JPH0337832B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an arc ignition method in consumable electrode arc welding.

[Conventional technology]

Traditionally, gas-shielded metal arc welding (MIG
A method called the scratch ignition method has generally been used as the arc ignition method in consumable electrode arc welding such as arc welding, MAG arc welding, CO ₂ arc welding), non-gas shielded arc welding, submerged arc welding, and consumable electrode arc welding. .

Note that the term "consumable electrode" as used herein includes both solid wires and flux-cored wires.

FIG. 2 shows an example of the configuration of an apparatus for carrying out the conventional gas-shielded metal arc welding method. In this case, a welding power source 1 having DC constant voltage characteristics is used.
A welding wire 3 is connected to the anode side of the welding torch 20 through the electrode tip 2 in the welding torch 20, and a base material 4 to be welded is connected to the cathode side, thereby forming a welding electric circuit 9. When the welding start switch is turned on, shielding gas flows through the shielding cap 5 (description of the shielding gas will be omitted in the following explanation), the welding power source 1 is turned on, and the welding wire is fed with no-load voltage applied. The feed controller 7 drives the feed roller 8 to feed the welding wire 3. At the moment the tip of the welding wire 3 contacts the base metal 4, a short-circuit current flows from the welding power source 1 through the electrode tip 2, and the vicinity of the contact part of the welding wire 3 with the base metal 4 melts and ignites an arc. .

According to this scratch ignition method, the welding wire 3
The shape and surface condition of the base material 4, the transient characteristics of the welding power source 1, etc. greatly influence the success or failure of arc ignition. To explain this in detail, the tip of the welding wire 3 may have become spherical due to crater treatment at the end of the previous welding, or the tip of the welding wire 3 may have been exposed to the atmosphere at high temperatures and covered with an oxide film. or even the base material 4 to be welded.
It actually occurs that the surface of the material is covered with an oxide film. At this time, the contact resistance between the welding wire 3 and the base metal 4 varies greatly under the influence of the above factors. When the arc is ignited, a short-circuit current determined by this contact resistance and the transient characteristics of the welding power source 1 flows, and the vicinity of the contact part of the welding wire 3 with the base material 4 is heated, fused, and the arc is ignited. A large variation in contact resistance greatly affects the state of heat generation near the contact portion of the welding wire 3 with the base metal 4, and accordingly makes arc ignition uncertain.

[Problem that the invention seeks to solve]

As explained above, the scratch ignition method has the disadvantage that arc ignition tends to fail.

On the other hand, even if the arc is successfully ignited,
When the welding wire 3 near the contact point with the base metal 4 fuses due to short-circuit current, large spatters are generated and adhere to the base metal 4, so an extra process is required to remove them, and the welding This led to increased costs.

In order to improve this, Japanese Patent Application Laid-Open No. 139285/1983 proposes to apply a high frequency voltage between the welding wire 3 and the base metal 4 without making the welding wire 3 and the base metal 4 contact. This causes dielectric breakdown,
A method has been proposed in which the arc is stably ignited in a non-contact manner and the welding wire 3 is fed after the arc is ignited.

However, when high-frequency voltage is used to ignite the arc, electromagnetic noise is generated due to the high frequency, which may malfunction or damage various peripheral electronic devices, including microcomputers built into automatic welding equipment. Therefore, it was necessary to take special measures against high-frequency noise, 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, in the consumable electrode type arc welding method, a non-contact type arc ignition method using a high frequency voltage is not generally popular.

Various other improvements are also being considered, but
A definitive method has not yet been established.

The present invention is a consumable electrode type arc welding method that enables stable arc ignition in a non-contact manner and prevents peripheral electronic equipment, control equipment, etc. from malfunctioning or being damaged due to arc ignition. The purpose of this invention is to provide an arc ignition method in accordance with the law.

[Means for solving problems]

The gist of the present invention is to inject plasma into the electric field generated around the consumable electrode and the base material toward the cathode,
The present invention relates to an arc ignition method in consumable electrode arc welding, which is characterized by igniting the arc in a non-contact manner.

