JPS5985900A - Etching method of tungsten electrode - Google Patents

Abstract

PURPOSE:To improve an arc starting characteristic and to stabilize an arc by etching electrolytically the top end of a W electrode bar contg. a thermion emissive material such as ThO2 and ZrO2 in an etching soln. wherein W reacts electrochemically. CONSTITUTION:The top end of a W electrode bar 1 contg. a thermion emissive material such as ThO2 or ZrO2 is dipped in an etching soln. 14 such as an aq. caustic alkali soln. which etches W. Electric current is conducted from a power source 10 to the bar 1 as an anode and a counter electrode 15 as a cathode by using a variable resistance 11 and a switch 12, to etch electrolytically the W on the surface at the top end of the bar 1. Then the thermion emissive material deposits on the surface thereof, whereby the arc starting characteristic in the stage of welding is improved and the arc is stabilized.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a tungsten electrode rod mainly used in TIG arc bath welding, and particularly to a method for improving arc starting. This is what we provide.

[Prior art]

Traditionally, TIG arc welding has been used to weld light alloys, 4I! It is widely used mainly in special steel. A non-consumable tungsten electrode rod is used as the electrode for this welding, and in this case, a tungsten rod containing a small amount of thorium oxide ('rhot) of around 2% is often used. In rare cases, a tungsten rod containing zirconia (zrot) is also used. These tungsten electrode rods containing thermoelectron-emitting substances such as thorium oxide (hereinafter referred to as thorium) and zirconia have superior arc starting performance and stability compared to pure tungsten electrode rods, as well as less wear and tear. has major features.

However, even with these tricks and zirconia-containing tungsten electrodes, the first
As shown in Figure 1(a), the arc 4 does not occur from the tip of the electrode rod 1, but occurs irregularly from the top as shown in Figure 1(b), or if the arc is caused by oxides. The arc may disappear or the arc may disappear.

In particular, in work lines such as arc spot welding and intermittent arc welding where arc starting is frequent, the arc starts and stops repeatedly, so the above phenomenon is extremely likely to occur, and this can cause problems such as welding. Unmelted at the beginning,
This causes welding defects such as insufficient penetration and burn-through. If welding is repeated repeatedly, it may become impossible to start the arc and the welding may be interrupted, even though the tip of the electrode is hardly worn out.

If the electrode rod has a reduced ability to start the arc or is no longer able to start, it must be removed from the torch and either re-ground or replaced with a new one.

When the tip of the torized tungsten electrode rod in such a state is observed with the naked eye, the metallic luster has been lost and the entire surface has a whitish color. Further observation and component analysis of this electrode surface under magnification using a scanning electron microscope revealed that the entire surface was covered with a molten film as shown in Figure 2, giving the impression that it had been coated with cement. Moreover, it was discovered that the Tolya that were originally scattered on the surface had disappeared. From this, the main reason why the arc cannot be started during welding is that the surface of the electrode is gradually covered with a molten film due to the repeated arc creeping phenomenon, and the surface of the electrode is gradually covered with a molten film, and moreover, ) disappeared, and the ability to start the arc was attenuated.

In order to give this electrode rod the ability to start an arc again, it is necessary to expose a new tungsten surface dotted with toria, and for this reason, conventionally, the electrode rod 1 is ground using a grinder 7 as shown in FIG. The tip of the machine was ground. However, in this grinding process, it is troublesome to attach and detach the electrode rod from the torch, and it takes time to grind accurately, and the electrode rod quickly breaks down due to repeated grinding processes. It has the disadvantage of being shorter.

Therefore, if Toria is deposited on the surface of the tip of the electrode by some method, it will be possible to start the arc again from this electrode rod without re-grinding. As a result of various studies on how to do this, we found that applying a corrosion treatment to the surface of the tip of the electrode rod is an extremely effective method.

Techniques for corroding (or electrolyzing) metals have been known for a long time, but most of them are used for purposes such as observing metal structures, anticorrosion treatment of metal products, and refining metal materials. However, corrosion treatment has never been applied to the surface of an electrode rod in order to improve arc starting characteristics during welding (or cutting) work. therefore,
The content of the present invention described below is completely different in purpose and effect from conventional corrosion techniques.

