CN102950366B

CN102950366B - Welder

Info

Publication number: CN102950366B
Application number: CN201210286975.6A
Authority: CN
Inventors: 井手章博; 惠良哲生
Original assignee: Daihen Corp
Current assignee: Daihen Corp
Priority date: 2011-08-25
Filing date: 2012-08-13
Publication date: 2016-05-04
Anticipated expiration: 2032-08-13
Also published as: CN102950366A; JP5770047B2; JP2013043213A

Abstract

The invention provides and a kind ofly can realize the welder that the growth of stable molten drop and stable electric arc produce. Welder (100) possesses power circuit (102) and power control (104). Power control (104) according to the 1st arc period (Ta1) the output high level of current at the initial stage of ensuing arc period after during short circuit, export the mode control power circuit (102) of the arc current corresponding with the weldingvoltage that carried out constant voltage control at the 2nd arc period (Ta2) in later stage of arc period. Power control and then according to the waveform of increase and decrease being repeatedly superimposed on to amplitude center electric current to produce the mode control power circuit of high level of current. Power control and then calculate recommendation magnitude of voltage corresponding to the current setting value of welding current, according to recommending magnitude of voltage and the voltage official post amplitude center electric current between the voltage setting value of weldingvoltage to increase and decrease. Thus, even if also can prevent that in the situation that having changed voltage setting value electric arc from becoming unstable.

Description

Welder

Technical field

The present invention relates to welder, relate in particular to and carry out the welding dress that co3 gas arc welding connectsPut.

Background technology

In Japanese Patent Publication 4-4074 communique (patent documentation 1), disclose consumable electrode withThe consumable electrode formula arc-welding method that between mother metal, short circuit and electric arc produce repeatedly. This consumable electrode formulaArc-welding method repeatedly the forming process of molten drop and molten drop to the transient process of mother metal transition.

Figure 13 is for consumable electrode formula arc-welding method that short circuit repeatedly and electric arc produces is describedFigure.

With reference to Figure 13, in the consumable electrode formula arc-welding method that short circuit and electric arc produce repeatedly,Below the process of (a)～(f) of explanation is carried out in order repeatedly. (a) molten drop has contacted with molten bathShort circuit A-stage; (b) contacting of molten drop and molten bath becomes short to molten bath transition of reliable and molten dropRoad state in mid-term; (c) molten drop of molten drop to pool side transition and between welding wire and molten bath produced contractingThe short circuit later stage state of neck; (d) short circuit disconnects and has produced the state of electric arc; (e) front end of welding wireThe electric arc of melting and molten drop growth produces state; (f) molten drop growth and be about to molten bath short circuit beforeElectric arc produces state.

Patent documentation 1: Japanese Patent Publication 4-4074 communique

Patent documentation 2: No. 4702375 description of Japan Patent

In the short circuiting arc welding in the past shown in Japanese Patent Publication 4-4074 communique, regularlyProduce electric arc and short circuit. But, utilizing co3 gas arc welding connection with the (weldering of high electric currentThe diameter of silk is 1.2mm and the electric current that exceedes 200A) in the situation of welding, with shortIn the droplet transfer on road, due to electric arc reaction force make molten drop on welding wire top wrinkling (Ga on せりり), so arc duration extend and be difficult to produce periodic short circuit, therefore produce brokenly electric arc andShort circuit.

Like this, if the cycle of short circuit and electric arc changes brokenly, droplet size when short circuit is solidFixed, the consistent degree variation of welding bead toe (beadtoe) portion.

In addition, because high electric current acts on excessive electric arc with respect to molten bath in irregular positionPower, institute is so that molten bath becomes greatly and brokenly vibration, especially makes molten bath to contrary with welding direction oneSide is protruded, thereby easily produces protuberance welding bead.

Particularly, require speed of welding to become at a high speed in order to boost productivity, wherein in high-speed weldingThe deteriorated of the welding quality that the impact of middle the problems referred to above brings displays significantly. In addition, for makingSpeed of welding becomes at a high speed, need to accelerate welding wire feeding speed with the deposited amount of the unit of obtaining. Accompany with it,Exist welding current to become large this relation.

In addition, the most situation of welder has following function: if set electric current or welding wire entersThe speed of giving has been determined recommendation voltage (also referred to as monobasic voltage) automatically. In contrast, operator is largeSusceptible condition is also that limit watches the result limit of welding that weldingvoltage is set as being different from the value of recommending voltage.But, if setting voltage is set extremely greatly with respect to recommending voltage or littlely extreme, electricIt is unstable that arc easily becomes.

Summary of the invention

The object of the present invention is to provide and a kind ofly can realize the growth of stable molten drop and stable electric arcThe welder producing.

In brief, the invention provides a kind of use carbon dioxide that passes through as protective gas friendshipFor ground repeatedly the co3 gas arc welding of short-circuit condition and conditions at the arc connect method and weldWelder, this welder possesses: power circuit, it for providing between welding torch and mother metalVoltage; And control part, it controls the voltage of power circuit. Control part connects after during short circuitThe 1st arc period output high level of current at the initial stage of the arc period getting off, after arc periodThe 2nd arc period output electric arc electricity corresponding with the weldingvoltage that carried out constant voltage control of phaseThe mode control power circuit of stream. Control part so according to by repeatedly increase and decrease waveform be superimposed in amplitudeElectrocardio flows to produce the mode control power circuit of high level of current. Control part and then electric corresponding to weldingThe current setting value of stream calculates recommendation magnitude of voltage, establishes according to the voltage of recommending magnitude of voltage and weldingvoltageVoltage difference between definite value makes the electric current increase and decrease of amplitude center.

On the other hand, the invention provides a kind of passing through and use carbon dioxide as protective gas alsoAlternately the co3 gas arc welding of short-circuit condition and conditions at the arc connects method and welds repeatedlyThe welder connecing, this welder possesses: power circuit, it for carrying between welding torch and mother metalVoltage supplied; And control part, it controls the voltage of power circuit. Control part is according to after during short circuitThe 1st arc period output high level of current at the initial stage of ensuing arc period, at arc periodThe 2nd arc period output electric arc corresponding with the weldingvoltage that carried out constant voltage control in later stageThe mode control power circuit of electric current. Control part so according to by repeatedly increase and decrease waveform be superimposed on amplitudeCenter electric current is to produce the mode control power circuit of high level of current. Control part and then corresponding to weldingThe current setting value of electric current calculates recommendation magnitude of voltage, according to the voltage of recommending magnitude of voltage and weldingvoltageVoltage difference between setting value makes the 1st arc period increase and decrease.

