Guide to Welding Gases and Mixtures

There are many welding techniques and processes, and some involve the use of compressed gases, also called shielding gas. Shield gases play an important role in welding, and it is crucial to understand how different types of gas influence welding outcomes and know how to choose the best one for your application.

What Are Shielding Gases?

Shielding gases shield or protect a weld from atmospheric contamination. Elements like oxygen, nitrogen and hydrogen can result in defects in the weld, so the shield gas acts as a protective layer between the environment and the weld puddle.

There are different types of welding gases, and they fall into two main categories:

• Inert gases: Inert gases are inactive or nonreactive. This means they do not change or alter anything in the welding process — their role is more for protection and prevention against unwanted reactions with the atmosphere. The most common examples of inert welding gases are argon and helium.
• Active gases: Active gases take an active role in the welding process, meaning they can exert influence over things like arc characteristics, weld pool fluidity and weld metal composition. In most cases, active gases are added or mixed with inert gases with a specific result in mind — improving arc stability, enhancing the weld bead profile or increasing penetration. Common active welding gases include carbon dioxide, oxygen and nitrogen.

Gas Mixtures for Different Types of Welding

Gases in their pure form may not always be right for certain welding applications. Some gases require mixing, while other gases can benefit from enhanced properties from mixing with others. Argon, helium and carbon dioxide gases operate well on their own or in mixtures. Meanwhile, oxygen, hydrogen and nitrogen work best when mixed.

Discover the best welding gas mixture ratios for different types of welding techniques:

MIG Welding Gases

Metal inert gas (MIG) welding, or gas metal arc welding (GMAW), is a traditional welding technique that uses an electric arc to fuse two metals together. MIG welding can use a wide range of inert, active and mixed gas options, such as:

• Pure carbon dioxide: Carbon dioxide is common in MIG welds because of its cost-effectiveness and high penetration. On its own, it can work well for carbon steel welding, though it produces a more unstable arc and spattering, and is generally more effective in mixtures.
• Pure argon: Argon provides good protection from atmospheric contaminants because of its weight. It is generally more stable and produces less spatter and penetration. It can be used in MIG welding for metals like copper, titanium or aluminum, but is more often mixed with other gases. 
• Argon and carbon dioxide: Argon, known for its stability, works well in MIG welds when mixed with carbon dioxide, which can add heat and improve penetration. Common ratios for this mixture include 75% argon to 25% carbon dioxide or 90% argon to 10% carbon dioxide. This mixture is ideal for metals like carbon steel and mild steel. 
• Argon and oxygen: One of the most common gas mixtures for stainless steel welding, argon and oxygen produce a stable arc, better penetration and a nicer weld bead. Most argon-oxygen mixtures for MIG welds involve 5% or less oxygen gas.

TIG Welding Gases

Tungsten inert gas (TIG) welding or gas tungsten arc welding (GTAW) is similar to MIG welding, except the filler metal is added to the weld pool separately from the arc. Argon is the most common and versatile gas in TIG welding, both on its own and in mixtures:

• Pure argon: One hundred percent argon is most common in TIG welding because it is inert, has good arc stability and produces cleaner welds. Using high-purity argon can reduce contamination and produce higher-quality welds. It works with a wide variety of metals, including stainless steel, aluminum, titanium and aluminum alloys.
• Argon and helium: This is the best gas mixture for aluminum welding, as well as nickel alloys and copper. Adding helium to argon helps tailor the weld for thicker materials or those with higher thermal conductivity. The most common ratios are 75% helium to 25% argon, or an even 50-50 mix.
• Argon and hydrogen: While less common, an argon-hydrogen gas mixture can increase weld cleanliness and travel speed. Ratios often include 15% or less hydrogen, and these gas mixtures work best for TIG welding for stainless steel. Because of hydrogen’s volatility, special safety precautions are necessary.

In general, TIG welding tends to use pure argon except in cases that involve thicker materials or need a higher heat input to produce the desired results.

FCAW Welding Gases 

Flux-cored arc welding (FCAW) is another welding technique that uses shielding gas mixtures. The type of flux-cored wire dictates the appropriate shielding gas, so it is best to check with the wire manufacturer for the right recommendations. The shield gas for FCAW provides additional protection on top of that which is supplied by the flux core. Common shield gases for FCAW include:

• Pure carbon dioxide
• Argon and carbon dioxide

In some cases, a small amount of oxygen can be added to argon-carbon dioxide mixtures to increase arc stability and weld pool fluidity.

Explore All Welding Gas Mixtures

Shield Gas Welding Best Practices

To ensure a good weld, follow these best practices:

1. Select the right gas: Different gases and gas mixtures have different chemical properties, which will affect how the welds turn out. Double-check that you are using the right gas for both the welding technique and the metal to get the results you want.
2. Optimize gas flow: You can optimize gas flow with the right gas valve selection. Make sure the gas flow is appropriate to maintain proper weld quality while reducing waste.
3. Use the proper regulator: Ensure consistent and safe gas delivery with the right regulator. Gas regulators are designed to strict safety standards to keep the gas flowing at the right pressure. When choosing a regulator, ensure it suits the type of gas you are using and can handle the inlet and outlet pressure for your application.
4. Inspect equipment regularly: All equipment for gas welding should be properly maintained with consistent maintenance and regular inspections.

Safety and Regulations for Welding Gases

Working with compressed gases — whether you are performing complex welds or filling balloons for a party — requires special safety precautions. Refer to the Compressed Gas Association for the list of standards, and review these safety requirements for welding gases:

Handling and Storage

It is important to understand what kinds of gases you have in your facility, so check all canister labels before handling or storage. Be sure to refer to the safety data sheet for every gas you use.

Poorly handling compressed gas cylinders can result in leaks and explosions. The best way to transport gas for welding is with cylinder carts. If one is not available, it is best to roll the cylinder rather than attempting to carry it and risk dropping it. Store all cylinders upright in a well-ventilated area and away from direct sunlight or heat sources.

Ventilation and Respiratory Protection

When welding with shield gases, toxic gases and fumes are a dangerous by-product that pose risks to worker health and safety. Ensure the space is sufficiently protected for the kinds of welding activities — a local exhaust ventilation system provides the best protection when working with gases or high-intensity welds.

Personal protective equipment for welding is extensive. When working with gases, workers should use gloves, appropriate shoes, eye protection and ventilators. Though welders may already use respirator masks, make sure the ventilation is appropriate for the type of gas they are working with. 

Emergency Protocols

It is vital to have a plan in place in case of gas emergencies. Ensure all employees know how to report a gas leak and the proper procedure for handling gas exposure. Proper training and safe handling of gases is the best way to prevent emergencies, and it can ensure compliance with relevant safety regulations and standards.

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Meritus Gas Partners Is Your Trusted Source for Industrial Gases and Welding Supplies

Meritus Gas Partners supplies gases and welding equipment for businesses in various industries. Our partners can provide industrial gas cylinders as well as bulk and microbulk gas solutions. We can also accommodate custom gas mixes, allowing you to tailor your shield gas mixture to the outcome you desire.

Explore more tailored welding solutions from Meritus Gas Partners and find a partner near you.