JP2010075983A - Control method of ac pulse arc welding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain stable welding condition even when a current ratio at an electrode negative polarity is set to a large value, in an AC pulse arc welding using a consumable electrode. <P>SOLUTION: The welding is performed by repeating a cycle of energizing pattern which comprises the steps of: conducting a peak current Ip of a critical value or more at the electrode positive polarity during a peak period Tp at the electrode positive polarity; conducting a peak current Ipn of the critical value or more at the electrode negative polarity during a peak period Tpn at the electrode negative polarity; conducting a base current Ibn of less than a critical value at the electrode negative polarity during a base period Tbn at the electrode negative polarity; and successively conducting a base current Ib of less than a critical value at the electrode positive polarity during a base period Tb at the electrode positive polarity. By preparing the peak period Tp at the electrode positive polarity and the peak period Tpn at the electrode negative polarity, even when a current ratio at the electrode negative polarity is set to a large value, the condition of causing one droplet transfer per one pulse can be maintained, which provides the stable welding condition. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an AC pulse arc welding control method capable of obtaining a stable welding state when an electrode negative polarity current ratio is set to a large value.

  In AC pulse arc welding, welding is performed by repeating the energization of the peak current and base current during the electrode positive polarity period and the energization of the base current during the electrode negative polarity period as one cycle. In this AC pulse arc welding, the heat input to the base material can be adjusted by adjusting the electrode negative polarity period to change the electrode negative polarity current ratio. For this reason, low heat input welding is possible, and high-quality thin plate welding can be performed. Further, by changing the electrode negative polarity current ratio, the bead shape such as the penetration depth and the surplus height can be optimized according to the workpiece. Hereinafter, conventional AC pulse arc welding will be described (for example, see Patent Documents 1 and 2).

  FIG. 7 is a general current / voltage waveform diagram in AC pulse arc welding. FIG. 4A shows the welding current Iw, and FIG. 4B shows the welding voltage Vw. In the figure, the upper side from 0A and 0V is when the electrode has a positive polarity EP, and the lower side is when the electrode has a negative polarity EN. The welding wire is fed at a predetermined feeding speed. At the time of polarity switching, a high voltage of several hundred volts is applied between the welding wire and the base material for a short time in order to prevent arc interruption. Hereinafter, a description will be given with reference to FIG.

  During the electrode negative polarity period Ten, as shown in FIG. 6A, a predetermined electrode negative polarity base current Ibn is energized, and as shown in FIG. 5B, the electrode negative polarity base voltage Vbn is applied. . The electrode negative polarity base current Ibn is set to a value less than the critical value so as not to form droplets at the tip of the welding wire. For example, Ibn is about 20 to 100A. The critical value is a welding current value at which the droplet transfer state of the welding wire becomes the spray transfer state, and the value varies depending on the material of the welding wire, the type of shield gas, and the like. In the case of an aluminum wire often used for AC pulsed arc welding (shielding gas is argon gas), the critical value is about ** 350A.

  The electrode positive polarity period Tep is divided into a peak period Tp and a base period Tb. During this peak period Tp, as shown in FIG. 6A, a predetermined peak current Ip is applied to a large current value equal to or higher than the critical value in order to cause droplet transfer, as shown in FIG. In addition, a peak voltage Vp is applied. Here, the peak period Tp and the peak current Ip are set so as to be in a so-called 1-pulse 1 droplet transfer state. The one-pulse / one-droplet transfer state is a state in which one droplet moves to the molten pool in one cycle by one energization of the peak current Ip, and a stable welding state is obtained. During the base period Tb, as shown in FIG. 5A, a predetermined base current Ib is applied to a small current value less than the critical value so as not to form droplets, and as shown in FIG. The base voltage Vb is applied. For example, it is about Ib = 20-80A.

  The welding is performed by repeating the electrode negative polarity period Ten, the peak period Tp, and the base period Tb as one pulse period Tf. The electrode negative polarity period Ten and the peak period Tp are predetermined periods, and the base period Tb is a period determined by feedback control so that the arc length is appropriate. In this arc length control, the length of the base period Tb is controlled such that the average value Vav of the absolute values of the welding voltage Vw shown in FIG. 5B is equal to a predetermined voltage setting value Vr (not shown). Is done by doing.

