JPH0338950B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an arc ignition method in a non-consumable electrode type arc welding method.

(Prior art) A feature of the non-consumable electrode arc welding method is that an inert gas is used as a shielding gas to shield the arc and weld metal from the atmosphere, so the arc is extremely stable and a smooth bead can be obtained, while welding One example is that there are no impurities in the metal. That is, since a high-quality and clean bead can be obtained, it is widely used for high-quality welding of medium and thin plates, root pass welding of thick plate multilayer welding, etc.

Now, as an arc ignition method in the conventional non-consumable electrode type arc welding method, a method generally called a high frequency ignition method has been used. Figure 2 shows its configuration.

The anode side of the welding power source 1 having DC drooping characteristics is connected to the base material 3 to be welded, and the cathode side is connected to the tungsten electrode 2 in the welding torch 7 via the high frequency power source 4.
Connect to. Note that 5 is a high frequency bypass capacitor.

While inert gas is being supplied as a shielding gas through the shielding cap 6 (description of the shielding gas will be omitted in the following explanation).
A high frequency voltage of several thousand V or more is applied between the tungsten electrode 2 and the base metal 3 by the high frequency power source 4 to cause spark discharge and dielectric breakdown, and then a current is supplied by the welding power source 1. It ignites an arc.

However, in such a high-frequency ignition method, electromagnetic noise is generated due to the high frequency, which may malfunction or damage various peripheral electronic devices such as microcomputers built into automatic welding equipment. Therefore, it was necessary to take special measures such as using a noise filter.

Furthermore, the high-frequency ignition method has the disadvantage that it cannot be easily connected because the measuring equipment is damaged when high-frequency voltage is applied.

Due to these factors, it has been difficult to automate the non-consumable electrode arc welding process using precision equipment such as welding robots and to control welding phenomena using precision measuring equipment.

The touch ignition method was developed as an improvement method. FIG. 3 shows its configuration. A base material 3 to be welded is connected to the anode side of a welding power source 1 having DC drooping characteristics, and a tungsten electrode 2 in a welding torch 7 is connected to the cathode side.

This method involves applying the no-load voltage of the welding power source 1 between the tungsten electrode 2 and the base metal 3.
The tungsten electrode 2 is brought into contact with and short-circuited to the base material 3, a short-circuit transient current is caused to flow, and then the tungsten electrode 2 is separated from the base material 3 to ignite an arc.

However, in this method, the tungsten electrode 2 is subject to wear and tear such as melting and deformation due to the excessive current generated at the time of short circuit, which significantly shortens the electrode life and sometimes makes it difficult to perform welding.

In order to improve this, in JP-A-59-50970 and JP-A-59-76675, the contact between the tungsten electrode 2 and the base material 3 is electrically detected, and based on this, tungsten A method has been proposed to suppress the wear and tear on the tungsten electrode 2 during contact and short circuit by controlling the timing of separating the electrode 2 from the base material 3 and further suppressing the current flowing during a short circuit.

However, this does not completely eliminate electrode wear, and some electrode wear occurs, shortening the electrode life.

Non-consumable electrode arc welding, which is characterized by high-quality welding with a stable arc, has a fatal disadvantage of electrode wear that leads to arc instability.

(Problems to be Solved by the Invention) The present invention provides a non-consumable electrode type arc welding method that does not cause electrode wear and eliminates the influence of high-frequency noise, thereby preventing malfunction or damage to peripheral measuring equipment and control equipment. The purpose is to provide an arc ignition method.

(Means for Solving Problems) The gist of the present invention is to connect a non-consumable electrode to the negative side of a DC welding power source, connect the base material to the positive side, and arrange an auxiliary electrode to face the side surface of the non-consumable electrode. By connecting the auxiliary electrode and the base material, an electric field is generated from the auxiliary electrode toward the non-consumable electrode, and by injecting ignited plasma from the vicinity of the auxiliary electrode toward the side of the non-consumable electrode, an arc is generated. The present invention relates to an arc ignition method in a non-consumable electrode type arc welding method, which is characterized by ignition.

The present invention will be described in detail below with reference to the drawings.

First, FIG. 1a shows a schematic diagram of a welding apparatus for carrying out the method of the present invention.

In the figure, 1 is a welding power source with DC drooping characteristics, the tungsten electrode 2 (hereinafter referred to as main electrode) in the welding torch 7 is connected to its cathode side, and the base material 3 to be welded is connected to its anode side. , a welding electric circuit 8 consisting of a welding power source 1, a tungsten electrode 2, and a base material 3 is formed.

