JPH07155948A - Method for controlling arc start of pulse mag welding - Google Patents

Abstract

PURPOSE:To obviate the generation of spatters and to prevent the generation of lack of penetration by changing over a hot start current directly to welding pulse currents when the short circuit time is to larger than the set time. CONSTITUTION:A wire tip 1a is energized with the hot start current Ih of the current value larger than the average value of the weld pulse currents Iw and is then energized with the weld pulse currents Iw when the wire tip 1a comes into contact with objects 2 to be welded at the time of starting welding. The short circuit time for transfer to an arc 3 from short circuit is detected in such a case and the control to change over the pulse width of the transfer pulse currents It to be energized in the transfer period Tt since the end of the energization of the hot start current Ih before the start of the energization of the weld pulse currents Iw stepwise from the pulse width larger than the pulse width Tp of the weld pulse currents Iw to the pulse width Tp of the weld pulse currents Iw is executed when the short circuit time is within the set time. The hor start current Ih is directly changed over to the weld pulse currents Iw when the short circuit time is longer than the set time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse MAG welding arc start control method for promptly returning to an appropriate arc length when the upper part of a wire made of a material having a poor arc start property is blown. The present invention relates to a welding arc start control method.

[0002]

[Prior art]

[Prior Art 1] [Explanation of FIG. 1] FIG. 1 (A) is a diagram showing a time lapse t between a position of a wire tip 1a and an arc 3 generation state at the time of arc start of the prior art 1. FIG. 6B is a diagram showing the time lapse t of the welding current I at the time of arc start.

As shown in FIG. 1A, at time t1, the wire 1 is fed from inside the nozzle 5 at a slow down speed. At the time t2, when the wire tip 1a comes into contact with the workpiece 2, the hot start current Ih of several [ms] shown in FIG. Then, the object to be welded 2 is melted and heated to start welding. This hot start current I
h is a current having a current value equal to or higher than the current value of the welding pulse current Iw and having a pulse width larger than the pulse width Tp of the welding pulse current Iw. Time t3
At the time t4, the welding pulse current Iw having the pulse width Tp shown in FIG. 7B is passed after the hot start current Ih is turned off at the time t4.

In the case of the prior art 1, at the time t2, the wire tip 1a comes into contact with the object to be welded 2, and then at the time t3, the hot start current Ih is supplied to the wire tip 1a to be 3 to 8 [mm]. Fusing and scattering, and spatter 7a is generated as shown in FIG. In this case, when the fusing portion is large, the arc 3 cannot be continued and the arc is broken.

[Prior Art 2] [Explanation of FIG. 2] FIG. 2A is a diagram showing a time lapse t between the position of the wire tip 1a and the generation state of the arc 3 at the time of arc start of the prior art 2. FIG. 3B is a diagram showing the time course t of the welding current I at the time of arc start. At time t2 shown in FIG.
When a comes into contact with the object to be welded 2, the current rising speed is about 4,000 [A / ms] and the pulse current value and pulse width are larger than the welding pulse current Iw as shown in FIG. A small starting current Ig is supplied.

By supplying the starting current Ig, the starting arc 3a shown in FIG. 9A is generated, and subsequently the hot start current I shown in FIG.
Energize h. As a result, the heat input until the wire 1 is sufficiently heated is limited, and the excessive length of wire fusing does not occur. Then, by heating and melting only the vicinity where the wire tip 1a is in contact with the object to be welded 2, it is possible to prevent the wire tip 1a from melting and spattering to some extent.

However, when the hot start period Th shown in FIG. 1B is considerably larger than the pulse width Tp of the welding pulse current Iw, the wire 1 of the wire 1 is switched when the hot start current Ih is switched to the welding pulse current Iw. The heat input for melting is drastically reduced, and the temperature of the wire 1 and the object to be welded 2 cannot be sufficiently increased. As a result, at time t5 shown in FIG.
a contacts the object to be welded 2, and at time t6, spatter 7b is generated by the molten particles at the wire tip 1a.

[Prior Art 3] [Explanation of FIG. 3] FIGS. 3A to 3E show welding power supply output terminal voltage V (hereinafter referred to as welding voltage) V and welding current I at the time of arc start of the prior art 3. FIG. 6 is a diagram showing a time course t of the position of the wire tip 1a. At time t1 shown in FIG. 7A, the wire slow-down feeding is started,
A welding voltage V consisting of a base voltage and a pulse voltage is applied. At time t2, the wire tip 1a comes into contact with the object to be welded 2 as shown in FIG. 6D, and the hot start pulse current value Hp and the hot start base current value as shown in FIG. When the hot start current Ih composed of Hb is passed, the welding voltage becomes a short circuit voltage.

