Electrode materials commonly used in tungsten argon arc welding

Currently used electrode materials are pure tungsten, needle tungsten, cerium tungsten, zirconium tungsten and strontium tungsten, etc., of which the most commonly used are thorium tungsten and cerium tungsten.

(1) Pure tungsten: tungsten has a high contact point of about 3380°C and a boiling point of about 900°C, so it is not easy to melt and evaporate. With pure tungsten can be made of various diameters of electrodes, and has a good grinding performance. The escape work of pure tungsten is high, 4.31~5.16eV, so it is more difficult to induce arc in cold state. However, tungsten's melting point is high, at high temperatures, tungsten's hot electron emission ability is still very strong, once the arc is ignited, the arc is still very stable. In DC positive polarity welding (tungsten pole negative), because of the strong hot electron emission ability, the permissible welding current is larger. In DC negative polarity welding (tungsten pole positive), the tungsten pole can not play the advantage of hot electron emission, the permissible current is very small. AC welding, between the two, the permissible current value is also in the middle.

(2) thoriated tungsten: in the pure tungsten by adding a mass fraction of 1% to 2% of thorium oxide (ThO), so that the electrode's escape work is greatly reduced, the electron emission ability to significantly enhance and improve the electrode's arc attraction and stabilization of the arc, but also to improve the electrode's current-carrying capacity, to extend the service life of the electrode. But thorium tungsten electrode contains a small amount of ThO2 has strong radioactivity, so it is not used much.

(3) Cerium tungsten: In order to reduce the radioactivity of the electrode, cerium (Ce) with lower radioactivity is used instead of thorium. Practice has shown that the addition of cerium oxide (CeO) in pure tungsten with a mass fraction of 2% or so, can also significantly reduce the electrode's fugitive power, improve the electrode's arc and arc stabilization. Especially in the small current welding, cerium tungsten electrode arc beam than thorium tungsten electrode is also thin, the heat of the arc is also more concentrated. At the same time, the burn rate of the electrode decreases, and the number of repairs can be reduced. But in high current welding, cerium tungsten electrode's overheating resistance is not as good as needle tungsten electrode. Cerium tungsten electrode is a promising electrode material due to weak radioactivity.

In order to facilitate the use of tungsten electrode one end is often coated with color, in order to identify, thorium tungsten electrode red, cerium tungsten electrode gray, pure tungsten electrode green. Commonly used tungsten electrode diameter of 0.5mm, 1.0mm, 1.6mm, 2.0mm, 2.4mm, 3.2mm, 4.0mm, and other specifications.