[Purpose of the invention]

The present invention has been made in view of the above, and aims to provide a simple processing method instead of re-grinding an electrode rod, as well as to improve arc starting characteristics and stabilize the arc.

[Summary of the invention]

The present invention involves electrolytically corroding the tip of a tungsten electrode rod for welding containing a thermionic emitting substance such as thorium oxide or zirconia in a corrosive solution in which tungsten undergoes an electrochemical reaction, thereby starting the arc of the electrode rod. I tried to improve my abilities. In addition, the welding power source or the power source installed in the welding machine is used as a power source during the electrolytic corrosion.

[Embodiments of the invention]

The content of the present invention will be specifically explained below with reference to Examples. Fig. 4 is a diagram showing the configuration of a device that performs corrosion treatment on the tip of the electrode rod, where 1 is a tungsten electrode rod containing tungsten used in welding, and 10 is used to electrolytically corrode the tip of the electrode rod 1. As a power source, either direct current or alternating current lightning sources may be used. In the case of a DC power source, the electrode rod 1 is connected to the anode side as shown in the figure. 11 and 12 are power supply 1
This is a variable device and switch that variably controls the zero current (or voltage). 14 is a corrosive liquid consisting of an aqueous solution of caustic alkali, which is placed in a container 13.

As a corrosive liquid, a fallen liquid may be used as long as it can corrode tungsten metal, but since it is not preferable to use chemicals that may cause harm to workers, N is used here because it is easy to handle.
a Caustic alkali aqueous solutions such as OH+ Hz O and KOH+ Ht O are used.

By applying electricity, the corrosive liquid (NaOH + H, 0) 14
An electrolytic reaction occurs between the electrode rod (W+The,) 1 inserted into the solution, and the W on the surface of the electrode rod is dissolved (electrolytic corrosion) by OH- ions. By subjecting the surface of the tip of the electrode rod to corrosion treatment in this manner, tric (Th02) is deposited on the surface, and the ability to emit thermionic electrons is enhanced. As a result, the arc starting characteristics during welding are improved and the arc can be stabilized.

Figure 5 (aJ (b) shows the electrode rod (2% The,
+W) was corroded using the equipment shown in Figure 4, and the corroded surface was examined using a scanning electron microscope.
This is an example of the results of observation and component analysis. Initially, the surface of the tip of this electrode rod was covered with a molten film and the trick had disappeared, but with this corrosion treatment, the tungsten metal was completely corroded as shown in Figure 5(a), and the trick was removed from the surface. is precipitated. Moreover, that trick [-U
It can be seen from Fig. 5 (bl) that much more sulfur was precipitated than the content contained in the material (2% The, -W).As a result, the tip of the electrode rod was Even without re-grinding, the ability to emit thermionic electrons is restored and improved through the precipitation of trike, making it possible to start an arc again from the tip of the electrode. Since a large amount of the trick is deposited on the surface of the tip of the rod, arc transfer from the electrode end becomes easier.

The amount of corrosion when the electrode rod is subjected to corrosion treatment (electrolytic corrosion during welding at a predetermined concentration) is determined by the applied current value (or voltage) and corrosion time, and by controlling these, a trick can be applied to the electrode rod surface. (a thermionic emitting substance) can be arbitrarily precipitated. For example, when the current value is set to about 5 A, the electrode rod can perform the predetermined process in 15 to 20 seconds. It goes without saying that the corrosion treatment time can be shortened by increasing the applied current value, but if the current value becomes excessive, spark discharge begins to occur from the electrode rod (the corroded surface tends to become rough). When using AC power for printing,
Since spark discharge is more likely to occur than when using a DC power supply, it is desirable to suppress the load voltage (or current) of the power supply so that the power supply value to be energized does not exceed 10A at most.

FIG. 6 shows an embodiment in which the electrode rod is not removed from the TIG torch and is subjected to corrosion treatment in its trench state. In the figure, 1 is a tungsten rod attached to the TIG torch 17 (a tungsten rod containing a thermal lightning or particle-emitting substance such as TIG or zirconia), 14 is a corrosive solution to corrode the electrode 1, and 16 Z06 is a cover provided on the top of the welder 13 to prevent the evaporation of the corrosive solution 14 and the incorporation of dust.Z06 is a power source for electrolytic corrosion. For example, a dual-purpose AC/DC power supply is used as is. Also,
It may be built into the welding machine as a dedicated power source for corrosion treatment of the electrode rod.