Further, a plasma nozzle 13 and a tungsten electrode 12 (hereinafter referred to as a sub-electrode) are arranged near the main electrode 2, and the sub-electrode is connected to the cathode side of the plasma device 10, and the plasma nozzle 13 is connected to the anode side of the plasma device 10. , sub-electrode 12, plasma nozzle 1
A plasma jet circuit 18 consisting of 3 is formed.

Further, the plasma nozzle 13 and the base material 3 are connected. By turning on the welding power source 1, an electric field is formed between the main electrode 2 and the plasma nozzle 13 from the plasma nozzle 13 toward the main electrode 2.

In this state, the plasma gas is transferred to the plasma nozzle 13.
(Description of plasma gas will be omitted in the following explanation) and turn on the plasma device 10.
Then, plasma is generated using the plasma jet circuit 18, and the plasma is injected toward the main electrode 2.

At this time, the positive ions in the plasma injected into the electric field are accelerated by the electric field, collide with the main electrode 2, and increase the temperature of the collision part, so that the voltage of the welding power source 1 easily ignites the arc.

At this time, an arc is first formed from the main electrode 2 toward the plasma nozzle 13, but immediately
to base material 3.

FIG. 1b shows a schematic diagram of another embodiment.

The circuit configuration is almost the same as that in FIG.
Plasma nozzle 13 and dummy electrode 20 using
and isolation.

(2) Dummy electrode 2 instead of plasma nozzle 13
0 and base material 3 are connected.

There are two differences.

That is, a feature is that the welding electric circuit 8 and the plasma jet circuit 18 are completely isolated.

By turning on the welding power source 1, an electric field is formed between the main electrode 2 and the dummy electrode 20 from the dummy electrode 20 toward the main electrode 2.

In this state, the plasma device 10 is turned on, plasma is generated using the plasma jet circuit 18, and is injected toward the main electrode 2 through the small hole of the dummy electrode 20. At this time, the positive ions in the plasma injected into the electric field are accelerated by the electric field, collide with the main electrode 2, and increase the temperature of the collision part, so that the voltage of the welding power source 1 easily ignites the arc.

At this time, an arc is initially formed from the main electrode 2 toward the dummy electrode 20, but immediately moves from the main electrode 2 to the base material 3.

According to the present invention, since an arc can be ignited without using a high frequency power source in the welding electric circuit 8, a device for measuring electric signals such as arc voltage can be directly connected. Furthermore, there is no risk of malfunction or damage to the control device due to the high frequency nozzle. Therefore, according to the present invention, automation using precision equipment and control of welding phenomena using precision measuring equipment, which has been extremely difficult in the past, becomes possible.

Further, according to the present invention, the plasma jet circuit 1
8, a low current plasma jet of a maximum of about 5 to 20 A is generated, and injection for a short time of about 0.05 to 1.0 seconds is sufficient to ignite the arc.
Furthermore, the plasma nozzle 13 can be miniaturized because only the plasma gas is required to generate the plasma jet and no shielding gas is required.

Furthermore, the discharge gap between the sub-electrode 12 and the plasma nozzle 13, and the shape and material of each can be arbitrarily set to facilitate discharge.

In addition, since the plasma jet for arc ignition requires low current and only short-term use, the sub-electrode 1
2 and the plasma nozzle 13 are extremely slight.

The outline of the present invention has been described above.

Next, the plasma device 10 used in FIGS.
A method of igniting the plasma jet circuit 18 will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a schematic diagram showing a plasma jet circuit for arc ignition using the touch ignition method. 11
is a plasma power supply having DC drooping characteristics, with a sub-electrode 12 on the cathode side and a plasma nozzle 1 on the anode side.
3 are connected to each other to form a plasma jet circuit consisting of a plasma power source 11, a sub-electrode 12, and a plasma nozzle 13.

Turn on the plasma power supply 11, and while applying no-load voltage, contact and short-circuit the sub-electrode 12 to the plasma nozzle 13 using manual, electric, bimetal, spring-loaded, or other means to flow a short-circuit transient current. After that, the sub-electrode 12 is separated from the plasma nozzle 13 to ignite the plasma jet.

In the conventional touch ignition method, there was a problem of wear and tear on the tip of the main electrode due to excessive current during short circuits, but in plasma jets for arc ignition, since the current is originally low (maximum 5 to 20 A), the secondary The wear and tear on the electrode tip is extremely slight. Moreover, even if it is slightly worn out, it is enough to ignite the plasma jet and it is unrelated to the welding electric circuit 8, so it does not pose a problem in welding.

