predetermined anti-stic voltage setting signal Var for controlling the welding voltage Vw during the anti-stic control period. The switching circuit SW receives the welding start signal St from the outside and switches to the a side when it changes to the High level (steady state) and outputs the voltage setting signal Vr as the voltage control setting signal Vcr. The above-described anti-stic voltage setting signal Var is output as the voltage control setting signal Vcr.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The error amplification circuit EA amplifies an error between the voltage control setting signal Vcr and the voltage detection signal Vd, and outputs an error amplification signal Ea. With this circuit, the consumable electrode arc welding power source has constant voltage characteristics. The start-up circuit ON outputs the start-up signal On that changes to the high level when the welding start signal St changes to the high level, and changes to the low level after being delayed by a predetermined antistic period Tan when the start signal St changes to the low level. . The drive circuit DR receives the activation signal On and outputs the drive signal Dr according to the error amplification signal Ea during the high level. The feed control circuit FC outputs a feed control signal Fc for controlling the feed motor M at a rotational speed corresponding to a predetermined feed speed while the welding start signal St is at a high level.

FIG. 7 is a timing chart of each signal of the welding power source. FIG. 4A shows the welding current Iw, FIG. 2B shows the welding voltage Vw, FIG. 3C shows the squeezing detection signal Nd, and FIG. 4D shows the time change of the transistor drive signal Drt. The figure is a timing chart in a steady state. Hereinafter, a description will be given with reference to FIG.

  In the figure, during the period other than the squeezing detection period from time t2 to t3, the squeezing detection signal Nd is at the low level as shown in FIG. 10C, so that the transistor drive is performed as shown in FIG. The signal Drt becomes High level. As a result, since the transistor TR is turned on, the operation is the same as that of a normal welding power source for consumable electrode arc welding.

  At time t2, as shown in FIG. 5B, it is detected that the welding voltage Vw has increased during the short-circuit period Ts and the voltage increase value ΔV has become equal to or greater than a predetermined squeezing detection reference value Vtn. If it is determined that constriction has occurred, the constriction detection signal Nd becomes High level as shown in FIG. In response to this, as shown in FIG. 4D, the transistor drive signal Drt is at the low level, so that the transistor TR is turned off. As a result, the resistor R is inserted into the energization path of the welding current Iw. Since the value of this resistor R is set to a value that is at least 10 times larger than the short-circuit load (several tens of mΩ), it is accumulated in the DC reactor in the welding power source and the cable reactor as shown in FIG. As a result, the welding current Iw decreases rapidly. When the short circuit is released and the arc is regenerated at time t3, the welding voltage Vw becomes equal to or higher than a predetermined short circuit / arc discrimination value Vta as shown in FIG. When this is detected, the squeezing detection signal Nd becomes a low level as shown in FIG. 5C, and the transistor drive signal Drt becomes a high level as shown in FIG. As a result, the transistor TR is turned on, and normal consumable electrode arc welding is controlled. By this operation, the arc regeneration current value Ia at the time of arc regeneration (time t3) can be reduced, and the occurrence of sputtering can be suppressed. (See Patent Document 1)

  FIG. 8 is a timing chart during the welding end control of the welding power source described above with reference to FIG. FIG. 4A shows the welding start signal St, FIG. 3B shows the start signal On, FIG. 3C shows the feed speed Wf, and FIG. 4D shows the voltage control setting signal Vcr. (E) shows the time variation of the welding voltage Vw, and FIG. (F) shows the time change of the welding current Iw. Hereinafter, a description will be given with reference to FIG.

  At time t1, when the welding start signal St changes to a low level (end command) as shown in FIG. 5A, the activation signal On is in the anti-stic period until time t3 as shown in FIG. It changes to Low level after Tan delay. In response to the change in the welding start signal St at time t1, the feed control signal Fc to the feed motor M is changed to a stop command as shown in FIG. It gradually slows down over about 10 ms, and the feeding stops at time t2. When the feed motor M is a servo motor, the rate of reduction of the feed speed after the stop command is also controlled. In addition, a brake circuit is added to the motor drive unit to shorten the deceleration period. As shown in FIG. 4D, the voltage control setting signal Vcr drops to a value determined by the anti-stic voltage setting signal Van at time t2.

  During the anti-stic period Tan, the anti-stic voltage setting signal Var is a low value, as shown in FIG. Then, at time t2, as shown in FIG. 5C, the feeding speed Wf becomes zero and the feeding by inertia stops, and the wire burnup height can maintain the arc before and after this time. When the value Vh is reached, the arc disappears. When the arc disappears, the welding voltage Vw becomes a high value no-load voltage. At time t3, as shown in FIG. 5B, the start signal On changes to the low level, and the output of the welding power source stops. The limit voltage value Vh is substantially proportional to the value of the anti-stick voltage setting signal Var. Therefore, the anti-stick voltage setting signal Var may be adjusted to set the wire burn-up height to a desired value.