On the other hand, the invention provides a kind of passing through and use carbon dioxide as protective gas alsoAlternately the co3 gas arc welding of short-circuit condition and conditions at the arc connects method and welds repeatedlyThe welder connecing, this welder possesses: power circuit, it for carrying between welding torch and mother metalVoltage supplied; And control part, it controls the voltage of power circuit. Control part is according to after during short circuitThe 1st arc period output high level of current at the initial stage of ensuing arc period, at arc periodThe 2nd arc period output electric arc corresponding with the weldingvoltage that carried out constant voltage control in later stageThe mode control power circuit of electric current. Control part so according to by repeatedly increase and decrease waveform be superimposed on amplitudeCenter electric current is to produce the mode control power circuit of high level of current. Control part and then corresponding to weldingThe current setting value of electric current calculates recommendation magnitude of voltage, establishes at the voltage of recommending magnitude of voltage and weldingvoltageVoltage difference between definite value is in the situation of the 1st scope, according to voltage difference, amplitude center electric current is increasedSubtracting, is to be different from the 2nd scope of the 1st scope in voltage difference, makes according to voltage difference1 arc period increase and decrease.

In above-mentioned any one welder, preferably, the waveform of increase and decrease is triangular wave or sine repeatedlyRipple.

In above-mentioned any one welder, preferably, the necking down of molten drop detected in during short circuitIn situation, control part makes the necking down that short circuit current reduces detect control.

Invention effect

According to the present invention, connect in method at co3 gas arc welding, by will be with fixed frequency andMeet after the electric current that waveform that the amplitude of droplet size increases and decreases is superimposed on the arc period initial stage defeatedGo out electric current, can realize thus stable molten drop growth. Thereby can not produce at the electric arc initial stage needn'tThe short circuit of wanting, can obtain high welding stability. In addition, even if set according to welderRecommend voltage to carry out change setting voltage, also can prevent that electric arc from becoming unstable.

Brief description of the drawings

Fig. 1 is the block diagram of the welder that relates to of embodiment 1.

Fig. 2 shows the weldingvoltage when the welder being related to by embodiment 1 weldsAnd the movement oscillogram of welding current.

Fig. 3 shows the figure of the state of the welding portion under the t=t3 of Fig. 2.

Fig. 4 shows the figure of the state of the welding portion under the t=t4 of Fig. 2.

Fig. 5 shows the figure of the state of the welding portion under the t=t5 of Fig. 2.

Fig. 6 shows the figure of the state of the welding portion under the t=t7 of Fig. 2.

Fig. 7 shows the block diagram of the formation of the welder 100A that embodiment 2 relates to.

Fig. 8 shows the block diagram of the formation of the welder 100B that embodiment 3 relates to.

Fig. 9 shows the block diagram of the formation of the welder 100C that embodiment 4 relates to.

Welding electricity when Figure 10 shows the welder being related to by embodiment 4 and weldsAnd the movement oscillogram of welding current and control signal.

Figure 11 shows the block diagram of the formation of the welder 100D that embodiment 5 relates to.

Figure 12 shows the block diagram of the formation of the welder 100E that embodiment 6 relates to.

Symbol description:

1 welding wire; 2 mother metals; 3 electric arcs; 4 welding torches; 5 feed rolls; 6 molten drops; 7 is moltenPond; 100,100A～100E welder; 102,102A power circuit; 104,104A～104E power control; 106 feed arrangements; AD arc detection circuitry; DEC baseAccurate voltage error signal distributor circuit; DR drive circuit; EC voltage error circuit; EV electricityPress error amplifying circuit; EI current error amplifying circuit; FC feeding control circuit; FH frequentlyRate initialization circuit; FR feed speed initialization circuit; G1R, G2R gain setting circuit; ID electricityCurrent detection circuit; IHCR amplitude center current setting circuit; IR welding current initialization circuit;NA NAND circuit; ND necking down testing circuit; NOT circuit for reversing; R current-limiting resistor;SW external behavior commutation circuit; TM timer circuit; TR1, TR2 transistor; VA electricityPress averaging circuit; VCR reference voltage setting circuit; VD voltage detecting circuit; VR welderingConnect voltage setting circuit; VTN detection reference value initialization circuit; WH amplitude setting circuit;WL1, WL2 reactor.

Detailed description of the invention

Below, with reference to accompanying drawing, embodiments of the present invention are elaborated. Wherein, in the drawings,Give identical symbol about identical or appropriate section, do not repeat explanation. In addition, in this realityExecute the welding method that the welding method illustrating in mode is repeatedly short-circuit condition and conditions at the arc, be different fromPulse arc welding method.

[embodiment 1]

Fig. 1 is the block diagram of the welder that relates to of embodiment 1.

With reference to Fig. 1, welder 100 comprises: power circuit 102, power control 104,Wire feed unit 106 and welding torch 4.

Power control 104 control power circuit 102 and control be: the welding of exporting to welding torch 4Electric current I w and weldingvoltage Vw become the value that is suitable for welding.

Wire feed unit 106 is to welding torch 4 feeding welding wires 1. Although not shown, with titanium dioxideCarbon gas is that the protective gas of principal component is released from the fore-end of welding torch 4. From welding torch 4Between the welding wire 1 that distal process goes out and mother metal 2, produce electric arc 3, welding wire 1 melting and mother metal 2 is weldedConnect. Wire feed unit 106 comprises: feed speed initialization circuit FR, feeding control circuit FC,Feeding motor WM and feed rolls 5.

Power circuit 102 comprises: electric power main circuit PM, reactor WL1 and WL2, transistorTR1, voltage detecting circuit VD and current detection circuit ID.

Electric power main circuit PM, using the source power supply (not shown) of 3 phase 200V etc. as input, pressesCarry out the output control based on inverter control according to error amplification signal Ea described later, output is suitable for electricityThe welding current Iw of arc welding and weldingvoltage Vw. Although not shown, electric power main circuit PMFor example be configured to and comprise: to source power supply carry out No. 1 rectifier of rectification, to the direct current after being rectifiedCarry out level and smooth capacitor, the DC converting after smoothed become to inverter circuit, the general of high-frequency acHigh-frequency ac is depressurized to the high frequency transformer of the magnitude of voltage that is suitable for arc welding, to by the high frequency after step-downInterchange is carried out No. 2 rectifiers of rectification and error amplification signal Ea is carried out to arteries and veins as inputRush width modulated control and drive the drive circuit of above-mentioned inverter circuit based on this result.

