JP2011073022A - Carbon dioxide pulsed arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a high quality welding with less spatters by stabilizing formation and separation of droplets in consumable electrode type carbon dioxide pulsed arc welding. <P>SOLUTION: In the carbon dioxide pulsed arc welding method in which welding is performed by repeating, as one pulse period Tpb, a peak period Tp for energizing peak current Ip and a base period Tb for energizing base current Ib, the droplets of desired size are formed at the tip end of a welding wire by vibrating the peak current Ip by amplitude Ws and vibration period Ts during the peak period Tp, and the formed droplets are smoothly transferred to a molten pool by short circuiting transfer during the base period Tb. As a result, the droplets formed during the peak period Tp are short-circuiting-transferred during the base period Tb, materializing a state of one pulse period-one droplet transfer. Accordingly, welding with less spatters is attained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a carbon dioxide pulse arc welding method for performing stable droplet transfer in consumable electrode type pulse arc welding using a shield gas containing carbon dioxide as a main component.

  Consumable electrode type pulse arc welding using a shielding gas mainly composed of argon gas is widely used. As the shielding gas mainly composed of argon gas, when the base material is a steel material, 20% by volume carbon dioxide gas + 80% by volume argon gas is used (mag pulse welding), and when the base material is an aluminum material. 100 vol% argon gas is used (Migpulse welding). In the pulse arc welding using such a shielding gas mainly composed of argon gas, the droplet transfer becomes a fine particle as much as the diameter of the welding wire and becomes a spray transfer state that is periodically performed stably. Good welding with less spatter generation can be performed. Below, the pulse arc welding using the shielding gas which has argon gas as a main component is demonstrated.

  FIG. 4 is a general current / voltage waveform diagram of pulse arc welding using a shield gas containing argon gas as a main component. FIG. 4A shows the change over time of the welding current Iw for energizing the arc, and FIG. 4B shows the change over time of the welding voltage Vw between the welding wire and the base material. Hereinafter, a description will be given with reference to FIG.

  During the peak period Tp from time t1 to t2, a peak current Ip greater than or equal to the critical current value is applied to form and transfer droplets at the tip of the welding wire as shown in FIG. ), A peak voltage Vp proportional to the arc length is applied between the welding wire and the base material.

  During the base period Tb from time t2 to t3, as shown in FIG. 5A, the base current Ib having a small current value is energized to prevent the formation of droplets, as shown in FIG. In addition, a base voltage Vb is applied. The welding is performed by repeating the period from time t1 to t3 as the pulse period Tpb.

  In order to perform good pulse arc welding, it is important to maintain the arc length at an appropriate value. In order to maintain the arc length at an appropriate value, the following output control (arc length control) is performed. The arc length is substantially proportional to the welding voltage average value Vav indicated by a broken line in FIG. For this purpose, the welding voltage average value Vav is detected, and the output for changing the welding current average value Iav indicated by the broken line in FIG. 5A so that the detected value becomes equal to the welding voltage set value corresponding to the appropriate arc length. Take control. When the welding voltage average value Vav is larger than the welding voltage set value, the arc length is longer than the appropriate value. Therefore, the welding current average value Iav is decreased to reduce the wire melting rate and shorten the arc length. To do. Conversely, when the welding voltage average value Vav is smaller than the welding voltage set value, the arc length is shorter than the appropriate value, so the welding current average value Iav is increased to increase the wire melting rate and the arc length is increased. To be. In general, a value obtained by smoothing the welding voltage Vw is often used as the welding voltage average value Vav.

  In the above description, frequency modulation control and pulse width modulation control are mainly used as the output control of the welding power source for changing the welding current average value Iav. In the frequency modulation control, the peak current Ip, the base current Ib, and the peak period Tp are fixed to predetermined values, and the length of the base period Tb is controlled so that the welding voltage average value Vav becomes equal to the welding voltage setting value. Since changing the base period Tb changes the pulse period Tpb, this method is called frequency modulation control. In the pulse width modulation control, the peak current Ip, the base current Ib, and the pulse period Tpb are fixed to predetermined values, and the length of the peak period Tp is controlled so that the welding voltage average value Vav becomes equal to the welding voltage setting value. The

  Next, droplet transfer will be described with reference to FIG. By applying the peak current Ip, the tip of the welding wire is melted to form a droplet. At this time, since the shielding gas containing argon gas as a main component is used, the anode points of the arc are widely distributed throughout the droplet without concentrating on the droplet. For this reason, no pushing force acts on the droplet. When the peak current Ip is applied to the formed droplet, an electromagnetic pinch force acts on the droplet to cause constriction. And before and after the end of the peak period Tp (immediately before the end, at the end or immediately after the end), the droplets are detached and move to the molten pool. The combination of the peak current Ip and the peak period Tp is called a unit pulse condition, and is set to a value at which droplets having the diameter of the welding wire are formed and detached. Therefore, the droplets are sprayed as a fine particle about the diameter of the welding wire every peak period Tp. This state is referred to as a 1 pulse 1 droplet transfer state. In this way, welding with very little spatter generation becomes possible.

