JPS58122178A - Arc welding method - Google Patents

Abstract

PURPOSE:To always keep a pointed shape of the tip of a wire, to start an arc satisfactorily, and to obtain a weld having a high quality, from the time of start, by stopping the arc by a variation of arc voltage, which accompanies breaking-away of a droplet. CONSTITUTION:When a signal of welding stop is outputted from a sequence circuit 11, a timing circuit 7 of welding stop outputs an output stopping signal to a controller, when a signal which does not synchronize with a pulse timing signal from the controller 3 is inputted from a voltage detector 6, that is to say, when a droplet has broken away from the tip of a wire. A transistor 2 becomes off, and welding is ended. Accordingly, when welding has ended, the tip of the wire has no molten metal at all times, becomes a pointed shape, and the following arc is started very well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulsed arc welding method using a consumable electrode in an inert gas such as argon or helium, or a mixture of oxygen, carbon dioxide, etc. with an inert gas.

Generally, in this type of welding method, as shown in Figure 1, the phenomenon in which the welding wire melts into droplets and transfers to the base metal changes discontinuously after a certain current value. . This current value is called a critical current, and below the critical current value, the droplets become large lumps larger than the wire diameter and move irregularly. On the other hand, when the current exceeds the critical current, the droplets become smaller in diameter and the spray transfer becomes relatively stable. Therefore, in order to perform stable welding, it is necessary to weld at a current higher than the critical current, but if the workpiece to be welded is a relatively thin plate, excessive heat input is required, making it impossible to obtain a satisfactory welded workpiece. It is. For this reason, it is shown in Figure 2. A method in which a pulse current is superimposed on the base current has been used.

In this method, by setting the base electric current 1 below the critical current and setting the peak current It above the critical current, the transfer of the droplet is made smooth, and the average current is lowered to reduce the amount of heat input to the workpiece. The aim is to obtain a good welded joint.

However, attempts have been made to achieve a smooth arc start using methods such as passing a high current for a certain period of time and gradually increasing the feed speed of the ike wire to a set value, but none of these methods are sufficient. Satisfactory results have not been obtained. This means that the state of the wire tip at the end of welding is
This is due to the large effect it has on arc starting characteristics.

In other words, the droplet at the tip of the wire separates just before the end of welding,
If welding is completed in the shape shown in Figure 3(a), 1
The next arc start was very smooth.

The arc quickly changes to a stable one, but if it ends in the shape shown in Figure 3 (b), it is difficult to start the arc, and when observed with a high-speed camera, most of the cases.

The arc starts after fusing occurs between the power supply tip and the base metal.

With the conventional pulse arc welding method, whether the result is as shown in Figure 3 (1) or as shown in Figure 3 (1) is purely coincidental, and the disadvantage is that a stable arc start is not always achieved. was there.

The present invention has been made in view of the above-mentioned matters.

In the pulsed arc welding method, which uses a consumable electrode to weld in an inert gas or a shielding gas mixed with oxygen, carbon dioxide, etc., the shape of the wire tip at the end of welding is always shown in Figure 3 (1). ), and the purpose is to provide a pulse arc welding method that allows stable arc starting at all times.

Embodiments of the present invention will be described below with reference to FIGS. 4 to 9.

Figure 4 is a simulation diagram of the pulse current waveform, where %IP is the peak current, TP is the peak current time sIs is the base current, and T
m is the pace current time and k is the average current.

At this time, the average current can be expressed by the following formula.

The influence of pulse current factors IP, TP, Il, and TI on droplet transfer will be described below.

Figure 5 shows the relationship between the peak current Ip and the peak current time TP to ensure the transfer of 11 droplets in one pulse, which was determined from observations of arc phenomena taken with a high-speed cine camera and a camera. . What controls droplet transfer is the peak current and peak current time, and in order to ensure that one droplet transfers with one pulse, the peak current Ip and peak current time TP must be set to h-・TP. It is necessary to set the relationship such that =C. C at this time is a constant determined by the wire diameter and wire material. Also, K is the wire diameter.

1, 9 to 2 with almost no change depending on the material. ．． It can take a value of 5. In the figure, the human region lacks energy, and the droplet does not transfer reliably with one pulse, and in the worst case,
Region B, where the droplet diameter is 2 to 4 times the wire diameter, is a condition of excessive input, where several droplets are transferred in one pulse, and the tip of the welding wire becomes candy-like, causing a whiplash phenomenon. This is a region where the arc becomes unstable, exhibiting aspects similar to . C
The area of! This is an appropriate area where one droplet can be reliably transferred with a pulse. Based on this relationship, FIG. 6 shows the welding current and welding voltage V when welding is performed under appropriate conditions.

