JP2013094792A - Current control method in detecting constriction in consumable electrode arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a satisfactory welding quality even when welding speed is changed in ark welding in which a constriction of droplet is detected to control welding current.SOLUTION: The current control method in detecting a constriction in consumable electrode arc welding includes: detecting a constriction of droplet that is a premonitory phenomenon of regenerating an arc from a short circuit condition; reducing, upon detection of the constriction, the welding current to be carried to a shorted load; and increasing and carrying the welding current to an arc load after the lapse of a delay period Tdr from the regeneration of the arc. When the welding speed Ws is less than a reference speed Wt, the delay time Tdr is set to a constant Tdi regardless of the value of the welding speed Ws, and when the welding speed Ws is the reference speed Wt or more, the delay time Tdr is changed according to the value of the welding speed Ws. Thus, since the delay time Tdr is optimized according to the welding Ws, the satisfactory welding quality can be secured even when the welding speed Ws is changed.

Description

  The present invention relates to a current control method for detecting the constriction of consumable electrode arc welding that detects the constriction of droplets during a short circuit and reduces the welding current immediately before the reoccurrence of arc to reduce the generation of spatter.

  FIG. 4 is a current / voltage waveform diagram and a droplet transfer diagram 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 of the welding current Iw for energizing the consumable electrode (hereinafter referred to as welding wire 1), and FIG. 4B shows the welding voltage Vw applied between the welding wire 1 and the base material 2. FIG. (C)-(E) show the state of transfer 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. Further, 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 progresses rapidly, and as shown to the same figure (E) at the time t3, the droplet 1a will detach | leave from the welding wire 1 to the molten pool 2a, and the arc 3 will generate | occur | produce again.

  When the constriction 1b is generated in the droplet 1a, the short circuit is opened after a short time of about several hundred μs, and the arc 3 is regenerated. That is, this constriction 1b becomes a precursor of short circuit opening. 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. This increase in resistance value increases as the constriction 1b progresses and the constricted portion becomes narrower. Therefore, the occurrence of the constriction 1b can be detected by detecting the change in the 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 dividing the welding voltage Vw by the welding current Iw. Further, the change in the welding current Iw during the constriction generation period is smaller than the change in the welding voltage Vw. For this reason, the occurrence of the constriction 1b can be detected by the change of the welding voltage Vw instead of the change of the resistance value. As a specific squeezing detection method, the rate of change (differential value) of the resistance value or welding voltage value Vw during the short-circuit period Ts is calculated, and this rate of change reaches a predetermined squeezing detection reference value corresponding thereto. Constriction is detected by discriminating. As a second method, as shown in FIG. 5B, a voltage rise value ΔV from a stable short-circuit voltage value Vs before the occurrence of constriction during the short-circuit period Ts is calculated, and this voltage rise at time t2. Necking is detected by determining that the value ΔV has reached a predetermined squeezing detection reference value Vtn. In the following description, the case where the constriction detection method is the second method will be described. However, the first method and other methods may be used. Detection of arc re-occurrence at time t3 can be easily performed by determining that the welding voltage Vw has become equal to or greater than the arc determination value Vta. That is, the period of Vw <Vta is the short circuit period Ts, and the period of Vw ≧ Vta is the arc period Ta. A period from detection of the occurrence of squeezing at times t2 to t3 to reoccurrence of the arc is hereinafter referred to as a squeezing detection period Tn.

  Next, when the arc is regenerated at time t3, the welding current Iw gradually decreases as shown in FIG. 5A, and the welding voltage Vw is about several tens of volts arc as shown in FIG. Changes to voltage value. During the arc period Ta, the tip of the welding wire 1 is melted by arc heat or the like to form the droplet 1a, and the base material 2 is melted. In general, a welding power source having a constant voltage characteristic is used for consumable electrode arc welding. In consumable electrode arc welding with a short circuit, when the welding current average value (feeding speed) is low, the droplet transfer form is a short circuit transfer form, and when it is high, it is a globule transfer form or a spray transfer form.

