JP6576294B2 - Pulse arc welding control method - Google Patents

Description

  The present invention relates to a countermeasure against magnetic blowing in consumable electrode pulse arc welding.

  In the consumable electrode pulse arc welding, welding is performed by feeding a welding wire and repeating a peak period for outputting a peak current and a peak voltage and a base period for outputting a base current and a base voltage. The peak current is set to a large current value of about 500 A, and the welding wire is melted to form and transfer droplets. The base current is set to about 30 A, and the welding wire hardly melts. In pulse arc welding, it is important to maintain a one-pulse, one-droplet transfer state in which one droplet is transferred by applying a single peak current in order to obtain a high-quality weld bead with less spattering. is there.

  In pulse arc welding of steel and the like, a magnetic field is often formed around the arc generating portion by a welding current passing through a base material, and the arc is often deformed by receiving a force from this magnetic field. Such a state is generally called magnetic blow or arc blow. When the state of occurrence of magnetic blow becomes worse, the arc is greatly deformed and the arc length becomes very long, the arc cannot be maintained, and an arc break occurs. When the arc break occurs, the welding quality deteriorates. For this reason, countermeasures against magnetic blowing are a major issue in pulse arc welding.

  In the invention of Patent Document 1, it is determined that the increase rate of the base voltage when the arc is generated during the base period is equal to or higher than the reference increase rate, and it is determined that the magnetic blow has occurred, and the base current is set to 200 A. The magnetic blow countermeasure control that increases rapidly as described above is performed. Magnetic blowing occurs during the base period when the arc stiffness becomes weak due to a small current value. The occurrence of magnetic blowing is determined by utilizing the fact that the arc voltage (base voltage) increases as the arc length increases due to magnetic blowing. Further, when the base current is increased, the rigidity of the arc becomes strong, and the deformation of the arc can be suppressed even when receiving a force from the magnetic field. As a result, arc interruption can be prevented. At this time, the base current needs to be increased rapidly. The reason for this is that since the magnetic blowing proceeds rapidly when it exceeds a certain level, the deformation of the arc cannot be suppressed if the increase in the base current is slow.

  A reactor for smoothing the welding voltage is provided inside the welding power source. Since the reactor is inserted in the welding current energization path (hereinafter sometimes simply referred to as the energization path), the change in the welding current is moderated. As the inductance value of the reactor increases, the change in welding current becomes more gradual. A saturable reactor may be used as a reactor. The saturable reactor has a quietness in which the inductance value becomes very large in the current range below the current saturation value and becomes extremely small in the current range larger than the saturation current value. The saturable reactor is designed so that the saturation current value is a little larger than the normal base current value. As a result, since the inductance value when the base current is energized is increased, the energized state is stabilized. Since the inductance value decreases in the current range larger than the saturation current value, the rate of change from the base current to the peak current can be set to a large value.

  When the inductance value of the reactor is large, the rate of increase when the base current is increased by discriminating the magnetic blow becomes gradual. As a result, the above-described prior art has a problem that the arc break cannot be suppressed because the increase in the base current is delayed with respect to the progress of the magnetic blowing.

JP 2004-268081 A

  Therefore, an object of the present invention is to provide a pulse arc welding control method that can suppress arc breakage due to magnetic blowing even when the inductance value of the reactor is large.

In order to solve the above-described problem, the invention of claim 1 is directed to feeding a welding wire, repeating a peak period for outputting a peak current and a peak voltage and a base period for outputting a base current and a base voltage, In a pulse arc welding control method in which a reactor is provided in a current and base current supply path, and the base current is increased based on an increase in the base voltage when an arc is generated to cope with magnetic blowing. ,
A transistor is provided in parallel with the reactor, and when the rising state of the base voltage is equal to or higher than a predetermined reference value, the transistor is turned on, the reactor is short-circuited, and the base current is increased.
It is the pulse arc welding control method characterized by this.

  The invention according to claim 2 is characterized in that the transistor is turned off when the increased value of the base current exceeds a predetermined reference current value. This is an arc welding control method.

  The invention according to claim 3 is characterized in that, when the reactor is a saturable reactor, the reference current value is set to a value larger than the saturation current value. It is.

  According to the present invention, when the occurrence of magnetic blowing is determined because the rising state of the base voltage is equal to or higher than the reference value, the transistor is turned on, the reactor is short-circuited, and the base current is rapidly increased. For this reason, in this invention, even when the inductance value of a reactor is large, the arc break by magnetic blowing can be suppressed.

It is a block diagram of the welding power supply for implementing the pulse arc welding control method which concerns on Embodiment 1 of this invention. It is a time chart of each signal in the welding power supply of FIG. 1 which shows the pulse arc welding control method which concerns on Embodiment 1 of this invention.