  As described above, in the pulse arc welding using the shield gas containing argon gas as a main component, a stable spray transfer state in which one pulse per droplet transfer occurs. Here, since the cost of argon gas is higher than that of carbon dioxide, attempts have been made to reduce the cost of shielding gas by decreasing the proportion of argon gas and increasing the proportion of carbon dioxide. . However, in the mixed gas of carbon dioxide gas and argon gas, when the ratio of carbon dioxide gas exceeds 30% by volume, stable spray transfer becomes gradually difficult for the reason described below. In particular, when a shield gas containing carbon dioxide as a main component with a carbon dioxide ratio exceeding 50% by volume is used, a stable spray transfer state is not achieved, and large spatters are generated. In the following description, when it is described as a shield gas containing carbon dioxide as a main component, it means a mixed gas in which the ratio of carbon dioxide exceeds 50% by volume. When a shield gas containing carbon dioxide as a main component is used, the anode point of the arc is concentrated on the lowest part of the droplet when the peak current Ip is applied. This is because the potential gradient of carbon dioxide gas is larger than that of argon gas, so that the action of minimizing the arc length works. As a result, the temperature of the anode point becomes extremely high, the metal vapor is blown out, and acts on the droplet as a pushing force. That is, when the peak current Ip is energized, a droplet is formed and this pushing force acts, and the droplet is not easily detached. In this state, in order to forcibly detach the droplet, it is necessary to make the peak period Tp 3-5 times longer than the normal value, grow the droplet large, and detach by gravity. . However, if this is done, the droplets will be separated into large lumps about several times the diameter of the welding wire and large spatter will be generated. Furthermore, this large droplet will move randomly without synchronizing with the energization of the peak current Ip, the welding state becomes unstable, and the welding quality also deteriorates. In order to solve the above-described problems in pulse arc welding using a shielding gas containing carbon dioxide as a main component (hereinafter referred to as carbon dioxide pulse arc welding), the following conventional techniques have been proposed.

  In the invention of Patent Document 1, the first half period of the peak current Ip is set to a larger value than the second half period, and is stepped downward. By doing so, droplets are formed in the latter half period of the peak current Ip, the droplets are shaped in the subsequent base period Tb, and the droplets are transferred in the first half period of the subsequent peak current Ip. Further, in the inventions of Patent Documents 2 to 4, the peak current Ip is energized as a plurality of peak current groups to stabilize the formation of droplets and facilitate the transfer.

JP 60-56486 A JP-A 61-17369 JP-A-1-254385 JP 2007-237270 A JP 2006-116546 A

  As described above, various proposals as shown in Patent Documents 1 to 4 have been made in order to improve formation and separation of droplets in carbon dioxide pulse arc welding. However, even at the present time, it cannot be said that carbon dioxide pulse arc welding has been put into practical use, and a welding apparatus for carbon dioxide pulse arc welding has not been sold. This indicates that there is still a problem even if the improvements proposed in Patent Documents 1 to 4 are implemented.

  According to the invention of Patent Literature 1, although the droplet transfer probability is increased by the peak current in the first half period, the droplet transfer still frequently occurs randomly without being synchronized with the peak current. This increases the peak current value in the first half period to form a constriction at the top of the droplet to promote separation, but on the other hand, the push-up force also increases so that the droplet does not reliably separate. Because. Moreover, according to invention of patent documents 2-4, formation of a droplet can be made smooth by energizing a peak current as a plurality of peak current groups. This is because the pushing force acting on the droplets can be dispersed when the plurality of peak current groups are energized rather than when the continuous peak current is energized, so that the formation of the droplets becomes smooth. However, in order to release the formed droplet by the peak current, it is necessary to form a constriction on the upper portion of the droplet, and at this time, a pushing force acts simultaneously. As a result, it is difficult to reliably remove the droplets even by energization of a plurality of peak current groups. Therefore, in the inventions of Patent Documents 2 to 4, although the formation of droplets is improved, there remains a problem in reliable separation of the droplets.

  Here, considering direct current carbon dioxide arc welding of a steel material, in a current region where the average welding current value is less than about 200 A, the droplets are short-circuited. That is, the arc period and the short-circuit period are periodically repeated, and the droplet formed during the arc period shifts during the short-circuit period. By precisely controlling the welding current during this short-circuit period, the generation of spatter can be reduced. However, pulse arc welding (mag pulse welding or MIG pulse welding) using a shielding gas containing argon gas as a main component can further reduce the generation of spatter. However, in this current region, it can be said that the amount of spatter of carbon dioxide arc welding is at a level that does not cause a problem in practice. When the average welding current value is in a current range of about 200 A or more, when the arc length is long, globule transition occurs, and the droplets migrate by free fall without being short-circuited by gravity. For this reason, the occurrence of spatter is small. In order to perform high-speed welding with a welding speed of 80 cm / min or higher in this current region, it is necessary to perform welding with a short arc length in order to prevent welding defects such as undercut. When the arc length is shortened, the droplets are transferred with a short circuit. In addition, since the timing at which the short circuit occurs is random, the size of the droplets varies in size, and the irregular droplet transfer state occurs, resulting in the occurrence of many large spatters. Therefore, when high-speed welding is performed in a current region of 200 A or more, the occurrence of spatter can be reduced by performing pulse arc welding using a shield gas mainly composed of argon gas.

