What Shielding Gas Should I use when TIG Welding?

When TIG Welding the most common gas option are 100% Argon, and an Argon/Helium mix. Both of these shielding gasses are used for all materials. 

• TIG Welding: Pure Argon is the most commonly used shielding gas for TIG Welding. 
  • 100% Argon
    • Is primarily used due to its availabilty, cost and arc starting characteristics. Argon produces consistent high frequency arc starts due to its lower ionization potential and produces a stable arc compared to that of helium.
  • Argon/Helium Mix
    • Is typically used to achieve higher heat inputs while maintaing the superior arc starts offered by argon. These mixes generally contain 25-75% helium. The more helium present the hotter the arc becomes but the high frequency arc starting performance and stability decrease. Due to the high price of helium and performance this is not commonly used.
• Gas Flow Rates
  • The opitmal gas flow rate varies by the comination of consumables and atmospheric conditonis. GTAW flow arates are generally between 10-35 Cubic Feet Per Hour (CFH). 20-25 CFM is generally a good starting point
    • A shielding gas flow that is to low can be easily disturbed, breaking down the shielding gas column and contamination the weld and/or tungsten as well.
    • A shielding gas flow that is to high the shielding gas can become more turbulent increasing the chances for the weld and/or tungsten to become contaminated. 
      • Shop Flowmeters Here
• Gas Lens or Collet Body
  • Consumables used in GTAW include a nozzle and a collet paired with either a gas lens or a collet body. Consider the requirements of the finished weld when choosing between the two. If the weld is critical or requires high quality, a gas lens is the best option. 
  • For non-critical or practice welds, a collet body is sufficient. Complete proper testing to verify that consumable combinations work for your application, and always follow the WPS.
  • A collet body has several holes that introduce the shielding gas to the inside of the nozzle. The holes tend to be perpendicular to the nozzle, causing the gas to spiral or be more turbulent exiting the nozzle. 
  • When using a collet body, the tungsten should not extend outside the nozzle more than the distance of the inside diameter of the nozzle.
  • A gas lens improves the consistency of the shielding gas coverage and reduces turbulence compared to that of a collet body because it has several screens inside that produce a more uniform laminar flow. The gas lens allows the tungsten to extend farther than the inside diameter of the standard collet body. 
    • Shop Collet Bodies Here
    • Shop Gas Lenses Here
    • Understanding Gas Coverage

• Best Practices for Success
  • When assembling the torch, tighten the collet body or gas lens before the back cap. If the order is reversed, the torch can take on atmospheric gases that result in contamination.
  • Missing or improper insulators can cause shielding gas contamination, so inspect insulators frequently.
  • A pre-flow of shielding gas helps shield the tungsten and weld area and initiate the arc start. A minimum pre-flow of 0.2 seconds is recommended.
  • Gas post-flow is also beneficial, assuring the weld is protected from atmospheric gases as the weld pool solidifies.  Hold the torch over the end of the weld until post-flow stops, to ensure coverage of the area.  Many people often overlook the fact that this gas is also shielding the tungsten from contamination as it cools – preventing poor arc starts on subsequent welds. Proper post-flow time in seconds is determined by dividing welding amps by 10. A minimum of eight seconds is recommended.
  • When running longer gas lines, the initial shielding gas released upon starting the arc will be a much higher flow rate. Decrease this by using shorter gas lines, or by increasing pre-flow time to purge the lines before arc start.