JP7482582B2 - Arc welding equipment - Google Patents

Description

The present invention relates to an arc welding device that performs welding with a pulse arc welding period and a short circuit transfer arc welding period as one cycle.

A welding method is used in which the welding wire is fed and a period of pulse arc welding and a period of short circuit transfer arc welding are alternately switched (see, for example, Patent Document 1). With this welding method, it is possible to form beautiful scale-like beads. Furthermore, with this welding method, it is possible to control the heat input to the base material by adjusting the ratio of the period of pulse arc welding and the period of short circuit transfer arc welding.

The invention of Patent Document 2 discloses an arc welding method in which welding is performed by alternating between a period in which the welding wire is fed forward to perform pulse arc welding and a period in which the welding wire is fed forward and backward to perform short circuit transfer arc welding. In this arc welding method, the wire is fed forward during the arc period and backward during the short circuit period during short circuit transfer arc welding. Furthermore, switching from pulse arc welding to short circuit transfer arc welding is performed during the base period after droplets are transferred by pulse arc welding.

JP 2005-313179 A JP 2015-205347 A

As welding progresses, the temperature of the base material rises, which can lead to unstable bead back waves and burn-through. This is particularly noticeable with base materials that have a low melting point, such as aluminum. The same is true when welding involves repeating a pulse arc welding period and a short-circuit transfer arc welding period as one cycle. Therefore, in actual construction, welding conditions such as the welding current and welding voltage are set in detail as welding progresses. As a result, it takes a lot of time to set the welding conditions.

The present invention aims to provide an arc welding device that can suppress the unstable occurrence of back seams and burn-through when welding is performed by repeating a pulse arc welding period and a short circuit transfer arc welding period as one cycle, even if the temperature of the base material rises as welding progresses, without detailed setting of the welding conditions.

In order to solve the above-mentioned problems, the invention of claim 1 comprises:
In an arc welding apparatus which performs welding with a pulse arc welding period and a short circuit transfer arc welding period as one cycle,
The arc welding apparatus corrects and controls the time ratio of the period and/or the short circuit transfer arc welding period based on an average value of the welding voltage.
The correction control is a control to shorten the period and/or a control to increase the time ratio when the average value of the welding voltage becomes equal to or greater than a reference voltage value.
The arc welding device is characterized by the above.
Ahh

The invention of claim 2 is as follows:
The average value of the welding voltage is an average value for each cycle of the pulse arc welding period and the short circuit transfer arc welding period.
2. The arc welding device according to claim 1 .

The invention of claim 3 is as follows:
The average value of the welding voltage is an average value during the pulse arc welding period.
2. The arc welding device according to claim 1 .

According to the present invention, when welding is performed by repeating a pulse arc welding period and a short circuit transfer arc welding period as one cycle, it is possible to suppress the unstable occurrence of back waves and burn-through even if the temperature of the base material rises as welding progresses, without detailed setting of the welding conditions.

1 is a block diagram of an arc welding device according to a first embodiment of the present invention. 2 is a timing chart of each signal when switching from a pulse arc welding period Ta to a short circuit transfer arc welding period Tc in the arc welding device of FIG. 1 . 2 is a timing chart of each signal when switching from a short circuit transfer arc welding period Tc to a pulse arc welding period Ta in the arc welding device of FIG. 1 .

The following describes an embodiment of the present invention with reference to the drawings.

[First embodiment]
1 is a block diagram of an arc welding device according to a first embodiment of the present invention. Each block will be described below with reference to the diagram.

The power supply main circuit PM receives a three-phase 200V or other commercial power supply (not shown), performs output control by inverter control or the like according to an error amplified signal Ea (described later), and outputs an output voltage E. Although not shown, this power supply main circuit PM includes a primary rectifier that rectifies the commercial power supply, a smoothing capacitor that smooths the rectified DC, an inverter circuit driven by the error amplified signal Ea described above that converts the smoothed DC into high-frequency AC, a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for welding, and a secondary rectifier that rectifies the stepped-down high-frequency AC into DC.

The reactor WL smoothes the above welding current Iw to maintain a stable arc 3.

The feed motor WM receives the feed control signal Fc (described later) as an input, and feeds the welding wire 1 at a feed speed Fw by mainly feeding in the forward direction during pulse arc welding and feeding in the reverse direction during short circuit transfer arc welding. A motor with fast transient response is used for the feed motor WM. In order to increase the rate of change of the feed speed Fw of the welding wire 1 and to speed up the reversal of the feed direction, the feed motor WM may be installed near the tip of the welding torch 4. In some cases, two feed motors WM are used to create a push-pull type feed system.

The welding wire 1 is fed through the welding torch 4 by the rotation of the feed roll 5 connected to the feed motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power feed tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw flows. A shielding gas (not shown) is ejected from the tip of the welding torch 4 to shield the arc 3 from the atmosphere. If the material of the welding wire 1 is steel, a mixture of argon gas and carbon dioxide gas is used as the shielding gas, and if the material of the welding wire 1 is aluminum, argon gas is used.

The output voltage setting circuit ER outputs a predetermined output voltage setting signal Er. The output voltage detection circuit ED detects and smoothes the output voltage E and outputs an output voltage detection signal Ed.

The voltage error amplifier circuit EV receives the output voltage setting signal Er and the output voltage detection signal Ed as inputs, amplifies the error between the output voltage setting signal Er(+) and the output voltage detection signal Ed(-), and outputs the voltage error amplification signal Ev.

The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The short circuit determination circuit SD receives the voltage detection signal Vd and outputs a short circuit determination signal Sd that goes to High level when this value is less than a predetermined short circuit determination value (approximately 10 V) and determines that the short circuit is in a short circuit period, and goes to Low level when this value is equal to or greater than this value and determines that the arc period is in an arc period.

The forward acceleration period setting circuit TSUR outputs a predetermined forward acceleration period setting signal Tsur.

The forward deceleration period setting circuit TSDR outputs a predetermined forward deceleration period setting signal Tsdr.

The reverse acceleration period setting circuit TRUR outputs a predetermined reverse acceleration period setting signal Trur.

The reverse feed deceleration period setting circuit TRDR outputs a predetermined reverse feed deceleration period setting signal Trdr.

