JP6593919B2 - Forward / reverse feed AC arc welding method - Google Patents

Description

  The present invention switches the welding wire feeding speed alternately between the forward feeding period and the reverse feeding period, and switches the voltage applied to the arc alternately between the electrode positive polarity and the electrode negative polarity to perform the forward / reverse feeding AC. The present invention relates to an arc welding method.

  In general consumable electrode arc welding, a welding wire that is a consumable electrode is fed at a constant speed, and an arc is generated between the welding wire and a base material to perform welding. In the consumable electrode type arc welding, the welding wire and the 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 has been proposed in which welding is performed by periodically repeating forward and backward feeding of the welding wire (see, for example, Patent Document 1).

  In invention of patent document 1, it is set as the average value of the feeding speed according to the welding current setting value, and the frequency and amplitude of the forward feed and the reverse feeding of the welding wire are values according to the welding current setting value.

  The invention of Patent Document 2 describes an AC arc welding method in which a welding wire is fed and welding is performed by alternately switching the voltage applied to the arc between an electrode positive polarity and an electrode negative polarity.

Japanese Patent No. 52012266 Japanese Patent No. 5090765

  In the forward / reverse feed AC arc welding method in which the welding wire feed speed is alternately switched between the forward feed period and the reverse feed period, and the voltage applied to the arc is switched alternately between the positive electrode polarity and the negative electrode polarity. There is a problem that the welded state becomes unstable because the molten state changes between when the electrode is positive and when the electrode is negative.

  Accordingly, an object of the present invention is to provide a forward / reverse feed AC arc welding method capable of maintaining a stable welding state even when the electrode positive polarity and the electrode negative polarity are alternately switched.

In order to solve the above-described problems, the invention of claim 1
In the forward / reverse feed AC arc welding method in which the welding wire feeding speed is alternately switched between the forward feeding period and the reverse feeding period, and the voltage applied to the arc is switched alternately between the positive electrode polarity and the negative electrode polarity. ,
The waveform parameter of the feed speed is automatically switched in conjunction with the switching between the electrode positive polarity and the electrode negative polarity ,
The waveform parameter is amplitude and / or frequency ;
When the electrode is negative polarity, the amplitude is larger than when the electrode is positive polarity, and the frequency is higher.
This is a forward / reverse feed AC arc welding method.

The invention of claim 4
The waveform parameter is switched so that the average value of the feeding speed when the electrode is positive polarity and the average value of the feeding speed when the electrode is negative polarity are equal.
The forward / reverse feed AC arc welding method according to claim 1 .

  According to the present invention, even if the electrode polarity is switched and the molten state is changed, the waveform parameter of the feeding speed adapted to the changed molten state is switched, so that the welding state is prevented from becoming unstable. Can do. For this reason, in the present invention, the welding state can be kept stable even when the electrode positive polarity and the electrode negative polarity are alternately switched.

It is a block diagram of the welding apparatus for enforcing the forward / reverse feeding AC arc welding method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding apparatus of FIG. 1 which shows the forward / reverse feed AC arc welding method according to Embodiment 1 of the present 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 apparatus for carrying out a forward / reverse feed AC arc welding method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The inverter circuit INV receives an AC commercial power supply (not shown) such as a three-phase 200V as an input, rectifies and smoothes the AC commercial power supply, generates a DC voltage, and controls this DC voltage according to a drive signal Dv described later. And 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 AC and outputs positive and negative DC voltages.

  The output polarity of the welding apparatus is switched by controlling on / off of 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 the on state, the electrode has a positive polarity EP, and when the electrode negative polarity switching element NTR is in the on state, the electrode has a negative polarity EN. The reactor WL smoothes the output.

  The feed motor WM receives a feed control signal Fc described later, and feeds the welding wire 1 at a feed speed Fw by periodically repeating forward feed and reverse feed. A motor with fast transient response is used as the feed motor WM. In order to increase the rate of change of the feeding speed Fw of the welding wire 1 and the reversal of the feeding direction, the feeding motor WM may be installed near the tip of the welding torch 4. In some cases, two feed motors WM are used to form a push-pull feed system.