  From the above, welding is performed using a shielding gas containing carbon dioxide as a main component, and the welding conditions for which the generation of spatter is to be reduced is particularly when high-speed welding is performed in a current range of 200 A or more. . Accordingly, an object of the present invention is to reduce the amount of spatter generated compared with carbon dioxide arc welding by improving the droplet transfer state of carbon dioxide pulse arc welding in high-speed welding in a current region of 200 A or more. .

In order to solve the above-described problems, the invention of claim 1 uses a shield gas mainly composed of carbon dioxide gas, feeds a welding wire, and supplies a peak period and a base current for supplying a peak current. In the carbon dioxide pulse arc welding method in which welding is performed by repeating the base period as one pulse period,
During the peak period, constant current control of the peak current, and by forming the droplet at the tip of the welding wire by vibrating the peak current,
During the base period, this formed droplet is transferred to the molten pool by short circuit transfer,
Arc length control is performed by constant voltage control of the welding voltage during the base period.
This is a carbon dioxide pulse arc welding method.

In the invention of claim 2, the amplitude and vibration period of the oscillating peak current are set to values at which spatter does not scatter from the droplet being formed by suppressing overheating of the droplet.
The carbon dioxide pulsed arc welding method according to claim 1.

In the invention of claim 3, the waveform of the oscillating peak current is a rectangular wave shape.
The carbon dioxide pulse arc welding method according to claim 1 or 2, wherein

In the invention of claim 4, the peak period is a period set according to the feeding speed of the welding wire.
The carbon dioxide pulse arc welding method according to any one of claims 1 to 3, wherein:

In the invention of claim 5, the base period is a period that continues until a short-circuit transition is performed.
It is a carbon dioxide pulse arc welding method of any one of Claims 1-4 characterized by the above-mentioned.

In the invention of claim 6, the base period is formed from a short-circuit standby period until a short-circuit occurs, and a short-circuit period in which a subsequent droplet transitions to a short-circuit,
Applying a first base current determined by an arc load during the short-circuit standby period, and applying a second base current that gradually increases with time from the value of the first base current during the short-circuit period;
It is a carbon dioxide pulse arc welding method of any one of Claims 1-4 characterized by the above-mentioned.

According to a seventh aspect of the present invention, the base period includes a short-circuit standby period until a short-circuit occurs, a short-circuit period during which a droplet moves to a short-circuit, and a short-circuit again after the subsequent arc is re-generated. Formed from a predetermined re-short circuit prevention period to prevent,
A first base current determined by an arc load is applied during the short-circuit standby period, and a second base current that gradually increases with time from the value of the first base current is supplied during the short-circuit period, and the re-short circuit is performed. During the prevention period, a third base current having a value larger than the value of the first base current is applied.
It is a carbon dioxide pulse arc welding method of any one of Claims 1-4 characterized by the above-mentioned.

In the invention of claim 8, the base period is formed of a short-circuit standby period until a short-circuit occurs, a short-circuit period in which a subsequent droplet transitions to a short-circuit, and a predetermined delay period following the short-circuit period.
A first base current determined by an arc load is applied during the short-circuit standby period, a second base current that gradually increases with time from the value of the first base current is supplied during the short-circuit period, and the delay period Medium is energized with a fourth base current having a value smaller than the value of the second base current at the end of the short-circuit period.
It is a carbon dioxide pulse arc welding method of any one of Claims 1-4 characterized by the above-mentioned.

According to a ninth aspect of the present invention, the base period includes a short-circuit standby period until a short-circuit occurs, a short-circuit period during which the droplets are short-circuited, and a short-circuit again after the subsequent arc is re-generated. Formed from a predetermined re-shorting prevention period followed by a predetermined delay period,
A first base current determined by an arc load is applied during the short-circuit standby period, and a second base current that gradually increases with time from the value of the first base current is supplied during the short-circuit period, and the re-short circuit is performed. A third base current having a value larger than the value of the first base current is applied during the prevention period, and a value having a value smaller than the value of the second base current at the end of the short-circuit period is applied during the delay period. Energize 4 base currents,
It is a carbon dioxide pulse arc welding method of any one of Claims 1-4 characterized by the above-mentioned.

  According to the present invention, in the carbon dioxide pulse arc welding method using a shielding gas containing carbon dioxide as a main component, a droplet period is substantially desired by providing a peak period and a base period and vibrating a peak current during the peak period. The formed droplets can be short-circuited during the base period. For this reason, since one droplet period and one droplet transfer state can be realized, high-quality welding with less spattering can be achieved. In particular, during high-speed welding in a current region of 200 A or more, the generation of spatter can be suppressed and the bead appearance can be improved as compared with the DC carbon dioxide arc welding method.