The forward transmission peak value setting circuit WSR receives the timer signal Tm (described later) and the short circuit discrimination signal Sd described above as inputs, and outputs a forward transmission peak value setting signal Wsr that is a predetermined initial value during the period from when the timer signal Tm changes to a low level (short circuit transition arc welding period Tc) until the short circuit discrimination signal Sd first changes to a high level (short circuit period), and that is a predetermined steady value during other periods.

The reverse transmission peak value setting circuit WRR outputs a predetermined reverse transmission peak value setting signal Wrr.

The short-circuit arc feed speed setting circuit FCR receives the forward feed acceleration period setting signal Tsur, the forward feed deceleration period setting signal Tsdr, the reverse feed acceleration period setting signal Trur, the reverse feed deceleration period setting signal Trdr, the forward feed peak value setting signal Wsr, the reverse feed peak value setting signal Wrr, and the short circuit determination signal Sd, and outputs a feed speed pattern generated by the following process as a short-circuit arc feed speed setting signal Fcr. When the short-circuit arc feed speed setting signal Fcr is a positive value, it is a forward feed period, and when it is a negative value, it is a reverse feed period.
1) During the forward acceleration period Tsu determined by the forward acceleration period setting signal Tsur, a short-circuit arc feed speed setting signal Fcr is output which linearly accelerates from 0 (however, immediately after switching to the short-circuit transfer arc welding period Tc, the pulse feed speed setting signal Far is output) to the forward feed peak value Wsp, which is a positive value determined by the forward feed peak value setting signal Wsr.
2) Subsequently, during the forward peak period Tsp, the short-circuit arc feed rate setting signal Fcr for maintaining the forward peak value Wsp is output.
3) When the short circuit determination signal Sd changes from a low level (arc period) to a high level (short circuit period), the process transitions to a forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr, and the short circuit arc feed speed setting signal Fcr is output, which linearly decelerates the feed speed from the forward feed peak value Wsp to 0.
4) Subsequently, during the reverse acceleration period Tru determined by the reverse acceleration period setting signal Trur, a short-circuit arc feed speed setting signal Fcr is output which linearly accelerates from 0 to a reverse peak value Wrp of a negative value determined by the reverse peak value setting signal Wrr.
5) Subsequently, during the reverse feed peak period Trp, the short-circuit arc feed speed setting signal Fcr for maintaining the above-mentioned reverse feed peak value Wrp is output.
6) When the short circuit determination signal Sd changes from a high level (short circuit period) to a low level (arc period), the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr begins, and the short circuit arc feed speed setting signal Fcr that linearly decelerates the reverse feed speed from the above-mentioned reverse feed peak value Wrp to 0 is output.
7) By repeating the above steps 1) to 6), a short-circuit arc feed rate setting signal Fcr is generated having a feed pattern that changes like a positive and negative trapezoidal wave.

The current-down resistor R is inserted between the reactor WL and the welding torch 4. The value of this current-down resistor R is set to a value (approximately 0.5 to 3 Ω) that is 50 times larger than the resistance value (approximately 0.01 to 0.03 Ω) of the current path of the welding current Iw during the short circuit period. When this current-down resistor R is inserted in the current path of the welding current Iw, the energy stored in the reactor WL and the reactor of the welding cable is rapidly consumed.

The transistor TR is connected in parallel with the current reducing resistor R and is controlled to be turned on or off according to the drive signal Dr described below.

The constriction detection circuit ND receives the above short circuit determination signal Sd, the above voltage detection signal Vd, and the above current detection signal Id as inputs, and outputs a constriction detection signal Nd that determines that the constriction formation state has reached the reference state when the voltage rise value of the voltage detection signal Vd reaches a reference value when the short circuit determination signal Sd is at a high level (short circuit period) and goes to a high level, and goes to a low level when the short circuit determination signal Sd changes to a low level (arc period). In addition, the constriction detection signal Nd may be changed to a high level when the differential value of the voltage detection signal Vd during the short circuit period reaches a corresponding reference value. Furthermore, the value of the voltage detection signal Vd may be divided by the value of the current detection signal Id to calculate the resistance value of the droplet, and the constriction detection signal Nd may be changed to a high level when the differential value of this resistance value reaches a corresponding reference value.

The low-level current setting circuit ILR outputs a predetermined low-level current setting signal Ilr. The current comparison circuit CM receives this low-level current setting signal Ilr and the current detection signal Id as inputs, and outputs a current comparison signal Cm that goes to a high level when Id<Ilr and a low level when Id≧Ilr.

The drive circuit DR receives the current comparison signal Cm and the constriction detection signal Nd as inputs, and outputs a drive signal Dr to the base terminal of the transistor TR. The drive signal Dr changes to a low level when the constriction detection signal Nd changes to a high level, and then changes to a high level when the current comparison signal Cm changes to a high level. Therefore, when a constriction is detected, the drive signal Dr goes to a low level, the transistor TR is turned off, and the current-reducing resistor R is inserted in the current path, so that the welding current Iw suddenly decreases. Then, when the value of the suddenly reduced welding current Iw decreases to the value of the low-level current setting signal Ilr, the drive signal Dr goes to a high level, the transistor TR is turned on, and the current-reducing resistor R is short-circuited and returns to the normal state.

The short circuit arc current setting circuit ICR receives the short circuit determination signal Sd, the low level current setting signal Ilr, and the constriction detection signal Nd, performs the following processing, and outputs a short circuit arc current setting signal Icr.
1) When the short circuit determination signal Sd is at a low level (arc period), a short circuit arc current setting signal Icr which becomes a low level current setting signal Ilr is output.
2) When the short circuit determination signal Sd changes to a high level (short circuit period), a short circuit arc current setting signal Icr is output which has a predetermined initial current setting value during a predetermined initial period, and thereafter rises to a predetermined short circuit peak setting value at a predetermined short circuit slope and maintains that value.
3) Thereafter, when the squeezing detection signal Nd changes to a high level, the short-circuit arc current setting signal Icr having the value of the low-level current setting signal Ilr is output.

The current drop time setting circuit TDR outputs a predetermined current drop time setting signal Tdr.

