JP6245734B2 - Welding current control method during short circuit period - Google Patents

Description

  The present invention relates to a welding current control method for a short-circuit period for improving a droplet transfer state in consumable electrode arc welding in which a short-circuit period and an arc period are alternately repeated.

  Consumable electrode arc welding that feeds the welding wire at a constant speed and performs welding using carbon dioxide gas, argon gas, mixed gas of carbon dioxide gas and argon gas, etc. as the shielding gas can obtain high quality. It is widely used because it can be easily automated. In this arc welding, welding is often performed by alternately repeating a short-circuit period and an arc period between a welding wire and a base material. During the arc period, the tip of the welding wire melts to form droplets, and during the short circuit period, the droplets move to the molten pool. In order to form a good weld bead and reduce the amount of spatter generated, it is important to control the welding current during the short-circuit period to an appropriate value so that droplet transfer can be performed smoothly. Hereinafter, the welding current control method in the short circuit period in the prior art will be described (for example, see Patent Document 1).

  FIG. 9 is a voltage / current waveform diagram of consumable electrode arc welding in the prior art. FIG. 4A shows the change over time of the welding voltage Vw applied between the welding wire and the base material, and FIG. 4B shows the change over time of the welding current Iw energized from the welding wire to the base material. . Hereinafter, description will be given with reference to FIG.

  Time t1 to t2 is a short circuit period Ts, time t2 to t3 is an arc period Ta, and time t3 to t4 is a short circuit period Ts. The short circuit period Ts and the arc period Ta are alternately repeated.

  When the short circuit is released at time t2 and the arc is regenerated, the welding voltage Vw rapidly rises to an arc voltage value of about several tens of volts as shown in FIG. As shown in FIG. 5B, the welding current Iw decreases slightly until the next short-circuit occurs after it suddenly decreases slightly when the arc is regenerated.

  When the droplet formed at the tip of the welding wire in the arc period Ta comes into contact with the molten pool at time t3, a short-circuit state is established. In the short circuit state, the welding voltage Vw rapidly drops to a short circuit voltage value of about several volts as shown in FIG. As shown in FIG. 5B, the welding current Iw decreases to a predetermined initial current value Ii and maintains that value during a predetermined initial period Ti from time t3 to t31. When the initial period Ti elapses at time t31, the welding current Iw increases at a predetermined increase rate (increase rate, inclination) K as shown in FIG. 5B, and the welding current Iw reaches a predetermined peak value at time t32. When Ip is reached, the value is maintained until time t4 when the arc is regenerated.

  Next, the transition state of the droplets will be described. When the arc is regenerated at time t2, since the droplet has been transferred, no droplet is formed at the tip of the welding wire. As the arc period Ta proceeds, the tip of the welding wire is gradually melted by heat from the arc and Joule heat to form droplets. The reason why the welding current Iw is maintained at a small initial current value Ii during the initial period Ti from the time when the short circuit occurs is to make the contact state between the droplet and the molten pool more reliable. Immediately after the occurrence of the short-circuit, a part of the bottom of the droplet is in contact with the molten pool. If the welding current Iw is large in this state, the contact state is released without the droplet moving and the arc is generated. It will occur again, and the stable droplet transfer state will be inhibited. At time t31 when the initial period Ti ends, the droplet forms a stable bridge with the molten pool. By increasing the welding current Iw from this time t31, a pinch force is applied to the bridge, causing a constriction in the upper part of the bridge and smoothly transferring the droplets to the molten pool.

  In order to stabilize the droplet transfer state, it is important to optimize the setting of the rising speed K and the peak value Ip of the welding current Iw during the short-circuit period Ts. If the ascending speed K and the peak value Ip are smaller than the appropriate values, the pinch force acting on the bridge becomes weak, so the time for transferring the droplets becomes long and the welding state becomes unstable. On the contrary, when the rising speed K and the peak value Ip are larger than appropriate values, the amount of spatter generated increases. Therefore, the rising speed K and the peak value Ip are set to appropriate values according to the type of shield gas, the material of the welding wire, the diameter, the feeding speed, and the like.

