Practical tips for welding: sharpening tungsten electrodes

Posted by Richard Baumann on Dec 3, 2020 7:44:33 AM
Find me on:

5 essential tips how to sharpen TIG welding electrodes correctly

Excellent-looking weld seams can be conjured up with TIG welding. It is not only the choice of the right tungsten electrode that has an influence on the appearance and quality of the welding result. HOW the TIG welding electrode is sharpened also has an enormous influence on the weld seam. In this blog we would like to show you how to properly sharpen tungsten electrodes so that this essential welding accessory for the TIG torch can unfold its full effect.

Wolframelektroden_Anschleifen_am_Stein_bannerMostly practised but wrong – This is not the correct way to sharpen tungsten electrodes!

Instable arc, bad ignition … does that sound familiar?

You have set up everything, checked the connections and settings on the welding machine one last time and start your welding process. It seems that all the requirements for a well-running weld have been met, but the arc ignites poorly or is restless. What could that be? Is the gas supply possibly not optimal? If you can rule that out, it is best to take a closer look at your TIG welding electrode. If it is blunt and therefore worn or if it even looks porous, it must be sharpened. Perhaps you have just sharpened the TIG welding electrode and the problem with the poorly igniting or unstable arc is due to incorrectly sharpening your welding electrode.

 

Why do you need to sharpen tungsten electrodes?

A tungsten electrode is a so-called non-consumable electrode, but in the course of its use it also changes its properties, which come from the doping elements added – and the shape. To be precise: at the top, where things get hot.

 

Doping elements and their task – a little excursion

Common doping elements are oxides of thorium, lanthanum, cerium and zirconium. One of their tasks is to facilitate the emission of electrodes from the tungsten electrode, because that means more energy in the arc, more efficient welding and often even a higher welding speed. Because a TIG welding electrode can reach temperatures of up to 3,000 ° C in the process and even more at the tip, the melting point of tungsten is exceeded. As already mentioned, high temperatures mean good emission from electrodes, but this also means that more material is removed. The added doping elements or oxides also lead to a lowering of the temperature required for emission and in this way reduce the wear and tear on the tungsten electrode. You can read more about the properties of the various doping elements in our blog »Practical tips for welding: tungsten electrodes«.

 

The more a TIG welding electrode is used, the more the doping elements emit, which means that the tungsten electrode, for example, no longer ignites well or the arc becomes unstable. This can also be recognized by the fact that the electrode tip becomes porous and open-pored, which the following figure clearly illustrates.

Wolframelektroden_Lanthanoxid

This figure shows the severe so-called depletion of lanthanum oxide at the tip of a used tungsten electrode (WL 20). Source: Andreas Endemann, Weldstone Components GmbH

 

So, if you want your tungsten electrode to last for a long time, you have to know that the doping element slowly evaporates from the tip of the TIG welding electrode. With the washing out or evaporation of the doping element, the doping from the core of the electrode also diffuses more slowly to the tip. So, it is ideal to have a tungsten electrode, whose added oxides are retained for as long as possible. For example, the E3® tungsten electrode from ABICOR BINZEL with the addition of rare earths is significantly more stable than the electrode with cerium oxide, which evaporates comparatively quickly. With an E3® welding electrode you are happy for longer and you only have to grind the tungsten electrode at significantly longer intervals.

 

A phenomenon that can also be observed on tungsten electrodes is the so-called crown formation. Perhaps you have also seen how many small peaks have formed around the sharpened electrode tip. One could assume that this has something to do with the properties of tungsten, but it has nothing to do with it. Rather, these are the consequences of oxidation with oxygen, sublimation – i. e. the phase transition from the solid to the gaseous state – and the subsequent dissociation (division of the chemical compound into two or more molecules) of the resulting oxides. By sharpening the tungsten electrodes, these material rings can be removed again without any problems.

 

Sharpening tungsten electrodes is therefore essential for the best welding results!

 

When sharpening a tungsten electrode, however, a few essential things must be observed. We have put them together for you here.


5 tips how to properly sharpen tungsten electrodes

1. Be careful with broken or pinched electrode tip

If you look at a tungsten electrode tip, greatly enlarged, you can clearly see the so-called grain size in the material, which is characterized by light and dark areas. Every boundary from one area to the other represents the grain boundary. Tungsten electrodes have their weak point when subjected to mechanical stress along the grain boundary. This means: A pinched or worn TIG welding electrode is weakened at the grain boundaries. If this is now sharpened, something similar happens that, figuratively, is known from pencil sharpening with a blunt sharpener: The material does not tear open nicely.

 

The heat during welding can cause cracks to form at the tip if the grain boundary is damaged. When grinding the tungsten electrode, you have to proceed very carefully so that the grain boundary is not damaged. The pressure for sharpening should also only be light. If the pressure is too great, heat builds up, which in turn can damage the grain boundary.