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

[Effect]

First, FIG. 1a shows the configuration of a welding apparatus that embodies one embodiment of the present invention when gas-shielded metal arc welding is used. In Figure 1a, 1
is a welding power source having DC constant voltage characteristics, a welding wire 3 is connected to its anode side through an electrode tip 2 in a welding torch 20, and a base material 4 to be welded is connected to its cathode side. , 2, 3, 4 is formed.

Further, a plasma nozzle 13 and a tungsten electrode 12 are arranged near the welding torch 20, and a tungsten electrode 12 is placed on the cathode side of the plasma device 10.
A plasma nozzle 13 is connected to each anode side,
A plasma jet generation circuit 19 consisting of 10, 12, and 13 is formed.

By turning on the welding power source 1, an electric field is formed between the welding wire 3 and the base metal 4 from the welding wire 3 toward the base metal 4. In this state, plasma gas is supplied into the plasma nozzle 13 (description of the plasma gas will be omitted in the following explanation), the plasma device 10 is turned on, plasma is generated using the plasma jet generation circuit 19, and the plasma is generated. Plasma is injected toward material 4.

At this time, the positive ions in the plasma injected into the electric field are accelerated by the electric field, collide with the base material 4, raise the temperature of the collision part, and form a cathode spot. Once the cathode spot is formed, the arc is easily ignited by the voltage of the welding power source 1.

When the arc ignites, the arc ignition detector 6 detects the arc ignition, and the welding wire feed control device 7 rotates the feed roller 8 in synchronization with the signal from the arc ignition detector 6. supply welding wire.

FIG. 1b shows an apparatus configuration for implementing another embodiment of the invention. Normally, in gas shield metal arc welding, the welding wire 3 is made positive, but this embodiment shows the possibility of application to the case where the welding wire 3 is made negative.

In Fig. 1b, 1 is a welding power source having DC constant voltage characteristics, and a welding torch 2 is connected to the cathode side of the welding power source.
A welding wire 3 is connected through the electrode tip 2 in the anode, and the base material 4 to be welded is connected to the anode side.
A welding electric circuit 9 consisting of 1, 2, 3, and 4 is formed. Furthermore, welding wire 3 or electrode tip 2
A plasma nozzle 13 and a tungsten electrode 12 are arranged near the plasma device 10, with the tungsten electrode 12 on the cathode side and the plasma nozzle 1 on the anode side.
3 are connected to each other to form a plasma jet generation circuit 19 consisting of 10, 12, and 13. Furthermore, the plasma nozzle 13 and the base material 4 are connected.

By turning on the welding power source 1, an electric field is formed between the welding wire 3 (electrode tip 2) and the plasma nozzle 13 from the plasma nozzle 13 toward the welding wire 3 (electrode tip 2). In this state, the plasma device 10 is turned on, plasma is generated using the plasma jet generation circuit 19,
Plasma is injected toward the welding wire 3 (electrode tip 2). At this time, the positive ions in the plasma injected into the electric field are accelerated by the electric field, and the welding wire 3
(electrode chip 2), the temperature of the collision part increases and a cathode spot is formed. Once the cathode spot is formed, the arc is easily ignited by the voltage of the welding power source 1. At this time, the arc initially
The welding wire 3 (electrode tip 2) is ignited toward the plasma nozzle 13, but immediately moves from the welding wire 3 (electrode tip 2) to the base material 4.

When the arc ignites, the arc ignition is detected by the arc ignition detector 6, and the welding wire feed control device 7
Then, the feed roller 8 is rotated in synchronization with the signal from the arc ignition detector 6 to feed the welding wire 3.

By a similar method, it is possible to stably ignite the arc in a non-contact manner in non-gas shielded arc welding and submerged arc welding.

According to the present invention, it is possible to ignite the arc in a non-contact manner in electrodeless arc welding, and the state of the welding wire tip (shape, presence or absence of oxide film, etc.) or the state of the base material to be welded ( (presence or absence of oxide film, etc.) has little effect on arc ignition.
Moreover, since the arc is ignited in a non-contact manner, there is no generation of large spatter due to short circuit current, which is a problem with the scratch ignition method.

