JPH0352769A - Method and equipment for ac arc welding for consumable electrode gas shielded arc welding - Google Patents

Abstract

PURPOSE:To prevent unsteadiness and running out of an arc by maintaining constant an output level of a period to make an electrode plus and minus and impressing AC electric power to make short and long a period to make the electrode minus according to variation of the electrode feed quantity on between the electrode and base metals. CONSTITUTION:Prior to welding, current values IEP and IEN, and the period TEP are set by current setters 13 and 14, and a period TEP setter 9, respectively. In addition, a voltage value V and the feed quantity of a wire 20 are set by a voltage setter 18 and a wire feed quantity setter 24, respectively. At the time of welding, the arc then becomes straight in both periods of the period TEP and the period TEN. In addition, when the arc length is extended, namely, when an output terminal voltage value of an output side inverter 8 detected by a voltage detection circuit 17 becomes higher than the voltage value set by the voltage setter 18, the period TEP is made longer than the set period TEN and the melting quantity of the wire is reduced and the arc length is returned to its origin with a comparator 19. In addition, since the period TEN is shorten when the arc length is short, the arc length is maintained constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to alternating current arc welding, and particularly to a welding method and apparatus K suitable for consumable electrode type gas-shielded arc welding.

[Conventional technology]

For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 56-165564, the average welding current value is changed by adding an electrode (hereinafter referred to as a wire) as the polarity and changing the minor current period of the base material. . As a result, the droplets forming at the tip of the wire could be moved to the molten pool in synchronization with the peak current period, making it possible to weld with less spatter.

Furthermore, in order to further improve the stability of the arc when the average welding current value is small, Japanese Patent Application Laid-Open No. 59-150672 discloses that a first pulse current is used to move droplets from the tip of the wire. At the same time, the second
The pulsed current prevents the wire from seizing on the power supply tip caused by the first pulsed current.
This prevents the occurrence of arc breaks that degrade the quality of welded parts.

[Problem to be solved by the invention]

When welding with so-called reverse polarity, where the wire is positive and the base metal is negative, when the welding current value is increased, a cathode spot is formed on the surface of the base material almost directly below the tip of the wire, and the arc becomes almost straight. If you reduce the welding current value,
Since the cathode spot moves over a wide range on the base metal surface, the arc also wanders on the base metal surface. If the arc length increases excessively, the arc will be completely extinguished.

For this reason, in the former technique described above, the average welding current value cannot be reduced by a small amount, and even in the latter technique, it is not possible to sufficiently prevent harmful arc breakage that occurs when the button is pressed in the small current range. Ta.

The purpose of the present invention is to prevent arc fluctuation and harmful arc breakage in the small current range, and to prevent welding operations. Another object of the present invention is to provide an AC arc welding method and apparatus for consumable electrode type gas-shielded arc welding that can improve the quality of welded parts.

[Means to solve the problem]

The above problem can be solved by applying AC output between the wire and the base material to make the wire positive, as shown in Figure 1, which is an example of the output characteristics of the consumable electrode type gas shielded arc welding method of the present invention. The period TIF and the critical current value of the wire as the output level during this period TmpK> A large current value I
MF and the critical current value as the output level during which the wire is negative (TmyK&).The current value Ir+ is also small.
This can be solved by keeping the three conditions n constant and making the period TIN shorter/longer depending on the increase/decrease in the amount of fire feed.

[For production]

Period Tl during which current value I111F is large! Spending too much time on IP
As a result of the cathode spot being formed on the base material approximately directly below the wire tip, the arc is approximately straight. Also, the period 'l'. N.K.
>, the current value INN is small, but as a result of the cathode point being formed at the tip of the wire, the arc is also almost straight, so arc wandering and harmful arc breakage do not occur.

In addition, by changing the period TIN, the average welding current value also changes, and the droplet formed at the tip of the wire changes during the period T1II.
1? move to the molten pool in synchronization with

〔Example〕

FIG. 2 is a diagram of a first embodiment of a welding device for realizing the output characteristics shown in FIG. 1.

