JP5871360B2 - Constriction detection control method for consumable electrode arc welding - Google Patents

Description

  The present invention relates to a constriction detection control method of consumable electrode arc welding for detecting a constriction of a droplet during a short circuit period and reducing welding current to improve welding quality.

  FIG. 4 is a diagram showing current / voltage waveforms and droplet transfer in consumable electrode arc welding in which the short-circuit period Ts and the arc period Ta are repeated. FIG. 4A shows the change over time of the welding current Iw for energizing the consumable electrode (hereinafter referred to as welding wire 1), and FIG. 4B shows the welding voltage applied between the welding wire 1 and the base material 2. FIG. The time change of Vw is shown, The figure (C)-(E) shows the mode of the transfer of the droplet 1a. Hereinafter, a description will be given with reference to FIG.

  During the short-circuit period Ts from time t1 to t3, the droplet 1a at the tip of the welding wire 1 is in a state of being short-circuited to the base material 2. The welding current Iw is maintained at an initial current value of a small current value during a predetermined initial period from time t1 to t11, and is determined during a subsequent period from time t11 to t12, as shown in FIG. The value increases with an inclination, and is controlled to a predetermined peak value from time t12 to time t3 when the arc is regenerated. The initial period is set to about 1 ms, the initial current value is set to about 50 A, the slope is set to about 100 to 300 A / ms, and the peak value is set to about 300 to 400 A. These values are set to appropriate values according to the type of welding wire, the type of shield gas, the feeding speed, and the like. As shown in FIG. 5B, the welding voltage Vw has a low value of about several volts because it is in a short circuit state.

  As shown in FIG. 5C, the droplet 1a comes into contact with the base material 2 at a time t1 to enter a short circuit state. When the short circuit state is entered, the welding current is reduced to an initial current having a small current value, so that a more reliable short circuit state is led. Thereafter, since the welding current Iw increases, as shown in FIG. 4D, a constriction 1b is generated above the droplet 1a due to the electromagnetic pinch force generated by the welding current Iw energizing the droplet 1a. This electromagnetic pinch force increases in proportion to the value of the welding current Iw. Therefore, by increasing the welding current Iw, the electromagnetic pinch force is increased and the formation of the constriction 1b is promoted. And this constriction 1b advances rapidly, and as shown to the same figure (E) at the time t3, the droplet 1a transfers from the welding wire 1 to the molten pool 2a, and the arc 3 regenerates.

  When the constriction 1b is generated in the droplet 1a, the short circuit is opened after a short time of about several hundred μs, and the arc 3 is regenerated. That is, this constriction phenomenon is a precursor of short circuit opening. When the constriction 1b occurs, the conduction path of the welding current Iw becomes narrow at the constricted portion, and the resistance value of the constricted portion increases. The increase in the resistance value increases as the constriction progresses and the constricted portion becomes narrower. Therefore, by detecting a change in resistance value between the welding wire 1 and the base material 2 during the short-circuit period Ts, it is possible to detect the occurrence and progress of the necking phenomenon. This change in resistance value can be calculated by dividing the welding voltage Vw by the welding current Iw. Further, the change in resistance value after the formation of the constriction is larger than the change in the welding current Iw during the short-circuit period Ts. For this reason, the occurrence of the constriction phenomenon can be detected by the change of the welding voltage Vw instead of the change of the resistance value. As a specific necking detection method, the rate of change (differential value) of the resistance value or the welding voltage value Vw during the short-circuit period Ts is calculated, and the necking is achieved by reaching the predetermined necking detection reference value Vtn. There is a way to detect. As another method, as shown in FIG. 5B, a voltage increase value ΔV from a stable short-circuit voltage value Vs before the occurrence of constriction during the short-circuit period Ts (during the initial period described above) is calculated. There is a method of detecting squeezing when the voltage increase value ΔV reaches a predetermined squeezing detection reference value Vtn at t2. In the following description, a case in which the squeezing detection method is based on the above-described voltage increase value ΔV will be described, but other methods that have been proposed in the past may be used. Detection of arc reoccurrence at time t3 can be easily performed by determining that the welding voltage Vw has become equal to or greater than the short circuit / arc determination value Vta. That is, the period of Vw <Vta is the short circuit period Ts, and the period of Vw ≧ Vta is the arc period Ta. The time from the occurrence of squeezing at times t2 to t3 to the reoccurrence of the arc is hereinafter referred to as squeezing detection time Tn. When the arc is regenerated at the time t3, the welding current Iw gradually decreases as shown in FIG. 5A, and the welding voltage Vw is about 20-30V as shown in FIG. become. Therefore, the short circuit / arc discrimination value Vta is set to about 10 to 15V. During the arc period Ta from time t3 to t4, the tip of the welding wire 1 is melted to form a droplet 1a. Thereafter, the operation in the period from time t1 to t4 is repeated.

  Examples of the consumable electrode arc welding that repeats the short-circuit period Ts and the arc period Ta include carbon dioxide arc welding, mag welding, MIG welding, and pulse arc welding with short-circuiting. In the case of carbon dioxide arc welding, mag welding, and MIG welding, the droplet transfer mode is a short-circuit transfer mode in a current region of less than about 200 A, and a globule transfer mode when the current value increases. In the case of pulse arc welding, the droplet transfer mode is a spray transfer mode. Also in these globule transfer forms and spray transfer forms, when performing high-speed welding or the like, the arc length is set short, so that a short circuit occurs. Therefore, in order to open this short circuit, the constriction 1b is formed as described above.