  The above is an antistic control method in which a predetermined antistic voltage is applied during a predetermined antistic period Tan. In addition to this, the following methods are conventionally used. First, in the second anti-stick control method, the limit voltage value Vh is set, and the output of the welding power source is stopped when the welding voltage value Vw during the anti-stick period Tan reaches this set value (t2). In this method, the limit voltage value Vh that determines the wire burnup height can be set directly. In addition, the wasteful no-load voltage application period at times t2 to t3 can be omitted. Next, in the third anti-stic control method, a welding current Iw having a low value of about several tens of A is applied for a predetermined period from the release of the short circuit during the anti-stic period Tan, thereby adjusting the amount of wire melt and The height is set to a desired value. This method is often applied to a welding power source having a constant current characteristic such as consumable electrode pulse arc welding. As described above, there are various anti-stick control methods for setting the wire burn-up height to a desired value. (See Patent Documents 1 and 2)

JP 59-206159 A Japanese Patent Laid-Open No. 62-176680 JP-A-9-267171

  The problem will be described with reference to FIG. 8 described above. In the steady state before entering the anti-stic period Tan, as shown at time ta, since the current value is low when the short circuit is released by the constriction detection control and the arc is regenerated, the occurrence of spatter is suppressed. Is done. However, the current value at the time of the occurrence of the short-circuit release arc during the anti-stick period Tan (time tb, tc) remains very large. The reason for this is as follows. That is, during the anti-stic period Tan, as shown in FIG. 5C, the feeding speed Wf changes so as to become gradually slower, so that it becomes difficult to adjust the squeezing detection sensitivity. For this reason, the constriction detection is often erroneously detected, and the arc state is often made unstable. In order to cope with this, it has been common to prohibit the squeezing detection control from being performed during the anti-stick period Tan. As a result, when a short circuit occurs during the anti-stic period Tan, the current value at the time of arc reoccurrence increases, and there is a problem that the generation of spatter cannot be suppressed.

  Therefore, the present invention provides a consumable electrode arc welding end control method capable of suppressing the occurrence of spatter by constriction detection control even during welding end control.

In order to solve the above-described problems, the first invention outputs a stop command to the feed motor when a welding end command is input to the welding power source, and the wire burnup height when the welding wire stops is substantially equal. In the consumable electrode arc welding end control method for anti-stick control of the output of the welding power source so as to have a desired value,
The first short-circuit occurrence after the welding end command is input is detected and the stop command is output to the feed motor, and then the welding current is rapidly reduced by detecting the constriction phenomenon of the droplet during the short-circuit period. The arc is regenerated by maintaining it at a low value, and when the arc is regenerated in a state where the arc length is substantially constant, the anti-stick control is performed to set the wire burnup height to a desired value. This is a consumable electrode arc welding end control method.

  According to a second aspect of the present invention, there is provided a consumable electrode arc welding end control method characterized in that a timing at which a stop command is output to the feed motor according to the first aspect of the invention is the arc re-generation time.

  According to the present invention, it is possible to perform control for detecting squeezing with high accuracy even for a short circuit during welding end control, so that it is possible to significantly suppress the occurrence of spatter during the welding end control period. In addition, since the short-circuit that occurred first during the welding end control period is canceled and the arc is re-generated, the arc state is stable and constant, so a short-circuit can occur again during the subsequent anti-stick control. The nature becomes low. For this reason, generation | occurrence | production of the sputter | spatter by a re-short circuit can be suppressed, and the variation in wire burnup height can also be reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
The first embodiment of the present invention detects the first occurrence of a short circuit after a welding end command is input, outputs a stop command to the feed motor, and subsequently detects a droplet constriction phenomenon during this short circuit period. Then, the welding current is rapidly reduced and maintained at a low value, and the arc is regenerated. When the arc is regenerated with the arc length being low, the antistick control is performed and the wire burnup height is reduced to the desired value. This is an electrode arc welding end control method. Hereinafter, the first embodiment will be described in detail.

  FIG. 1 is a block diagram of a welding power source for carrying out the consumable electrode arc welding end control method according to Embodiment 1 of the present invention. In the figure, the same blocks as those in FIG. 6 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from those in FIG. 6 will be described.