  By the way, during welding, the formation of droplets is caused by various disturbances such as fluctuations in the feeding speed, irregular movement of the molten pool, gas ejection from the molten pool, fluctuations in the welding position, fluctuations in the torch height, etc. The state will vary. If the formation state of the droplets varies, the size of the droplets at the time when the short circuit occurs varies. When the droplet size is smaller or larger than the appropriate size, in order to secure a stable droplet transfer state and reduce the amount of spatter generated, the above-described rising speed K and peak value Ip Needs to be optimized according to the droplet size.

  In the invention of Patent Document 2, for this optimization, the rising speed K of the short circuit current is changed according to the time length of the short circuit period or the arc period.

Japanese Patent Publication No. 4-407 JP 2012-76131 A

  When the short-circuit period is less than the predetermined time, the short-circuit is distinguished as the micro short-circuit, and the short-circuit period is determined as the normal short-circuit, and when the average value of the welding current is less than 180 A and the welding speed is relatively slow, the normal short-circuit Only occurs, and micro short-circuits hardly occur. In such a case, since the length of the short-circuit period and the arc period correlates with the droplet size at the time of occurrence of the short-circuit, the droplet transfer state can be stabilized by the method of Patent Document 2.

  However, when the average value of the welding current is 180 A or more, or when the welding speed is relatively fast, the normal short circuit and the micro short circuit are mixedly generated. In such a case, the lengths of the short circuit period and the arc period are not correlated with the droplet size when the short circuit occurs. As a result, the method disclosed in Patent Document 2 cannot stabilize the droplet transfer state.

  Therefore, the present invention is to maintain a stable droplet transfer state even if the droplet size at the occurrence of a short circuit varies due to disturbance during welding in a welding condition where a normal short circuit and a micro short circuit occur together. And it aims at providing the welding current control method of the short circuit period which can also reduce the generation amount of a sputter | spatter.

In order to solve the above-described problems, the invention of claim 1
In the arc welding in which the welding wire is fed and the short circuit period and the arc period are alternately repeated, the welding current control method of the short circuit period in which the welding current is increased to the peak value during the short circuit period,
A short circuit in which the short circuit period is a predetermined first reference time or more is defined as a normal short circuit, and a short circuit that is less than the first reference time is defined as a micro short circuit,
An index that correlates with the melting amount of the welding wire during a normal short-circuit interval from the time when the previous normal short circuit is released to the time when the current normal short circuit occurs is detected, and the current normal is detected according to this index. Changing the rate of increase of the welding current and / or the peak value in a short circuit;
When the period of the normal short circuit is equal to or longer than a second reference time set to a value longer than the first reference time, the welding current is further increased from the peak value, and the second reference is determined according to the index. Change the time,
It is the welding current control method of the short circuit period characterized by this.

In the invention of claim 2, the index is a time length of the normal short-circuit interval period .
The welding current control method for a short circuit period according to claim 1.

In the invention of claim 3, the index is an integral value of the welding current during the normal short-circuit interval period.
The welding current control method for a short circuit period according to claim 1.

  According to the present invention, when the rising speed and / or peak value is optimized according to an index that correlates with the melting amount of the welding wire during the normal short-circuit interval, the droplet transfer state can be stabilized, and Sputter generation can also be reduced. For this reason, in the present invention, in a welding condition in which a normal short circuit and a micro short circuit occur together, even if the droplet size at the time of the short circuit varies due to disturbance during welding, the droplet transfer state is stabilized. And the amount of spatter generated can be reduced.

