Tungsten electrodes <-> welding result


Grinding of tungsten electrodes

The shape of electrode tip determines considerably the welding process and the quality of weld seam. Prior to grinding it has to be regarded that the end of electrode is not broken nor pinched. The grain boundery consistancy is lower than the consistancy of the individual cristals. Therefore, electrodes tend to weaken along the grain bounderies under mechanical load. The heavy heat during welding will lead then to fissuring at the tip.

Grinding the tungsten electrode must be effected very carefully, in order to avoid any grain boundary damage due to mechanical forces. The grinding only may be done under slight pressure, since too great heat accumulation may result in grain tension and grain boundary damage. A free-hand grinding should be avoided completely!

The grinding picture

A grinding disc with most fine grain should be used. Best are diamond grianding discs (depending on load either with a plastic or metal binding).

Korundium grinding discs will show unsatisfactory grinding results due to the hardness of tungsten. The life time of electrode will increase the finer the grinding is.

Direction of grinding

It is absolutely necessary to grind in longitudinal direction!

Therefore the electrode only shall be ground in longitudinal direction being turned very slowly! With a cross grinding the grooves will result in an unstable arc and in break-off of tungsten particles which may drop into the molten pool.

The centric

Anschliff in Längsrichtung

It is very important that the tip is positioned as centrically as possible in the electrode longitudinal axis. 

With a variance it may happen that  the arc becomes instable.

Especially during automatic welding it may happen that an adjustment of electrode towards the workpiece and to the electrode longitudinal axis is done, but, due to missing centric the welding energy will not be brought to the area desired.

The grinding angle

wrong grinding angle

In coaction with diameter of tungsten electrode the grinding angle has the decisive influence in the quality of weld seam.

At the adjoining picture it is shown, how a molten pool takes shape with identical current force but different grinding angle.

The arc illustrates the mirror image of the grinding angle.

angle of tip

With a pointed electrode energy is brought to a small surface with deep penetration. With dull electrodes the energy with identical weld current is brought to a large surface with a considerably shallow molten pool.   

Grinding length of electrode

as function of electrode diameter and grinding angle.

grinding angle at tungsten electrodes
Possible scan setting at electrode grinding appliance EAG-3
scan setting at electrode grinding appliance EAG-3

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