The small current period circuit STD receives the above short circuit detection signal Sd and the above current drop time setting signal Tdr as inputs, and outputs a small current period signal Std that goes to a high level when the time determined by the current drop time setting signal Tdr has elapsed since the short circuit detection signal Sd changed to a low level (arc period), and then goes to a low level when the short circuit detection signal Sd goes to a high level (short circuit period).

The peak period setting circuit TPR receives the final pulse period signal Stf (described later) as input, and outputs a peak period setting signal Tpr that is a predetermined steady peak period when the final pulse period signal Stf is at a low level, and is a predetermined final peak period when the final pulse period signal Stf is at a high level.

The peak rise period setting circuit TUR receives the final pulse cycle signal Stf (described later) as input, and outputs a peak rise period setting signal Tur that is a predetermined steady peak rise period when the final pulse cycle signal Stf is at a low level, and is a predetermined final peak rise period when the final pulse cycle signal Stf is at a high level.

The peak falling period setting circuit TPDR receives the final pulse period signal Stf (described later) as input, and outputs a peak falling period setting signal Tpdr that has a predetermined steady peak falling period when the final pulse period signal Stf is at a low level, and a predetermined final peak falling period when the final pulse period signal Stf is at a high level.

The base period setting circuit TBR outputs a predetermined base period setting signal Tbr.

The peak current setting circuit IPR performs modulation control using the voltage error amplification signal Ev as input, and outputs the peak current setting signal Ipr. Modulation control is performed by integrating the voltage error amplification signal Ev as follows: Ipr = Ip0 - ∫Kp Ev dt. Ip0 is the initial value of the peak current value, and Kp is a constant for adjusting the gain of the peak current modulation control to an appropriate value.

The base current setting circuit IBR receives the voltage error amplification signal Ev, performs modulation control, and outputs the base current setting signal Ibr. Modulation control is performed by integrating the voltage error amplification signal Ev as follows: Ibr = Ib0 - ∫Kb Ev dt. Ib0 is the initial value of the base current, and Kb is a constant for adjusting the gain of the base current modulation control to an appropriate value.

The pulse initial reverse feed period setting circuit TARR outputs a predetermined pulse initial reverse feed period setting signal Tarr.

The pulse initial current period setting circuit TASR outputs a predetermined pulse initial current period setting signal Tasr. The pulse initial current setting circuit IASR outputs a predetermined pulse initial current setting signal Iasr.

The pulse current setting circuit IAR receives as input a timer signal Tm, which will be described later, the peak period setting signal Tpr, the peak rise period setting signal Tur, the peak fall period setting signal Tpdr, the base period setting signal Tbr, the peak current setting signal Ipr, the base current setting signal Ibr, the pulse initial current period setting signal Tasr, and the pulse initial current setting signal Iasr, performs the following processing, and outputs a pulse current setting signal Iar.
1) When the timer signal Tm is at a low level (short-circuit transfer arc welding period), the value of the pulse initial current setting signal Iasr is output as the pulse current setting signal Iar.
2) During the pulse initial current period Tas determined by the pulse initial current period setting signal Tasr from the point at which the timer signal Tm changes from a low level to a high level (pulse arc welding period), the value of the pulse initial current setting signal Iasr is output as the pulse current setting signal Iar.
3) Subsequently, during the peak rise period Tu determined by the peak rise period setting signal Tur, a pulse current setting signal Iar that rises from the value of the pulse initial current setting signal Iasr (from the second pulse period, the base current setting signal Ibr) to the value of the peak current setting signal Ipr is output.
4) Subsequently, during the peak period Tp determined by the peak period setting signal Tpr, the pulse current setting signal Iar that maintains the value of the peak current setting signal Ipr is output.
5) Subsequently, during the peak falling period Tpd determined by the peak falling period setting signal Tpdr, the pulse current setting signal Iar is output, which decreases from the value of the peak current setting signal Ipr to the value of the base current setting signal Ibr.
6) Subsequently, during the base period Tb determined by the base period setting signal Tbr, the pulse current setting signal Iar that maintains the value of the base current setting signal Ibr is output.
7) The above steps 3) to 6) constitute one pulse period, and are repeated until the timer signal Tm changes to a low level.

The average voltage detection circuit VAD receives the voltage detection signal Vd and the timer signal Tm as inputs, detects the average value of the voltage detection signal Vd for each cycle of the timer signal Tm, or the average value of the voltage detection signal Vd when the timer signal Tm is at a high level (pulse arc welding period), and outputs the average voltage detection signal Vad. One cycle of the timer signal Tm is one cycle of the pulse arc welding period Ta and the short circuit transfer arc welding period Tc.

The voltage rise determination circuit HD receives the average voltage detection signal Vad and outputs a voltage rise determination signal Hd that goes to a high level when the value of the average voltage detection signal Vad is equal to or greater than a predetermined reference voltage value Vt.

The period setting circuit TACR receives the voltage rise detection signal Hd and outputs a predetermined period setting value as the period setting signal Tacr when the voltage rise detection signal Hd is at a low level, and outputs a predetermined corrected period setting value as the period setting signal Tacr when the voltage rise detection signal Hd is at a high level. The period setting value is greater than the corrected period setting value.

The time ratio setting circuit DTR receives the voltage rise detection signal Hd and outputs a predetermined time ratio setting value as the time ratio setting signal Dtr when the voltage rise detection signal Hd is at a low level, and outputs a predetermined modified time ratio setting value as the time ratio setting signal Dtr when the voltage rise detection signal Hd is at a high level. The time ratio setting signal Dtr is a percentage. The time ratio setting value is < the modified time ratio setting value. The time ratio is the time ratio that the short circuit transfer arc welding period occupies in the cycle.

The pulse arc welding period setting circuit TAR receives the above cycle setting signal Tacr and the above time ratio setting signal Dtr as inputs, calculates Tar = Tacr · (1 - (Dtr / 100)), and outputs the pulse arc welding period setting signal Tar.

The short circuit transfer arc welding period setting circuit TCR receives the above cycle setting signal Tacr and the above time ratio setting signal Dtr as inputs, calculates Tcr = Tacr · (Dtr / 100), and outputs the short circuit transfer arc welding period setting signal Tcr.