Moreover, since the arc can be ignited without using a power source such as a high-frequency power source that serves as an electromagnetic nozzle source in the welding electric circuit 8, a device that measures electrical signals such as arc voltage can be directly connected. Moreover, there is no fear of malfunction or damage to the control device due to electromagnetic noise.

Further, according to the present invention, the plasma jet circuit 1
9, generating a low current plasma jet of about 5 to 30 A, and injecting it for a short time of about 0.01 to 1 second is sufficient to ignite the arc. Moreover, since the gas required to generate the plasma jet is only the plasma gas and no shielding gas is required, the plasma nozzle 13 can be made extremely compact.

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

Further, since the plasma jet for arc ignition is required to be used only for a short time with a low current, wear and tear on the tungsten electrode 12 and the plasma nozzle 13 is extremely slight.

The outline of the present invention has been described above.

Next, a method of igniting the plasma device 10 and plasma jet circuit 19 used in FIGS. 1a and 1b will be explained with reference to FIGS. 3 and 4.

FIG. 3 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;
A tungsten electrode 12 is connected to the cathode side, and a plasma nozzle 13 is connected to the anode side, thereby forming a plasma jet circuit 19 consisting of a plasma power source 11, a tungsten electrode 12, and a plasma nozzle 13.

With the plasma current 11 turned on and the no-load voltage applied, the tungsten electrode 12 is manually operated.
A device that attempts to ignite the plasma jet by drawing the tungsten electrode 12 away from the plasma nozzle 13 after contacting and short-circuiting the plasma nozzle 13 using electric, bimetal, or spring-loaded means to cause a short-circuit transient current to flow. It is.

FIG. 4 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, a tungsten 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. Plasma power supply 11, tungsten electrode 1
2. A plasma jet circuit 19 is formed by a plasma nozzle 13, a high frequency power source 14, and a high frequency bypass capacitor 15.

In this circuit, a high frequency voltage is applied between a tungsten electrode 12 and a plasma nozzle 13 by a high frequency power source 14 to cause a spark discharge and dielectric breakdown, and then a current is supplied by a plasma power source 11 to ignite the arc. It is something to do.

Electromagnetic noise generated by the use of high-frequency voltage can cause malfunctions and damage to precision electronic equipment, which is a problem in the field of non-consumable electrode arc welding such as TIG welding. In this case, electromagnetic noise can be easily and completely suppressed by covering the plasma jet circuit 19 with the shield 16 and contacting the external power source through the noise filter 17, so that no problem arises.

In FIG. 4, the high frequency voltage generated by the high frequency power source 14 is used to ignite the plasma jet circuit 19, but any power source capable of supplying the same voltage can be incorporated into the plasma jet circuit 19. In fact, it is possible to ignite the plasma jet in the same way by using the capacitor discharge voltage from the capacitor power source or the surge voltage generated when the current is cut off.

Examples according to the present invention will be described below.

Example 1 Figures 5a and 5b show an example in which the present method is applied to arc ignition in reverse polarity gas-shielded metal arc welding. Incidentally, FIG. 5a shows the entire apparatus, and FIG. 5b shows the plasma jet generation circuit.

Plasma jet side: No-load voltage of plasma power supply 11 100V, plasma jet current 10A, plasma gas flow rate 3/min・Ar, D=1.0mm, lt=1.0mm, lp=1.2mm, ds=1.0mm, welding Electrical circuit side: Welding power supply 1 has a no-load voltage of 47V and a droop degree of 0.007V/
It has the characteristics of A.

Plasma was injected for 0.1 seconds under the following conditions: shield gas flow rate 20/min・Ar, wire feeding speed 10 m/min, dm = 1.2 mm (solid wire) la = 2 mm, lb = 5 mm, lc = 5 mm, θ = 45 deg. Arc ignition was attempted 100 times in a row, and arc ignition was extremely stable in each case. Furthermore, no large spatter was generated during arc ignition.

