阅读说明：本技术 电弧焊接方法 (Arc welding method ) 是由 高田贤人 惠良哲生 广田周吾 中俣利昭 于 2019-10-25 设计创作，主要内容包括：本发明提供电弧焊接方法,交替切换正向进给的脉冲电弧焊接和正反向进给的短路过渡电弧焊接来进行焊接,平顺地进行焊接方法的切换。在交替切换将焊丝正向进给来进行脉冲电弧焊接的期间和将焊丝正反向进给来进行短路过渡电弧焊接的期间从而进行焊接的电弧焊接方法中,在脉冲电弧焊接的时刻(t1)所表示的峰值期间中,将进给速度(Fw)加速到正向进给峰值(Wsp)并切换到短路过渡电弧焊接的期间(Tc)。(The invention provides an arc welding method, which alternately switches pulse arc welding of forward feeding and short-circuit transition arc welding of forward and reverse feeding to weld, and smoothly switches the welding method. In an arc welding method for alternately switching a period for performing pulse arc welding by feeding a wire forward and a period for performing short-circuit transition arc welding by feeding the wire forward and backward, a feeding speed (Fw) is accelerated to a forward feeding peak value (Wsp) and the period is switched to a short-circuit transition arc welding period (Tc) in a peak period indicated by a time point (t1) of the pulse arc welding.)

1. An arc welding method for performing welding by alternately switching a period for performing pulse arc welding by feeding a welding wire in a forward direction and a period for performing short-circuit transition arc welding by feeding the welding wire in the forward direction and the reverse direction,

and switching to the short-circuit transition arc welding during a peak period of the pulse arc welding.

2. The arc welding method according to claim 1,

and accelerating the feeding speed to a forward feeding peak value and switching to the short-circuit transition arc welding in the peak period of the pulse arc welding.

3. The arc welding method according to claim 2,

the forward feed peak value of the first cycle in the short-circuit transition arc welding is set to a value different from the forward feed peak value of the next cycle transition.

4. An arc welding method according to any one of claims 1 to 3,

switching to the pulse arc welding during an arc period of the short-circuit transition arc welding.

5. An arc welding method according to any one of claims 1 to 3,

the short-circuit transition arc welding is switched to the pulse arc welding in a state of low current value.

Technical Field

The present invention relates to an arc welding method for performing welding by alternately switching a period for performing pulse arc welding and a period for performing short-circuit transition arc welding.

Background

A method of welding by alternately switching a period of performing pulse arc welding and a period of performing short-circuit transition arc welding by feeding a wire (for example, refer to patent document 1). The switching frequency in this case is about 0.1 to 10 Hz. In this welding method, a scaly and beautiful bead can be formed. Further, in this welding method, the heat input to the base material can be controlled by adjusting the ratio of the pulse arc welding period to the short-circuit transition arc welding period.

Further, the invention of patent document 2 discloses an arc welding method in which a period in which a 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 transition arc welding are alternately switched to perform welding. In the arc welding method, the feed in the short-circuit transition arc welding is made to be a forward feed in the arc period and a reverse feed in the short-circuit period. Further, switching from pulse arc welding to short-circuit transition arc welding is performed during the base period of pulse arc welding.

Disclosure of Invention

Therefore, an object of the present invention is to provide an arc welding method capable of smoothly switching between pulse arc welding and short-circuit transition arc welding.

In order to solve the above-described problems, the invention according to claim 1 is an arc welding method for performing welding by alternately switching a period during which a welding wire is fed forward to perform pulse arc welding and a period during which the welding wire is fed forward to perform short-circuit transition arc welding, wherein the arc welding method is characterized by switching to the short-circuit transition arc welding in a peak period of the pulse arc welding.

The invention according to claim 2 is the arc welding method according to claim 1, wherein the arc welding method is characterized in that the arc welding method is switched to the short-circuit transition arc welding by accelerating the feed rate to a forward feed peak value in a peak period of the pulse arc welding.

The invention of claim 3 is the arc welding method according to claim 2, wherein the forward feed peak value of the first cycle in the short-circuit transition arc welding is set to a value different from the forward feed peak value of the next cycle transition.

The invention of claim 4 is the arc welding method according to any one of claims 1 to 3, wherein the arc period in the short-circuit transition arc welding is switched to the pulse arc welding.

The invention according to claim 5 is the arc welding method according to any one of claims 1 to 3, wherein the arc is regenerated in the short-circuit transition arc welding, and the arc is switched to the pulse arc welding in a state of a low level current value.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, switching between pulse arc welding and short-circuit transition arc welding can be performed smoothly.

