KR102473580B1 - Direct and inverse feeding ac arc welding method - Google Patents

Abstract

In the normal/reverse supply alternating current arc welding method, the unstable welding state is suppressed by switching the electrode polarity.
Electrode polarity Switching of Spn is set during the period where the supply speed Fw during the normal supply period is decelerating. Thereby, since electrode polarity Spn is switched in the constant phase of supply speed|rate Fw and the molten state at the time of switching becomes constant, a welding state is stabilized.

Description

Direct and reverse feeding alternating current arc welding method {DIRECT AND INVERSE FEEDING AC ARC WELDING METHOD}

The present invention relates to a normal and reverse feeding alternating current arc welding method in which welding is performed by alternately switching the feeding speed of a welding wire between forward feeding period and reverse feeding period, and alternately switching electrode polarity to electrode positive polarity and electrode negative polarity.

In general consumable electrode type arc welding, welding is performed by supplying a welding wire serving as a consumable electrode at a constant speed and generating an arc between the welding wire and a base material. In consumable electrode type arc welding, a welding wire and a base material are often in a welding state in which a short circuit period and an arc period are alternately repeated.

In order to further improve the welding quality, a method of welding by periodically repeating forward feed and back feed of the welding wire has been proposed (for example, see Patent Document 1 and the like).

In the invention of Patent Literature 1, the average value of the supply speed according to the welding current setting value is taken, and the frequency and amplitude of the forward feeding and back feeding of the welding wire are made the values according to the welding current setting value.

In addition, the invention of Patent Literature 2 describes an alternating arc welding method in which a welding wire (electrode) is fed and the electrode polarity is alternately switched to an electrode positive polarity and an electrode negative polarity for welding.

Japanese Patent No. 5201266 Japanese Patent No. 5090765

In the forward and reverse feed AC arc welding method in which the feeding speed of the welding wire is alternately switched to forward feed period and reverse feed period, and electrode polarity is alternately switched to electrode plus polarity and electrode minus polarity to weld, feeding at the time of switching electrode polarity Since the direction and value of the speed fluctuate for each changeover, there has been a problem that the welding state becomes unstable.

Accordingly, an object of the present invention is to provide a normal/reverse supply alternating current arc welding method capable of stabilizing the welding state at the time of electrode polarity switching.

In order to solve the above problems, the invention of claim 1,

In the forward and reverse feeding alternating current arc welding method in which the feeding speed of the welding wire is alternately switched to a forward feeding period and a reverse feeding period, and the electrode polarity is alternately switched to an electrode positive polarity and an electrode negative polarity for welding,

Switching the electrode polarity is performed when the supply speed is a specific phase,

It is a forward and reverse feeding alternating current arc welding method characterized in that.

The invention of claim 2 is the forward and reverse supply alternating current arc welding method according to claim 1, characterized in that the specific phase is set during a period in which the supply speed is decelerating during the normal supply period.

The invention of claim 3 is the forward and reverse supply alternating current arc welding method according to claim 1, wherein the specific phase is set to a phase at which the supply speed starts to decelerate during the feeding period.

The invention of claim 4 is the forward and reverse supply alternating current arc welding method according to claim 1, characterized in that the specific phase is set to a phase at which the supply speed during the feeding period ends deceleration.

According to the present invention, the switching timing of the electrode polarity is performed at a constant phase of the supply speed. For this reason, in the present invention, the welding state at the time of switching the electrode polarity can be stabilized.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a welding apparatus for carrying out a forward and reverse feed alternating current arc welding method according to Embodiment 1 of the present invention.
Fig. 2 is a timing chart of each signal in the welding apparatus of Fig. 1 showing a forward and reverse supply alternating current arc welding method according to Embodiment 1 of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

[Embodiment 1]

1 is a block diagram of a welding apparatus for carrying out a forward and reverse feed alternating current arc welding method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG. 1 .

The inverter circuit INV receives an AC commercial power supply (not shown) such as 3-phase 200V as an input, rectifies and smooths the AC commercial power supply to generate a DC voltage, and generates a DC voltage according to a drive signal Dv described later. Inverter control outputs high-frequency alternating current.