Reactor WL1 and reactor WL2 carry out smoothly the output of electric power main circuit PM. ElectricityThe anti-device WL2 transistor T R1 that is connected in parallel. Illustrated in fig. 2 according to below of transistor T R1The 2nd arc period become low level (Low) with non-(NAND) logical signal Na, only existThe 2nd arc period Ta2 is in cut-off (OFF).

Feed speed initialization circuit FR output is suitable with predetermined stable feed speed setting valueFeed speed setting signal Fr. Feeding control circuit FC will be used for with feed speed setting signalThe feeding control signal Fc of the feed speed feeding welding wire 1 that the value of Fr is suitable exports feeding motor toWM. Welding wire 1 is according to the rotation of the feed rolls 5 of wire feed unit 106 and by entering in welding torch 4Advance to, and mother metal 2 between produce electric arc 3.

Current detection circuit ID detects welding current Iw, and exports welding current detection signal Id. ElectricityPress testing circuit VD to detect weldingvoltage Vw, and export weldingvoltage detection signal Vd.

Power control 104 is configured to and comprises: arc detection circuitry AD, timer circuit TM,In non-(NAND) circuit NA, circuit for reversing NOT, gain setting circuit G1R, amplitudeHeart current setting circuit IHCR, frequency setting circuit FH, amplitude setting circuit WH, welding electricityStream initialization circuit IR, current error amplifying circuit EI, weldingvoltage initialization circuit VR, benchmark electricityPressure initialization circuit VCR, voltage error amplifying circuit EV and EC, average voltage circuit VA,And external behavior commutation circuit SW.

Arc detection circuitry AD is using weldingvoltage detection signal Vd as input, and if output due toThe value of weldingvoltage detection signal Vd reaches the above differentiation generation of threshold value electric arc and becomes height (High)The arc detection signal Ad of level. Timer circuit TM is using arc detection signal Ad as input,And export during arc detection signal Ad is low (Low) level and believe from arc-detectionNumber Ad becomes the timer signal of high level in becoming during rise after high level predeterminedTm. NAND circuit NA receive timer signal Tm be inverted signal after circuit NOT reversion andArc detection signal Ad is used as input, and exports NAND Logic signal Na.

Weldingvoltage initialization circuit VR output is waited the weldingvoltage setting signal Vr setting by operator(being equivalent to the voltage Vr of Fig. 2). Average voltage circuit VA output makes weldingvoltage detection signalAverage voltage detection signal Va after Vd equalization. Voltage error amplifying circuit EV amplifies welding electricityPress the error between setting signal Vr and average voltage detection signal Va, and output voltage error is putLarge-signal Ev.

Reference voltage setting circuit VCR output reference voltage setting signal Vcr, this reference voltage is establishedDetermining signal Vcr represents to become according to the welding condition corresponding to welding wire feeding speed, speed of welding etc.The predetermined voltage setting value of mode of suitable arc length. This reference voltage setting signal VcrBe equivalent to monobasic voltage center. Voltage error circuit EC calculates weldingvoltage setting signal Vr and baseError between accurate voltage setting signal Vcr, and output reference voltage error signal Ec.

Gain setting circuit G1R exports predetermined the 1st gain setting signal G1r. In amplitudeHeart current setting circuit IHCR is by the 1st gain setting signal G1r and reference voltage error signal Ec(=Vr-Vcr) conduct input, and export the amplitude center current settings signal that time formula (1) illustratesIhcr。

Ihcr＝Ihcr0+G1r*(Vr-Vcr)…(1)

Wherein, Ihcr represents amplitude center current settings signal, and Ihcr0 represents reference voltage setting letterNumber corresponding reference amplitude of Vcr center current settings signal, G1r represents the 1st gain setting signal,Vr represents weldingvoltage setting signal, and Vcr represents reference voltage setting signal. G1r for example can establishBe 10～50 (A/V). This expression: for voltage deviation 1V, amplitude center electric current is establishedThe amplitude of variation of determining signal Ihcr is 10～50A.

Frequency setting circuit FH exports predetermined frequency setting signal Fh. Amplitude setting circuitWH exports predetermined amplitude setting signal Wh. Welding current initialization circuit IR is by amplitudeElectrocardio stream setting signal Ihcr, frequency setting signal Fh and amplitude setting signal Wh be as input,And export welding current setting signal Ir. Current error amplifying circuit EI amplifies welding current and sets letterError between number Ir and welding current detection signal Id, and output current error amplification signal Ei.

External behavior commutation circuit SW receives timer signal Tm, current error amplifying signal EiAnd voltage error amplifying signal Ev is used as input.

External behavior commutation circuit SW switches in input terminal in the time that timer signal Tm is high levelA side, and current error amplifying signal Ei is exported as error amplification signal Ea. Now,Because current error is fed back to electric power main circuit PM, so carry out constant current control.

External behavior commutation circuit SW switches in input terminal in the time that timer signal Tm is low levelB side, and voltage error amplifying signal Ev is exported as error amplification signal Ea. According to thisA little modules are controlled welding current Iw. Now, because voltage error is fed back to electric power main circuit PM,So carry out constant voltage control.

Fig. 2 show weldingvoltage when the welder that relates to embodiment 1 welds andThe movement oscillogram of welding current.

With reference to Fig. 1, Fig. 2, advance welding by Ts during short circuit repeatedly and arc period. Electric arcBe divided into during this time: the 1st arc period Ta1 at initial stage and the 2nd arc period Ta2 in later stage.

Ts during the short circuit of moment t0～t2, welding wire 1 and mother metal 2 contact and flow short circuit electricityStream, produce Joule heat, thereby the front end of welding wire 1 is in high temperature at the front end of welding wire 1.

At moment t2, if droplet transfer of the leading section of welding wire 1 and produce electric arc, power supply controlDevice 104 is differentiated and has been produced electric arc corresponding to weldingvoltage sharply rises. Correspondingly, power supplyControl is switched to constant current control by control device 104, and transit to the 1st arc period Ta1.Welding current rises to high level of current (amplitude center is amplitude center electric current I hcr). Then, existDuring fixing as welding current and the high level of current that flowing. This high level of current is suppressed to:The wrinkling current value that can not produce degree of molten drop causing because of arc force. Will be at the 1st arc periodIn Ta1, mobile welding current is called high level of current.

