JPS6157113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an arc welding machine that stably melts wire in a non-consumable electrode type arc welding machine for TIG welding, plasma welding, etc.

One of the prior art technologies closest to the present invention is a welding machine shown in FIG.
The wire 5 is energized via the variable resistor 4. However, in such a welding machine, the wire 5
Since a shunt current with DC droop characteristics flows through the wire, a nearly constant current is maintained at the start and end of welding, even when there are fluctuations in wire feed rate or plasma current fluctuations during welding. Excessive melting and arc penetration phenomena are likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide an arc welding machine that is capable of melting the wire at a substantially constant position without always moving the wire away from the arc despite the above-mentioned fluctuations.

The present invention is characterized in that a separate power source with DC constant voltage characteristics is provided as a power source for supplying current to the wire.

By connecting a power source with DC constant voltage characteristics as the power source for energizing the wire, the value of the current flowing through the wire will not melt due to fluctuations in wire feed rate or main arc current fluctuations. This utilizes the characteristic of an arc that self-adjusts in the direction of stability.

An embodiment in which the present invention is applied to a plasma arc is shown in FIG.

A power source 3 having DC drooping characteristics is provided between the non-consumable electrode 1 and the material to be welded 2, and an arc 6 is generated. Furthermore, a power supply 7 having DC constant voltage characteristics is also provided between the non-consumable electrode 1 and the wire 5.
An arc is generated between the two.

In addition, in the power source 3 with DC droop characteristics, the negative electrode is connected to the non-consumable electrode 1 side and the positive electrode is connected to the welded material 2 side, and the power source 7 with DC constant voltage characteristics also corresponds to the connection method of the power source 3. Then, connect the negative electrode to the non-consumable electrode 1 side and the positive electrode to the wire 5 side.

The reason why the positive and negative polarities of the non-consumable electrode 1, the workpiece 2, and the wire 5 are limited in the power source 3 and the power source 7 is that in the power source 3, the positive electrode is
If the negative electrode is connected to the welding material 2 side in the opposite manner to that described above, the non-consumable electrode 1 will be seriously damaged, which is not desirable. Also, in the power supply 7, if the positive electrode is connected to the non-consumable electrode 1 side and the negative electrode is connected to the wire 5 side, current will also flow between the power supply 3 and the power supply 7, and in order to prevent such a flow from occurring, the polarity should be changed. This is because it is necessary to limit the

FIG. 3 is a diagram showing the relationship between the wire feed rate (m/min) by the arc welding machine of the present invention and the current A flowing through the wire. That is, if the current flowing through the wire is set to 100 A and then the feed rate is varied, the current will automatically change as shown by the solid line and be adjusted favorably. In addition, the wire current shows stability against fluctuations in the wire feed rate, and shows stable melting at a wire feed rate of 5.2 m/min.
This shows that if the value set at 100A fluctuates for some reason, for example if the feed rate becomes low, the current value will self-adjust to a low current to prevent over-melting.

This self-adjustment effect can be explained as follows.
In other words, when the wire feed rate decreases,
A phenomenon occurs in which the wire melts at the outer edge of the main arc (it melts quickly and falls in front of the main arc), the surface of the wire exposed to the main arc decreases, and the arc voltage of the wire increases. As a result, the current flowing through the wire is self-adjusted from 100A to a lower current according to the current-voltage characteristics of the DC constant voltage power supply (the current decreases greatly for a slight increase in voltage), and the melting state of the wire changes. Maintained stably.

In this case, after the current flowing through the wire is set to 100A, it goes without saying that there is no need to make any manual adjustments, and furthermore, there is no need to control the current to change automatically in advance. This is due to the voltage change caused by the arc phenomenon and the use of the characteristics of the power supply.

Similarly, Figure 4 is a diagram showing the relationship between the plasma arc current A and the current A flowing through the wire when a plasma arc is used as the main arc.
After setting it to 100A, when the plasma arc current is varied, the current flowing through the wire automatically changes as shown by the solid line, and is adjusted to the desired value.

It also shows the stability against main arc current fluctuations, and when the plasma arc current is 200A,
If the wire current set at 100A, which indicates stable melting, fluctuates for some reason, for example when the plasma arc reaches a high current, the wire current will self-adjust to a low current to prevent excessive melting. On the contrary, when the plasma arc current becomes low, the wire current is self-adjusted to a high current to prevent unmelting.

This self-adjustment effect can be explained as follows.
That is, when the plasma arc reaches a high current, the wire becomes more likely to melt, the melting position of the wire extends to the outer edge, the surface of the wire exposed to the plasma arc decreases, and the arc voltage of the wire increases. On the other hand, when the current becomes low, the wire enters the center of the plasma arc and melts, so the arc voltage of the wire decreases. At this time, when the main plasma arc current becomes high at the same time, the voltage of the plasma arc becomes high, so the arc voltage of the wire also becomes high, and when the plasma arc current becomes low, the voltage of the plasma arc increases. As the voltage decreases, a phenomenon occurs in which the arc voltage of the wire also decreases. This is because the potential gradient of the plasma arc changes, and these phenomena also work in the direction of stably maintaining the molten state of the wire by decreasing the current of the wire as the current of the plasma arc increases. These are the results of utilizing the voltage change based on the arc phenomenon and the characteristics of the power supply, and thus the present invention does not require any readjustment or automatic control.

Although the above example uses a plasma welding method, it goes without saying that other non-consumable electrode welding methods such as TIG can have similar effects.

The present invention provides an arc welding machine that always maintains the wire welding position at a constant position in the arc during welding, and as a result maintains stable wire melting despite various fluctuations. It will be done.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an example of the conventional technology;
The figure is a block diagram showing an embodiment in which the present invention is applied to a plasma arc welding machine, FIG. 3 is a diagram showing changes in the current flowing through the wire due to fluctuations in the wire feed rate, and FIG. FIG. 3 is a diagram showing changes in the current flowing through the wire due to fluctuations in the plasma arc current. 1... Non-consumable electrode, 2... Material to be welded, 3... DC drooping power supply, 5... Wire, 7... DC constant voltage power supply.

Claims (1)

[Claims] 1. In a welding machine that welds while feeding a wire into an arc generated between a non-consumable electrode and the material to be welded, a power source with DC droop characteristics is installed between the non-consumable electrode and the material to be welded, and A power source with DC constant voltage characteristics is provided between the consumable electrode and the wire, and in the power source with DC droop characteristics, the negative electrode is connected to the non-consumable electrode side and the positive electrode is connected to the material to be welded. An arc welding machine characterized in that, in a characteristic power source, the negative electrode is connected to the non-consumable electrode side and the positive electrode is connected to the wire side.