JP6882832B2 - AC non-consumable electrode arc welding control method - Google Patents

Description

The present invention relates to an AC non-consumable electrode arc welding control method in which an electrode negative polarity period and an electrode positive polarity period are alternately repeated, and a re-ignition voltage is applied to weld when switching to the electrode positive polarity period. ..

AC non-consumable electrode arc welding includes AC TIG welding, AC plasma arc welding, and the like. In AC non-consumable electrode arc welding, a non-consumable electrode such as a tungsten electrode is used for the electrode, and while the electrode is shielded from the atmosphere by a shield gas such as argon gas, an AC welding current is applied to generate an arc for welding. I do. The alternating current welding current is formed from the electrode negative polarity current during the electrode negative polarity period and the electrode positive polarity current during the electrode positive polarity period. The negative electrode polarity and the positive electrode polarity are repeated alternately, and the negative electrode polarity and the positive electrode polarity form one cycle.

AC non-consumable electrode arc welding is mainly used for welding aluminum. There is an oxide film on the surface of the aluminum material, which is the base material, and good welding cannot be performed unless this is removed. In AC non-consumable electrode arc welding, a cathode point is formed on the surface of the base metal during the positive polarity period of the electrode. The action of removing the oxide film (cleaning action) works by the energy when the cathode point is formed. That is, in AC non-consumable electrode arc welding, the oxide film is removed by exerting a cleaning action by providing an electrode positive polarity period. At this time, since the non-consumable electrode wears quickly during the electrode positive polarity period, it is set to the shortest period during which an appropriate cleaning width can be secured. The time ratio of the electrode negative polarity period to one cycle is about 70%. In the following description, the non-consumable electrode may be simply referred to as an electrode.

In AC non-consumable electrode arc welding, arc breakage may occur when the polarity is switched. In particular, when switching from the negative electrode polarity to the positive electrode polarity, arc breakage is likely to occur. Therefore, when switching from the negative electrode polarity to the positive electrode polarity, a re-ignition voltage of about 300 V is superimposed on the welding voltage to suppress arc breakage. When the arc breaks, the welding quality deteriorates.

However, even if a re-ignition voltage is applied, arc breakage may occur depending on the welding conditions. Therefore, in the invention of Patent Document 1, when the arc breakage is detected during the positive polarity period of the electrode, the arc is reignited smoothly by switching to the negative polarity period of the electrode before the positive polarity period of the electrode ends. ing.

Japanese Patent No. 5429356

In the prior art, when the occurrence of arc breakage is detected, the re-ignition of the arc is facilitated. However, in the prior art, there is a problem that the welding quality deteriorates because the arc breakage occurs once.

Therefore, an object of the present invention is to provide a non-consumable electrode arc welding control method capable of suppressing the occurrence of arc breakage.

In order to solve the above-mentioned problems, the invention of claim 1 is
In the AC non-consumable electrode arc welding control method in which the electrode negative polarity period and the electrode positive polarity period are alternately repeated and a re-ignition voltage is applied at the time of switching to the electrode positive polarity period for welding.
When the average welding current value is 100 A or more and a precursory state of arc breakage is detected during the electrode positive polarity period, the electrode is switched to the electrode negative polarity period before the end of the electrode positive polarity period.
This is an AC non-consumable electrode arc welding control method.

The invention of claim 2 is performed by detecting the precursor state of the arc breakage when the arc is generated and the welding current (absolute value) less than a predetermined reference current value is energized. ,
The AC non-consumable electrode arc welding control method according to claim 1, wherein the AC non-consumable electrode arc welding is controlled.

According to the third aspect of the present invention, the precursor state of the arc breakage is detected during the period in which the re-ignition voltage is applied.
The AC non-consumable electrode arc welding control method according to claim 1 or 2.

According to the present invention, the occurrence of arc breakage can be suppressed.

It is a block diagram of the welding apparatus for carrying out the AC non-consumable electrode arc welding control method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding apparatus of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is a block diagram of a welding apparatus for carrying out the AC non-consumable electrode arc welding control method according to the first embodiment of the present invention. Hereinafter, each block will be described with reference to the figure.

