JPS6356029B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulsed arc welding method, particularly a welding method using a direct current arc, in which a pulsed current is periodically applied to the welding current to make the molten metal formed at the end of the welding electrode into fine particles. The present invention relates to a pulsed arc welding method in which the pulsed arc is transferred to the welding base metal side.

Conventionally, the average current of welding current is low, but
Arc welding is widely practiced, in which the current is increased in pulses in response to the formation of a molten mass at the end of a welding electrode wire, and the droplets are spray-transferred.

FIG. 1 shows an example of a pulse arc welding device used for this type of arc welding method. Reference numeral 10 denotes an average current supply circuit for supplying an average DC current to the welding current, and is composed of a welding transformer 12 and a rectifier circuit 14. 16 is a pulse current supply circuit for supplying a pulse current to the welding current, and is composed of a welding transformer 18 and a rectifier circuit 20 including a phase control element. Since thyristors are usually used in the rectifying circuit 20 of the pulse current supply circuit 16, a single-phase wave rectifying circuit using a thyristor as the rectifying element of the rectifying circuit 20 will be described below as an example.

The output terminal of the average current supply circuit 10 and the output terminal of the pulse current supply circuit 16 are connected in parallel so that their respective polarities match, and a positive output terminal 22 and a negative output terminal 24 of the welding power supply device are connected. and is connected to.

A wire 26 constitutes a welding electrode, and the wire 26 and the positive output terminal 22 of the welding power source are connected by a welding current supply cable 28.

30 is a base material to be welded; the base material to be welded 30;
Similarly, a welding current supply cable 32 is connected to the negative output terminal 24 of the welding power source.

With the above structure, the average current supply circuit 10 of the welding power supply supplies an average DC current to the output ends 22 and 24 of the welding power supply, and the pulse current supply circuit 16 supplies a periodic The pulse current is supplied to the output end of the welding power supply, and the waveform of the current flowing through the arc 34 generated between the end of the wire 26 and the base metal 30 to be welded is shown in FIG. If I and time T are plotted on the horizontal axis, a waveform is obtained that is a combination of mountain-shaped pulse currents 40 spaced at regular intervals and a lower, smooth average DC current 42. This kind of welding current causes arc 3
4, the pulsed current 40 causes the arc 34
, that is, T _p shown in FIG.
During this period, the end of the wire 26 is heated by the excessive welding current, and a molten lump is formed at the end of the wire 26, and droplets from the end of the wire 26 reach the base material 3 to be welded.
0, a weld bead is formed on the surface of the base material 30 to be welded, and welding work can be performed.

In order to be able to perform stable welding by such a pulsed arc welding method, it is necessary to ensure that one droplet flows from the end of the wire 26 to the base material to be welded each time the pulsed current 40 flows through the arc 34. It is necessary that the so-called 1-pulse 1-droplet phenomenon, which moves to 30°, occurs stably. In order to stably sustain this 1 pulse 1 droplet phenomenon, the wire 2
The value I _p of the pulse current 40 and the generation period T _p of the pulse current 40 are controlled by the material of 6 and its outer diameter, and the square of the pulse current I _p and the pulse current generation period T p are controlled.
The value of _the ^pulse current _{40 ,} I _p
It is necessary to appropriately select the period T p and the period T _p of occurrence.

FIG. 3 shows the end of the wire 26 and the base material 30 to be welded.
The arc characteristic curve R is shown when the distance between the two electrodes, that is, the arc length is constant, the vertical axis shows the arc voltage V, and the horizontal axis shows the welding current I. Further, in FIG. 3, a pulse current characteristic curve Q and an average current characteristic curve S are drawn overlapping the arc characteristic curve R. The arc 34 is stably generated at the intersection points 50 and 52 of the current characteristic curves Q and S and the arc characteristic curve R.

Further, the arc length can be controlled by the feed rate of the wire 26 per unit time, and the welding current can be controlled by
This can be done by changing the output terminal voltage of the welding power supply device and the feed amount per unit time of the wire 26, and the pulse current 40 in the conventional pulsed arc welding method
is generally controlled by the output voltage V _p of the pulse current supply circuit 16 and the feed amount v of the wire 26 per unit time.

In the conventional pulsed arc welding apparatus as shown in FIG. 1 above, the pulsed current circuit 1
The control of the output voltage V _p of 6 is performed during the pulse current generation period.
This is done by adjusting the conduction period of the thyristor forming the rectifier circuit 20, which is equal to T _p .
In other words, the feed rate v of the wire 26 per unit time is set, and only the conduction period T _p of the thyristor constituting the rectifier circuit 20 is controlled accordingly to stabilize the so-called 1 pulse 1 droplet phenomenon. I tried to make it occur.

