JPH10156535A - Arc welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely execute arc starting or arc re-spotting without making an electrode in contact with an object to be welded by originating ultraviolet rays onto the electrode, the object to be welded or the gap between them at the time of starting arc or arc re-spotting. SOLUTION: When a start switch 15 is closed after a power source switch 2 is closed, a main switch 3 inside a welding power source 7 is closed, the power from an alternating current power source 1 is made in a direct current power smoothed at a rectifying circuit 5 and a direct current reactor 6 after properly converting the voltage at a transformer 4, and it is supplied between an electrode 21 and an object 10 to be welded. In the TIG arc welding method, the electrode 21 becomes a cathode, and the object 10 to be welded becomes the cathode in the MIG arc welding method, when ultraviolet rays 18 are originated onto these cathodes, electron is emitted from the face of cathode caused on optical electron emission. As a result, the electron and ion are increased remarkably in a clearance 22, and the arc is generated easily with the output of the welding power source 7 supplied between the electrode 21 and the object 10 to be welded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding method for easily starting an arc and restriking an arc without bringing an electrode into contact with a workpiece.

[0002]

2. Description of the Related Art Conventionally, in a TIG arc welding method using a non-consumable electrode, when an electrode is brought into contact with a workpiece, not only is the electrode extremely damaged, but also electrode material components adhere to the surface of the workpiece. However, since not only the appearance but also the welding quality is significantly impaired, the arc is generated without bringing the electrode into contact with the workpiece at the start of the arc. For that purpose, at the time of arc start, a state where a certain gap is provided between the electrode and the workpiece, and a high-frequency high voltage of several thousand volts is supplied between the electrode and the workpiece, A high-frequency spark discharge is generated between the two, and an arc is induced by the spark discharge.

In the MIG arc welding method using a consumable electrode wire, an arc is generated by bringing an electrode into contact with a workpiece, but when the current value is low, the electrode and the workpiece are short-circuited. Arc start may fail. Therefore, even in the MIG arc welding method, a method in which a constant gap is provided between the electrode and the workpiece and a high-frequency high voltage is supplied between the electrode and the workpiece to start the arc. Used.

FIG. 5 is a connection diagram showing an example of an apparatus for performing a conventional arc welding method. In FIG. 1, reference numeral 1 denotes an AC power supply, which is a single-phase commercial AC power supply or a three-phase commercial AC power supply. Reference numeral 2 denotes a power switch, 3 denotes a main switch, and 4 denotes a transformer, which converts the output of the AC power supply 1 into electric power suitable for arc machining. The output of transformer 4 is rectified and smoothed by rectifier circuit 5 and DC reactor 6. A high-frequency bypass circuit 23 prevents a high-frequency high voltage generated from a high-frequency high-voltage generating circuit 12 described later from flowing into the welding power supply 7. Welding power source 7
Is composed of a main switch 3, a transformer 4, a rectifier circuit 5, a DC reactor 6, and a high-frequency bypass circuit 23.
Reference numeral 12 denotes a known high-frequency high-voltage generation circuit using a capacitor, a discharge gap, and the like. The output of the circuit is superimposed on the output of the welding power source 7 via the coupling coil 8. Reference numeral 9 denotes a welding torch, reference numeral 21 denotes an electrode, reference numeral 10 denotes a workpiece, and an arc is generated in a gap 22 between the electrode 21 and the workpiece 10 to perform welding. 11 is an output current detection circuit, 13 is an auxiliary switch, 14 is an AND circuit, and 15 is a start switch. The AND circuit 14 outputs a closing command signal to the auxiliary switch 13 when the output signal of the start switch 15 and the signal obtained by inverting the output signal of the output current detection circuit 11 are simultaneously at the high level.