It is a voltage and current waveform diagram for demonstrating the welding current control method of the short circuit period concerning Embodiment 1 of this invention. In Embodiment 1, it is an example of the relationship diagram of time length Tb (ms) of normal short circuit interval period, ascent speed K (A / ms), and peak value Ip (A). In Embodiment 1, it is an example of the relationship figure of integral value Si (A * ms) of welding current Iw in normal short circuit interval period Tb, ascent rate K (A / ms), and peak value Ip (A). It is a block diagram of the welding power supply for implementing the welding current control method of the short circuit period which concerns on Embodiment 1 of this invention. It is a voltage and current waveform diagram for demonstrating the welding current control method of the short circuit period which concerns on Embodiment 2 of this invention. In Embodiment 2, it is an example of the related figure of time length Tb (ms) of the normal short circuit interval period, and 2nd reference time Tc (ms). In Embodiment 2, it is an example of the related figure of integral value Si (A * ms) of welding current in 2nd standard time Tc (ms) in normal short circuit interval period Tb. It is a block diagram of the welding power source for enforcing the welding current control method of the short circuit period concerning Embodiment 2 of this invention. It is a voltage and electric current waveform diagram of consumable electrode arc welding in a prior art.

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

[Embodiment 1]
FIG. 1 is a voltage / current waveform diagram for explaining a welding current control method during a short-circuit period according to Embodiment 1 of the present invention. FIG. 4A shows the time change of the welding voltage Vw, and FIG. 4B shows the time change of the welding current Iw. This figure corresponds to FIG. 9 described above, and the description of the same operation will not be repeated. Hereinafter, description will be given with reference to FIG.

  The normal short circuit and the micro short circuit used in the following description are defined. The normal short circuit is a short circuit in which the length of the short circuit period is equal to or longer than a predetermined first reference time Tf, and the droplet at the wire tip moves to the molten pool during the short circuit period. On the other hand, the micro short circuit is a short circuit in which the length of the short circuit period is less than the first reference time Tf, and the droplet at the wire tip does not move to the molten pool but remains as it is at the wire tip. The first reference time Tf is set in a range of about 0.5 to 1.5 MS. The first reference time Tf is set to an appropriate value by experiment as a threshold value with or without droplet transfer depending on the material, diameter, type of shield gas, and the like of the welding wire 1.

  In the figure, a normal short circuit occurs at times t1 to t2, a micro short circuit occurs at times t21 to t22, a micro short circuit occurs at times t23 to t24, and a normal short circuit occurs at times t3 to t4. doing. That is, in FIG. 9, in the above-described FIG. 9, during the period between the previous normal short-circuit release time t2 and the current normal short-circuit occurrence time t3 (hereinafter referred to as the normal short-circuit interval period Tb), This is a case where a short-circuit occurs.

  During the normal short-circuit period from time t1 to t2 and from time t3 to t4, as shown in FIG. 5A, the welding voltage Vw becomes a short-circuit voltage value of about several volts, and as shown in FIG. The welding current Iw becomes a predetermined initial current value Ii during a predetermined initial period Ti, thereafter increases at a predetermined rising speed K, and maintains that value when reaching a predetermined peak value Ip. The initial period Ti is set to the first reference time Tf, and the initial current value Ii is set to about 50A.

  As shown in the same figure (A), the welding voltage Vw becomes a short circuit voltage value of about several volts during the period of the micro short circuit of the time t21 to t22 and the time t23 to t24, and as shown in the same figure (B), The welding current Iw becomes the initial current value Ii because the arc is regenerated during the initial period Ti.

  Here, in order to clarify the cause of the variation in droplet size at the time when the normal short circuit occurred, the relationship between the occurrence state of the short circuit and the droplet size was investigated. As a result, it was found that the droplet size increases when a micro short circuit occurs during the normal short circuit interval period Tb. Furthermore, the droplet size increased as the number of micro short-circuits increased. This is because, as the number of occurrences of micro short-circuits increases, the normal short-circuit interval period Tb becomes longer, and the droplet does not move in the micro short-circuit, so the amount of melt at the wire tip increases and the droplet size increases. .

  In the prior art, the droplet size at the time when the normal short-circuit occurred depending on the period between the time when the previous short-circuit was released and the time when this normal short-circuit occurred (previous arc period), regardless of whether it is a normal short circuit or a micro short circuit. Was detected. That is, in the same figure, the droplet size at the occurrence time t3 of the normal short-circuit is detected by the period (time t24 to t3) between the previous short-circuit release time t24 and the current normal short-circuit occurrence time t3. It was. However, as described above, the immediately preceding arc period does not correlate with the droplet size when the previous short circuit is a micro short circuit.