By applying the hot start current Ih, the wire tip 1a and the workpiece 2 are heated and melted. At time t3, arc 3 is generated, welding voltage V increases, and welding current I decreases. This welding voltage V
Is detected, the welding current I is decreased, or both are detected.
At, a welding voltage V composed of a pulse voltage and a base voltage during welding is supplied, and a welding pulse current Iw composed of a pulse current value Iwp and a base current value Iwb is supplied as shown in FIG. As a result, as in the case of the related art 2, at the time t3, it is possible to prevent the tip portion of the wire from melting and generating the spatter 7a.

However, as in the case of the prior art 2, when the hot start current Ih is switched to the welding pulse current Iw, the melting heat input of the wire 1 sharply decreases, so that the melting speed of the wire 1 decreases and The short circuit shown in FIG. Then, as shown in FIG.
Spatter 7b is generated by the molten particles of.

[Prior Art] [Explanation of FIG. 4] In order to prevent the above-mentioned spatter 7b from occurring, the present applicant has filed Japanese Patent Application No. 3-56138 before the present application.
In the following (hereinafter referred to as prior application), a starting method provided with the following means was proposed.

FIG. 4 (A) is a diagram showing the time elapse t between the position of the wire tip 1a and the generation state of the arc 3 at the time of arc start of the prior application, and FIG. 4 (B) is the arc start. It is a figure which shows the time elapsed t of the welding current I at the time.

In the arc start method of the prior art, as shown in FIG. 7B, a transition period Tt is provided and a transition pulse current It is supplied to prevent a sharp decrease in the welding current. . That is, the hot start period T
The pulse width (hereinafter, referred to as the first transition pulse width) Tp1 of the start pulse current (hereinafter, referred to as the first transition pulse current It1) at time t5 after h is made larger than the pulse width Tp of the welding pulse current Iw, The pulse width (hereinafter referred to as the second transition pulse width) Tp2 of the next pulse current (hereinafter referred to as the second transition pulse current It2) is switched to a value smaller than Tp1, and the next pulse current (hereinafter referred to as the third transition pulse current) The pulse width (hereinafter referred to as the third transition pulse width) Tp3 of It3) is switched to a value smaller than Tp2 to sequentially approach the pulse width Tp. Thus Tp1> Tp2
By setting> Tp3 ...> Tp, the hot start period Th is switched step by step to the pulse width Tp of the welding pulse current Iw, so that the heat input for melting the wire 1 gradually decreases, and the melting speed of the wire 1 changes. It is possible to prevent the generation of the spatter 7b shown in FIG.

[Explanation of FIG. 5 and FIG. 6] FIG. 5 is a block diagram of a pulse MAG welding apparatus for carrying out the arc start control method of the prior application, and FIG. 6 shows each part of the pulse MAG welding apparatus of FIG. It is a figure which shows the waveform of a signal.

In FIG. 5, the welding output control circuit PS is
Power supply tip 4 and work piece 2 with commercial power supply AC as input
Supply output between and. The arc 3 is the wire tip 1a
And the object 2 to be welded. The wire feeding motor WM rotates the wire feeding roller WR to feed the wire 1. The wire feed speed detector WD detects the rotation speed of the wire feed motor WM and outputs a wire feed speed detection signal Wd. The average current setting circuit IM outputs an average current setting signal Im for setting the average value of the welding current I determined by the wire feeding speed of the wire feeding motor WM. The first comparison circuit CM1 compares the wire feeding speed detection signal Wd with the average current setting signal Im and outputs a comparison signal Cm1. The wire feed control circuit WC receives the comparison signal Cm1 and inputs the wire feed control signal Wc to the wire feed motor WM.

The arc voltage detection circuit VD is a circuit for detecting an arc voltage and outputs an arc voltage detection signal Vd. The arc voltage setting circuit VS is a circuit for setting the arc voltage and outputs the arc voltage setting signal Vs.
The second comparison circuit CM2 inputs the arc voltage detection signal Vd and the arc voltage setting signal Vs, and outputs an arc voltage control signal Cm2 having the difference between them. The pulse frequency signal generation circuit VF outputs a pulse frequency signal Vf corresponding to the arc voltage control signal Cm2. The pulse width setting circuit TP is
The pulse width setting signal Tp is output. The pulse signal generation circuit DF includes a pulse frequency signal Vf and a pulse width setting signal Tp.
A pulse width frequency control signal Df obtained by combining and is output.

The short circuit determination circuit VI receives the arc voltage detection signal Vd as an input and outputs a short circuit determination signal Vi0. The short circuit inverting circuit NOT1 inverts the short circuit determination signal Vi0,
The short circuit inversion signal Vi1 is output. Welding current detection circuit ID
Detects the instantaneous value of the welding current I and outputs the welding current detection signal Id. The welding current conducting circuit IE receives the welding current detection signal Id as an input and outputs the welding current conducting signal Ie. The flip-flop circuit FF receives the welding current energization signal Ie as an input, outputs an FF output signal Ff, and stops the FF output signal Ff when the short circuit inversion signal Vi1 is input. The delay circuit TM receives the FF output signal Ff as an input,
When the delay signal Tm is output and the FF output signal Ff is stopped, the delay signal Tm is stopped after a preset delay time.