This eliminates the need for attaching and detaching the electrode rod from the torch, and allows a predetermined corrosion treatment to be performed on the surface of the tip. In addition, the equipment is simpler and welding power source (welding machine)
Predetermined energization can be easily performed with a single switch.

Figures 7(a) and 7(b) show the conventional method of re-grinding shown in Figure 3 (Figure a) and the method of the present invention shown in Figure 6 (Figure b).
This is a comparison of the construction procedures. In the conventional method, when the ability to start the arc deteriorates due to repeated welding, the welding operation is stopped (the same applies when the specified usage time has elapsed or welding becomes impossible), and the electrode rod is removed. Remove it from the torch and re-grind its tip. Then, the electrode rod is attached to the torch again and welding work is restarted.

On the other hand, the method of the present invention performs corrosion treatment instead of re-grinding, and if it is done as shown in Figure 6, corrosion treatment is applied to the surface of the tip of the electrode rod without removing it from the torch. Since it can be processed, time can be shortened.

In addition, in the method of the present invention, tricium (or zirconia) is precipitated at the tip of the electrode rod, and the thermionic emission ability is high (10), so the arc starting characteristics are improved compared to the conventional method, and the arc is stable. Moreover, the usage time can be extended. This further improves the quality of the welded area and also makes it possible to improve the welding operation rate.

Although this embodiment has been described with reference to an electrode rod used in TIG welding, the present invention can also be applied to an electrode rod equipped in a plasma torch that generates a plasma arc (for welding fog cutting and thermal spraying). Needless to say, it is applicable.

〔Effect of the invention〕

As described above, according to the present invention, even if an electrode rod has fallen into a state in which it cannot start an arc, it can be made to have the ability to start an arc again without re-grinding the electrode rod. Therefore, the effort and time of grinding can be reduced. Furthermore, according to the present invention, it is possible to arbitrarily deposit a thermionic emissive substance such as thoria or zirconia on the tip of the electrode where the arc is to be generated, thereby stabilizing the arc starting characteristics and shortening the usage time of the electrode. It is possible to increase the welding reliability, weld quality and uptime (11). In particular, the present invention can fully exhibit its effects when applied to an automatic welding line that performs arc spot welding or intermittent welding where arc starting is frequent.

[Brief explanation of drawings]

Figure 1 shows the arc starting situation during TIG welding. Figure (a) shows a normal arc, Figure (b) shows an abnormal arc, and Figure 2 shows an arc that cannot be started. FIG. 3 is a diagram showing the conventional grinding method, FIG. 4 is a configuration diagram of a corrosion treatment apparatus explaining the present invention, and FIGS. 5(a) and (b) 6 is an electron micrograph and a Th0 X-ray diagram of the surface of the electrode tip subjected to corrosion treatment according to the present invention, and FIG. 6 is an example of the present invention.
Figure 7 ←) is a comparison diagram of the construction procedure between the conventional method (Figure a) and the method of the present invention (Figure B). 1... Tungsten electrode rod, 2... Holder, 3...
...Holder, 4.4'...Arc, 5...Base material,
6... Welding power source, 7... Grinder, 10... Power source,
DESCRIPTION OF SYMBOLS 11... Variable device, 12... Switch, 13... Container, 14... Corrosion solution, (12) 15... Current-carrying terminal, 16... Cover, 17... T
IG) (13) Fig. 1 ('') Decreased 5 0 Fig. 2 Fig. 3 Fig. 4 Fig. 5 (s(f) Fig. 6 s) Knee-=

Claims (1)

[Claims] 1. A thermionic emitting substance such as thorium oxide or zirconia? The tip of the tungsten electrode rod? This is a corrosion method for tungsten electrode rods, which is characterized by the fact that tungsten is electrolytically corroded in a corrosive solution that undergoes an electrochemical reaction, thereby increasing the arc starting ability of the electrode rods. 2. Should I use a welding power source or a power source installed in the welding machine as a power source for electrolytic corrosion of the tungsten electrode rod?
A method for corroding a tungsten electrode rod according to claim 1.