The selection of TIG shielding gases is crucial for the quality, appearance, and durability of the weld. In TIG (Tungsten Inert Gas) welding, the electric arc melts metal using a non-consumable tungsten electrode, and its stability and purity depend largely on the type of shielding gas. This creates a protective barrier between the weld zone and the air, preventing the ingress of oxygen, nitrogen, and water vapor. This prevents the metal from oxidizing, prevents the formation of gas inclusions, and ensures the weld retains its high gloss and corrosion resistance.
The TIG process uses inert gases, meaning those that do not chemically react with the metal – primarily pure argon, helium, or their shielding gas blends. Argon (Ar) is the most commonly used gas because it enables easy arc ignition and ensures a stable weld pool even at low flow rates. Helium (He), in turn, increases the thermal energy of the arc, allowing for deeper penetration and higher welding speeds, especially with thick aluminum or copper components.
The role of gas, however, is not limited to protecting the welding arc. A properly selected shielding gas influences the weld shape, its mechanical properties, and even the process’s economics. Too little gas flow causes porosity and discoloration, while too much causes turbulence and air suction into the welding zone.
This is why the PN-EN ISO 14175 standard classifies TIG shielding gases according to their composition and application (e.g., I1 – pure argon, I3 – a mixture of argon and helium, R1 – argon and hydrogen). When selecting the appropriate shielding gas, consider the material type (e.g., stainless steel, aluminum, copper), its thickness, the welding position, and the quality requirements.
In summary, the quality of the welding gas and its proper selection are fundamental to achieving a defect-free, corrosion-resistant weld that meets technological requirements. In TIG welding, every detail matters – from argon purity to gas flow adjustment – so professionally selecting a shielding gas is the first step to achieving a high-quality weld.
Pure Argon (Ar) – the “universal shielding gas”
Argon is the most commonly used and versatile gas in TIG welding. Chemically inert, it does not react with metal or the tungsten electrode, creating a stable arc shield and protecting the weld pool from air. This allows for clean, shiny welds without discoloration or porosity.
Pure argon (class 4.6–5.0, meaning 99.996–99.999% purity) ensures easy arc ignition, uniform metal melting, and good weld pool control. This makes it the recommended shielding gas for most TIG-weldable materials – from stainless steel and carbon steel to aluminum and copper. For thin sheets and precise welds, such as in industrial structures or process installations, pure argon guarantees the highest process stability and predictability.
According to equipment manufacturers’ recommendations (e.g., Kemppi, Fronius), the optimal shielding gas flow is typically 8–12 l/min, depending on the nozzle diameter and ambient conditions. It’s also important to ensure the tightness of the gas system and the cleanliness of the pipes, as even trace amounts of oxygen or moisture can impair weld quality and the metal’s corrosion resistance.
Thanks to its versatility and high arc protection effectiveness, pure argon remains the primary choice for most TIG processes – both for TIG welding of stainless steel and for working with aluminum, where maximum atmosphere purity and precise arc control are required.
Argon-Helium Mixture (Ar + He) – When “More Heat” Is Needed
Adding helium to argon is a proven way to increase the arc’s thermal energy and improve the efficiency of the TIG welding process. Helium has significantly higher thermal conductivity than argon, thus raising the arc temperature, resulting in deeper penetration, a wider weld pool, and faster welding speeds.
These types of shielding gas mixtures are particularly recommended for working with metals with high thermal conductivity, such as aluminum or copper, and for thicker components. In practice, mixtures containing 25 to 75% helium are used, depending on the requirements for penetration depth and arc stability. The higher the helium content, the higher the thermal energy, but also the higher the gas flow requirement and the slightly more difficult arc ignition.
According to manufacturers’ technical specifications (e.g., MillerWelds, Fronius), Ar+He mixtures can reduce welding time by up to 20–30% compared to pure argon, while also improving weld appearance and uniformity. For this reason, they are often chosen in the energy, aerospace, and petrochemical industries, where efficiency and high weld quality are paramount.