Therefore, when attempting to weld mild steel using such a pulsed arc welding device, the pulse current generation period T _p is shortened and the peak value I _p of the pulse current 40 is increased so that I _p ²・T If the value of _p is set to be a constant value based on empirical rules, an arc 3 generated between the end of the wire 26 and the base metal 30 to be welded
As a result of being able to improve the concentration in step 4, undercuts do not occur on the surface of the base material 30 to be welded during arc welding, and a weld bead with deep penetration can be formed, resulting in highly reliable and good arc welding. I was able to do that.

In addition, if the base material 30 to be welded is aluminum or the like,
An oxide film is usually formed on the surface of the base material 30 to be welded, and in order to perform stable and reliable arc welding, it is necessary to remove the oxide film on the surface. That is, the surface of the base material 30 to be welded is oxidized by the energy generated when the cations existing in the arc 34 generated between the wire 26 and the base material 30 to be welded collide with the surface of the base material 30 to be welded. After removing the coating, it is necessary to melt the base material 30 to be welded by arc heat and perform welding. To do this, wire 26
The arc 34 generated between the base metal 30 and the base metal 30 to be welded has a sufficient spread, so that the oxide is left as a solid on the surface of the base metal 30 due to the difference in melting temperature, resulting in a stable and good condition. It is necessary to ensure that arc welding is not impossible. That is, when the base material 30 to be welded is aluminum or the like, the generation period T _p of the pulse current 40 is lengthened, the peak value I _p of the pulse current 40 is decreased, and the value of I _p ² · T _p is determined by the empirical rule. It is better to set the values of I _p and T _p to be constant values based on , so that the arc 34 has a constant spread, so that the oxide film on the surface of the base material 30 to be welded is sufficiently spread in the arc 34. can be removed by the collision energy of positive ions, allowing stable and reliable arc welding.

However, in the welding method using the conventional pulse arc welding device described above, the output voltage V _p of the pulse current circuit 16 is controlled by the rectifier circuit 2.
In the pulsed arc welding apparatus in which the output _voltage of the welding transformer 18 of the pulsed current circuit 16 is set high, When the material 30 is made of aluminum or the like, the peak value of the pulse current is too large and the concentration of the arc 34 becomes high. As a result, oxides are left as a solid on the surface of the base material 30 to be welded, resulting in a stable and good welding condition. Arc welding was not possible. In addition, when the output voltage of the welding transformer 18 of the pulse current supply circuit 16 is set low in accordance with the welding work of the base material 30 to be welded such as aluminum, the peak value of the pulse current is small when welding mild steel etc. The arc 34 spreads too much and the base material 3 to be welded
Undercuts were likely to occur on the 0 surface, and the penetration was shallow, making it impossible to perform stable and good arc welding. In this way, in welding using a conventional pulse arc welding device, both base materials 30 such as mild steel and aluminum can be welded stably and in a good manner using one pulse arc welding device. The output voltage of the welding transformer 18 of the pulse arc current supply circuit 16 could not be changed appropriately depending on the material of the welding base material 30.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to easily weld mild steel and aluminum without using a separate power source, and to easily switch and adjust the welding of mild steel and aluminum. Pulse arc welding is easy to weld, and the concentration or spread of the arc generated between the wire end and the base material to be welded can be adjusted appropriately according to the material of the base material to be welded, allowing stable and good arc welding to be performed. The purpose is to provide a method.

In order to achieve this object, the pulse arc welding method of the present invention includes an average current supply circuit that applies a predetermined DC average current between a welding wire and a base material to be welded, and a transformer. a pulse current supply circuit that superimposes a transformed pulse current on the DC average current and applies it between the welding wire and the base material to be welded; the pulse current supply circuit has a voltage taken out from the transformer; A first circuit with a high pulse current value and a second circuit with a low pulse current value taken out from the transformer are provided, and when welding mild steel, the first circuit is used to maintain the conduction period. When welding aluminum, the second circuit is used to control the conduction period to be short, and the pulse current is supplied by selectively conducting the first and second circuits. It is designed to control the period of occurrence.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 4 shows a preferred embodiment of an apparatus for carrying out the pulse arc welding method according to the present invention,
Components that are the same as those in the conventional device shown in FIG. 1 are designated by the same reference numerals and their explanations will be omitted.

This embodiment is characterized by a tap 51 forming a first circuit and a tap 52 forming a second circuit in the middle of a coil 50 on the output side of the welding transformer 18 of the pulse current supply circuit 16. but,
The taps 51 and 52 are connected to a thyristor 58 constituting the rectifier circuit 20 of the pulse current supply circuit 16 via electromagnetic contactors 54 and 56, respectively.

When one electromagnetic contactor 54 is closed to obtain a high voltage from the transformer 18, the conduction period of the thyristor 58 is shortened, and the other electromagnetic contactor 56 is closed to obtain a low voltage from the transformer 18. To obtain this, the conduction period of the thyristor 58 is controlled to be long.

