JPS6241838B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention makes it possible to easily control the short-circuit period in a DC arc welding machine using a consumable electrode, and in particular, to obtain a stable bead by increasing the number of short-circuits in a small current area. This invention relates to a DC arc welding machine.

In general, CO ₂ arc welding and MIG welding are short-circuit transition type welding that uses a DC power supply with constant voltage characteristics or quasi-constant voltage characteristics and a consumable electrode, and the electrode and the base metal repeatedly short circuit and arc. In the conventional short-circuit transfer type DC arc welding machine, power is supplied to the consumable electrode and the base material from the DC power supply via the DC reactor. This DC reactor limits excessive current at the time of a short circuit arc, alleviates sudden changes in current, and controls the arc phenomenon.Furthermore, at the time of re-arcing, the energy of Ldi/dt stored during the short circuit is released to break the arc. It is indispensable in short-circuit transfer type DC arc welding machines, which transfer to an arc due to a short circuit between the electrode and the base metal.

In addition, during steady state, short circuits and arcs are repeated, the feeding speed and penetration of the consumable electrode are balanced, the welding finish and bead appearance are good, and there are few spatters.

However, if the feeding speed of the consumable electrode becomes slow for some reason, the arc generation period becomes longer, the consumable electrode melts due to the arc heat, the electrode droplet becomes larger, and especially in the case of semi-automatic welding, penetration may occur. Some parts are not there, and some parts are not there, resulting in uneven welding and increased occurrence of spatter.

Therefore, as described in Japanese Patent Publication No. 51-47653, diodes, resistors,
A device in which a series circuit of capacitors is provided and a discharge resistor is provided in the capacitor has been proposed.

By the way, in the above proposal, the charge in the capacitor is discharged through the discharge resistor only when the electrode feeding speed becomes slow and the arc generation period becomes longer, and it does not follow all short circuits. , poor arc followability, incomplete overlay, and uneven beads. Furthermore, the number of short circuits per unit time is limited, the range in which the arc time can be shortened is limited, and there is a limit to penetration, making it particularly unsuitable for welding thin plates.

This invention was made with the above-mentioned points in mind, and the voltage induced in the reactor when the consumable electrode and the base material are short-circuited is returned to the power supply circuit, thereby improving the followability of the arc and making the bead uniform. As the
It can shorten the short circuit cycle, improve build-up, and be suitable for semi-automatic welding. It can also increase the rising current to increase the pinch effect, increase the number of short circuits, and shorten the arc time. , has low penetration and is particularly suitable for welding thin plates.

Next, the present invention will be explained in detail with reference to drawings showing embodiments thereof.

First, in FIG. 1 showing one embodiment, 1 is a DC power supply with constant voltage characteristics or quasi-constant voltage characteristics;
are the + terminal and - terminal of the DC power supply 1, 4 is the electrode side load terminal connected to the + terminal 2, 5 is the base material side load terminal connected to the - terminal 3 via the primary reactor 6, and 7 is the transmission side load terminal. A consumable electrode is fed by a drive roll 8 driven by a feed drive device, 9 is a power supply chip connected to the electrode side load terminal 4 and supplies power to the consumable electrode 7, and 10 is a motherboard connected to the base material side load terminal 5. wood,
11 is a secondary reactor whose one end is connected to the load terminal 5 on the base material side, and 12 and 13 are variable resistors and diodes as a rectifier connected in series between the other end of the secondary reactor 11 and the electrode side load terminal 4. A feedback circuit consisting of a series circuit of a secondary reactor 11, a variable resistor 12, and a diode 13 is connected in parallel to the power supply circuit.

Next, the operation of the above embodiment will be explained with reference to FIG. Figure a shows the arc voltage VA, T
1 and T2 are short circuit periods, and T1' and T2' are arc periods. Figure b shows the voltage across the primary reactor 6.
VL1, and the secondary reactor 11 has a voltage VL
A voltage proportional to 1 is induced. Figure c shows the current IL2 flowing through the secondary reactor 11.

Then, the moment the electrode 7 and the base material 10 are short-circuited,
A current flows from the DC power supply 1 to the power supply circuit between the electrode 7 and the base material 10, and by energizing the primary reactor 6, a voltage VL2 is induced in the secondary reactor 11, and the variable resistor 12, diode 13, and both load terminals 4, 5 is fed back to the electrode 7 and base material 10 via the induced voltage VL
2, the current IL2 flows from the DC power supply 1 to the electrode 7.
This is superimposed on the current flowing through the base material 10, and the rise characteristic of the short-circuit current flowing between the electrode 7 and the base material 10 becomes steeper than that of the current flowing from the DC power source 1 into the electrode 7 and the base material 10.

