The art of tungsten electrode polishing: creating perfect welding!

Tungsten electrodes are used for TIG welding, which is a tungsten alloy strip made by adding about 0.3% -5% rare earth elements such as cerium, thorium, lanthanum, zirconium, yttrium, etc. into a tungsten matrix through powder metallurgy, and then pressure processing. The diameter ranges from 0.25 to 6.4mm, and the standard length ranges from 75 to 600.

The most commonly used specifications are diameters of 1.0, 1.6, 2.4, and 3.2. The shape of the electrode terminal is an important factor for TIG. When using DC positive connection, the tungsten electrode terminal needs to be ground into a pointed shape, and its tip angle varies with the application range, electrode diameter, and welding current. Narrow joints require a smaller tip angle. When welding very thin materials, a small current, needle like minimum electrode is required to stabilize the arc.

When using an AC power source for welding, there is no need to grind the tungsten electrode when welding aluminum magnesium, because when using an appropriate welding current, the tungsten electrode will form a half spherical shape. If the welding current is increased, the electrode will become a bulb shape and may melt, contaminating the melt pool.

In tungsten electrodes, more importantly, their final color and tungsten content vary. When welding, choosing the correct tungsten electrode makes welding easier, and it is important to obtain high-quality welding.

Type of Tungsten Electrode

The shape of the tungsten electrode tip has a significant impact on TIG welding. Reasonable types and shapes of tungsten electrodes contribute to arc stability and improved welding performance.

Pure tungsten electrode (green) has a high melting point and boiling point, making it difficult to melt, develop, or burn. It has less pollution at the tip, but poor electron emission, which is not conducive to stable combustion of the arc.

Thorium tungsten electrode (red) has strong electron emission ability, allows high current density, and has stable arc combustion. However, thorium has a certain level of radioactivity, which limits its use.

Cerium tungsten electrode (gray) has low electron work function, high chemical stability, large allowable current density, and is non radioactive, making it a commonly used electrode at present.

Zirconium tungsten electrode (white) can be used to prevent electrode contamination of the base metal and under specific conditions. The tip of this electrode is easy to maintain a hemispherical shape and is suitable for AC power welding.

The shape and application of tungsten electrode

1. The conical shape is suitable for small current welding of thin plates and curved butt welds.
2.  The arc shape is suitable for welding with AC power supply, but the arc is unstable when connected to DC positive.
3. Cylindrical shape is suitable for welding aluminum and magnesium alloys. But the direct current positive connection method is not available.
4. Flat bottom shape is suitable for DC positive connection, with concentrated arc, stable combustion, and good weld formation.

After grinding the tungsten electrode cone, the tip diameter should be appropriate. If it is too large, the arc will be unstable; Too small, easy to melt. It is generally determined based on the magnitude of the welding current. The length of grinding is generally 3-5 times that of the tungsten electrode, and the minimum diameter at the end should be 1/2 of the tungsten electrode diameter.

There are three main shapes of tungsten electrode tips in current production applications: spherical, conical, and conical with a platform. Spherical end

Spherical tips are generally used for pure tungsten and zirconium tungsten electrodes, for alternating current and traditional square wave TIG welding. Firstly, it should be noted that the spherical end is not ground out but produced after welding.

Just ignite the arc under the recommended current conditions, and for a given electrode diameter, a spherical end will be formed at the end of the electrode. The diameter of the ball should not exceed 1.5 times the diameter of the tungsten electrode. Excessive size of the end ball can reduce arc stability and may detach and contaminate the weld seam, forming tungsten inclusions.

Conical shape or conical shape with platform

Conical or plateau conical tungsten electrodes (for pure tungsten, cerium tungsten, lanthanum tungsten, and thorium tungsten) are suitable for AC and DC welding. Grinding the electrode into a conical shape can facilitate arc initiation, generate more concentrated arcs, and thus have better welding performance. Choosing the appropriate end shape and angle is crucial. The right choice depends on the goal you want to achieve.

When welding thin plates (from 0.1mm to 1.0mm) using low current welding, it is recommended to polish the tungsten end into a sharp conical shape. A conical end can concentrate welding current and help prevent thin plate distortion and deformation.

Under higher current conditions, it is recommended to polish the electrode end into a conical shape with a platform. This end shape can prevent high current from melting the tungsten electrode tip, thereby causing contamination of the welding pool. It is not recommended to use sharp conical tips under high current conditions.

Polishing of tungsten extreme head

In order to properly polish tungsten electrodes and prevent contamination, it is best to use a specially designed grinding wheel for polishing tungsten electrodes. The grinding wheel should have the hardness to polish tungsten, and the axis of the tungsten electrode should be consistent with the tangent of the grinding wheel rotation direction to ensure that the polishing marks are longitudinal