  In the welding with short circuit described above, when the arc regeneration current value Ia when the arc 3 is regenerated at the time t3 is a large current value, the arc force from the arc 3 to the molten pool 2a increases sharply. A large amount of spatter is generated. That is, the amount of spatter generated increases substantially in proportion to the current value Ia at the time of arc re-generation. For this reason, in order to suppress generation | occurrence | production of a sputter | spatter, it is necessary to make small this electric current value Ia at the time of arc regeneration. As a method for this purpose, various welding power sources have been proposed in which a constriction detection control method for reducing the current value Ia during arc re-occurrence by detecting the occurrence of the constriction and reducing the welding current Iw has been proposed. Hereinafter, this conventional technique (for example, refer to Patent Document 1) will be described.

  FIG. 5 is a block diagram of a welding apparatus equipped with a conventional necking detection control method. The welding power source PS is a welding power source for general consumable electrode arc welding, and outputs a welding voltage Vw and a welding current Iw and a feeding control signal Fc for controlling the rotation of the feeding motor WM. Output to motor WM. The current reducing resistor R is inserted in series with the output, and a transistor TR is connected in parallel thereto. 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.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The squeezing detection reference value setting circuit VTN outputs a squeezing detection reference value signal Vtn. The squeezing detection circuit ND receives the squeezing detection reference value signal Vtn, the voltage detection signal Vd, and the current detection signal Id, and the voltage increase value ΔV during the short circuit period is converted into the squeezing detection reference value signal Vtn as described above. When the value reaches the high level, the squeezing detection signal Nd is output at a high level when the arc is regenerated and the voltage detection signal Vd becomes equal to or greater than the short-circuit / arc discrimination value Vta. Therefore, the squeezing detection time Tn is a period during which the squeezing detection signal Nd is at a high level. As described above, the squeezing detection signal Nd may be changed to a high level when the differential value of the voltage detection signal Vd during the short circuit period reaches the value of the squeezing detection reference value signal Vtn corresponding thereto. Further, the resistance value of the droplet is calculated by dividing the value of the voltage detection signal Vd by the value of the current detection signal Id, and when the differential value of the resistance value reaches the value of the squeezing detection reference value signal Vtn corresponding thereto. The constriction detection signal Nd may be changed to a high level. When the squeezing detection signal Nd is at a low level (when non-necking is detected), the driving circuit DR outputs a driving signal Dr that turns on the transistor TR. Therefore, the transistor TR is turned off when the squeezing detection signal Nd is at a high level (when squeezing is detected).

  FIG. 6 is a timing chart of each signal of the welding apparatus. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the squeezing detection signal Nd, (D) ) Shows the time change of the drive signal Dr. Hereinafter, a description will be given with reference to FIG.

  In the figure, during a period other than the squeezing detection time Tn from time t2 to t3, as shown in FIG. 10C, the squeezing detection signal Nd is at the low level, and as shown in FIG. The signal Dr becomes a high level. As a result, the transistor TR is turned on and the current reducing resistor R is short-circuited, so that the operation is the same as that of an ordinary welding apparatus for consumable electrode arc welding.

  At time t2, as shown in FIG. 5B, it is detected that the welding voltage Vw has increased during the short circuit period Ts and the voltage increase value ΔV has become equal to the value of the predetermined squeezing detection reference value signal Vtn. If it is determined that constriction has occurred in the droplet, the constriction detection signal Nd becomes High level as shown in FIG. In response to this, as shown in FIG. 4D, the drive signal Dr goes to a low level, so that the transistor TR is turned off. As a result, the current reducing resistor R is inserted into the current path of the welding current Iw. The value of the current reducing resistor R is set to a value (about 0.5 to 3Ω) that is 10 times or more larger than the short-circuit load (about 0.01 to 0.03Ω). For this reason, the energy accumulated in the DC reactor and the cable reactor in the welding power source is suddenly discharged, and the welding current Iw decreases rapidly as shown in FIG. The current Il becomes. Here, assuming that the output voltage of the welding power source PS is 50V and the current reducing resistor R is 1Ω, the low-level current Il is 50A. As shown in FIG. 5B, the welding voltage Vw rapidly increases after once decreasing because the welding current Iw decreases rapidly at time t2. At time t3, when the short circuit is released and the arc is regenerated, the welding voltage Vw becomes equal to or higher than a predetermined short circuit / arc discrimination value Vta as shown in FIG. By detecting this, the squeezing detection signal Nd becomes the Low level as shown in FIG. 5C, and the drive signal Dr becomes the High level as shown in FIG. As a result, the transistor TR is turned on, and normal consumable electrode arc welding is controlled. At time t3, when the arc is regenerated and the transistor TR is turned on, the welding current Iw increases gradually to a predetermined high current value and gradually decreases as shown in FIG. Converges to a value determined by. By this operation, the current value Ia at the time of arc re-occurrence at time t3 can be reduced, so that the occurrence of sputtering can be suppressed. As a means for rapidly reducing the welding current Iw when the constriction is detected, the method for inserting the current reducing resistor R into the energizing path has been described above. As another means, a capacitor is connected in parallel between the output terminals of the welding apparatus via a switching element, and when the constriction is detected, the switching element is turned on and a discharge current is supplied from the capacitor to rapidly reduce the welding current Iw. There is also a method (see, for example, Patent Document 2).