  On the other hand, in the present embodiment, the amount of welding wire melted during the normal short-circuit interval Tb from the time when the previous normal short circuit is released to the time when the current normal short circuit occurs is ignored, ignoring the micro short circuit. Usually, the droplet size at the time of occurrence of a short circuit is accurately detected by detecting correlated indicators. As an index correlated with the melting amount of the welding wire, the time length of the normal short-circuit interval period Tb or the integrated value of the welding current during the normal short-circuit interval period Tb is used. As the time length of the normal short-circuit interval period Tb and the integrated value of the welding current during the normal short-circuit interval period Tb increase, the melting amount of the wire tip increases and the wire tip particle size increases.

  In order to stabilize the droplet transfer state even if the droplet size varies at the time when the normal short circuit occurs, it is necessary to change the rising speed K and / or the peak value Ip in conjunction with each other as described above. . That is, as the index correlating with the amount of melting of the welding wire during the above-described normal short-circuit interval Tb increases, the rising speed K and / or the peak value Ip may be increased.

  FIG. 2 is an example of a relationship diagram between the time length Tb (ms) of the normal short-circuit interval period, the rising speed K (A / ms), and the peak value Ip (A). The horizontal axis indicates the time length Tb of the normal short-circuit interval period, which is in the range of 20 to 40 ms. The left vertical axis shows the ascending speed K and is in the range of 0 to 500 A / ms. The right vertical axis indicates the peak value Ip, which is in the range of 300 to 600A. The figure shows the case where the welding wire is made of steel, the diameter is 1.2 MM, the type of shielding gas is 100% carbon dioxide, and the welding current average value is 200A.

  The rising speed K shown by the solid line is 200 A / ms when Tb ≦ 25 ms, increases from 200 A / ms to 400 A / ms as Tb increases from 25 ms to 35 ms, and 400 A / ms when Tb ≧ 35 ms. ms. The peak value Ip indicated by the broken line is 400 A when Tb ≦ 25 ms, increases from 400 A to 500 A as Tb increases from 25 ms to 35 ms, and becomes 500 A when Tb ≧ 35 ms.

  The relationship as shown in the figure is set for each welding condition such as the material of the welding wire, the diameter, the type of shield gas, and the welding current average value (feeding speed).

  FIG. 3 is an example of a relationship diagram of the integrated value Si (A · ms), the rising speed K (A / ms), and the peak value Ip (A) of the welding current Iw during the normal short-circuit interval Tb. The horizontal axis represents the integrated value Si, which is in the range of 4000 to 8000 A · ms. The left vertical axis shows the ascending speed K and is in the range of 0 to 500 A / ms. The right vertical axis indicates the peak value Ip, which is in the range of 300 to 600A. The figure shows the case where the welding wire is made of steel, the diameter is 1.2 MM, the type of shielding gas is 100% carbon dioxide, and the welding current average value is 200A.

  The rising speed K indicated by the solid line is 200 A / ms when Si ≦ 5000 A · ms, and increases from 200 A / ms to 400 A / ms as Si increases from 5000 A · ms to 7000 A · ms, and Si ≧ At 7000 A · ms, it is 400 A / ms. The peak value Ip indicated by the broken line is 400 A when Si ≦ 5000 A · ms, and increases from 400 A to 500 A as Si increases from 5000 A · ms to 7000 A · ms, and when Si ≧ 7000 A · ms. 500A.

  The relationship as shown in the figure is set for each welding condition such as the material of the welding wire, the diameter, the type of shield gas, and the welding current average value (feeding speed).

  FIG. 4 is a block diagram of a welding power source for carrying out the above-described welding current control method during the short-circuit period 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 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 the voltage to an appropriate voltage value, a secondary rectifier that rectifies the stepped-down high-frequency alternating current to direct current, a reactor that smoothes the rectified direct current, and pulse width modulation control using the above error amplification signal Ea as input. A modulation circuit that outputs a signal and a drive circuit that drives the switching element of the inverter circuit with the modulation signal as an input are provided.

  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 voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the welding voltage Vw (arc voltage) during the arc period Ta.