  The formation and transfer of droplets in AC pulse arc welding are summarized as follows. The droplet moves near the end of the peak period Tp. During the subsequent base period Tb, since the base current Ib having a small current value less than the critical value is energized, the tip of the welding wire does not melt so much and no droplets are formed. During the subsequent electrode minus polarity period Ten, the electrode minus polarity base current Ibn having a small current value less than the critical value is energized. Even with a small current of the same value, the effect of melting the tip of the welding wire is greater when the electrode has a negative polarity EN than when the electrode has a positive polarity EP. However, in AC pulse arc welding, the electrode negative polarity current ratio is generally used in a range of about 0 to 30%, so the above electrode negative polarity period Ten is a short period. For this reason, the welding wire tip is slightly melted, and a small droplet is formed. During the subsequent peak period Tp, a peak current Ip having a large current value equal to or higher than the critical value is energized. As the peak current Ip is applied, the tip of the welding wire is rapidly melted to form droplets. Furthermore, an electromagnetic pinch force acts on the top of the droplet formed by energization of the peak current Ip to form a constriction. Then, near the end of the peak period Tp (immediately before the end, at the end time or immediately after the end), the constriction rapidly advances and the droplets move to the molten pool. In direct current pulse arc welding, formation and transfer of droplets are performed during the peak period Tp. In AC pulse arc welding, small droplets may be formed during the electrode negative polarity period Ten, but basically, as in the case of DC pulse arc welding, droplet formation and transition during the peak period Tp. You can think that is done. As described above, a 1-pulse 1-droplet transfer state in which one droplet transfer is performed in one cycle results in a stable welding state, and good welding quality is obtained.

The electrode negative polarity current ratio Ren (%) is defined as follows.
Ren = ((Ten · | Ibn |) / (Ten · | Ibn | + Tp · Ip + Tb · Ib)) × 100
That is, the electrode negative polarity current ratio Ren represents the ratio of the welding current during the electrode negative polarity period, which is the average value of the absolute values of the welding current.

  In the above equation, the peak current Ip and the base current Ib are predetermined values, and the peak period Tp is also a predetermined value. The base period Tb can also be regarded as a substantially predetermined value in a steady state where the arc length is an appropriate value. Therefore, the electrode negative polarity current ratio Ren can be adjusted by adjusting the electrode negative polarity period Ten and / or the electrode negative polarity base current Ibn. When the electrode negative polarity current ratio Ren is changed, the melted portion and the surplus portion change and the bead shape changes.

JP 2002-86271 A JP 2007-283393 A

  As described above, in AC pulse arc welding, welding is generally performed by setting the electrode negative polarity current ratio to an appropriate value in accordance with the work within a range of about 0 to 30%. An electrode negative polarity current ratio of 0% means direct current pulse arc welding. When the electrode negative polarity current ratio is in the above normal range, droplets are not formed largely during the electrode negative polarity period Ten, so that the droplets can be formed and transferred during the peak period Tp.

  However, depending on the workpiece, it may be necessary to form a bead shape having a small dilution rate with a small melted portion and a large surplus portion. In order to form such a bead shape, it is necessary to set the electrode minus polarity current ratio to 30% or more, which is a value larger than the normal range. Sometimes it may be necessary to set a value exceeding 50%. In the prior art, in order to set the electrode minus polarity current ratio to a large value, the electrode minus polarity period Ten and / or the electrode minus polarity base current Ibn is set to a large value. In this case, the tip of the welding wire is melted during the electrode negative polarity period Ten, and a large droplet is formed. Since the peak period Tp is entered in this state, the droplets become even larger during the peak period Tp, and even after the peak period Tp ends, the droplets cannot be completely transferred, and the droplets are not transferred to the tip of the welding wire. Will remain. This residual droplet will affect the droplet transfer of the next cycle, and as a result, the one-pulse / one-droplet transfer state cannot be maintained, resulting in an unstable welding state in which the droplet transfer occurs randomly. Become.

  Therefore, an object of the present invention is to provide an AC pulse arc welding control method capable of obtaining a stable welding state even when the electrode negative polarity current ratio is set to a value larger than the normal range.

In order to solve the above-described problem, the first invention
In the AC pulsed arc welding control method for welding by feeding a welding wire and energizing an AC welding current,
During the electrode positive polarity peak period, apply an electrode positive polarity peak current above the critical value,
Next, during the electrode negative polarity peak period, apply an electrode negative polarity peak current above the critical value,
Subsequently, during the electrode negative polarity base period, an electrode negative polarity base current less than the critical value is applied,
Next, during the electrode positive polarity base period, an electrode positive polarity base current less than the critical value is applied,
Welding by repeating these energizations as one cycle,
An AC pulse arc welding control method characterized by the above.