  In the above-described constriction detection control method, it is important to accurately detect the occurrence of constriction in order to increase the effect of suppressing the amount of spatter generated. The occurrence of the constriction and the state of progress thereof vary depending on the welding conditions such as the type of shielding gas, the type of welding wire, the weld joint, the feeding speed of the welding wire, and the welding posture. For this reason, it is necessary to optimize the sensitivity for detecting the occurrence of constriction according to the welding conditions. The squeezing detection sensitivity can be adjusted by increasing or decreasing the squeezing detection reference value Vtn. That is, when the squeezing detection reference value Vtn is increased, the sensitivity is lowered, and conversely, when it is decreased, the sensitivity is increased. If the squeezing detection reference value Vtn is too large, the sensitivity will be too low, the squeezing detection time Tn will be shortened, and sometimes the squeezing cannot be detected, and the welding current can be sufficiently reduced before the arc is regenerated. Since this is not possible, the effect of suppressing the amount of spatter is reduced. Conversely, if the squeezing detection reference value Vtn is too small, the sensitivity will be too high, and the above-described squeezing detection time Tn will be too long and the arc will not reoccur, making the welding state unstable. Therefore, it can be said that the squeezing detection time Tn is in the range of about 50 to 1000 μs when the squeezing detection reference value Vtn is set to an appropriate value.

  As described above, the squeezing detection reference value Vtn is set to an appropriate value according to the welding conditions. However, even if the squeezing detection reference value Vtn is optimized due to fluctuation factors such as fluctuations in the feeding speed, irregular movement of the molten pool, and variations in droplet shape, the squeezing detection time Tn varies. When the range of this variation is about 50 to 1000 μs as described above, there is not much adverse effect on the occurrence of spatter and the stability of the welded state. Moreover, even if the constriction detection time Tn occasionally becomes less than 50 μs, it is only a slight increase in spatter and is not a big problem. On the other hand, when the squeezing detection time Tn exceeds 1000 μs, particularly 2000 μs or more, the welding state becomes unstable, and the arc may not be regenerated. For this reason, if the arc has not regenerated even if the elapsed time from the point of detection of the constriction reaches the reference time, the constriction progresses by increasing the electromagnetic pinch force by increasing the welding current Iw. Compensation control is commonly used to promote and reinitiate arcs. Hereinafter, this compensation control (see, for example, Patent Document 3) will be described.

  FIG. 7 is a timing chart of each signal corresponding to FIG. 6 described above for explaining the compensation control. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the squeezing detection signal Nd, (D) ) Shows the time change of the drive signal Dr. In the figure, the operations other than the operation during the period from time t21 to t3 are the same as those in FIG. The operation during the period from time t21 to t3 will be described below with reference to FIG.

  When the elapsed time t from the necking detection time at time t2 reaches a predetermined reference time Tt at time t21, the welding voltage Vw is less than the short circuit / arc discrimination value Vta as shown in FIG. As it is, the arc has not regenerated yet. In such a case, the drive signal Dr is changed to a high level as shown in FIG. When the drive signal Dr becomes high level, the transistor TR in FIG. 5 is turned on, so that the welding current Iw increases with a steep slope from the low level current Il as shown in FIG. Becomes a high level current Ih. This steep inclination is the fastest inclination that the welding apparatus can output, and is about 1000 A / ms. The high level current Ih is about 500A. As the welding current Iw increases, the electromagnetic pinch force also increases, so that the progress of the constriction is promoted and the arc is regenerated at time t3. As shown in FIG. 5B, the welding voltage Vw once decreases immediately after time t2, and then gradually increases until time t21. When the welding current Iw increases to the high level current Ih at time t21, the welding voltage Vw increases rapidly. When the arc is regenerated at time t3, the arc voltage value becomes equal to or greater than the short circuit / arc determination value Vta. When the arc is regenerated at time t3, the welding current Iw gradually decreases and converges to a steady value as shown in FIG. As shown in FIG. 6C, the squeezing detection signal Nd is at a high level from the time of squeezing detection at time t2 until the occurrence of arc at time t3. As shown in FIG. 4D, the drive signal Dr becomes High level from time t21. The reference time Tt is set to about 1000 μs. This reference time Tt is set to an appropriate value according to the type of welding wire, the type of shield gas, the weld joint, the feeding speed of the welding wire, the welding posture, and the like.

JP 2006-281219 A JP 2005-288540 A JP 2006-116585 A

  As described above, the welding state is prevented from becoming unstable by increasing the welding current when the arc has not regenerated even when the elapsed time from the necking detection time reaches the reference time. . However, when such compensation control is performed, as shown in FIG. 7A, since the current value when the arc is regenerated at time t3 becomes a large value, there is a problem that large spatters are generated. there were

  Therefore, in the present invention, when the arc has not regenerated even if the elapsed time from the time of detection of the constriction has reached the reference time, the arc can be regenerated smoothly without increasing the generation of spatter. An object of the present invention is to provide a constriction detection control method for electrode arc welding.