  The short circuit determination circuit SD receives the voltage detection signal Vd as described above, and outputs a short circuit determination signal Sd having a high level when this value is less than a predetermined threshold value. When the short circuit determination signal Sd is at a high level, it is a short circuit period, and when it is at a low level, it is an arc period. The threshold is set to about 10V.

The first reference time setting circuit TFR outputs a predetermined first reference time setting signal Tfr. The index detection circuit HD receives the first reference time setting signal Tfr, the short circuit determination signal Sd, and the current detection signal Id, performs the following processing, and outputs the index detection signal Hd.
1) When the short circuit determination signal Sd changes to a high level (short circuit), it is determined that a normal short circuit has occurred if the period length of the high level is equal to or greater than the value of the first reference time setting signal Tfr. Determines that a small short circuit has occurred.
2) After determining the occurrence of the normal short circuit, when the short circuit determination signal Sd is changed to the low level and it is determined that the normal short circuit is released, the time measurement of the normal short circuit interval period and the integration of the current detection signal Id are started. When the occurrence of a short circuit is determined, the timing and integration are stopped.
3) When the occurrence of the normal short circuit is determined, the above measured value is set as the time length Tb of the normal short circuit interval period, and the above integrated value is set as the integrated value Si of the welding current during the normal short circuit interval period.
4) Either the time length Tb of the normal short-circuit interval period or the integration value Si of the welding current during the normal short-circuit interval period is selected and output as the index detection signal Hd.

  The initial period setting circuit TIR receives the first reference time setting signal Tfr, and outputs an initial period setting signal Tir that is predetermined to the same value. The initial current setting circuit IIR outputs a predetermined initial current setting signal Iir.

  The ascending speed setting circuit KR receives the index detection signal Hd as described above and outputs the ascending speed setting signal Kr calculated by a predetermined function as described above with reference to FIG. 2 or FIG.

  The peak value setting circuit IPR receives the index detection signal Hd as described above and outputs the peak value setting signal Ipr calculated by a predetermined function as described above with reference to FIG.

The current setting circuit IR receives the initial period setting signal Tir, the initial current setting signal Iir, the rising speed setting signal Kr, the peak value setting signal Ipr, and the short circuit determination signal Sd as follows. Processing is performed to output a current setting signal Ir.
1) The value of the initial current setting signal Iir is output as the current setting signal Ir during a period determined by the initial period setting signal Tir from the time when the short circuit determination signal Sd changes to the High level (short circuit).
2) Thereafter, the value of the current setting signal Ir is increased from the value of the initial current setting signal Iir at a rising speed determined by the rising speed setting signal Kr.
3) When the value of the current setting signal Ir becomes equal to the value of the peak value setting signal Ipr, the value of the peak value setting signal Ipr is output as the current setting signal Ir. This state is maintained until the next short circuit occurs.

  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 determination signal Sd, and when the short circuit determination signal Sd is at a high level (short circuit), the current 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.

  According to the first embodiment described above, the index (normal short circuit interval period) is correlated with the melting amount of the welding wire during the normal short circuit interval period from the time when the previous normal short circuit is released to the time when the current normal short circuit occurs. The time length or the integration value of the welding current) is detected, and the rising speed and / or peak value of the welding current in this normal short circuit is changed according to this index. The larger this index, the larger the droplet size at the time when a normal short circuit occurs. Therefore, if the rising speed and / or peak value is optimized according to this index, the droplet transfer state can be stabilized and the amount of spatter generated can be reduced. For this reason, in the present embodiment, in a welding condition in which a normal short circuit and a micro short circuit are mixed, even if the droplet size at the occurrence of the short circuit varies due to disturbance during welding, the droplet transfer state is maintained. It can be kept stable and the amount of spatter generated can be reduced.

[Embodiment 2]
In the second embodiment, in addition to the first embodiment, when the period of the normal short circuit becomes equal to or longer than the second reference time Tc, the welding current Iw is further increased from the peak value Ip, and according to the index detection signal Hd. To change the second reference time Tc.