It is a current and voltage waveform diagram showing a carbon dioxide pulse arc welding method according to an embodiment of the present invention. It is a figure which illustrates the appropriate value of peak period Tp with respect to the feeding speed which concerns on embodiment of this invention. It is a block diagram of the welding power source for implementing the carbon dioxide pulse arc welding method concerning an embodiment of the invention. It is a current / voltage waveform diagram of a conventional pulse arc welding method.

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

  FIG. 1 is a current / voltage waveform diagram showing a carbon dioxide pulse arc welding method according to an embodiment of the present invention. FIG. 4A shows the time change of the welding current Iw, and FIG. 4B shows the time change of the welding voltage Vw. The figure shows the case of a carbon dioxide pulse arc welding method using a shielding gas containing carbon dioxide as a main component. Hereinafter, a description will be given with reference to FIG.

  In the carbon dioxide pulse arc welding method according to the embodiment of the present invention, the pulse period Tpb at times t1 to t3 is formed from two periods. The first is the base period Tb from time t1 to t2, and the second is the peak period Tp from time t2 to t3. Therefore, welding is performed repeatedly with the base period Tb and the peak period Tp as one pulse period Tpb. In the base period Tb, the droplet transitions to a short circuit, and the droplet is formed in the peak period Tp. The peak period Tp is set to an appropriate value in advance so as to form a droplet having a substantially constant size. During this peak period Tp, since the output of the welding power source is controlled at a constant current, the value of the peak current Ip can be directly controlled. The base period Tb is a period that continues until the droplet formed during the peak period Tp shifts to a short circuit, and has a different value for each cycle. The output of the welding power source during the base period Tb is controlled at a constant voltage. This is because the arc length is controlled by controlling the output at a constant voltage as in the case of general consumable electrode arc welding. Therefore, the value of the base current Ib cannot be directly controlled and becomes a value determined by the arc load. Hereinafter, each period will be described in detail.

(1) Base period Tb (short-circuit transition period)
A droplet is formed during the peak period Tp of the previous period. Then, as shown in FIG. 5A, the first base current Ib1 determined by the arc load is energized from time t1. Since the welding current average value in the steady state is determined corresponding to the welding wire feeding speed, if the feeding speed is a constant value, the welding current average value can also be regarded as a constant value. Since the peak current Ip is set to a large value, the base current Ib has a relatively small value in order for the welding current average value to be a constant value. Therefore, the value of the first base current Ib1 is also smaller than the average value of the peak current Ip. The welding voltage Vw becomes a base voltage value Vb as shown in FIG. In this state, the welding wire is fed to the molten pool at a predetermined constant speed, and since the first base current Ib1 is a small current value, the feeding speed becomes faster than the melting speed, and the wire tip Will gradually approach the molten pool. At time t11, when the droplet at the tip of the wire comes into contact with the molten pool and is in a short circuit state, the welding voltage Vw rapidly drops to a short circuit voltage value of about several volts, as shown in FIG. When this short-circuit state is determined by the change in the welding voltage Vw, as shown in FIG. 5A, the second base current (short-circuit current) Ib2 that gradually increases with time from the value of the first base current Ib1. To release the short-circuit state. In the short-circuit period from time t11 to t12, the droplet moves to short-circuit, and the arc is regenerated at time t12. When the arc is regenerated, the welding voltage Vw rapidly increases to an arc voltage value of about several tens of volts as shown in FIG. When the reoccurrence of the arc is determined by the change in the welding voltage Vw, as shown in FIG. 4A, during the predetermined re-short-circuit prevention period Th from time t12 to t13, the value of the first base current Ib1 is exceeded. The third base current Ib3 having a large value is energized. By applying the third base current Ib3, a short circuit is prevented from occurring again immediately after the arc is regenerated. That is, when the arc is regenerated, the wire tip and the molten pool are close to each other, so depending on the welding conditions (type of welding wire, feeding speed, groove counting, welding speed, etc.) Due to vibration, re-short circuit is likely to occur. When the re-short circuit occurs, spatter occurs and the welding state becomes unstable. In order to prevent the occurrence of this re-short circuit, a large third base current Ib3 is energized when the arc is regenerated, thereby strengthening the arc force to the molten pool and pushing down the molten pool, and the wire tip and melt Re-shorting is prevented by increasing the distance to the pond. The third base current Ib3 is controlled to be gradually decreased from the current at the time when the arc is regenerated at time t12, so that a large value is maintained. The re-shorting prevention period Th is set to a range of about 0.5 to 3 ms. It is desirable to optimize the re-short circuit prevention period Th according to the welding conditions.

  Then, as shown in FIG. 5A, the transition is made to the peak period Tp at the time t2 when the predetermined delay period Td has elapsed from the time t13 when the re-short circuit prevention period Th ends. During the delay period Td from time t13 to t2, the fourth base current Ib4 having a value smaller than the value of the second base current at the end of the short-circuit period is energized, as shown in FIG. As shown in FIG. 5B, the welding voltage Vw becomes the base voltage Vb. This delay period Td is set in a range of about 0.5 to 3 ms. The reason for providing the delay period Td is to weaken the arc force to the molten pool and to flatten the molten pool surface by supplying the fourth base current Ib4 having a small current value after the arc is regenerated. Thereby, the spatter from a molten pool when the peak current Ip of a large current value starts energization can be reduced.

