JP6347721B2 - Arc welding control method - Google Patents

Description

  The present invention relates to an arc welding control method for generating a short circuit period and an arc period by periodically changing a feeding speed between forward feeding and reverse feeding.

  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 reverse feeding of the welding wire. For example, in the invention of Patent Document 1, the average value of the feeding speed according to the welding current setting value is used, and the frequency and amplitude of the forward and reverse feeding of the welding wire are values according to the welding current setting value. In the welding method that repeats forward and reverse feeding of the welding wire, the repetition cycle of short-circuiting and arcing, which was impossible with the conventional technology of constant-speed feeding, can be set to a desired value. It is possible to improve the welding quality such as reducing the number of beads and improving the bead appearance.

Further, in the invention of Patent Document 2, a welding wire is fed at a constant speed, a short-circuiting time rate is used as an index indicating an arc state, and a short-circuiting time rate setting value that is a target value is set according to an average feeding speed. The short circuit time rate during welding is detected, and the output control of the welding power source is performed so that the short circuit time rate detection value becomes equal to the short circuit time rate set value. Here, the short circuit time rate Rs (%) can be calculated by the following equation, where ΣTa (second) is the total time of the arc period occupying the unit time and ΣTs (second) is the total time of the short circuit period.
Rs = (ΣTs / (ΣTa + ΣTs)) × 100 (1) Expression The unit time is, for example, 0.1 second, 1 second, or the like.

Japanese Patent No. 52012266 JP-A-8-155645

  In the arc welding control method of performing welding by performing output control based on the short circuit time rate, even if the average feed speed is the same value, if the welding conditions such as the joint shape, welding speed, welding posture, etc. are different, an appropriate short circuit time rate is obtained. Different. For this reason, it is necessary to change a short circuit time rate setting value to an appropriate value according to welding conditions. However, in welding that repeats forward and reverse feeding speeds periodically, changing the short-circuiting time rate setting value changes the droplet transfer state. A state of synchronization deviation occurs in the cycle, the short-circuit period, and the arc period. As a result, there is a problem that the welding state becomes unstable.

  Therefore, the present invention provides an arc welding control method capable of keeping the welding state stable even in the case where the set value of the short-circuiting time rate is changed in welding in which the feed rate is periodically forwarded and reversely fed. The purpose is to do.

In order to solve the above-described problems, the invention of claim 1
The feed rate is periodically changed between forward feed and reverse feed to generate a short circuit period and an arc period to detect the short circuit time rate during welding, and this short circuit time rate detection value is the short circuit time rate set value. In the arc welding control method of welding by controlling the output of the welding power source to be equal,
Changing the cycle of the feeding speed based on the short circuit time rate setting value;
An arc welding control method characterized by the above.

  According to the present invention, the cycle of the feeding speed is changed based on the short circuit time rate setting value. As a result, the cycle of the feeding speed is optimized in response to the change of the droplet transfer state accompanying the change of the short circuit time rate setting value, so the cycle of the feeding speed forward and reverse feeding and the short circuit period The occurrence of a synchronization deviation between the period of the arc and the arc period can be suppressed. As a result, in the present invention, the welding state can be kept stable even in the case where the short-circuit time rate set value changes in welding in which the feeding speed is periodically forwarded and reversed.

It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding power supply of FIG. 1 which shows the arc welding control method which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply for implementing the arc welding control method which concerns on Embodiment 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
The invention of the first embodiment changes the cycle of the feeding speed based on the short circuit time rate set value.

  FIG. 1 is a block diagram of a welding power source for carrying out an arc welding control method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as a three-phase 200V, performs output control by inverter control or the like according to a drive signal Dv described later, and outputs an output voltage E. Although not shown, the power supply main circuit PM is driven by a primary rectifier that rectifies the commercial power supply, a smoothing capacitor that smoothes the rectified direct current, and the drive signal Dv that converts the smoothed direct current to high-frequency alternating current. An inverter circuit, a high-frequency transformer that steps down the high-frequency alternating current to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency alternating current into direct current.

  The reactor WL smoothes the output voltage E. The inductance value of the reactor WL is, for example, 200 μH.

  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 voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short circuit determination circuit SD receives the voltage detection signal Vd as an input, determines that it is in the short circuit period when this value is less than the short circuit determination value (about 10 V), and is at the high level, and if it is above, it is in the arc period. A short circuit determination signal Sd that is determined to be low level is output.

  The short-circuit time rate detection circuit RSD receives the short-circuit determination signal Sd as an input, and sums a period in which the short-circuit determination signal Sd is at a high level (short circuit) and a period in which it is at a low level (arc) for each unit time. The short circuit time rate is calculated by the equation (1), and the short circuit time rate detection signal Rsd is output.

