JPH0337835B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention generates an electric discharge between at least one discharge electrode and a workpiece or another electrode, and generates heat due to the electric discharge. The present invention relates to an arc ignition method used for welding, cutting, thermal spraying, or heating processing of workpiece materials.

[Prior art] Conventionally, the main electrode for discharge and the workpiece or another
A high-frequency ignition method that applies a high-frequency voltage between two electrodes to cause dielectric breakdown between them to start an arc discharge, or a contact spark that is generated by bringing the main discharge electrode into contact with the workpiece. Arc discharge for machining is started by a contact ignition method in which the main discharge electrode is separated from the workpiece material after the contact ignition process is completed, and the contact spark discharge is transferred to arc discharge.

[Problems to be solved by the invention] However, in the conventional high-frequency ignition method, the high-frequency voltage used to start the arc is large, so high-power electromagnetic noise is generated, and the micro- This can cause malfunction or damage to various peripheral electronic devices such as computers, and it has been necessary to take measures such as using special noise filters to deal with this type of high frequency, high power noise. Furthermore, since the measuring device connected to the arc power supply circuit is damaged during high-frequency ignition, there is a problem that the measuring device cannot be easily connected to the welding electric circuit.

On the other hand, in the conventional contact ignition method, arc ignition may fail depending on the tip shape of the discharge main electrode and the surface condition of the workpiece.

SUMMARY OF THE INVENTION An object of the present invention is to provide an arc ignition method that substantially does not generate high-power, high-frequency noise during ignition, is easy to ignite, and is highly stable.

[Means for Solving the Problems] In the present invention, an electric field is formed near at least one discharge main electrode and the workpiece or another electrode, and ignition plasma is directed toward the cathode of the electric field. The feature is that the arc is ignited by injecting.

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

[Operation] FIG. 1 shows a schematic configuration of an example of an apparatus for implementing the present invention and an outline of an arc phenomenon that occurs when the present invention is implemented. This is a case of arc discharge machining in which the main discharge electrode 2 is connected to the negative side of the DC power source 1 for machining, and the base material 3, which is the material to be machined, is connected to the positive side.

As shown in FIG. 1, a perforated electrode 13 is arranged as an example of an auxiliary electrode opposite to the side surface of the main electrode 2, and by grounding the base material 3, an electric field is generated from the perforated electrode 13 toward the main electrode 2. In this state, the perforated electrode 1
When ignited plasma is injected towards the main electrode 2 through the hole 3 (a in Figure 1), an arc is ignited from the main electrode 2 towards the perforated electrode 13 (b in Figure 1).
When establishing a special relationship between the main electrode 2, the base material 3, and the perforated electrode 13, which will be described later, the main electrode 2
The upper cathode spot instantly moves to the tip of the main electrode 2 (c in FIG. 1), and an arc is ignited between the main electrode 2 and the base material 3 (d in FIG. 1).

Note that if there is a shielding gas flow Qs flowing in the axial direction of the main electrode 2, this gas flow also participates in the cathode spot migration phenomenon.

Next, the main electrode 2 in the cathode spot migration phenomenon,
The influence of the positional relationship between the base material 3 and the perforated electrode 13 will be explained.

FIG. 2a is a schematic diagram showing the positional relationship among the base material 3, the main electrode 2, and the perforated electrode 13.

As shown in FIG. 2a, the main electrode 2 is arranged to face the base material 3, and the perforated electrode 13 is arranged to face the side surface between the main electrodes 2. At this time,
The distance between the main electrode 2 and the base material 3 is abbreviated as La, the distance between the main electrode 2 and the perforated electrode 13 as Lb, and the distance from the tip of the main electrode 2 to the center of the hole of the perforated electrode 13 as Lc. .

Figures 2b and 2c show La, Lb and Lc
This figure shows the relationship between the combination of and the arc ignition phenomenon.

The ignition plasma generation conditions used were as follows: ignition plasma current was 13 A, ignition plasma gas flow rate was 3.0/min: Ar, and the outer diameter of the perforated electrode was 10 mm. The × in the figure indicates the position where b in Fig. 1 does not fire, and the 〇 indicates the position that is suitable for implementing the present invention, because after b in Fig. 1 is ignited, it gradually shifts to d in 1 second or more. △ indicates a position where the position slowly transitions to d after 1 second or more after firing b in Figure 1, but the response is slow and is not practical; the mouth is held at b after firing b in Figure 1. Indicates a position that does not move.

As can be seen from Figures 2b and 2c, La,
The arc ignition phenomenon differs greatly depending on the combination of Lb and Lc, and when a special relationship is established between La, Lb, and Lc (the area marked with a circle in the figure), the machining arc will start instantaneously after the ignition plasma is injected. It can be seen that ignition occurs between the main electrode 2 and the base material 3.