  In consumable electrode arc welding with a short circuit, when the current value Ia when the arc 3 is regenerated at time t3 is large, the pressure (arc force) from the arc 3 to the molten pool 2a becomes very large, and a large amount of spatter is generated. Will occur. That is, the amount of spatter generated increases substantially in proportion to the welding current value Ia when the arc is regenerated. Therefore, in order to suppress the occurrence of spatter, it is necessary to reduce the welding current value Ia when the arc is regenerated. As a method for this, various current control methods at the time of squeezing detection have been proposed in which the occurrence of the above-described squeezing is detected to reduce the welding current Iw to reduce the welding current value Ia when the arc is regenerated. Hereinafter, these conventional techniques will be described.

  FIG. 5 is a block diagram of a welding power source equipped with a current control method for squeezing detection according to the prior art. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200V as input, performs output control such as inverter control according to an error amplification signal Ea described later, and outputs an output voltage Vo and a welding current Iw. The power supply main circuit PM is not shown, but a primary rectifier circuit that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high frequency alternating current, and arc welding of the high frequency alternating current A transformer for stepping down the voltage to a voltage suitable for the above, a secondary rectifying circuit for rectifying the stepped down high frequency alternating current, a reactor for smoothing the rectified direct current, and a modulation for controlling the PWM modulation of the inverter circuit based on the error amplification signal Ea. Circuit. The parallel circuit of the transistor TR and the resistor R is inserted into the energization path, and as will be described later, when the constriction is detected, the transistor TR is turned off and energized through the resistor R to rapidly reduce the welding current Iw. The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the welding wire 1 and the base material 2, and a welding current Iw is conducted.

  The squeezing detection circuit ND receives the welding voltage Vw and detects a squeezing by the above-described squeezing detection method, and outputs a squeezing detection signal Nd that is at a low level during the squeezing detection period Tn. The drive circuit DR outputs a drive signal Dr that turns off the transistor TR only when the squeezing detection signal Nd is at a low level. That is, during the squeezing detection period Tn, the resistor R is inserted into the energization path, so that the energization path resistance value becomes ten times or more and the welding current Iw rapidly decreases. Since the transistor TR is in an on state during a period other than the constriction detection period Tn, the resistor R is short-circuited to have the same configuration as that of a normal welding power source.

  The delay period setting circuit TDR outputs a predetermined delay period setting signal Tdr. The rising period setting circuit TUR outputs a predetermined rising period setting signal Tur. The low current setting circuit IMR outputs a predetermined low current setting signal Imr. The high arc current setting circuit IHR outputs a predetermined high arc current setting signal Ihr. The squeezing detection current control circuit NIC receives the setting signals Tdr, Tur, Imr, Ihr and the squeezing detection signal Nd, and outputs a power supply characteristic switching signal Sw and a current setting signal Ir, which will be described later with reference to FIG. .

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The voltage detection circuit VD detects the output voltage Vo and outputs a voltage detection signal Vd. The voltage error amplification circuit EV amplifies an error between the voltage setting signal Vr and the voltage detection signal Vd, and outputs a voltage error amplification signal Ev. The current error amplification circuit EI amplifies an error between the current setting signal Ir and the current detection signal Id, and outputs a current error amplification signal Ei. The power supply characteristic switching circuit SW receives the power supply characteristic switching signal Sw as an input, and switches to the b side during the squeezing detection period Tn + delay period Td + rise period Tu described later with reference to FIG. 6 and error-amplifies the current error amplification signal Ei. The signal Ea is output, and during the other periods, the voltage is switched to the a side and the voltage error amplified signal Ev is output as the error amplified signal Ea. Therefore, the period switched to the a side is a constant current characteristic period, and the period switched to the b side is a constant voltage characteristic period.

  The feeding speed setting circuit FR outputs a predetermined feeding speed setting signal Fr. The feed control circuit FC inputs the feed speed setting signal Fr and outputs a feed control signal Fc for feeding the welding wire 1 at a feed speed corresponding to this value to the feed motor WM. To do.

  FIG. 6 is a timing chart of each signal in the above-described welding power source. (A) is the welding current Iw, (B) is the welding voltage Vw, (C) is the squeezing detection signal Nd, (D) is the power supply characteristic switching signal Sw (FIG. E) shows the time change of the current setting signal Ir. Hereinafter, a description will be given with reference to FIG.

  In the same figure, the periods other than the constant current characteristic period from time t2 to t5 have constant voltage characteristics as described above, and the transistor TR is turned on, so that the normal current / voltage waveform described above with reference to FIG. Be the same.

