JP2023015630A - Pulse arc welding control method - Google Patents

Abstract

To prevent arc breakage due to magnetic blow and stably maintain a welding state in consumable electrode pulse arc welding.SOLUTION: In a pulse arc welding control method that feeds a welding wire and performs welding by repeating a peak period Tp for outputting peak current Ip and peak voltage and a base period Tb for outputting base current Ib and base voltage Vb, the base current Ib is oscillated within a current range of 100 A or less, and with an amplitude of 40 A or more and a frequency of 300 Hz or more. Magnetic blow is discriminated (Hd) on the basis of rise in the base voltage Vb when arcing, and after discriminating (Hd) magnetic blow, oscillation of the base current Ib is started.SELECTED DRAWING: Figure 2

Description

The present invention relates to countermeasures against magnetic blow in consumable electrode pulsed arc welding.

In consumable electrode pulse arc welding, welding is performed by feeding a welding wire and repeating a peak period during which peak current and peak voltage are output and a base period during which base current and base voltage are output. The peak current is set to a large current value of about 500 A, which is equal to or higher than the critical current value, and the welding wire is melted to form and transfer droplets. The base current is set to about 40 A, which is less than the critical current value, and the welding wire hardly melts. When the welding current value is greater than or equal to the critical current value, the droplet transfer state is in the spray transfer state. In pulsed arc welding, it is important to maintain the state of 1 pulse cycle 1 droplet transfer in which 1 droplet is transferred by energizing a single peak current in order to obtain a high quality weld bead with little spatter. is.

In pulse arc welding of iron and steel, a magnetic field is formed around the arc generating portion by the welding current passing through the base metal, and the arc is often deformed by receiving force from this magnetic field. Such a state is generally called magnetic blow or arc blow. If the magnetic blow occurs severely, the arc is greatly deformed and the arc length becomes very long, and the arc cannot be maintained, resulting in arc breakage. Welding quality deteriorates when arc breakage occurs. Therefore, countermeasures against magnetic blow are a major issue in pulsed arc welding.

In the invention of Patent Document 1, it is determined that the magnetic blow has occurred by detecting that the rate of increase of the base voltage when the arc is occurring during the base period exceeds the reference rate of increase, and the base current is reduced to 200A. Control is being performed to cope with the rapidly increasing magnetic blow. Magnetic blow occurs during the base period when the arc stiffness becomes weak due to the small current value. The occurrence of magnetic blow is determined by utilizing the fact that the arc voltage (base voltage) increases as the arc length increases due to magnetic blow. Also, increasing the base current increases the rigidity of the arc, so that deformation of the arc can be suppressed even if force is applied from the magnetic field. As a result, arc interruption can be prevented.

Japanese Patent Application Laid-Open No. 2004-268081

If the base current is increased to 200 A or more as a countermeasure against magnetic blow in the prior art, arc breakage can be prevented. However, increasing the base current to a high current value of 200 A or more accelerates the melting of the welding wire to form droplets. As a result, there is a problem that the welding state is deviated from the one-pulse-cycle, one-droplet-transfer state, and the welding state deteriorates from the good state.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a pulsed arc welding control method capable of preventing arc breakage due to magnetic arc blow and maintaining a good welding state.

In order to solve the above-mentioned problems, the invention of claim 1 is
In a pulse arc welding control method for feeding a welding wire and repeatedly welding 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 base current is oscillated with a current range of 100 A or less, an amplitude of 40 A or more, and a frequency of 300 Hz or more;
A pulse arc welding control method characterized by:

The invention of claim 2 is
determining magnetic blow based on the increase in the base voltage when an arc is generated;
starting the oscillation of the base current after determining the magnetic blow;
The pulse arc welding control method according to claim 1, characterized in that:

The invention of claim 3 is
the average value of the base current when vibrating is equal to the value of the base current when not vibrating;
The pulse arc welding control method according to claim 2, characterized in that:

According to the present invention, in consumable electrode pulse arc welding, it is possible to prevent arc breakage due to magnetic blow and maintain a good welding state.

