JP5042527B2 - Welding end control method for consumable electrode arc welding - Google Patents

Description

  The present invention relates to a welding end control method of consumable electrode arc welding for improving the welding quality at the end of welding in consumable electrode arc welding.

  In consumable electrode arc welding such as CO2 welding, MAG welding, and MIG welding, the welding wire is prevented from sticking (sticking) to the molten pool at the end of welding, and the size of the wire tip grain formed at the end of welding is optimized. Then, the welding end control (anti-stick control) for improving the next arc start property is performed. This welding end control is control of a welding current and a welding voltage in an inertia period from when a stop signal is input to the feed motor until the feed motor is decelerated transiently due to inertia and stops. In direct current or alternating current consumable electrode arc welding in which no pulse current is applied, the output is controlled at a constant voltage. Therefore, constant voltage control is generally performed to lower the welding voltage value even during the inertia period. For this reason, the arc burns up, arc breakage occurs, and welding is terminated, so that the wire tip particle size tends to increase. As a conventional technique for improving this, in a consumable electrode arc welding in which no pulse current is passed, a welding end control method is used in which the pulse current is passed during the inertia period to reduce the wire tip particle size. Hereinafter, this prior art will be described.

  FIG. 5 is a waveform diagram showing a welding end control method in which a pulse current is applied during an inertia period in non-pulse consumable electrode arc welding. 3A shows the start signal On, FIG. 1B shows the feeding speed vf, FIG. 1C shows the welding current Iw, and FIG. 3D shows the welding voltage Vw. The start signal On becomes a welding start signal at a high level and becomes a welding end signal at a low level. Hereinafter, a description will be given with reference to FIG.

  During the steady welding period before time t4, the start signal On is at a high level (welding start signal) as shown in FIG. 9A, so the feed speed vf is as shown in FIG. The constant consumable electrode arc welding is performed at a predetermined constant feed rate. During the short-circuit period Ts from time t1 to t2, the welding wire is short-circuited to the molten pool, and the welding current Iw increases as shown in FIG. Vw becomes a low short-circuit voltage value. During the arc period Ta between times t2 and t3, an arc is generated, the welding current Iw decreases as shown in FIG. 5C, and the welding voltage Vw is high as shown in FIG. The voltage rises. During the steady period, the short circuit period Ts and the arc period Ta are repeated.

  At time t4, when the start signal On changes to a low level (welding end signal) as shown in FIG. 9A, a stop signal is input to the feed motor as shown in FIG. The feeding speed vf stops at time t5 after an inertia period Tk. This inertia period Tk is about several hundred ms. In response to the change of the start signal On to the welding end signal at time t4, a pulse current is applied as shown in FIG. 4C, and a pulse voltage is applied as shown in FIG. . As shown in FIG. 5B, around the time t5 when the feed speed vf becomes substantially zero and the feed is stopped, as shown in FIG. The transition is made to reduce the wire tip particle size and the welding is finished. When the wire tip particle size is a desired value rather than too small, the next arc start property may be better. In such a case, a base current for a predetermined period is supplied after the last pulse current Ipe. To form a desired tip grain. Further, although the timing for switching to the pulse current is set from the time when the welding end signal is input in the same figure, there are cases where the feed speed vf is reduced to a predetermined value (for example, substantially zero). The above-described welding end control is particularly effective for MIG welding of stainless steel in which the wire tip particle size tends to be large (see, for example, Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 4-111972 JP-A-9-267171

  As described above, in the prior art, energization of the pulse current starts in synchronization with the switching timing to the pulse current during the inertia period Tk. This switching timing is a predetermined timing such as the start time of the inertia period TK, the time when the feeding speed due to inertia is reduced to a predetermined value, or the like. For this reason, energization of the pulse current is started irrespective of the arc occurrence state at the switching timing. As a result, the following problems occur.

  FIG. 6 is a waveform diagram corresponding to FIG. 5 described above, and FIGS. (F1) to (F3) show arc generation states at each time. The signals in FIGS. 5A to 5D are the same as those in FIG. The figure shows the case where the switching timing is when the activation signal On changes to the low level (welding end signal) and enters the inertia period Tk at time t4.

  Immediately before the time t4, as shown in the figure (F1), the droplet of the welding wire 1 moves to the melted land 2, and as shown in the figure (F2), the short circuit is released and the arc 3 is generated. . Since this short circuit is released and the melted ground 2 is raised, time t4 is reached, so that a pulse current having a large current value is energized as shown in FIG. Due to the strong arc force caused by the large current, a large amount of spatter is generated from the molten pool as shown in FIG.

  FIG. 7 is a waveform diagram corresponding to FIG. 5 described above, and FIGS. (F1) to (F3) show the arc generation state at each time. The signals in FIGS. 9A to 9D are the same as those in FIG. The figure shows the case where the switching timing is when the activation signal On changes to the low level (welding end signal) and enters the inertia period Tk at time t4.