If welder 100 is set to welding wire feeding speed or welding current (mean value), correspondingRecommendation voltage (monobasic voltage) Vcr determine. In contrast, operator can utilize weldingvoltageSetting signal Vr sets setting voltage Vr.

Afterwards, power control 104 (is set letter corresponding to weldingvoltage according to setting voltage VrNumber Vr) and reference voltage V cr (corresponding to reference voltage setting signal Vcr) between voltage difference comeMake amplitude center electric current I hcr increase and decrease.

By reduce amplitude center electric current I hcr in the time that setting voltage Vr is low, thereby prevent at electric arcInitial stage (the 1st arc period Ta1) the excessive melting of welding wire during this time, between electric arc latter half the (the 2ndArc period Ta2) constant voltage control under easily reduce output voltage.

On the contrary, by promote amplitude center electric current I hcr in the time that setting voltage Vr is high, thereby at electricityInitial stage during arc, (the 1st arc period Ta1) made the abundant melting of welding wire, between electric arc latter half (2 arc period Ta2) constant voltage control under easily promote output voltage.

And, in the example of Fig. 2, make the waveform (for example triangular wave) of increase and decrease for high level of currentSuperpose. In addition, even if be the waveform stack of high level of current, also in the case of not making increase and decreaseCan make as described above amplitude center electric current I hcr increase and decrease, then set it as high level of current.But, if stack increase and decrease waveform obtains the more welding of high-quality.

Vm=α I+ β I for the melting speed Vm of welding wire²R represents. Wherein, α, β represent beNumber, I represents welding current, R represents that welding wire is outstanding from the contact mouth (contacttip) of welding torch front endThe resistance value of part (outstanding length). Hence one can see that, if welding current I is increased, and welding wireMelting speed Vm also become large.

But if welding current I increases, the arc force upwards that acts on molten drop also increases. ElectricityArc power and welding current I's is square proportional. On the other hand, because gravity also acts on molten drop, because ofAnd taking gravity and arc force just in time the current value of balance as boundary, if the large effect of current value power upwards,Act on downward power if current value is little. If make alternating current and welding current I stack, upwardsPower and downward power alternately act on molten drop. The present application person is known: by making like this electric current enterRow increase and decrease and make upwards downward power alternately act on the situation of molten drop, and by integrally making electric currentThe situation increasing and make power upwards act on continuously molten drop is compared, and molten drop is stable and canMinimizing is splashed. Therefore, in the present embodiment, make electric current increase and decrease at the 1st arc period, thus canTo seek, molten drop is stablized and interim growth.

During moment t3～t6 among the 1st arc period Ta1, make the triangle of following explanationRipple is superimposed on amplitude center electric current I hcr.

If the triangular wave superposeing centered by amplitude center electric current I hcr (200～400A), frequencyFor 2.5kHz～5kHz, the 1st arc period Ta1 is 0.3ms～3.0ms. If amplitude is+-50～100A. For example, can set amplitude center electric current I hcr be also Ihcr=400A, frequency is f=4kHz, the 1st arc period is Ta1=1.0ms, the triangular wave superposeing was 4 cycles. In addition,The waveform superposeing is not limited to triangular wave, can be also sinusoidal wave other waveform that waits.

Below, the state of the welding portion in the 1st arc period Ta1 is elaborated.

(1) 0～1/2 cycle of triangular wave

Fig. 3 shows the figure of the state of the welding portion under the t=t3 of Fig. 2. T=t3 is triangular waveThe time point that starts of stack.

With reference to Fig. 3, between the front end of welding wire 1 and mother metal 2, produce electric arc 3. Brought by electric arc 3Heat and make the front end of welding wire 1 heated, leading section melting, forms molten drop 6. Welding wire 1 is enteredCarry out feeding along mother metal 2 directions to device.

Due to the electric current after stack, welding wire melting speed increases, and it is large that molten drop becomes, and puts on the power of molten dropBe maximum in 1/4 cycle, molten drop is accelerated wrinkling because of electric arc reaction force. But, because companionAlong with electric current reduced towards 1/2 cycle, electric arc reaction force also declines, thereby can prevent wrinkling.

Fig. 4 shows the figure of the state of the welding portion under the t=t4 of Fig. 2. T=t4 be throughThe time point in 1/2 cycle of triangular wave. As shown in Figure 4, the molten drop 6 of the leading section of welding wire 1 slightlyGrowth, in wrinkling a little state.

(2) 1/2～3/4 cycle of triangular wave

During this period, make welding current reduce than electrocardio in amplitude by power control 104Ihcr is little for stream, thereby the electric arc reaction force of molten drop is further declined.

(3) 3/4～1 cycle of triangular wave

In 3/4～1 cycle of triangular wave, welding current is increased again from the downside peak value of triangular waveAdd to amplitude center electric current I hcr.

Fig. 5 shows the figure of the state of the welding portion under the t=t5 of Fig. 2. T=t5 be throughThe time point in 1 cycle of triangular wave. As shown in Figure 5, because electric arc reaction force has declined, make to doFor gravity and the just in time balance of electric arc reaction force of molten drop 6. Thereby, eliminate the wrinkling of molten drop 6,Molten drop 6 is in sagging state.

And, make the triangular wave illustrating in (1)～(3) repeatedly be superimposed on and shake stipulated numberWidth center electric current I hcr. Thus, can prevent because of electric arc reaction force cause wrinkling, again can be graduallyIncrease the molten drop that droplet size forms desired size.

In addition, in order easily to carry out the stack of triangular wave, by the inductance value of the 1st arc period Ta1WL1 sets littlely than ensuing the 2nd arc period Ta2 (inductance value is WL1+WL2).

Below, the state of the welding portion in the 2nd arc period Ta2 is elaborated. AgainWith reference to Fig. 2, finish and transit to the 2nd arc period Ta2 at moment t2 the 1st arc period Ta1.At the 2nd arc period Ta2, power control 104 increases the inductance value of power circuit 102, forCarry out arc length control and control switched to constant voltage control from constant current control. This is cutChange, in Fig. 1, be equivalent to external behavior commutation circuit SW to switch to terminal b from terminal a. CauseFor inductance is large, so welding current reduces lentamente according to arc load. In addition, weldingvoltage is also slowSlowly reduce.