Then, when the value of the variable resistor 12 is changed, the current IL2 is changed, and the number of short circuits is increased or decreased. now,
When the value of the variable resistor 12 is decreased, the current IL2 increases, a steep current flows at the moment the electrode 7 is short-circuited with the base material 10, the distance over which the electrode 7 is fused is shortened, and the next short-circuit time is shortened. In addition, the short circuit current is small, the arc time is short, the number of short circuits is increased, and the short circuit period is short. In this case, as the number of short circuits increases, the arc time also becomes shorter, which reduces the amount of heat, but on the other hand, melting decreases, making it suitable for welding thin plates, eliminating melting and resulting in good welding. .

Furthermore, as a means for feeding back the induced voltage VL2 of the secondary reactor 11 to the power supply circuit, in addition to the means shown in FIG. 1, the means shown in FIGS. 3 to 6 can be applied as appropriate.

That is, in FIG. 3, a reactor 14 is used instead of the variable resistor 12 in FIG. 1, and in FIG. 4, one end of the secondary reactor 11 is connected to one terminal 3, and the other end is connected to a diode. 13 to the load terminal 4.

In addition, in FIG. 5, both ends of the secondary reactor 11 are connected to a full-wave rectifier 15, and both output ends are connected to a resistor 1.
In FIG. 6, both output ends of the rectifier 15 in FIG. 5 are connected to the - terminal 3 and the load terminal 4.

Next, FIG. 7 showing another embodiment of the present invention will be described. One end of each of the star-connected three-phase secondary windings T1, T2, and T3 of the transformer 17 is +
The other ends are connected to the negative terminal 3 via the main thyristors S1, S2, S3, respectively, and the intermediate taps of the secondary windings T1, T2, T3 connect to the base thyristor S1', respectively. ,S
2', connected to the base terminal 3' via S3',
A DC power supply 1' is formed.

The + terminal 2 is connected to the electrode side load terminal 4, the - terminal 3 is connected to the base material side load terminal 5 via two primary reactors 6', 6, and the base terminal 3' is connected to both primary reactors. It is connected to the connection point of the reactors 6', 6. Furthermore, two secondary reactors 11,
11', a variable resistor 12, and a diode 13 are connected in series.

This embodiment has a base circuit, and the two primary reactors 6, 6' are provided with secondary reactors 11, 11', respectively, to reduce the voltage induced during short-circuit transition, especially in the small current range where stability is required. The voltage of the reactor is returned to the load side, a steep current is passed between the electrode 7 and the base material 10, the short circuit time is shortened, the current flowing time is shortened, and the energy accumulated in the reactor is reduced. This increases the number of short circuits and reduces spatter, resulting in excellent welding with an extremely stable arc.

In the embodiment shown in FIG. 7, instead of the secondary reactor 11' and the variable resistor 12, an impedance circuit including only a resistor, only a reactor, or a resistor and a reactor may be used.

Moreover, as another embodiment of FIG. 7, the configuration as shown in FIGS. 8 to 10 can also be used.

That is, FIG. 8 shows both primary reactors 6,
One end of the secondary reactor 11 in FIG. 7 is connected to the connection point 6'.

In FIG. 9, both ends of one secondary reactor 11 are connected to a full-wave rectifier 15, one end of the output end of the rectifier 15 is connected to the load terminal 5 on the base metal side, and the other end is connected to the other secondary reactor 11'. These are connected to the electrode-side load terminals 4 via resistors 12, respectively.

Further, in FIG. 10, the negative terminal 3 is connected to the electrode side load terminal 4 via one secondary reactor 11, variable resistor 12, and diode 13.

As described above, according to the DC arc welding machine of the present invention, in the DC arc welding machine that supplies power to a consumable electrode and a base material from a DC power source and generates an arc by contact between the consumable electrode and the base metal, the DC power supply a primary reactor installed in series with the power supply circuit;
By providing a secondary reactor that induces a voltage proportional to the voltage of the primary reactor, and a feedback circuit that is provided in parallel with the power supply circuit and is composed of a series circuit of the secondary reactor and a rectifier, the rise of the welding current is reduced. This makes it possible to increase the number of short circuits, especially in the small current range, making it suitable for welding thin plates.

[Brief explanation of the drawing]

The drawings show an embodiment of the DC arc welding machine of the present invention, FIG. 1 is a wiring diagram of one embodiment, FIG. 2 a,
b, c are the voltage and current waveform diagrams at each part in Figure 1, and Figure 3.
10 through 10 are connection diagrams of other embodiments, respectively. 1... DC power supply, 6, 6'... Primary reactor, 7... Electrode, 10... Base material, 11, 11'...
...Secondary reactor, 12...Variable resistor, 13...
Diode, 14...reactor, 15...full wave rectifier.

Claims (1)

[Claims] 1. In a DC arc welding machine that supplies power to a consumable electrode and a base material from a DC power source and generates an arc by contact between the consumable electrode and the base metal, a primary reactor provided in series with the power supply circuit of the DC power source; A DC arc characterized by comprising: a secondary reactor that induces a voltage proportional to the voltage of the primary reactor; and a feedback circuit that is provided in parallel with the power supply circuit and consists of a series circuit of the secondary reactor and a rectifier. Welding machine.