Drawings

Fig. 1 is a block diagram of a welding power source for carrying out an arc welding method according to embodiment 1 of the present invention.

Fig. 2 is a timing chart of signals at the time of switching from the pulse arc welding period Ta to the short-circuit transition arc welding period Tc in the welding power source of fig. 1 illustrating the arc welding method according to embodiment 1 of the present invention.

Fig. 3 is a timing chart showing signals at the time of switching from the short-circuit transition arc welding period Tc to the pulse arc welding period Ta in the welding power source of fig. 1 of the arc welding method according to embodiment 1 of the present invention.

Description of reference numerals

1 welding wire

2 base material

3 arc of electricity

4 welding spray gun

5 feed roller

CM current comparison circuit

Cm current comparison signal

DR drive circuit

Dr drive signal

E output voltage

Ea error amplified signal

ED output voltage detection circuit

Ed output voltage detection signal

EI current error amplifying circuit

Ei current error amplified signal

ER output voltage setting circuit

Er output voltage setting signal

EV voltage error amplifying circuit

Ev voltage error amplified signal

FAR pulse feed speed setting circuit

Far pulse feed rate 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 rate setting signal

Fw feed rate

IAR pulse current setting circuit

Iar pulse current setting signal

Current of base Ib

IBR basic value 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 necking down detection circuitry

Nd neck detection signal

PM power main circuit

R current reducing resistor

SD short circuit discrimination circuit

Sd short circuit discrimination signal

Circuit in small current period of STD

Signal during Std small current

SW power supply characteristic switching circuit

Ta pulse arc welding period

TAR pulse arc welding period setting circuit

Tar pulse arc welding period setting signal

During the Tb base value

Tc short transition arc welding period

TCR short circuit transition arc welding period setting circuit

Tcr short circuit transition arc welding period setting signal

Td peak falling period

TDR current fall time setting circuit

Tdr current falling time setting signal

TF pulse period circuit

Tf pulse period (Signal)

TM timer circuit

Tm timer signal

Tp peak period

TR transistor

During Trd reverse feed deceleration

TRDR reverse feeding deceleration period setting circuit

Trdr reverse feeding deceleration period setting signal

During the reverse peak feed period of Trp

During acceleration of Tru reverse feed

TRUR reverse feed acceleration period setting circuit

Trur reverse feed acceleration period setting signal

During forward feed deceleration of Tsd

TSDR forward feed deceleration period setting circuit

Tddr Forward feed deceleration period setting Signal

During Tsp positive feed peak

During acceleration of Tsu forward feed

TSUR forward feed acceleration period setting circuit

Tsur Forward feed acceleration period setting Signal

Tu peak rise period

VD voltage detection circuit

Vd voltage detection signal

Vw welding voltage

WL reactor

WM feed motor

Peak reverse feed of Wrp

WRR reverse feeding peak value setting circuit

Wrr reverse feed peak setting signal

Peak Wsp forward feed

WSR forward feeding peak value setting circuit

Wsr positive feed peak setting signal

Detailed Description

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

[ embodiment 1]

Fig. 1 is a block diagram of a welding power source for carrying out an arc welding method according to embodiment 1 of the present invention. Each block is described below with reference to the figure.

The power main circuit PM receives a 3-phase 200V commercial power supply (not shown) as an input, performs output control by inverter control or the like in accordance with an error amplification signal Ea to be described later, and outputs an output voltage E. Although not shown, the power supply main circuit PM includes: a 1-time rectifier for rectifying a commercial power supply; a smoothing capacitor for smoothing the rectified direct current; an inverter circuit for converting the smoothed direct current into a high-frequency alternating current and driven by the error amplification signal Ea; the high-frequency transformer is used for reducing the high-frequency alternating current to a voltage value suitable for welding; and 2-time rectifier for rectifying the high-frequency alternating current with voltage reduction into direct current.

The reactor WL smoothes the welding current Iw to continue the stable arc 3.

The feed motor WM feeds a wire 1 at a feed speed Fw by feeding the wire in a forward direction during a pulse arc welding period and in a forward and reverse direction during a short-circuit transient arc welding period, using a feed control signal Fc described later as an input. A motor having a high transient response is used for the feed motor WM. In order to increase the rate of change of the feeding speed Fw of the welding wire 1 and the reversal of the feeding direction, the feeding motor WM may be provided near the tip of the welding torch 4. In addition, there is also a case where a push-pull type feed system is made using 2 feed motors WM.