The transition pulse control circuit SR has a delay signal Tm.
When the delay signal Tm is stopped, a pulse width switching signal Tw for switching the pulse width of the transition pulse current It in stages is output. This transition pulse control circuit SR
Ends the transition period Tt when the built-in transition period time circuit ends, and starts passing the pulse width frequency control signal Df.

The pulse current value setting circuit IP outputs a pulse current value setting signal Ip. Base current setting circuit IB
Outputs the base current setting signal Ib. The pulse base current switching circuit SW4 uses the pulse width switching signal Tw to set the pulse current value setting signal Ip and the base current setting signal Ip.
The pulse control signal Pf is output by switching between b and b. The hot start current setting circuit IH outputs a start current Ig and a hot start current Ih. The start current switching circuit SW6 inputs the start current Ig and the hot start current Ih when the delay signal Tm is input, and inputs the pulse control signal Pf when the delay signal Tm is stopped. The current value setting signal S6 is output.
The third comparison circuit CM3 compares the current value setting signal S6 with the welding current detection signal Id and inputs the current value control signal Cm3 to the welding output control circuit PS.

In FIG. 6, (A) shows the waveform of the welding current I and the welding current detection signal Id output from the welding current detection circuit ID, and (B) shows the welding voltage V and arc voltage detection circuit. It is a figure which shows the waveform of the arc voltage detection signal Vd of the output of VD, (C) is a figure which shows the waveform of the welding current conduction signal Ie of the output of the welding current conduction circuit IE.
(D) is a short circuit determination signal Vi output from the short circuit determination circuit VI.
It is a figure which shows the waveform of 0, (E) is a figure which shows the waveform of FF output signal Ff of the output of flip-flop circuit FF, (F) is the waveform of the delay signal Tm of the output of delay circuit TM. FIG.

Transmission of signals with respect to time will be described with reference to FIG. When a welding start switch (not shown) is operated, the wire 1 comes into contact with the object 2 to be welded at time t1, and the welding current I is conducted to generate a welding current conduction signal as shown in FIG. Output Id. As the welding current I, first, a starting current Ig is passed, and subsequently, a hot start current I having a wider width than the welding pulse current Iw.
Energize h.

The welding current energization circuit IE receives the welding current detection signal Id as an input and outputs the welding current energization signal Ie shown in FIG. The flip-flop circuit FF receives the welding current energization signal Ie as an input, and the FF shown in FIG.
The output signal Ff is output. The delay circuit TM receives the FF output signal Ff as an input, outputs a delay signal Tm, and inputs it to the start current switching circuit SW6 and the transition pulse control circuit SR.

At time t1, as shown in FIG. 7B, when the welding voltage V and the arc voltage detection signal Vd decrease sharply, the short circuit determination circuit VI outputs the short circuit determination signal Vi0 shown in FIG. Output.

At time t2, as shown in FIG. 5, when the arc 3 is generated between the wire 1 and the object 2 to be welded, as shown in FIG. 6B, the welding voltage V and the arc voltage detection signal Vd are detected. Increases, and the short circuit determination signal Vi0 becomes L level as shown in FIG. Short circuit determination signal Vi0 is L
When it becomes the level, the short-circuit inversion signal Vi1 of the output of the short-circuit inversion circuit NOT1 shown in FIG. 5 becomes the H level and is input to the flip-flop circuit FF. Then, as shown in FIG. 6E, the FF output signal Ff becomes L level and is input to the delay circuit TM.

At time t3, when the delay signal Tm becomes L level, the start current switching circuit SW6 shown in FIG.
Is switched from the hot start current Ih to the pulse control signal Pf and is output as the current value setting signal S6.
At this time t3, the transition pulse control circuit SR starts its operation and, as shown in FIG. 6A, energizes the transition pulse current It after applying the hot start current Ih,
After that, the welding pulse current Iw is applied.

[0060]

[Problems to be Solved by the Invention]

[Explanation of FIGS. 7 and 8] FIG.
For example, like the aluminum silicon alloy A4043,
It is a figure which shows the time passage t of the position of the wire tip 1a at the time of an arc start, and the generation | occurrence | production state of the arc 3 when using the wire 1 of a component with which an arc start is extremely difficult. FIG. 3B is a diagram showing the time course t of the welding current I at the time of arc start. As shown in the figure, when the wire slows down at time t1 and the wire tip 1a contacts the workpiece 2 at time t2, the starting current of 4,000 [A / ms] rises at a high speed. A long-term short circuit occurs at times t3 and t4, despite the fact that Ig is energized.