The timer circuit TM receives as input the pulse arc welding period setting signal Tar, the short circuit transfer arc welding period setting signal Tcr, the short circuit determination signal Sd, the pulse current setting signal Iar, and the base current setting signal Ibr,
After the time period determined by the short circuit transfer arc welding period setting signal Tcr has elapsed since the time the timer signal Tm changed to a low level (short circuit transfer arc welding period Tc), the timer signal Tm changes to a high level when the short circuit determination signal Sd first changes to a low level (arc period),
When a new pulse period starts after a period determined by the pulse arc welding period setting signal Tar has elapsed from the time when the timer signal Tm changes to a High level (pulse arc welding period Ta), the final pulse period Tsf is entered, and when the pulse current setting signal Iar becomes equal to the value of the base current setting signal Ibr during the final pulse period Tsf, the final pulse period Tsf ends and the timer signal Tm changes to a Low level,
A final pulse cycle signal Stf that is at a high level only during the final pulse cycle Tsf is output.
Therefore, the pulse arc welding period Ta is the period of the pulse arc welding period setting signal Tar + the period until the final pulse period Tsf starts + the period of the final pulse period Tsf. The short circuit transfer arc welding period Tc is the period of the short circuit transfer arc welding period setting signal Tcr + the period until the first short circuit period ends thereafter.

The pulse initial reverse feed speed setting signal FARR outputs a predetermined pulse initial reverse feed speed setting signal Farr of a negative value. The pulse positive feed speed setting circuit FASR outputs a predetermined pulse positive feed speed setting signal Fasr of a positive value.

The pulse feed speed setting circuit FAR receives the timer signal Tm, the pulse initial reverse feed period setting signal Tarr, the pulse initial reverse feed speed setting signal Farr, and the pulse forward feed speed setting signal Fasr as inputs, performs the following processing, and outputs the pulse feed speed setting signal Far.
1) When the timer signal Tm is at a low level (short-circuit transfer arc welding period), the value of the pulse initial reverse feed speed setting signal Farr is output as the pulse feed speed setting signal Far.
2) During the pulse initial reverse feed period Tair determined by the pulse initial reverse feed period setting signal Tarr from the point in time when the timer signal Tm changes from a low level to a high level (pulse arc welding period), the value of the pulse initial reverse feed speed setting signal Farr is output as the pulse feed speed setting signal Far.
3) Subsequently, during the period until the timer signal Tm changes to the low level, the value of the pulse positive feed speed setting signal Fasr is output as the pulse feed speed setting signal Far.

The feed speed setting circuit FR receives the timer signal Tm, the short circuit arc feed speed setting signal Fcr, and the pulse feed speed setting signal Far as inputs, and outputs the pulse feed speed setting signal Far as the feed speed setting signal Fr when the timer signal Tm is at a high level (pulse arc welding period Ta), and outputs the short circuit arc feed speed setting signal Fcr as the feed speed setting signal Fr when the timer signal Tm is at a low level (short circuit transition arc welding period Tc).

The feed control circuit FC receives the feed speed setting signal Fr as an input and outputs a feed control signal Fc to the feed motor WM to feed the welding wire 1 at a feed speed Fw that corresponds to the value of the feed speed setting signal Fr.

The current setting circuit IR receives the timer signal Tm, the short circuit arc current setting signal Icr, and the pulse current setting signal Iar as inputs, and outputs the pulse current setting signal Iar as the current setting signal Ir when the timer signal Tm is at a high level (pulse arc welding period Ta), and outputs the short circuit arc current setting signal Icr as the current setting signal Ir when the timer signal Tm is at a low level (short circuit transfer arc welding period Tc).

The current error amplifier circuit EI receives the current setting signal Ir and the current detection signal Id as inputs, amplifies the error between the current setting signal Ir(+) and the current detection signal Id(-), and outputs a current error amplification signal Ei.

The power supply characteristics switching circuit SW receives as input the timer signal Tm, the current error amplified signal Ei, the voltage error amplified signal Ev, the short circuit determination signal Sd, and the small current period signal Std, performs the following processing, and outputs an error amplified signal Ea.
1) While the timer signal Tm is at a low level and the short circuit determination signal Sd changes to a high level (short circuit period) until the short circuit determination signal Sd changes to a low level (arcing period) and the above-mentioned delay period has elapsed, the current error amplified signal Ei is output as the error amplified signal Ea.
2) During the subsequent large current arc period, the voltage error amplified signal Ev is output as the error amplified signal Ea.
3) During the subsequent small current arc period in which the small current period signal Std is at a high level, the current error amplified signal Ei is output as the error amplified signal Ea.
4) During the period from when the timer signal Tm changes to low level to when the short circuit determination signal Sd first goes high level and while the timer signal Tm is at high level, the current error amplified signal Ei is output as the error amplified signal Ea.
With this circuit, the characteristics of the welding power source during the short circuit transfer arc welding period Tc become constant current characteristics during the period from the start of the short circuit transfer arc welding period Tc to the first occurrence of a short circuit, the short circuit period, the delay period, and the small current arc period, and become constant voltage characteristics during the other large current arc periods (the period from the time when the short circuit determination signal Sd changes from High to Low and the above-mentioned delay time has elapsed to the time when the small current period signal Std changes from Low to High while the timer signal Tm is Low). Also, the characteristics of the welding power source during the pulse arc welding period Ta become constant current characteristics.

Figure 2 is a timing chart of each signal when switching from the pulse arc welding period Ta to the short circuit transfer arc welding period Tc in the arc welding device of Figure 1. Figure (A) shows the change over time of the feed speed Fw, Figure (B) shows the change over time of the welding current Iw, Figure (C) shows the change over time of the welding voltage Vw, Figure (D) shows the change over time of the short circuit discrimination signal Sd, Figure (E) shows the change over time of the small current period signal Std, Figure (F) shows the change over time of the timer signal Tm, and Figure (G) shows the change over time of the final pulse period signal Stf. The operation of each signal will be explained below with reference to the figure.