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

  The polarity switching signal generation circuit SPN outputs a polarity switching signal Spn that is at a high level during a predetermined electrode plus polarity period and is at a low level during a predetermined electrode minus polarity period. The electrode positive polarity switching element drive circuit EPD outputs an electrode positive polarity switching element drive signal Epd when the polarity switching signal Spn is at a high level. The electrode negative polarity switching element drive circuit END outputs an electrode negative polarity switching element drive signal End when the polarity switching signal Spn is at a low level. Accordingly, when the polarity switching signal Spn is at a high level, the electrode has a positive polarity EP, and when it is 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 secondary output AC voltage (output voltage E) of the high-frequency transformer INT, converts it to an absolute value, smoothes it, and outputs an output voltage detection signal Ed.

  The voltage error amplification circuit EA amplifies an 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 apparatus has constant voltage characteristics. The drive circuit DV receives the voltage error amplification signal Ea, performs PWM modulation control based on the voltage error amplification signal Ea, and outputs a drive signal Dv for driving the inverter circuit INV.

  The average feed speed setting circuit FAR outputs a predetermined average feed speed setting signal Far.

  The amplitude setting circuit WFR receives the above polarity switching signal Spn, and when the polarity switching signal Spn is at a high level (EP polarity), it has a predetermined electrode positive polarity period amplitude Wfp, and the polarity switching signal Spn is at a low level (EN (Polarity), an amplitude setting signal Wfr having a predetermined electrode minus polarity period amplitude Wfn is output. For example, Wfn = a · Wfp is set. a is a constant, and a> 1.0. For example, a = 1.2. Therefore, Wfn> Wfp.

  The frequency setting circuit SFR receives the above-described polarity switching signal Spn, and when the polarity switching signal Spn is at a high level (EP polarity), the frequency setting circuit SFR has a predetermined electrode plus polarity period frequency Sfp and the polarity switching signal Spn is at a low level (EN (Polarity), a frequency setting signal Sfr having a predetermined electrode minus polarity period frequency Sfn is output. For example, Sfn = b · Sfp is set. b is a constant, and b> 1.0. For example, b = 1.1. Therefore, Sfn> Sfp.

  The feed speed setting circuit FR receives the average feed speed setting signal Far, the amplitude setting signal Wfr, and the frequency setting signal Sfr, and receives the amplitude determined by the amplitude setting signal Wfr and the reciprocal of the frequency setting signal Sfr. A predetermined trapezoidal wave that changes into a positive and negative shape with a period determined by a certain period setting value is a waveform in which the average feeding speed Fa for each period is shifted to the positive feeding side by a value equal to the average feeding speed setting signal Far. The feed speed setting signal Fr is output. The feed speed setting signal Fr will be described in detail with reference to FIG. The waveform of the feed speed setting signal Fr may be a sine wave or a triangular wave in addition to the trapezoidal wave.

  The feed control circuit FC receives the feed speed setting signal Fr and receives a feed control signal Fc for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr. It outputs to said feed motor WM.

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

  As shown in FIG. 4D, the polarity switching signal Spn becomes High level during the predetermined period from time t1 to t3 and becomes the electrode positive polarity EP, and becomes Low level during the predetermined period from time t3 to t5. Electrode negative polarity EN. The polarity switching signal Spn is repeated with time t1 to t5 as one cycle.

  The feed speed Fw shown in FIG. 6A is controlled to the value of the feed speed setting signal Fr output from the feed speed setting circuit FR of FIG. The feed speed setting signal Fr is a predetermined trapezoidal wave that changes into a positive and negative shape with a period that is the reciprocal of the amplitude determined by the amplitude setting signal Wfr and the frequency determined by the frequency setting signal Sfr, and an average feed speed Fa for each cycle. Is a waveform shifted to the forward feed side by a value equal to a predetermined average feed speed setting signal Far. For this reason, as indicated by a broken line in FIG. 5A, the average feed speed Fa is equal during both the electrode positive polarity period and the electrode negative polarity period.