Figure 2d shows the relationship between the combinations of La, Lb and Lc and the arc ignition phenomenon when the ignition plasma generation conditions are changed. The optimal positional relationship between the base material, main electrode, and perforated electrode in Figures 2b and 2c (the area marked with a circle in the figure) is based on the ignition plasma current, which is the ignition plasma generation condition, from 5A to 5A.
Select within the range of 40A and set the ignition plasma gas flow rate.
When selected within the range of 0.5/min:Ar to 10/min:Ar, the range was expanded to the range shown in FIG. 2d, confirming that the present invention could be applied.

Next, a method for generating ignited plasma used in carrying out the present invention will be described.

FIG. 4a is a schematic diagram of a touch-ignited plasma generation method. This method uses plasma power source 11
Connect the sub-electrode 12 to the negative side and the perforated electrode 13 to the positive side, supply plasma gas (omitted in the following explanation), start the plasma power supply 11, and apply a no-load voltage to the sub-electrode. By once bringing the electrode 12 into contact with the perforated electrode 13 and then separating it, a spark discharge is generated and this is transformed into an arc discharge.

Since a small current of about 10A is sufficient for the ignition plasma, damage to the sub-electrode 12 during touch ignition is slight, and even if it is worn out, as long as the ignition plasma can be started, the main electrode 2 for machining can be used. There is no problem because it is unrelated.

FIG. 4b is a schematic diagram of a high frequency ignition type ignition plasma generation method. A sub-electrode 12 is connected to the negative side of the plasma power source 11 via a high-frequency power source 14, and a perforated electrode 13 is connected to the positive side of the plasma power source 11, respectively. Note that 15 is a high frequency bypass capacitor. In this method, a high frequency high voltage is applied between the sub electrode 12 and the perforated electrode 13 by a high frequency power source 14 to cause dielectric breakdown.
It starts ignited plasma.

Since the distance between the sub-electrode 12 and the perforated electrode 13 can be set to a very small distance, ignition plasma can be started even with a high-frequency voltage of about 1000V. The high frequency noise generated at this time is removed from the ignition plasma circuit 18 by the shield 1
0 and is connected to an external power supply via the noise filter 17, it is possible to prevent the influence of high frequency noise on the outside.

FIG. 4c is a schematic diagram showing an electrode self-heating type ignition plasma generation method. A filament heating power source 84 is connected to both ends of the auxiliary electrode bent into a hairpin shape (hereinafter referred to as filament 85), and the negative side of the plasma power source 11 is connected to one end of the filament 85, and the positive side is connected to the perforated electrode 13. , connect respectively. In this method, the temperature of the filament 85 is raised to 2,000 degrees or more using a current supplied from the filament heating power source 84 due to Joule heat generation, and the plasma power source 1
Thermionic emission is generated using one power source, and this is transferred to arc discharge to start ignited plasma.

Example 1 An example using the apparatus shown in FIG. 3a is shown below. This is an example in which the present invention is applied to a positive non-consumable electrode type arc welding method. A high frequency ignition type was used as the ignition plasma generation method.

Ignition plasma generation circuit side: Plasma power supply: DC droop characteristics, set current value 15A, plasma gas flow rate: 3.0/min: Ar Sub-electrode: Tungsten with 2% thorium, ds = 1.0mmφ, Ds = 1.0mmφ, Lt = 1.0 mm, Lp=1.0mm Arc electric circuit side: Arc power source: DC drooping characteristics, set current value 50A,
No-load voltage 50V, shielding gas flow rate: 20/min: Ar Main electrode: Tungsten containing 2% thorium, arc ignited 100 times continuously under the following conditions: Dm = 1.6mmφ, La = 2.0mm, Lb = 5mm, Lc = 6mm. I tried this, but the arc ignited stably in each case. Furthermore, no noise was observed during arc ignition. The instrument side equipment or control device used at this time was of the type with a built-in microcomputer, but as a matter of course, no malfunctions occurred.

In addition, La=2.0mm, Lb=6mm and Lc=5mm,
It was confirmed that the arc generated from the main electrode 2 toward the perforated electrode 13 in the area marked with a circle in Figure 2b instantly transitioned to an arc from the main electrode 2 toward the base metal 3. did.

Example 2 An example using the apparatus shown in FIG. 3b is shown below. This is the side in which the present invention is applied to an AC consumable electrode type arc welding method. As the ignition plasma generation method, a high frequency ignition type was used.

