Gas for TIG welding
When pinpoint control, high quality and aesthetics are important, gas tungsten arc welding (GTAW), also known as TIG welding, can meet those requirements.
But did you know proper shielding gas coverage is critical to achieving the best results in this process?
Many factors impact shielding gas coverage, including the choice of consumables paired with the proper gas flow settings.
Choosing the right gas and consumables for the job depends upon the desired performance and in some cases operator preference, among other key factors.
Keep these considerations in mind to get optimal results with GTAW.
What is the best gas for TIG welding?
In GTAW an inert gas protects the molten weld pool and tungsten from surrounding atmospheric gases. These atmospheric gases can react with the weld pool, causing contamination.
Although the primary purpose of a shielding gas is to shield the weld pool and tungsten from atmospheric gasses, the shielding gas also influences heat inputs and arc starting characteristics. *Due to the influence the shielding gas has on an arc, it is critical to adhere to any welding procedure specification (WPS) that is issued.
The three most common shielding gas options for GTAW are 100 percent argon, 100 percent helium and an argon/helium mix. You can use these shielding gases for all materials.
- 100 percent argon: Welders use Argon for GTAW primarily due to its availability, cost and arc starting characteristics. Argon produces consistent high frequency arc starts due to its lower ionization potential and produces a more stable arc compared to that of helium.
- 100 percent helium: Because it has higher thermal conductivity than argon, helium can be used for GTAW to produce higher heat inputs. These higher heat inputs result in faster travel speeds and higher depth-to-width ratios and are good for welding thicker materials. Helium does have a higher ionization potential, resulting in inconsistent arc starts.
- Argon/helium: An argon/helium mix is typically used to achieve the higher heat inputs of helium while maintaining the superior arc starts offered by argon. These mixes commonly contain 25 to 75 percent helium. As helium content increases, the arc becomes hotter but high frequency arc starting performance and stability decrease.
To determine the best shielding gas for your application, consider the cost, required heat and high frequency arc starting consistency.
Gas flow rates
The optimal gas flow rate for TIG welding varies by the combination of consumables and atmospheric conditions. GTAW flow rates are typically between 10 and 35 cubic feet per hour (cfh).
When the shielding gas exits the nozzle, it has a different velocity than that of the atmospheric gases surrounding it. The different velocity and density between these two types of gases can cause currents to form, which can potentially turn the shielding gas column from a laminar flow (which is desirable) to a turbulent flow (less desirable). A turbulent flow can pull atmospheric gases into the shielding gas column, leading to contamination of the weld and/or tungsten.
As shielding gas flow rate is increased, the laminar flow column becomes more turbulent, increasing the chances for the weld and/or tungsten to become contaminated. Decreasing flow rate causes the shielding gas column to become more laminar and less turbulent. Although a higher flow rate produces a turbulent shielding gas column and isn’t necessarily better, a flow rate that is too low can be easily disturbed, breaking down the shielding gas column and potentially contaminating the weld and/or tungsten as well. To achieve the greatest laminar flow, use the lowest gas flow rate possible for the application and conditions.
Experts recommend a flow meter regulator for measuring cfh due to its accuracy. Place the regulator as close to the welding power source as possible for the best results and easy adjustments.
Gas lens or collet body?