1 is a block diagram of a welding power source for carrying out a pulse arc welding control method according to Embodiment 1 of the present invention; FIG. FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1 showing the pulse arc welding control method according to Embodiment 1 of the present invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a welding power source for carrying out a pulse arc welding control method according to an embodiment of the present invention. Each block will be described below with reference to FIG.

The power supply main circuit MC receives a commercial power supply (not shown) such as 3-phase 200 V, performs output control such as inverter control according to a current error amplification signal Ei described later, and outputs an output voltage suitable for welding.

A reactor WL smoothes the output of the power supply main circuit MC.

The welding wire 1 is fed through the welding torch 4 by 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 a power supply tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is applied.

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

A 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. A V/F converter VF outputs a pulse frequency signal Tf having a frequency corresponding to the voltage error amplification signal Ev. This pulse frequency signal Tf is a signal that determines a frequency having a peak period and a base period as one cycle.

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

The arc determination circuit AD receives the voltage detection signal Vd, determines whether an arc is generated based on this value, and outputs an arc determination signal Ad at a high level.

The base voltage rising state detection circuit DV receives the peak period signal Ttp, the arc discrimination signal Ad, and the voltage detection signal Vd as inputs, the peak period signal Ttp is at Low level (base period Tb), and A rising state of the voltage detection signal Vd (base voltage) when the arc discrimination signal Ad is at High level (arc generation state) is detected, and a base voltage rising state detection signal Dv is output. The base voltage rising state detection signal Dv is calculated, for example, as follows.
1) Rise rate (differential value) of the voltage detection signal Vd in the state of arc generation during the base period
2) Increase value (difference value) of the voltage detection signal Vd in an arc occurrence state during the base period from a predetermined reference base voltage value
3) Absolute value of voltage detection signal Vd in arcing state during base period

The magnetic blow countermeasure mode selection circuit MS is a switch or the like provided on the front panel of the welding power source, and when the welding operator determines that the work is subject to frequent magnetic blow and selects the "magnetic blow countermeasure mode", the signal goes high. Thus, when the "normal mode" is selected, the magnetic blow countermeasure mode selection signal Ms, which becomes Low level, is output.

The magnetic blow discrimination circuit HB receives the magnetic blow countermeasure mode selection signal Ms, the base voltage rise state detection signal Dv, and the peak period signal Ttp as inputs, and performs any of the following processes 1) to 3). and outputs a magnetic blow determination signal Hd.
Process 1) When the magnetic blow countermeasure mode selection signal Ms is at the High level (magnetic blow countermeasure mode), the magnetic blow determination signal Hd which is always at the High level is output.
Process 2) When the magnetic blow countermeasure mode selection signal Ms is at Low level (normal mode), if the value of the base voltage rising state detection signal Dv becomes equal to or greater than a predetermined reference value, it is set to High level, and then during the peak period. When the signal Ttp becomes High level, it outputs a magnetic blow discrimination signal Hd which is reset to Low level.
Process 3) When the magnetic blow countermeasure mode selection signal Ms is at Low level (normal mode), if the value of the base voltage rise state detection signal Dv becomes equal to or greater than a predetermined reference value, it is set to High level, and then welding is started. A magnetic blow discrimination signal Hd is output which is reset to Low level upon completion.

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

The oscillation base current setting circuit IBBR outputs an oscillation base current setting signal Ibbr that periodically oscillates with a waveform such as a rectangular wave, a triangular wave, or a sine wave. The oscillation base current setting signal Ibbr oscillates at a current range of 100 A or less, an amplitude of 40 A or more, and a frequency of 300 Hz or more. The average value of the oscillating base current setting signal Ibbr is preferably set equal to the value of the normal base current setting signal Ibsr.