  At time t31, as shown in FIG. 5F1, the short circuit is released and the arc 3 is regenerated. Thereafter, the arc period continues for a long time, and immediately before time t4, as shown in FIG. Since it is time t4 in this state, a large current pulse current is applied as shown in FIG. Due to the strong electromagnetic pinch force caused by the energization of a large current, a large amount of spatter is generated from the droplet as shown in FIG.

  As described above, since the switching timing to the pulse current in the inertia period is irrelevant to the arc state, there is a problem that spatter is generated in the pulse current energization start character and the welding quality is deteriorated.

  Therefore, the present invention provides a welding end control method for consumable electrode arc welding that can suppress a decrease in welding quality at the start of energization of a pulse current in the inertia period.

In order to solve the above-described problem, the first invention is directed to a feeding motor when a welding end signal is input to a welding power source when performing consumable electrode arc welding with a short circuit without applying a pulse current. In response to this stop signal, the feed motor decelerates and stops due to inertia, and during this inertia period, the welding current is switched to a pulse current and energized to finish welding. In the welding end control method,
An average arc time, which is an average value of arc periods between short circuits, is calculated during welding before the welding end signal is input, and the average arc time is determined within a range of 0.3 to 0.7. Multiply the coefficient of to calculate the switching delay time,
The switching to the pulse current is performed at the time when the arc period starts and the switching delay time is reached after a predetermined switching timing has elapsed from the start time of the inertia period. This is an end control method.

  A second invention is a welding end control method of consumable electrode arc welding according to the first invention, wherein the switching timing is set to a start time of the inertia period.

  In a third aspect of the invention, the switching timing is set to a point in time when the feeding speed during the inertia period is decelerated to a predetermined value. The welding end control method for consumable electrode arc welding according to the first aspect of the invention. It is.

  4th invention calculates the said average arc time in the predetermined period just before the said inertia period, The consumable electrode arc welding of any one of the 1st-3rd invention characterized by the above-mentioned This is a welding end control method.

  In a fifth aspect of the present invention, the consumable electrode arc welding is electrode negative polarity consumable electrode arc welding or AC consumable electrode arc welding, and the consumable according to any one of the first to fourth inventions It is a welding end control method of electrode arc welding.

  According to the first aspect, the average arc time is calculated during the period before the welding end signal is input, and the switching delay time is calculated by multiplying the average arc time by the coefficient. Then, when a welding end signal is input and an inertia period is entered, a predetermined switching timing elapses, and energization of a pulse current is started when the arc period reaches the switching delay time. For this reason, since the pulse current starts energization when the droplet becomes an appropriate size, it is possible to perform smooth switching with less spattering.

  According to the second aspect, even when the switching timing is set to the start point of the inertia period, the effect of the first aspect is obtained.

  According to the third aspect of the invention, even when the switching timing is set to the time point when the feeding speed during the inertia period is decelerated to a predetermined value, the effect of the first aspect of the invention is achieved.

  According to the fourth aspect, the average arc time is calculated during the predetermined period immediately before the inertia period. For this reason, since the average arc time can be calculated in substantially the same state as the arc state during the inertia period, the droplet size at the start of energization of the pulse current can be more accurately set to an appropriate value, and spatter generation can be further increased. Can be suppressed.

  According to the fifth aspect, the present invention can be applied even when the consumable electrode arc welding is electrode negative polarity consumable electrode arc welding or AC consumable electrode arc welding.

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

[Embodiment 1]
FIG. 1 is a waveform diagram showing a welding end control method of consumable electrode arc welding according to Embodiment 1 of the present invention. (A) shows the start signal On, (B) shows the feeding speed vf, (C) shows the welding current Iw, (D) shows the welding voltage Vw, Figures (F1) to (F3) show the arc state at each time. This figure corresponds to FIG. 5 described above. Hereinafter, a description will be given with reference to FIG.

  An average arc time Tav, which is an average value of arc periods Ta generated during a predetermined period (several tens of ms to several seconds) before time t4, is calculated. Then, the switching delay time Td is calculated by multiplying the average arc time Tav by a coefficient in the range of 0.3 to 0.7. The meaning of the coefficient will be described later.

  At time t2, as shown in FIG. 9A, when the start signal On changes to a low level (welding end signal), a stop signal is input to the feed motor, and as shown in FIG. The feeding speed vf is slowly decelerated due to inertia and stops at time t4. When the arc period reaches the switching delay time Td at time t3, the application of pulse current is started as shown in FIG. Therefore, the energization of the pulse current is when the predetermined switching timing (time t2) has elapsed and the arc period has reached the switching delay time Td thereafter.