Example 2 FIG. 6 shows an example in which the present method is applied to arc ignition in positive polarity gas-shielded metal arc welding. The same plasma jet generating circuit as shown in FIG. 5b was used.

Welding electric circuit side: Welding power supply 1 has a no-load voltage of 47V and a droop degree of 0.007V/
It has the characteristics of A.

Shielding gas flow rate: 20/min, CO ₂ wire feeding speed: 10 m/min, dm = 1.2 mm (solid wire) Plasma is injected for 0.1 seconds under the conditions of la = 2 mm, lb = 5 mm, lc = 5 mm, and the arc point is repeated 100 times in a row. We tried arc ignition, and in each case we were able to achieve extremely stable arc ignition.

Furthermore, no large spatter was generated during arc ignition.

Example 3 FIG. 7 shows an example in which the present method is applied to arc ignition in reverse polarity non-gas shielded arc welding. The plasma jet generating circuit used was the same as that shown in FIG. 5b.

Welding electric circuit side: Welding power supply 1 has a no-load voltage of 47V and a droop degree of 0.007V/
It has the characteristics of A.

Wire feeding speed: 10 m/min, dm = 1.6 mm (flux-cored wire), la = 2 mm, lb = 5 mm, lc = 5 mm, θ = 45 deg, plasma was injected for 0.1 seconds and the arc was repeated 100 times in a row. I tried igniting the arc, and in each case I was able to ignite the arc extremely stably. Furthermore, no large spatter was generated during arc ignition.

Through the examples 1, 2, and 3 shown above, there was almost no voltage fluctuation of the external power supply during high frequency generation, and furthermore, the measuring equipment or control device used at this time was a microcomputer built-in type. However, no malfunctions due to high frequency noise occurred.

〔Effect of the invention〕

As described in detail above, according to the present invention, the arc can be ignited without contacting the base metal and the welding wire. It is simpler than the arcing method and has excellent arc ignition stability. Furthermore, since the arc is ignited in a non-contact manner, there is no need to use means that cause noise, such as a high-frequency power supply, in the welding electric circuit, so control devices and measurement using electronic devices such as microcomputers are not required. There is no risk of malfunction or damage to the device. Furthermore, since no short-circuit current flows, large spatters that occur during ignition can be prevented, and the process for removing spatters can be omitted, improving work efficiency.

[Brief explanation of drawings]

FIGS. 1a and 1b are block diagrams each showing the configuration of an apparatus for carrying out one embodiment of the present invention. FIG. 2 is a schematic diagram showing a conventional example. FIGS. 3 and 4 are block diagrams showing the configuration of an arc ignition plasma jet generating circuit used in carrying out the present invention. Figures 5a and 5b
6 and 7 are block diagrams each showing a specific arrangement of an apparatus for carrying out one embodiment of the present invention. 1: Welding power source, 2: Electrode chip, 3: Welding wire, 4: Base metal, 5: Shield cap, 6: Arc ignition detector, 7: Welding wire feeding control device,
8: Feeding roller, 9: Welding electric circuit, 10: Plasma device, 11: Plasma power source, 12: Tungsten electrode, 13: Plasma nozzle, 14: High frequency power source, 15: High frequency bypass capacitor, 1
6: Shield, 17: Noise filter, 19: Plasma jet generation circuit, 20: Welding torch.

Claims (1)

[Claims] 1. A consumable electrode is connected to the negative side of a DC welding power source, a base material is connected to the positive side, and an auxiliary electrode is arranged so as to face the side surface of the consumable electrode, and the auxiliary electrode and the base material are connected. 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 consumable electrode while generating an electric field from the auxiliary electrode toward the consumable electrode. arc ignition method. 2 Connect the consumable electrode to the positive side of the DC welding power source and the base material to the negative side, and inject ignited plasma from near the consumable electrode toward the base material while generating an electric field from the consumable electrode toward the base material. A method for igniting an arc in consumable electrode arc welding, which is characterized by igniting an arc.