The high frequency transformer INT converts the high frequency alternating current into a voltage value suitable for welding. The secondary rectifier group D2 rectifies the converted high-frequency alternating current and outputs positive and negative DC voltages.

The output polarity of the welding device is switched by on/off controlling the electrode positive polarity switching element PTR and the electrode negative polarity switching element NTR. When the electrode positive polarity switching element PTR is in an on state, the electrode becomes positive polarity (EP), and when the electrode negative polarity switching element NTR is in an on state, the electrode becomes negative polarity (EN). Reactor WL smoothes the output.

Feeding motor WM takes as an input the feeding control signal Fc mentioned later, and feeds the welding wire 1 at feeding speed Fw by repeating forward feeding and backfeeding periodically. A motor with a fast transient response is used for the supply motor WM. In order to accelerate the change rate of the supply speed Fw of the welding wire 1 and the reversal of the supply direction, the supply motor WM may be installed near the tip part of the welding torch 4. In addition, there is a case where two supply motors WM are used to make a supply system of a push-pull system.

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

The polarity switching signal generation circuit (SPN) takes the polarity switching signal Spn described later and the supply speed setting signal Fr described later as inputs, and after a first predetermined period has elapsed from the time when the polarity switching signal Spn changes to the High level, The time when the supply speed setting signal Fr is changed to the low level at the time when the supply speed setting signal Fr is in a specific phase, and the time when the supply speed setting signal Fr is in the specific phase after the second predetermined period has elapsed from the time when the polarity switching signal Spn is changed to the low level Outputs the polarity conversion signal Spn that changes from to high level. As a specific phase of supply speed setting signal Fr, one is selected and set from the following three. The specific phase at the time of changing the polarity switching signal Spn to the low level and the specific phase at the time of changing to the high level may be set to different phases.

1) The specific phase is set during the period during which the supply speed setting signal Fr during the normal supply period is decelerating. That is, it sets during the period which is Fr≥0 and the differential value dFr/dt<0 of supply speed setting signal Fr.

2) A specific phase is set to the phase at which the supply speed setting signal Fr during the feeding period starts deceleration. That is, it is set to a phase where Fr ≥ 0 and dFr/dt first becomes a negative value.

3) The specific phase is set to the phase at which the supply speed setting signal Fr during the feeding period ends deceleration. That is, the phase is set so that Fr = 0 and dFr/dt < 0.

The electrode plus polarity switching element driving circuit EPD outputs the electrode plus polarity switching element driving signal Epd when the polarity switching signal Spn is at a high level. The negative electrode polarity switching element driving circuit END outputs the negative electrode polarity switching element driving signal End when the above polarity switching signal Spn is at a Low level. Therefore, when the polarity switching signal Spn is at a high level, the electrode has a positive polarity (EP), and at a low level, the electrode has a negative polarity (EN).

The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The output voltage detection circuit ED detects the AC voltage (output voltage E) of the secondary output of the high frequency transformer INT described above, converts it into an absolute value, smooths it, and outputs the output voltage detection signal Ed.

The voltage error amplification circuit EA amplifies the error between the output voltage setting signal Er and the output voltage detection signal Ed, and outputs a voltage error amplification signal Ea. With this circuit, the welding device has constant voltage characteristics. The drive circuit DV receives the voltage error amplified signal Ea as an input, performs PWM modulation control based on the voltage error amplified signal Ea, and outputs a drive signal Dv for driving the inverter circuit INV described above. .

The average supply speed setting circuit FAR outputs the average supply speed setting signal Far determined beforehand.

The amplitude setting circuit WFR outputs a predetermined amplitude setting signal Wfr. The frequency setting circuit SFR outputs a predetermined frequency setting signal Sfr.

The feed rate setting circuit FR takes the above average feed rate setting signal Far, the above amplitude setting signal Wfr and the above frequency setting signal Sfr as inputs, and the amplitude and frequency setting signal Sfr determined by the amplitude setting signal Wfr. A predetermined trapezoidal wave that changes to a positive or negative shape at a period determined by the period setting value, which is the reciprocal of , by a value where the average supply speed Fa per cycle becomes equal to the average supply speed setting signal Far. It becomes a waveform shifted to the forward delivery side, Supply speed setting signal Fr is output. About this supply speed setting signal Fr, it demonstrates in detail with FIG. The waveform of the supply speed setting signal Fr may be a sinusoidal wave or a triangular wave other than a trapezoidal wave.