The second invention changes the electrode negative polarity current ratio by adjusting at least one of the electrode negative polarity peak period, the electrode negative polarity base period, or the electrode negative polarity base current.
An AC pulse arc welding control method according to the first aspect of the invention.

A third aspect of the invention relates to an AC pulse arc welding control method in which a welding wire is fed and an AC welding current is supplied for welding.
During the electrode positive polarity peak period, apply an electrode positive polarity peak current above the critical value,
Next, during the electrode negative polarity peak period, apply an electrode negative polarity peak current above the critical value,
Subsequently, during the electrode negative polarity base period, an electrode negative polarity base current less than the critical value is applied,
Welding by repeating these energizations as one cycle,
An AC pulse arc welding control method characterized by the above.

The fourth invention changes the electrode minus polarity current ratio by adjusting the electrode minus polarity peak period and / or the electrode minus polarity base current,
The AC pulse arc welding control method according to the third aspect of the invention.

  According to the present invention, by forming the peak period from the electrode positive polarity peak period and the electrode negative polarity peak period, the electrode negative polarity current ratio can be set to a large value, and the electrode negative polarity current ratio is Even when it is a large value, it is possible to make a transition to one pulse per droplet. Therefore, a bead shape with a small dilution rate can be formed with high quality.

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

[Embodiment 1]
FIG. 1 is a waveform diagram of a welding current Iw showing an AC pulse arc welding control method according to Embodiment 1 of the present invention. In the figure, the upper side from 0A shows the electrode positive polarity EP, and the lower side shows the electrode negative polarity EN. This figure shows a case where the electrode negative polarity current ratio is set larger than the normal range (about 0 to 30%). Also in the figure, a high voltage is applied between the welding wire and the base material in order to prevent arc break at the time of polarity switching. Hereinafter, a description will be given with reference to FIG.

  During the electrode positive polarity peak period Tp from time t1 to t2, an electrode positive polarity peak current Ip greater than the critical value is applied. The polarity is inverted at time t2. During the electrode negative polarity peak period Tpn from time t2 to t3, the electrode negative polarity peak current Ipn greater than the critical value is applied. During the electrode negative polarity base period Tbn from time t3 to t4, the electrode negative polarity base current Ibn less than the critical value is applied. The polarity is inverted at time t4. During the electrode positive polarity base period Tb from time t4 to t5, the electrode positive polarity base current Ib less than the critical value is applied. From time t5 to t6, the above-mentioned electrode positive polarity peak period Tp is reached again, and from time t6 to t7, the above-mentioned electrode minus polarity peak period Tpn is reached again. The period from time t1 to t5 is one pulse period Tf. Further, the period from time t2 to t4 is the electrode minus polarity period Ten.

The electrode positive polarity peak period Tp, the electrode positive polarity peak current Ip, the electrode negative polarity peak period Tpn, the electrode negative polarity peak current Ipn, the electrode negative polarity base period Tbn, and the electrode negative polarity. The base current Ibn and the electrode positive polarity base current Ib are set to appropriate values in advance. Further, the length of the pulse period Tf is feedback-controlled (arc length control) so that the average value of the absolute values of the welding voltage becomes equal to a predetermined voltage setting value. When the pulse period Tf changes, the electrode positive polarity base period Tb changes. In the figure, the electrode negative polarity current ratio Ren is as follows.
Ren = ((Tpn · | Ipn | + Tbn · | Ibn |) / (Tp · Ip + Tpn · | Ipn | + Tbn · | Ibn | + Tb · Ib)) × 100

  This figure shows a case where the rising and falling edges of the electrode positive polarity peak current Ip and the electrode negative polarity peak current Ipn are steep and become a rectangular wave. However, a trapezoidal wave may be formed by giving a predetermined slope to the rise and fall of these peak currents. In AC pulsed arc welding for aluminum materials, by making these peak currents a trapezoidal wave, the arc force can be weakened and the occurrence of spatter can be reduced.