A base current setting circuit IBR receives the magnetic blow discrimination signal Hd, the normal base current setting signal Ibsr, and the vibration base current setting signal Ibbr as inputs, and when the magnetic blow discrimination signal Hd is at a low level, the normal base current It outputs a base current setting signal Ibr which becomes a setting signal Ibsr and becomes a vibration base current setting signal Ibbr when the magnetic blow discrimination signal Hd is at a high level.

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

A current setting circuit IR receives the base current setting signal Ibr, the peak current setting signal Ipr, and the peak period signal Ttp as inputs, and sets the peak current setting signal Ipr when the peak period signal Ttp is at a high level. When the peak period signal Ttp is at Low level, the base current setting signal Ibr is output as the current setting signal Ir.

A current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. A 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.

FIG. 2 is a timing chart of each signal in the welding power source of FIG. 1 showing the pulse arc welding control method according to the 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, and (C) shows the time change of the magnetic blow discrimination signal Hd. The operation of each signal will be described below with reference to FIG.

The figure shows waveforms of two cycles, and is a case where the occurrence of magnetic blow is determined during the first cycle.

(1) Description of operation in the first cycle During a predetermined peak period Tp from time t1 to t2, a predetermined peak current Ip is applied as shown in FIG. , a peak voltage proportional to the arc length is applied. The peak current Ip is set by the peak current setting signal Ipr of FIG. During the peak period Tp, the tip of the welding wire is melted to form a droplet, and the droplet transfers to the molten pool around the end of the peak period Tp (one pulse period, one droplet transfer state). The peak period Tp and the peak current Ip are set so as to achieve this one pulse period one droplet transfer state.

A period from time t2 to t3 is the base period Tb. Time t1 to t3 is one pulse period. The pulse period (pulse frequency) is feedback controlled (frequency modulation controlled) so that the average value of the welding voltage Vw becomes equal to the value of the voltage setting signal Vr in FIG. As a result, the average arc length is maintained at a proper value.

During the period from time t2 to t21 in the base period Tb, no magnetic blow occurs, so as shown in FIG. ), a substantially constant base voltage Vb of a normal value is applied. The normal base current is set by the normal base current setting signal Ibsr in FIG.

At time t21, the arc is deformed due to the occurrence of magnetic blow, and the arc length gradually becomes longer than in the normal state. Therefore, as shown in FIG. 2B, the base voltage Vb rises from time t21, and at time t22, the rising state becomes equal to or higher than a predetermined reference value. The rising state of the base voltage Vb is detected by the base voltage rising state detection signal Dv of FIG. When the rising state of the base voltage Vb reaches or exceeds the reference value, the magnetic blow discrimination signal Hd changes to High level as shown in FIG. In response to this, the base current Ib is switched from a constant normal base current to a square-wave oscillating base current Ibb, as shown in FIG. The vibration base current Ibb is set by the vibration base current setting signal Ibbr in FIG. The oscillating base current Ibb oscillates with an amplitude of 40 A or more and a frequency of 300 Hz or more in a current range of 100 A or less. For this reason, the rigidity of the arc increases, and deformation of the arc due to magnetic blow can be suppressed. The reason why the oscillation base current Ibb is set to 100 A or less is to suppress the droplet growth and maintain the one-pulse cycle, one-drop transfer state. Here, in order to more reliably maintain the 1-pulse-cycle 1-drop transfer state, it is preferable to set the average value of the oscillating base current Ibb equal to the value of the normal base current. The reason why the oscillating base current Ibb is oscillated with an amplitude of 40 A or more and a frequency of 300 Hz or more is to generate rigidity of the arc that can resist deformation of the arc due to magnetic blow. After time t22, since the deformation of the arc is suppressed, the rising state of the base voltage Vb returns to the normal value as shown in FIG.

