Different Types of Gases Used for Welding

If you’re new to welding, you may be wondering what all the different welding gases are what they are used for. Welding gases are critical elements for a sleek, stable weld. We use them to protect the weld from unwanted chemical reactions and influence the look and strength of the job.

While traditional stick welders knew very little about gases with their welding, the rise of the MIG and TIG welding machines over the last 70 – 80 years has brought in the need for welding gas as a common commodity in most workshops.

As we jump into the leading gases and mixtures used in the welding world, it’s fascinating to learn how much we have progressed over the short time since they were first implemented. The progression is enormous, and what’s in store for new gases, or new ways to use these gases, is exciting.

In this article, we’ll explore the different types of welding gas and their uses.

Why Is Gas Used In Welding?

Welding gas is used in a range of different ways. These include shielding the arc from impurities like air, dust, and other gases; keeping welds clean on the underside of the seam opposite the arc (or purging); and heating metal. Blanketing gases are also used to protect metal after the welding process.

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Inert and Reactive Gases

Gases come in two categories: inert or reactive. Inert gases do not change or create change when in contact with other substances or temperatures. Reactive gases do the opposite. They react in different circumstances, creating a change of state in the other substances and/or themselves.

Inert gases are useful, as they allow welds to be achieved naturally without unwanted occurrences weakening or distorting the weld. Reactive gases provide a positive change during the process of the weld, which enhances the way the material is fused.

Shielding gas

When the air gets into the arc while you’re welding, it causes air bubbles to form within the molten metal, creating a weak and very ugly weld. You cannot MIG or TIG weld without a shielding gas unless the filler material being used is flux-cored or flux coated. This serves the same purpose as a shielding gas, keeping impurities out, but in a different way.

Most shielding gases are inert, which makes them ideal for shielding a welding process as they remain stable under welding’s extreme conditions. They also nurture the weld in different ways, depending on the gas being used, including more penetration, more fluidity when molten, and a smoother surface on the bead.

Purging gas

Purging gases are used to cover the underside of the material you’re welding in the same way a shielding gas does, only it’s done separately from the natural process of the weld.

While you weld the top of a joint, the bottom of the joint is sealed off and has a flow of gas purging it. It’s frequently used with stainless steel items, and it can be the same type of gas or a different gas than what’s used on the top of the joint.

Heating gas

Certain welding, like gas welding and brazing, requires gas to heat the metal or the filler rods to achieve the welding. This replaces the need for an arc.

Specific types of welding require the metal to be preheated before welding, which this gas is used for. The gas is simply a fuel mixed with air or oxygen, which is lit by a flame to warm or melt the metal.

Blanketing gas

Blanketing is a process where tanks and confined spaces are filled with gas after they’re completed to keep air and other contaminants from damaging or staining the finished product.

Sometimes it’s used to fill the completed projects entirely. Other times, the gas is added to the air-filled tank, creating a mixture to keep the tank pure against other gases or reactions.

welding gas

What Are the Different Gases Found in a Welder’s Shop?

So now that we have an understanding of the primary uses of gas in welding, it’s time to learn about exactly what the different types are and how they are used.

1. Argon Gas

Argon is an inert gas, meaning it should not react with other substances. That is what people thought until they found it changes form at high temperatures. It’s the third most abundant gas on earth and is brilliant for keeping environments unreactive, for example, in a light bulb to keep the air from consuming the glowing filament.

What is its welding purpose?

Argon is used as a shielding gas to keep air out of a welding arc. It’s used in both the primary welding stage and to purge the backside of the joint. It’s the most commonly used shielding gas and is often found in shielding mixtures for MIG welding operations.

2. Helium (He) Gas

Did you know helium is one of the only substances that doesn’t freeze? Bring its temperature below about 450° F, and it turns into liquid. It’s used in many scientific experiments, and in rockets, decorative and scientific balloons, and hypersonic wind tunnels.

We’ve all had our share of fun using helium with balloons or as a voice modifier, but it’s actually a very precious gas vital to human progression. It’s the second most common gas in the universe, but on Earth, it’s not abundant like other gases and is challenging to produce.

Because over six billion cubic feet of it is consumed every year, the supply is gradually diminishing. A few helium-collecting space trips might be necessary soon.

What is its welding purpose?

Helium is used as a shielding gas, in both its pure form and as a mixed solution with other gases in MIG and TIG welding. It provides deeper penetration and brings a higher heat input to welds, but struggles to provide consistent arc starts.

It creates a good mix when used with argon. The argon excels inconsistent arc starts, and the helium adds the extra heat needed for specific applications like welding aluminum, and TIG welding in particular.

3. C02 Gas

Carbon dioxide is what we exhale when breathing, and it’s also created from organic matter. This makes it a very common gas on earth. Industrial C02 used in workshops and other industrial sites is captured from natural gas and then compressed in a pressure tank.

What is its welding purpose?

C02 is used as a shielding gas. It’s less expensive to buy, but it doesn’t produce the same quality welds as argon does, and it has issues like more spatter during the welding process. This is why it’s more commonly used in mixtures, rather than in its pure form.

Applications using its pure form include flux core welding, some carbon steel MIG welding, and plasma shielding.

4. Compressed Air

This is the stuff we breathe but in a compressed form. It’s a mix of 78% nitrogen, 21% oxygen, and 1% other particles. When compressed, a massive volume of air is squashed into a tighter space than it would typically fit into.

It is forced into the tank, creating significant pressure. When it’s released, it comes out with urgency into the application you’re using it for.

What is its welding purpose?