  At time t2, when the voltage increase value ΔV reaches the squeezing detection reference value Vtn as shown in FIG. 5B, the squeezing detection signal Nd changes to the low level as shown in FIG. In response to this, as shown in FIG. 4D, the power supply characteristic switching signal Sw is changed to the low level, and the power supply characteristic is switched to the constant current characteristic. At the same time, since the transistor TR is turned off, the welding current Iw rapidly decreases and is kept at the low current value Im as shown in FIG. When the arc is regenerated at time t3, the welding voltage Vw reaches the arc discriminating value Vta as shown in FIG. 5B, so that the squeezing detection signal Nd changes to the high level as shown in FIG. To do. During a predetermined delay period Td from time t3 to time t4, as shown in FIG. 9E, the current setting signal Ir is low and maintains a value determined by the current setting signal Imr. For this reason, the welding current Iw is low and the current value Im is maintained as shown in FIG. When the arc is regenerated at time t3, the welding current value is low and the current value Im, so that the arc force at the time of droplet detachment becomes weak and the occurrence of spatter is suppressed. Further, a predetermined delay period Td from the time when the arc is regenerated at time t3 to time t4 is provided, and during this delay period Td, the current setting signal Ir = Imr is maintained as shown in FIG. This waits for the vibration of the molten pool to settle due to the influence of the droplets transferred to the molten pool. Since the welding current Iw is increased after the weld pool vibration has subsided, the change in the arc force due to the current change and the vibration of the weld pool do not resonate and spatter does not occur. This delay period Td is set to an appropriate value according to the material of the base material, the feeding speed, etc., and is set to about 0.1 to 2 ms.

  When the delay period Td ends at time t4, the current setting signal Ir changes to a value determined by the predetermined high arc current setting signal Ihr during the rising period Tu as shown in FIG. As shown in FIG. 4D, since the power supply characteristic switching signal Sw is at the low level until time t5, the power supply characteristic is a constant current characteristic. For this reason, as shown in FIG. 5A, the welding current Iw rapidly increases and reaches a high arc current value Ih. At time t5, as shown in FIG. 4D, when the power supply characteristic switching signal Sw changes to the high level, the power supply characteristic is switched to the constant voltage characteristic. The subsequent operations are the same as those in FIG. (See Patent Document 1 for the above-described conventional technology)

JP 2006-247710 A

  In the prior art described above, the welding current Iw is maintained at the low current value Im, which is a small current value, during the delay period Td from the time when the arc is regenerated. This is for waiting for the vibration of the molten pool accompanying the droplet transfer to settle. If the welding current Iw is increased before the molten pool vibration accompanying the droplet transfer is settled, the vibration becomes intense due to the increase of the arc force, and spatter is generated. On the other hand, when this delay period Td becomes longer than necessary, the amount of heat input from the arc to the base metal decreases, and the welding state tends to become unstable.

  When the welding speed is relatively slow, less than about 50 cm / min, there is little adverse effect on the welding state even if the delay period Td is increased. For this reason, the delay period Td may be set so that the vibration of the molten pool accompanying the droplet transfer is sufficiently contained. When the welding speed is 50 cm / min or more, particularly about 80 cm / min or more, the welding state tends to become unstable if the delay period Td becomes longer than necessary. In this case, it is necessary to set to the minimum delay period Td in which the vibration of the molten pool accompanying the droplet transfer is settled. Thus, unless the delay period Td is set, it is not possible to suppress the generation of spatter and to prevent the welding state from becoming unstable.

  Therefore, in the present invention, even when the welding speed is increased, it is possible to suppress the occurrence of spatter at the time of arc re-occurrence and to detect the constriction of consumable electrode arc welding that can prevent the welding state from becoming unstable. An object is to provide a current control method.

In order to solve the above-described problem, the invention of claim 1 feeds the consumable electrode at a predetermined feeding speed and repeats an arc generation state and a short-circuit state between the consumable electrode and the base material. In consumable electrode arc welding, the constriction of droplets, which is a precursor to the occurrence of an arc again from the short circuit state, is detected, and when this constriction is detected, the welding current applied to the short circuit load is reduced and the arc is regenerated. In the current control method at the time of constriction detection of consumable electrode arc welding that increases the welding current at the time when a predetermined delay period has elapsed from the time when the current is applied to the arc load,
When the welding speed is less than a predetermined reference speed, the delay period is constant regardless of the value of the welding speed, and when the welding speed is equal to or higher than the reference speed, the delay period is set according to the value of the welding speed. Change,
This is a current control method for detecting constriction in consumable electrode arc welding.

