What Gases Are Used for TIG Welding?

Argon is the main shielding gas used for TIG welding. Helium and various gas mixtures can also be used depending on the specific application and metal being welded.

In this guide, we’ll explore the different gases used in TIG welding in more detail. We’ll discuss their properties and show you how to select the right gas for your welding projects.

Understanding Shielding Gases in TIG Welding

Shielding gases in TIG welding protect the weld pool from atmospheric contamination. Without proper shielding, oxygen and nitrogen from the air would react with the molten metal and cause porosity, embrittlement, and oxidation.

TIG welding requires inert gases that won’t react with the weld pool. This is why it’s called Tungsten Inert Gas welding in the first place.

Your chosen shielding gas also influences:

• Arc stability
• Penetration profile
• Overall weld quality

That’s why the right gas can make the difference between a strong, clean weld and one that requires significant revisions.

Pure Argon: The Industry Standard for TIG Welding

Pure argon is by far the most commonly used shielding gas for TIG welding. It works well on virtually all weldable metals, which makes it incredibly versatile.

Argon is particularly effective for welding:

•  Aluminum
• Magnesium
• Carbon steel
• Stainless steel
• Titanium

Its relatively low cost and widespread availability make it the default choice for most welding operations.

Argon’s inert properties provide excellent arc stability and control, especially at lower amperage settings. This makes it ideal for precision work on thin materials.

Argon is also heavier than air, which means it provides good coverage over the weld pool without requiring excessive flow rates. Typical flow rates for argon range from 15-20 cubic feet per hour (CFH) for most applications.

Pure argon is particularly valuable for welding aluminum and magnesium because it works exceptionally well with AC welding. The cleaning action during the electrode positive cycle helps remove oxide layers from these reactive metals.

Helium and Helium-Argon Mixtures

Helium is another inert gas used in TIG welding, though less commonly than argon because of its higher cost focus on specific applications.

Pure helium or helium-rich mixtures increase heat input to the weld, resulting in deeper penetration and faster travel speeds. This makes helium advantageous when welding thicker sections of aluminum, copper, and magnesium alloys.

The higher thermal conductivity of helium produces a wider, more fluid weld pool. This helps reduce the risk of incomplete fusion when welding highly conductive materials like copper.

Helium-argon mixtures typically contain 25-75% helium, with the balance being argon. These blends offer a compromise between the stability of argon and the increased heat input of helium.

When using helium, flow rates must be increased by around 50% compared to argon due to helium’s lower density. Typical flow rates for helium-based gases range from 25-35 CFH.

A significant drawback of helium is that it’s becoming increasingly expensive and less readily available. It’s a non-renewable resource extracted primarily from natural gas deposits, and global supplies are limited.

Specialized Gas Mixtures for Specific Applications

For certain stainless steel applications, small amounts of hydrogen (1-5%) may be added to argon. This addition increases heat input and provides a cleaner, more fluid weld pool with better wetting characteristics.

Hydrogen-containing mixtures should only be used on austenitic stainless steels. They should never be used on carbon steel or ferritic stainless steels due to the risk of hydrogen embrittlement.

Tri-mix gases containing argon, helium, and hydrogen may be used for extremely thick materials or applications requiring maximum penetration. These specialized mixtures are typically only needed in industrial settings with unique requirements.

Nitrogen additions are occasionally used for duplex stainless steels to maintain nitrogen content in the weld metal, though this is a specialized application that requires careful parameter control.

It’s worth noting that, unlike in MIG welding, active gases like carbon dioxide or oxygen aren’t  used in TIG welding. These reactive gases would damage the tungsten electrode and compromise weld quality.

Practical Considerations for TIG Welding Gas Selection

Budget constraints often influence the gas choice for TIG welding. Pure argon is the most economical option, so it’s seen in most welding shops. The higher cost of helium and specialty mixtures must be justified by specific project requirements.

The thickness of the material being welded is another key factor in gas selection. Thinner materials (under 1/8″) typically work best with pure argon, while thicker materials may benefit from helium-containing mixtures.

Metal type also dictates gas selection, specifically:

• Aluminum and magnesium work well with pure argon under AC
• Stainless steel can benefit from hydrogen additions
• Copper often requires helium for adequate penetration

Weld quality requirements must also be considered to ensure proper gas selection. For critical applications with strict quality standards, specialized gas mixtures may be justified despite their higher cost.

Finally, availability is another practical concern. While argon is readily available in most locations, helium and specialty mixtures may require special ordering or have limited local availability.

Choose Your TIG Welding Gas Wisely

While pure argon is the workhorse shielding gas for TIG welding across most applications, helium mixtures or specialized additives can be used for challenging materials and thicknesses.

Proper gas selection combined with appropriate flow rates and delivery methods, ensures the high-quality, contamination-free welds that make TIG welding the preferred process for critical applications.