  Next, formation and transfer of droplets will be described with reference to FIG. In the vicinity of the end of the electrode negative polarity peak period Tpn at the time t3, the droplets go. During the electrode negative polarity base period Tbn at times t3 to t4, droplets are formed. This is set so that the electrode negative polarity base period Tbn becomes long because the electrode negative polarity current ratio is set to be large. For this reason, even if the electrode negative polarity base current Ibn is a small current value, the electrode negative polarity EN promotes melting of the welding wire tip, so that droplets are formed. During the electrode positive polarity base period Tb from time t4 to t5, since a small current was applied and the electrode was positive polarity EP, the welding wire tip melted little and droplets were formed in the previous period. Almost no change from size. During the electrode positive polarity peak period Tp from time t5 to time t6, a large current is applied, so that the droplet becomes larger. In the vicinity of the end of this period, constriction occurs in the droplet, but the droplet size is too large to go. During the electrode negative polarity peak period Tpn from the time t6 to the time t7, since the first current is energized, a strong electromagnetic pinch force acts on the constricted portion of the droplet, and the constriction rapidly proceeds and the droplet moves. That is, when the electrode negative polarity current ratio is set to a large value, droplets are also formed during the electrode negative polarity base period Tbn. For this reason, the size of the droplets to be transferred during the peak period. Becomes larger. For this purpose, two peak periods are provided, and one is set as an electrode plus polarity peak period Tp and the other is set as an electrode minus polarity peak period Tpn so that a large-sized droplet can be surely carried out. Yes. Furthermore, by changing the polarities of these two peak periods, the electrode negative polarity current ratio can be easily set to a large value. In the figure, the electrode negative polarity current ratio is changed by changing at least one of the electrode negative polarity peak period Tpn, the electrode negative polarity base period Tbn, or the electrode negative polarity base current Ibn.

  FIG. 2 is a block diagram of a welding power source for carrying out the AC pulse arc welding control method according to Embodiment 1 of the present invention described above. In the figure, the above-described high voltage application circuit at the time of polarity switching is omitted. Hereinafter, each block will be described with reference to FIG.

  The inverter circuit INV receives an AC commercial power source (not shown) such as a three-phase 200V as an input, performs inverter control by pulse width modulation control using a current error amplification signal Ei, which will be described later, and rectifies and smoothes a DC voltage. Is output. The inverter transformer INT steps down the high-frequency AC voltage to a voltage value suitable for arc welding. The secondary rectifiers D2a to D2d rectify the stepped-down high-frequency alternating current into direct current. The electrode plus polarity transistor PTR is turned on by an electrode plus polarity drive signal Pd described later, and the output of the welding power source becomes the electrode plus polarity EP. The electrode negative polarity transistor NTR is turned on by an electrode negative polarity drive signal Nd described later, and the output of the welding power source becomes the electrode negative polarity EN. The reactor WL smooths the rippled output. The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 coupled to the wire feed motor WM, and an arc 3 is generated between the base metal 2 and the welding wire 1.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The voltage averaging circuit VAV averages the absolute value of the voltage detection signal Vd and outputs a voltage average value signal Vav. The voltage setting circuit VR outputs a predetermined voltage setting signal Vr. The voltage error amplification circuit EV amplifies the error between the voltage setting signal Vr and the voltage average value signal Vav and outputs a voltage error amplification signal Ev. The voltage / frequency conversion circuit VF converts the signal into a signal having a frequency proportional to the voltage error amplification signal Ev, and outputs a pulse period signal Tf that becomes High level for a short time for each frequency.

  The electrode positive polarity peak period setting circuit TPR outputs an electrode positive polarity peak period setting signal Tpr. The electrode negative polarity peak period setting circuit TPNR outputs a predetermined electrode negative peak period setting signal Tpnr. The electrode negative polarity base period setting circuit TBNR outputs a predetermined electrode negative polarity base period setting signal Tbnr. The timer circuit TM receives the pulse period signal Tf, the electrode positive polarity peak period setting signal Tpr, the electrode negative polarity peak period setting signal Tpnr, and the electrode negative polarity base period setting signal Tbnr as inputs. Each time the pulse period signal Tf changes to the high level for a short time, the value becomes 1 during the period determined by the electrode positive polarity peak period setting signal Tpr, and then the period determined by the electrode minus peak period setting signal Tpnr. A timer signal whose value becomes 2 during the period determined by the electrode negative polarity base period setting signal Tbnr, and which becomes 4 during the subsequent electrode positive polarity base period. Output Tm.