The molten drop forming at the 1st arc period Ta1 as shown in Figure 6, can be not wrinkling, the 2ndIn arc period Ta2, limit becomes a little large limit and moves closer to molten bath. Because prevented the electricity causing because of wrinklingThe variation of arc length degree and by constant voltage control adjust arc length the variation of arc force is becomeSlowly, so that the situation of molten bath vibration is few. And then, because welding current reduces lentamente, soHeat input to mother metal is fully carried out, and the fusion of the toe portion of welding bead becomes good.

At the moment of Fig. 2 t8, if molten drop contacts with molten bath and produces short circuit, weldingvoltage sharplyDecline. If the power control of Fig. 1 104 is differentiated short circuit because of the sharply decline of this weldingvoltage,Make welding current increase with the rising edge speed of expecting. Because of the rising of welding current, make electricityMagnetic convergent force acts on the top of molten drop and produces necking down, thereby molten drop 6 is to molten bath 7 transition.

As described above, the welding method shown in embodiment 1 is carried out low spatter controlCo3 gas arc welding connection, is different from pulse arc welding method.

, the welding method shown in embodiment 1 is repeatedly the welding side of short-circuit condition and conditions at the arcMethod. In this welding method, if lifting speed of welding and welding current is increased, moltenDrip in transitional region and weld, short-circuit condition and conditions at the arc repeatedly become irregular.

Therefore, in the welding method shown in embodiment 1, the 1st arc period during necessarilyTa1 exports high level of current, carries out constant current control at the 1st arc period Ta1, and stack exchangesElectric current, for example low-frequency current of periodically variable fixed frequency as triangular wave or sine wave. ByThis, can prevent molten drop because of electric arc reaction force cause wrinkling, can realize stable molten drop rawLong.

And, about the amplitude center of high level of current, according to setting voltage Vr (corresponding to weldingVoltage setting signal Vr) and reference voltage V cr (corresponding to reference voltage setting signal Vcr) betweenVoltage difference make amplitude center electric current I hcr increase and decrease.

On the contrary, by increase amplitude center electric current I hcr in the time that setting voltage Vr is high, thereby at electricityInitial stage during arc, (the 1st arc period Ta1) made the abundant melting of welding wire, between electric arc latter half (2 arc period Ta2) constant voltage control under easily increase output voltage.

After having passed through the 1st arc period Ta1, long in order to carry out electric arc at the 2nd arc period Ta2Degree is controlled, and the control of the source of welding current is switched to constant voltage control from constant current control. To weldThe inductance value of the reactor of power supply is set also greatlyr than the 1st arc period Ta1, thereby makes welding currentReduce lentamente. Thus, the variation of arc force becomes slowly, so that the situation of molten bath vibration tail off.And then, because welding current reduces lentamente, thus fully carry out to the heat input of mother metal, welding beadIt is good that the fusion of toe portion becomes.

In above-mentioned embodiment 1, in order to make the reactance of the source of welding current at the 2nd arc period Ta2The inductance value of device is greater than the 1st arc period Ta1, and has inserted actual reactor WL2. Get andDai Zhi, mode control reactor that also can electronics increases inductance value.

In above-mentioned embodiment 1, also can, during short circuit in Ts, keep constant voltage controlMake in constant situation electric current be increased to desired value, or by control switch to constant current control itAfter electric current is increased to desired value.

In addition, the example that makes triangular wave be superimposed on high level of current has been shown in above-mentioned embodiment 1Son, even if but in the situation that not superposeing triangular wave, also can be based on setting voltage Vr and benchmark electricityPress the voltage difference between Vcr that high level of current is changed, thereby can prevent that electric arc from becoming unstableFixed.

[embodiment 2]

In embodiment 1, although the voltage based between setting voltage Vr and reference voltage V crThe poor size variation that makes high level of current, but in embodiment 2, based on setting voltage VrAnd during the voltage difference between reference voltage V cr makes the high level of current shown in Fig. 2 the (the 1stArc period Ta1) change.

Fig. 7 shows the block diagram of the formation of the welder 100A that embodiment 2 relates to. WithUnder explanation in, only explanation is different from the part of embodiment 1, about identical with embodiment 1Part is given identical not repeat specification of symbol.

With reference to Fig. 7, welder 100A comprises: power circuit 102, power control 104A,Wire feed unit 106 and welding torch 4.

Power control 104A, in the formation of the power control 104 shown in Fig. 1, replacesGain setting circuit G1R and comprise gain setting circuit G2R. Gain setting circuit G2R output is pre-The 2nd gain setting signal G2r first determining. The output of gain setting circuit G2R is input to meterTime device circuit TM.

In Fig. 1, although amplitude center current setting circuit IHCR is based on reference voltage error signalEc and exported amplitude center current settings signal Ihcr, but in Fig. 7, amplitude center electric currentInitialization circuit IHCR exports predetermined amplitude center current settings signal Ihcr.

In addition, the reference voltage error signal Ec that voltage error circuit EC exports inputs to timingDevice circuit TM, replaces and is input to amplitude center current setting circuit IHCR.

Timer circuit TM is by arc detection signal Ad, the 2nd gain setting signal G2r and benchmarkVoltage error signal Ec is as input, and output is only low (Low) at arc detection signal AdThe 1st arc period Ta1 during level and from arc detection signal Ad becomes high levelInside become the timer signal Tm of high level. The 1st arc period Ta1 is shown by inferior formula (2)Show.

Ta1＝Ta10+G2r*(Vr-Vcr)…(2)

Wherein, Ta1 represents the 1st arc period, and Ta10 represents and reference voltage setting signal VcrCorresponding benchmark the 1st arc period, G2r represents the 2nd gain setting signal, Vr represents welding electricityPress setting signal, Vcr represents reference voltage setting signal. In addition, can establish G2r for for example 100～500 (μ s/V). This expression: for voltage deviation 1V, the 1st arc period Ta1'sAmplitude of variation is 100～500 μ s.

In addition, because the power supply shown in formation and Fig. 1 of other parts of power control 104AControl device 104 is identical, so not repeat specification.

The welder 100A of embodiment 2 is based between setting voltage Vr and reference voltage V crVoltage difference make the 1st arc period Ta1 change, even if thus setting voltage Vr has been changedSituation under, with embodiment 1 similarly, also can prevent that electric arc from becoming unstable.

[embodiment 3]

In embodiment 1, only make amplitude center current settings signal according to voltage difference (Vr-Vcr)Ihcr increase and decrease only makes the 1st arc period Ta1 increase and decrease in embodiment 2.