  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 the pulse arc welding control method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit MC receives a commercial power supply (not shown) such as a three-phase 200V, performs output control such as inverter control and thyristor phase control according to a current error amplification signal Ei described later, and outputs an output voltage suitable for welding. Output.

  Reactor WL is provided at the output of power supply main circuit MC and smoothes the output voltage. A saturable reactor may be used as the reactor WL. The saturable reactor has a large inductance value when the current value to be energized is less than the saturation current value, and the inductance value is small when the current value exceeds the saturation current value. Since the normal value of the base current Ib is about 20 to 50A, the saturable reactor is designed so that the saturation current value is about 50A.

  The welding wire 1 is fed through the welding torch 4 by the rotation of a feeding roll 5 coupled to a wire feeding motor (not shown), and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is conducted.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The voltage averaging circuit VAV averages the voltage detection signal Vd and outputs a voltage average signal Vav. The voltage setting circuit VR outputs a voltage setting signal Vr having a desired value.

  The voltage error amplification circuit EV amplifies an error between the voltage setting signal Vr and the voltage average signal Vav, and outputs a voltage error amplification signal Ev. The V / F converter VF outputs a pulse frequency signal Tf having a frequency corresponding to the voltage error amplification signal Ev. The pulse frequency signal Tf is a signal for determining a frequency having a peak period and a base period as one cycle.

  The peak period timer circuit TTP outputs a peak period signal Ttp that is at a high level for a predetermined peak period Tp for each frequency of the pulse frequency signal Tf. Therefore, the peak period signal Ttp is a signal that is at a high level during the peak period Tp and is at a low level during the base period.

  The arc determination circuit AD receives the voltage detection signal Vd as described above, determines whether or not an arc is generated based on this value, and outputs an arc determination signal Ad that is at a high level.

The base voltage rise state detection circuit DV receives the peak period signal Ttp, the arc determination signal Ad, and the voltage detection signal Vd, and the peak period signal Ttp is at a low level (base period Tb). A rising state of the voltage detection signal Vd (base voltage) when the arc discrimination signal Ad is at a high level (arc generation state) is detected, and a base voltage rising state detection signal Dv is output. The base voltage increase state detection signal Dv is calculated as follows, for example.
1) Rate of increase of voltage detection signal Vd in the arc generation state during the base period (differential ground)
2) Increase value (difference value) of the voltage detection signal Vd in the arc generation state during the base period from a predetermined reference base voltage value
3) Absolute value of the voltage detection signal Vd in the arc generation state during the base period

  The discrimination circuit HB receives the base voltage rise state detection signal Dv and the peak period signal Ttp as an input, and is set to a high level when the value of the base voltage rise state detection signal Dv exceeds a predetermined reference value. When the peak period signal Ttp becomes High level, a determination signal Hb that is reset to Low level is output. The reference value is a threshold value for determining that the rising state of the base voltage is in the state of occurrence of magnetic blow.

  The normal base current setting circuit IBSR outputs a normal base current setting signal Ibsr for setting a normal value of a predetermined base current. The setting range of the normal base current setting signal Ibsr is about 20 to 50A.

  Increase base current setting circuit IBUR outputs a predetermined increase base current setting signal Ibur. Increase base current setting signal Ibur is 200 A or more, and is set to be equal to or less than peak current setting signal Ipr. The increased base current setting signal Ibur is set to a value capable of suppressing the rapid deformation of the arc in a state where a magnetic blow occurs.

  The base current setting circuit IBR receives the determination signal Hb, the normal base current setting signal Ibsr, and the increased base current setting signal Ibur as an input, and outputs the normal base current setting signal Ibsr when the determination signal Hb is at a low level. The base current setting signal Ibr is output, and when the determination signal Hb is at the high level (magnetic blow occurrence state), the increased base current setting signal Ibur is output as the base current setting signal Ibr.

  The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr. The peak current setting signal Ipr is set to about 400 to 600 A according to the diameter, material, feeding speed, etc. of the welding wire.

