JPS58141858A - Pulse arc welding method - Google Patents

Abstract

PURPOSE:To perform welding of high workability and high welding quality, by controlling a titled method so that an output in base period of pulse current becomes constant-voltage characteristics and an output in peak period of pulse current becomes constant-current characteristics, respectively. CONSTITUTION:A peak signal generating circuit 13 compares a current value determined by a peak current setting device 14 and a current value measured by a current measuring device 8 and extracted by a peak current detector 12, and generates a peak signal so as to allow the two to coincide with each other. A base signal generating circuit 16 compares a voltage value determined by a base voltage setting device 15 and a voltage value extracted by a base voltage detector 17 by measurement of output voltage and generates a base signal to make the two coincide with each other. By the above way, the output in base period becomes constant-voltage characteristics and that in peak period becomes constant-current characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses consumable electrodes/? The present invention relates to a lus arc welding method.

FIG. 1 is a diagram showing an example of pulsed current used in pulsed arc welding, where Ip is the peak current,
tp is the peak period, IB is the pace current, and t
l indicates the pace period.

The average output current Im of this pulse current is controlled by adjusting the pulse period T'.

FIG. 2 is a characteristic diagram in which both the peak period and the pace period of the All soot flow have constant voltage characteristics as described above.

In the same figure, P shows an increase in arc length (especially during the peak period).
When Ll) is decreased (L,), the output voltage hardly changes, but the peak current Ip and pace current I greatly increase or decrease. Even if the pace current In changes somewhat, it does not greatly affect the 1W contact. However, when the peak current Ip decreases, the peak current rp becomes thicker (acts on droplet detachment), so
The pinch rate decreases, and droplet detachment becomes unstable.There are cases where the droplet detachment is not performed in synchronization with the pl peak period, and the arc becomes unstable. On the other hand, if the peak current Ip increases, the wire melts and separates beyond the appropriate value, and the amount of change in current and voltage when transitioning from the peak period to the pace period becomes large (which may cause arc breakage). .

FIG. 3 is a characteristic diagram when the peak period is a constant voltage characteristic and the 4-phase period is a constant current characteristic, and the peak period has a voltage similar to that in FIG. 2. During the pace period, if a disturbance occurs, the pace current IB hardly changes, but the arc length increases (changes).If the average output current is large and the base period is short (the peak period is long)
fi, the output voltage hardly changes because the pace period ratio is small. However, as the average output current Im becomes smaller, the ratio of the pace period becomes larger and the change in output voltage also becomes larger. Therefore, in order to keep the output voltage constant, some kind of compensation must be performed.

Figure 4 shows the constant current characteristics for both the peak period and the pace period, and the average output current I in Figure 3.
Just as when n is a small current, some compensation will be required to keep the output voltage constant.

The present invention was made in view of the drawbacks of the prior art,
It is an object of the present invention to provide a pulse arc welding method that eliminates the above-mentioned drawbacks.

In the constant arc welding method of the present invention, the output during the pace period of the pulse current is controlled to be a constant voltage %, and the output during the peak period of the pulse current is controlled so as to have constant current characteristics. It is a feature.

The present invention will be explained in more detail below with reference to the accompanying drawings.

FIG. 5 is a characteristic diagram when the peak period has a constant current characteristic and the pace period has a constant voltage characteristic according to the present invention.

As is clear from FIG. 5, even if the arc length changes during the peak period, the peak current Ip hardly changes, and the droplets melted and detached by the peak current Ip are always kept constant. As the arc length changes during the pace period, the base current! B
changes greatly, but the output voltage hardly changes.

That is, in the constant voltage characteristic during the pace period, the pace current IB changes significantly due to a change in the output voltage caused by a slight change in the arc length. As a result, - When the arc length increases, the pace current IB decreases, so the amount of wire melting also decreases, and the arc length also decreases, returning to the original arc length. When the arc length becomes short, the pace current IB increases, the amount of wire melting increases, the arc length also increases, and the arc length returns to its original value. This is called arc length self-control. During the peak period, the constant current characteristic is
Since there is almost no change in the I peak current Ip, no self-control effect on the arc length occurs.

Therefore, according to the pulsed arc welding method of the present invention, when the average output current is small, the Noculus period is 5 long and the 6th
The waveform will be as shown in the figure. That is, the ratio of the pace period tB to the pulse period T is extremely large, and the arc state is almost equal to the pace period 1. is dominated by the power supply characteristics (constant voltage characteristics). Therefore, even without compensation for arc length variations, the arc length 10 is kept approximately constant due to the self-control action of the arc. For example, with mild steel φ1.2 wire, Ip=40
OA, Xp==40A, tp=: 4.2ms
If In =: 1. OOA (average output current) is T120m5, so ta/T = (20-4,2
) /20 = 0.79, and it can be seen that it is dominated by the power supply characteristic 15 of the pace period.