At time t0, a new pulse cycle is started after the time elapsed from the time when the timer signal Tm shown in FIG. 1F changes to a high level (the start time of the pulse arc welding period Ta) reaches the period determined by the pulse arc welding period setting signal Tar in FIG. 1. At time t0, as shown in FIG. 1G, the final pulse cycle signal Stf changes to a high level and the final pulse cycle Tsf begins. During the final pulse cycle Tsf from time t0 to t1, as shown in FIG. 1B, during the predetermined final peak rise period Tu, a transition current that rises to the peak current value Ip determined by the peak current setting signal Ipr in FIG. 1 flows. During the subsequent predetermined final peak period Tp, the above peak current value Ip flows. During the subsequent predetermined final peak fall period Tpd, a transition current that falls from the above peak current value Ip to the base current value Ib determined by the base current setting signal Ibr in FIG. 1 flows. At time t1, when the final peak falling period Tpd ends and the welding current Iw becomes the above-mentioned base current Ib, as shown in FIG. 1(G), the final pulse period signal Stf returns to a low level and the final pulse period Tsf ends. The values of the final peak rising period Tu, the final peak period Tp, and the final peak falling period Tpd during the final pulse period Tsf are set to values that prevent the droplets formed during the final pulse period Tsf from transferring.

At time t1, the timer signal Tm shown in FIG. 1 (F) changes to a high level (pulse arc welding period Ta) and the period determined by the pulse arc welding period setting signal Tar in FIG. 1 has elapsed, and a new pulse period begins, the final pulse period Tsf, during which the pulse current setting signal Iar in FIG. 1 becomes equal to the value of the base current setting signal Ibr in FIG. 1. Then, at time t1, as shown in FIG. 1 (F), the timer signal Tm changes from a high level to a low level. Therefore, at time t1, the pulse arc welding period Ta is switched to the short circuit transfer arc welding period Tc. In the figure, during the period before time t1, as shown in FIG. 1 (A), the feed speed Fw is forward fed at a constant speed determined by the pulse forward feed speed setting signal Fasr in FIG. 1. As shown in FIG. 1 (C), the welding voltage Vw has a waveform similar to that of the welding current Iw. As shown in FIG. 1D, the short circuit detection signal Sd remains at a low level because the arc period continues. As shown in FIG. 1E, the small current period signal Std remains at a low level.

At time t1, as shown in FIG. 1(F), the timer signal Tm changes to a low level, and the short circuit transition arc welding period Tc begins. In response to this, as shown in FIG. 1(A), the feed speed Fw is accelerated to the forward feed peak value Wsp determined by the forward feed peak value setting signal Wsr in FIG. 1, and maintains that value until a short circuit occurs at time t3. The forward feed peak value Wsp during this period is a predetermined initial value, since it is the period from when the timer signal Tm changes to a low level to when the short circuit determination signal Sd first changes to a high level (short circuit period). The forward feed peak value Wsp thereafter becomes a predetermined steady value. The initial value is set independently of the steady value so that the welding state during this period is stable. The initial value may be set to the steady value.

During the period from when the short circuit transfer arc welding period Tc starts at time t1 until the first short circuit occurs at time t3, as shown in the same figure (B), the welding current Iw is a low-level current value determined by the low-level current setting signal Ilr in Figure 1, because the welding power source has a constant current characteristic.

The feed speed Fw shown in FIG. 1A is controlled by the value of the short circuit arc feed speed setting signal Fcr output from the short circuit arc feed speed setting circuit FCR in FIG. 1. The feed speed Fw is formed by the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur in FIG. 1, the forward feed peak period Tsp that continues until a short circuit occurs, the forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr in FIG. 1, the reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur in FIG. 1, the reverse feed peak period Trp that continues until an arc occurs, and the reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr in FIG. 1. Furthermore, the forward feed peak value Wsp is determined by the forward feed peak value setting signal Wsr in FIG. 1, and the reverse feed peak value Wrp is determined by the reverse feed peak value setting signal Wrr in FIG. 1. As a result, the short circuit arc feed speed setting signal Fcr has a feed pattern that changes in a substantially trapezoidal wave shape between positive and negative.

[Operation during the short circuit period from time t3 to t6]
If a short circuit occurs at time t3 during the forward feed peak period Tsp, as shown in Fig. 1C, the welding voltage Vw suddenly drops to a short circuit voltage value of several volts, and the short circuit determination signal Sd changes to a high level (short circuit period) as shown in Fig. 1D. In response to this, the system transitions to a predetermined forward feed deceleration period Tsd from time t3 to t4, and the feed speed Fw decelerates from the forward feed peak value Wsp to 0 as shown in Fig. 1A. For example, the forward feed deceleration period Tsd is set to 1 ms.

As shown in FIG. 1A, the feed speed Fw enters a predetermined reverse acceleration period Tru from time t4 to t5, and accelerates from 0 to the reverse peak value Wrp. During this period, the short circuit period continues. For example, the reverse acceleration period Tru is set to 1 ms.

When the reverse feed acceleration period Tru ends at time t5, as shown in FIG. 1A, the feed speed Fw enters the reverse feed peak period Trp and becomes the reverse feed peak value Wrp described above. The reverse feed peak period Trp continues until an arc occurs at time t6. Therefore, the period from time t3 to t6 is the short circuit period. The reverse feed peak period Trp is not a predetermined value, but is about 4 ms. For example, the reverse feed peak value Wrp is set to -60 m/min.

As shown in FIG. 1B, the welding current Iw during the short circuit period from time t3 to t6 is a predetermined initial current value during a predetermined initial period. Thereafter, the welding current Iw rises at a predetermined short circuit slope, and when it reaches a predetermined short circuit peak value, it maintains that value.

As shown in FIG. 1C, the welding voltage Vw rises from the point where the welding current Iw reaches its peak value during a short circuit. This is because a constriction gradually forms in the droplet at the tip of the welding wire 1 due to the reverse feed of the welding wire 1 and the pinching force caused by the welding current Iw.

After that, when the voltage rise value of the welding voltage Vw reaches the reference value, it is determined that the state of the necking has reached the reference state, and the necking detection signal Nd in Figure 1 changes to a high level.

