What Is a Tungsten Electrode?
A tungsten electrode is an electrode used for welding.
It is made of tungsten and processed into a cylindrical shape. They are sold in diameters ranging from 1.0 to 4.0 mm and lengths of about 150 mm.
Uses of Tungsten Electrodes
Tungsten electrodes are used for welding. Therefore, construction sites and processing plants are the main places where they are used.
Specific applications are as follows:
- For repairing boilers
- Maintenance and modification of motorcycles and automobiles
- Shipbuilding in shipyards
- For piping repair in chemical plants
Basically, it is used for welding of metal base materials. Among manufacturing industries, this component is often used in heavy industries.
Principle of Tungsten Electrodes
Tungsten electrodes are rods made of tungsten. Tungsten is a metal with an atomic number of 74 and is represented by the element symbol W. It is characterized by relatively high resistance and a high melting point among metals.
Tungsten electrodes are used as electrodes for TIG welding, taking advantage of their high melting point. TIG welding stands for “tungsten inert gas” welding and is a welding process using a tungsten electrode and inert gas. A high voltage is applied between the base metal to be welded and the tungsten electrode to generate an arc discharge.
The heat generated by the arc discharge melts the base metal for welding. During this process, inert gases such as argon and helium are sprayed to prevent oxidation and deterioration of the metal. The high melting point of the tungsten electrode allows welding without mixing with the base metal. The tip of the tungsten electrode is machined into a conical shape at the time of use. The shape of the arc discharge can be changed by this cutting angle.
When the tip of the tungsten electrode is sharply angled, the arc spreads over the entire area. A large area of the base material can be melted shallowly. When the angle is obtuse, the arc concentrates on a single point at the tip. This enables deep melting of a single point of the base material.
Types of Tungsten Electrodes
There are four types of tungsten electrodes. The four types are thorium oxide, cerium oxide, lanthanaum oxide, and pure tungsten electrode. Each has different characteristics, so it is important to use the appropriate one depending on the application.
1. Tungsten Electrode With Thorium Oxide
This is a tungsten electrode containing 1~2% thorium oxide. It is characterized by its strength against abrasion and startability, which are superior to those of pure tungsten electrodes. However, the tip of the electrode is easily deformed when used with AC current, and it may melt and scatter during welding. Therefore, it is suitable for applications welding with DC current.
2. Tungsten Electrode With Cerium Oxide
This is a tungsten electrode containing 1~2% cerium oxide. The tip of the electrode does not melt and scatter even with AC current, and it has higher resistance to abrasion and startability than the electrode containing thorium oxide. It is suitable for AC welding of aluminum and aluminum alloys.
3. Tungsten Electrode With Lanthanum Oxide
Tungsten electrodes containing 1~2% lanthanum oxide have the highest resistance to abrasion and startability among the four types of electrodes, and can be used continuously for a long time while maintaining arc stability. It is suitable for automatic welding and is used in applications such as robot welding.
4. Pure Tungsten Electrode
This is a tungsten electrode composed only of pure tungsten and has the weakest resistance to abrasion and startability among the four types of electrodes. While the tip wears out quickly, once it becomes round, it does not deform any further, so it is characterized by its resistance to splattering during welding. Therefore, it is used for AC welding applications where electrode wear is high.
Other Information on Tungsten Electrodes
Distinguishing Colors of Tungsten Electrodes
Identification colors of tungsten electrodes are specified for each of the aforementioned types. The identification color is a color to be painted on the rod end for easy recognition at the time of sale, and is specified according to the standards.
The following are the identification colors of each electrode:
- Yellow: 1% thoriated tungsten electrode
- Red: 2% tungsten electrode with thorium
- Peach: 1% cerium-in-tungsten electrode
- Gray: 2% cerium-in-tungsten electrode
- Black: 1% tungsten electrode with lanthanum
- Yellow Green: 2% tungsten electrode with lanthanum
- Green: Pure tungsten electrode