In the figure, numeral 3 indicates an input rectifier that rectifies commercial frequency alternating current into direct current. 2 is a pulse width control circuit that controls the pulse width of the component current using a MOS-FET. 4 is a welding transformer, the input side of which is connected to the input side inverter. Reference numeral 5 denotes an output rectifier connected to the output side of the welding transformer 4, which converts the high frequency alternating current into direct current again. 6 is a DC reactor for smoothing the DC output rectified by the output rectifier 5; 7 is a current detector. 8 is for performing AC welding, and 7 is an output-side imperter for converting DC back into AC. The output side inverter 8 is a rectangular wave generator 11 set by a period T/IIP setter 9 and a period Tma setter 10.
Based on the signals from the drive circuit 12, the drive circuit 12 is controlled as follows.

13 and 14 are current setting devices, which set the current value Impj? output from the output side inverter 8. and current value IBM. 15 is a changeover switch, and the square wave generator 1
1, the current setter 13 and the period TRm' setter 9 are connected to the TFC current setter 14 and the period TIN setter 1.
0 are synchronized with each other, the current setters 13 and 1
4 is connected to the pulse width control circuit 3 via the error amplifier 16.

A current detector 7 is connected to the error amplifier 16, and during welding, the error amplifier 16 uses the current value υ detected by the current detector 7 and the current value υ set by the current setting devices 13 and 14. The error amplifier 16 compares the current value ImpxImy with the output side inverter 8 so that the average value of the current values flowing through the current detector 7 becomes the current value corresponding to the current value ImpzIr+n.
The pulse width control circuit 3 is controlled so that the output characteristics of the pulse width control circuit 3 have constant current characteristics.

17 is a voltage detection circuit connected to the output side terminal of the output side inverter 8; 18 is a voltage setting device for setting the voltage value when welding, and the period TIN is
It is connected to the setting device 10. And voltage setting device 18
When the voltage value V is set by , the period TIII corresponding to the set voltage value V is set in the period TIM setter 10 . As shown in FIG. 3, the period Tin changes with respect to the voltage value V in a four-exponential manner.

A comparator 19 compares the detection value detected by the voltage detection circuit 17 and the set voltage value V during welding, and controls the period TIN setting device 10 so that the two match.

20 is a wire. 21 is a roller that feeds the wire 20; 2
2 is a motor, which is controlled by a motor control circuit 23.

24 is a wire feed rate setting device connected to the motor control circuit 23; 25 is a base material.

Figures m4 to 5 show the voltage detection circuit 17 described above.
This shows an example, and the fourth example shows an example in which the voltage VIIIP%VIll between the wire 20 and the base material 25 during the period Tip%1I is individually detected based on the peak charging waveform of the capacitor. Further, FIG. 5 shows an example of detecting the average value of the voltage Vmp%v]llM.

The operation will be explained below. Prior to welding, the current setting devices 13 and 14 and the period T
The setter 9 sets the % current value ImpqImx and the period Ti.
Determine P. In addition, the voltage setting device 18 sets JIJ [pressure value V
(As mentioned above, the period TInN is also determined at the same time),
The feed amount of the wire 20 is set by the wire feed amount setting device 24.

During welding, a droplet formed at the tip of the wire 20 is transferred to the molten pool in synchronization with the period TIF, and during the period TlwK&, the arc is maintained and the droplet is slightly shaped. and,
No matter which period it falls in, the arc will be almost straight.

Further, for example, when the arc length increases, that is, when the output terminal voltage value of the output side inverter 8 detected by the voltage detection circuit 17 becomes larger than the voltage value set in the voltage setting device 18, the comparator 19 is activated. When the arc length becomes shorter, the period TIN is shortened, so that the arc length is kept constant.

Table 1 shows L. Using 211EIIIφ metal flux cored wire, Ar gas 80% was used as shielding gas.
This is an example of AC welding with φ+COz gas of 20'%.

Table 1: By keeping the current Ir+psImM$P and the period TIIIP constant and changing the period TmN according to the wire feed rate, good results could be obtained at any wire feed rate.

11 In this embodiment, one voltage setting device 18 is used, but for example, a voltage detection circuit 17 shown in FIG. They may be combined with the setting device 18 to set the respective voltages.

Furthermore, the control target for keeping the output terminal voltage constant is not limited to the period Tlllli, but the period TInP1
Similar effects can be achieved by controlling either the peek current Imp or the current INN. Furthermore, when detecting both voltages V B P s V M N,
For example, if the voltage VIP is the period TIIiN, the voltage ■BM
The current Imp may also be controlled by.