At time t5 shown in FIG. 9A, when the arc start is generated after the tip of the wire is melted and the spatter 7a is generated, when the transition pulse current It shown in FIG. The large arc length Lb continues for a long time. The arc length Lb is lengthened by the fusing of the wire 1, but the arc length Lb is further lengthened because the hot start current Ih is applied. As a result, it takes 3 to 5 [seconds] to return to an appropriate arc length, and a penetration failure often occurs at the welding start portion. Particularly, in the horizontal fillet welding shown in FIG. 8, the web 21 and the flange 2 are
Since the arc is not concentrated in the corner portion formed by 2 and 2, defective fusion often occurs at the welding start portion 8a of the bead 8. The welding conditions are as follows. Aluminum silicon alloy A4 with a diameter of 1.6 [mm] as a wire
043, aluminum magnesium alloy A5083 having a plate thickness of 8 [mm], a welding current of 150 [A], a welding voltage of 19 [V] and a welding speed of 40 [cm / min], and argon gas. Horizontal fillet welding.

[0070]

A pulse MAG according to claim 1
The welding arc start control method is such that, when the wire tip 1a contacts the workpiece 2 at the start of welding, the welding pulse current Iw is applied after the hot start current Ih having a current value larger than the average value of the welding pulse current Iw is passed. In the pulse MAG welding arc start control method for energizing, the short-circuit time from the short-circuit to the arc 3 is detected, and when the short-circuit time is within the set time, the hot start current Ih
Of the welding pulse current Iw from the pulse width larger than the pulse width Tp of the welding pulse current Iw, the pulse width of the transition pulse current It to be energized during the transition period Tt from the end of the energization of the welding pulse current Iw to the start of the energization of the welding pulse current Iw. This is a pulse MAG welding arc start control method in which control is performed in steps up to the pulse width Tp, and when the short circuit time is longer than the set time, the hot start current Ih is directly switched to the welding pulse current Iw.

According to the pulse MAG welding arc start control method of the second aspect, when the wire tip 1a comes into contact with the workpiece 2 at the start of welding, the current rising speed is large and the pulse current value Ip and the pulse width Tp are welded. The starting current Ig smaller than the pulse current Iw is passed, and then the current I is supplied.
The pulse MAG welding arc start control method in which the hot start current Ih and the welding pulse current Iw described in (1) are applied.

[0080]

[Action]

[Explanation of FIG. 9] FIGS. 9 (A) and 9 (C) are views showing a time lapse t between the position of the wire tip 1a and the generation state of the arc 3 at the time of arc start of the present invention. (B) And (D) is a figure showing time passage t of welding current I at the time of arc start of the present invention.

FIGS. 9A and 9B show the case where the arc 3 is generated in a time shorter than the set time between the wire tip 1a and the workpiece 2 at the time of starting the arc. Similar to the description of 4, the generation of the spatter 7b shown in FIG. 3 (E) can be prevented.

FIGS. 9C and 9D show the case where the arc 3 is generated at a time when the short-circuiting time between the wire tip 1a and the workpiece 2 at the time of arc start is longer than the set time. At time t5, when the upper part of the wire tip 1a is melted and the arc length becomes large, the welding pulse current Iw is supplied without passing through the transition period Tt. As a result, the arc length Lb having a large arc length shown in FIG. 7 (A) does not continue for a long time, becomes an appropriate arc length Lc in a short time, and a penetration failure does not occur at the welding start portion. .

In the description of FIG. 9, at the start of welding, the welding pulse current Iw is supplied after the start current Ig is passed.
The control method of claim 2 for energizing the
In the present invention, even if the wire fusing of an excessive length occurs, it is possible to achieve an appropriate arc length in a short time,
As in the first aspect, the energization of the start current Ig can be omitted.

[Explanation of FIG. 10] FIG. 10 shows the time Ts until the wire 1 contacts the workpiece 2 and the arc 3 is generated.
It is a figure which shows the relationship between a [ms] (horizontal axis) and the number of flare-up start (vertical axis) when the arc length becomes large immediately after the wire 1 is melted and the arc 3 is generated. The welding conditions are as follows. Wire 1 has a diameter of 1.6
Using aluminum silicon alloy A4043 of [mm], aluminum magnesium alloy A5083 of plate thickness 12 [mm], welding current 150 [A], welding voltage 19
The welding current of [V] is applied, and the arc generation time is 5 seconds,
The arc start was performed by repeating the arc stop time of 30 seconds 250 times. The anti-stick condition was set so that the diameter of the molten sphere at the tip of the wire was 2 mm or less when the arc was stopped.

As shown in the figure, at the time of arc start, the number of times that the upper part of the wire tip 1a was melted and burned up and started was 30 times. The time Tsa until the arc 1 is generated when the wire 1 comes into contact with the workpiece 2 is 70 [m
[s] or more, the number of flare-up starts has significantly increased. As a result, 70 [ms] is appropriate for the set time.