  At time t1, the short circuit is released and the arc 3 is regenerated as shown in FIG. At this time, since the droplet at the tip of the welding wire 1 has moved due to a short circuit, there is almost no droplet. Just before time t3, a small droplet is formed as shown in FIG. This is because the arc period from time t1 to t3 is the switching delay time Td, and the switching delay time Td is a time obtained by multiplying the average arc time Tav by a coefficient of 0.3 to 0.7. Therefore, since a large droplet grows near the time when the average arc time Tav has elapsed and a short circuit occurs, the droplet 4 is small when the switching delay time Td has elapsed. At time t3, as shown in FIG. 5F3, when a pulse current is applied, the droplet 4 is sprayed without spattering. When the above coefficient is a value close to 0, as described above with reference to FIG. 6, a pulse current is applied immediately after the release of the short circuit, and spatter is generated from the molten pool. Further, when the coefficient is close to 1, as described above with reference to FIG. 7, the droplet grows large and spatter is generated from the droplet by energization of the pulse current. Therefore, the appropriate coefficient is in the range of 0.3 to 0.7. The average arc time Tav may be calculated during the entire welding period up to time t2 or during a partial period.

  FIG. 2 is a block diagram of a welding power source PS for carrying out the welding end control method of the consumable electrode arc welding according to Embodiment 1 described above. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply such as a three-phase 200V as an input, performs output control such as inverter control and thyristor phase control according to a drive signal Dv described later, and outputs a welding voltage Vw and a welding current Iw suitable for arc welding. To do. The welding wire 1 is fed through the welding torch 6 by a feed roll 7 coupled to a feed motor M, and an arc 3 is generated between the base metal (the molten pool 2).

  The feed control circuit FC receives the start signal On from the outside, rotates the feed motor by a predetermined value when the start signal On is at a high level (welding start signal), and when the start signal On is at a low level (welding end signal). Outputs a feed control signal Fc for stopping the rotation. The inertia period off-delay circuit OD outputs the inertia period off-delay signal Od by delaying the start signal On from changing from the High level to the Low level by a period corresponding to a predetermined inertia period.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The voltage detection signal VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The arc period measuring circuit TA measures the elapsed time of the arc period from the time when the short circuit is released and the arc is regenerated, and outputs an arc period signal Ta. The switching delay time calculation circuit TD averages the arc period signal Ta during the steady welding period to calculate an average arc time, multiplies it by a predetermined coefficient, and outputs a switching delay time signal Td. The switching control circuit SC becomes a high level when the activation signal On becomes a high level, and at the time when the arc period signal Ta becomes equal to the value of the switching delay time signal Td after changing to the low level. The switching control signal Sc which becomes Low level is output.

The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. The pulse current setting circuit IPR outputs a pulse current setting signal Ipr formed from the pulse current and the base current. The voltage error amplification circuit EV amplifies the error between the voltage setting signal Vr and the voltage detection signal Vd and outputs a voltage error amplification signal Ev. The current error amplification circuit EI amplifies an error between the pulse current setting signal Ipr and the current detection signal Id and outputs a current error amplification signal Ei. When the switching control signal Sc is at a high level (non-pulse energization period), the switching circuit SW switches to the a side, outputs the voltage error amplification Ev as an error amplification signal Ea, and outputs a low level (pulse energization period). ), The current error amplification signal Ei is output as the error amplification signal Ea. Therefore, when the switching control signal Sc is at a high level, constant voltage control is performed as in a general consumable electrode arc welding power source, and when it is at a low level, constant current control is performed and a pulse current (including a base current) is energized. Although not shown at this time, the arc length during this period is controlled by varying the period in which the pulse current is applied based on the voltage error amplification signal Ev. The drive circuit DV performs PWM control or the like based on the error amplification signal Ea and outputs the drive signal Dv while the inertia period off-delay signal Od is at a high level (between steady welding machines + inertia period). .

  According to the first embodiment described above, the average arc time is calculated during the period before the welding end signal is input, and the switching delay time is calculated by multiplying this by the coefficient. Then, when a welding end signal is input and an inertia period starts, a predetermined switching timing elapses, and energization of a pulse current is started when the arc period reaches the switching delay time. For this reason, since the pulse current starts energization when the droplet becomes an appropriate size, it is possible to perform smooth switching with less spattering.

[Embodiment 2]
FIG. 3 is a waveform diagram corresponding to FIG. 1 in the case where the switching timing is set at the time when the feed speed vf is decelerated to a predetermined value during the inertia period Tk. Only differences from FIG. 1 will be described below.