FIG. 6 is a diagram showing a second embodiment of the welding device according to the present invention. Items that are the same as the younger brother 2 are given the same reference numerals.

In the same figure, 31 and 32 are voltage setting devices, and the voltage value Vi+p & which the output side inverter 8 outputs and the changeover switch 15 are set to 1 voltage setting device 31 and period T1cp setting device according to the signal from the rectangular wave generator 11. 9 is also the voltage setting device 3
The voltage setters 31 and 32 are connected to the pulse width control circuit 3 so that the voltage setter 2 and the period TIIIN setter 10 are synchronized with each other. That is, the output characteristic of the output side inverter 8 is a constant voltage characteristic.

Further, the wire feed amount setting device 24 is connected to the period TIN setting device 10.
When connected to >B and the wire feed rate is set, the period Tin changes approximately exponentially, as shown in FIG.

The operation will be explained below.

Prior to welding, voltage setting devices 31, 32 and period TIF
The voltage value VIP%VIN% period Tmp> and the wire feeding amount are determined by the setting device 9 and the wire feeding amount setting device 24. Among them, as described above, the period TIIIN is also set by setting the wire feeding amount.

During welding, the droplet formed at the tip of the wire 20 is transferred to the molten pool in synchronization with the period TIF, and during the period TiN, the arc is maintained and the droplet is slightly shaped. Also, the arc becomes almost straight.

Further, since the output characteristic of the output side inverter 8 is a constant voltage characteristic, the arc length becomes almost constant due to the self-control action of the arc length due to the power supply characteristics.

Table 2 shows 0. 9 Using wILti3 mild steel solid wire, 80% Ar gas + COz as shielding gas
This is an example of AC welding using 20% gas.

Table 2 Voltage V I p, V yn w I was able to get it.

In this embodiment, the wire feed setting device 24 and the period TIc)i setting device 10 are connected so that the value of the period TEN changes in conjunction with the wire feeding amount setting value. However, it goes without saying that, for example, the relationships shown in FIG. 6 may be prepared as a data sheet and set individually.

FIG. 8 is a diagram showing a third embodiment of the welding device according to the present invention. Among them, the same parts as in FIG. 2 are given the same reference numerals.

In the figure, 35 is a current setting device that sets the current value Id output by the output side inverter 8. In addition,
As shown in Figures 9 and 10, the current value Id is a value that gradually decreases from the current value I'Ep or a value that is smaller than the current value IEP (however, the wire is positive in both cases), and the period Td setting device The time period Td set at 36 continues.

Reference numeral 37 denotes a changeover switch, which, depending on the signal from the square wave generator 11, switches the current setter 13 and the period Tgp setter 9, the current setter 35 and the period Td setter 36, and the current setter 14 and the period TEN setter. 10 are synchronized with each other.

The operation will be explained below.

Prior to welding, the current value Izp+Id+IIDNν and the working period Txp+Td6 are determined using the current setting device 13, 35, 14 $1-, the period TEP setting device 9, and the period Td setting device 36. Further, the voltage setting device 18K sets the choir voltage value (2) and the wire feeding amount setting device 24 sets the wire feeding amount.

Since the operation during welding is almost the same as that of the first embodiment, only the differences from the first embodiment will be explained. That is, in the third embodiment, arc noise is reduced, arc stability is further improved, and welding workability is improved.

Table 3 shows that using a mild steel solid wire with a diameter of 0.9,
This is an example of MIG AC welding using Ar gas as a shielding gas of 100%. Good results were obtained in the same manner as in Tables 1 and 2 above. As shown, the output level setter 51, the wire feeding amount according to the setting value, and the output voltage v1 period TEN
By providing a function generator 52 that commands the set value of , it becomes possible to uniformly set the welding conditions.

In addition, in this third embodiment, the current value Id is changed in a slope-like or step-like manner, but even if the above-mentioned second embodiment is changed, the period Td setting device and the voltage for setting the voltage in the period Td can be changed. A similar effect can be obtained by adding a setting device and changing the voltage value in a slope or stepwise manner.

Furthermore, regarding the above-mentioned first to third embodiments,
Although the output characteristics of the output side inverter 8 are based on constant current or constant voltage characteristics, for example, if the EP period is made into constant voltage characteristics,
The EN period may have constant current characteristics.