According to the PN-EN ISO 14175 standard, argon-helium mixtures are classified as I3-ArHe-30, I3-ArHe-50, or other variants, depending on the percentage of helium. The choice of a specific composition should always be based on the material type, its thickness, and the welding position – to achieve high weld quality at optimal process costs.
Argon and Hydrogen Mixtures (Ar + H₂) – Austenitic Stainless Steel
Argon and hydrogen mixtures are among the most effective shielding gases used in TIG welding of stainless steel, especially the austenitic version. Adding 1–5% H₂ to argon improves arc characteristics, increasing its thermal energy and stability. This results in a smoother weld pool, faster welding speeds, and a smooth, shiny weld bead with high corrosion resistance.
Hydrogen has a reducing effect, eliminating oxygen from the weld surface and limiting the formation of oxides. This is particularly important in industries requiring perfectly clean joints, such as the food, pharmaceutical, and chemical industries. These mixtures are effective for welding pipes, tanks, and system components made of austenitic stainless steel, where weld aesthetics and durability are essential.
However, it’s worth remembering that Ar + H₂ is not suitable for welding aluminum, copper, and ferritic and martensitic steels, as hydrogen can cause gas bubbles or hydrogen cracking in these cases.
According to the PN-EN ISO 14175 standard, these mixtures are classified in the R1 group – for example, R1-ArH-2.4 / 5, where the number indicates the percentage of hydrogen in argon. Proper selection of gas parameters and purity allows for exceptional weld quality, characterized by high corrosion resistance and aesthetic appearance.
Practical Parameters: Shielding Gas Flow and Settings
Proper shielding gas flow is crucial for effective protection of the arc and weld pool. Too little flow causes air to be drawn into the weld zone, resulting in oxidation and weld porosity, while too much flow creates gas turbulence, which also impairs arc stability. Therefore, it is crucial to precisely match the flow parameters to the gas type, nozzle diameter, and ambient conditions.
For pure argon (Ar), the recommended range is typically 8–12 l/min. However, when using argon-helium mixtures (Ar + He), it is worth increasing the flow to as much as 15–18 l/min, as helium has a lower density and is more difficult to maintain a stable shield. When working outdoors or in heavy drafts, it may be necessary to further increase the operating pressure to maintain the shielding integrity of the welding arc.
In addition to proper flow, it is also important to monitor the pre-flow (time of gas pre-flow before arc ignition) and post-flow (time of gas flow after the arc is extinguished). Too short a post-flow time causes the hot tungsten electrode to oxidize upon contact with air, shortening its lifespan and compromising the quality of subsequent welds. In practice, it is recommended to set the pre-flow to 0.5–1 s and the post-flow to 5–10 s, depending on the current intensity and material type.
The purity of the welding gas and the condition of the installation are equally important – any leaky hose, moisture, or contamination can lead to discoloration and porosity in the welds. Therefore, it is recommended to use gases with a purity of at least 99.996% (class 4.6) and regularly check the condition of the regulator, hoses, and torch.
Correctly setting the gas flow and purity is a simple yet crucial step in achieving high-quality welds and consistent results in TIG welding.
Selection Checklist: Material × Thickness × Geometry × Requirements
Choosing the appropriate shielding gas for TIG welding should always be based on an analysis of four key factors: material type, material thickness, weld geometry, and quality requirements. Each of these factors influences the choice of gas mixture composition, gas flow, and welding arc control.
1. Welding Material
Stainless Steel (Austenitic) – Pure argon (Ar) is best, providing a stable arc and clean welds. For higher efficiency and a smooth weld bead, argon-hydrogen mixtures (Ar + 2–5% H₂) can be used – they improve wettability and increase welding speed.
Carbon and Low-Alloy Steel – Pure argon (Ar) or Ar + 30% He are used, improving arc penetration and stability for thicker components.
Aluminum and its Alloys – Pure argon is sufficient for thinner components, while for thicker components or high thermal conductivity, an argon-helium mixture (Ar + 25–75% He) is recommended, ensuring deeper penetration.
Copper and its Alloys – Requires high thermal energy, so Ar + 50–75% He is the best choice, facilitating arc ignition and melting.