[Explanation of FIG. 11] FIG. 11 shows that in the pulse MAG welding arc start control method of the present invention, after the wire 1 comes into contact with the object to be welded 2, the upper part of the wire tip 1a is melted and an arc 3 is generated. It is a figure which shows the welding start part when it is made to perform horizontal fillet welding. Welding conditions are
The welding conditions are the same as the horizontal fillet welding of the prior application shown in FIG. As shown in FIG. 8, in horizontal fillet welding of the prior application, fusion failure often occurs at the welding start portion 8a. However, as shown in FIG. 11, in the horizontal fillet welding of the present invention, the arc length can be quickly returned to an appropriate arc length after the upper part of the wire tip 1a is melted and the arc 3 is generated. Further, when the arc length is restored, the wire 1 does not come into contact with the object to be welded 2 and short-circuited, so that a good welding result can be obtained.

[0090]

【Example】

[Description of FIG. 12] FIG. 12 is a block diagram of a welding apparatus for carrying out the pulse MAG welding arc start control method of the present invention. In the figure, the same reference numerals as those in FIG. 5 are the same as those in the description of FIG.

In FIG. 12, the start sequence control circuit SI inputs the welding current energization signal Ie to the input terminal IN1 and the short circuit determination signal Vi0 to the input terminal IN2. Then, the hot start current conduction signal Si1 is output from the output terminal OUT1 to start current switching circuit SW6.
To enter. The start current switching circuit SW6 receives the start current Ig and the hot start current Ih when the hot start current energization signal Si1 is input, and makes a pulse when the hot start current energization signal Si1 is stopped. The control signal Pf is input and the current value setting signal S6 is output. The transition period start signal Si2 is output from the output terminal OUT2 and input to the transition pulse control circuit SR. This transition pulse control circuit SR, when the transition period start signal Si2 is stopped, transition pulse current It
A pulse width switching signal Tw for switching the pulse width of the pulse width is output stepwise.

[Description of FIG. 13] FIG. 13 is a specific block diagram of the start sequence control circuit SI shown in FIG. The input terminals IN1 and IN2 and the output terminals OUT1 and OUT2 shown in FIG. 13 are the same as IN1 and IN2 and OUT1 and O of the start sequence control circuit SI shown in FIG.
Corresponds to UT2.

In FIG. 13, the short circuit inverting circuit NOT1
Receives the short circuit determination signal Vi0 as an input, inverts it, and outputs an inverted signal Vi1. Flip-flop circuit FF1
Receives the welding current conduction signal Ie at the set terminal S, outputs the hot start drive signal Ff0, and inputs the inverted signal Vi1 at the reset terminal R to stop the hot start drive signal Ff0. Hot start inverting circuit N
The OT3 receives the hot start drive signal Ff0 as an input and inverts it to output a hot start inversion signal Ff1. The delay circuit DY1 inputs the hot start drive signal Ff0 and outputs a delay signal Dy. The monostable multivibrator circuit SM receives the inverted signal Ff1 as an input,
Transition sequence drive signal S which is a pulse signal for a fixed time
Output m.

The integration circuit SG receives the short circuit determination signal Vi0 as an input and integrates it to output a short circuit timed integration signal Sg that rises from the L level to the H level with the lapse of time t. The short circuit time limit voltage reference circuit VTH outputs a short circuit time limit voltage reference signal VTh. The fourth comparison circuit CM4 receives the short-circuit time-period integral signal Sg as an input, and short-circuit time-period voltage reference signal V
Compared with Th, the short circuit time limit comparison signal Cm4 is output only when the short circuit time integration signal Sg is larger than the short circuit time period voltage reference signal VTh. The short-circuit time period inversion circuit NOT4 receives the short-circuit time period comparison signal Cm4 as an input, inverts the same, and outputs the short-circuit time period inversion signal Nt4. The AND circuit AND receives the transition sequence drive signal Sm and the short circuit time period inversion signal Nt4 as input, and outputs the transition period start signal Si2 when both the transition sequence drive signal Sm and the short circuit time period inversion signal Nt4 are at the H level. . The OR circuit OR is
Hot start delay signal Dy and transition period start signal S
i2 and the input, this hot start delay signal Dy
When either of the transition period start signal Si2 and the transition period start signal Si2 is at the H level, the hot start current conduction signal Si1 is output.

[Explanation of FIG. 14] FIG. 14 is a diagram showing waveforms of respective portions of the block diagrams shown in FIGS. 12 and 13 when the short-circuit time between the wire 1 and the workpiece 2 is longer than the set time. is there. In FIG. 14, (A) shows the welding current I and the welding current detection signal Id which is the output of the welding current detection circuit ID.
FIG. 7B is a diagram showing the waveform of the arc voltage detection signal V, which is the output of the welding voltage V and the arc voltage detection circuit VD.
It is a figure which shows the waveform of d, (C) is a figure which shows the waveform of the welding current energization signal Ie which is an output of the welding current energization circuit IE, and (D) is a short circuit which is an output of the short circuit discriminating circuit VI. It is a figure which shows the waveform of the determination signal Vi0, (E) is a figure which shows the waveform of the hot start drive signal Ff0 which is an output of flip-flop circuit FF1.