  At time t1, when the start signal On changes to a low level (welding end signal) as shown in FIG. 9A, the feed speed vf is decelerated due to inertia as shown in FIG. At time t3, when the feed speed vf is decelerated to the predetermined value vft, the switching timing is reached. Thereafter, when the switching delay time Td in which the arc period is calculated at time t4 is reached, energization of the pulse current is started as shown in FIG. Since the size of the droplet at the time of applying the pulse current is an appropriate size, the switching can be smoothly performed with less spattering.

  FIG. 4 is a block diagram of a welding power source for carrying out the welding end control method of consumable electrode arc welding according to Embodiment 2 described above. In the figure, the same blocks as those in FIG. Hereinafter, blocks indicated by dotted lines different from those in FIG. 2 will be described.

  The comparison circuit CM receives the feed speed detection signal vfd of the feed motor M and outputs a comparison signal Cm that becomes High level when decelerated to a predetermined vft during the inertia period. The time when the comparison signal Cm becomes High level is the predetermined switching timing. The second switching control circuit SC2 becomes the high level when the start signal On becomes the high level (welding start signal), and the value of the arc period signal Ta changes to the switching t delay time signal after the comparison signal Cm changes to the high level. When it becomes equal to the value of Td, the switching control signal Sc that changes to the Low level is output.

  According to the second embodiment described above, even when the switching timing to the pulse current is set to the time when the feeding speed during the inertia period is decelerated to a predetermined value, the effects of the first embodiment described above can be achieved. .

  In the present invention, when the welding method until energizing the pulse current is AC consumable electrode arc welding that does not energize the pulse current with a short circuit, or negative polarity consumable electrode arc welding that energizes the short circuit but does not energize the pulse current. There is an effect. Further, the switching delay time may be calculated and set in advance by experiments.

It is a wave form diagram which shows the welding end control method of the consumable electrode arc welding which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply which concerns on Embodiment 1 of this invention. It is a wave form diagram which shows the welding end control method of the consumable electrode arc welding which concerns on Embodiment 2 of this invention. It is a block diagram of the welding power supply which concerns on Embodiment 2 of this invention. It is a wave form diagram which shows the welding end control method of consumable electrode arc welding in a prior art. It is a wave form diagram corresponding to Drawing 5 showing the subject of conventional technology. FIG. 7 is a waveform diagram different from FIG. 6 corresponding to FIG.

Explanation of symbols

1 Welding wire 2 Melt ground (base material)
3 Arc 4 Droplet 5 Spatter 6 Welding Torch 7 Feed Roll CM Comparison Circuit Cm Comparison Signal DV Drive Circuit Dv Drive Signal Ea Error Amplification Signal EI Current Error Amplification Circuit Ei Current Error Amplification Signal EV Voltage Error Amplification Circuit Ev Voltage Error Amplification Signal FC feed control circuit Fc feed control signal ID current detection circuit Id current detection signal Ipe last pulse current IPR pulse current setting circuit Ipr pulse current setting signal Iw welding current M feed motor OD inertia period off delay circuit Od inertia period off Delay signal On Start signal PM Power supply main circuit PS Welding power supply SC Switching control circuit Sc Switching control signal SC2 Second switching control circuit SW Switching circuit TA Arc period measuring circuit Ta Arc period (signal)
Tav average arc time TD switching delay time calculation circuit Td switching delay time (signal)
Tk inertia period Ts short circuit period VD voltage detection circuit Vd voltage detection signal vf feed speed vfd predetermined value detection signal vft predetermined feed speed value VR voltage setting circuit Vr voltage setting signal Vw welding voltage

Claims (5)

When consumable electrode arc welding with short circuit is performed without applying a pulse current, if a welding end signal is input to the welding power source, a stop signal is output to the feed motor, and the feed signal is received in response to the stop signal. In the welding end control method of consumable electrode arc welding, the motor decelerates and stops due to inertia and stops welding by switching the welding current to a pulse current during this inertia period.
An average arc time, which is an average value of arc periods between short circuits, is calculated during welding before the welding end signal is input, and the average arc time is determined within a range of 0.3 to 0.7. Multiply the coefficient of to calculate the switching delay time,
The switching to the pulse current is performed at the time when the arc period starts and the switching delay time is reached after a predetermined switching timing has elapsed from the start time of the inertia period. Termination control method.   2. The welding end control method for consumable electrode arc welding according to claim 1, wherein the switching timing is set to a start time of the inertia period.   2. The welding end control method of consumable electrode arc welding according to claim 1, wherein the switching timing is set to a time point when a feeding speed during the inertia period is decelerated to a predetermined value.   The welding end control method for consumable electrode arc welding according to any one of claims 1 to 3, wherein the average arc time is calculated during a predetermined period immediately before the inertia period. 5. The consumable electrode arc welding welding end control method according to any one of claims 1 to 4, wherein the consumable electrode arc welding is electrode negative polarity consumable electrode arc welding or AC consumable electrode arc welding. .

Images