In embodiment 3, voltage difference is arranged to upper and lower threshold value, only make amplitude center current settingsSignal Ihcr increases and decreases to till threshold value, and about having exceeded the voltage difference of threshold value or being less than the electricity of threshold valuePressure reduction, only makes the 1st arc period Ta1 increase and decrease.

Fig. 8 shows the block diagram of the formation of the welder 100B that embodiment 3 relates to. WithUnder explanation in, only explanation is different from the part of embodiment 1, about identical with embodiment 1Part is given identical not repeat specification of symbol.

With reference to Fig. 8, welder 100B comprises: power circuit 102, power control 104B,Wire feed unit 106 and welding torch 4.

Power control 104B, in the formation of the power control 104 shown in Fig. 1, enters oneStep comprises reference voltage error signal distributor circuit DEC and gain setting circuit G2R. Gain settingCircuit G2R exports predetermined the 2nd gain setting signal G2r.

Reference voltage error signal distributor circuit DEC receives upper limit threshold Tv1, lower threshold Tv2With reference voltage error signal Ec, and output reference voltage error distribution current signal Eri and benchmarkVoltage distribution time signal Ert.

Reference voltage error distribution current signal Eri replaces benchmark voltage error signal Ec and with the 1stGain setting signal G1r is input to amplitude center current setting circuit IHCR together.

In addition, reference voltage distribute time signal Ert together with the 2nd gain setting signal G2r by defeatedEnter to timer circuit TM.

By the reference amplitude center of the comparing current settings signal of amplitude center current settings signal IhcrThe upper limit of the recruitment of Ihcr0 is made as Ih1. Because recruitment in formula (1) is G1r* (Vr-Vcr), thus the predetermined upper limit threshold Tv1 of voltage difference (Vr-Vcr) by inferior formula (3)Represent.

Tv1＝Ih1/G1r…(3)

For example,, in the time that the 1st gain setting signal G1r is 10A/V, if establish the upper limit of recruitmentIh1 is 50A: Tv1 is 5V.

Reference voltage error signal distributor circuit DEC is using reference voltage error signal Ec as benchmarkVoltage error distributes current signal Eri to export, until reference voltage error signal Ec reachesTill limit threshold value Tv1. In this case, with embodiment 1 similarly, become based on formula (1)The more amplitude center of high level of current.

In addition, reference voltage error signal distributor circuit DEC is super at reference voltage error signal EcCross in upper limit threshold Tv1, believed upper limit threshold Tv1 as reference voltage error distribution electric currentNumber Eri exports, by (reference voltage error signal Ec-upper limit threshold Tv1) as benchmark electricityPress and distribute time signal Ert to export. In this case, the amplitude center of high level of current is becomeMore with the corresponding voltage of upper limit threshold Tv1. And, about the change that exceedes upper limit threshold Tv1Change amount, as illustrated in embodiment 2, only changes the 1st arc period Ta1 institute correspondingTime.

In addition, by the reference amplitude center of the comparing current settings of amplitude center current settings signal IhcrThe lower limit of the reduction that signal Ihcr0 reduces is made as Ih2. Because recruitment in formula (1) is G1r* (Vr-Vcr), so the predetermined lower threshold Tv2 of voltage difference (Vr-Vcr) is by inferiorFormula (4) represents.

Tv2＝Ih2/G1r…(4)

Reference voltage error signal distributor circuit DEC is using reference voltage error signal Ec as benchmarkVoltage error distributes current signal Eri to export, until under reference voltage error signal Ec reachesTill limit threshold value Tv2. In this case, with embodiment 1 similarly, become based on formula (1)The more amplitude center of high level of current.

In addition, reference voltage error signal distributor circuit DEC is little at reference voltage error signal EcIn lower threshold Tv2, using lower threshold Tv2 as reference voltage error distribution current signalEri exports, by (reference voltage error signal Ec-lower threshold Tv2) as reference voltageDistribute time signal Vrt to export. In this case, the amplitude center of high level of current is changedWith the corresponding voltage of lower threshold Tv2. And, about the variation lower than lower threshold Tv2Amount, as illustrated in embodiment 2, only changes the 1st arc period Ta1 correspondingTime.

In embodiment 3, be combined and used in enforcement side by the change degree that coordinates setting voltageThe increase and decrease of the amplitude center electric current I hcr of the high level of current illustrating in formula 1 and at embodiment 2The change of the 1st arc period Ta1 of middle explanation, thus prevent that electric arc from becoming unstable.

In addition, in embodiment 3, illustrated and in prescribed limit, made high level electricity in voltage differenceThe amplitude center electric current I hcr increase and decrease of stream makes the 1st in the situation that voltage difference is outside prescribed limitThe example that arc period Ta1 changes, but also can make amplitude center electric current I hcr and the 1st electric arc phaseBetween Ta1 change simultaneously.

[embodiment 4]

In embodiment 4, on the basis of the welding method illustrating in embodiment 1, pass throughBefore electric arc produces, detect the necking down of molten drop, thereby made electric current decline to alleviate before electric arc producesSplash.

Fig. 9 shows the block diagram of the formation of the welder 100C that embodiment 4 relates to. WithUnder explanation in, only explanation is different from the part of embodiment 1, about identical with embodiment 1Part is given identical not repeat specification of symbol.

With reference to Fig. 9, welder 100C comprises: power circuit 102A, power control 104C,Wire feed unit 106 and welding torch 4.

Power circuit 102A, in the formation of the power circuit 102 shown in Fig. 1, also comprises transistorTR2 and current-limiting resistor R. Transistor T R2 and reactor WL1 and WL2 are in series inserted intoThe output of electric power main circuit PM. The transistor T R2 current-limiting resistor R that is connected in parallel. Because power supplyThe formation of other parts of circuit 102A is identical with the power circuit of Fig. 1 102, so do not repeatBright.

Power control 104C, in the formation of the power control 104 shown in Fig. 1, also wrapsDraw together: necking down testing circuit ND, necking down detection reference value initialization circuit VTN and drive circuitDR. Because the formation of other parts of power control 104C and the power control of Fig. 1104 is identical, so not repeat specification.

Welding electricity when Figure 10 shows the welder being related to by embodiment 4 and weldsThe movement oscillogram of pressure, welding current and control signal.

The waveform difference of the waveform of Figure 10 and the embodiment of Fig. 21 is: at moment t1a,If detect, the necking down of molten drop makes welding current reduce, and produces electric arc at moment t2 afterwards.