Welding wire 1 is fed into welding torch 4 by rotation of feed roller 5 coupled to feed motor WM described above, and arc 3 is generated between welding wire and base material 2. A welding voltage Vw is applied between a contact tip (not shown) in the welding torch 4 and the base material 2, and a welding current Iw is applied. A protective gas (not shown) is ejected from the tip of welding torch 4 to shield arc 3 from the atmosphere. As the shielding gas, a mixed gas of argon gas and carbon dioxide gas is used when the material of the welding wire 1 is steel, and argon gas is used when the material of the welding wire 1 is aluminum.

The output voltage setting circuit ER outputs a predetermined output voltage setting signal ER. The output voltage detection circuit ED detects the output voltage E, 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 input signals, amplifies an error between the output voltage setting signal Er (+) and the output voltage detection signal Ed (-) and outputs a 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 as an input, and outputs a short circuit determination signal SD that is determined to be in the short circuit period and set to the high level when the value of the voltage detection signal Vd is less than a predetermined short circuit determination value (about 10V), and is determined to be in the arc period and set to the low level when the value is greater than the predetermined short circuit determination value.

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

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

The reverse feed acceleration period setting circuit TRUR outputs a predetermined reverse feed 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 feeding peak value setting circuit WSR receives a timer signal Tm described later and the short-circuit determination signal Sd as inputs, and outputs a forward feeding peak value setting signal Wsr which has a predetermined initial value during a period from when the timer signal Tm changes to a low level (short-circuit transient arc welding period Tc) until when the first short-circuit determination signal Sd changes to a high level (short-circuit period), and which has a predetermined steady-state value during other periods.

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

The short-circuit arc feed speed setting circuit FCR receives as input 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 discrimination signal Sd, and outputs a feed speed pattern generated by the following processing as a short-circuit arc feed speed setting signal FCR. The short-circuit arc feed speed setting signal Fcr is a positive value, and is a negative value, and is a positive feed period.

1) In the forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur, a short-circuit arc feed speed setting signal Fcr linearly accelerated from 0 (where the pulse feed speed setting signal Far is immediately after switching to the short-circuit transient arc welding period Tc) to a forward feed peak Wsp of a positive value determined by the forward feed peak setting signal Wsr is output.

2) Next, in the forward feed peak period Tsp, the short-circuit arc feed speed setting signal Fcr is output to maintain the above-described forward feed peak Wsp.

3) When the short-circuit determination signal Sd changes from a low level (arc period) to a high level (short-circuit period), the short-circuit determination signal Sd transits to the forward feed deceleration period Tsd specified by the forward feed deceleration period setting signal Tsdr, and the short-circuit arc feed speed setting signal Fcr linearly decelerated from the forward feed peak Wsp to 0 is output.

4) Next, in the backward feed acceleration period Tru determined by the backward feed acceleration period setting signal Trur, the short-circuit arc feed speed setting signal Fcr is output which linearly accelerates from 0 to the backward feed peak value Wrp determined by the backward feed peak value setting signal Wrr.

5) Next, in the reverse feeding peak period Trp, the short-circuit arc feeding speed setting signal Fcr for maintaining the reverse feeding 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 short-circuit determination signal Sd transits to the reverse feed deceleration period Trd specified by the reverse feed deceleration period setting signal Trdr, and outputs the short-circuit arc feed speed setting signal Fcr linearly decelerated from the reverse feed peak value Wrp to 0.

7) The above-described 1) to 6) are repeated to generate the short-circuit arc feed speed setting signal Fcr of the feed pattern in which the positive and negative trapezoidal wave changes.

The current reducing resistor R is interposed between the above-described reactor WL and the welding torch 4. The value of the current reducing resistor R is set to a large value (on the order of 0.5 to 3 Ω) which is 50 times or more the resistance value (on the order of 0.01 to 0.03 Ω) of the current path of the welding current Iw during the short circuit period. When the current reducing resistor R is inserted into a current path for receiving the current Iw, energy stored in the reactor WL and the reactor of the weld cable is rapidly consumed.

The transistor TR is connected in parallel with the above-described current reducing resistor R, and is turned on or off in accordance with a drive signal Dr described later.

The neck detection circuit ND receives the short circuit determination signal Sd, the voltage detection signal Vd, and the current detection signal Id as input, and outputs a neck detection signal ND that determines that the state of formation of the neck is in the reference state and becomes high level at a time point when the voltage rise value of the voltage detection signal Vd when the short circuit determination signal Sd is at high level (short circuit period) reaches a reference value, and that determines that the state of formation of the neck is low level at a time point when the short circuit determination signal Sd changes to low level (arc period). Further, the neck detection signal Nd may be changed to the high level at a point in time when the differential value of the voltage detection signal Vd during the short-circuit period reaches a reference value corresponding thereto. Further, the resistance value of the droplet may be calculated by dividing the value of the voltage detection signal Vd by the value of the current detection signal Id, and the neck detection signal Nd may be changed to the high level at a time point when the differential value of the resistance value reaches a reference value corresponding thereto.