When the start switch 15 is closed after the power switch 2 is closed, the main switch 3 in the welding power source 7 is closed, and the power from the AC power source 1 is converted into a voltage by the transformer 4 as appropriate. The DC power is smoothed by the DC reactor 6 and supplied between the electrode 21 and the workpiece 10. At this time, since an arc has not yet occurred, the output signal of the output current detection circuit 11 is at a low level. A high level signal is output, and the auxiliary switch 13 is closed. As a result, the high-frequency high-voltage generating circuit 12 is activated, and the high-frequency high voltage output from this circuit is superimposed on the output of the welding power source 7 via the coupling coil 8 and supplied between the electrode 21 and the workpiece 10. Is done. Then, the insulation of the gap 22 between the electrode 21 and the workpiece 10 is broken by the high frequency high voltage, and a spark discharge is generated, thereby causing an arc. When this arc is generated and the welding current flows, the output of the output current detection circuit 11 becomes high level, and the output signal of the AND circuit having this inverted output as one input is inverted to low level, and the auxiliary switch 13 Open, high-frequency high-voltage generation circuit 12
Output stops.

[0010]

When these high frequencies are used, there are the following disadvantages. The first is the problem of radio interference to communication equipment due to high-frequency radiation.
Is caused by malfunction of various control devices due to the incorporation of high frequency into the welding power supply and control power supply line and damage to semiconductor circuit elements. It is thought that a line filter should be inserted to prevent high-frequency mixing into the power supply line, but in practice only the high-frequency power to the control cable and power supply line is effective without reducing the supply of high-frequency power to the electrodes It is very difficult to attenuate the filter, and the substantial effect of inserting the filter is small. In addition, there is no method other than electromagnetic shielding of the entire workplace for the radio frequency radiated into the air, and this is also difficult to realize. Therefore, there is no practical means to eliminate these high-frequency obstacles other than reducing the high-frequency energy to be supplied, but reducing the high-frequency energy makes high-frequency sparks less likely to occur and significantly reduces the meaning of supplying high-frequency high voltage. Will be done.

Further, even if a sufficient high-frequency high voltage is supplied between the electrode and the workpiece, if the tip of the electrode is cleaned and the oxide film disappears, electron emission (electric field) obtained by supplying the high voltage is obtained. (Electron emission due to emission) decreases, and due to poor insulation or distributed capacity of the welding torch cable, high frequency leaks from the cable to the ground and the voltage actually supplied to the tip of the electrode decreases, etc. Discharge does not occur between the workpiece and the workpiece, and there is a disadvantage that arc start fails. In particular, failure of the arc start in the automatic welding device causes a reduction in the operation rate of the line.

[0020]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the conventional welding method, the present invention provides a method for starting or closing an arc switch, starting an arc and detecting an output current, or when the arc is extinguished. By the time the arc is re-ignited,
By irradiating the electrode and the workpiece or the gap with ultraviolet rays, the electron emission necessary for arc start or arc re-ignition is obtained by photoelectron emission, and no high voltage is supplied or the output voltage is relatively low, For example, the present invention proposes an arc welding method that can easily and reliably perform an arc start or an arc re-ignition simply by supplying a high voltage that does not generate a spark discharge.

[0030]

FIG. 1 is a connection diagram showing an example of an embodiment of the present invention. In the figure, reference numeral 19 denotes an ultraviolet light emitting lamp, which emits ultraviolet light 18 to the electrode 21 and the workpiece 10.
Alternatively, the light is irradiated to the gap 22. Reference numeral 20 denotes a power supply for an ultraviolet light emitting lamp, which supplies power to the ultraviolet light emitting lamp 19 to emit light while the output signal of the AND circuit 14 is at a high level. The other components having the same functions as those of the apparatus for performing the conventional arc welding method shown in FIG.

In FIG. 1, when the start switch 15 is closed after the power switch 2 is closed, the main switch 3 in the welding power source 7 is closed, and the power from the AC power source 1 is appropriately converted by the transformer 4 into a voltage. Later, the DC power becomes smoothed by the rectifier circuit 5 and the DC reactor 6, and the electrode 21 and the workpiece 10
Is supplied between At this time, since an arc has not yet occurred, the output signal of the output current detection circuit 11 is at a low level. A high level signal is output, and the power supply 20 for the ultraviolet light emitting lamp
Activated by the high level signal of the ND circuit 14 to supply power to the ultraviolet light emitting lamp 19,
9 irradiates the ultraviolet rays 18 to the electrode 21 and the workpiece 10 or the gap 22 therebetween. In the TIG arc welding method, the electrode 21 serves as a cathode, and in the MIG arc welding method, the workpiece 10 serves as a cathode. When the ultraviolet rays 18 are irradiated on these cathodes, electrons are emitted from the cathode surface by photoelectron emission.
As a result, electrons and ions are significantly increased in the gap 22, and an arc is easily generated by the output of the welding power source 7 supplied between the electrode 21 and the workpiece 10. When an arc is generated and a welding current flows, the output of the output current detection circuit 11 goes to a high level, and the output signal of the AND circuit 14 having this inverted output as one input is inverted to a low level, so that the output signal for the ultraviolet light emitting lamp is The output of the power supply 20 stops, and the ultraviolet light emitting lamp 19 stops irradiation of the ultraviolet light 18.