  The current setting circuit IR receives the base current setting signal Ibr, the peak current setting signal Ipr, and the peak period signal Ttp as an input, and when the peak period signal Ttp is at a high level, the current setting circuit IR sets the peak current setting signal Ipr. When the peak period signal Ttp is at the low level, the base current setting signal Ibr is output as the current setting signal Ir.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. 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 drive circuit DR receives the discrimination signal Hb and the current detection signal id, and is set to a high level when the discrimination signal Hb changes to a high level. Thereafter, the value of the current detection signal Id is a predetermined reference current. When the value exceeds the value, the drive signal Dr that is reset to the low level is output. The transistor TR is connected in parallel with the reactor WL, and the drive signal Dr is connected to the base terminal. Therefore, the transistor TR is turned on when the drive signal Dr is at a high level, and is turned off when the drive signal Dr is at a low level. That is, when determining that the magnetic blow has occurred, the transistor TR is turned on, and the reactor WL is short-circuited. When the value of the welding current Iw increases to the reference current value, the transistor TR is turned off, and the reactor WL is in a normal state inserted in the energization path. The reference current value is set to be larger than the value of the normal base current setting signal Ibsr and not more than the value of the increased base current setting signal Ibur. When the reactor WL is a saturable reactor, the reference current value is set to a value about 10 to 50 A larger than the saturation current value. The setting range of the reference current value is set to about 60 to 100A.

  FIG. 2 is a time chart of each signal in the welding power source of FIG. 1 showing the pulse arc welding control method according to the first embodiment of the present invention. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the discrimination signal Hb, (D) Indicates the time change of the drive signal Dr. This figure shows a case where the reactor WL is a saturable reactor. The operation will be described below with reference to FIG.

  The figure shows a two-cycle waveform. The first period is a case where no magnetic blow occurs during the base period Tb. The second period is a case where magnetic blowing occurs during the base period Tb.

(1) Description of operation in the first period from time t1 to time t3 During a predetermined peak period Tp from time t1 to time t2, after increasing with an inclination from the base current Ib, as shown in FIG. It rapidly increases and a predetermined peak current Ip is energized. The reason for the inclination is that the inductance value of the saturable reactor is large. When the saturation current value is exceeded, the inductance value decreases and rapidly increases to the peak current Ip. At the same time, a peak voltage proportional to the arc length is applied as shown in FIG. The peak current Ip is set by the peak current setting signal Ipr in FIG. During the peak period Tp, the tip of the welding wire is melted to form droplets, and the droplets move to the molten pool at the timing before and after the end of the peak period Tp (1 pulse 1 droplet transfer state). The peak period Tp and the peak current Ip are set so as to be in this 1 pulse 1 droplet transfer state.

  During the base period Tb from time t2 to t3, no magnetic blow occurs, so as shown in FIG. 5A, the current decreases rapidly from the peak current Ip and then decreases with a slope. A base current Ib having a predetermined normal value is energized. The reason for the inclination is that, as described above, the inductance value of the saturable reactor becomes larger when the saturation current value is less than or equal to the saturation current value. At the same time, as shown in FIG. 5B, a normal base voltage Vb that is a substantially constant value is applied. The normal value base current Ib is set by the normal base current setting signal Ibsr in FIG.

  The above-described times t1 to t3 are one pulse period. The pulse period (pulse frequency) is feedback controlled (frequency modulation control) so that the average value of the welding voltage Vw becomes equal to the value of the voltage setting signal Vr. Thereby, the average value of the arc length is maintained at an appropriate value. Since the magnetic blow does not occur during the first period from time t1 to time t3, the discrimination signal Hb remains at the low level as shown in FIG. Further, as shown in FIG. 4D, since the drive signal Dr remains at the low level, the transistor TR in FIG. 1 is turned off, and the reactor WL is in a normal state where it is inserted into the energization path.

(2) Description of operation in second period from time t3 to t4 The operation in the peak period Tp from time t3 to t4 is the same as that from time t1 to t2. Further, the operation in the period from time t4 to t41 is the same as that from time t2 to t3.

  At time t41, since the magnetic blow has occurred, the arc is deformed and the arc length becomes gradually longer than the normal state. For this reason, as shown in FIG. 5B, the base voltage Vb increases from time t41, and the rising state becomes equal to or higher than the reference value at time t42. When the rising state of the base voltage Vb becomes equal to or higher than the reference value, the determination signal Hb changes to the high level as shown in FIG. In response to this, as shown in FIG. 4D, the drive signal Dr changes to the high level, the transistor TR is turned on, and the reactor WL is in a short circuit state (bypass state). For this reason, the inductance value of the current path is a small value even if it is less than the saturation current value. As shown in FIG. 9A, the base current Ib rapidly increases to the increased base current value Ibu because the inductance value is small. When the value of the base current Ib becomes equal to or higher than a predetermined reference current value at time t43 during the increase, the drive signal Dr returns to the off state and the reactor WL is inserted into the energization path as shown in FIG. Return to the state. The timing at which the drive signal Dr is reset to the low level may be the time when the value of the base current Ib reaches the increased base current value Ibu or the time when the next pulse cycle is started. The increased base current value Ibu is set by the increased base current setting signal Ibur in FIG.