〔Effect of the invention〕

As described in detail above, according to the present invention, the period in which the wire is turned on in consumable electrode type gas shielded arc welding and the output level button 4 during that period. Since the output level k is constant during the period in which the wire is made negative and the period in which the wire is made negative, and the alternating current output is applied between the wire and the base material, the period in which the wire is made negative is shortened or lengthened depending on the increase/decrease in the wire feeding amount. Welding is possible up to a small current range, and droplets formed at the tip of the wire can be transferred to the molten area in synchronization with the period when the wire is turned positive. Furthermore, even when applied to a small current range, harmful arc breakage and arc fluctuations do not occur.

Therefore, there is an effect that the welding workability and the quality of the welded part can be improved.

[Brief explanation of drawings]

FIG. 1 shows an example of the output characteristics of the consumable electrode type gas-shielded arc welding method according to the present invention. FIG. 2 is a diagram of a first embodiment of the welding device. Figure 3 shows the voltage value V and period TE that can be pressed in the first embodiment.
A diagram showing the relationship with N. FIG. 4 and FIG. 5 are examples of the voltage detection circuit in the first embodiment. FIG. 6 is a diagram showing a second embodiment of the welding device. FIG. 7 is a diagram showing the relationship between the fire feed amount and the period TIN in the second embodiment. Figure 8 shows the third welding device.
Example diagram. FIGS. 9 and 10 are explanatory diagrams of characteristics in the third embodiment. 1...Input side rectifier, 2...M08-
FET. 3...Pulse width control circuit, 4...
Welding transformer, 5... Output side rectifier, 7... Current detector, 8... Output side imperter, 9... Period Tip setting device, 10゜゜゜ period TICN setting device, 1
3,14.35...Current setting device, 15...Selector switch, 16...WA difference amplifier, 17...Voltage detection circuit, 18,31.32...Boat pressure setting device,
19... Comparator, 20... Wire, 24...
・Wire feed setting device, 25...Base material, 36...
Period Td setter.

Claims (1)

[Claims] 1. The output level during the period when the electrode is positive, the output level during the period when the electrode is negative, and the output level during the period when the electrode is negative are constant, and the electrode An alternating current arc welding method in consumable electrode type gas shielded arc welding, characterized by applying an alternating current output between an electrode and a base material for short/long periods of time in which the negative value is negative. 2. The period in which the electrode is made positive consists of a period in which the output level is kept constant, and a period in which the output level is lower than the output level, which is continuous with this period. The AC arc welding method in consumable electrode type gas shielded arc welding according to item 1. 3. Determine the value of the output terminal voltage or arc voltage in advance, measure the output terminal voltage or arc voltage during welding, and set the electrode to a positive or An alternating current arc welding method in consumable electrode type gas shielded arc welding, characterized by increasing or decreasing at least one of the current value during a period in which the current value is negative or a period in which the electrode is positive or negative. 4. A DC power supply, at least two output setting means for setting a DC output level, and a control means connected to the output setting means for controlling the DC power supply according to a set value of the output setting means;
It is characterized by comprising a conversion means for converting DC output into AC output, and a period setting means connected to the conversion means and setting an electrode positive period and an electrode negative period, and the period setting means and the output setting means are synchronized. AC arc welding equipment for consumable electrode type gas shielded arc welding. 5. The AC in consumable electrode type gas shielded arc welding according to claim 4, wherein the output setting means for the DC output level is a voltage setting means, and the output characteristic of the DC power supply is a constant voltage characteristic. Arc welding equipment. 6. The output setting means for the DC output level is a current setting means, the output characteristics of the DC power supply are constant current characteristics, and
5. The AC arc welding apparatus for consumable electrode type gas shielded arc welding according to claim 4, further comprising means for keeping the value of the output terminal voltage or arc voltage constant. 7. The AC arc welding device for consumable electrode type gas shielded arc welding according to claim 4, characterized in that the output characteristics of the DC power source are different between the electrode positive period and the electrode negative period. 8. Claims 4 to 7, characterized in that at least two of the electrode feeding amount, the output terminal voltage, or the negative electrode period are linked with the output setting means for the DC output level. AC arc welding equipment for consumable electrode type gas shielded arc welding according to any one of the above.