The supply control circuit FC takes the above supply speed setting signal Fr as an input and supplies the supply control signal Fc for supplying the welding wire 1 at the supply speed Fw corresponding to the value of the supply speed setting signal Fr as described above. Output to the supply motor (WM).

FIG. 2 is a timing chart of each signal in the welding apparatus of FIG. 1 showing the forward and reverse supply alternating current arc welding method according to Embodiment 1 of the present invention. 2(A) shows the time change of the supply speed Fw, FIG. 2(B) shows the time change of the welding current Iw, FIG. 2(C) shows the time change of the welding voltage Vw, FIG. (D) in Figure 2 shows the time change of the polarity switching signal Spn. Hereinafter, the operation of each signal will be described with reference to FIG. 2 .

As shown in (D) of FIG. 2 , the polarity switching signal Spn is at a low level (electrode minus polarity (EN)) during the period before time t17, and at a high level (electrode plus polarity (electrode plus polarity (electrode plus polarity)) during the period from time t17 to t37. EP)), the low level (electrode minus polarity (EN)) during the period from time t37 to t57, and the high level (electrode plus polarity (EP)) during the period after time t57. The polarity switching signal Spn is repeated from time t17 to t57 as one cycle.

Supply speed Fw shown in FIG.2(A) is controlled by the value of supply speed setting signal Fr output from supply speed setting circuit FR of FIG. The supply speed setting signal Fr supplies a predetermined trapezoidal wave that changes to a positive or negative shape at a period equal to the reciprocal of the amplitude Wf determined by the amplitude setting signal Wfr and the frequency Sf determined by the frequency setting signal Sfr, as an average supply every cycle. It becomes the waveform shifted to the forward delivery side by the value which the speed Fa becomes equal to the average supply speed setting signal Far which determined beforehand. For this reason, as shown by the broken line of FIG. 2(A), average supply speed|rate Fa becomes equal also during an electrode positive polarity period and an electrode negative polarity period.

As shown in (A) of FIG. 2, as for the supply speed|rate Fw, time t1-t2, time t2-t3, time t3-t4, time t4-t5, and time t5-t6 become one cycle, respectively.

As shown in FIG. 2 (A), the supply speed Fw is formed by the backfeeding acceleration period, the backfeeding peak period, the backfeeding peak value, and the backfeeding deceleration period, respectively, in the backfeeding period from time t1 to t14, and from time t14 to The feeding period of t2 is formed by a feeding feeding acceleration period, a feeding peak period, a feeding feeding peak value, and a feeding feeding deceleration period, respectively. As shown in (D) of FIG. 2, since the polarity switching signal Spn is at a Low level before time t17, it becomes a negative electrode polarity (EN). For this reason, the welding current Iw shown in FIG. 2(B) and the welding voltage Vw shown in FIG. 2(C) become negative values. At time t17, the polarity switching signal Spn changes to the High level, so that the electrode has a positive polarity (EP). For this reason, the welding current Iw and the welding voltage Vw become positive values. That is, at time t17, the electrode polarity is switched from the negative electrode polarity (EN) to the positive electrode polarity (EP).

[Operation during the backfeeding period from time t1 to t14]

As shown in (A) of FIG. 2, supply speed Fw enters into the backfeed acceleration period of time t1 - t11, and accelerates from 0 to the backfeed peak value mentioned above. During this period, the short-circuit state continues. This period is electrode minus polarity (EN), Iw≤0 and Vw≤0.

If the backfeeding acceleration period ends in time t11, as shown in (A) of FIG. 2, supply speed Fw will enter the backfeeding peak period of time t11 - t13, and will become the said backfeeding peak value. At time t12 during this period, an arc is generated by backfeeding and pinch force by energization of the welding current Iw. In response to this, as shown in Fig. 2(C), the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts, and as shown in Fig. 2(B), the welding current Iw increases during the subsequent arc period. gradually decreases during Since this period is the electrode minus polarity (EN), Iw≤0 and Vw≤0.