The inverter circuit INV uses an AC commercial power supply (not shown) such as 3-phase 200V as an input, and controls the rectified and smoothed DC voltage by pulse width modulation control by the current error amplification signal Ei described later, and performs high-frequency AC. Is output.

The inverter transformer INT steps down the high frequency AC voltage to a voltage value suitable for arc welding.

The secondary rectifiers D2a to D2d rectify the stepped-down high-frequency alternating current to direct current.

The electrode positive polarity transistor PTR is turned on by the electrode positive polarity drive signal Pd described later, and the output of the welding power supply becomes the electrode positive polarity EP. The electrode negative polarity transistor NTR is turned on by the electrode negative polarity drive signal Nd described later, and the output of the welding power supply becomes the electrode negative polarity EN.

The reactor WL smoothes the rippled output.

An electrode 1 is attached to the tip of the welding torch 4, and an arc 3 is generated between the electrode 1 and the base metal 2. An alternating current welding current Iw is energized in the arc 3, and an alternating current welding voltage Vw is applied between the electrode 1 and the base metal 2. The welding current Iw is conventionally set to the + side when energized in the direction of the base material 2 → arc 3 → electrode 1 (when the electrode negative polarity period Ten).

The electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr. The electrode positive polarity period setting circuit TPR outputs a predetermined electrode positive polarity period setting signal Tpr. Tnr = about 10 ms and Tpr = about 3 ms.

The current detection circuit ID detects the absolute value of the welding current Iw and outputs the current detection signal Id.

The current comparison circuit CM takes the above-mentioned current detection signal Id as an input, and outputs a current comparison signal Cm which is a high level when the value of the current detection signal Id is equal to or less than a predetermined polarity switching current value. The polarity switching current value is set to, for example, 50A.

The timer circuit TM performs the following processing with the above-mentioned electrode negative polarity period setting signal Tnr, the above-mentioned electrode positive polarity period setting signal Tpr, the above-mentioned current comparison signal Cm, and the above-mentioned arc break sign detection signal Zd as inputs. Outputs the timer signal Tm. When the timer signal Tm is 1 or 2, the electrode negative polarity period Ten is obtained, and when the timer signal Tm is 3 or 4, the electrode positive polarity period Temp is obtained.
1) The timer signal Tm = 1 is output during the period determined by the electrode negative polarity period setting signal Tnr.
2) Subsequently, the timer signal Tm = 2 is output during the transition period from the elapse of the period determined by the electrode negative polarity period setting signal Tnr until the current comparison signal Cm changes to the High level.
3) Subsequently, after the current comparison signal Cm changes to the High level, the timer signal Tm = 3 is output during the period determined by the electrode plus polarity period setting signal Tpr. However, if the arc break sign detection signal Zd reaches the High level for a short time during this period, the operation of 1) is forcibly shifted to that point.
4) Subsequently, the timer signal Tm = 4 is output during the transition period from the elapse of the period determined by the electrode positive polarity period setting signal Tpr until the current comparison signal Cm changes to the High level.
5) Repeat steps 1) to 4) above.

The secondary drive circuit DV takes the timer signal Tm as an input, outputs the electrode negative polarity drive signal Nd when the timer signal Tm is 1 or 2, and outputs the electrode negative polarity drive signal Nd when the timer signal Tm is 3 or 4. Outputs the electrode positive polarity drive signal Pd of. As a result, when the timer signal Tm is 1 or 2, the electrode negative polarity transistor NTR is turned on, and the electrode negative polarity period Ten is set. When the timer signal Tm is 3 or 4, the electrode positive polarity transistor PTR is turned on and the electrode positive polarity period is set.

The re-ignition voltage application circuit SD receives the above timer signal Tm as an input, and has a re-ignition voltage of about 300 V for a short time (about 0.3 ms) from the time when the timer signal Tm is switched to 3 (electrode positive polarity period). Is applied between the electrode 1 (+) and the base material 2 (−).

The electrode negative polarity current amplitude setting circuit INR outputs a predetermined electrode negative polarity current amplitude setting signal Inr. The electrode positive polarity current amplitude setting circuit IPR outputs a predetermined electrode plus polarity current amplitude setting signal Ipr. Inr and Ipr are positive values.