The effects of ultraviolet rays on the human body can cause inflammation of the eyes when viewed directly, cause sunburn when they hit the skin, and cause skin cancer when irradiated in large amounts. In the apparatus for carrying out the arc welding method of the present invention, ultraviolet rays 18 are emitted only for a moment from when the start switch 15 is closed to when an arc is generated, so that there is almost no effect on the human body as compared with continuous irradiation. In particular, at the start of welding, the worker wears a light-shielding surface and wears protective equipment. Therefore, even if the worker is instantaneously irradiated with the ultraviolet light 18 at this time, the worker is not affected at all.

Next, an appropriate wavelength of the ultraviolet light to be irradiated in the present invention is determined. When ultraviolet light is applied to the surface of the cathode or gas molecules filling the gap 22, the electrons can escape from the metal atoms or gas molecules so that the electrons can cross the barrier of a certain potential determined by these substances. It is necessary that the light energy is larger than the required energy, that is, the work function φ [eV]. The energy of light is proportional to the frequency ν [Hz] of light, and is expressed as hν [J] when a proportional constant is h. Here, h is called Planck's constant, and h = 6.626 × 10 ⁻³⁴ [J · S]. Assuming that the electron charge is e, electron emission is performed if (eφ ≦ hν). Next, at the wavelength of ultraviolet light, the longest wavelength at which electrons are emitted from metal atoms is defined as the limit wavelength λ0.
[Mm], the limit wavelength λ0 is given by λ0 = (c / ν) ≦ (ch / eφ) [mm], where c is the speed of light. c = 2.998 × 10 ⁸ [m / s] e = 1.60 × 10 ⁻¹⁹ [C] Therefore, when the limit wavelengths of various electrodes are obtained by using this equation, they are used in the TIG arc welding method. Of pure dangsten (work function is 4.54 [eV])
[Nm], tungsten containing thorium (work function is 2.
60 [eV]) is 477 [nm], and aluminum (work function is 3.74) used in the MIG arc welding method.
[EV]), 331 [nm], iron (work function is 4.3).
6 [eV]), it is 284 [nm].

As the ultraviolet light emitting lamp 19, there is a germicidal lamp which is generally available on the market.
This is a low-pressure mercury lamp that uses quartz glass having a high transmittance of 4 [nm] ultraviolet light and does not apply a fluorescent paint to the inner wall of the glass tube. When the above-mentioned metal was irradiated to the electrode 21 or the workpiece 10 using this germicidal lamp, the arc start property was good. On the other hand, when a black light that emits light with a wavelength of 365 [nm] at the center (this is a low-pressure mercury lamp whose glass tube is made of black ultraviolet transmitting glass that blocks visible light), the arc-starting property was not good. Further, in order to emit more electrons from metal atoms, it is better that the wavelength of the ultraviolet ray is shorter. However, if the wavelength is less than 200 [nm], the absorption in the air increases, which is not practical. Therefore, the wavelength is 200 to 300 [n
m] is suitable.
In order to emit ultraviolet light in a pulsed form, it is recommended to use a flash lamp using ultraviolet transmitting glass by modifying the strobe for photography, and use a shielding gas from when the start switch is closed until the arc is generated. When the flash lamp is caused to emit light in a pulsed manner at a time when the gas is sufficiently supplied, a more reliable arc start can be performed.

In the case of using the above-mentioned ultraviolet ray having a wavelength of 200 to 300 [nm], the shielding gas filling the gap 22 is, for example, argon having a relatively low ionization voltage and the ionization voltage is 15.75 [eV]. It is difficult to ionize this directly with ultraviolet light. However, irradiation of ultraviolet rays has an effect of exciting these gas molecules and facilitating ionization.

