When To Use TIG Electrodes

When using plasma welding or arc welding with tungsten inert gas (TIG), tungsten electrodes are utilized. An inert gas shields the electrode, arc, and weld pool from airborne contaminants in both procedures. Because tungsten can endure extremely high temperatures with little melting or erosion, it is utilized as an electrode. Powder metallurgy is used to create electrodes, which are then shaped to size following sintering.

Other metallic oxides, which are often present in trace amounts in TIG welding electrodes, have the following advantages:

• Aid in the arc's beginning.
• Enhance the stability of the arc.
• Increase the rod's capacity to carry current.
• Minimize the possibility of weld contamination.
• Lengthen the electrode's life.

The most commonly utilized oxides are those of cerium, lanthanum, thorium, zirconium, or yttrium. Typically, additions range from 1% to 4%. Each of these oxides significantly enhances arc initiation, particularly in direct current (DC) welding applications. Since thoria (thorium oxide) has been shown to be successful in terms of long life and thermal efficiency, it has been utilized for many years. When using alternating current (AC) TIG welding, zirconium oxide, or zirconia, is typically used to weld aluminum.

TIG Electrodes: Risks

With a lengthy half-life, thorium (Th) is mildly radioactive and mostly emits alpha (α) particles, though it can also occasionally produce some beta (β) and gamma (γ) radiation. Paper or skin cannot be penetrated by Alpha particles. But if they get into the lungs or digestive tract, where they act as carcinogens, they become dangerous. 

Thus, thorium oxide is a low-level radioactive substance that can provide an internal risk from ingestion or inhalation, as well as a little exterior radiation risk. The predicted external radiation risk for a welder holding an electrode for a whole year is minuscule compared to the maximum allowable radiation dosage, leading experts to conclude that the external radiation risk is most likely insignificant.

During arcing, very little radioactive material is released. However, the TIG electrodes tip must be honed to a conical point before use in order to obtain optimal arc stability. During use, its shape is preserved by frequent regrinding. Tungsten particles with thoria on the surface could be created during the grinding process. The primary risk is posed by these dust particles because they can be inhaled and because the thoria has the potential to discharge alpha particles from their surface.

After reviewing air sampling measurements taken during grinding, it was determined that air concentrations could get close to or even above those at which it would be appropriate to designate the area as a controlled area in accordance with the Ionising Radiation Regulations of 1999.

However, because individual exposure durations to thoria are always brief, the risk of cancer among TIG welders as a result of thoria exposure is quite low. According to estimations from the Danish Welding Institute, among 1200 full-time TIG welders, 0–3% of them will develop cancer during the course of a thirty-year career. Although this amount is deemed acceptable, the Danish Welding Institute has suggested that, given the availability of non-radioactive alternatives, tungsten be phased out in Denmark.

SAFE AND SECURE WORKING ENVIRONMENT

STORAGE

Thoriated electrodes should ideally be kept in steel cases that are prominently marked with the radiation trefoil. Handling and storage pose no substantial risks when enclosed in closed boxes.

Welders can safely handle small quantities of electrodes—one day's worth—without taking any extra safety measures.

PREPARATION AND GRINDING

The biggest risk is from grinding since it increases the exposed tungsten/thoria area and releases fine, possibly radioactive dust particles into the sky.

In the event that less than 20 electrodes are used annually, it is advised to use a specialized grindstone with local dust extraction and to use a basic filter mask. Eye protection should be worn if the grinding wheel is not equipped with a protected viewing screen. Particles should be placed into a large, disposable bag by the way the grindstone's air extractor is set up.

To minimize release into the atmosphere, a safe way of handling and collecting the dust from the collection unit must be utilized (for example, it could be placed in a sealed paper/plastic bag).

To get rid of dust, the area surrounding the grinding wheels needs to be vacuumed every day. If one does not have access to a high-efficiency Hoover cleaner, the material should be compressed to reduce dust.

Hand washing stations should be placed close to the work areas because it is important to urge employees to wash their hands before using the lavatory and before taking breaks.

WELDING

Welding does cause some tungsten to evaporate, but only very little, and the radioactivity that results is also very low. No extra safety measures are required. Wearing protective gear for the mouth, nose, and eyes while welding would, however, further minimize any chance of contamination—just like when grinding thoriated tungsten electrodes.

SUBSTITUTES FOR THORIATED TUNGSTEN

Tungsten can be utilized in conjunction with oxides of lanthanum, cerium, yttrium, and zirconium. Although they are all slightly radioactive, there is no need for special measures because the risk is far lower than with thoria. Users generally agree that zirconiated tungsten is the best option for AC current welding, but ceriated or lanthanated tungsten are suitable substitutes for thoriated tungsten, especially when welding with a DC current. The arc voltages needed for equal currents across the different options differ just slightly. Justifying the usage of thoriated tungsten electrodes over more appropriate substitutes should be taken into account.

OFFICIAL PROTOCOLS

According to the International Institute of Welding Health and Safety Commission VIII, there are no particular risks associated with handling, storing, or welding; nonetheless, the grindstone should be equipped with dust extraction equipment, and the operator should wear respiratory protection when grinding. Health and Safety Executive Guidance note HS(6) 53 addresses this. The choice, use, and upkeep of respiratory protection gear.

Adequate supervision and local regulations are necessary. A Radiation Protection Supervisor (RPS), appointed by the company, is in charge of

• The application and oversight of all health and safety protocols concerning the usage, storage, grinding, and disposal of tungsten electrodes that have been thoriated, as well as any byproducts.
• Maintaining track of the quantity of thoriated tungsten that is on hand as well as the quantity of electrodes that are given to each welder.
• Giving the welders instructions on proper use and grinding techniques. Together with vocal presentations, these procedures ought to be documented in the form of written instructions. The RPS name must be known by welders.
• Monitoring to ensure that the dust extraction system is operating efficiently and that the welders are performing the grinding procedures correctly.