The average welding current detection circuit IAD takes the above current detection signal Id as an input, calculates an average value, and outputs an average welding current detection signal Iad. The average value is calculated, for example, by passing the current detection signal Id through a low-pass filter having a cutoff frequency of about 1 to 5 Hz. Further, the average value may be calculated by sampling the current detection signal Id every about 0.1 ms and calculating the average value at each predetermined cycle of the welding current waveform.

The arc discrimination circuit AD takes the above current detection signal Id as an input, and when this value is equal to or higher than a predetermined current energization discrimination value (about 1A), the arc discrimination signal AD determines that an arc is generated and becomes a high level. Outputs Ad.

The arc break sign detection circuit ZD receives the above-mentioned average welding current detection signal Iad, the above-mentioned timer signal Tm, the above-mentioned arc discrimination signal Ad, and the above-mentioned current detection signal Id as inputs, and the average welding current detection signal Iad is 100 A or more. Yes, the timer signal Tm is 3 (electrode positive polarity period Tep), the arc discrimination signal Ad is at High level (arc generation state), and Id is during a predetermined period (about 0.2 ms). When it becomes less than the predetermined reference current value It (about 15A), the arc break sign detection signal Zd which becomes the high level for a short time is output.

The switching circuit SW receives the above timer signal Tm, the above electrode negative polarity current amplitude setting signal Inr, and the above electrode positive polarity current amplitude setting signal Ipr as inputs, performs the following processing, and outputs the current setting signal Ir.
1) When the timer signal Tm = 1, the electrode negative polarity current amplitude setting signal Inr is output as the current setting signal Ir.
2) When the timer signal Tm = 2, the current setting signal Ir = 0 is output.
3) When the timer signal Tm = 3, the electrode positive polarity current amplitude setting signal Ipr is output as the current setting signal Ir.
4) When the timer signal Tm = 4, the current setting signal Ir = 0 is output.

The current error amplifier circuit EI amplifies the error between the current setting signal Ir and the current detection signal Id, and outputs the current error amplification signal Ei. As a result, the welding power source has a constant current characteristic, and the alternating current welding current Iw is energized.

FIG. 2 is a timing chart of each signal in the welding apparatus of FIG. FIG. (A) shows the time change of the welding current Iw, FIG. (B) shows the time change of the current comparison signal Cm, and FIG. 3 (C) shows the time change of the electrode negative polarity drive signal Nd. FIG. (D) shows the time change of the electrode positive polarity drive signal Pd, FIG. (E) shows the time change of the current setting signal Ir, and FIG. .. The welding current Iw shown in FIG. 0A is the electrode negative polarity current Ien from 0 to the upper side and the electrode positive polarity current Iep from 0 to the lower side. The figure shows a non-equilibrium waveform in which the amplitude of the electrode positive polarity EP of the welding current Iw is larger than the amplitude of the electrode negative polarity EN. Further, the figure shows the case where the average welding current value is 100 A or more. Hereinafter, the operation of each signal will be described with reference to the figure.

During the electrode positive polarity period Tep at times t1 to t4 and the electrode negative polarity period Ten at times t4 to t7, a stable arc generation state is achieved without a precursor state of arc breakage. The figure shows a case where the arc is broken during the electrode positive polarity period Tep from time t7.

At time t1, as shown in FIG. (B), when the current comparison signal Cm reaches the High level for a short time, the timer signal Tm becomes 3, and as shown in FIG. The Pd becomes the High level, the electrode positive polarity transistor PTR is turned on, and the electrode positive polarity EP is switched to. At the same time, as shown in FIG. 6C, the electrode negative polarity drive signal Nd becomes the Low level, and the electrode negative polarity transistor NTR is turned off. At time t1, as shown in FIG. (E), the current setting signal Ir switches from 0 to the positive electrode positive polarity current amplitude setting signal Ipr. As shown in FIG. 3A, the welding current Iw instantaneously changes from a positive polarity switching current value to a negative polarity switching current value. At the same time, a re-ignition voltage is applied between the electrode 1 and the base metal 2. During the electrode positive polarity period Tep at times t1 to t4, the absolute value of the welding current Iw is equal to or higher than the reference current value It.