  The droplet transfer during the base period Tb will be described as follows. During the previous peak period Tp, the droplets are formed in a substantially constant size as will be described later. Since the first base current Ib1 having a small current value is energized during the short-circuit standby period from the time t1 to the time t11, the lifting force does not act so much on the droplet, and gravity and surface tension act to form a spherical shape. To be shaped. In addition, since a short circuit occurs at time 11 in a state where the first base current Ib1 having a small current value is energized, the occurrence of sputtering when the short circuit occurs is reduced. At the same time, since the droplet contacts the molten pool in a shaped state, it smoothly integrates with the molten pool. Therefore, since the droplet is in a short circuit transition state, the value of the second base current Ib2 during the short circuit period does not need to be increased so much, and the transition is smoothly performed and the arc is regenerated. A small amount of spatter is generated at the time of this arc re-occurrence, but since it is a smooth short-circuit transition, the amount is not so large that it is not a practically problematic level.

Since the short-circuit standby period is a period until the droplet is short-circuited to the molten pool, it is not a constant value but a value that changes every moment depending on the welding state. Similarly, since the short-circuit period is a period from when the droplet is short-circuited to the molten pool until the transition is completed and the arc is regenerated, it is not a constant value but a value that varies depending on the droplet transition state. However, when the welding state is stable, the variation in the short-circuit period is small. The re-short circuit prevention period Th and the delay period Td are predetermined constant values. Therefore, the base period Tb, which is the sum of these periods, is not a constant value but a value that varies depending on the welding state. However, in a stable welding state, the base period Tb can be regarded as a substantially constant value. The base current Ib during the base period Tb is formed from the first base current Ib1 to the fourth base current Ib4. Whether the re-short-circuit prevention period Th and the delay period Td are provided according to the welding conditions can be set. This is because, depending on the welding conditions, providing each period may have an effect of reducing spatter. On the contrary, there are welding conditions in which even if these periods are provided, there is no effect such as reduction of spatter. Therefore, the base period Tb may be formed by selecting one pattern from the following four patterns according to the welding conditions.
(A) Short-circuit standby period + short-circuit period (b) Short-circuit standby period + short-circuit period + re-short-circuit prevention period Th
(C) Short-circuit standby period + short-circuit period + delay period Td
(D) Short-circuit standby period + short-circuit period + re-short-circuit prevention period Th + delay period Td

(2) Peak period Tp (droplet formation period) at times t2 to t3
During the peak period Tp from time t2 to t3, as shown in FIG. 6A, the oscillating peak current Ip is applied, and as shown in FIG. 5B, the welding voltage Vw is the corresponding oscillating peak. The voltage Vp. The oscillation waveform of the peak current Ip is a high peak current HIp during the high peak period HTp shown at time t2 to t21, and is a low peak during the subsequent low peak period LTp from time t21 to t22, as shown in FIG. The current LIp is obtained. The total period of the high peak period HTp and the low peak period LTp is the oscillation period Ts. Further, the difference (HIp−LIp) between the high peak current HIp and the low peak current LIp is the amplitude Ws. Further, the duty Ds = HTp / Ts. Therefore, the peak current Ip vibrates with the amplitude Ws and the vibration period Ts. The example of the range of each value when a welding wire is a mild steel wire with a diameter of 1.2 mm is as follows. High peak current HIp: 350 to 500 A, amplitude Ws: 200 to 400 A, vibration period Ts: 1.5 to 3.0 ms, duty Ds: 0.5 to 0.75. In the figure, the peak current Ip is illustrated as oscillating in a rectangular wave shape, but may be oscillated in a trapezoidal wave shape, a triangular wave shape, a sine wave shape, a sawtooth wave shape, or the like. The reason for oscillating the peak current Ip is as follows. That is, when the peak current Ip is continuously energized without oscillating, the temperature of the droplet is superheated with the formation of the droplet, and the phenomenon that the gas contained in the droplet expands and the droplet bursts occurs. It comes to occur. When this rupture phenomenon occurs, spatter is scattered from the droplet and formation of the droplet is also inhibited. When the peak current Ip is vibrated with an appropriate amplitude Ws and vibration period Ts, overheating of the droplet can be suppressed and a droplet having a desired size can be formed. The droplet having a desired size is about 1.5 to 2.5 times the diameter of the welding wire. Therefore, the amplitude Ws and the vibration period Ts are set to values at which the spatter does not scatter from the droplet without overheating the droplet. Both values are set to appropriate values according to the material of the welding wire, the diameter, the type of shield gas, the feeding speed, and the like. By this peak period Tp, a droplet having a substantially desired size is formed.