  As shown in FIG. 5A, the feed speed Fw is one period from time t1 to t2, time t2 to t3, time t3 to t4, and time t4 to t5. During the electrode positive polarity period from time t1 to t3, the amplitude of the feed speed Fw is a predetermined electrode plus polarity period amplitude Wfp, and the cycle of the feed speed Fw is the reciprocal of the predetermined electrode plus polarity period frequency Sfp Tfp = 1 / Sfp. During the electrode minus polarity period from time t3 to t5, the amplitude of the feeding speed Fw becomes a predetermined electrode minus polarity period amplitude Wfn, and the cycle of the feeding speed Fw is the reciprocal Tfn = the electrode minus polarity period frequency Sfn. 1 / Sfn. As described above, Wfn> Wfp. Since Sfn> Sfp, Tfn <Tfp. The reason why the amplitude and frequency of the feeding speed are switched depending on the electrode polarity in this way is that the welding state of the welding wire 1 and the base material 2 differs depending on the electrode polarity. For this reason, the welding state becomes unstable unless the amplitude and / or frequency of the feeding speed Fw is made larger during the electrode minus polarity period than during the electrode plus polarity period. In other words, the welding condition is always kept stable by automatically switching the waveform parameter (amplitude, frequency, etc.) of the feed speed FW in conjunction with the switching between the electrode positive polarity EP and the electrode negative polarity EN. Can do.

[Operations during time period t1 to t3 during electrode positive polarity]
As shown in FIG. 4A, the feed speed Fw is formed from a predetermined reverse feed acceleration period, reverse feed peak period, reverse feed peak value, and reverse feed deceleration period in the reverse feed period from time t1 to t14. The normal feed period from time t14 to t2 is formed from a predetermined normal feed acceleration period, a normal feed peak period, a normal feed peak value, and a normal feed deceleration period, respectively. The welding current Iw shown in the figure (B) and the welding voltage Vw shown in the figure (C) are positive values.

[Operation in the reverse feed period from time t1 to t14]
As shown in FIG. 5A, the feed speed Fw enters the reverse feed acceleration period from time t1 to t11, and accelerates from 0 to the reverse feed peak value. During this period, the short-circuit state continues.

  When the reverse acceleration period ends at time t11, as shown in FIG. 5A, the feeding speed Fw enters the reverse peak period at times t11 to t13, and becomes the reverse peak value described above. At time t12 during this period, an arc is generated by the pinch force generated by reverse feeding and energization of the welding current Iw. In response to this, the welding voltage Vw suddenly increases to an arc voltage value of several tens of volts as shown in FIG. 5C, and the welding current Iw is set to the arc period thereafter, as shown in FIG. The inside gradually decreases.

  When the reverse feed peak period ends at time t13, as shown in FIG. 5A, the reverse feed deceleration period starts at times t13 to t14 and decelerates from the reverse feed peak value to zero. During this period, the arc period continues.

[Operation in the forward feed period from time t14 to t2]
As shown in FIG. 5A, the feed speed Fw enters the forward feed acceleration period from time t14 to t15, and accelerates from 0 to the forward feed peak value. During this period, the arc period remains.

  When the forward feed acceleration period ends at time t15, the feed speed Fw enters the forward feed peak period from time t15 to t17, as shown in FIG. At time t16 during this period, a short circuit occurs due to normal feeding. In response to this, the welding voltage Vw rapidly decreases to a short-circuit voltage value of several V as shown in FIG. 5C, and the welding current Iw is maintained during the subsequent short-circuit period as shown in FIG. Gradually increases.

  When the forward feed peak period ends at time t17, as shown in FIG. 5A, the forward feed deceleration period of time t17 to t2 starts, and the forward feed peak value decelerates to zero. During this period, the short circuit period continues.

  During the period from the time t2 to the time t3, the operations of the reverse transmission period and the normal transmission period are repeated.

[Operation during electrode minus polarity period from time t3 to t5]
As shown in FIG. 4A, the feed speed Fw is formed from a predetermined reverse feed acceleration period, reverse feed peak period, reverse feed peak value, and reverse feed deceleration period, respectively, at the times t3 to t34. The forward feed periods from time t34 to t4 are each formed from a predetermined forward feed acceleration period, a forward feed peak period, a forward feed peak value, and a forward feed deceleration period. The welding current Iw shown in the figure (B) and the welding voltage Vw shown in the figure (C) become negative values. That is, at time t3, when the polarity switching signal Spn is switched from the High level to the Low level as shown in FIG. 4D, the welding current Iw is changed from a positive value to a negative value as shown in FIG. The welding voltage Vw is also switched from a positive value to a negative value as shown in FIG. Similarly, the amplitude and frequency of the feeding speed Fw are switched as shown in FIG.