The invention of claim 2 makes the delay period constant regardless of the value of the welding speed when the feed speed is less than a predetermined reference feed speed.
2. The current control method according to claim 1, wherein the constriction detection of consumable electrode arc welding is detected.

  According to the present invention, since the delay period is automatically optimized according to the welding speed, even if the welding speed is increased, the occurrence of spatter during arc re-generation is suppressed, and the welding state is unstable. Can be suppressed.

It is a block diagram of the welding power supply for implementing the current control method at the time of the constriction detection of consumable electrode arc welding which concerns on Embodiment 1 of this invention. FIG. 3 is a diagram illustrating an example of a delay period setting function built in a second delay period setting circuit TDR2 of FIG. It is a block diagram of the welding power supply for implementing the current control method at the time of the constriction detection of consumable electrode arc welding which concerns on Embodiment 2 of this invention. In prior art, it is the electric current and voltage waveform figure and droplet transfer figure in consumable electrode arc welding which repeat short circuit period Ts and arc period Ta. It is a block diagram of the welding power supply carrying the current control method at the time of a squeezing detection of a prior art. It is a timing chart of each signal in the welding power supply of FIG.

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

[Embodiment 1]
FIG. 1 is a block diagram of a welding power source for carrying out a current control method during constriction detection in consumable electrode arc welding according to Embodiment 1 of the present invention. This figure is obtained by adding a welding speed setting circuit WS to FIG. 5 described above and replacing the delay period setting circuit TDR of FIG. 5 with a second delay period setting circuit TDR2. In the figure, the same blocks as those in FIG. 5 are denoted by the same reference numerals, and description thereof is omitted. Hereinafter, the different blocks will be described with reference to FIG.

  The welding speed setting circuit WS outputs a predetermined welding speed setting signal Ws. In a welding apparatus using a robot, since the welding speed is set in a robot control device (not shown), information on the welding speed is sent from the robot control device to the welding speed setting circuit WS. And this welding speed setting circuit WS will output the welding speed setting signal Ws based on the sent information regarding the welding speed.

The second delay period setting circuit TDR2 receives the welding speed setting signal Ws as described above, calculates a delay period using a predetermined delay period setting function, and outputs a delay period setting signal Tdr. The delay period setting function will be described later with reference to FIG. 2, but the delay period setting signal Tdr becomes a value that changes as follows by this circuit.
1) When the value of the welding speed setting signal Ws is less than the predetermined reference speed Wt, the value of the delay period setting signal Tdr is made constant regardless of the value of the welding speed setting signal Ws.
2) When the value of the welding speed setting signal Ws is equal to or higher than the reference speed Wt, the value of the delay period setting signal Tdr is changed according to the value of the welding speed setting signal Ws. The change is made so that the value of the delay period setting signal Tdr decreases as the value of the welding speed setting signal Ws increases. That is, the delay period changes so as to increase as the welding speed increases. At this time, a lower limit value may be provided for the delay period. Of course, the delay period will not be less than zero.

  FIG. 2 is a diagram illustrating an example of a delay period setting function built in the above-described second delay period setting circuit TDR2. The horizontal axis of the figure shows the welding speed setting signal Ws (cm / min), and its range is 0 to 300 cm / min. The vertical axis represents the delay period setting signal Tdr (ms), and its range is 0 to 3 ms. The figure shows the case where the shielding gas is 100% carbon dioxide, the base material is steel, the welding wire diameter is 1.2 mm, and the feeding speed is 850 cm / min (welding current average value 250 A). It is. This will be described below with reference to FIG.

  In the figure, the reference speed Wt is set to 50 cm / min. In the function shown in the figure, when the value of the welding speed setting signal Ws is less than the reference speed, the delay period setting signal Tdr is a constant value that is a predetermined delay period initial value Tdi = 0.6 ms. When the value of the welding speed setting signal Ws is equal to or higher than the reference speed, the value of the delay period setting signal Tdr changes in a straight line descending to the right in inverse proportion to the value. When the welding speed setting signal Ws = 300 cm / min, Tdr = 0.1 ms. Under these welding conditions, a welding speed of about 300 cm / min is the upper limit speed of the weldable range.