  As described above, the length of the peak period Tp is set to an appropriate value according to the welding conditions (material, diameter, and feeding speed of the welding wire). This appropriate value is selected so that the droplets formed during the peak period Tp are stably the same size by performing a welding experiment under each welding condition. FIG. 2 is a diagram illustrating an appropriate value of the peak period Tp with respect to the feeding speed. In the figure, the horizontal axis indicates the feeding speed (m / min), and the vertical axis indicates the peak period Tp (ms). The figure shows the case where a mild steel wire having a diameter of 1.2 mm is used as the welding wire. As shown in the figure, the peak period Tp becomes longer as the feeding speed becomes faster. This is because when the feed rate is increased, the peak period Tp is lengthened so that the droplet size formed during the peak period Tp is increased to balance the feed rate and the melting rate.

The droplet transfer of the carbon dioxide pulse arc welding method according to the embodiment of the present invention described above is summarized as follows.
(1) During the peak period Tp, the peak current Ip is oscillated to suppress overheating of the droplet and to prevent spatter from the droplet. The length of the peak period Tp is set to an appropriate value according to the welding conditions. For this reason, the droplet of a desired size can be formed stably.
(2) During the base period Tb, the first base current Ib1 having a small current value is energized to guide the droplet at the tip of the welding wire to a short circuit with the molten pool. And a droplet will transfer to a short circuit. Since a short circuit occurs with the first base current Ib1 having a small current value, the occurrence of spatter is small when a short circuit occurs. In addition, since a droplet having a substantially constant size is transferred to a short circuit, the transfer is performed smoothly, and the amount of spatter at the time of arc re-occurrence is not so large as to be a practical problem.
(3) By the operations (1) and (2), one droplet moves in synchronization with each pulse period Tpb. That is, one droplet period and one droplet transfer state are realized, and a stable welding state is obtained. For this reason, even during high-speed welding in a current range of 200 A or more where the welding state tends to be unstable, high-quality welding with less spatter can be performed.

  Numerical examples of each parameter in the waveform of FIG. 1 are shown below. Welding wire: Mild steel wire with a diameter of 1.2 mm, average welding current value: 220 A, feed speed (set value): 7 m / min, first base current Ib1: 100 A during the short-circuit standby period, re-short-circuit prevention period Th (set value) ): 1 ms, delay period Td (set value): 1 ms, fourth base current Ib4: 100 A, high peak current value HIp (set value): 450 A, amplitude Ws (set value): 350 A, vibration period Ts (set value) : 2.0 ms, duty Ds (set value): 1.5 / 2.0 = 0.75, peak period Tp (set value): 9.5 ms. The description of (set value) indicates that the value is set to an appropriate value in advance. On the contrary, a value not described as (set value) is a measured value and indicates a changing value.

  FIG. 3 is a block diagram of a welding power source for carrying out the carbon dioxide pulse arc welding method according to the embodiment of the present invention described above with reference to FIG. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as a three-phase 200V, performs output control by inverter control according to an error amplification signal Ea described later, and generates a welding current Iw and an output voltage E suitable for arc welding. Output. The power supply main circuit PM is not shown in the figure, but includes, for example, a primary rectifier that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current to high frequency alternating current, and arcs the high frequency alternating current A high-frequency transformer that steps down to a voltage value suitable for welding, a secondary rectifier that rectifies the stepped-down high-frequency alternating current, and performs pulse width modulation control using the error amplification signal Ea as an input. It consists of a drive circuit that drives. Reactor WL is formed by winding a cable around an iron core, has an inductance value of Lw (μH), and smoothes the output of power supply main circuit PM. The voltage output from the power supply main circuit PM becomes the output voltage E, and the voltage after passing through the reactor WL becomes the welding voltage Vw. Therefore, the welding voltage Vw is a voltage between the welding wire 1 and the base material 2. The welding wire 1 is fed through the welding torch 4 by the rotation of a feeding roll 5 of a wire feeding device (not shown), and an arc 3 is generated between the base metal 2 and the welding wire 1.

  The current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id. The voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The short-circuit determination circuit SD receives the welding voltage detection signal Vd as an input, determines a short-circuit state based on the value, and outputs a short-circuit determination signal Sd that becomes a high level. The peak period setting circuit TPR outputs a predetermined peak period setting signal Tpr. As described above, the peak period setting signal Tpr is set to an appropriate value according to the welding conditions. The re-short circuit prevention period setting circuit THR outputs a predetermined re-short circuit prevention period setting signal Thr. The delay period setting circuit TDR outputs a predetermined delay period setting signal Tdr. The period switching control circuit ST receives the peak period setting signal Tpr, the re-short circuit prevention period setting signal Thr, the delay period setting signal Tdr, and the short circuit determination signal Sd, and is determined by the peak period setting signal Tpr. When the period ends, the value changes to 1 (short-circuit standby period), and when the short-circuit determination signal Sd becomes High level (short-circuit state) during this period, the value becomes 2 (short-circuit period), and then the short-circuit determination signal When Sd becomes Low level (arc generation state), the value becomes 3 (re-short-circuit prevention period Th) during the period determined by the re-short-circuit prevention period setting signal Thr from that point, and then during the period determined by the delay-period setting signal Tdr. The value becomes 4 (delay period Td), and subsequently becomes 5 (peak period Tp) during the period determined by the peak period setting signal Tpr. And outputs a switching control signal St. In FIG. 1, the period switching control signal St is 1 during the short-circuit standby period from time t1 to t2, 2 during the short-circuit period from time t11 to t12, and 3 during the re-short-circuit prevention period Th from time t12 to t13. And becomes 4 during the delay period Td from time t13 to t2, and becomes 5 during the peak period Tp from time t2 to t3.