The low level current setting circuit ILR outputs a predetermined low level current setting signal ILR. The current comparison circuit CM receives the low-level current setting signal Ilr and the current detection signal Id as input, and outputs a current comparison signal CM which becomes high when Id < Ilr and becomes low when Id ≧ Ilr.

The drive circuit DR receives the current comparison signal Cm and the neck detection signal Nd as input, and outputs a drive signal DR to the base terminal of the transistor TR, the drive signal DR changing to a low level when the neck detection signal Nd changes to a high level, and then changing to a high level when the current comparison signal Cm changes to a high level. Therefore, when the constriction is detected as the drive signal Dr, the drive signal Dr becomes low level, the transistor TR is turned off, and the current reducing resistor R is inserted into the conduction circuit, so that the welding current Iw rapidly decreases. When the value of welding current Iw that has decreased sharply decreases to the value of low-level current setting signal Ilr, drive signal Dr becomes high, and transistor TR is turned on, so that 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 necking detection signal Nd as inputs, 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), the short circuit arc current setting signal Icr which becomes the low level current setting signal Ilr is output.

2) When the short circuit determination signal Sd changes to a high level (short circuit period), the short circuit arc current setting signal Icr is output in a predetermined initial period, and thereafter, is ramped up to a predetermined short circuit peak value setting value at the time of a predetermined short circuit and is maintained at the same value.

3) Then, when the neck detection signal Nd changes to the high level, the short-circuit arc current setting signal Icr, which is the value of the low-level current setting signal Ilr, is output.

The current fall time setting circuit TDR outputs a predetermined current fall time setting signal TDR.

The small-current period circuit STD receives the short-circuit determination signal Sd and the current-fall-time setting signal Tdr as input, and outputs a small-current period signal STD which becomes high at a time point when a time determined by the current-fall-time setting signal Tdr elapses from a time point when the short-circuit determination signal Sd changes to low level (arc period), and then becomes low when the short-circuit determination signal Sd becomes high level (short-circuit period).

The pulse period circuit TF receives the voltage error amplification signal Ev as an input, voltage-frequency converts the voltage error amplification signal Ev, and outputs a pulse period signal TF which becomes a short-time high level for each pulse period. The repetition period of the peak period and the base period of the pulse arc welding is determined by the pulse period signal Tf.

The peak current setting circuit IPR outputs a predetermined peak current setting signal IPR. The base current setting circuit IBR outputs a predetermined base current setting signal IBR.

The pulse current setting circuit IAR receives the pulse period signal Tf, the peak current setting signal Ipr, and the base current setting signal Ibr as input, performs the following processing, and outputs a pulse current setting signal IAR.

1) When the pulse period signal Tf changes to a high level for a short time, a pulse current setting signal Iar rising from the base current setting signal Ibr to the peak current setting signal Ipr is output during a predetermined peak rising period Tu.

2) Next, in a predetermined peak period Tp, a pulse current setting signal Iar which becomes a peak current setting signal Ipr is output.

3) Next, in a predetermined peak fall period Td, a pulse current setting signal Iar that falls from the peak current setting signal Ipr to the base current setting signal Ibr is output.

4) Next, in the base period Tb until the pulse period signal Tf becomes a high level for a short time, the pulse current setting signal Iar which becomes the base current setting signal Ibr is output.

The pulse arc welding period setting circuit TAR outputs a predetermined pulse arc welding period setting signal TAR. The short-circuit transition arc welding period setting circuit TCR outputs a predetermined short-circuit transition arc welding period setting signal TCR.

The timer circuit TM receives the pulse arc welding period setting signal Tar, the short-circuit transient arc welding period setting signal Tcr, the short-circuit determination signal Sd, the pulse current setting signal Iar, and the peak current setting signal Ipr as input.

After a period determined by the short-circuit transient arc welding period setting signal Tcr elapses from a time point when the timer signal Tm changes to a low level (short-circuit transient arc welding period Tc), the short-circuit determination signal Sd initially changes to a low level (arc period), and the timer signal Tm changes to a high level at a time point when a predetermined delay period elapses.

After a period determined by the pulse arc welding period setting signal Tar has elapsed from the time point when the timer signal Tm changes to the high level (pulse arc welding period Ta), the timer signal Tm changes to the low level at the time point when the pulse current setting signal Iar first becomes equal to the value of the peak current setting signal Ipr.