  The short circuit detection circuit SD detects a short circuit state based on the value of the voltage detection signal Vd, and outputs a short circuit detection signal Sd that becomes High level. The anti-stick control switching circuit AC receives the short circuit detection signal Sd and the welding start signal St, and the short circuit detection signal Sd is first set to the High level after the welding start signal St changes from the High level to the Low level (welding end command). At the time of changing to (short circuit), an anti-stick control switching signal Ac that changes to High level is output. In the figure, the above-mentioned anti-stick control switching signal Ac is used as an input signal for synchronization to the start-up circuit ON, the switching circuit SW, and the feed control circuit FC.

  FIG. 2 is a timing chart during welding end control in the above-described welding power source. FIG. 4A shows the welding start signal St, FIG. 3B shows the start signal On, FIG. 3C shows the feed speed Wf, and FIG. 4D shows the voltage control setting signal Vcr. (E) shows the welding voltage Vw, (F) shows the welding current Iw, (G) shows the short circuit detection signal Sd, and (H) shows the time change of the anti-stick control switching signal Ac. This figure corresponds to FIG. 8 described above. Hereinafter, a description will be given with reference to FIG.

  At time t1, the welding start signal St changes to the low level (welding end command) as shown in FIG. 5A, but the anti-stick control switching signal Ac is at the low level as shown in FIG. It remains unchanged. For this reason, the feeding speed Wf shown in FIG. 6C and the voltage control setting signal Vcr shown in FIG. When the first short circuit after time t1 occurs at time t2 as shown in (E) of the figure, the short circuit detection signal Sd changes to High level and responds to this as shown in (G) of the figure. As shown in FIG. 5H, the anti-stick control switching signal Ac changes to the high level. In response to this, as shown in FIG. 4B, the activation signal On is delayed by a predetermined anti-stic period Tan from time t2 and changes to the low level at time t4. At the same time, as shown in FIG. 5C, a stop command is output to the feed motor M by the feed control signal Fc, and the feed speed Wf is gradually decreased due to inertia. At the same time, as shown in FIG. 4D, the voltage control setting signal Vcr changes to the anti-stick voltage setting value Var.

  During the short-circuit period occurring at time t2, as described above, the feed speed Wf remains substantially steady, so that the constriction detection can be performed with high accuracy as in the steady state. For this reason, as shown in FIG. 5F, the current value at the time of arc re-occurrence at time tb can be lowered, and the occurrence of spatter during the welding end control period after time t1 can be suppressed. Furthermore, the arc length at the time of arc re-occurrence at time tb is substantially constant at first because the arc force is weak because almost all of the droplets on the wire tip are smoothly transferred by the constriction detection control and the current value is low. It becomes a low state. That is, the arc length when the arc is regenerated does not vary greatly depending on the welding conditions, and is a substantially constant low value. Since the anti-stick control is performed from a state in which the arc length is substantially constant, as shown in FIG. 5C, before and after the feeding speed Wf becomes substantially zero at time t3, as shown in FIG. In addition, the wire burn-up height reaches a substantially desired value and the arc disappears. When the anti-stic period Tan ends at time t4, as shown in FIG. 5B, the start signal On changes to the low level, and the output of the welding power source stops.

  In the first embodiment described above, since the squeezing detection control can be performed with high accuracy even for a short circuit during the welding end control period, the occurrence of spatter during the welding end control period can be significantly suppressed. In addition, the arc state when the short circuit that occurred first in the welding end control period is canceled and the arc is regenerated is a stable and constant state, so that a short circuit can occur again during the subsequent anti-stic period. The nature becomes low. For this reason, the possibility of occurrence of spatter due to re-short-circuiting is reduced, and variations in the wire burn-up height are reduced.

[Embodiment 2]
The second embodiment of the present invention switches the anti-stick control described in the first embodiment and outputs a stop command to the feed motor. The first short circuit that occurs after the welding end command is input is released. This is the time when the arc is regenerated. In the following, the second embodiment will be described differently from the first embodiment.

  FIG. 3 is a block diagram of a welding power source for carrying out the consumable electrode arc welding end control method according to Embodiment 2 of the present invention. In the figure, the same blocks as those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, blocks indicated by dotted lines different from those in FIG. 1 will be described.

  The second anti-stick control switching circuit AC2 receives the short circuit detection signal Sd and the welding start signal St, and after the welding start signal St changes from the High level to the Low level (welding end command), the short circuit detection signal Sd is first High. The anti-stick control switching signal Ac that changes to the high level is output when the level (short circuit) is reached and the level changes again to the low level (arc reoccurrence). As a result, the timing at which the anti-stick control switching signal Ac changes to the high level is shifted from the time when the first short circuit occurs in the first embodiment to the time when the short circuit release arc is regenerated.