  The electronic reactor control circuit ERC receives the period switching control signal St and the welding current detection signal Id as input, and when the period switching control signal St is 2 (short circuit period) or 3 (re-short circuit prevention period), the welding current The detection signal Id is differentiated and multiplied by a predetermined amplification factor Lr to output a current differential signal Bi = Lr · dId / dt. When the period switching control signal St is any other value, the current differential signal Bi = 0 is set. Output. The amplification factor Lr is a positive value and is a constant that determines the inductance value of the reactor formed by electronic control. Therefore, the amplification factor Lr determines the increase rate of the welding current during the short circuit period and the decrease rate of the welding current during the re-short circuit prevention period Th, as will be described later. The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The subtraction circuit SUB subtracts the current differential signal Bi from the output voltage setting signal Er and outputs a voltage control setting signal Ecr = Er-Bi. The output voltage detection circuit ED detects the output voltage E and outputs an output voltage detection signal Ed. The voltage error amplification circuit EV amplifies an error between the voltage control setting signal Ecr and the output voltage detection signal Ed, and outputs a voltage error amplification signal Ev. As shown in Patent Document 5, this electronic reactor control is a technique that has been widely used. The outline is as follows. In the short-circuit period from time t11 to t12 shown in FIG. 1, the load state becomes a short-circuit load and constant voltage control is performed, so that the welding current Iw increases rapidly. At this time, since the amplification factor Lr> 0 and dId / dt> 0, the current differential signal Bi> 0. As a result, the voltage control setting signal Ecr = Er−Bi becomes a value smaller than the output voltage setting signal Er by the value of the current differential signal Bi, and the increasing speed of the welding current Iw is moderated. When the re-short-circuit prevention period Th from time t12 to time t13 is reached, the load state becomes an arc load, so the welding current Iw decreases. Also at this time, the welding current Iw is gradually reduced by the electronic reactor control. As a result, the third base current Ib3 during the re-short-circuit prevention period Th substantially maintains a large current when the arc is regenerated. When the delay period Td at time t13 is reached, the operation of the electronic reactor control is prohibited, so that the welding current Iw rapidly decreases to a small fourth base current Ib4. In this electronic reactor control, a reactor having an inductance value of Lr (μH) is electronically formed. Therefore, when combined with the inductance value Lw of the reactor WL described above, the welding power source incorporates an equivalent reactor having an inductance value of Lw + Lr. For example, Lw = 30 μH and Lr = 200 μH are set. The reason why Lw is a small value is that the welding state can be stabilized by increasing the change in the peak current Ip. On the other hand, during the short-circuit period and the re-short-circuit prevention period Th, it is possible to stabilize the welding state if the change in the welding current Iw is moderated. Therefore, the electronic reactor control for forming a large value Lr is operated. ing.

  The high peak current setting circuit HIPR outputs a predetermined high peak current setting signal HIpr. The amplitude setting circuit WSR outputs a predetermined amplitude setting signal Wsr. The vibration cycle setting circuit TSR outputs a predetermined vibration cycle setting signal Tsr. The duty setting circuit DSR outputs a predetermined duty setting signal Dsr. The peak current setting circuit IPR receives the high peak current setting signal HIpr, the amplitude setting signal Wsr, the vibration period setting signal Tsr, the duty setting signal Dsr, and the period switching control signal St as inputs. A rectangular wave-shaped peak current setting signal Ipr as shown in FIG. 1 which starts vibration in synchronization with the switching control signal St = 5 (peak period Tp) is output. The current error amplification circuit EI amplifies an error between the peak current setting signal Ipr and the welding current detection signal Id and outputs a current error amplification signal Ei. The switching circuit SW receives the period switching control signal St, the current error amplification signal Ei, and the voltage error amplification signal Ev. When the period switching control signal St = 1 to 4 (base period Tb), the switching circuit SW The voltage error amplification signal Ev is output as the error amplification signal Ea, and when St = 5 (peak period Tp), the current error amplification signal Ei is output as the error amplification signal Ea. Thus, constant current control is performed during the peak period Tp, and constant voltage control is performed during the base period Tb. With the circuit configuration described above, the welding current Iw in FIG. 1 is energized and the welding voltage Vw is output.