In order to solve the above-described problems, the invention of claim 1 is consumable electrode arc welding in which an arc generation state and a short circuit state are repeated between a welding wire and a base material, and the arc is regenerated from the short circuit state. In the constriction detection control method of consumable electrode arc welding, which detects the constriction of droplets, which is a precursor phenomenon, and reduces the welding current passed through the short-circuit load from the time of the constriction detection to regenerate the arc in a low level current state.
When the elapsed time from the necking detection time reaches a predetermined reference time before the arc is regenerated, the welding current is increased from the low level current to the high level current to regenerate the arc. The level current value and / or rising slope is changed according to the progress of the constriction when the reference time is reached.
This is a constriction detection control method for consumable electrode arc welding.

The invention of claim 2 detects the progress of the constriction by a change in voltage value or resistance value between the welding wire and the base material.
The constriction detection control method for consumable electrode arc welding according to claim 1.

  According to the present invention, when the elapsed time from the squeezing detection time reaches the reference time before the arc is regenerated, the welding current is increased from the low level current to the high level current to regenerate the arc. The value of the high level current and / or the rising slope is changed according to the progress of the constriction when the reference time is reached. When the degree of progress of the constriction is advanced, even if the high level current is a relatively small value, it is possible to lead to the arc regeneration early. On the other hand, when the progress of the constriction is delayed, the arc cannot be regenerated unless the high level current is a relatively large value. A case in which the elapsed time from the point of detection of the squeezing is longer than the reference time and a high level current is applied occurs several times per second, depending on the welding conditions. Since the progress of the constriction at the time when the reference time is reached varies, the value of the high level current also changes correspondingly. As a result, the current value when the arc is regenerated also changes variously, and the average value is smaller than that of the prior art. Therefore, in the present invention, even when the elapsed time from the necking detection time is equal to or longer than the reference time, it is possible to lead to a smooth arc regeneration, and the amount of large spatter generated can be reduced as a total amount. .

It is a block diagram of the welding apparatus for implementing the constriction detection control method of the consumable electrode arc welding which concerns on embodiment of this invention. It is a timing chart of each signal in the welding apparatus of FIG. FIG. 2 is a diagram illustrating an example of a current setting function built in a high level current setting circuit IHR and a slope setting function built in a rising slope setting circuit SR in FIG. 1. In a prior art, it is a figure which shows the electric current and voltage waveform and droplet transfer in consumable electrode arc welding which repeats the short circuit period Ts and the arc period Ta. It is a block diagram of the welding apparatus carrying the necking detection control method of a prior art. It is a timing chart of each signal in the welding apparatus of FIG. It is a timing chart of each signal corresponding to above-mentioned FIG. 6 for demonstrating the compensation control in a prior art.

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

  FIG. 1 is a block diagram of a welding apparatus for carrying out a constriction detection control method for consumable electrode arc welding according to an embodiment 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 three-phase 200 V, performs output control such as inverter control according to an error amplification signal Ea described later, and outputs a welding voltage Vw and a welding current Iw. This power supply main circuit PM is omitted in the drawing, but a primary rectifier that rectifies commercial power, a smoothing capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current to high frequency alternating current, and high frequency alternating current for welding A high-frequency transformer that steps down to a suitable voltage value, a secondary rectifier that rectifies the stepped-down high-frequency alternating current into direct current, a reactor that smoothes the rectified direct current, a modulation circuit that performs pulse width modulation control using the error amplification signal Ea as an input, The inverter driving circuit is configured to drive the switching element of the inverter circuit with the pulse width modulation control signal as an input.

  The current reducing resistor R is inserted between the power supply main circuit PM and the welding torch 4. The value of the current reducing resistor R is the same as that of the above-described prior art. The transistor TR is connected in parallel with the current reducing resistor R and is controlled to be turned on or off in accordance with a drive signal Dr described later.

  The welding wire 1 is fed through the welding torch 4 by the rotation of a feeding roll 5 coupled to a feeding motor (not shown), and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the welding wire 1 and the base material 2, and a welding current Iw is passed through the arc 3. In the figure, the circuit for controlling the feeding of the welding wire is not shown.

  The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd.

  The short-circuit / arc discrimination circuit SD receives the voltage detection signal Vd as described above, and when the value is less than a predetermined short-circuit / arc discrimination value Vta, the short-circuit / arc discrimination circuit determines that it is in a short-circuit state and becomes a high level. Outputs a short-circuit / arc determination signal Sd which is determined to be in the arc generation state and becomes low level. As in the prior art, the squeezing detection circuit ND receives the voltage detection signal Vd and the current detection signal Id as described above, and the voltage increase value ΔV during the short-circuit period as described above is a predetermined squeezing detection reference value Vtn. When the value reaches the high level, the squeezing detection signal Nd is output at a high level when the arc is regenerated and the voltage detection signal Vd becomes equal to or greater than the short-circuit / arc discrimination value Vta. As described above, the squeezing detection signal Nd may be changed to a high level when the differential value of the voltage detection signal Vd during the short circuit period reaches the squeezing detection reference value Vtn corresponding thereto. Further, the resistance value of the droplet is calculated by dividing the value of the voltage detection signal Vd by the value of the current detection signal Id, and when the differential value of the resistance value reaches the corresponding squeezing detection reference value Vtn, the squeezing is detected. The signal Nd may be changed to a high level.