  FIG. 5 is a voltage / current waveform diagram for explaining the welding current control method during the short-circuit period according to Embodiment 2 of the present invention. FIG. 4A shows the time change of the welding voltage Vw, and FIG. 4B shows the time change of the welding current Iw. This figure corresponds to FIG. 1 described above, and the operations other than the period from time t33 to t4 are the same, and therefore description thereof will not be repeated. Hereinafter, the operation during the period from time t33 to t4 will be described with reference to FIG.

  During the normal short-circuit period from time t3 to t4, the welding voltage Vw becomes a short-circuit voltage value of about several volts as shown in FIG. Then, as shown in FIG. 5B, the welding current Iw becomes the initial current value Ii during the initial period Ti from time t3 to t31, thereafter increases at the rising speed K, and reaches the peak value Ip at time t32. Then, this value is maintained, and at time t33 when the length of the short-circuit period reaches a predetermined second reference time Tc, the value is increased to the short-circuit forced release current value Ik, and this value is maintained until time t4 when the arc is regenerated. The first reference time Tb <the second reference time Tc, and the peak value Ip <the short-circuit forced release current value Ik. The short circuit forced release current value Ik is set to about 600 to 700A.

  The reason why the welding current Iw is increased to the short-circuit forced release current value Ik is as follows. That is, if the arc is not regenerated even if the short-circuit period exceeds the second reference time Tc, the short-circuit period may be several tens of ms and the welded state may become unstable if left as it is. This is because when the short-circuit period exceeds the second reference time Tc, it is necessary to further increase the welding current Iw to cancel the short-circuit as soon as possible to regenerate the arc.

  Also for the second reference time Tc, by changing the value according to the index detection signal Hd, the droplet transfer state can be stabilized and the amount of spatter generated can be reduced.

  FIG. 6 is an example of a relationship diagram between the time length Tb (ms) of the normal short-circuit interval period and the second reference time Tc (ms). The horizontal axis indicates the time length Tb of the normal short-circuit interval period, which is in the range of 20 to 40 ms. The vertical axis represents the second reference time Tc and is in the range of 0 to 10 ms. The figure shows the case where the welding wire is made of steel, the diameter is 1.2 MM, the type of shielding gas is 100% carbon dioxide, and the welding current average value is 200A.

  The second reference time Tc is 8 ms when Tb ≦ 25 ms, decreases from 8 ms to 5 ms as Tb increases from 25 ms to 35 ms, and 5 ms when Tb ≧ 35 ms.

  The relationship as shown in the figure is set for each welding condition such as the material of the welding wire, the diameter, the type of shield gas, and the welding current average value (feeding speed).

  FIG. 7 is an example of a relationship diagram between the integrated value Si (A · ms) of the welding current and the second reference time Tc (ms) during the normal short-circuit interval period Tb. The horizontal axis represents the integrated value Si, which is in the range of 4000 to 8000 A · ms. The vertical axis represents the second reference time Tc and is in the range of 0 to 10 ms. The figure shows the case where the welding wire is made of steel, the diameter is 1.2 MM, the type of shielding gas is 100% carbon dioxide, and the welding current average value is 200A.

  The second reference time Tc is 8 ms when Si ≦ 5000 A · ms, decreases from 8 ms to 5 ms as Si increases from 5000 A · ms to 7000 A · ms, and 5 ms when Si ≧ 7000 A · ms. It becomes.

  The relationship as shown in the figure is set for each welding condition such as the material of the welding wire, the diameter, the type of shield gas, and the welding current average value (feeding speed).

  FIG. 8 is a block diagram of a welding power source for carrying out the above-described welding current control method during the short-circuit period according to Embodiment 2 of the present invention. This figure corresponds to FIG. 4 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 second reference time setting circuit TCR and a short-circuit forced release current setting circuit IKR to FIG. 4 and replacing the current setting circuit IR of FIG. 4 with a second current setting circuit IR2. Hereinafter, these blocks will be described with reference to FIG.

  The second reference time setting circuit TCR receives the index detection signal Hd and outputs the second reference time setting signal Tcr calculated by a predetermined function as described above with reference to FIG. 6 or FIG.