FIG. 5 is a schematic diagram showing a plasma jet circuit for arc ignition using the high frequency ignition method. 11
is a plasma power supply having DC drooping characteristics, and a sub-electrode 12 is connected to its cathode side via a high-frequency power supply 14, and a plasma nozzle 13 is connected to its anode side. Note that 15 is a high frequency bypass capacitor. A plasma jet circuit 18 is formed by a plasma power source 11, an auxiliary electrode 12, a plasma nozzle 13, a high frequency power source 14, and a high frequency bypass capacitor 15.

This circuit uses a high frequency power source 14 to
After a high frequency voltage is applied between the plasma nozzle 13 and the plasma nozzle 13 to cause spark discharge and dielectric breakdown, the plasma power supply 11 supplies current to ignite the arc.

However, since the discharge gap between the plasma nozzle 13 and the sub-electrode 12 can be set as small as about 0.1 mm, it is sufficient that the output voltage of the high-frequency power source 14 is about 1,000 V at maximum. The level of high frequency noise generated is also low.

Therefore, by covering the plasma jet circuit 18 with the shield 16 and connecting it to an external power source through the noise filter 17, high frequency noise can be easily and completely suppressed.

Note that the high-frequency power source 14 does not need to be connected to the cathode side of the plasma power source 11, and may be placed anywhere as long as a circuit is formed by the sub-electrode 12, the plasma nozzle 13, the high-frequency power source 14, and the high-frequency bypass capacitor 15. .

In FIG. 5, the high frequency voltage generated by the high frequency power source 14 is used to ignite the plasma jet circuit 18, but any power source capable of supplying the same voltage can be incorporated into the plasma jet circuit 18. In fact, it is possible to ignite the plasma jet in the same way by using the capacitor discharge voltage from the capacitor power supply or the surge voltage generated when the current is cut off.

(Example) An example using the apparatus shown in FIG. 6 is shown below.

In the figure, a shows the entire device, and b shows the plasma jet circuit.

Plasma jet circuit side: No-load voltage of plasma power supply 11 100V, plasma jet current 10A, plasma gas flow rate 3/
minAr, D = 1.0mm, l _t = 1.0mm, l _p = 1.2mm, d _s =
1.0mm.

Welding electric circuit side: Welding power supply 1 no-load voltage 47V, set welding current
50A, shielding gas flow rate 20/min Arl _a = 4mm,
l _b = 5 mm, l _c = 10 mm, d _n = 2.4 mm.

We tried to ignite the arc 100 times in a row by injecting plasma for 0.1 seconds under these conditions, and in each case we were able to ignite the arc extremely stably. Moreover, no wear was observed on the main electrode 2, the sub-electrode 12, and the plasma nozzle 13.

In addition, almost no voltage fluctuations in the external power supply were observed when high-frequency waves were generated, and although the measuring equipment or control device used at this time had a built-in microcomputer, no malfunctions due to high-frequency noise occurred.

(Effects of the Invention) As detailed above, according to the present invention, there is no need to use a means that causes noise, such as a high frequency power supply, in the welding electric circuit, so the control device uses electronic equipment such as a microcomputer. There is no need to take noise countermeasures. Furthermore, since there is no fear of damage to measuring equipment, etc., even more precise measurements are possible. Furthermore, since it is a non-contact type of arc ignition, there is no problem with wear and tear on the main electrode, and it has great industrial value.

[Brief explanation of the drawing]

Figs. 1a and 1b are schematic diagrams showing an example of a device implementing the present invention, Figs. 2 and 3 are schematic diagrams showing a conventional example, and Figs. 4 and 5 are plasma jets for arc ignition. A schematic diagram showing an embodiment of the circuit, FIG. 6a is a diagram showing an example of a specific arrangement of a device implementing the present invention,
FIG. 6b is a diagram similarly showing the plasma jet circuit. 1: Welding power source, 2: Tungsten electrode (main electrode), 3: Base material, 4: High frequency power source, 5: High frequency bypass capacitor, 6: Shield cap,
7: Welding torch, 8: Welding electric circuit, 10: Plasma device, 11: Plasma power supply, 12: Tungsten electrode (auxiliary electrode), 13: Plasma nozzle,
14: High frequency power supply, 15: High frequency bypass capacitor, 16: Shield, 17: Noise filter, 18: Plasma jet circuit, 19: Insulator, 20: Dummy electrode.

Claims (1)

[Claims] 1 Connect the non-consumable electrode to the negative side of the DC welding power source and the base material to the positive side, place the auxiliary electrode so as to face the side of the non-consumable electrode, and connect the auxiliary electrode to the base material. Non-consumable electrode type arc welding characterized by igniting an arc by injecting ignition plasma from the vicinity of the auxiliary electrode toward the side surface of the non-consumable electrode while generating an electric field directed toward the non-consumable electrode. Arc ignition method in law.