  The low level current setting circuit ILR outputs a predetermined low level current setting signal Ilr. The value of the low level current setting signal Ilr is set to about 50A. The current comparison circuit CM receives the low-level current setting signal Ilr and the current detection signal Id as input, and outputs a current comparison signal Cm that is at a high level when Id <Ilr and is at a low level when Id ≧ Ilr. Output. The drive circuit DR receives the current comparison signal Cm and the above-described squeezing detection signal Nd, changes to a low level when the squeezing detection signal Nd changes to a high level, and then changes to a high level when the current comparison signal Cm changes to a high level. The drive signal Dr that changes in level is output to the base terminal of the transistor TR. Therefore, when the constriction is detected, the drive signal Dr becomes a low level, the transistor TR is turned off, and the current reducing resistor R is inserted into the energization path. To do. When the sharply decreased welding current Iw value decreases to the low level current setting signal Ilr value, the drive signal Dr becomes a high level and the transistor TR is turned on. Return to the state.

  The reference time setting circuit TTR outputs a predetermined reference time setting signal Ttr. The value of the reference time setting signal Ttr is set to about 600 to 1000 μs. The elapsed time discriminating circuit CT receives the reference time setting signal Ttr and the above-described squeezing detection signal Nd, and when the time when the squeezing detection signal Nd is at the high level reaches the value of the reference time setting signal Ttr, High. When the squeezing detection signal Nd changes to the Low level, an elapsed time determination signal Ct that is reset to the Low level is output.

  The squeezing progress detection circuit NS receives the elapsed time determination signal Ct, the voltage detection signal Vd, and the current detection signal Id, and receives the voltage detection signal Vd at the time when the elapsed time determination signal Ct becomes High level. Is output as a constriction progress signal Ns. As the value of the voltage detection signal Vd is larger, it indicates that the constriction is progressing. Therefore, the value of the voltage detection signal Vd can be used as an index indicating the progress of the constriction. Further, the differential value of the voltage detection signal Vd at the time when the elapsed time determination signal Ct becomes the High level can be used as an index indicating the progress of the constriction. Further, the resistance value (= Vd / Id) of the droplet at the time when the elapsed time determination signal Ct becomes the High level or the differential value can be used as an index indicating the progress of the constriction. The high level current setting circuit IHR outputs the high level current setting signal Ihr calculated by a predetermined current setting function with the squeezing progress signal Ns as an input. The rising slope setting circuit SR receives the squeezing progress signal Ns as an input, and outputs a rising slope setting signal Sr calculated by a predetermined slope setting function. The current setting function and the slope setting function will be described later with reference to FIG.

The current setting circuit IR includes the short circuit / arc determination signal Sd, the low level current setting signal Ilr, the squeezing detection signal Nd, the elapsed time determination signal Ct, the high level current setting signal Ihr, and the above The following processing is performed with the rising slope setting signal Sr as an input, and the current setting signal Ir is output. The operation of this circuit is also described in detail in FIG.
1) A predetermined initial current set value is output as the current setting signal Ir during a predetermined initial period from the time when the short circuit / arc determination signal Sd changes to the high level (short circuit).
2) Thereafter, the value of the current setting signal Ir is increased from the initial current setting value to a predetermined peak setting value with a slope determined by a predetermined slope setting value, and the value is maintained.
3) When the squeezing detection signal Nd changes to the high level (squeezing detection), the value of the current setting signal Ir is switched to the value of the low level current setting signal Ilr.
4) When the elapsed time determination signal Ct changes to the High level (when the squeezing detection time reaches the reference time), the value of the current setting signal Ir is determined from the value of the low level current setting signal Ilr by the rising slope setting signal Sr. The value is increased to the value of the high level current setting signal Ihr by the inclination, and the value is maintained.

  The voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the welding voltage during the arc period. The current error amplification circuit EI amplifies an error between the current setting signal Ir (+) and the current detection signal Id (−) and outputs a current error amplification signal Ei. The voltage error amplification circuit EV amplifies an error between the voltage setting signal Vr (+) and the voltage detection signal Vd (−) and outputs a voltage error amplification signal Ev. The control switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, and the short circuit / arc determination signal Sd as an input. When the short circuit / arc determination signal Sd is at a high level (short circuit), the current is amplified. The error amplification signal Ei is output as the error amplification signal Ea, and when the level is low (arc), the voltage error amplification signal Ev is output as the error amplification signal Ea. This circuit provides constant current control during the short circuit period and constant voltage control during the arc period.

  FIG. 2 is a timing chart of each signal in the welding apparatus described above with reference to FIG. (A) shows the time change of the welding current Iw, (B) shows the time change of the welding voltage Vw, (C) shows the time change of the squeezing detection signal Nd, (D) ) Shows the time change of the drive signal Dr, FIG. 8E shows the time change of the short circuit / arc discrimination signal Sd, FIG. 8F shows the time change of the elapsed time discrimination signal Ct, and FIG. ) Shows the time change of the current setting signal Ir. This figure shows a case where the elapsed time from the point of detection of the squeezing reaches the reference time Tt before the arc is regenerated, and corresponds to FIG. 7 described above. The timing chart in the normal state where the arc is regenerated before the elapsed time from the squeezing detection time reaches the reference time Tt is basically the same operation as in FIG. Hereinafter, a description will be given with reference to FIG.