When the backfeeding peak period ends at time t13, as shown in FIG. During this period, the arc period continues. Since this period is the electrode minus polarity (EN), Iw≤0 and Vw≤0.

[Operation during forwarding period from time t14 to t2]

As shown in (A) of FIG. 2, supply speed Fw enters into the feeding acceleration period of time t14 - t15, and accelerates from 0 to the feeding peak value mentioned above. During this period, it remains the same as the arc period. Since this period is the electrode minus polarity (EN), Iw≤0 and Vw≤0.

When the feeding acceleration period ends at time t15, as shown in Fig. 2(A), the feeding speed Fw enters the feeding peak period of time t15 to t17, and becomes the feeding peak value described above. At time t16 during this period, a short circuit occurs due to forwarding. In response to this, as shown in Fig. 2(C), the welding voltage Vw rapidly decreases to a short-circuit voltage value of several V, and as shown in Fig. 2(B), the welding current Iw decreases during the subsequent short-circuit period. gradually increases during Since this period is the electrode minus polarity (EN), Iw≤0 and Vw≤0.

When the feeding peak period ends at time t17, as shown in FIG. 2(A), the feeding deceleration period starts from time t17 to t2, and the feed rate is decelerated from the above-described peak feeding value to 0. During this period, the short-circuit period continues. Moreover, in time t15, although the period in which polarity switching signal Spn is Low level becomes equal to the 2nd period which determined beforehand, Low level is maintained until supply speed|rate Fw becomes a specific phase. Here, the specific phase of supply speed Fw is set during the normal feed deceleration period of time t17 - t2. In FIG. 2, it is a case where the specific phase is set to the start time point of the forward speed deceleration period of time t17. At time t17, polarity switching signal Spn switches from Low level to High level since the period in which polarity switching signal Spn is Low level becomes more than the 2nd period and supply speed Fw became a specific phase. Accompanying this, the electrode polarity is switched from the electrode minus polarity (EN) to the electrode plus polarity (EP). Therefore, during this period, Iw≥0 and Vw≥0.

During the period from time t2 to t3, the operations of the backfeeding period and the forwarding period described above are repeated. However, since the polarity switching signal Spn is at a high level, it becomes electrode positive polarity (EP). This makes Iw≥0 and Vw≥0.

As shown in (A) of FIG. 2, at the start time point t34 of the feeding acceleration period during the period of time t3 to t4 of the supply speed Fw, the period (time t17 to t34) in which the polarity switching signal Spn is at the High level is predetermined It becomes equivalent to the first period. However, the supply speed Fw maintains the High level until the starting point in time t37 of the normal feeding deceleration period in which it becomes a specific phase. As shown in (D) of FIG. 2 , at time t37, the period in which the polarity switching signal Spn is at the High level is longer than the first period, and the supply speed Fw is in a specific phase, so the polarity switching signal Spn is at the High level to low level. Accompanying this, the electrode polarity is switched from electrode plus polarity (EP) to electrode minus polarity (EN). Therefore, during the transition period of time t37, Iw≤0 and Vw≤0.

As shown in (A) of FIG. 2 , at the start time point t55 of the feeding peak period in the period of time t5 to t6 of the supply speed Fw, the period (time t37 to t55) in which the polarity switching signal Spn is at the Low level is as described above equal to the second period. However, the supply speed Fw maintains the Low level until the start time point t57 of the normal feeding deceleration period used as a specific phase. As shown in (D) of FIG. 2 , at time t57, the period in which the polarity switching signal Spn is at the Low level is longer than the second period, and the supply speed Fw is at a specific phase, so the polarity switching signal Spn is at the Low level to High level. Accompanying this, the electrode polarity is switched from the electrode minus polarity (EN) to the electrode plus polarity (EP). Therefore, during the transition period of time t57, Iw≥0 and Vw≥0.

In the period after this, the above operation is repeated.

The numerical example of the trapezoidal wave of supply speed Fw is shown below. It is frequency Sf=100 Hz of supply speed Fw, and amplitude Wf=60 m/min. In addition, the switching frequency of the polarity switching signal Spn is 25 Hz (period is 40 ms).