  The electrode positive polarity peak current setting circuit IPR outputs a predetermined electrode positive polarity peak current setting signal Ipr. The electrode negative polarity peak current setting circuit IPNR outputs a predetermined electrode negative polarity peak current setting signal Ipnr. The electrode negative polarity base current setting circuit IBNR outputs a predetermined electrode negative polarity base current setting signal Ibnr. The electrode positive polarity base current setting circuit IBR outputs a predetermined electrode positive polarity base current setting signal Ibr. The switching circuit SW includes the timer signal Tm, the electrode positive polarity peak current setting signal Ipr, the electrode negative polarity peak current setting signal Ipnr, the electrode negative polarity base current setting signal Ibnr, and the electrode positive polarity base. When the timer signal Tm = 1, the electrode positive polarity peak current setting signal Ipr is output as the current setting signal Ir when the timer signal Tm = 1, and when the timer signal Tm = 2, the electrode negative polarity peak current is input. The setting signal Ipnr is output as the current setting signal Ir. When the timer signal Tm = 3, the electrode negative polarity base current setting signal Ibnr is output as the current setting signal Ir. When the timer signal Tm = 4, the electrode positive polarity is output. The base current setting signal Ibr is output as the current setting signal Ir. The current detection circuit ID detects the absolute value of the welding current Iw and outputs a current detection signal Id. 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 drive circuit DV receives the timer signal Tm as an input, and outputs the electrode positive polarity drive signal Pd when the timer signal Tm = 1 or 4, and the electrode minus when the timer signal Tm = 2 or 3. The polarity drive signal Nd is output. Accordingly, the electrode positive polarity peak period and the electrode positive polarity base period become the electrode positive polarity, and the electrode negative polarity peak period and the electrode negative polarity base period become the electrode negative polarity. The feeding speed setting circuit FR outputs a predetermined feeding speed setting signal Fr. The feed control circuit FC receives this feed speed setting signal Fr, and feeds a feed control signal Fc for feeding the welding wire 1 at a feed speed corresponding to the value to the wire feed motor WM. Output.

  FIG. 3 is a timing chart of each signal of the welding power source described above with reference to FIG. (A) shows the welding current Iw, (B) shows the pulse period signal Tf, (C) shows the timer signal Tm, (D) shows the current setting signal Ir, FIG. 4E shows the electrode positive polarity drive signal Pd, and FIG. 4F shows the electrode negative polarity drive signal Nd. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 6A, before the time t1, the electrode positive polarity base period Tb is reached, the time t1 to t2 is the electrode positive polarity peak period Tp, the time t2 to t3 is the electrode minus polarity peak period Tpn, and the time t3 ~ T4 is the electrode negative polarity base period Tbn, the time t4 to t5 is the electrode positive polarity base period Tb, and the time after the time t5 is the electrode positive polarity peak period Tp. As shown in FIG. 5B, the pulse period signal Tf is a trigger signal that becomes a high level for a short time at time t1 and time t5. The period from time t1 to t5 is a pulse period. As shown in FIG. 5C, the timer signal Tm is a period (time t1 to time t1) determined by the electrode positive polarity peak period setting signal Tpr in FIG. 2 from the time when the pulse period signal Tf becomes high level at time t1. The value becomes 1 during the period t2), and the value determined by the electrode minus polarity peak period setting signal Tpnr in FIG. 2 from the time t2 (period t2 to t3) becomes 2, and the electrode shown in FIG. The value of the period determined by the negative polarity base period setting signal Tbnr (period from time t3 to t4) is 3, and the value is 4 from time t4 to time t5 when the pulse period signal Tf becomes high level. At time t5, the value returns to 1. Therefore, the value is 4 during the electrode positive polarity base period before time t1. In the figure, the change in the value of the timer signal Tm is shown in a stepped manner.

  As shown in FIG. 4D, the current setting signal Ir changes according to the value of the timer signal Tm, becomes the value of the electrode positive polarity base current setting signal Ibr before time t1, and the period from time t1 to t2 The value of the electrode positive polarity peak current setting signal Ipr is the value of the electrode negative polarity peak current setting signal Ipnr during the period from time t2 to t3, and the value of the electrode negative polarity base current setting signal Ibnr during the period from time t3 to t4. The period of time t4 to t5 becomes the value of the electrode plus polarity base current setting signal Ibr, and the period after time t5 becomes the value of the electrode plus polarity peak current setting signal Ipr. The values of the current setting signal Ir are all positive values. As shown in FIG. 5E, the electrode positive polarity drive signal Pd is output during a period before time t2 and during a period after time t4 to turn on the electrode positive polarity transistor PTR in FIG. As shown in FIG. 5F, the electrode minus polarity drive signal Nd is output during the period from time t2 to t4, and turns on the electrode minus polarity transistor NTR in FIG.