(1) Operation from occurrence of short circuit at time t1 to squeezing detection time at time t2 The operation during this period is the same as that in FIG. When the welding wire comes into contact with the base material at time t1, a short-circuit state occurs, and the welding voltage Vw rapidly decreases to a short-circuit voltage value of about several volts as shown in FIG. When it is determined that the welding voltage Vw is less than the short circuit / arc determination value Vta, the short circuit / arc determination signal Sd changes from the Low level to the High level as shown in FIG. In response to this, as shown in FIG. 5G, the current setting signal Ir changes from the value of the low level current setting signal Ilr to a predetermined initial current setting value which is a little larger at time t1. Here, the value of the current setting signal Ir is the value of the low-level current setting signal Ilr before the time t1 because the elapsed time from the time when the previous short-circuit release (arc reoccurrence) is detected is the reference time Tt. It was because it was done before reaching. When it is performed after reaching the reference time Tt, the value of the current setting signal Ir before time t1 becomes the value of the high level current setting signal Ihr. Regardless of the value, the current setting signal Ir is irrelevant to the operation because only the short-circuit period after the time t1 is used. The current setting signal Ir has a predetermined initial current setting value during a predetermined initial period from time t1 to t11, and a predetermined slope setting during the period from time t11 to t12, as shown in FIG. It rises at a slope determined by the value, and becomes a predetermined peak setting value during the period from time t12 to t2. Since the constant current control is performed as described above during the short circuit period, the welding current Iw is controlled to a value corresponding to the current setting signal Ir. For this reason, as shown in FIG. 6A, the welding current Iw rapidly decreases from the welding current in the arc period at time t1, and becomes an initial current value during the initial period from time t1 to t11, and from time t11 to t12. It rises at a predetermined slope during the period, and reaches a peak value during the period from time t12 to t2. As shown in FIG. 5B, the welding voltage Vw increases rapidly from around time t12 when the welding current Iw reaches its peak value. This is because constriction occurs in the droplets. As shown in FIG. 5C, the squeezing detection signal Nd is at a low level except during a period from time t2 to t3 described later. As shown in FIG. 4D, the drive signal Dr is at a low level during a period from time t2 to t21, which will be described later, and is at a high level during other periods. Accordingly, during the period before time t2 in the figure, the drive signal Dr is at a high level, and the transistor TR in FIG. 1 is turned on, so that the current reducing resistor R is short-circuited and the normal consumable electrode arc welding apparatus is used. It becomes the same state. As shown in FIG. 5F, the elapsed time determination signal Ct is at a high level during a period from time t22 to t3 described later, and is at a low level during other periods.

(2) Operation from the time when the necking is detected at time t2 until the reference time Tt at time t22 is reached At time t2, as shown in FIG. 5B, the welding voltage Vw rapidly rises from the voltage value during the initial period. When the necking is detected when the voltage increase value ΔV becomes equal to the predetermined necking detection reference value Vtn, the necking detection signal Nd changes to the high level as shown in FIG. In response to this, as shown in FIG. 4D, the drive signal Dr becomes the low level, so that the transistor TR in FIG. 1 is turned off and the current reducing resistor R is inserted into the energization path. At the same time, the current setting signal Ir is reduced to the value of the low level current setting signal Ilr, as shown in FIG. For this reason, as shown in FIG. 5A, the welding current Iw rapidly decreases from the peak value to the low level current value Il. When the welding current Iw decreases to the low level current value Il at time t21, as shown in FIG. 4D, the drive signal Dr returns to the high level, so that the transistor TR in FIG. The device R is short-circuited. As shown in FIG. 6A, the welding current Iw maintains the low level current value Il because the current setting signal Ir remains the low level current setting signal Ilr. Therefore, the transistor TR is turned off only during a period from when the constriction is detected at time t2 until the welding current Iw decreases to the low level current value Il at time t21. As shown in FIG. 5B, the welding voltage Vw gradually increases after once decreasing from time t2. However, since this figure shows a case where the arc does not reappear before time t22 when the elapsed time from the time of detection of the squeezing at time t2 reaches the reference time Tt, the welding voltage Vw rises sharply by time t22 and short-circuit / arc It does not exceed the discrimination value Vta.