Nickel alloys and high-alloy metals – require the cleanest possible welding atmosphere, therefore Ar 5.0 or Ar + He is used (for better arc stability and oxidation resistance).
2. Material Thickness
Thin sheets (up to 3 mm) – pure argon ensures a smooth arc and precise weld pool control.
Medium thicknesses (3–6 mm) – a small addition of helium is permitted to increase welding speed.
Thick components (>6 mm) – Ar + 25–75% He mixtures are recommended, which allow for deeper penetration and reduce the risk of scale.
3. Welding Geometry and Position
Forced positions (vertical, overhead) – use pure argon, which produces a stable, focused arc and facilitates weld pool control.
Flat or horizontal positions – Ar + He or Ar + H₂ mixtures can be used, increasing metal fluidity and welding speed.
Pipes and Tanks – When circumferentially welding stainless steel, use pure argon back purging to avoid oxides and “welding sugar.”
4. Welding Geometry and Position
Forced positions (vertical, overhead) – use pure argon, which produces a stable, focused arc and facilitates weld pool control.
Flat or horizontal positions – Ar + He or Ar + H₂ mixtures can be used, increasing metal fluidity and welding speed.
Pipes and Tanks – When circumferentially welding stainless steel, use pure argon back purging to avoid oxides and “welding sugar.”
Common Mistakes and How to Avoid Them
Even the best-selected TIG shielding gas cannot guarantee a high-quality weld if the process is not properly controlled. In practice, most TIG welding problems stem not from the gas selection itself, but from errors in its application – from incorrect flow to contamination in the system. Below, we present the most common mistakes and how to avoid them.
Shield gas flow that is too low or too high
A flow that is too low (below 6 l/min) does not provide effective arc shielding – air enters the weld zone, causing oxidation, porosity, and weld discoloration.
A flow that is too high (over 15 l/min) creates turbulence and also draws in ambient oxygen.
How to avoid: For most applications, use 8–12 l/min for Ar and 15–18 l/min for Ar+He mixtures; adjust the settings according to the nozzle diameter and welding position.
Contaminants in the gas and supply system
Even trace amounts of oxygen, moisture, or oil can cause discoloration and porosity in the weld.
How to avoid: Use at least Class 4.6 gases (99.996% purity), store cylinders in a dry place, and regularly check the tightness of regulators, hoses, and quick connectors.
Lack of control over pre-flow and post-flow parameters
Insufficient gas flow time after welding causes the hot tungsten electrode to oxidize and lose its durability.
How to avoid: Set the pre-flow to 0.5–1 s and the post-flow to 5–10 s (more at higher currents). This allows both the electrode and the weld to cool in the gas shield.
Excessive tungsten electrode extension
When the electrode extends too far beyond the nozzle, the gas shield is ineffective – discoloration, an unstable arc, and oxide inclusions occur.
How to avoid: The electrode should typically extend 3–6 mm beyond the nozzle; when welding in hard-to-reach areas, it is advisable to use a gas lens, which increases the protection zone.
Lack of back purging
When welding stainless steel pipes and tanks, the lack of an internal shield leads to the formation of oxides, known as “welding sugar,” which weakens corrosion resistance.
How to avoid: Use an internal shield of pure argon (4–8 l/min) until the weld has completely cooled.
Incorrect gas selection for the material
Using an argon-hydrogen mixture (Ar + H₂) for welding aluminum or copper leads to blisters and microcracks.
How to avoid: Use Ar + H₂ only for austenitic stainless steels, and choose Ar + He for aluminum and copper.
Failure to clean components and equipment
Greases, dust, and oxide residues on the metal surface disrupt the arc’s stability and lead to weld defects.
How to avoid: Always clean the surface with acetone or a stainless steel brush before welding; clean nozzles and electrodes regularly.
Excessively long arc
A long arc causes heat dissipation, instability, and gas inclusions.
How to avoid: Maintain an arc length approximately equal to the electrode’s diameter—usually 2–3 mm.
How to Choose the Perfect Shielding Gas for TIG Welding?