  The short circuit time rate setting circuit RSR outputs a predetermined short circuit time rate setting signal Rsr. The time rate error amplifying circuit EA receives the short circuit time rate setting signal Rsr and the short circuit time rate detection signal Rsd as inputs, and outputs a short circuit time rate setting signal Rsr (+) and a short circuit time rate detection signal Rsd (−). The error is amplified and a time rate error amplification signal Ea is output. By this circuit, the welding power source is subjected to feedback control (output control) so that the short circuit time rate detection signal Rsd becomes equal to the short circuit time rate setting signal Rsr.

  The output voltage setting circuit ER receives the above time rate error amplification signal Ea, performs integration of Er = Er0 + ∫Ea · dt during welding, and outputs it as an output voltage setting signal Er. Er0 is a predetermined initial value.

  The output voltage detection circuit ED detects and smoothes the output voltage E and outputs an output voltage detection signal Ed.

  The voltage error amplification circuit EV receives the output voltage setting signal Er and the output voltage detection signal Ed, and amplifies an error between the output voltage setting signal Er (+) and the output voltage detection signal Ed (−). The voltage error amplification signal Ev is output. By this circuit, the welding power source is controlled at a constant voltage.

  The drive circuit DV receives the voltage error amplification signal Ev, performs PWM modulation control based on the voltage error amplification signal Ev, and outputs a drive signal Dv for driving the inverter circuit in the power supply main circuit PM. To do.

  The cycle setting circuit TFR calculates a cycle by a predetermined cycle setting function that receives the short-circuit time rate setting signal Rsr and outputs it as the cycle setting signal Tfr. This period setting function is a function in which the value of the period setting signal Tfr decreases as the short-circuiting time ratio setting signal Rsr increases. The period setting function is preset by experiment.

  The amplitude setting circuit WFR outputs a predetermined amplitude setting signal Wfr. The forward feed shift amount setting circuit SFR outputs a predetermined forward feed shift amount setting signal Sfr.

  The feed speed setting circuit FR receives the period setting signal Tfr, the amplitude setting signal Wfr, and the normal transmission side shift amount setting signal Sfr as input, and is determined by the period and amplitude setting signal Wfr determined by the period setting signal Tfr. A feed speed pattern obtained by shifting the sine wave formed from the amplitude by the forward feed side shift amount determined by the forward feed side shift amount setting signal Sfr is output as the feed speed setting signal Fr. When the feed speed setting signal Fr is 0 or more, it is a forward feed period, and when it is less than 0, it is a reverse feed period.

  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 power source of FIG. 1 showing the arc welding control method according to the first embodiment of the present invention. FIG. 4A shows the time change of the feeding speed Fw, FIG. 4B shows the time change of the welding current Iw, FIG. 4C shows the time change of the welding voltage Vw, and FIG. ) Shows a time change of the short-circuit determination signal Sd. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 5A, the feed speed Fw is a forward feed period above 0 and a reverse feed period below. Forward feeding is feeding in the direction in which the welding wire is brought closer to the base material, and reverse feeding is feeding in a direction away from the base material. The feeding speed Fw changes in a sine wave shape and has a waveform shifted to the forward feeding side. For this reason, the average value of the feeding speed Fw is a positive value, and the welding wire is fed forward on average. The feeding speed pattern of the feeding speed Fw may be a triangular wave, a trapezoidal wave, or the like.

  As shown in FIG. 6A, the feeding speed Fw is 0 at time t1, the period from time t1 to t2 is a normal feeding acceleration period, the maximum value of normal feeding at time t2, and the time t2 The period of t3 is a forward feed deceleration period, becomes 0 at time t3, the period of time t3 to t4 is a reverse feed acceleration period, becomes the maximum value of reverse feed at time t4, and the period of time t4 to t5 is a reverse feed deceleration period. It becomes. The period from time t5 to t6 again becomes the normal feed acceleration period, and the period from time t6 to t7 again becomes the normal feed deceleration period. Therefore, the feed speed Fw is the period Tf (ms) from time t1 to t5, the amplitude Wf (m / min) that is the difference between the maximum value of forward feed at time t2 and the maximum value of reverse feed at time t4, and the average. It repeats with the feed speed pattern of the forward feed side shift amount Sf (m / min) that becomes the feed speed.