In response to the constriction detection signal Nd becoming high level, the drive signal Dr in FIG. 1 becomes low level, so that the transistor TR in FIG. 1 becomes off and the current reducing resistor R in FIG. 1 is inserted into the current path. At the same time, the short-circuit arc current setting signal Icr in FIG. 1 becomes small to the value of the low-level current setting signal Ilr. For this reason, as shown in FIG. 1 (B), the welding current Iw suddenly decreases from the peak value at the time of short circuit to the low-level current value. Then, when the welding current Iw decreases to the low-level current value, the drive signal Dr returns to high level, so that the transistor TR becomes on and the current reducing resistor R is short-circuited. As shown in FIG. 1 (B), the welding current Iw maintains the low-level current value until a predetermined delay period has elapsed since the arc re-ignition, because the short-circuit arc current setting signal Icr remains the low-level current setting signal Ilr. Therefore, the transistor TR is in the off state only during the period from when the squeezing detection signal Nd changes to a high level until the welding current Iw decreases to a low-level current value. As shown in FIG. 1C, the welding voltage Vw decreases once as the welding current Iw decreases, and then rises sharply. The above-mentioned parameters are set to the following values, for example: initial current = 40 A, initial period = 0.5 ms, short circuit slope = 180 A/ms, short circuit peak value = 400 A, low-level current value = 50 A, delay period = 0.5 ms.

[Operation during arc period from time t6 to t9]
At time t6, when the constriction progresses due to the pinching force caused by the reverse feed of the welding wire and the flow of the welding current Iw and an arc is generated, as shown in Fig. 1C, the welding voltage Vw increases sharply to an arc voltage value of several tens of volts, and the short circuit determination signal Sd changes to a low level (arc period) as shown in Fig. 1D. In response to this, the system transitions to a predetermined reverse feed deceleration period Trd from time t6 to t7, and the feed speed Fw decelerates from the reverse feed peak value Wrp to 0 as shown in Fig. 1A.

When the reverse feed deceleration period Trd ends at time t7, a predetermined forward feed acceleration period Tsu begins from time t7 to t8. During this forward feed acceleration period Tsu, as shown in FIG. 1A, the feed speed Fw accelerates from 0 to the forward feed peak value Wsp. During this period, the arc period continues. For example, the forward feed acceleration period Tsu is set to 1 ms.

When the forward acceleration period Tsu ends at time t8, as shown in FIG. 1A, the feed speed Fw enters the forward peak period Tsp and becomes the forward peak value Wsp described above. The arc period continues during this period. The forward peak period Tsp continues until a short circuit occurs at time t9. Therefore, the period from time t6 to t9 is the arc period. When a short circuit occurs, the operation returns to that at time t3. The forward peak period Tsp is not a predetermined value, but is about 4 ms. For example, the forward peak value Wsp is set to 70 m/min.

When an arc is generated at time t6, as shown in FIG. 1C, the welding voltage Vw increases rapidly to an arc voltage value of several tens of volts. On the other hand, as shown in FIG. 1B, the welding current Iw maintains a low-level current value during the delay period from time t6 to t61. After that, from time t61, the welding current Iw increases rapidly to a peak value, and then gradually decreases to a large current value. During this high-current arc period from time t61 to t81, feedback control of the welding power source is performed by the voltage error amplification signal Ev in FIG. 1, resulting in a constant voltage characteristic. Therefore, the value of the welding current Iw during the high-current arc period changes depending on the arc load.

At time t81, when the current drop time determined by the current drop time setting signal Tdr in FIG. 1 has elapsed since the arc was generated at time t6, the small current period signal Std changes to a high level, as shown in FIG. 1(E). In response to this, the welding power source is switched from a constant voltage characteristic to a constant current characteristic. As a result, as shown in FIG. 1(B), the welding current Iw drops to a low level current value and maintains that value until time t9 when a short circuit occurs. Similarly, as shown in FIG. 1(C), the welding voltage Vw also drops. When a short circuit occurs at time t9, the small current period signal Std returns to a low level.

The short circuit transfer arc welding period Tc includes multiple cycles of repeated short circuit periods and arc periods. One cycle of short circuit/arc is, for example, about 10 ms. In FIG. 2, the short circuit transfer arc welding period Tc is switched to at the start of a base period in which droplets are not transferred. Alternatively, the switching may occur during a period partway through the base period Tb.

Figure 3 is a timing chart of each signal when switching from the short circuit transfer arc welding period Tc to the pulse arc welding period Ta in the arc welding device of Figure 1. Figure (A) shows the change over time of the feed speed Fw, Figure (B) shows the change over time of the welding current Iw, Figure (C) shows the change over time of the welding voltage Vw, Figure (D) shows the change over time of the short circuit discrimination signal Sd, Figure (E) shows the change over time of the small current period signal Std, and Figure (F) shows the change over time of the timer signal Tm. The operation of each signal will be explained below with reference to the figure.

At time t1, as shown in FIG. 1B, the welding current Iw is at a low level current value because the short circuit is released and the arc is reignited. Then, at time t1, the timer signal Tm shown in FIG. 1F changes to a low level (short circuit transition arc welding period Tc) and the time determined by the short circuit transition arc welding period setting signal Tcr in FIG. 1 has elapsed, and the short circuit determination signal Sd first changes to a low level (arc period). Therefore, at time t1, the short circuit transition arc welding period Tc is switched to the pulse arc welding period Ta. In FIG. 1B, during the period before time t1, the feed speed Fw is at the reverse feed peak value Wrp as shown in FIG. 1A. As shown in FIG. 1C, the welding voltage Vw is at the short circuit voltage value. As shown in FIG. 1D, the short circuit determination signal Sd changes from a high level (short circuit period) to a low level (arc period) at time t1. As shown in FIG. 1E, the small current period signal Std remains at a low level.

At time t1, as shown in FIG. 1(F), the timer signal Tm changes to a high level, and the pulse arc welding period Ta begins. In response to this, as shown in FIG. 1(A), the feed speed Fw enters the pulse initial reverse feed period Tair, which is determined by the pulse initial reverse feed period setting signal Tarr in FIG. 1. The feed speed Fw during the pulse initial reverse feed period Tair from time t1 to t2 becomes the pulse initial reverse feed speed Fa, which is determined by the pulse initial reverse feed speed setting signal Farr in FIG. 1. At time t2, when the pulse initial reverse feed period Tair ends, as shown in FIG. 1(A), the feed speed Fw becomes the pulse forward feed speed Fas, which is determined by the pulse forward feed speed setting signal Fasr in FIG. 1, and forward feed is performed at a constant feed speed.