When the droplet detaches and migrates, the arc length momentarily increases, which causes the arc voltage to rise.

It is possible to establish when the droplets migrated. Figure 7 shows the droplet transfer form observed by observing the arc phenomenon.
It matches well with the waveform in the figure. In addition, the tip of the wire immediately after the droplet detaches (frame number 11) has almost no molten metal and has a relatively sharp shape, but just before the droplet detaches (frame number 4)
In 2), the molten metal that has grown at the tip of the wire hangs down, and if welding is finished in this state, the above-mentioned figure 3 (b)
), it will be difficult to start the arc.

From the results described above, the primary arc start can be performed stably by always ending welding immediately after the droplets have separated.

An embodiment for achieving the purpose of the method of the present invention is shown in FIG.

In Fig. 8, 1 is a rectifier, 2 is a transistor, 3 is a controller, 4 is a signal setting device, 5 is a current detector, 6 is an arc voltage detector, 7 is an output stop timing circuit, 8
10 is a welding wire, 9 objects to be welded, 10 is a wire feed motor, and 11 is a sequence circuit. In the circuit configured as shown in Fig. 8, 1. Normally, the waveform output by the transistor 2 is fed back to the current detector 5 and the voltage detector 6, differentially amplified to a predetermined value, and output controlled. are doing. On the other hand, the signal obtained by the voltage detector is passed through a filter such as a differential circuit, and the timing when the voltage suddenly changes is outputted to the timing circuit 7. The timing circuit 7 also receives a timing signal at the end of welding from the sequence circuit 11 and a timing signal for outputting a pulse current from the controller 3.

Now, when the sequence circuit 11 outputs the welding end timing signal to the timing circuit 7, the voltage detector 6 does not synchronize with the timing of the pulse current from the controller 3.
When a signal is input from the transistor 2, all signals to the transistor 2 are stopped, the transistor 2 is turned off, and the arc is cut. FIG. 9 shows the timing of this operation.

Since the signal (1) from the voltage detector 6 is output only for rapid voltage changes, the voltage changes accompanying the rise and fall of the pulse current and detachment of the droplet are output.

When the pulse voltage is output from the controller 3, the signal ① is outputted. Therefore, the signals from the voltage detector 6 and the controller 3 match when the pulse is output.

Here, the welding stop signal (II
) is output, the welding stop timing circuit 7 receives a signal that is not synchronized with the pulse timing signal from the controller 3 from the voltage detector 6, and at 9 o'clock, that is, when the droplet detaches from the tip of the wire, the welding stop timing circuit 7 starts the welding stop timing circuit 7. Outputs an output stop signal to and turns off transistor 2 (IV)
and finish welding. Therefore, whenever welding is finished, the tip of the wire is free of molten metal and has a sharp shape, making it possible to perform the primary arc start very well. It is possible to maintain high quality.

As explained above, according to the present invention, the tip of the wire is always kept in a sharp shape when welding is finished, so the next arc start is very good, and as a result, the spatter at the start is reduced, □High quality welds can be obtained from the start.

[Brief explanation of the drawing]

Figure 1 is a basic explanatory diagram of the gas shielded arc welding method, Figure 2
The figure is an explanatory diagram of the conventional pulse arc welding method. 3-4 are explanatory diagrams, FIGS. 5-7 are basic conceptual diagrams of the present invention, FIG. 8 is an embodiment of the method of the present invention, and FIG. 9 is an explanatory diagram of the operation of FIG. 8. DESCRIPTION OF SYMBOLS 1... Rectifier, 2... Transistor, 3... Controller, 4... Signal setting device, 6... Arc voltage detector, 7... Output stop timing circuit. 1st diagram den Nu U (A) vine 2 fig. ¥i 3 fig. (phantom (b) 24 Figure 7 Compassion 1

Claims (1)

[Claims] Peak current value in pulse waveform■? In a pulsed arc welding method using a consumable electrode, in which the peak current time and the peak current time Ty are kept almost constant, the average output is adjusted by changing the pulse frequency, and the arc voltage changes as the droplet detaches, the arc is stopped. A pulsed arc welding method characterized by nine advantages.