  The operations of the welding current Iw and the welding voltage Vw during the period from the time t3 to the time t5 are different in polarity from those during the period from the time t1 to the time t2 described above, but the operation is substantially the same, so the description will not be repeated.

  A numerical example of the trapezoidal wave of the feeding speed Fw is shown below. The frequency of the feeding speed Fw is Sfp = 100 Hz and Sfn = 110 Hz, and the amplitudes are Sfp = 60 m / min and Sfn = 72 m / min. The electrode polarity switching frequency at this time is about 26 Hz (the cycle is 38 ms), and the electrode positive polarity period is 10 ms and the electrode negative polarity period is about 9 ms.

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

  According to the first embodiment described above, the waveform parameter of the feeding speed is automatically switched in conjunction with the switching between the electrode positive polarity and the electrode negative polarity. The waveform parameter is amplitude and / or frequency. When the electrode is negative polarity, the amplitude is larger and the frequency is higher than when the electrode is positive polarity. As a result, in this embodiment, even if the electrode polarity is switched and the molten state is changed, the waveform parameter of the feeding speed adapted to the changed molten state is switched, so that the welding state is prevented from becoming unstable. can do. For this reason, in this embodiment, the welding state can be kept stable even if the electrode positive polarity and the electrode negative polarity are alternately switched.

  Further, according to the present embodiment, the waveform parameter of the feeding speed is switched so that the average value of the feeding speed when the electrode is positive polarity and the average value of the feeding speed when the electrode is negative polarity are equal. . Thereby, even if the waveform parameter of the feeding speed is switched, the average value of the feeding speed is constant, so that the quality of the weld bead can be improved.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll D2 Secondary rectifier group DV Drive circuit Dv Drive signal E Output voltage EA Voltage error amplification circuit Ea Voltage error amplification signal ED Output voltage detection circuit Ed Output voltage detection signal EN Electrode negative polarity END Electrode negative polarity switching element drive circuit End Electrode negative polarity switching element drive signal EP Electrode positive polarity EPD Electrode positive polarity switching element drive circuit Epd Electrode positive polarity switching element drive signal ER Output voltage setting circuit Er Output voltage setting signal Fa Average feed speed FAR Average feed speed setting circuit Far Average feed speed setting signal FC Feed control circuit Fc Feed control signal FR Feed speed setting circuit Fr Feed speed setting signal FW Feed speed INT High frequency transformer INV Inverter Circuit Iw Welding current NTR Electrode marker Negative polarity switching element PTR Electrode plus polarity switching element Sfn Electrode minus polarity period frequency Sfp Electrode plus polarity period frequency SFR Frequency setting circuit Sfr Frequency setting signal SPN Polarity switching signal generation circuit Spn Polarity switching signal Vw Welding voltage Wfn Electrode minus polarity period amplitude Wfp Electrode plus polarity period amplitude WFR Amplitude setting circuit Wfr Amplitude setting signal WL Reactor WM Feeding motor

Claims (2)

In the forward / reverse feed AC arc welding method in which the welding wire feeding speed is alternately switched between the forward feeding period and the reverse feeding period, and the voltage applied to the arc is switched alternately between the positive electrode polarity and the negative electrode polarity. ,
The waveform parameter of the feed speed is automatically switched in conjunction with the switching between the electrode positive polarity and the electrode negative polarity ,
The waveform parameter is amplitude and / or frequency ;
When the electrode is negative polarity, the amplitude is larger than when the electrode is positive polarity, and the frequency is higher.
A forward / reverse feed AC arc welding method characterized by the above. The waveform parameter is switched so that the average value of the feeding speed when the electrode is positive polarity and the average value of the feeding speed when the electrode is negative polarity are equal.
The forward / reverse feed AC arc welding method according to claim 1 .

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