Choosing the right shielding gas is one of the most important factors in determining the success of a TIG welding process. The type and purity of the gas determine the arc stability, the appearance and durability of the weld, and the efficiency of the entire process.
Pure argon (Ar) is the most universal choice – it provides a stable arc, easy ignition, and ideal metal protection when welding most materials, including stainless steel and aluminum.
Argon-helium mixtures (Ar + He) increase the arc temperature and allow for deeper penetration and faster welding speeds, which is important for thick aluminum and copper components.
Argon-hydrogen mixtures (Ar + H₂) are effective for austenitic stainless steel, where aesthetics and corrosion resistance are key – hydrogen smooths the weld bead and accelerates the process, but is not suitable for active metals like aluminum.
In addition to selecting the gas itself, the following operating parameters are crucial:
shielding gas flow (8–12 l/min for Ar, 15–18 l/min for Ar+He),
pre-flow and post-flow control,
gas purity (min. class 4.6),
and the tightness and cleanliness of the installation.
The right combination of gas type, parameters, and work technique allows you to achieve high-quality, clean, and resistant welds, regardless of the material type.
The Deffor team will help you select the optimal welding parameters, select the gas for your application, and optimize the process to ensure every weld is durable, clean, and compliant with industry requirements.
Which shielding gas is best for TIG welding?
The most commonly used shielding gas for TIG welding is pure argon (Ar). It provides a stable arc, a smooth weld, and excellent protection against oxidation. In some cases, mixtures of argon with hydrogen (Ar + 2–5% H₂) or helium (Ar + 25–75% He) are also used, depending on the material being welded.
How to choose the right shielding gas for the material type?
Austenitic stainless steel → Ar or Ar + 2–5% H₂ – for better appearance and faster welding speed.
Carbon steel → pure Ar or Ar + 30% He – for thicker components.
Aluminum and copper → Ar + 25–75% He – helium increases the arc temperature and penetration depth.
Nickel alloys and high-alloy metals → Ar 5.0 or Ar + He – for maximum weld purity.
Does hydrogen in the gas mixture improve weld quality?
Yes, a small addition of hydrogen (1–5%) improves weld wettability, smoothness, and gloss, especially on stainless steel. However, hydrogen should not be used when welding aluminum, copper, or ferritic steels, as it can cause blisters or hydrogen cracking.
Why is helium added to argon?
Helium (He) increases the arc temperature and allows for deeper weld penetration. Therefore, Ar + He mixtures are used for thicker components made of aluminum, copper, and high-alloy alloys, where pure argon would be insufficient.
What should be the purity of the shielding gas for TIG welding?
TIG welding processes should use gases with a minimum purity of 99.996% (class 4.6). Contaminants (oxygen, moisture) lead to weld porosity and oxidation. The principles of gas quality are defined in the PN-EN ISO 14175 standard.
What shielding gas flow should be set for TIG welding?
The recommended flow is 8–12 liters per minute, and for larger torches, up to 15 liters per minute. Too little flow causes oxidation and porosity, while too much causes turbulence and arc instability.
What are the most common errors when using shielding gas?
Too low or too high a gas flow.
Lack of shielding gas back purging.
Using contaminated gas or a leaky installation.
Excessive tungsten electrode protrusion.
Incorrect gas mixture selection for the metal type.
What benefits does back purging provide?
It protects the inner surface of the weld – especially when welding stainless steel – from oxidation. This ensures the joint remains corrosion-resistant and maintains a smooth surface. Pure argon gas is used at a flow rate of 4–8 l/min.
What is the importance of arc length and post-flow time?
An arc that is too long causes oxidation and spatter.
A post-flow time that is too short exposes the hot electrode to air. It is recommended to set the post-flow time to 5–10 seconds after welding.
What are the universal recommendations for TIG welding?
Use only pure gases of class 4.6 or better.
Regularly check the gas system for leaks.
Maintain a stable flow rate of 8–12 l/min.
Adjust the gas mixture to the material type and component thickness.
Do not omit the backside shielding when welding stainless steel.