(3) Operation from the time when the reference time Tt at the time t22 is reached to the occurrence of the arc again at the time t3 At the time t22, the elapsed time from the time when the squeezing detection signal Nd becomes High level at the time t2, the reference time setting signal When the reference time Tt determined by Ttr is reached, the elapsed time determination signal Ct changes to High level as shown in FIG. In response to this, as shown in FIG. 4G, the current setting signal Ir rises from the value of the low level current setting signal Ilr to the value of the high level current setting signal Ihr at a slope determined by the rising slope setting signal Sr. And maintain that value. For this reason, as shown in FIG. 2A, the welding current Iw rises from the low level current value Il to the high level current value Ih with a predetermined rising slope S, and maintains that value. Both values of the rising slope setting signal Sr and the high level current setting signal Ihr are changed according to a predetermined function according to the progress of the constriction at the time t22 when the elapsed time determination signal Ct changes to the high level. The progress of the constriction is as described above with reference to FIG. The function will be described later with reference to FIG. When the progress of the constriction is promoted by increasing the welding current Iw and the arc is regenerated at time t3, the welding voltage Vw becomes the high level current value Ih as shown in FIG. It rises rapidly from the hit, and becomes short circuit / arc discrimination value Vta or more at time t3. In response to this, as shown in FIG. 5E, the short circuit / arc discrimination signal Sd changes to the low level. As a result, the welding apparatus is switched from constant current control to constant voltage control. For this reason, as shown in FIG. 5A, the welding current Iw gradually decreases from the high level current value Ih. As shown in FIG. 5C, the squeezing detection signal Nd changes to the low level because the short circuit / arc determination signal Sd changes to the low level. Similarly, as shown in FIG. 5F, the elapsed time determination signal Ct also changes to the Low level. As shown in FIG. 5G, the current setting signal Ir maintains its value after time t3. Here, since the value of the high-level current setting signal Ihr is the time t3, the value is maintained.

  FIG. 3 is a diagram showing an example of the current setting function built in the high level current setting circuit IHR and the slope setting function built in the rising slope setting circuit SR described above with reference to FIG. The horizontal axis of the figure shows the squeezing progress signal Ns (V), which is in the range of 0 to 10V. The left vertical axis indicates the high level current setting signal Ihr (A), which is in the range of 0 to 600A. The right vertical axis indicates the rising slope setting signal Sr (A / ms), which is in the range of 0 to 600 A / ms. In the figure, the solid line shows the current setting function, and shows the relationship between the squeezing progress signal Ns and the high level current setting signal Ihr. The broken line indicates the slope setting function, and shows the relationship between the squeezing progress signal Ns and the rising slope setting signal Sr.

  As the squeezing progress signal Ns, as described above, the value of the voltage detection signal Vd at the time when the elapsed time determination signal Ct becomes the high level is used. That is, it is the value of the welding voltage Vw at the time (time t22 in FIG. 2) when the elapsed time from the necking detection time reaches the reference time Tt before the arc is regenerated.

  As shown in the figure, the current setting function is Ihr = 500 when Ns <3.0, and Ihr is a straight line descending from 500 to 200 in the range of 3.0 ≦ Ns <7.0. When Ns ≧ 7.0, Ihr = 200. Further, the slope setting function is Sr = 500 when Ns <3.0, and in the range of 3.0 ≦ Ns <7.0, Sr is a straight line descending from 500 to 100, and Ns ≧ 7.0. In this case, Sr = 100. That is, the value of the high-level current setting signal Ihr generally decreases as the squeezing progress signal Ns increases (the progress of the squeezing progresses). The value of the rising slope setting signal Sr generally decreases as the constriction progress signal Ns increases (the progress of the constriction progresses). Both functions may be changed into a curved shape, a staircase shape, or the like. It is desirable to optimize both functions by experiment according to the type of welding wire, the type of shield gas, the weld joint, the feeding speed of the welding wire, the welding posture, and the like.

  Next, the effect of the constriction detection control method for consumable electrode arc welding according to the embodiment of the present invention will be described with reference to FIGS. In the following description, the description will be divided into two cases. The first case is a case of normal neck detection control in which an arc is regenerated before the elapsed time from the neck detection time reaches the reference time. The second case is a case where the elapsed time from the necking detection time reaches the reference time before the arc is regenerated. The second case is the case of the timing chart of FIG. 2 described above, and the case where the present invention is effective.

(1) First Case Also in this case, the operation during the period from time t1 to t21 in FIG. At time t21, the welding current Iw is at the low level current value Il as shown in FIG. Then, before the elapsed time from the necking detection time at time t2 reaches the reference time Tt, the necking progresses and the arc is regenerated. That is, the arc is regenerated during the period from time t21 to t22. When the arc is regenerated, the welding voltage Vw shown in FIG. 4B rapidly increases and becomes an arc voltage value equal to or higher than the short-circuit / arc discrimination value Vta. In response to this, the short circuit / arc discrimination signal Sd shown in FIG. 5E changes to the low level, so that the constant current control is switched to the constant voltage control. As a result, the welding current Iw shown in FIG. The waveforms of the welding current Iw and the welding voltage Vw in this case are the same as those in FIG.

(2) Second Case The operation of the second case is as shown in FIG. Even if the elapsed time from the time of detecting the neck at time t2 reaches the reference time Tt at time t22, the arc is not regenerated, so that the welding current Iw is increased to the high level current value Ih to promote the progress of the necking. This leads to the reoccurrence of the arc. In the above-described prior art, the current level is increased to a predetermined high level current value Ih (500 A) with the fastest rising slope (1000 A / ms) regardless of the progress of the constriction when the reference time Tt is reached. For this reason, the current value at the time of arc re-occurrence is 500 A, which is a large value, so that large spatter is generated. On the other hand, in the present embodiment, the progress of the squeezing at the time when the reference time Tt is reached is detected, and the value of the high level current and / or the rising slope is optimized according to the squeezing progress, and the arc Sputtering is suppressed by making the current value at the time of re-generation smaller than that of the prior art. This is because, when the degree of constriction progresses, the arc can be regenerated even if the value of the high level current and / or the rising slope is reduced.