In the apparatus for carrying out the arc welding method of the present invention shown in FIG. 1, it is necessary to start discharge only by electron emission by irradiating ultraviolet rays. It is necessary to increase the capacity of the power source 20 for the ultraviolet light emitting lamp. Therefore, if a high-frequency high voltage or a DC high voltage at a lower level than that shown in the apparatus for performing the conventional arc welding method shown in FIG. 5 is supplied together with the ultraviolet light, other equipment will not be damaged. Arc start can be easily performed with a high frequency high voltage or a DC high voltage. Next, examples of these embodiments will be described with reference to FIGS.

FIG. 2 is a connection diagram showing an example of another embodiment of the present invention. In the figure, those having the same functions as those of the apparatus shown in FIGS. 1 and 5 are denoted by the same reference numerals. In FIG. 2, when the start switch 15 is closed after the power switch 2 is closed, the main switch 3 in the welding power source 7 is closed and the AC power source 1 is closed.
Is converted into a DC power by the rectifier circuit 5 and the DC reactor 6 after being appropriately converted in voltage by the transformer 4 and supplied between the electrode 21 and the workpiece 10. At this time, since the arc has not yet occurred, the output signal of the output current detection circuit 11 is at a low level, and the AND circuit 14 which inverts the output signal and receives the input signal has a high level because the two inputs are at a high level. Outputs a high level signal. As a result, the auxiliary switch 13 is closed by the high-level signal of the AND circuit 14, whereby the high-frequency high-voltage generating circuit 12 is activated to apply the high-frequency high voltage to the coupling coil 8.
, And is supplied between the electrode 21 and the workpiece 10. At the same time as the high-frequency high-voltage generating circuit 12 starts outputting, the ultraviolet light emitting lamp power supply 20 is activated by the high level signal of the AND circuit 14 and supplies power to the ultraviolet light emitting lamp 19. UV light 18 is applied to electrode 21 and workpiece 1
0 or the gap 22 is irradiated. UV light 18 is in the gap 22
When it hits a shielding gas molecule such as argon existing in
This is excited to facilitate ionization. Electrons are emitted from the electrode 21 or the cathode surface of the workpiece 10, and as a result, electrons and ions are significantly increased in the gap 22, and the welding power source 7 in which a high-frequency high voltage is superposed between the electrode 21 and the workpiece 10.
Of the electrode 21 and the workpiece 10
The insulation of the gap 22 between them is easily destroyed and a spark discharge occurs, which induces an arc. When this arc is generated and the welding current flows, the output current detection circuit 11
Becomes high level, the output signal of the AND circuit 14 having this inverted output as one input is inverted to low level, the auxiliary switch 13 is opened, and the high frequency high voltage generation circuit 12
Output stops. When the output of the AND circuit 14 is inverted to a low level, the power supply 2
0 is stopped, and the ultraviolet light emitting lamp 19 is turned off.
The irradiation of is stopped.