With the above configuration, when the base metal 30 to be welded is made of mild steel or the like, a concentrated arc 34 suitable for the welding conditions of the base metal 30 to be welded can be created between the end of the wire 26 and the base metal 30 to be welded. When welding, select the tap 51 of the coil 50 on the output side from which high voltage can be obtained from the welding transformer 18, close the electromagnetic contactor 54 connected to the tap 51, and start the welding operation. All you have to do is In other words, in this case, the generation period T _p of the pulse current 40 is shortened, and the welding work is performed with the peak value I _p of the pulse current 40 set high, so that the so-called 1 pulse 1 droplet phenomenon is stabilized. The above-mentioned welding transformer 1 is
Select the output side voltage of 8.

In addition, when performing arc welding on the base material 30 to be welded such as aluminum, the electromagnetic contactor 56 connected to the low voltage side tap 52 of the welding transformer 18 of the pulse current circuit 16 is in a closed state for welding. It's good to do the work. That is, in this case, the generation period T _p of the pulse current 40 becomes long, and the peak value I _p of the pulse current 40 is kept low, making the welding conditions suitable for welding work on aluminum etc. The output voltage of the welding transformer 18 is selected so that the phenomenon continues stably.

As described above, in the pulsed arc welding method according to the embodiment of the present invention, the output voltage of the welding transformer 18 is appropriately selected depending on the type of the base material 30 to be welded, and the pulsed current supply circuit 16 The conduction period T _p of the thyristor 58 constituting the rectifier circuit 20 of
By controlling the welding conditions, suitable welding conditions for the base material 30 to be welded can be easily obtained.

In the above embodiment, the electromagnetic contactors 54 and 56 are used to connect the welding transformer 1 of the pulse current supply circuit 16.
As shown in FIG.
Each thyristor 6 is provided with a plurality of switches 64 and a switch 64 that can be switched by a gate signal.
0 and 62, and connect the respective taps 51 and 52 of the coil 50 on the output side of the welding transformer 18 to the respective thyristors 60 and 62 constituting the rectifier circuit 20, so that the output of the welding transformer 18 is A changeover switch 6 attached to the thyristors 60 and 62 changes the side coil voltage.
4, the settings may be changed as appropriate.

Furthermore, in the present invention, a circuit example has been described in which a pulsed current with a frequency equal to the power supply frequency is used as the welding current, but the power supply frequency and the frequency of the pulsed current do not necessarily have to be equal, and the frequency of the pulsed current may be different from the power supply frequency. A wiring system for the welding transformer 18 and a rectification system for the rectifier circuit 20 may be used so that the selected pulse current frequency can be obtained.

Furthermore, in the embodiment, the pulse current supply circuit 16
Taps 51 and 52 are provided on the coil 50 on the output side of the welding transformer 18 to control the output voltage, but conversely, a plurality of taps are provided on the coil on the input side of the welding transformer 18. Please provide
It may be possible to control by the output voltage of the welding transformer 18.

As described above, according to the pulsed arc welding method of the present invention, the output voltage of the welding transformer of the pulsed current supply circuit is appropriately selected depending on the type of base material to be welded, and the pulsed current generation period T _p is adjusted. Because of this configuration, it is possible to easily switch and adjust the welding conditions to the optimum welding conditions for various base materials to be welded, and with one pulse arc welding device, stable and good welding conditions can be achieved for various base materials to be welded. It becomes possible to perform pulse arc welding.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration explanatory diagram showing an example of a conventional pulsed arc welding device, Fig. 2 is a welding current waveform diagram flowing in the arc, and Fig. 3 is an arc characteristic curve diagram, a pulse current characteristic curve diagram, and an average current characteristic diagram. curve diagram,
4 and 5 are schematic structural explanatory diagrams for explaining a preferred embodiment of the pulsed arc method according to the present invention. The same members in each figure are given the same reference numerals, 16 is a pulse current supply circuit, 18 is a welding transformer, 30 is a base material to be welded, 50 is a coil, 51 and 52 are taps, and 54 and 56 are electromagnetic contacts. 60 and 62 are thyristors, and 64 is a changeover switch.

Claims (1)

[Scope of Claims] 1. An average current supply circuit that applies a predetermined DC average current between a welding wire and a base material to be welded, and a transformer, and a pulse current transformed by the transformer is applied to the DC average current. and a pulse current supply circuit superimposed on the welding wire and the base metal to be welded. A second circuit is provided in which the voltage taken out from the transformer is low and the value of the pulse current is small, and when welding mild steel, the first circuit is used to control the conduction period to be short; When welding, the second circuit is used to control the conduction period to be longer, and the first and second circuits are selectively made conductive to control the generation period of the supplied pulse current. Pulse arc welding method. 2. A magnetic contactor is inserted into each of the first and second circuits, a single thyristor is connected in series with a parallel circuit consisting of the first and second circuits, and conduction of the thyristor is controlled. A pulse arc welding method according to claim 1. 3. It has two thyristors inserted in the first and second circuits respectively, and selectively switches between the first and second circuits, and in response to this switching, the two thyristors are inserted.
2. The pulse arc welding method according to claim 1, wherein the gate circuits of the two thyristors are selectively switched by a changeover switch.