  As shown in FIG. 4D, the short circuit determination signal Sd is at a low level (arc) before time t21, and is at a high level (short circuit) during a period from time t21 to t31, as described later. During the period of t61, it becomes the Low level (arc), and after the time t61, it becomes the High level (short circuit). The short circuit determination signal Sd is input to the short circuit time rate detection circuit RSD of FIG. 1, and the short circuit time rate detection signal Rsd is output. When the unit time for detecting the short circuit time rate is 0.1 second, the short circuit time rate is detected every 5 to 10 cycles of the feeding speed Fw. Then, the output voltage setting circuit Er of FIG. 1 corrects the output voltage setting signal Er so that the short circuit time rate detection signal Rsd becomes equal to the predetermined short circuit time rate setting signal Rsr. As a result, the welding power source is output-controlled (constant voltage control) so that the output voltage detection signal Ed becomes equal to the output voltage setting signal Er by the voltage error amplification circuit EV of FIG. That is, the output of the welding power source is controlled so that the short circuit time rate detection signal Rsd and the short circuit time rate setting signal Rsr are equal.

  The period Tf is set by the period setting circuit TFR in FIG. 1 and changes in conjunction with the value of the short circuit time rate setting signal Rsr. The amplitude Wf is set to a predetermined value by the amplitude setting circuit WFR in FIG. The forward feed shift amount Sf is set to a predetermined value by the forward feed shift amount setting circuit SFR in FIG. The cycle Tf changes in association with the short circuit time rate setting signal Rsr in the range of about 8 to 20 ms. The amplitude Wf is set to about 30 to 100 m / min, and the forward feed side shift amount Sf is set to about 3 to 20 m / min.

  Short-circuiting between the welding wire and the base material often occurs before and after the maximum normal feed value at time t2. In the figure, the case occurs at time t21 during the forward feed deceleration period after the forward feed maximum value. When a short circuit occurs at time t21, the welding voltage Vw rapidly decreases to a short circuit voltage value of several V as shown in FIG. 10C, and in response to this, as shown in FIG. The signal Sd changes to a high level (short circuit). At the same time, as shown in FIG. 5B, the welding current Iw gradually increases during the short circuit period.

  As shown in FIG. 5A, the feeding speed Fw is in the reverse feed period from time t3, so the welding wire is fed backward. The short circuit is released by the pinch force generated by the reverse feeding and the welding current Iw, and the arc is regenerated at time t31. The reoccurrence of the arc often occurs before and after the maximum reverse feed value at time t4. In the figure, the case occurs at time t31 during the reverse acceleration period before the reverse peak value. Accordingly, the period from time t21 to t31 is a short circuit period, and during this period, as shown in FIG. 4D, the short circuit determination signal Sd is at a high level. The

  When the arc is regenerated at time t31, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts as shown in FIG. 10C, and in response to this, as shown in FIG. The short circuit determination signal Sd changes to the low level (arc). At the same time, as shown in FIG. 5B, the welding current Iw starts to change from the maximum value during the short circuit period.

  During the period from time t31 to t5, as shown in FIG. 5A, since the feed speed Fw is in the reverse feed state, the welding wire is pulled up and the arc length is gradually increased. As the arc length increases, the welding voltage Vw increases and the welding current Iw decreases because constant voltage control is performed by the voltage error amplification circuit EV of FIG. Therefore, during the arc period reverse feed period Tar from time t31 to t5, the welding voltage Vw gradually increases as shown in FIG. 3C, and the welding current Iw gradually decreases as shown in FIG. Become.

  Then, the next short circuit occurs at time t61 during the forward feed deceleration period from time t6 to t7. However, the short circuit that occurred at time t61 is delayed in the time (phase) from the maximum value of the forward feed than the short circuit that occurred at time t21. Thus, the timing at which a short circuit occurs has some variation. The period from time t31 to t61 is an arc period, and during this period, as shown in FIG. 4D, the short circuit determination signal Sd is at a low level. During the period from time t5 to t61, as shown in FIG. 6A, the feed speed Fw is in the normal feed state, so the welding wire is fed forward and the arc length is gradually shortened. When the arc length becomes shorter, the welding voltage Vw becomes smaller, and the welding current Iw becomes larger because the constant voltage control is performed by the voltage error amplification circuit EV of FIG. Therefore, during the arc period normal feed period Tas from time t5 to t61, the welding voltage Vw gradually decreases as shown in FIG. 3C, and the welding current Iw gradually increases as shown in FIG. Become.

  As described above, even if the average feeding speed is the same value, the appropriate short-circuiting time ratio differs if the welding conditions such as the joint shape, welding speed, and welding posture are different. For this reason, it is necessary to change a short circuit time rate setting value to an appropriate value according to welding conditions. However, in welding that periodically repeats forward and reverse feeding speeds, changing the short-circuit time rate setting value changes the output of the welding power source, so the droplet transfer state changes and A state of synchronization deviation occurs in the cycle of forward and reverse speeds, the cycle of the short circuit period, and the cycle of the arc period.