  According to the first embodiment described above, by forming the peak period from the electrode plus polarity peak period and the electrode minus polarity peak period, the electrode minus polarity current ratio can be set to a large value, and the electrode minus Even when the polarity current ratio is a large value, a 1-pulse 1-droplet transfer state can be achieved. Therefore, a bead shape with a small dilution rate can be formed with high quality.

[Embodiment 2]
FIG. 4 is a waveform diagram of a welding current Iw showing an AC pulse arc welding control method according to Embodiment 2 of the present invention. In the figure, the upper side from 0A shows the electrode positive polarity EP, and the lower side shows the electrode negative polarity EN. This figure shows a case where the electrode negative polarity current ratio is set larger than that in FIG. 1 described above, and the electrode positive polarity base period Tb in FIG. 1 is removed. In the figure, the electrode positive polarity peak period Tp and the electrode negative polarity peak period Tpn are the same as those in FIG. Hereinafter, an electrode negative polarity base period Tbn different from FIG. 1 will be described.

  During the electrode negative polarity base period Tbn from time t3 to t4, the electrode negative polarity base current Ibn less than the critical value is applied. The time t4 to t5 again becomes the electrode positive polarity peak period Tp, and the time t5 to t6 again becomes the electrode negative polarity peak period Tpn. The period from time t1 to t4 is one pulse period Tf. Further, the period from time t2 to t4 is the electrode minus polarity period Ten.

The electrode positive polarity peak period Tp, the electrode positive polarity peak current Ip, the electrode negative polarity peak period Tpn, the electrode negative polarity peak current Ipn, and the electrode negative polarity base current Ibn are set to appropriate values in advance. Further, the length of the pulse period Tf is feedback-controlled (arc length control) so that the average value of the absolute values of the welding voltage becomes equal to a predetermined voltage setting value. When the pulse period Tf changes, the electrode minus polarity base period Tbn changes. In the figure, the electrode negative polarity current ratio Ren is as follows.
Ren = ((Tpn · | Ipn | + Tbn · | Ibn |) / (Tp · Ip + Tpn · | Ipn | + Tbn · | Ibn |)) × 100

  Next, formation and transfer of droplets will be described with reference to FIG. In the vicinity of the end of the electrode negative polarity peak period Tpn at the time t3, the droplets go. During the electrode negative polarity base period Tbn at times t3 to t4, droplets are formed. This is set so that the electrode negative polarity base period Tbn becomes long because the electrode negative polarity current ratio is set to be large. For this reason, even if the electrode negative polarity base current Ibn is a small current value, the electrode negative polarity EN promotes melting of the welding wire tip, so that droplets are formed. During the electrode positive polarity peak period Tp from time t4 to t5, a large current is applied, so that the droplet becomes larger. In the vicinity of the end of this period, constriction occurs in the droplet, but the droplet size is too large to go. During the electrode negative polarity peak period Tpn from time t5 to t6, since the first current is applied, a strong electromagnetic pinch force acts on the constricted portion of the droplet, and the constriction rapidly proceeds and the droplet moves. That is, when the electrode negative polarity current ratio is set to a large value, droplets are also formed during the electrode negative polarity base period Tbn. For this reason, the size of the droplets to be transferred during the peak period. Becomes larger. For this purpose, two peak periods are provided, and one is set as an electrode plus polarity peak period Tp and the other is set as an electrode minus polarity peak period Tpn so that a large-sized droplet can be surely carried out. Yes. Furthermore, by changing the polarities of these two peak periods and removing the electrode positive polarity base period Tb of FIG. 1, the electrode negative polarity current ratio can be easily set to a large value. In the figure, the electrode negative polarity current ratio is changed by changing the electrode negative polarity peak period Tpn and / or the electrode negative polarity base current Ibn.

  FIG. 5 is a block diagram of a welding power source for carrying out the above-described AC pulse arc welding control method according to the second embodiment of the present invention. In the figure, the same blocks as those in FIG. 2 described above are denoted by the same reference numerals, and description thereof is omitted. In the figure, the timer circuit TM in FIG. 2 is replaced with a second timer circuit TM2 indicated by a broken line, the electrode minus polarity base period setting circuit TBNR in FIG. 2 is deleted, and the electrode plus polarity base current setting circuit IBR in FIG. The switching circuit SW in FIG. 2 is replaced with a second switching circuit SW2 indicated by a broken line, and the driving circuit DV in FIG. 2 is replaced by a second driving circuit DV2 indicated by a broken line. Hereinafter, the blocks different from those in FIG. 2 will be described with reference to FIG.