  The short-circuit forced release current setting circuit IKR outputs a predetermined short-circuit symbiosis release current setting signal Ikr.

The second current setting circuit IR2 includes an initial period setting signal Tir, an initial current setting signal Iir, an ascending speed setting signal Kr, a peak value setting signal Ipr, a short circuit determination signal Sd, the second reference time setting signal Tcr, and the short circuit. The following process is performed with the forced release current setting signal Ikr as an input, and the current setting signal Ir is output.
1) The value of the initial current setting signal Iir is output as the current setting signal Ir during a period determined by the initial period setting signal Tir from the time when the short circuit determination signal Sd changes to the High level (short circuit).
2) Thereafter, the value of the current setting signal Ir is increased from the value of the initial current setting signal Iir at a rising speed determined by the rising speed setting signal Kr.
3) When the value of the current setting signal Ir becomes equal to the value of the peak value setting signal Ipr, the value of the peak value setting signal Ipr is output as the current setting signal Ir.
4) When the elapsed time from when the short circuit determination signal Sd changes to the High level reaches the value of the second reference time setting signal Tcr, the value of the short circuit forced release current setting signal Ikr is output as the current setting signal Ir. . This state is maintained until the next short circuit occurs.

  According to the second embodiment described above, when the normal short-circuit period is equal to or longer than the second reference time, the welding current is further increased from the peak value, and is correlated with the amount of melting of the welding wire during the normal short-circuit interval period. The second reference time is changed according to the index. Thereby, in addition to the effect of the first embodiment, even when the short circuit period becomes long and it is necessary to forcibly cancel the short circuit, the second reference time for shifting to the compulsory cancellation is set to the welding during the normal short circuit interval period. Since the optimization is made in accordance with the index correlating with the melting amount of the wire, it is possible to suppress the droplet transfer state from becoming unstable.

  In the above, the second reference time Tc changes according to the index, but the short-circuit forced release current Ik may be changed.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal HD Index detection circuit Hd Index detection signal ID Current detection circuit Id Current detection Signal Ii Initial current value IIR Initial current setting circuit Iir Initial current setting signal Ik Short-circuit forced release current IKR Short-circuit forced release current setting circuit Ikr Short-circuit forced release current setting signal Ip Peak value IPR Peak value setting circuit Ipr Peak value setting signal IR Current setting Circuit Ir Current setting signal IR2 Second current setting circuit Iw Welding current K Rising speed KR Rising speed setting circuit Kr Rising speed setting signal PM Power supply main circuit SD Short circuit determination circuit Sd Short circuit determination signal Si Integral value SW Control switching circuit Ta Arc period Tb Normal short-circuit interval period Tc Second reference time TCR Second reference time setting Path Tcr Second reference time setting signal Tf First reference time TFR First reference time setting circuit Tfr First reference time setting signal Ti Initial period TIR Initial period setting circuit Tir Initial period setting signal Ts Short circuit period VD Voltage detection circuit Vd Voltage detection Signal VR Voltage setting circuit Vr Voltage setting signal Vw Welding voltage

Claims (3)

In the arc welding in which the welding wire is fed and the short circuit period and the arc period are alternately repeated, the welding current control method of the short circuit period in which the welding current is increased to the peak value during the short circuit period,
A short circuit in which the short circuit period is a predetermined first reference time or more is defined as a normal short circuit, and a short circuit that is less than the first reference time is defined as a micro short circuit,
An index that correlates with the melting amount of the welding wire during a normal short-circuit interval from the time when the previous normal short circuit is released to the time when the current normal short circuit occurs is detected, and the current normal is detected according to this index. Changing the rate of increase of the welding current and / or the peak value in a short circuit;
When the period of the normal short circuit is equal to or longer than a second reference time set to a value longer than the first reference time, the welding current is further increased from the peak value, and the second reference is determined according to the index. Change the time,
A method for controlling a welding current during a short-circuit period. The indicator is a time length of the normal short-circuit interval period ;
The welding current control method for a short-circuit period according to claim 1. The indicator is an integral value of the welding current during the normal short-circuit interval;
The welding current control method for a short-circuit period according to claim 1.

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