At the same time, when the pulse arc welding period Ta is entered at time t1, as shown in FIG. 1B, the welding current Iw enters the pulse initial current period Tas determined by the pulse initial current period setting signal Tasr in FIG. 1. The welding current Iw during this pulse initial current period Tas from time t1 to t3 becomes the pulse initial current Ias determined by the pulse initial current setting signal Iasr in FIG. 1.

After time t3, the steady period begins. As shown in FIG. 1B, during the predetermined steady peak rise period Tu from time t3 to t4, a transition current that rises to the peak current value Ip determined by the peak current setting signal Ipr in FIG. 1 flows. During the predetermined steady peak period Tp from time t4 to t5, the above peak current value Ip flows. During the predetermined steady peak fall period Tpd from time t5 to t6, a transition current that falls from the above peak current value Ip to the base current value Ib determined by the base current setting signal Ibr in FIG. 1 flows. During the predetermined base period Tb from time t6 to t7, the above base current value Ib flows. During the pulse arc welding period Ta, the welding power source has a constant current characteristic. For this reason, the welding current Iw is set by the pulse current setting signal Iar in FIG. 1. As shown in FIG. 1C, the welding voltage Vw has a waveform similar to the current waveform. The period from time t3 to t7 is one pulse period Tf. In order to maintain the arc length at an appropriate value, the peak current Ip and base current Ib are modulated so that the average value of the welding voltage Vw is equal to the target value (current modulation control). Other modulation control methods include frequency modulation control, which modulates the pulse period Tf, and peak period modulation control, which modulates the peak period Tp. In any modulation control, a good welding condition can be achieved by achieving a state in which one droplet is transferred during one pulse period Tf, that is, one droplet is transferred per pulse period. Example values of each parameter are Tu = 1.5 ns, Tp = 0.2 ms, Tpd = 1.5 ms, Tb = 7 ms, Ip = 350-450 A, and Ib = 30-80 A.

The pulse arc welding period Ta includes multiple pulse periods Tf. The pulse period Tf is, for example, about 10 ms.

At time t1, when the pulse arc welding period Ta starts, the arc length is very short because it is immediately after the short circuit is released. The pulse initial reverse feed period Tair from time t1 is set so that the arc length is increased to the desired value. By passing the first peak current Ip from time t3 after the arc length is increased to the desired value, the droplet formation state can be stabilized from the first cycle. This allows for smooth switching from the short circuit transfer arc welding period Tc to the pulse arc welding period Ta. Therefore, the pulse initial reverse feed period Tair and the pulse initial reverse feed speed Fa are set to values that increase the arc length to the desired value. For this purpose, the pulse initial reverse feed period Tair is set to a period at least longer than the reverse feed deceleration period Trd in FIG. 2. In addition, the pulse initial reverse feed speed Fa is a value smaller than the reverse feed peak value Wrp in FIG. 2. For example, Tar = 3 ms, Fa = -6 m/min.

Furthermore, the pulse initial reverse feed period Tair is set to the period during which the welding voltage Vw rises to the reference voltage value. The welding voltage Vw is proportional to the arc length. Therefore, by setting the reference voltage value to a value corresponding to the desired arc length, the pulse initial reverse feed period Tair can be automatically set, making parameter setting easier.

Furthermore, during the initial pulse reverse feed period Tair, the welding current Iw is maintained at the initial pulse current Ias, which is greater than the base current Ib and smaller than the peak current Ip. The initial pulse current Ias is supplied during a predetermined initial pulse current period Tas. It is set so that Tar < Tas. By setting the initial pulse current Ias to a value greater than the base current Ib, it is possible to promote melting of the welding wire and prevent re-short circuiting between the welding wire and the base material during a period when the arc length is short. This makes it possible to reduce spatter when switching to the pulse arc welding period Ta, making the switching even smoother. By setting the initial pulse current Ias to a value smaller than the peak current Ip, it is possible to prevent the arc length from burning up too quickly and becoming too long than the desired value. For example, Tas = 5 ms, Ias = 100 A.

Furthermore, the first peak current Ip is applied after the initial pulse reverse feed period Tair has elapsed. In other words, this means setting it so that Tar < Tas. By starting the first pulse cycle after the initial pulse reverse feed period Tair has ended, it is possible to reliably stabilize the droplet transfer state in the first pulse cycle.

The effects of this embodiment will be described below.
(1) When welding is started, as described above in Figures 2 and 3, welding is performed with the pulse arc welding period Ta and the short circuit transfer arc welding period Tc forming one cycle. The time lengths of both periods Ta and Tc are set by calculating the pulse arc welding period setting signal Tar and the short circuit transfer arc welding period setting signal Tcr from the cycle setting value of the cycle setting signal Tacr and the time ratio setting value of the time ratio setting signal Dtr in Figure 1. The setting range of the cycle setting signal Tacr in Figure 1 is about 0.1 to 1 second, and the setting range of the time ratio setting signal Dtr in Figure 1 is about 30 to 70%. Therefore, the pulse arc welding period Ta and the short circuit transfer arc welding period Tc are about 30 to 700 ms.

(2) When the welding progresses and the temperature of the base metal rises, the weld pool becomes concave and the distance between the power feed tip and the base metal becomes longer, and as a result, the average value of the welding voltage (average voltage detection signal Vad) rises from the normal value to the reference voltage value Vt or higher. When this state occurs, the voltage rise determination signal Hd in FIG. 1 changes to a high level. In response to this, the value of the cycle setting signal Tacr switches from the cycle setting value in (1) to the corrected cycle setting value, and the value of the time ratio setting signal Dtr switches from the time ratio setting value in (1) to the corrected time ratio setting value. Here, the cycle setting value > the corrected cycle setting value and the time ratio setting value < the corrected time ratio setting value, so the cycle becomes shorter and the time ratio of the short circuit transfer arc welding period Tc becomes larger. As a result, the arc becomes more concentrated and the heat input to the base metal becomes smaller, so that the unstable generation of the bead's cycle and the occurrence of burn-through can be suppressed, and good welding quality can be obtained. These cycle and time ratio corrections are performed automatically, so there is no need to set the welding conditions in detail as the welding progresses. The reference voltage value Vt is set to a value that is about 2V higher than the average welding voltage during normal welding in (1). The corrected cycle setting value is set to about 0.3 to 0.7 times the cycle setting value, and the corrected time ratio setting value is set to a value obtained by adding 10 to 20% to the time ratio setting value. For example, the cycle setting value is set to 200 ms, the corrected cycle setting value is set to 100 ms, the time ratio setting value is set to 50%, and the corrected time ratio setting value is set to 60%.