During the period of time t1 to t2, as shown in FIG. 6A, the welding current Iw increases with an inclination from the polarity switching current value to the value of the electrode plus polarity current amplitude setting signal Ipr. This inclination is determined by the inductance value of the reactor WL and the welded cable. During the period of time t2 to t3, as shown in FIG. 6A, the welding current Iw becomes the value of the electrode plus polarity current amplitude setting signal Ipr.

At time t3, when the elapsed time from time t1 reaches the value of the electrode plus polarity period setting signal Tpr, the timer signal Tm becomes 4, and as shown in FIG. .. In response to this, as shown in FIG. 3A, the welding current Iw decreases with an inclination. This inclination is also determined by the inductance value of the reactor WL and the welded cable. Then, when the value of the welding current Iw becomes equal to or less than the polarity switching current value at time t4, the current comparison signal Cm becomes the High level for a short time as shown in FIG.

At time t4, as shown in FIG. 6A, the absolute value of the welding current Iw becomes equal to or less than the predetermined polarity switching current value. Therefore, as shown in FIG. The high level is set, and the timer signal Tm is 1. In response to this, as shown in FIG. 6C, the electrode negative polarity drive signal Nd becomes the High level, the electrode negative polarity transistor NTR is turned on, and the electrode is switched to the electrode negative polarity EN. At the same time, as shown in FIG. 3D, the electrode positive polarity drive signal Pd becomes the Low level, and the electrode positive polarity transistor PTR becomes the off state. At time t4, as shown in FIG. (E), the current setting signal Ir switches from 0 to the electrode negative polarity current amplitude setting signal Inr. As shown in FIG. 3A, the welding current Iw instantaneously changes from a negative polarity switching current value to a positive polarity switching current value. No re-ignition voltage is applied when switching to the negative polarity EN of the electrode. This is because arc breakage hardly occurs during the electrode negative polarity period Ten.

During the period from time t4 to t5, as shown in FIG. 6A, the welding current Iw increases with an inclination from the polarity switching current value to the value of the electrode negative polarity current amplitude setting signal Inr. This inclination is also determined by the inductance value of the reactor WL and the welded cable. During the period of time t5 to t6, as shown in FIG. 6A, the welding current Iw becomes the value of the electrode negative polarity current amplitude setting signal Inr.

At time t6, when the elapsed time from time t4 reaches the value of the electrode negative polarity period setting signal Tnr, the timer signal Tm becomes 2, and as shown in FIG. .. In response to this, as shown in FIG. 3A, the welding current Iw decreases with an inclination. This inclination is also determined by the inductance value of the reactor WL and the welded cable. Then, at time t7, when the value of the welding current Iw becomes equal to or less than the polarity switching current value, the current comparison signal Cm becomes the High level for a short time as shown in FIG.

At time t7, as shown in FIG. 6B, when the current comparison signal Cm reaches the High level for a short time, the timer signal Tm becomes 3, and as shown in FIG. The Pd becomes the High level, the electrode positive polarity transistor PTR is turned on, and the electrode positive polarity EP is switched to. At the same time, as shown in FIG. 6C, the electrode negative polarity drive signal Nd becomes the Low level, and the electrode negative polarity transistor NTR is turned off. At time t7, as shown in FIG. 6E, the current setting signal Ir switches from 0 to the positive electrode positive polarity current amplitude setting signal Ipr. As shown in FIG. 3A, the welding current Iw instantaneously changes from a positive polarity switching current value to a negative polarity switching current value. At the same time, a re-ignition voltage is applied between the electrode 1 and the base metal 2.

However, immediately after switching to the electrode positive polarity period Tep, the arc generation state becomes a precursor state of arc breakage. Therefore, as shown in FIG. 6A, the absolute value of the welding current Iw is less than the reference current value It. Then, at time t8, the welding current Iw having an average welding current value of 100 A or more, being in the electrode positive polarity period Tep, being in an arc generation state, and being less than the reference current value It is during the predetermined period. As shown in FIG. 3F, the arc break sign detection signal Zd changes to the High level for a short time due to the energization. In response to this, the timer signal Tm is forcibly changed from 3 to 1, so that the electrode is switched to the negative polarity period Ten. The operation after that is the same as the operation from time t4. Even if the arc is in a precursory state during the electrode positive polarity period Tep, it is possible to shift to a stable arc generation state by switching to the electrode negative polarity period Ten. As a result, the occurrence of arc breakage can be suppressed.