  According to the above-described embodiment, in the carbon dioxide pulse arc welding method using the shielding gas containing carbon dioxide as a main component, the droplet period is provided by providing the peak period and the base period and vibrating the peak current during the peak period. Can be formed in a substantially desired size, and the formed droplet can be short-circuited in the base period. For this reason, since one droplet period and one droplet transfer state can be realized, high-quality welding with less spattering can be achieved. In particular, during high-speed welding in a current region of 200 A or more, the generation of spatter can be suppressed and the bead appearance can be improved as compared with the DC carbon dioxide arc welding method.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll Bi Current differential signal E Output voltage Ecr Voltage control setting signal ED Output voltage detection circuit Ed Output voltage detection signal EI Current error amplification circuit Ei Current error amplification signal ERC Electronic reactor Control circuit ER Output voltage setting circuit Er Output voltage setting signal EV Voltage error amplification circuit Ev Voltage error amplification signal HIp High peak current HIPR High peak current setting circuit HIpr High peak current setting signal HTp High peak period Iav Welding current average value Ib Base current Ib1 first base current Ib2 second base current Ib3 third base current Ib4 fourth base current ID current detection circuit Id welding current detection signal Ip peak current IPR peak current setting circuit Ipr peak current setting signal Iw welding current LIp low peak current LTp Low peak period PM Power supply main circuit Sd Short circuit Circuit Sd Short circuit determination signal Spb Pulse cycle signal ST Period switching control circuit St Period switching control signal SUB Subtraction circuit SW Switching circuit Tb Base period Td Delay period TDR Delay period setting circuit Tdr Delay period setting signal Th Re-short circuit prevention period THR Re-short circuit prevention Period setting circuit Thr Re-shorting prevention period setting signal Tp Peak period Tpb Pulse period Ts Vibration period TSR Vibration period setting circuit Tsr Vibration period setting signal Vb Base voltage VD Voltage detection circuit vd Welding voltage detection signal Vp Peak voltage Vw Welding voltage Ws Amplitude WSR Amplitude setting circuit Wsr Amplitude setting signal

Claims (9)

A carbon dioxide gas pulse that uses a shielding gas containing carbon dioxide as its main component, feeds the welding wire, and repeats the peak period in which the peak current is applied and the base period in which the base current is supplied as one pulse period. In the arc welding method,
During the peak period, constant current control of the peak current, and by forming the droplet at the tip of the welding wire by vibrating the peak current,
During the base period, this formed droplet is transferred to the molten pool by short circuit transfer,
Arc length control is performed by constant voltage control of the welding voltage during the base period.
A carbon dioxide pulse arc welding method characterized by the above. The amplitude and vibration period of the oscillating peak current are set to a value at which spatter does not scatter from the droplet being formed by suppressing overheating of the droplet.
The carbon dioxide pulse arc welding method according to claim 1. The waveform of the oscillating peak current is rectangular.
The carbon dioxide pulse arc welding method according to claim 1 or 2, wherein The peak period is a period set according to the feeding speed of the welding wire,
The carbon dioxide pulse arc welding method according to any one of claims 1 to 3. The base period is a period that continues until a short-circuit transition is performed,
The carbon dioxide pulse arc welding method according to any one of claims 1 to 4, wherein: The base period is formed from a short-circuit standby period until a short-circuit occurs, and a short-circuit period in which a subsequent droplet transitions to a short-circuit,
Applying a first base current determined by an arc load during the short-circuit standby period, and applying a second base current that gradually increases with time from the value of the first base current during the short-circuit period;
The carbon dioxide pulse arc welding method according to any one of claims 1 to 4, wherein: The base period includes a short-circuit standby period until a short-circuit occurs, a short-circuit period in which a droplet subsequently moves to a short-circuit, and a predetermined re-short circuit that prevents a short-circuit from occurring again after a subsequent arc is re-generated. Prevention period, and formed from
A first base current determined by an arc load is applied during the short-circuit standby period, and a second base current that gradually increases with time from the value of the first base current is supplied during the short-circuit period, and the re-short circuit is performed. During the prevention period, a third base current having a value larger than the value of the first base current is applied.
The carbon dioxide pulse arc welding method according to any one of claims 1 to 4, wherein: The base period is formed from a short-circuit standby period until a short-circuit occurs, a short-circuit period in which the subsequent droplet moves to a short-circuit, and a predetermined delay period following the short-circuit period.
A first base current determined by an arc load is applied during the short-circuit standby period, a second base current that gradually increases with time from the value of the first base current is supplied during the short-circuit period, and the delay period Medium is energized with a fourth base current having a value smaller than the value of the second base current at the end of the short-circuit period.
The carbon dioxide pulse arc welding method according to any one of claims 1 to 4, wherein: The base period includes a short-circuit standby period until a short-circuit occurs, a short-circuit period in which a droplet subsequently moves to a short-circuit, and a predetermined re-short circuit that prevents a short-circuit from occurring again after a subsequent arc is re-generated. Formed from a prevention period followed by a predetermined delay period,
A first base current determined by an arc load is applied during the short-circuit standby period, and a second base current that gradually increases with time from the value of the first base current is supplied during the short-circuit period, and the re-short circuit is performed. A third base current having a value larger than the value of the first base current is applied during the prevention period, and a value having a value smaller than the value of the second base current at the end of the short-circuit period is applied during the delay period. Energize 4 base currents,
The carbon dioxide pulse arc welding method according to any one of claims 1 to 4, wherein:

Images