In the same figure, (F) is a diagram showing the waveform of the hot start current conduction signal Si1 which is the output of the OR circuit OR, and (G) is the short circuit time integration signal Sg which is the output of the integration circuit SG. FIG. 7 is a diagram showing a waveform of a short circuit time limit voltage reference signal VTh which is an output of the short circuit time limit voltage reference circuit VTH. (H) is a diagram showing a waveform of a short-circuit timed comparison signal Cm4 which is an output of the fourth comparison circuit CM4, and (I).
FIG. 4 is a diagram showing a waveform of a short-circuit time period inversion signal Nt4 which is an output of the short-circuit time period inversion circuit NOT4, and (J) is a diagram showing a waveform of a transition sequence drive signal Sm which is an output of the monostable multivibrator circuit SM. Yes, (K) is the transition period start signal Si2 which is the output of the AND circuit AND
It is a figure showing the waveform of.

The transmission of signals with respect to time will be described with reference to FIG. When a welding start switch (not shown) is operated, the wire 1 comes into contact with the object 2 to be welded at time t1, and the welding current I is conducted to generate a welding current conduction signal as shown in FIG. Output Id. This welding current I
First, the start current Ig is supplied, and then,
A hot start current Ih, which is wider than the welding pulse current Iw, is applied.

The welding current energization circuit IE receives the welding current detection signal Id as an input and outputs the welding current energization signal Ie shown in FIG. 7C, which is input to the input terminal IN1 of the start sequence control circuit SI. Flip-flop circuit FF1
Receives the welding current conduction signal Ie as an input and outputs the hot start drive signal Ff0 shown in FIG. As a result, the OR circuit OR outputs the hot start current conduction signal Si1 shown in FIG.

At time t1, as shown in FIG. 7B, when the arc voltage detection signal Vd corresponding to the welding voltage V sharply decreases, the short circuit determination circuit VI causes the short circuit determination signal VI shown in FIG. Vi0 is output, and the integration circuit SG outputs the short-circuit time-limited integration signal Sg shown in FIG.

At time t2, when the short circuit time integration signal Sg shown in (G) of the figure reaches a level higher than the short circuit time period voltage reference signal VTh, the short circuit time period comparison signal Cm4 shown in (H) of FIG. Then, the short circuit time-delayed inversion signal Nt4 shown in FIG.

At time t3, as shown in FIG.
When an arc 3 is generated between the wire 1 and the work piece 2,
As shown in FIG. 14 (B), the welding voltage V and the arc voltage detection signal Vd increase, and as shown in FIG. 14 (D), the short circuit determination signal Vi0 becomes L level. Short circuit determination signal Vi0
Becomes L level, the short circuit inversion signal Vi1 shown in FIG.
Becomes H level and is input to the reset terminal R of the flip-flop circuit FF. Then, as shown in FIG. 14E, the hot start drive signal Ff0 becomes L level,
As shown in FIG. 14 (J), the monostable multivibrator SM outputs the sequence drive signal Sm which is a pulse wave for a fixed time and stops at time t5.

At time t3, the H-level sequence drive signal Sm is input to the AND circuit AND, but the other input signal, that is, the short-circuit time-reversal signal Nt4 is changed to that shown in FIG.
4 (I), it is at L level. As a result, the transition period start signal Si2 which is the output of the AND circuit AND
Is at the L level, the transition pulse control circuit SR does not operate.

In FIG. 13, the delay circuit DY1 receives the hot start drive signal Ff0 as an input and outputs a hot start delay signal Dy which stops a few microseconds later than the hot start drive signal Ff0 and outputs the OR circuit O1.
Enter in R. This is because when the operation delay of the flip-flop circuit FF1 occurs, the transition sequence drive signal S
This is to prevent the hot start current conduction signal Si1 from stopping before m becomes H level.

At time t4, as shown in FIG. 14F, when the hot start current conduction signal Si1 is stopped,
The start current switching circuit SW6 is switched to supply the welding pulse current Iw as shown in FIG.

[Explanation of FIG. 15] FIG. 15 is a diagram showing waveforms of respective parts of the block diagrams shown in FIGS. 12 and 13 when the short-circuit time between the wire 1 and the workpiece 2 is shorter than the set time. is there. Since the reference numerals shown in FIG. 15 are the same as those in FIG. 14, description thereof will be omitted, and in FIG. 15, signal transmission with respect to time will be described.

Since the signal transmission at time t1 is the same as the signal transmission at time t1 shown in FIG. 14, description thereof will be omitted.

At time t2, as shown in FIG.
When an arc 3 is generated between the wire 1 and the work piece 2,
As shown in FIG. 15B, the arc voltage detection signal Vd corresponding to the welding voltage V increases, and as shown in FIG. 15D, the short circuit determination signal Vi0 becomes L level. When the short circuit determination signal Vi0 becomes L level, the short circuit inversion signal Vi1 shown in FIG. 13 becomes H level, and the flip-flop circuit FF
1 is input to the reset terminal R. Then, FIG. 15 (E)
15, the hot start drive signal Ff0 becomes L level, and the monostable multivibrator SM operates as shown in FIG.
As shown in (J), the sequence drive signal Sm which is a pulse wave for a certain period of time is output and stopped at time t3.