When the average output current is large, the pulse period T becomes shorter, tm/T decreases, and tp/T increases. Therefore, the arc state is dominated by the power supply characteristics (constant current characteristics) during the peak period 1p. In particular, when the average output current exceeds a certain value, the pace period tM appears to have an angular value as shown in FIG. 7, and the waveform becomes just as long as the peak period tp. For example, welding of the aforementioned mild steel φ1.2 wire (Ip =
40OA, IB=40A, tp=1.2
m5), then I! II = 30OA and 4ms in T or 5, so tn/T = (4-4,2)/4 =
-0.05, tp/T: 4.2/4: 1.05. In such a case, the peak period t
It will be dominated by the power supply characteristics of p. Therefore, it is dominated by constant current characteristics, and the peak current rarely changes due to disturbances.

Generally, in a small current range where the average output current is small, the pace period of small current and low voltage is long, so when the arc length changes, work efficiency decreases. In addition, only the pace period requires less energy (welding is carried out at 15 @f), and arc breakage or short circuits must not occur during the base period. For this reason, it is necessary to keep the arc length V constant.

In the large current region of the average output current, the proportion of peak periods with high energy is large, so that even if the arc length changes somewhat, it will not impede workability. However, when the current changes, the penetration FL between the base metal BM and the welding bead WB changes as shown in FIG. 8, which may cause welding defects such as poor fusion. In particular, in the case of AI welding, this tendency is remarkable because the melting point is low (easily affected by the current value).

Therefore, according to the method of the present invention, there is no constant voltage characteristic in the small current region, and constant current characteristic in the large current region. This enables welding with excellent properties and welding quality.

FIG. 9 is a block diagram showing an example of a welding machine implementing the pulse arc welding method of the present invention. In the figure, l is a rectifier, 2 is a transistor that controls the peak period and pace period, 3 is a flywheel diode, 4 is a smoothing reactor, and 5 is a feed roller 6 driven by a wire feed control circuit 18. This is a welding wire supplied for welding the material 7. 9 is a transistor control circuit that controls the conduction time of the transistor 2 according to the peak period 1 or the pace period; 1] is a pulse frequency setting device 1;
According to the peak period/pace period set at 0, the signal from the peak generation circuit 13 and the pace signal generation circuit 16
This is a peak/pace selector switch that changes the signal from.

The peak signal generation circuit 13 compares the current value determined by the peak current setting device 14 with the current value measured by the current measuring device 8 and extracted by the peak current detector 12,
A peak signal is generated so that both coincide. The pace signal generation circuit 16 compares the voltage value determined by the pace voltage setter 15 with the voltage value extracted by the pace voltage detector 17 by measuring the output voltage, and generates a pace signal so that the two match. let By doing the above, it becomes possible to set the pace period to have constant voltage characteristics and the peak period to have constant current characteristics.

As is clear from the above description, according to the present invention, the arc length can be kept constant and good welding results can be obtained in a low current range without using arc length control means. Further, the amount of weld penetration can be kept constant in the large current range, and a good welding result without defects such as poor fusion can be obtained. Furthermore, there is no need for a control circuit that compensates for arc length against disturbances.
This has the effect of simplifying the control circuit.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the /4' Luss current used in pulsed arc welding, Fig. 2 is a characteristic diagram when both the peak period and pace period of the td No. 4' Luss current are set to constant voltage characteristics, and Fig. 3 is A characteristic diagram when the pulse current peak period is a constant voltage characteristic and a pace period is a constant current characteristic. Figure 4 is a characteristic diagram when both the bus pulse current peak period and pace period are constant current characteristics. Fig. 5 is a characteristic diagram when the peak period of the pulse current is made into a constant current characteristic and the pace period is made into a constant voltage characteristic according to the present invention. Figure 7 is a diagram showing the nozzle current during high current welding, the eighth factor is a diagram showing an example of the penetration shape during high current welding, and Figure 9 is a diagram showing an example of a welding machine that implements the method of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Rectifier, 4... Smoothing reactor, 5... Welding wire, 6... Feeding roller, 7... Base material, 8...
Current detector, 19...Transistor control circuit, 10.
... Arm frequency setter, 11... Peak/pace selector switch, 12... Peak current detector, 13...
・Peak signal generation circuit, 14...Peak current setting device,
15... Pace voltage setting device, 16... Pace signal generation circuit, 17... Pace voltage detector, 18... Wire feeding control circuit. Representative Patent Attorney Tadashi Akimoto Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] In pulsed arc welding, in which a consumable electrode is fed at a constant speed for welding, the output during the pace period of the pulse current is controlled to have constant voltage characteristics, and the output during the peak period of the arm current is controlled to have constant current characteristics. A pulsed arc welding method characterized by controlled control.