FIG. 3 is a connection diagram showing an example of another embodiment of the present invention. In the figure, reference numeral 17 denotes a DC high voltage generating circuit having a no-load voltage higher than the no-load voltage of the welding power source 7, and an output of the high-voltage diode 16 connected to the welding power source 7 in series. They are connected in parallel. The high voltage diode 16 is provided to bypass the output of the welding power source 7 to the DC high voltage generating circuit 17 during welding. The output of the auxiliary switch 13 is input to a power source 20 for an ultraviolet light emitting lamp. The other components having the same functions as those of the device shown in FIG. In FIG.
When the start switch 15 is closed after the power switch 2 is closed, the main switch 3 in the welding power source 7 is closed, and the power from the AC power source 1 is appropriately converted in voltage by the transformer 4 and then the rectifier circuit 5 and the DC reactor. The DC power becomes smoothed at 6 and is supplied between the electrode 21 and the workpiece 10. At this time, since the arc has not yet occurred, the output signal of the output current detection circuit 11 is at a low level, and the AND circuit 14 which inverts the output signal and receives the input signal has a high level because the two inputs are at a high level. Outputs a high level signal. As a result, the auxiliary switch 13 is closed by the high-level signal of the AND circuit 14, whereby the DC high-voltage generation circuit 17 is closed.
Starts and superimposes the DC high voltage on the output of the welding power source 7,
It is supplied between the electrode 21 and the workpiece 10. The power supply 20 for the ultraviolet light emitting lamp is also activated by closing the auxiliary switch 13, and supplies power to the ultraviolet light emitting lamp 19,
The ultraviolet light emitting lamp 19 irradiates the ultraviolet light 18 to the electrode 21 and the workpiece 10 or the gap 22 therebetween. When the ultraviolet light 18 strikes a shielding gas molecule such as argon existing in the gap 22, it is excited and ionized easily. Electrons are emitted from the electrode 21 or the cathode surface of the workpiece 10, and as a result, electrons and ions are significantly increased in the gap 22, and
Since the output of the welding power source 7 in which a DC high voltage is superimposed is supplied between the electrode 21 and the workpiece 1,
The insulation of the gap 22 between 0 and 0 is easily destroyed and a spark discharge occurs, which induces an arc. When this arc is generated and the welding current flows, the output current detection circuit 1
1 becomes high level, the output signal of the AND circuit 14 having this inverted output as one input is inverted to low level, the auxiliary switch 13 is opened, and the DC high voltage generating circuit 17 is opened.
Output stops. Further, when the auxiliary switch 13 is opened, the output of the power supply 20 for the ultraviolet light emitting lamp is stopped, and the irradiation of the ultraviolet light 18 by the ultraviolet light emitting lamp 19 is stopped.

FIG. 4 is a connection diagram showing an example of another embodiment of the present invention. In the figure, reference numeral 24 denotes a welding power source which outputs AC power. When arc welding is performed by AC output, the arc is extinguished each time the welding current becomes zero. Therefore, in order to continue welding, an arc in the opposite direction must be ignited every time the polarity is reversed. Therefore, the high-frequency high-voltage generating circuit 12 and the power supply 2
0 is inputting the secondary output of the transformer 4 of the welding power source 24. The other components having the same functions as those of the device shown in FIG.

In FIG. 4, when the start switch 15 is closed after the power switch 2 is closed, the main switch 3 in the welding power source 24 is closed, and the power from the AC power source 1 is appropriately converted in voltage by the transformer 4. , And between the electrode 21 and the workpiece 10. At this time, since a no-load voltage appears at the output terminal of the welding power source 24, the input voltage of the high-frequency high-voltage generating circuit 12 rises, and the high-frequency high-voltage generating circuit 12 starts up and outputs a high-frequency high voltage. Is superimposed on the output of the welding power source 24 via the coupling coil 8 and supplied between the electrode 21 and the workpiece 10. In addition, the input voltage of the ultraviolet light emitting lamp power supply 20 also increases due to the no-load voltage appearing at the output terminal of the welding power supply 24, and the ultraviolet light emitting lamp power supply 20 is activated to supply power to the ultraviolet light emitting lamp 19.
To supply. The ultraviolet light emitting lamp 19 irradiates the ultraviolet light 18 to the electrode 21 and the workpiece 10 or the gap 22 therebetween, and when the ultraviolet light 18 strikes a shielding gas molecule such as argon existing in the gap 22, excites it and makes it easy to be ionized. . Electrons are emitted from the electrode 21 or the cathode surface of the workpiece 10. As a result, electrons and ions are significantly increased in the gap 22, and a welding power source 24 in which a high-frequency high voltage is superposed between the electrode 21 and the workpiece 10. Is supplied, the insulation of the gap 22 between the electrode 21 and the workpiece 10 is easily broken to generate a spark discharge, thereby inducing an arc.

When this arc is generated, the output voltage of the welding power supply 24 decreases in accordance with the drooping characteristic, so that the input voltages of the high-frequency high-voltage generating circuit 12 and the power supply 20 for the ultraviolet light emitting lamp become insufficient. As a result, the high-frequency high-voltage generation circuit 1
2 stops the output of the high-frequency high voltage, the ultraviolet light emitting lamp power supply 20 stops the power supply to the ultraviolet light emitting lamp, and the ultraviolet light emitting lamp 19 stops the irradiation of the ultraviolet light 18. Thereafter, when the polarity is reversed, when the welding current becomes zero and the arc is extinguished once, a no-load voltage appears at the output terminal of the welding power source 24. At this time, the input voltages of the high-frequency high-voltage generating circuit 12 and the power supply 20 for the ultraviolet light emitting lamp increase, and as a result, the output of the welding power supply 24 in which the high-frequency high voltage is superimposed between the electrode 21 and the workpiece 10 is supplied. At the same time, the ultraviolet rays 18 are irradiated to the electrode 21 and the workpiece 10 or the gap 22 therebetween, and the arc is regenerated. Start switch 1
These operations are repeated until 5 is opened.