 

2. Never sharpen the TIG welding electrode freehand

Angle grinder, whetstone or abrasive mop – there are the most adventurous approaches to sharpen tungsten electrodes manually. In any case, do not try to grind the tungsten electrode freehand! For a good welding result, the tip must be concentric and the sharpening surface smooth. Even with very steady hand control, you would never get a perfect tungsten electrode cut. And this is especially important when the weld seam is more demanding. In addition, grinding by hand is never exactly the same a second time. However, repeatable parameters are the be-all and end-all for consistently good resp. high quality.

 

3. The right sharpening direction for tungsten electrodes: axial instead of radial

When sharpening the TIG welding electrode, the grinding direction is decisive: If the grinding is transverse, i. e. radial to the welding electrode, a wide arc cone is generated. The penetration depth is then smaller, which as a result leads to root binding errors, for example in the case of an i-joint. If, on the other hand, the cut is longitudinal to the electrode, i. e. axially, the arc is more focused, enables deeper penetration and thus makes it easier for the welder to apply the energy with pinpoint accuracy.

Wolframelektroden_Axial_Radial

There is a rule of thumb: the tip of the tungsten electrode should be twice as long as its diameter.

 

4. Sharpening at the correct angle

You get the best welding result with the correct grinding angle. The sharper the TIG welding electrode is ground, the more targeted and narrow the penetration. At the same time, however, the load on the electrode tip is extremely high, which in turn limits its service life. With an extreme peak of, for example, 30 °, tungsten can get into the weld pool and then contaminate it. If, on the other hand, the tungsten electrode is blunt-pointed and you weld with it at the same welding current as with the sharpened electrode, the penetration is wider and less focused. We recommend a grinding angle of 60 ° for TIG welding electrodes in order to achieve the best welding results.

Wolframelektroden_Axial_Radial_Winkel

5. Flatten the electrode tip after sharpening

We recommend you flatten or blunt the tip of the tungsten electrode after sharpening. The guideline for this is approx. ten percent of the electrode diameter – an electrode with a diameter of 1.6 mm then has a blunt tip of approx. 0.15 mm. The flattened tip has a positive effect on the electrode exit because it prevents particles from breaking out of the tungsten electrode tip. In addition, the flat surface grinding of the tip puts less stress on the electrode and thus extends the service life of this wear part.

 

Sharpening the electrode when welding with AC

When welding with alternating current, grinding a tungsten electrode behaves differently: Instead of being pointed, the welding electrode is ground flat so that a spherical cap can be formed. This spherical shape can be created more easily if the electrode has been chamfered or grinded at 45°. If you notice with a doped tungsten electrode such as the E3® that it ignites poorly – which is due to the depletion of the doping elements – you shorten the welding electrode by at least the length of the cap and chamfer it, as mentioned at the beginning. A little tip to get a nice calotte: Hold the torch with one hand and ignite the arc, while using the other hand briefly increase the current on the power source ... and there is a 1A calotte.

 

If you notice that the calotte is significantly larger than the electrode diameter, then the welding current is too high for this electrode and you should use the next larger diameter.

 

Formation of the calotte with different amperage (AC welding)

Wolframelektroden_Kalotte

    Too low                         Correct                           Too high

 

Let’s get down to it: Which device is best suited for sharpening tungsten electrodes?

Whetstone, angle grinder, abrasive mop ... it is best not to use these devices for grinding tungsten electrodes. Although manual grinding with such helpers is very widespread and may be sufficient for small workshops, we recommend grinding the electrode with a tungsten electrode grinder. There are good devices on the market for this, which are definitely worth investing in if you want to achieve top welding results.

 

The automated sharpening devices for TIG electrodes are available as dry grinding devices and as wet grinding devices. If you have to sharpen your tungsten electrodes very often, the wet grinder is recommended because it also cools. Because of the friction on the grinding wheel, you can see small sparks spraying on dry grinders during the grinding process, which is not a problem if grinding is not so frequent. The tungsten electrode sharpening itself can be done in a few simple steps and is a safe thing – also from a health point of view, because the grinding dust is absorbed in the device and does not get into the welder's respiratory system.

 

We show you electrode sharpening with a dry grinder in 5 simple steps.

 

How to sharpen tungsten electrodes in 5 steps

1.

Wolframelektroden_Anschleifen_ULTIMA_TIG_A

Wolframelektroden_Anschleifen_ULTIMA_TIG_B

Clamp the TIG welding electrode in the clamping device integrated in the grinder and prepare it for grinding.

2. Set up the grinding angle.

3.

Wolframelektroden_Anschleifen_ULTIMA_TIG_C

Switch on the device, insert the tungsten electrode into the grinder and hold it.

4.
During the grinding process, turn the TIG welding electrode regularly until resistance can no longer be felt or heard.

5.

Wolframelektroden_Anschleifen_ULTIMA_TIG_D

Remove the welding electrode and check the result. The more pointed the tungsten electrode, the more focused and deeper the penetration.

As you can see, grinding tungsten electrodes has a significant influence on the welding process and the welding result. What have you already experienced or what are your experiences with grinding TIG electrodes? Please let us know here.

If you want to know more about TIG welding electrodes, get more information about this important welding accessory here.

Happy welding!

For regular updates on other interesting topics from the welding industry, please subscribe to our News:

Subscribe to our news!

Topics: TIG Torches