At time t2, as shown in FIG. 15 (G), the short circuit time integration signal Sg is lower than the short circuit time period voltage reference signal VTh, so that the comparison circuit CM4 is operated as shown in FIG. , The short circuit time limit comparison signal Cm4 is not set to the H level. Since the short circuit time limit comparison signal Cm4 does not become the H level, the short circuit time period inversion signal Nt4 maintains the H level as shown in FIG. As a result,
Transition period start signal S which is the output of the AND circuit AND
As shown in (K) of the same figure, i2 becomes H level during the time t2 to t3 when the sequence drive signal Sm is H level.

At time t3, the hot start delay signal Dy of the two inputs of the OR circuit OR shown in FIG.
Has already stopped, and when the transition period start signal Si2 which is the other input is stopped, the hot start current conduction signal Si1 is stopped as shown in FIG. 15 (F).

At time t3, the hot start current conduction signal Si1 which is an input to the start current switching circuit SW6.
Is stopped, the hot start current Ih is switched to the pulse control signal Pf and the current value setting signal S6 is output. At this time t3, the transition period start signal Si
When 2 is stopped, the transition pulse control circuit SR starts operating. As a result, as shown in FIG. 15A, at the time t3 after the hot start current Ih is supplied, the transition pulse current It is supplied, and then the welding pulse current Iw is supplied.

9 to 15 describe the start control method of claim 2 in which the start current Ig is supplied at the start of welding and then the hot start current Ih is supplied, but the supply of the start current Ig is omitted. Then, a part of the configuration and the operation can be omitted and modified so as to correspond to the start control method of the first aspect.

[0140]

According to the invention of claim 1, at the start of welding, when the wire tip 1a comes into contact with the workpiece 2, after the hot start current Ih having a current value larger than the average value of the welding pulse current Iw is passed. In the pulse MAG welding arc start control method of passing the welding pulse current Iw, the short-circuit time to shift from the short circuit to the arc 3 is detected, and when the short-circuit time is within the set time, the hot start current I
The pulse width of the transition pulse current It that is energized during the transition period Tt from the end of energization of h to the start of energization of the welding pulse current Iw is changed from a pulse width larger than the pulse width Tp of the welding pulse current Iw to the welding pulse current Iw. The pulse width Tp is controlled stepwise, and when the short circuit time is longer than the set time, the hot start current Ih is directly switched to the welding pulse current Iw so that the spatter is caused by the wire short circuit immediately after the arc start. It does not occur, and burnback does not occur immediately after the arc start. Further, even when the upper part of the wire tip 1a made of a material having a poor arc starting property is melted and blown, the arc length is promptly restored to a proper arc length, so that no penetration failure occurs.

According to the second aspect of the invention, at the start of welding, a starting current Ig having a high current rising speed and a pulse current value Ip and a pulse width Tp smaller than the welding pulse current is supplied, and then the first aspect of the invention is performed. Described hot start current Ih
In addition to the effect of claim 1, the heat input until the wire is sufficiently heated can be prevented by energizing the wire to prevent the occurrence of the excessive fusing of the wire itself. In addition to the above effect, the occurrence of spatter is prevented and the arc length is quickly restored to an appropriate length, so that no penetration failure occurs.

[Brief description of drawings]

FIG. 1 is a diagram showing a time course of a position of a wire tip and an arc generation state at the time of arc start and a time course of a welding current at the arc start in the prior art 1.

FIG. 2 is a diagram showing a time course of a position of a wire tip and an arc generation state at the time of arc start and a time course of a welding current at the arc start in the prior art 2.

FIG. 3 is a diagram showing a welding voltage, a welding current, and a position of a wire tip at the time of arc start of the prior art 3 over time.

FIG. 4 is a diagram showing a time course of a position of a wire tip and an arc generation state at the time of arc start of the prior application and a diagram showing a time course of welding current at the arc start.

FIG. 5 is a block diagram of a pulse MAG welding apparatus for implementing the arc start control method of the prior application.

6 is a diagram showing a signal waveform of each part of the pulse MAG welding apparatus of FIG.

FIG. 7 is a diagram showing the time course of the position of the wire tip and the arc generation state at the time of arc start of the prior application when using a wire having a component with extremely difficult arc start and welding current. It is a figure which shows the time passage of.

FIG. 8 is a bead when the horizontal fillet welding of the prior application was carried out.

FIG. 9 is a diagram showing a time course of a position of a wire tip and an arc generation state at the time of arc start and a time course of a welding current at the arc start of the present invention.

FIG. 10 is a diagram showing the time until the wire contacts the workpiece and an arc is generated, and the number of burn-up starts when the arc length becomes large immediately after the wire is melted and the arc is generated. It is a figure which shows the relationship with.