  Hereinafter, a numerical example will be given and described. In FIG. 3, it is assumed that the squeezing progress Ns = 5.0V when the reference time Tt is reached. It is assumed that the arc is regenerated when a time of 0.5 ms, 1.0 ms, or 1.5 ms has elapsed from the reference time. Even in actual welding, there is a high probability that an arc will reoccur in this range. In the prior art, since the rising slope is 1000 A / ms and the high level current value is 500 A, the current values when the arc is regenerated are 500 A, 500 A, and 500 A. On the other hand, in this embodiment, when only the high level current value is changed according to the degree of constriction, the high level current value when Ns = 5.0 V is 350 A from FIG. The current values when the arc is regenerated are 350A, 350A, and 350A. When only the rising slope is changed according to the progress of the constriction, the rising slope when Ns = 5.0 V is 300 A / ms from FIG. It becomes. In the case where both the value of the high level current and the rising slope are changed according to the progress of the constriction, 200A, 350A, and 350A are obtained from FIG. As can be seen from these numerical examples, the current value when the arc is regenerated is smaller in the present embodiment than in the prior art. Therefore, the occurrence of spatter is reduced.

  According to the above-described embodiment, when the elapsed time from the squeezing detection time reaches the reference time before the arc is regenerated, the welding current is increased from the low level current to the high level current to regenerate the arc. The value of the high-level current and / or the rising slope is changed according to the progress of the constriction when the reference time is reached. When the degree of progress of the constriction is advanced, even if the high level current is a relatively small value, the arc regeneration can be led at an early stage. On the other hand, when the progress of the constriction is delayed, the arc cannot be regenerated unless the high level current is a relatively large value. A case in which the elapsed time from the point of detection of the squeezing is longer than the reference time and a high level current is applied occurs several times per second, depending on the welding conditions. Since the progress of the constriction at the time when the reference time is reached varies, the value of the high level current also changes correspondingly. As a result, the current value when the arc is regenerated also changes variously, and the average value is smaller than that of the prior art. Therefore, in the present embodiment, even when the elapsed time from the point of detection of the squeezing is equal to or longer than the reference time, the arc can be smoothly regenerated, and the amount of large spatter generated can be reduced as a total amount. Can do.

  In the above description, the case where the control for detecting the constriction is prohibited when the high-level current is applied has been described. However, the squeezing detection control may be performed even when a high level current is applied. That is, in FIG. 2, when a constriction is detected during energization of a high level current from time t22, the welding current Iw is suddenly reduced again to a low level current value as after time t2. However, since the elapsed time from the first squeezing detection time exceeds the reference time and a high level current is applied, the squeezing progress is not smooth. Therefore, when a constriction is normally detected when a high level current is applied and the welding current is rapidly reduced, the probability is not so high. However, there is a certain effect of reducing spatter.

DESCRIPTION OF SYMBOLS 1 Welding wire 1a Droplet 1b Constriction 2 Base material 2a Molten pool 3 Arc 4 Welding torch 5 Feed roll CM Current comparison circuit Cm Current comparison signal CT Elapsed time discrimination circuit Ct Elapsed time discrimination signal DR Drive circuit Dr 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 Feeding control signal Ia Current value ID when arc is regenerated Current detection circuit Id Current detection signal Ih High level current IHR High level current setting Circuit Ihr High level current setting signal Il Low level current ILR Low level current setting circuit Ilr Low level current setting signal IR Current setting circuit Ir Current setting signal Iw Welding current ND Constriction detection circuit Nd Constriction detection signal NS Constriction progress detection circuit Ns Constriction Progress signal PM Power supply main circuit PS Welding power supply R Current reducing resistor S Tilt SD Short-circuit / arc discrimination circuit Sd Short-circuit / arc discrimination signal SR Rising slope setting circuit Sr Rising slope setting signal SW Control switching circuit t Elapsed time Ta Arc period Tn Neck detection time TR Transistor Ts Short-circuit period Tt Reference time TTR Reference time setting circuit Ttr Reference time setting signal VD Voltage detection circuit Vd Voltage detection signal VR Voltage setting circuit Vr Voltage setting signal Vs Short circuit voltage value Vta Short circuit / arc discriminating value VTN Constriction detection reference value setting circuit Vtn Constriction detection reference value (signal)
Vw Welding voltage WM Feed motor ΔV Voltage rise value

Claims (2)

In consumable electrode arc welding in which the arc generation state and the short-circuit state are repeated between the welding wire and the base metal, the constriction of the droplet, which is a precursor to the occurrence of the arc again from the short-circuit state, is detected. In the constriction detection control method of consumable electrode arc welding, which reduces the welding current flowing from the short circuit load to the regenerated arc at a low level current state,
When the elapsed time from the necking detection time reaches a predetermined reference time before the arc is regenerated, the welding current is increased from the low level current to the high level current to regenerate the arc. The level current value and / or rising slope is changed according to the progress of the constriction when the reference time is reached.
A constriction detection control method for consumable electrode arc welding. The progress of the constriction is detected by a change in voltage value or resistance value between the welding wire and the base material,
The constriction detection control method of consumable electrode arc welding according to claim 1.

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