Helium arc welding:
Helium arc welding is a type of gas tungsten arc welding (GTAW) process that uses helium as the shielding gas. It is commonly used for welding non-ferrous metals like aluminum, magnesium, and copper alloys. The process involves melting the workpiece and the filler metal using an electric arc generated between a tungsten electrode and the workpiece.

The electrode in helium arc welding:
In helium arc welding, the electrode used is made of tungsten. Tungsten has a very high melting point and excellent heat resistance, making it suitable for this welding process. Tungsten electrodes are commonly used in GTAW processes due to their durability and ability to withstand high temperatures.

Reasons for using tungsten electrode:
- High melting point: Tungsten has the highest melting point of all metals, which allows the electrode to withstand the high temperatures generated during the welding process without melting or deforming.
- Heat resistance: Tungsten has excellent heat resistance, which helps in maintaining the stability and shape of the electrode even at high temperatures.
- Non-consumable: Tungsten electrodes are non-consumable, meaning they do not melt or contribute to the filler metal during the welding process. This allows for precise control over the welding process and prevents contamination of the weld.
- Good electrical conductivity: Tungsten has good electrical conductivity, which is necessary for generating and maintaining the electric arc during the welding process.
- Suitable for non-ferrous metals: Tungsten electrodes are particularly suitable for welding non-ferrous metals like aluminum and copper alloys because they do not react with these metals, ensuring a clean and high-quality weld.

Conclusion:
In helium arc welding, the electrode is made of tungsten. Tungsten electrodes are preferred in GTAW processes due to their high melting point, heat resistance, non-consumable nature, good electrical conductivity, and compatibility with non-ferrous metals.