Therefore, the pulse arc welding period Ta is a period from + the pulse arc welding period setting signal Tar to the first peak period. The short-circuit transition arc welding period Tc is a period from + the short-circuit transition arc welding period setting signal Tcr until the end of the first delay period.

The pulse feed rate setting circuit FAR outputs a predetermined positive pulse feed rate 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 input, and outputs the pulse feed speed setting signal Far as a 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 a 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 for feeding the welding wire 1 at a feed speed Fw corresponding to the value of the feed speed setting signal Fr to the feed motor WM.

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 input signals, 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 transition arc welding period Tc).

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

The power supply characteristic switching circuit SW receives the timer signal Tm, the current error amplification signal Ei, the voltage error amplification signal Ev, the short circuit determination signal Sd, and the small current period signal Std as input, performs the following processing, and outputs an error amplification signal Ea.

1) The current error amplification signal Ei is output as the error amplification signal Ea during a period from a time point when the timer signal Tm is at a low level and the short circuit determination signal Sd changes to a high level (short circuit period) to a time point when the short circuit determination signal Sd changes to a low level (arc period) and the delay period described above elapses.

2) In the subsequent large-current arc period, the voltage error amplification signal Ev is output as the error amplification signal Ea.

3) In the subsequent arc period, the current error amplification signal Ei is output as the error amplification signal Ea in the small-current arc period in which the small-current period signal Std becomes the high level.

4) When the timer signal Tm is at a high level, the current error amplification signal Ei is output as the error amplification signal Ea.

With this circuit, the characteristic of the welding power source in the short-circuit transient arc welding period Tc becomes a constant current characteristic in the short-circuit period, the delay period, and the small-current arc period, and becomes a constant voltage characteristic in the large-current arc period (the period from the time point when the delay time described above elapses after the short-circuit determination signal Sd changes from the high level to the low level to the time point when the small-current period signal Std changes from the low level to the high level in the period in which the timer signal Tm is at the low level). Further, the characteristic of the welding power source in the pulse arc welding period Ta becomes a constant current characteristic.

Fig. 2 is a timing chart of signals at the time of switching from the pulse arc welding period Ta to the short-circuit transition arc welding period Tc in the welding power source of fig. 1 illustrating the arc welding method according to embodiment 1 of the present invention. Fig. a shows a temporal change in the feed rate Fw, fig. B shows a temporal change in the welding current Iw, fig. C shows a temporal change in the welding voltage Vw, fig. D shows a temporal change in the short-circuit determination signal Sd, fig. E shows a temporal change in the small-current period signal Std, and fig. F shows a temporal change in the timer signal Tm. The operation of each signal will be described below with reference to the figure.

At time t0, as shown in the drawing (B), the welding current Iw increases from the base current and reaches the peak current value at time t 1. Then, at time t1, after a period determined by the pulse arc welding period setting signal Tar of fig. 1 has elapsed from the time point at which the timer signal Tm changes to the high level (pulse arc welding period Ta) shown in this diagram (F), the pulse current setting signal Iar of fig. 1 initially becomes equal to the peak current setting signal Ipr of fig. 1, and therefore, as shown in this diagram (F), the timer signal Tm changes from the high level to the low level. Therefore, at time t1, the pulse arc welding period Ta is switched to the short-circuit transition arc welding period Tc. In this figure, during a period before time t1, as shown in the figure (a), the feed rate Fw is fed forward at a constant rate determined by the pulse feed rate setting signal Far in fig. 1. As shown in fig. C, welding voltage Vw increases from the base voltage to the peak voltage. As shown in fig. D, the short circuit determination signal Sd remains at a low level as the arc period continues. As shown in fig. E, the low-current period signal Std is kept at a low level.

At time t1, as shown in the drawing (F), the timer signal Tm changes to a low level and enters the short-circuit transition arc welding period Tc. In response thereto, as shown in this graph (a), the feed speed Fw is accelerated toward the forward feed peak Wsp determined by the forward feed peak setting signal Wsr of fig. 1, and is maintained until a short circuit occurs at time t 3. The forward feed peak Wsp in this period is a predetermined initial value since the timer signal Tm changes to the low level until the first short circuit determination signal Sd changes to the high level (short circuit period). The forward feed peak Wsp thereafter becomes a predetermined steady-state value. The initial value and the steady-state value are set independently so that the welding state is stabilized during this period. The initial value may be set to a steady-state value.

During the period from time t1 to time t2, as shown in the graph (B), the welding power source has constant voltage characteristics, and therefore the welding current Iw changes according to the arc load. The welding current Iw gradually decreases from the time t 1. As shown in fig. C, welding voltage Vw also decreases.