In the apparatus for carrying out the arc welding method of the present invention shown in FIGS. 1 to 4, the power source 20 for the ultraviolet light emitting lamp may be provided separately from the welding power source 7 or 24. It may be incorporated in Further, it is convenient that the ultraviolet light emitting lamp 19 has a structure in which the irradiation direction or irradiation range of the ultraviolet light 18 can be changed. Furthermore, when the output voltage is detected instead of detecting the output current and the output voltage from when the start switch 15 is closed until the arc is generated or when the arc is extinguished and the arc is reignited is the no-load voltage, Ultraviolet rays 18 may be applied to supply a high voltage.

[0060]

As described above, the arc welding method of the present invention does not supply any high voltage by irradiating the electrode and the workpiece or the gap between the electrode and the workpiece at the time of starting the arc or re-igniting the arc. The arc start or arc re-ignition can be performed easily and reliably by supplying a high voltage with a low output voltage. Intrusion or induction disturbance can be completely prevented.

In general, the tip of a tungsten electrode is worn out when arc start and welding are repeated, and it becomes difficult to start arc. However, in the present invention, the electron emission from the electrode does not rely only on the emission (field emission) by supplying a high voltage as in an apparatus for performing a conventional arc welding method, but utilizes photoelectron emission or excitation by ultraviolet rays. Therefore, the sharpness of the electrode tip does not significantly affect the arc start. Therefore, the arc can be started even if the tip of the electrode is consumed to some extent, so that the number of times of polishing the electrode can be reduced and the working efficiency can be improved. Further, in the present invention, since the ultraviolet light emitting lamp is only turned on at the time of starting the arc or at the time of re-ignition of the arc, the life of the ultraviolet light emitting lamp is significantly prolonged, and the frequency of lamp replacement is reduced. There are advantages.

[Brief description of the drawings]

FIG. 1 is a connection diagram illustrating an example of an embodiment of the present invention.

FIG. 2 is a connection diagram showing an example of another embodiment of the present invention.

FIG. 3 is a connection diagram showing an example of another embodiment of the present invention.

FIG. 4 is a connection diagram showing an example of another embodiment of the present invention.

FIG. 5 is a connection diagram showing an example of an apparatus for performing a conventional arc welding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Power switch 3 Main switch 4 Transformer 5 Rectifier circuit 6 DC reactor 7 Welding power supply 8 Coupling coil 9 Welding torch 10 Workpiece 11 Output current detection circuit 12 High frequency high voltage generation circuit 13 Auxiliary switch 14 AND Circuit 15 Start switch 16 High voltage diode 17 DC high voltage generating circuit 18 Ultraviolet light 19 Ultraviolet light emitting lamp 20 Power supply for ultraviolet light emitting lamp 21 Electrode 22 Gap 23 High frequency bypass circuit 24 Welding power supply

Claims (6)

[Claims] 1. An arc welding method for performing an arc start while maintaining a non-contact state between an electrode and a workpiece. An arc welding method that irradiates the gap with ultraviolet light. 2. An arc welding method for starting an arc while maintaining a non-contact state between an electrode and a workpiece. An arc welding method for irradiating an ultraviolet ray to an electrode and a workpiece or a gap between the electrode and a workpiece before ignition. 3. A high voltage is applied between an electrode and a workpiece from an auxiliary power supply during the irradiation of the ultraviolet light.
5. The arc welding method according to 1. 4. The arc welding method according to claim 3, wherein said auxiliary power supply generates a high frequency high voltage of a relatively low voltage that is insufficient for starting an arc by itself. 5. The arc welding method according to claim 3, wherein the auxiliary power source has a no-load voltage higher than a no-load voltage of the welding power source. 6. The wavelength of the ultraviolet light is 200 to 300 [n].
m]. The arc welding method according to any one of claims 1 to 5, wherein