If the average value for each cycle of the pulse arc welding period and the short circuit transfer arc welding period is used as the average value of the above welding voltage, it is possible to quickly and accurately detect that the molten pool has become concave and the distance between the power feed tip and the base metal has become longer. This makes it possible to more reliably suppress the unstable occurrence of back waves in the bead and the occurrence of burn-through. Furthermore, if the average value during the pulse arc welding period is used as the average value of the above welding voltage, it is possible to even more quickly and accurately detect that the molten pool has become concave and the distance between the power feed tip and the base metal has become longer. This is because the heat input during the pulse arc welding period is greater than the heat input during the short circuit transfer arc welding period, so the molten pool becomes more concave and the distance between the power feed tip and the base metal also becomes longer, improving detection accuracy.

In the above, we have described a case where both the period and the time ratio are corrected when the average welding voltage value becomes equal to or exceeds the reference voltage value, but it is also possible to correct only one of them.

1 Welding wire
2. Base material
3. Arc
4. Welding torch
5 Feed roll CM Current comparison circuit Cm Current comparison signal DR Drive circuit Dr Drive signal DTR Time ratio setting circuit Dtr Time ratio setting signal E Output voltage Ea Error amplification signal ED Output voltage detection circuit Ed Output voltage detection signal EI Current error amplification circuit Ei Current error amplification signal ER Output voltage setting circuit Er Output voltage setting signal EV Voltage error amplification circuit Ev Voltage error amplification signal Fa Pulse initial reverse feed speed FAR Pulse feed speed setting circuit Far Pulse feed speed setting signal FARR Pulse initial reverse feed speed setting signal Farr Pulse initial reverse feed speed setting signal FASR Pulse forward feed speed setting circuit Fasr Pulse forward feed speed setting signal FC Feed control circuit Fc Feed control signal FCR Short circuit arc feed speed setting circuit Fcr Short circuit arc feed speed setting signal FR Feed speed setting circuit Fr Feed speed setting signal Fw Feed speed HD Voltage rise determination circuit Hd Voltage rise determination signal IAR Pulse current setting circuit Iar Pulse current setting signal Ias Pulse initial current IASR Pulse initial current setting circuit Iasr Pulse initial current setting signal Ib Base current IBR Base current setting circuit Ibr Base current setting signal ICR Short circuit arc current setting circuit Icr Short circuit arc current setting signal ID Current detection circuit Id Current detection signal ILR Low level current setting circuit Ilr Low level current setting signal Ip Peak current IPR Peak current setting circuit Ipr Peak current setting signal IR Current setting circuit Ir Current setting signal Iw Welding current ND Constriction detection circuit Nd Constriction detection signal PM Power supply main circuit R Current reducing resistor SD Short circuit determination circuit
Sd Short circuit determination signal STD Small current period circuit Std Small current period signal Stf Final pulse period signal SW Power supply characteristics switching circuit Ta Pulse arc welding period TACR Period setting circuit Tacr Period setting signal Tair Initial pulse reverse feed period TAR Pulse arc welding period setting circuit Tar Pulse arc welding period setting signal TARR Initial pulse reverse feed period setting circuit Tarr Initial pulse reverse feed period setting signal Tas Initial pulse current period TASR Initial pulse current period setting circuit Tasr Initial pulse current period setting signal Tb Base period TBR Base period setting circuit Tbr Base period setting signal Tc Short circuit transition arc welding period TCR Short circuit transition arc welding period setting circuit Tcr Short circuit transition arc welding period setting signal TDR Current fall time setting circuit Tdr Current fall time setting signal Tf Pulse period TM Timer circuit Tm Timer signal Tp Peak period TPR Peak period setting circuit Tpr Peak period setting signal Tpd Peak fall period TPDR Peak falling period setting circuit Tpdr Peak falling period setting signal TR Transistor Trd Reverse feed deceleration period TRDR Reverse feed deceleration period setting circuit Trdr Reverse feed deceleration period setting signal Trp Reverse feed peak period Tru Reverse feed acceleration period TRUR Reverse feed acceleration period setting circuit Trur Reverse feed acceleration period setting signal Tsd Forward feed deceleration period TSDR Forward feed deceleration period setting circuit Tsdr Forward feed deceleration period setting signal Tsf Final pulse period Tsp Forward feed peak period Tsu Forward feed acceleration period TSUR Forward feed acceleration period setting circuit Tsur Forward feed acceleration period setting signal Tu Peak rise period TUR Peak rise period setting circuit Tur Peak rise period setting signal VAD Average voltage detection circuit Vad Average voltage detection signal VD Voltage detection circuit Vd Voltage detection signal Vw Welding voltage WL Reactor WM Feed motor Wrp Reverse feed peak value WRR Reverse feed peak value setting circuit Wrr Reverse transmission peak value setting signal Wsp Forward transmission peak value WSR Forward transmission peak value setting circuit Wsr Forward transmission peak value setting signal

Claims (3)

In an arc welding apparatus which performs welding with a pulse arc welding period and a short circuit transfer arc welding period as one cycle,
The arc welding apparatus corrects and controls the time ratio of the period and/or the short circuit transfer arc welding period based on an average value of the welding voltage.
The correction control is a control to shorten the period and/or a control to increase the time ratio when the average value of the welding voltage becomes equal to or greater than a reference voltage value.
1. An arc welding device comprising: The average value of the welding voltage is an average value for each cycle of the pulse arc welding period and the short circuit transfer arc welding period.
2. The arc welding apparatus according to claim 1 . The average value of the welding voltage is an average value during the pulse arc welding period.
2. The arc welding apparatus according to claim 1 .

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