Because being in proportion of the current value in the electric arc of splashing amount and moment t2 produces, soIf reduce in advance current value in electric arc generation, can reduce the generation of splashing.

With reference to Fig. 9, Figure 10, necking down detection reference value initialization circuit VTN exports predetermined contractingNeck detection reference value signal Vtn. Necking down testing circuit ND is by this necking down detection reference value signal VtnWith the weldingvoltage detection signal Vd illustrating in Fig. 1 and welding current detection signal Id conductInput, and the voltage rising value Δ V of output in during short circuit reaches necking down detection reference value signalThe time point (moment t1a) of the value of Vtn becomes high level, again produces and make weldingvoltage at electric arcThe value of detection signal Vd be time point (moment t2) more than electric arc discriminant value Vta become low level thisThe necking down detection signal Nd of sample. Therefore, this neck detection signal Nd becomes contracting during high levelTn between neck detection period.

In addition the differential value of the weldingvoltage detection signal Vd in, also can be during short circuit reach according toThe time point of the value of the necking down detection reference value signal Vtn that corresponding mode sets with it, makes necking down inspectionSurvey signal Nd and be varied to high level. And then, also can remove by the value of weldingvoltage detection signal VdCalculate the resistance value of molten drop with the value of welding current detection signal Id, and at the differential of this resistance valueValue reach the necking down detection reference value signal Vtn setting according to corresponding with it mode value timePoint, makes necking down detection signal Nd be varied to high level. Necking down detection signal Nd is input to power supplyMain circuit PM. Electric power main circuit PM stops output between necking down detection period in Tn.

Drive circuit DR output is that (non-necking down detects in low level at this necking down detection signal NdTime) make the driving signal Dr of transistor T R2 in conducting state. Because Tn between necking down detection periodInterior driving signal Dr is low level, so transistor T R2 is in cut-off state. Its result, current limlitingResistor R is inserted into the power circuit of welding current Iw (from electric power main circuit PM to welding torch 4Path). The value of this current-limiting resistor R is set to short circuit load (0.01～0.03 Ω degree)10 times of above large values (0.5～3 Ω degree). For this reason, the direct current reactor in the source of welding currentAnd the energy of accumulating in the reactor of cable is by deep discharge, as shown in moment t1a～t2 of Figure 10 thatSample, welding current Iw sharply reduces and becomes little current value.

At moment t2, if short circuit is disconnected, electric arc produces again, and weldingvoltage Vw becomes in advanceMore than definite electric arc discriminant value Vta. This situation detected, necking down detection signal Nd becomes low electricityFlat, drive signal Dr to become high level. Its result, transistor T R2 is in conducting state, afterBecome the control that utilizes the arc welding that Fig. 2 illustrated in embodiment 1. About the later the 1stArc period Ta1 and the 2nd arc period Ta2, because illustrated in Fig. 2, soNot repeat specification.

Because the welder that embodiment 4 relates to can reduce electric arc while again producing (moment t2)Electric arc current value while again producing, so the welder institute except illustrating in embodiment 1Outside the effect playing, can also further reduce electric arc and produce splashing while beginning.

In addition, in embodiment 4, as making welding current Iw rapidly detecting in necking downThe means that reduce, and the method that current-limiting resistor R is inserted into power circuit has been described. As removingMeans outside this, also can adopt following method: via switch element, Parallel-connected Capacitor is connected inBetween the lead-out terminal of welder, if necking down detected, make switch element in conducting state, byCapacitor energization discharge current, and welding current Iw is reduced rapidly.

[embodiment 5]

In embodiment 5, on the basis of the welding method illustrating in embodiment 2, pass throughBefore electric arc produces, detect the necking down of molten drop, thereby made electric current decline to alleviate before electric arc producesSplash.

Figure 11 shows the block diagram of the formation of the welder 100D that embodiment 5 relates to. ?In the following description, only explanation is different from the part of embodiment 2, about identical with embodiment 2Part give identical not repeat specification of symbol.

With reference to Figure 11, welder 100D comprises: power circuit 102A, power control 104D,Wire feed unit 106 and welding torch 4.

Power circuit 102A, in the formation of the power circuit 102 shown in Fig. 7, also comprises transistorTR2 and current-limiting resistor R. Transistor T R2 and reactor WL1 and WL2 are in series inserted intoThe output of electric power main circuit PM. The transistor T R2 current-limiting resistor R that is connected in parallel. Because power supplyThe formation of other parts of circuit 102A is identical with the power circuit of Fig. 7 102, so do not repeatBright.

Power control 104D is in the formation of the power control 104A shown in Fig. 7, alsoComprise: necking down testing circuit ND, necking down detection reference value initialization circuit VTN and drive circuitDR. Because the formation of other parts of power control 104C and the power control of Fig. 7104A is identical, so not repeat specification.

In addition, about detecting associated necking down testing circuit ND with necking down, necking down detection reference value is establishedDetermine the action separately of circuit VTN and drive circuit DR because in embodiment 4Through being illustrated, so not repeat specification.

Because the electric arc that the welder 100D of embodiment 5 also can reduce electric arc while again producingCurrent value while again generation, so play except the welder that illustrated in embodiment 2Outside effect, can also further reduce electric arc and produce splashing while beginning.

[embodiment 6]

In embodiment 6, on the basis of the welding method illustrating in embodiment 3, pass throughBefore electric arc produces, detect the necking down of molten drop, thereby made electric current decline to alleviate before electric arc producesSplash.

Figure 12 shows the block diagram of the formation of the welder 100E that embodiment 6 relates to. ?In the following description, only explanation is different from the part of embodiment 3, about identical with embodiment 3Part give identical not repeat specification of symbol.

With reference to Figure 12, welder 100E comprises: power circuit 102A, power control 104E,Wire feed unit 106 and welding torch 4.

Power circuit 102A, in the formation of the power circuit 102 shown in Fig. 8, also comprises transistorTR2 and current-limiting resistor R. Transistor T R2 and reactor WL1 and WL2 are in series inserted intoThe output of electric power main circuit PM. The transistor T R2 current-limiting resistor R that is connected in parallel. Because power supplyThe formation of other parts of circuit 102A is identical with the power circuit of Fig. 8 102, so do not repeatBright.

Power control 104E is in the formation of the power control 104B shown in Fig. 8, alsoComprise: necking down testing circuit ND, necking down detection reference value initialization circuit VTN and drive circuitDR. The power control 104B of the formation of other parts of power control 104C and Fig. 8Identical, so not repeat specification.