  Since the base current Ib rapidly increases to the increased base current value Ibu from time t43 as shown in FIG. As a result, as shown in FIG. 5B, the base voltage Vb gradually increases from time t43, and thereafter decreases until time t5. During the period from time t43 to t5, the base current Ib maintains the increased base current value Ibu as shown in FIG. When the next pulse cycle starts at time t5, the determination signal Hb shown in FIG. The timing at which the determination signal Hb is reset to the low level may be the time when the rising state of the base voltage Vb ends and the falling state is reached. In the figure, the case where the reactor WL is a saturable reactor has been described, but the same applies to a normal reactor in which the inductance value is a substantially constant value regardless of the current range.

  Hereinafter, the action of the magnetic blow countermeasure by the pulse arc welding control method according to the first embodiment will be described. As described in the operation of the second period in FIG. 2, the occurrence of magnetic blow is determined based on the rising state of the base voltage Vb. When it is determined that the magnetic blow has occurred because the rising state of the base voltage Vb is equal to or higher than the reference value, the transistor TR is turned on, and the reactor WL is brought into a short circuit state (bypass state). Then, the base current Ib is rapidly increased to the increased base current value Ibu after reducing the inductance value of the current path. Thereby, the rigidity of the arc is quickly increased to prevent the occurrence of arc breakage. In the prior art, when the inductance value of the reactor is large, it takes time until the base current Ib reaches the increased base current value Ibu, and an arc break may occur. On the other hand, in this embodiment, it is possible to reliably prevent arc breakage.

  According to the first embodiment described above, a transistor is provided in parallel with the reactor of the energization path, and when the rising state of the base voltage is equal to or higher than a predetermined reference value, the transistor is turned on and the reactor is short-circuited. , Increase the base current rapidly. In the present embodiment, when the occurrence of magnetic blow is determined because the rising state of the base voltage is equal to or higher than the reference value, the transistor is turned on, the reactor is short-circuited, and the base current is rapidly increased. For this reason, in this Embodiment, even when the inductance value of a reactor is large, the arc break by magnetic blowing can be suppressed.

  Furthermore, in this embodiment, when the increased base current value is equal to or higher than a predetermined reference current value, the transistor may be returned to an off state. In this case, the transistor is turned on for a necessary minimum time, so that the loss of the transistor can be reduced and the cost is reduced. In addition, since the transistor is turned off before the current value becomes larger than necessary, the surge voltage at the time of turn-off can be suppressed to be small, and damage to the transistor can be suppressed.

  Further, in the present embodiment, when the reactor is a saturable reactor, the reference current value is set to a value 10 to 50 A larger than the saturation current value. Thereby, the ON state of the transistor can be set to a necessary minimum appropriate time.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll AD Arc discrimination circuit Ad Arc discrimination signal DR Drive circuit Dr Drive signal DV Base voltage rise state detection circuit Dv Base voltage rise state detection signal EI Current error amplification circuit Ei Current Error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal HB Discrimination circuit Hb Discrimination signal Ib Base current IBR Base current setting circuit Ibr Base current setting signal IBSR Normal base current setting circuit Ibsr Normal base current setting signal IBUR Increase base current setting circuit Ibur Increase base current setting signal ID Current detection circuit Id Current detection signal Ip Peak current IPR Peak current setting circuit Ipr Peak current setting signal IR Current setting circuit Ir Current setting signal Iw Welding current MC Power supply main circuit Tb Base period Tf Pulse frequency signal Tp Peak period TR transistor TTP peak period timer circuit Ttp peak period signal VAV voltage averaging circuit Vav voltage average signal Vb base voltage VD voltage detection circuit Vd voltage detection signal VF V / F converter VR voltage setting circuit Vr voltage setting signal Vw welding voltage WL reactor

Claims (3)

A welding wire is fed, and a peak period for outputting a peak current and a peak voltage and a base period for outputting a base current and a base voltage are repeated, and a reactor is provided in the current path for the peak current and the base current, In a pulse arc welding control method for dealing with magnetic blowing by increasing the base current based on an increase in the base voltage when an arc is generated,
A transistor is provided in parallel with the reactor,
When the rising state of the base voltage is equal to or higher than a predetermined reference value, the transistor is turned on, the reactor is short-circuited, and the base current is increased.
The pulse arc welding control method characterized by the above-mentioned. When the increased value of the base current is equal to or higher than a predetermined reference current value, the transistor is turned off.
The pulse arc welding control method according to claim 1. When the reactor is a saturable reactor, the reference current value is set to a value larger than the saturation current value.
The pulse arc welding control method according to claim 2, wherein:

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