At time t2, when the elapsed time from time t1 reaches the value of the current drop time setting signal Tdr in fig. 1, the low-current period signal Std changes to the high level as shown in this diagram (E). In response, the welding power supply switches from a constant voltage characteristic to a constant current characteristic. Therefore, as shown in fig. B, the welding current Iw is reduced to a low level current value and is maintained until time t3 when a short circuit occurs. Similarly, as shown in fig. C, welding voltage Vw also decreases. When a short circuit occurs at time t3, the low-current period signal Std returns to the low level.

The feed speed Fw shown in fig. (a) is controlled to the value of the short-circuit arc feed speed setting signal FCR output from the short-circuit arc feed speed setting circuit FCR of fig. 1. The feed speed Fw is formed by the following period: a forward feed acceleration period Tsu determined by the forward feed acceleration period setting signal Tsur of fig. 1; a forward feed peak period Tsp that continues until a short circuit occurs; a forward feed deceleration period Tsd determined by the forward feed deceleration period setting signal Tsdr of fig. 1; a reverse feed acceleration period Tru determined by the reverse feed acceleration period setting signal Trur of fig. 1; a reverse feeding peak period Trp which continues until an arc occurs; and a reverse feed deceleration period Trd determined by the reverse feed deceleration period setting signal Trdr of fig. 1. Further, the forward feed peak Wsp is determined by the forward feed peak setting signal Wsr of fig. 1, and the reverse feed peak Wrp is determined by the reverse feed peak setting signal Wrr of fig. 1. As a result, the short-circuit arc feed speed setting signal Fcr has a feed pattern in which positive and negative substantially trapezoidal waves change in a wave shape.

[ operation during short-circuit period from time t3 to t6 ]

When a short circuit occurs at time t3 in the forward feed peak period Tsp, the welding voltage Vw rapidly decreases to a short-circuit voltage value of several V as shown in the diagram (C), and therefore the short-circuit determination signal Sd changes to a high level (short-circuit period) as shown in the diagram (D). In response to this, the predetermined forward feed deceleration period Tsd from time t3 to t4 is transitioned to, and as shown in this drawing (a), the feed speed Fw is decelerated from the above-described forward feed peak Wsp to 0. For example, the forward feed deceleration period Tsd is set to 1 ms.

As shown in this diagram (a), the feed speed Fw enters a predetermined reverse feed acceleration period Tru from time t4 to time t5, and accelerates from 0 to the above-described reverse feed peak Wrp. The short circuit period continues during this period. For example, the reverse feed acceleration period Tru is set to 1 ms.

When the reverse feeding acceleration period Tru ends at time t5, the feeding speed Fw enters the reverse feeding peak period Trp as shown in fig. a, and becomes the reverse feeding peak Wrp described above. The reverse feed peak period Trp continues until an arc is generated at time t 6. Therefore, the period from time t3 to time t6 becomes a short-circuit period. The reverse feeding peak period Trp is not a given value and is of the order of 4 ms. For example, the reverse feed peak Wrp is set to-60 m/min.

As shown in fig. B, the welding current Iw in the short-circuit period from time t3 to time t6 reaches a predetermined initial current value in a predetermined initial period. Thereafter, the welding current Iw is ramped up at the predetermined short circuit time, and when the predetermined short circuit time peak is reached, the value is maintained.

As shown in fig. C, welding voltage Vw increases from the vicinity of the peak when welding current Iw is short-circuited. This is because the droplet at the leading end of the welding wire 1 gradually forms a neck due to the reverse feeding of the welding wire 1 and the pinch force caused by the welding current Iw.

When the voltage rise value of welding voltage Vw reaches the reference value, it is determined that the state of formation of the neck is in the reference state, and the neck detection signal Nd in fig. 1 changes to the high level.

In response to the neck detection signal Nd becoming high level, the drive signal Dr of fig. 1 becomes low level, and therefore the transistor TR of fig. 1 becomes off state, and the current reducing resistor R of fig. 1 is inserted in the conducting circuit. Meanwhile, the short-circuit arc current setting signal Icr of fig. 1 becomes small to the value of the low level current setting signal Ilr. Therefore, as shown in fig. B, the welding current Iw sharply decreases from the short-circuit peak value to a low-level current value. When welding current Iw decreases to a low level current value, driving signal Dr returns to a high level, and transistor TR is turned on, thereby short-circuiting current reducing resistor R. As shown in this diagram (B), since the short-circuit arc current setting signal Icr is in the state of holding the low-level current setting signal Ilr, the welding current Iw is maintained at the low-level current value until a predetermined delay period elapses after the arc is regenerated. Therefore, the transistor TR is turned off only during a period from a time point when the neck detection signal Nd changes to the high level to a time point when the welding current Iw decreases to a low level current value. As shown in fig. C, welding voltage Vw decreases once as welding current Iw decreases, and then rises rapidly. The above parameters are set to, for example, the following values. The initial current is 40A, the initial period is 0.5ms, the short circuit time slope is 180A/ms, the short circuit time peak value is 400A, the low-level current value is 50A, and the delay period is 0.5 ms.