  FIG. 4 is a timing chart at the time of welding end control in the above-described welding power source. FIG. 4A shows the welding start signal St, FIG. 3B shows the start signal On, FIG. 3C shows the feed speed Wf, and FIG. 4D shows the voltage control setting signal Vcr. (E) shows the welding voltage Vw, (F) shows the welding current Iw, (G) shows the short circuit detection signal Sd, and (H) shows the time change of the anti-stick control switching signal Ac. This figure corresponds to FIG. 2 described above, and the points different from FIG. 2 will be described below.

  At time t2, when the short circuit detection signal Sd changes to the low level as shown in FIG. 5G, the anti-stick control switching signal Ac changes to the high level as shown in FIG. In response to this, the control is switched to the anti-stick control, and the start signal On becomes the low level after the anti-stick period Tan has elapsed as shown in FIG. 5B, and as shown in FIG. A stop command is output and the feed speed Wf is gradually decreased due to inertia. At the same time, as shown in FIG. 4D, the voltage control setting signal Vcr changes from the voltage setting value Vr in the steady state to the anti-stick voltage setting value Var. The other operations are the same as those in FIG. Therefore, in the second embodiment, the timing at which the anti-stick control switching signal Ac becomes the high level is shifted from the first short-circuit occurrence to the release. The operational effects of the second embodiment are the same as those of the first embodiment.

  In the above-described first and second embodiments, a method of applying an anti-stic voltage for a predetermined period is illustrated as an anti-stick control method. However, as the anti-stick control method in the present invention, as described above in the section of the prior art, a method of stopping output when the welding voltage during the anti-stic period reaches a predetermined value, and applying a predetermined current for a predetermined period. Various conventional techniques such as methods may be used.

It is a block diagram of the welding power supply for implementing the consumable electrode arc welding completion | finish control method which concerns on Embodiment 1 of this invention. It is a timing chart at the time of the welding end control in the welding power supply of FIG. It is a block diagram of the welding power source for implementing the consumable electrode arc welding completion | finish control method which concerns on Embodiment 2 of this invention. It is a timing chart at the time of the welding end control in the welding power supply of FIG. It is a current and voltage waveform diagram of consumable electrode arc welding in the prior art. It is a block diagram of the welding power supply for implementing the consumable electrode arc welding completion | finish control method in a prior art. It is a timing chart at the time of the steady state in the welding power supply of FIG. It is a timing chart at the time of the welding end control in the welding power supply of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 1a Droplet 1b Constriction 2 Base material 2a Weld pool 3 Arc AC Antistic control switching circuit Ac Antistic control switching signal AC2 2nd antistic control switching circuit DR Drive circuit Dr Drive signal DRT Transistor drive circuit Drt Transistor drive signal EA Error amplification circuit Ea Error amplification signal FC Feed control circuit Fc Feed control signal Ia Arc regeneration current value Iw Welding current M Feed motor ND Constriction detection control circuit Nd Constriction detection signal ON Start circuit On Start signal PM Main power Circuit R Resistor SD Short-circuit detection circuit Sd Short-circuit detection signal St Welding start signal SW Switching circuit Tan Anti-stic period TR Transistor Ts Short-circuit period VAR Anti-stic voltage setting circuit Var Anti-stic voltage setting (value / signal)
Vcr Voltage control setting signal VD Voltage detection circuit Vd Voltage detection signal Vh Limit voltage value VR Voltage setting circuit Vr Voltage setting (value / signal)
Vs Short-circuit voltage value Vta Short-circuit / arc discrimination value Vtn Necking detection reference value Vw Welding voltage Wf Feeding speed ΔV Voltage increase value

Claims (2)

When a welding end command is input to the welding power source, a stop command is output to the feed motor, and the output of the welding power source is controlled in an anti-stick manner so that the wire burn-up height when the welding wire stops is approximately the desired value. In the consumable electrode arc welding end control method,
The first short-circuit occurrence after the welding end command is input is detected and the stop command is output to the feed motor, and then the welding current is rapidly reduced by detecting the constriction phenomenon of the droplet during the short-circuit period. The arc is regenerated by maintaining it at a low value, and when the arc is regenerated in a state where the arc length is substantially constant, the anti-stick control is performed to set the wire burnup height to a desired value. Consumable electrode arc welding end control method. 2. A consumable electrode arc welding end control method, characterized in that a timing at which a stop command is output to the feeding motor according to claim 1 is the arc re-generation time.

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