The magnetic blow determination signal Hd becomes High level under one of the following three conditions.
Process 1) When the welding operator selects the "magnetic blow countermeasure mode" by means of the magnetic blow countermeasure mode selection signal Ms shown in FIG. In this case, the base current Ib always becomes the oscillating base current Ibb regardless of the increase state of the base voltage Vb. When the welding operator judges that the work state is such that magnetic blow is likely to occur, he can select the "magnetic blow countermeasure mode". As a result, it is possible to reliably suppress deformation of the arc due to magnetic blow and prevent arc burnout without judging the occurrence of magnetic blow based on the rising state of the base voltage Vb. On the other hand, since the base current Ib is always an oscillating base current Ibb, it has the weak point that the noise from the arc increases.

Process 2) When the welder selects the "normal mode" by means of the magnetic blow countermeasure mode selection signal Ms shown in FIG. When it reaches a predetermined reference value or more, it is set to High level, and when the peak period signal Ttp of FIG. 1 becomes High level after that, it is reset to Low level. That is, the magnetic blow determination signal Hd becomes High level when the rise state of the base voltage Vb reaches or exceeds the reference value, and returns to Low level when the next cycle starts. In this case, the base current Ib is switched to the oscillating base current Ibb only in the period in which the magnetic blow is detected, so that the deformation of the arc due to the magnetic blow can be suppressed and the arc can be prevented from breaking. As a result, the noise caused by the oscillating base current Ibb is also suppressed. On the other hand, it is necessary to reliably determine the magnetic blow, and if the determination fails, the arc will be deformed.

Process 3) When the welder selects the "normal mode" with the magnetic blow countermeasure mode selection signal Ms of FIG. When it reaches a predetermined reference value or more, it is set to High level, and after that, when welding is completed, it is reset to Low level. That is, the magnetic blow discrimination signal Hd becomes High level when the rise state of the base voltage Vb reaches or exceeds the reference value, and returns to Low level when welding of the workpiece is completed. In this case, the base current Ib is switched to the oscillating base current Ibb only in the period after the magnetic blow is detected, so that the deformation of the arc due to the magnetic blow can be suppressed and the arc can be prevented from breaking. As a result, since the current is switched to the vibration base current Ibb after the magnetic blow is determined, the noise is limited. Furthermore, once magnetic arc blow is identified, the oscillation base current is Ibb until welding is completed. Therefore, even if the accuracy of magnetic arc arc identification is slightly poor, arc deformation and arc breakage can be suppressed.

(2) Description of Operation in Second Period The operation during the peak period Tp from time t3 to t4 is the same as that from time t1 to t2. Also, since this figure shows the case of the process 3) described above, during the base period Tb from time t4 to t5, the base current Ib becomes the oscillation base current Ibb as shown in FIG. there is Therefore, as shown in (C) of the figure, the magnetic blow discrimination signal Hd remains at the High level after time t22.

1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll AD Arc discrimination circuit Ad Arc discrimination 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 Magnetic blow discrimination circuit Hd Magnetic blow discrimination signal Ib Base current Ibb Oscillation base current IBBR Oscillation base current setting circuit Ibbr Oscillation base current setting signal IBR Base current setting circuit Ibr Base current setting signal IBSR Normal base current Setting circuit Ibsr Normal 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 MS Magnetic blow countermeasure mode selection Circuit Ms Magnetic blow mode selection signal Tb Base period Tf Pulse frequency signal Tp Peak period 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)

In a pulse arc welding control method for feeding a welding wire and repeatedly welding 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 base current is oscillated with a current range of 100 A or less, an amplitude of 40 A or more, and a frequency of 300 Hz or more;
A pulse arc welding control method characterized by: determining magnetic blow based on the increase in the base voltage when an arc is generated;
starting the oscillation of the base current after determining the magnetic blow;
The pulse arc welding control method according to claim 1, characterized in that: the average value of the base current when vibrating is equal to the value of the base current when not vibrating;
The pulse arc welding control method according to claim 2, characterized in that:

Images