The switching frequency of the polarity switching signal Spn described above is set to a value smaller than the frequency of the supply speed Fw, and the setting range is about 50 Hz or less. The setting range of the frequency of supply speed is about 60-150 Hz.

According to the experiment of the inventors, it was confirmed that the welding state was stabilized by performing the switching timing to the electrode positive polarity (EP) and the switching timing to the electrode negative polarity (EN) at a constant phase of the supply speed Fw, respectively. The reason is that, when the phase of the supply speed Fw in the switching timing of the electrode polarity is not constant, various molten states in the switching timing of the electrode polarity are mixed, and the welding state has become unstable. On the other hand, when electrode polarity is switched in the fixed phase of supply speed|rate Fw, the molten state at the time of switching will become constant and a welding state will become stabilized. In addition, the inventors experimented with which period of the reverse feeding acceleration period, the backfeeding peak period, the backfeeding deceleration period, the forward feeding acceleration period, the forward feeding peak period, or the forward feeding deceleration period would further stabilize the welding state when the electrode polarity switching timing was performed. As a result, it was confirmed that the welding state was further stabilized by performing the switching timing of the electrode polarity at a specific phase during the feeding deceleration period.

According to Embodiment 1 mentioned above, switching of an electrode polarity is performed when supply speed is a specific phase. Preferably, as a specific phase, it is set during the period in which the supply speed during the normal supply period is decelerating. Moreover, preferably, as a specific phase, the supply speed during the feeding period is set to a phase in which deceleration starts. Moreover, preferably, as a specific phase, the supply speed during the feeding period is set to a phase at which deceleration is completed. Thereby, in this embodiment, the switching timing of an electrode polarity is performed with the constant phase of supply speed|rate. For this reason, in this embodiment, the welding state at the time of switching of electrode polarity can be stabilized.

1: welding wire
2: parent material
3 : arc
4 : welding torch
5: feeding roll
D2: secondary rectifier group
DV: drive circuit
Dv: driving signal
E: output voltage
EA: voltage error amplifier circuit
Ea: voltage error amplification signal
ED: output voltage detection circuit
Ed: output voltage detection signal
EN: electrode minus polarity
END: electrode minus polarity switching element driving circuit
End: Electrode minus polarity switching element driving signal
EP: electrode plus polarity
EPD: electrode plus polarity switching element drive circuit
Epd: electrode plus polarity switching element driving signal
ER: output voltage setting circuit
Er: output voltage setting signal
Fa: average feed rate
FAR: average feed rate setting circuit
Far: Signal to set the average delivery speed
FC: feeding control circuit
Fc: feeding control signal
FR: feeding speed setting circuit
Fr: feeding speed setting signal
Fw: feeding speed
INT: high frequency transformer
INV: inverter circuit
Iw: welding current
NTR: electrode minus polarity switching element
PTR: electrode plus polarity switching element
Sf: frequency of feed rate
SFR: frequency setting circuit
Sfr: frequency setting signal
SPN: Polarity switching signal generation circuit
Spn: polarity conversion signal
Vw: welding voltage
Wf: Amplitude of feeding speed
WFR: amplitude setting circuit
Wfr: amplitude setting signal
WL: Reactor
WM: feeding motor

Claims (4)

In the forward and reverse feeding alternating current arc welding method in which the feeding speed of the welding wire is alternately switched to a forward feeding period and a reverse feeding period, and the electrode polarity is alternately switched to an electrode positive polarity and an electrode negative polarity for welding,
Switching the electrode polarity is performed when the supply speed is a specific phase,
The forward and reverse supply alternating current arc welding method characterized in that the specific phase is set during a period in which the supply speed is decelerating during the normal supply period. delete delete In the forward and reverse feeding alternating current arc welding method in which the feeding speed of the welding wire is alternately switched to a forward feeding period and a reverse feeding period, and the electrode polarity is alternately switched to an electrode positive polarity and an electrode negative polarity for welding,
Switching the electrode polarity is performed when the supply speed is a specific phase,
The normal/reverse supply alternating current arc welding method characterized by setting the specific phase to a phase at which the supply speed during the feeding period ends deceleration.

Images