Ignition plasma generation circuit side: Plasma power supply: DC droop characteristics, set current value 15A Plasma gas flow rate: 3.0/min: Ar Sub-electrode: Tungsten containing 2% thorium ds = 1.0mmφ, Ds = 1.0mmφ, Lt = 1.0mm, Lp=1.0mm Arc electric circuit side: Arc power source: AC drooping characteristics, short circuit current 300A,
No-load voltage 80V Shielding gas flow rate: 20/min: Ar Main electrode: Solid wire Dm = 3.2mmφ, La = 2mm, Lb = 6mm, Lc = 5mm For wire feeding, arc generation is detected by arc generation detector 26 Thereafter, by driving the feed motor 29 via the feed motor controller 28, feeding was performed at a speed of 1.0 cm/sec after arc ignition.

I tried to ignite the arc 100 times in a row under the above conditions, but the arc ignited stably every time. Furthermore, no noise was observed during arc ignition. The measuring equipment or control device used at this time was one with a built-in microcomputer, but as a matter of course, no malfunctions occurred.

In addition, La=2mm, Lb=6mm, Lc=6mm are the second
It was confirmed that the arc generated from the main electrode 2 toward the perforated electrode 13 in the area marked with a circle in FIG.

[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 arc discharge electric circuit for machining, so that electronic equipment such as a microcomputer can be used. There is no need to take noise countermeasures to the control device. Furthermore, since there is no fear of damage to the measuring equipment, even more precise measurements are possible. In addition, since it is a non-contact type of arc ignition, there is no problem with wear and tear on the non-consumable electrode in arc discharge machining using a non-consumable electrode; Alternatively, there is no problem of uncertainty in ignition due to the condition of the base material surface or large spatter that occurs during ignition, and it has high industrial value.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of the configuration of an arc machining device embodying the present invention and an arc phenomenon occurring at the time. FIG. 2a is a sectional view showing an example of the configuration of an apparatus used to carry out the present invention, and FIG.
2c and 2d are graphs showing the correlation between the positional relationship of the perforated electrode 13 with respect to the main electrode 2 and the arc transition form. Figures 3a and 3b
The figure is a sectional view showing the configuration of an apparatus for carrying out various aspects of the present invention. Figures 4a, 4b and 4
Figure c is a sectional view showing the configuration of an apparatus for generating ignited plasma used in the present invention. 1: Arc power supply, 2: Main electrode, 3: Base material, 6:
Shield cap, 7: Torch, 8: Arc generating electric circuit, 10: Plasma device, 11: Plasma power supply, 12: Sub-electrode, 13: Perforated electrode, 14: High frequency power supply, 15: High frequency bypass capacitor, 1
6: Shield, 17: Noise filter, 18: Ignition plasma generation detector, 26: Arc generation detector, 27: Power supply chip, 28: Motor controller, 29: Motor.

Claims (1)

[Claims] 1. Arc ignition, in which an arc is ignited by injecting ignition plasma toward a cathode into an electric field generated in the vicinity of at least one main electrode and a base material to be processed. In this method, a main electrode and an electrode chip for the main electrode are arranged to face the base material to be processed, and the main electrode is connected to one pole side of the processing power supply through the electrode chip, and the base material is connected to the other pole side. By arranging the auxiliary electrode to face the side surface of the main electrode or the side surface of the electrode chip and connecting the auxiliary electrode and the base metal in common, an electric field is generated from the auxiliary electrode toward the main electrode or the electrode chip. The distance La between the surface and the tip of the main electrode is 0.01 mm to 20 mm, the distance Lb between the side surface of the main electrode and the auxiliary electrode is 0.5 mm to 20 mm, and the distance between the center of the surface of the auxiliary electrode facing the main electrode and the tip of the main electrode is The distance Lc from the auxiliary electrode was 0 mm to 40 mm, and ignition plasma was injected from the vicinity of the auxiliary electrode toward the main electrode or electrode chip, and an arc was first generated from the side of the main electrode or the side of the electrode chip toward the auxiliary electrode. The arc ignition method is characterized in that the cathode spot is then instantaneously moved to the tip of the main electrode to instantaneously ignite an arc between the main electrode and the base metal. 2 The processing power source is a DC power source, and the main electrode is connected to the negative side through the electrode chip, and the base material is connected to the positive side, and the auxiliary electrode is connected to the main electrode or the electrode by grounding the auxiliary electrode and the base material. 2. The arc ignition method according to claim 1, wherein ignition plasma is injected from the vicinity of the auxiliary electrode toward the main electrode or electrode tip while an electric field directed toward the tip is generated. 3. The power source for processing is an AC power source, and the main electrode is connected to one output terminal of the power source through an electrode chip, and the base material is connected to the other output terminal of the AC power source for processing.
By arranging the auxiliary electrode to face the side surface of the main electrode or the side surface of the electrode chip and grounding the auxiliary electrode and the base material, when the main electrode is on the negative side and the base material is on the positive side, the auxiliary electrode The arc ignition method according to claim 1, wherein ignition plasma is injected from the vicinity of the auxiliary electrode toward the main electrode or electrode chip while an electric field is generated from the auxiliary electrode toward the main electrode or electrode chip.