  The second timer circuit TM2 receives the pulse period signal Tf, the electrode positive polarity peak period setting signal Tpr and the electrode minus polarity peak period setting signal Tpnr, and each time the pulse period signal Tf changes to a high level for a short time, The value becomes 1 during the period determined by the electrode positive polarity peak period setting signal Tpr, and subsequently becomes 2 during the period determined by the electrode negative peak period setting signal Tpnr. During the period, a timer signal Tm whose value is 3 is output. The second switching circuit SW2 receives the timer signal Tm, the electrode positive polarity peak current setting signal Ipr, the electrode negative polarity peak current setting signal Ipnr, and the electrode negative polarity base current setting signal Ibnr, and inputs the timer signal Tm. = 1, the electrode positive polarity peak current setting signal Ipr is output as the current setting signal Ir. When the timer signal Tm = 2, the electrode negative polarity peak current setting signal Ipnr is output as the current setting signal Ir. When the signal Tm = 3, the electrode negative polarity base current setting signal Ibnr is output as the current setting signal Ir. The second drive circuit DV2 receives the timer signal Tm as an input, and outputs the electrode positive polarity drive signal Pd when the timer signal Tm = 1, and the electrode negative polarity drive when the timer signal Tm = 2 or 3. The signal Nd is output. Accordingly, the electrode positive polarity peak period becomes the electrode positive polarity, and the electrode negative polarity peak period and the electrode negative polarity base period become the electrode negative polarity.

  FIG. 6 is a timing chart of each signal of the welding power source described above with reference to FIG. (A) shows the welding current Iw, (B) shows the pulse period signal Tf, (C) shows the timer signal Tm, (D) shows the current setting signal Ir, FIG. 4E shows the electrode positive polarity drive signal Pd, and FIG. 4F shows the electrode negative polarity drive signal Nd. Hereinafter, a description will be given with reference to FIG.

  As shown in FIG. 6A, before the time t1, the electrode minus polarity base period Tbn is reached, the times t1 to t2 are the electrode plus polarity peak period Tp, the times t2 to t3 are the electrode minus polarity peak period Tpn, and the time t3 ˜t4 is the electrode negative polarity base period Tbn, and after time t4 is the electrode positive polarity peak period Tp. As shown in FIG. 5B, the pulse period signal Tf is a trigger signal that becomes a high level for a short time at time t1 and time t4. The period between times t1 and t4 is a pulse period. As shown in FIG. 6C, the timer signal Tm is a period (time t1 to time t1) determined by the electrode positive polarity peak period setting signal Tpr in FIG. 5 from the time when the pulse period signal Tf becomes high level at time t1. The value becomes 1 during the period t2), and the value 2 becomes the period determined by the electrode negative polarity peak period setting signal Tpnr in FIG. 5 from the time t2 (the period from the time t2 to the time t3). The value is 3 during a period until time t4 when the signal Tf becomes High level, and the value returns to 1 at time t4. Therefore, the value is 3 during the electrode negative polarity base period before time t1. In the figure, the change in the value of the timer signal Tm is shown in a stepped manner.

  As shown in FIG. 4D, the current setting signal Ir changes depending on the value of the timer signal Tm, becomes the value of the electrode negative polarity base current setting signal Ibnr before the time t1, and the period from the time t1 to the time t2 It becomes the value of the electrode positive polarity peak current setting signal Ipr, the value of the electrode negative polarity peak current setting signal Ipnr during the period from time t2 to t3, and the value of the electrode negative polarity base current setting signal Ibnr during the period from time t3 to t4. The period after time t4 becomes the value of the electrode positive polarity peak current setting signal Ipr. The values of the current setting signal Ir are all positive values. As shown in FIG. 5E, the electrode positive polarity drive signal Pd is output during the period from time t1 to t2 and the period after time t4 to turn on the electrode positive polarity transistor PTR in FIG. As shown in FIG. 5F, the electrode minus polarity drive signal Nd is output during the period before time t1 and the period between times t2 and t4, and turns on the electrode minus polarity transistor NTR in FIG.

  According to the second embodiment described above, in addition to the effects of the first embodiment, the electrode negative polarity current ratio is set to a larger value than in the first embodiment by removing the electrode positive polarity base period. Is possible. Therefore, a bead shape having a smaller dilution rate can be formed with high quality.