Because the electric arc that the welder 100E of embodiment 6 also can reduce electric arc while again producingCurrent value while again generation, so play except the welder that illustrated in embodiment 3Outside effect, can also further reduce electric arc and produce splashing while beginning.

In addition, in embodiment 6, illustrated and in prescribed limit, made high level electricity in voltage differenceThe amplitude center electric current I hcr increase and decrease of stream makes the 1st in the situation that voltage difference is outside prescribed limitThe example that arc period Ta1 changes, but also can make amplitude center electric current I hcr and the 1st electric arc phaseBetween Ta1 change simultaneously.

Finally, referring again to Fig. 1 etc., summarize embodiment 1～6.

The welder of embodiment 1～6 is to utilize carbon dioxide to be used in protective gas alsoAlternately the co3 gas arc welding of short-circuit condition and conditions at the arc connects method and welds repeatedlyThe welder connecing. Welder 100,100A～100E possess: power circuit 102,102A,Between welding torch 4 and mother metal 2, provide voltage; With power control 104,104A～104E,Control the voltage of power circuit 102,102A. Power control 104,104A～104E according toThe 1st arc period Ta1 output high level at the initial stage of ensuing arc period after during short circuitElectric current, the 2nd arc period Ta2 output in later stage of arc period with carried out constant voltage controlMode control power circuit 102, the 102A of arc current corresponding to weldingvoltage. Power supply control dressPut 104,104A～104E so according to the waveform of increase and decrease is repeatedly superimposed on amplitude center electric current withProduce mode control power circuit 102, the 102A of high level of current.

Power control 104,104C and then the electricity corresponding to welding current of embodiment 1,4Stream setting value calculates recommends magnitude of voltage (reference voltage V cr), according to recommending magnitude of voltage (benchmark electricityPress Vcr) and the voltage setting value Vr of weldingvoltage between voltage difference make amplitude center electric current I hcrIncrease and decrease.

Power control 104A, the 104D of embodiment 2,5 and then corresponding to welding currentCurrent setting value calculates recommends magnitude of voltage (reference voltage V cr), according to recommending magnitude of voltage (benchmarkVoltage Vcr) and the voltage setting value Vr of weldingvoltage between voltage difference make the 1st arc periodTa1 increase and decrease.

Power control 104B, the 104E of embodiment 3,6 and then corresponding to welding currentCurrent setting value calculates recommends magnitude of voltage (reference voltage V cr), is recommending magnitude of voltage (benchmark electricityPress Vcr) and the voltage setting value Vr of weldingvoltage between voltage difference in the 1st scope (upper limitBetween threshold value Th1 and lower threshold Th2) situation under, make electrocardio in amplitude according to voltage differenceStream increase and decrease, voltage difference in be different from the 1st scope the 2nd scope (be greater than upper limit threshold Th1,Or be less than lower threshold Th2) situation under, make the 1st arc period increase and decrease according to voltage difference.

Preferably, in welder 100,100A～100E, the waveform of increase and decrease is triangular wave repeatedlyOr sinusoidal wave.

Preferably, in welder 100C～100E, power control 104C～104E asWhat in Figure 10, illustrated is such, in the case of the necking down of molten drop being detected in during short circuit, carries outMake the necking down that short circuit current reduces detect control.

Should think: this disclosed embodiment is example in all respects, is not restricted. Scope of the present invention is not above-mentioned explanation, but is represented by claims, comprisesThe scope of claims and all changes in the scope that is equal to the meaning.

Claims

1. a welder, it is by using carbon dioxide as protective gas also alternatelyThe co3 gas arc welding of short-circuit condition and conditions at the arc connects method and welds repeatedly, whereinDescribed welder possesses:

Power circuit, it for providing voltage between welding torch and mother metal; With

Control part, it controls the voltage of described power circuit,

Described control part is according to the 1st electricity at the initial stage of ensuing arc period after during short circuitDuring arc, export high level of current, the 2nd arc period output in later stage of described arc period with enterPower supply electricity described in the mode control of the corresponding arc current of the weldingvoltage of constant voltage control of goingRoad,

Described control part is according to the waveform of increase and decrease is repeatedly superimposed on to amplitude center electric current with described in producingPower circuit described in the mode control of high level of current,

Described control part calculates recommendation magnitude of voltage corresponding to the current setting value of welding current, according to instituteState the voltage difference of recommending between magnitude of voltage and the voltage setting value of weldingvoltage and make described amplitude centerElectric current increase and decrease.

2. a welder, it is by using carbon dioxide as protective gas also alternatelyThe co3 gas arc welding of short-circuit condition and conditions at the arc connects method and welds repeatedly, whereinDescribed welder possesses:

Control part, it controls the voltage of described power circuit,

Described control part calculates recommendation magnitude of voltage corresponding to the current setting value of welding current, according to instituteState the voltage difference of recommending between magnitude of voltage and the voltage setting value of weldingvoltage and make described the 1st electric arcIncrease and decrease during this time.

3. a welder, it is by using carbon dioxide as protective gas also alternatelyThe co3 gas arc welding of short-circuit condition and conditions at the arc connects method and welds repeatedly, whereinDescribed welder possesses:

Control part, it controls the voltage of described power circuit,

Described control part is according to the 1st electricity at the initial stage of ensuing arc period after during short circuitDuring arc, export high level of current, the 2nd arc period output in later stage of described arc period with enterPower circuit described in the mode control of the arc current that the weldingvoltage of constant voltage control of going is corresponding,

Described control part calculates recommendation magnitude of voltage corresponding to the current setting value of welding current, describedRecommending the voltage difference between magnitude of voltage and the voltage setting value of weldingvoltage is in the situation of the 1st scope,Make the increase and decrease of described amplitude center electric current according to described voltage difference, in described voltage difference for described in being different fromIn the situation of the 2nd scope of the 1st scope, according to described voltage difference, described the 1st arc period is increasedSubtract, the 1st scope between upper limit threshold and lower threshold, the 2nd scope for be greater than upper limit threshold orBe less than the scope of lower threshold.

4. according to the welder described in claim 1～3 any one, wherein,

Described waveform is triangular wave or sine wave.

5. according to the welder described in claim 1～3 any one, wherein,

In the case of detecting in during described short circuit that the necking down of molten drop, described control part makes shortThe necking down that road electric current reduces detects to be controlled.