[ operation during arc period from time t6 to t9 ]

At time t6, when the constriction progresses due to the pinching force generated by the backward feeding of the welding wire and the turning on of welding current Iw to generate an arc, welding voltage Vw rapidly increases to an arc voltage value of several tens V as shown in the diagram (C), and short circuit determination signal Sd changes to a low level (arc period) as shown in the diagram (D). In response to this, the predetermined reverse feed deceleration period Trd from the time t6 to t7 is transitioned to, and as shown in this diagram (a), the feed speed Fw is decelerated from the above-described reverse feed peak value Wrp to 0.

When the reverse feed deceleration period Trd ends at time t7, the transition is made to a predetermined forward feed acceleration period Tsu from time t7 to t 8. In the forward feed acceleration period Tsu, as shown in the drawing (a), the feed speed Fw is accelerated from 0 to the above-described forward feed peak Wsp. During which the arc period continues. For example, the forward feed acceleration period Tsu is set to 1 ms.

When the forward feed acceleration period Tsu ends at time t8, the feed speed Fw enters the forward feed peak period Tsp as shown in fig. a, and becomes the forward feed peak Wsp. During this period, the arc period also continues. The forward feed peak period Tsp continues until a short circuit occurs at time t 9. Therefore, the period from time t6 to time t9 is an arc period. When a short circuit occurs, the operation returns to the operation at time t 3. The forward feed peak period Tsp is not a given value, and is about 4 ms. For example, the forward feed peak Wsp is set to 70 m/min.

When an arc is generated at time t6, welding voltage Vw sharply increases to an arc voltage value of several tens V as shown in fig. C. On the other hand, as shown in fig. B, the welding current Iw continues at a low level current value for a delay period from time t6 to t 61. Then, from time t61, welding current Iw rapidly increases and reaches a peak value, and then gradually decreases to a large current value. In the large current arc period from time t61 to time t81, the feedback control of the welding power source is performed by the voltage error amplification signal Ev in fig. 1, and therefore, the constant voltage characteristic is obtained. Therefore, the value of the welding current Iw during the large-current arc varies depending on the arc load.

After the arc is generated at time t6, at time t81 when the current drop time determined by the current drop time setting signal Tdr in fig. 1 elapses, the small current period signal Std changes to the high level as shown in fig. E. In response, the welding power supply switches from a constant voltage characteristic to a constant current characteristic. As shown in fig. B, the welding current Iw is reduced to a low level current value and maintained until time t9 when a short circuit occurs. Similarly, as shown in fig. C, welding voltage Vw also decreases. When a short circuit occurs at time t9, the low-current period signal Std returns to the low level.

The short-circuit transition arc welding period Tc includes a plurality of repeated cycles of the short-circuit period and the arc period. The 1 cycle of the short circuit/arc is, for example, about 10 ms. The short-circuit transition arc welding period Tc is, for example, about 50 to 500 ms. In fig. 2, the start time of the peak period may be switched to the short-circuit arc welding period Tc. Alternatively, the switching may be performed during the peak period Tp, the peak rise period Tu, or the peak fall period Td.

Fig. 3 is a timing chart showing signals at the time of switching from the short-circuit transition arc welding period Tc to the pulse arc welding period Ta in the welding power source of fig. 1 of the arc welding method according to embodiment 1 of the present invention. Fig. a shows a temporal change in the feed rate Fw, fig. B shows a temporal change in the welding current Iw, fig. C shows a temporal change in the welding voltage Vw, fig. D shows a temporal change in the short-circuit determination signal Sd, fig. E shows a temporal change in the small-current period signal Std, and fig. F shows a temporal change in the timer signal Tm. The operation of each signal will be described below with reference to the figure.