In the figure, the change when Ws ≧ Wt is a straight line, but it may be curved. In that case, what is necessary is just to define a function like the following Formula, for example.
When Ws ≧ Wt, Tdr = (Tdi · Wt) / Ws
According to this equation, when Ws = Wt = 50 cm / min, Tdr = 0.6 ms, and when Ws = 300 cm / min, Tdr = 0.1 ms, both of which are the same as in FIG.

  The change pattern of the delay period setting signal Tdr when the reference speed Wt, the delay period initial value Tdi, and Ws ≧ Wt are in accordance with the type of shielding gas, the material of the base material, the diameter of the welding wire, the feeding speed, and the like. It is set to an appropriate value by experiment.

  The timing chart of each signal in the figure is the same as that in FIG. However, the delay period Td in FIG. 6 varies depending on the welding speed.

  Next, the function and effect of the first embodiment will be described. When the welding speed is a relatively slow speed that is less than the reference speed Wt, the delay period may be set to a length of time in which the vibration of the molten pool accompanying the droplet transfer is sufficiently contained, as in the prior art. When the welding speed changes within this range, the welding state does not become unstable even if the delay period is a constant value (delay period initial value Tdi). In this range, if the delay period is changed to become longer as the welding speed becomes slower, there is a problem that the bead appearance is deteriorated. Therefore, in this range, the delay period should be a constant value. When the welding speed is equal to or higher than the reference speed Wt, the delay period is shortened in inverse proportion to the welding speed. Thereby, after suppressing that the welding state becomes unstable, the delay period can be set so that the vibration of the molten pool accompanying the droplet transfer can be almost settled, so that the occurrence of spatter can also be suppressed. . The reason for this is that as the welding speed increases, the volume of the molten pool per unit length decreases, so the time for the vibration to settle is shortened. Therefore, according to the first embodiment, since the delay period is automatically optimized according to the welding speed, even when the welding speed is increased, the occurrence of spatter during arc re-generation is suppressed, and welding is performed. It can suppress that a state becomes unstable.

[Embodiment 2]
FIG. 3 is a block diagram of a welding power source for carrying out the current control method during constriction detection in consumable electrode arc welding according to Embodiment 2 of the present invention. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and the description thereof is omitted. This figure is obtained by replacing the second delay period setting circuit TDR2 of FIG. 1 with a third delay period setting circuit TDR3. Hereinafter, the different blocks will be described with reference to FIG.

The third delay period setting circuit TDR3 receives the feed speed setting signal Fr and the welding speed setting signal Ws as input, and when the value of the feed speed setting signal Fr is less than a predetermined reference feed speed Ft, a predetermined low speed is set. The delay period LTd at the feeding speed is output as the delay period setting signal Tdr, and when the value of the feeding speed setting signal Fr is equal to or higher than the reference feeding speed Ft, the delay period is calculated by a predetermined delay period setting function. The delay period setting signal Tdr is output. This delay period setting function is the same as in the first embodiment. With this circuit, the delay period setting signal Tdr has a value that varies as follows.
1) When the value of the feeding speed setting signal Fr is less than a predetermined reference feeding speed Ft, a predetermined low feeding speed delay period LTd is output as the delay period setting signal Tdr.
2) When Fr ≧ Ft:
21) When the value of the welding speed setting signal Ws is less than the predetermined reference speed Wt, the value of the delay period setting signal Tdr is made constant regardless of the value of the welding speed setting signal Ws.
22) When the value of the welding speed setting signal Ws is equal to or higher than the reference speed Wt, the value of the delay period setting signal Tdr is changed according to the value of the welding speed setting signal Ws. The change is made so that the value of the delay period setting signal Tdr decreases as the value of the welding speed setting signal Ws increases. That is, the delay period changes so as to increase as the welding speed increases.