  According to the invention of the first embodiment, when the short circuit time rate setting value (short circuit time rate setting signal Rsr) changes, the cycle of the feeding speed is changed in conjunction with the change. As a result, the cycle of the feeding speed is optimized in response to the change of the droplet transfer state accompanying the change of the short circuit time rate setting value, so the cycle of the feeding speed forward and reverse feeding and the short circuit period The occurrence of a synchronization deviation between the period of the arc and the arc period can be suppressed. As a result, in the present embodiment, the welding state can be kept stable even in the case where the short-circuit time rate setting value changes in welding in which the feeding speed is periodically forwarded and reversely fed.

[Embodiment 2]
The invention of the second embodiment feedback-controls the cycle of the feeding speed so that the short circuit time rate detection value and the short circuit time rate set value are equal.

  FIG. 3 is a block diagram of a welding power source for carrying out the arc welding control method according to the second embodiment of the present invention. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and the description thereof will not be repeated. This figure is obtained by adding a feed error amplifier circuit EF to FIG. 1 and replacing the cycle setting circuit TFR of FIG. 1 with a second cycle setting circuit TFR2. Hereinafter, these blocks will be described with reference to FIG.

  The feed error amplification circuit EF amplifies an error between the short circuit time rate setting signal Rsr (+) and the short circuit time rate detection signal Rsd (−) and outputs a feed error amplification signal Ef. This circuit and the above time rate error amplifier circuit EA have different amplification factors.

  The second cycle setting circuit TFR2 receives the feed error amplification signal Ef, integrates the feed error amplification signal Ef during welding, and outputs a cycle setting signal Tfr. The integral can be expressed as Tfr = Tf0 + ∫Ef · dt. Here, Tf0 is a predetermined initial value. By this circuit, the cycle setting signal Tfr is feedback-controlled so that the short circuit time rate detection signal Rsd becomes equal to the short circuit time rate setting signal Rsr, and changes every moment during welding.

  Since the timing chart of each signal in the welding power source of FIG. 3 showing the arc welding control method according to the second embodiment of the present invention is the same as FIG. 2 described above, description thereof will not be repeated. However, the cycle Tf shown in FIG. 2 is feedback-controlled by the feed error amplifier circuit EF and the second cycle setting circuit TFR2 in FIG. 3 so that the short circuit time rate detection signal Rsd becomes equal to the short circuit time rate setting signal Rsr. The point is different.

  According to the second embodiment, the feed rate cycle is feedback-controlled so that the short circuit time rate detection value and the short circuit time rate set value are equal. As a result, the feed rate cycle is feedback-controlled so that the short circuit time rate detection value becomes equal to the short circuit time rate setting value in response to the change of the droplet transfer state accompanying the change of the short circuit time rate setting value. The state in which the short-circuit time rate detection value is equal to the short-circuit time rate setting value means that there is no synchronization shift between the cycle of the feed speed forward and reverse feeds and the cycle of the short-circuit period and the arc period. The welding state is stable. In the invention of the second embodiment, unlike the invention of the first embodiment, it is not necessary to obtain the period setting function by experiment, so that production preparation can be made efficient. Furthermore, even if the short-circuiting time rate setting value changes under various welding conditions, the feed rate cycle is optimized by feedback control, so that a stable welding state can always be obtained.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll DV Drive circuit Dv Drive signal E Output voltage EA Time rate error amplification circuit Ea Time rate error amplification signal ED Output voltage detection circuit Ed Output voltage detection signal EF Feeding error Amplifier circuit Ef Feed error amplification signal ER Output voltage setting circuit Er Output voltage setting signal EV Voltage error amplifier circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feed control signal FR Feed speed setting circuit Fr Feed speed setting signal Fw Feeding speed Iw Welding current PM Power supply main circuit Rs Short circuit time rate RSD Short circuit time rate detection circuit Rsd Short circuit time rate detection signal RSR Short circuit time rate setting circuit Rsr Short circuit time rate setting signal SD Short circuit determination circuit Sd Short circuit determination signal Sf Positive feed Side shift amount SFR Forward feed side shift amount setting circuit Sfr Forward feed side shift amount setting signal Tar Arc period Reverse feed period Tas Arc period Cycle of feeding period Tf feeding rate TFR period setting circuit Tfr cycle setting signal TFR2 second period setting circuit VD voltage detection circuit Vd voltage detection signal Vw welding voltage Wf amplitude WFR amplitude setting circuit Wfr amplitude setting signal WL reactor WM feed motor

Claims (1)

The feed rate is periodically changed between forward feed and reverse feed to generate a short circuit period and an arc period to detect the short circuit time rate during welding, and this short circuit time rate detection value is the short circuit time rate set value. In the arc welding control method of welding by controlling the output of the welding power source to be equal,
Changing the cycle of the feeding speed based on the short circuit time rate setting value;
An arc welding control method characterized by the above.

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