At time t1, as shown in fig. B, welding current Iw is a low level current value because it is a delay period after the short circuit is released and the arc is re-generated. At time t1, since the short-circuit determination signal Sd is initially changed to the low level (arc period) and a predetermined delay period elapses after the period determined by the short-circuit transient arc welding period setting signal Tcr in fig. 1 elapses from the time point at which the timer signal Tm changes to the low level (short-circuit transient arc welding period Tc) shown in the drawing (F), the timer signal Tm changes from the low level to the high level as shown in the drawing (F). Therefore, at time t1, the short-circuit transition arc welding period Tc is switched to the pulse arc welding period Ta. In the figure, during the period before the time t1, as shown in the figure (a), the feed speed Fw is in the state of the reverse feed deceleration period Trd from the reverse feed peak Wrp to 0. As shown in this diagram (C), welding voltage Vw is an arc voltage value. As shown in fig. D, the short circuit determination signal Sd is at a low level during the delay period. As shown in fig. E, the low-current period signal Std is kept at a low level.

At time t1, as shown in the drawing (F), the timer signal Tm changes to a high level, and enters the pulse arc welding period Ta. In response to this, as shown in the graph (a), the feed speed Fw is fed forward at a fixed speed determined by the pulse feed speed setting signal Far of fig. 1.

As shown in this diagram (B), a transition current that rises to a predetermined peak current Ip is turned on during a predetermined peak rise period Tu from time t1 to t 2. The peak current Ip is turned on during a predetermined peak period Tp from time t2 to t 3. In a predetermined peak value falling period Td from time t3 to time t4, a transition current that falls from the peak current Ip to a predetermined base current Ib is turned on. In a base period Tb from time t4 to t5, the base current Ib is turned on. During the pulse arc welding period Ta, the welding power source becomes a constant current characteristic. For this purpose, the welding current Iw is set by the pulsed current setting signal Iar of fig. 1. As shown in fig. C, welding voltage Vw has a waveform similar to the current waveform. The pulse period Tf at times t1 to t5 is feedback-controlled so that the average value of the welding voltage Vw becomes a desired value. The current waveform parameters are set to let 1 droplet transit every 1 pulse period Tf. For example, the peak current Ip is 500A, the base current Ib is 60A, the peak rise period Tu is 1ms, the peak period Tp is 2ms, and the peak fall period Td is 1 ms.

The pulse arc welding period Ta includes a plurality of pulse periods Tf. The pulse period Tf is for example of the order of 15 ms. The pulse arc welding period Ta is, for example, about 50 to 500 ms. Fig. 3 shows a case where the delay period is switched to the pulse arc welding period Ta. Alternatively, the pulse arc welding period Ta may be started from the base period Tb. The period of the small current until the first peak current Ip is turned on may be advanced.

The operation and effect of the present embodiment will be described below. According to the present embodiment, as shown at time t1 in fig. 2, the pulse arc welding is switched to the short-circuit transition arc welding in the peak period. In this way, the arc period in which a large current value is turned on is switched to the short-circuit transition arc welding period. For this reason, a droplet is formed from the time of entering the short-circuit transition arc welding period until the initial short-circuit occurs at time t 3. As a result, the droplet smoothly transitions to the molten pool during the short-circuit period, and therefore, the switching from the pulse arc welding period to the short-circuit transition arc welding period is smoothly performed. If a short circuit occurs in a state where no droplet is formed, a non-molten portion of the welding wire enters a molten pool, and the welding form becomes unstable, causing large spatters. In the present embodiment, such a state can be suppressed.

Further, according to the present embodiment, in the peak period of the pulse arc welding, the feed speed is accelerated to the forward feed peak and the short-circuit transition arc welding is switched. In this way, since the high-speed forward feeding at the forward feeding peak is performed, it is possible to suppress the time until the first short circuit occurs from becoming excessively long. Therefore, it is possible to suppress the occurrence of spattering due to an excessively large droplet size at the time point when the first short circuit occurs.

Further, according to the present embodiment, the forward feed peak value of the first cycle in the short-circuit transition arc welding is set to a value different from the forward feed peak value of the next cycle transition. In this way, since the forward feed peak value until the first short circuit occurs is set to an appropriate value, the droplet size at the time point when the first short circuit occurs can be made appropriate, and the occurrence of spatters can be reduced.

Further, as shown at time t1 in fig. 3, according to the present embodiment, the arc period in the short-circuit transition arc welding is switched to the pulse arc welding. When the short-circuit period is switched to the pulse arc welding, the droplet transfer state becomes unstable, and therefore the welding form becomes unstable, and there is a possibility that large spatters are generated. If switching is performed during the arc period, the transition to pulsed arc welding is smooth.

Further, according to the present embodiment, the arc is regenerated in the short-circuit transition arc welding, and the arc is switched to the pulse arc welding in a state of a low level current value. In this way, since the pulse arc welding is switched to the state where no droplet is formed, the droplet transfer state of 1 pulse cycle 1 can be realized from the first pulse cycle. This can further stabilize the welding form.