The precursory state of arc breakage is a state in which the cathode point of the arc is not formed in the portion of the base material surface with the oxide film, but is formed in the bead portion without the oxide film. Such a state is likely to occur when the average welding current value is 100 A or more and the bead width is a predetermined value or more. In such a state, since a large amount of energy is required to maintain the cathode point, the welding current Iw of the set value cannot be energized, and the value becomes less than the reference current value It.

Most of the time when the re-ignition voltage is being applied, the state of precursor of arc breakage occurs. During the electrode positive polarity period Tep after the application of the re-ignition voltage is completed, it is unlikely that the arc will be cut off. Therefore, the detection of the precursory state of arc breakage may be limited to the application of the re-ignition voltage. In this way, it is possible to prevent erroneous detection of a precursory state of arc breakage.

In FIG. 2, the case where the current waveform is a non-equilibrium waveform is illustrated, but the same applies to the case where the current waveform is an equilibrium waveform in which Inr = Ipr. Further, the current waveform may be a sine wave.

According to the invention of the first embodiment described above, when the sign state of arc breakage is detected during the electrode positive polarity period when the average welding current value is 100 A or more, the electrode positive polarity period ends rather than ending. Switch to the electrode negative polarity period before. Therefore, the occurrence of arc breakage can be suppressed. The detection of the precursory state of arc breakage is detected by the state in which an arc is generated and the welding current (absolute value) less than a predetermined reference current value is energized.

Further, the detection of the precursor state of the arc breakage may be performed during the period when the re-ignition voltage is applied. In this way, in addition to the above-mentioned effects, it is possible to prevent erroneous detection of a precursory state of arc breakage.

1 Electrode 2 Base material 3 Arc 4 Welding torch AD Arc discrimination circuit Ad Arc discrimination signal CM Current comparison circuit Cm Current comparison signal D2a to D2d Secondary rectifier DV Secondary side drive circuit EI Current error amplification circuit Ei Current error amplification signal EN electrode Negative Polar EP Electrode Positive IAD Average Welding Current Detection Circuit Iad Average Welding Current Detection Signal ID Current Detection Circuit Id Current Detection Signal Ien Electrode Negative Current Iep Electrode Positive Current INR Electrode Negative Current Oscillation Setting Circuit Inr Electrode Setting signal INT Inverter transformer INV Inverter circuit IPR Electrode positive polarity current amplitude Setting circuit Ipr Electrode positive polarity current amplitude Setting signal Ir Current setting signal It Reference current value Iw Welding current Nd Electrode Negative polarity Drive signal NTR Electrode Negative polarity transistor Pd Electrode positive polarity Drive signal PTR Electrode positive polarity transistor SD Re-ignition voltage application circuit SW Switching circuit Ten Electrode Negative polarity period Tep Electrode positive polarity period TM Timer circuit Tm Timer signal TNR Electrode Negative polarity period setting circuit Tnr Electrode Negative polarity period setting signal TPR Electrode plus Polarity period setting circuit Tpr Electrode positive Polarity period setting signal Vw Welding voltage WL Reactor ZD Arc break sign detection circuit Zd Arc break sign detection signal

Claims (3)

In the AC non-consumable electrode arc welding control method in which the electrode negative polarity period and the electrode positive polarity period are alternately repeated and a re-ignition voltage is applied at the time of switching to the electrode positive polarity period for welding.
When the average welding current value is 100 A or more and a precursory state of arc breakage is detected during the electrode positive polarity period, the electrode is switched to the electrode negative polarity period before the end of the electrode positive polarity period.
An AC non-consumable electrode arc welding control method characterized by this. The detection of the precursor state of the arc breakage is performed by the state in which the arc is generated and the welding current (absolute value) less than the predetermined reference current value is energized.
The AC non-consumable electrode arc welding control method according to claim 1. The detection of the precursory state of arc breakage is performed during the period in which the re-ignition voltage is applied.
The AC non-consumable electrode arc welding control method according to claim 1 or 2.

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