It is a welding current waveform figure which shows the alternating current pulse arc welding control method which concerns on Embodiment 1 of this invention. It is a block diagram of the welding power supply which concerns on Embodiment 1 of this invention. It is a timing chart of each signal in the welding power supply of FIG. It is a welding current waveform figure which shows the alternating current pulse arc welding control method which concerns on Embodiment 2 of this invention. It is a block diagram of the welding power supply which concerns on Embodiment 2 of this invention. It is a timing chart of each signal in the welding power supply of FIG. It is an electric current and voltage waveform figure in the alternating current pulse arc welding of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll DV Drive circuit DV2 2nd drive circuit EI Current error amplification circuit Ei Current error amplification signal EN Electrode minus polarity EP Electrode plus polarity EV Voltage error amplification circuit Ev Voltage error amplification Signal FC Feeding control circuit Fc Feeding control signal FR Feeding speed setting circuit Fr Feeding speed setting signal Ib Base current Ib Electrode plus polarity base current Ibn Electrode minus polarity base current IBNR Electrode minus polarity base current setting circuit Ibnr Electrode minus polarity Base current setting signal IBR Electrode plus polarity base current setting circuit Ibr Electrode plus polarity base current setting signal ID Current detection circuit Id Current detection signal INT Inverter transformer INV Inverter circuit Ip Peak current Ip Electrode plus polarity peak current Ipn Electrode minus polarity peak current IP NR Electrode minus polarity peak current setting circuit Ipnr Electrode minus polarity peak current setting signal IPR Electrode plus polarity peak current setting circuit Ipr Electrode plus polarity peak current setting signal Ir Current setting signal Iw Welding current Nd Electrode minus polarity drive signal NTR Electrode minus polarity transistor Pd electrode plus polarity drive signal PTR electrode plus polarity transistor Ren electrode minus polarity current ratio SW switching circuit SW2 second switching circuit Tb base period Tb electrode plus polarity base period Tbn electrode minus polarity base period TBNR electrode minus polarity base period setting circuit Tbnr electrode Negative polarity base period setting signal Ten electrode Negative polarity period Tep Electrode positive polarity period Tf Pulse period (signal)
TM timer circuit Tm timer signal TM2 second timer circuit Tp peak period Tp electrode plus polarity peak period Tpn electrode minus polarity peak period TPNR electrode minus polarity peak period setting circuit Tpnr electrode minus polarity peak period setting signal TPR electrode plus polarity peak period setting circuit Tpr electrode positive polarity peak period setting signal Vav welding voltage average value VAV voltage averaging circuit Vav voltage average value signal Vb base voltage Vbn electrode negative polarity base voltage VD voltage detection circuit Vd voltage detection signal VF voltage / frequency conversion circuit Vp peak voltage VR Voltage setting circuit Vr Voltage setting signal Vw Welding voltage WL Reactor WM Wire feed motor

Claims (4)

In the AC pulsed arc welding control method for welding by feeding a welding wire and energizing an AC welding current,
During the electrode positive polarity peak period, apply an electrode positive polarity peak current above the critical value,
Next, during the electrode negative polarity peak period, apply an electrode negative polarity peak current above the critical value,
Subsequently, during the electrode negative polarity base period, an electrode negative polarity base current less than the critical value is applied,
Subsequently, during the electrode positive polarity base period, an electrode positive polarity base current less than the critical value is applied,
Welding by repeating these energizations as one cycle,
AC pulse arc welding control method characterized by the above. Changing the electrode negative polarity current ratio by adjusting at least one of the electrode negative polarity peak period, the electrode negative polarity base period, or the electrode negative polarity base current;
The AC pulse arc welding control method according to claim 1, wherein: In the AC pulsed arc welding control method for welding by feeding a welding wire and energizing an AC welding current,
During the electrode positive polarity peak period, apply an electrode positive polarity peak current above the critical value,
Next, during the electrode negative polarity peak period, apply an electrode negative polarity peak current above the critical value,
Subsequently, during the electrode negative polarity base period, an electrode negative polarity base current less than the critical value is applied,
Welding by repeating these energizations as one cycle,
AC pulse arc welding control method characterized by the above. Changing the electrode negative polarity current ratio by adjusting the electrode negative polarity peak period and / or the electrode negative polarity base current;
The AC pulse arc welding control method according to claim 3.

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