  The difference between the second embodiment and the first embodiment is that the delay period when the feed speed is less than the reference feed speed Ft is set to a constant value (delay period at low feed speed LTd). In typical consumable electrode arc welding such as carbon dioxide arc welding, mag welding, and MIG welding, when the feed rate is slow, the droplet transfer mode becomes the short-circuit transfer mode, and when the feed rate increases, the globule transfer mode or spray transfer It becomes a form. Even in the globule transfer mode or spray transfer mode, the arc length (welding voltage) is set so as to be accompanied by a short circuit in order to prevent the occurrence of welding defects. The reference feed speed Ft is set so that the droplet transfer form is a substantially upper limit value of the feed speed that is the short-circuit transfer form. For example, in carbon dioxide arc welding, when the diameter of the welding wire is 1.2 mm, the reference feed speed Ft is set to 5 m / min (welding current average value of about 180 A). The low feed speed delay period LTd is the same value as the delay period initial value Tdi in the delay period setting function or a value larger than that when the feed speed is slightly faster than the reference feed speed Ft. Is set. The reference feed speed Ft and the low feed speed delay period LTd are set to appropriate values by experiments according to the type of shield gas (welding method), the material of the base material, the diameter of the welding wire, and the like.

  The timing chart of each signal in the figure is the same as that in FIG. However, the delay period Td in FIG. 6 varies depending on the feeding speed and the welding speed.

  Next, the function and effect of the second embodiment will be described. Since the operation and effect when the feeding speed is equal to or higher than the reference feeding speed Ft are the same as those in the first embodiment, the description thereof is omitted. When the feed rate is less than the reference feed rate Ft, as described above, the droplet transfer mode is a short-circuit transfer mode. In the short circuit transfer mode, the arc period and the short circuit period are regularly repeated, and the droplet transfer is also stable. For this reason, even if the delay period when the welding speed changes is a constant value, the welding state does not become unstable. In the short-circuit transition mode, the bead appearance is further improved when the delay period is not changed. Therefore, when the feed rate is less than the reference feed rate Ft, the delay period is maintained at a constant value even if the welding rate is changed, thereby suppressing the occurrence of spatter and the instability of the weld state, and the bead appearance. Becomes even better.

DESCRIPTION OF SYMBOLS 1 Welding wire 1a Droplet 1b Constriction 2 Base material 2a Weld pool 3 Arc 4 Welding torch 5 Feed roll Dr Drive signal Ea Error amplification signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC feed control circuit Fc feed control signal FR feed speed setting circuit Fr feed speed setting signal Ft reference feed speed Ia current value ID when arc is regenerated current detection circuit Id current detection signal Ih high arc current value IHR high Arc current setting circuit Ihr High arc current setting signal Im Low constriction current value IMR Low constriction current setting circuit Imr Low constriction current setting signal Ir Current setting signal Iw Welding current LTd Low feed rate delay period ND Constriction detection circuit Nd Constriction detection signal NIC Constriction detection current control circuit PM Power supply main circuit R Resistor SW Power supply characteristic switching circuit Sw Power supply characteristic Conversion signal Ta Arc period Td Delay period Tdi Delay period initial value TDR Delay period setting circuit Tdr Delay period setting signal TDR2 Second delay period setting circuit TDR3 Third delay period setting circuit Tn Neck detection period TR Transistor Ts Short circuit period Tu Rising period TUR Rising period setting circuit Tur Rising period setting signal VD Voltage detection circuit Vd Voltage detection signal Vo Output voltage VR Voltage setting circuit Vr Voltage setting signal Vs Short-circuit voltage value Vta Arc discrimination value Vtn Necking detection reference value Vw Welding voltage WM Feeding motor WS Welding Speed setting circuit Ws Welding speed setting signal Wt Reference speed ΔV Voltage rise value

Claims (2)

In consumable electrode arc welding in which the consumable electrode is fed at a predetermined feeding speed and the arc generation state and the short circuit state are repeated between the consumable electrode and the base material, and the arc is regenerated from the short circuit state. When the necking of the droplet, which is a precursor phenomenon, is detected, and the necking is detected, the welding current applied to the short-circuit load is reduced, and the welding current is detected when a predetermined delay period elapses after the arc is regenerated. In the current control method at the time of constriction detection of consumable electrode arc welding that increases the current to the arc load,
When the welding speed is less than a predetermined reference speed, the delay period is constant regardless of the value of the welding speed, and when the welding speed is equal to or higher than the reference speed, the delay period is set according to the value of the welding speed. Change,
A current control method for detecting a constriction in consumable electrode arc welding. When the feed speed is less than a predetermined reference feed speed, the delay period is constant regardless of the welding speed value.
The current control method for detecting constriction in consumable electrode arc welding according to claim 1.

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