FIG. 11 is a bead when horizontal fillet welding according to the present invention is performed.

FIG. 12 is a block diagram of a welding apparatus for carrying out the pulse MAG welding arc start control method of the present invention.

13 is a specific block diagram of the start sequence control circuit shown in FIG.

FIG. 14 is a diagram showing waveforms of the block diagrams shown in FIGS. 12 and 13 when the short-circuit time between the wire and the workpiece is longer than the set time.

FIG. 15 is a diagram showing waveforms of the block diagrams shown in FIGS. 12 and 13 when the short circuit time between the wire and the workpiece is shorter than the set time.

[Explanation of symbols]

 1 Wire 1a Wire Tip 2 Workpiece 3 Arc 3a Start Arc 4 Power Supply Tip 5 Nozzle 7a Sputter 7b (due to melting of wire tip part) Spatter 7b Spatter 8 Bead 8a Welding start part 21 Web 22 Flange Ig Start current Ih Hot start current Iw Welding pulse current Tp Welding pulse current Iw pulse width Th Hot start period Tt Transition period Tp1 First transition pulse width Tp2 Second transition pulse width Tp3 Third transition pulse width Tsa Short circuit to arc Time until transition It Transition pulse current It1 1st transition pulse current It2 2nd transition pulse current It3 3rd transition pulse current Tbt Transition base period WM Wire feeding motor WC Wire feeding control circuit IM Average current setting circuit ID Welding current Detection circuit I E Welding current energizing circuit VS Arc voltage setting circuit VD Arc voltage detecting circuit CM1 First comparing circuit CM2 Second comparing circuit CM3 Third comparing circuit CM4 Fourth comparing circuit VF Pulse frequency signal generating circuit IH Hot start current setting circuit IP pulse current Value setting circuit IB Base current setting circuit TP Pulse width setting circuit DF Pulse signal generation circuit SW4 Pulse base current switching circuit SW6 Start current switching circuit SI Start sequence control circuit PS Welding output control circuit SR Transition pulse control circuit SG Integration circuit VTH Short circuit time limit Voltage reference circuit FF flip-flop circuit FF1 flip-flop circuit DY1 delay circuit SM monostable multivibrator circuit VI short circuit determination circuit WD wire feeding speed detector TM delay circuit OR OR circuit AND AND circuit NOT 1 Short circuit inversion circuit NOT3 Hot start inversion circuit NOT4 Short circuit timed inversion circuit Wd Wire feed speed detection signal Wc Wire feed control signal Vs Arc voltage setting signal Vd Arc voltage detection signal Im Average current setting signal Id Welding current detection signal Ie Welding Current energizing signal Ip Pulse current value setting signal Ig Start current Ih Hot start current Ib Base current setting signal Cm1 Arc current control signal Cm2 Arc voltage control signal Cm3 Current value control signal Cm4 Short circuit time limit comparison signal Vf Pulse frequency signal Tp pulse Width setting signal Tm Delay signal Tw Pulse width switching signal S6 Current value setting signal Df Pulse width frequency control signal Pf Pulse control signal Si1 Hot start current energizing signal Si2 Transition period start signal Vi0 Short circuit discrimination signal Vi1 Short circuit inversion signal Sg Short product Signal VTh short timed voltage reference signal Ff FF output signal Ff0 hot start drive signal Ff1 hot start inverting signal Nt4 short timed inverted signal Dy hot start delay signal Sm transition sequence driving signal

Claims (2)

[Claims] 1. A pulsed MAG welding arc in which a welding pulse current is applied after a hot start current having a current value larger than the average value of the welding pulse current is applied when the tip of the wire comes into contact with the workpiece at the start of welding. In the start control method, detecting a short-circuit time to shift from a short circuit to an arc, and when the short-circuit time is within a set time, shift from the end of energization of the hot start current to the start of energization of the welding pulse current. The pulse width of the transition pulse current to be energized during the period is controlled so that the pulse width of the welding pulse current is gradually changed from the pulse width larger than the pulse width of the welding pulse current, and the short-circuit time is set from When the length is too long, a pulse MAG welding arc start control method for directly switching from the hot start current to the welding pulse current . 2. A pulsed MAG welding arc in which a welding pulse current is applied after a hot start current having a current value larger than the average value of the welding pulse current is applied when the tip of the wire comes into contact with the workpiece at the start of welding. In the start control method, the current rising speed is high, the pulse current value and the pulse width are smaller than the welding pulse current, and the start current is supplied, and then the short-circuit time from the short-circuit to the arc is detected. If is within the set time,
The pulse width of the transition pulse current energized during the transition period from the end of energization of the hot start current to the start of energization of the welding pulse current, the welding pulse current from a pulse width larger than the pulse width of the welding pulse current Pulse MAG welding arc start control method in which control is performed in steps up to the pulse width, and when the short circuit time is longer than a set time, the hot start current is directly switched to the welding pulse current.