Although air isn’t used in the welding process because it contaminates the weld, it’s used in many other ways in a welding workshop. Many shops use compressed air to clean off dust, swarf, and other dry matter around the workshop. Air nozzles attached to compressors with hoses shoot air out to blow off the dirt.

It’s also combined with fuel to create flames that preheat metal before welding. An even heat transfer or a lower transition from cold to hot is necessary for certain materials while welding, including high carbon steel. This is why preheating is sometimes necessary.

5. Oxygen Gas

Almost all life is dependent upon this vital gas. It’s odorless, colorless, and tasteless, and many people consider it a more passive and friendly gas than most others. It’s actually one of the most reactive gases in the world. It’s found in most living organisms and combines with every other gas except inert gases.

What is its welding purpose?

It’s mixed in small quantities of shielding gases to add fluidity to the molten pool and speed to the welding process. It’s used to amplify heat with fuel for gas welding and oxy-cutting metals, and when mixed with acetylene, it creates the only flame hot enough to weld steel.

Gas welding with oxygen also provides a sufficient shield to protect some metals from needing a shielding flux filler wire.

6. Acetylene gas

This highly flammable gas is widely used to produce chemicals for other industrial purposes. It’s highly combustible when mixed with air.

What is its welding purpose?

Acetylene is used as fuel for oxy-cutting and oxy-welding. When mixed with oxygen, it’s the most effective gas to form a flame hot enough to cut and weld most metals with ease. It’s more expensive than some other fuel types, but it’s the best type of fuel to use.

7. Nitrogen (N) Gas

As the most abundant gas in our atmosphere, covering close to 80% of the earth’s surface and being a part of every living organism, nitrogen is essential. It’s used to preserve and protect many new products like food, motors, tanks, and anything that could be damaged by too much oxygen or other gases.

What is its welding purpose?

Nitrogen can be used by itself as a shielding gas for laser welding and plasma cutting, and it’s used in some heat treatments. It’s also mixed with other shielding gases for specific applications, but it’s not suitable for carbon steel. When shielding nitrogen-rich metals, it increases the alloy’s mechanical properties and can deepen penetration while stabilizing the arc.

Nitrogen is also used as a blanketing gas once welding is finished inside tanks and enclosed spaces, to preserve the material until it’s used with its intended product.

8. Hydrogen (H) Gas

As the simplest of all the gases, hydrogen is a fuel that the stars, like our Sun, use to burn. It’s abundant on Earth, easy to produce, and burns without emissions while producing water as its final byproduct.

Aside from being the main element in water, in its raw form, it’s used heavily for commercial purposes. It’s used in food products like peanut butter and oils, and to create essential chemicals such as ammonia.

What is its welding purpose?

Surprisingly, hydrogen is used as a shielding gas in mixtures with argon or C02. Some people are frightened by this thought because it’s combustible.

There is a specialized welding process called atomic hydrogen welding, which uses 100% hydrogen in its raw form and produces an arc heat range between 6100° F and 7200° F. This is hotter than an acetylene torch can reach cranking at its hottest.

The process is used to weld materials with extremely high melting points, like tungsten. This kind of hydrogen welding is dangerous.

However, due to the percentage of hydrogen used in standard welding procedures, it’s actually very safe. There are risks of weld cracks when hydrogen is used in the shielding gas, but applying protective layers to the weld solves this.

Hydrogen is otherwise an excellent shielding gas choice, due to its capacity to produce incredible heat in welds. This increases penetration and makes a much cleaner weld than other gases can produce.

Common Gas Mixtures use in welding

Different gas mixtures produce different effects in a weld. Depending on the materials you’re using, you’ll want to choose your mix appropriately.

Let’s explore the most common gas mixtures in welding, what processes to use for each one, and what metal to use it on.

Argon/CO2

Argon and carbon dioxide can mix at various consistencies, anywhere from 5 to 25% carbon dioxide, for different levels of control and effect on the weld. We use these mixtures most commonly on low alloy or carbon steel.

Argon/CO2 combinations help balance the most extreme effects of each gas. Higher argon helps decrease the spatter and smoke created by CO2, while high CO2 helps with short-circuit transfer and better penetration of heavier metals. Higher CO2 will begin to increase alloy depletion, and over 20% starts becoming unstable.

Welders use these gas mixtures in:

  • Gas metal arc welding (GMAW) on carbon steel
  • Flux-cored arc welding (FCAW) on carbon steel
  • Flux-cored arc welding (FCAW) on stainless steel

Argon/O2

Introducing minimal concentrations of oxygen to argon in a shielding gas will considerably improve the downsides of pure argon. By helping with heat transfer, the oxygen increases the droplet rate and keeps the weld pool in a molten state for a more extended period. This extra time enables the metal to flow and fuse more consistently across the weld and flattens the bead.

Use argon/O2 mixtures for the following welding processes and metals:

  • Gas metal arc welding (GMAW) on stainless steels
  • Gas metal arc welding (GMAW) on carbon steel

Argon/CO2/O2

This tri-mix is incredibly versatile and can be used successfully on a wide variety of metal thicknesses. CO2 increases deeper penetration, while oxygen helps with efficiency, giving you a good spray transfer with a lower voltage.

Some people call this the “universal mixture” because you can use it with spray transfer, short circuit, and globular transfer. We use it in the following processes:

  • Gas metal arc welding (GMAW) on carbon steel
  • Gas metal arc welding (GMAW) on stainless steel in some cases

Argon/Helium/CO2

This tri-mix helps increase the heat transfer compared to pure argon, which gives a better bead result and fuse. The addition of helium works similarly to argon and oxygen, but since helium is inert, you don’t risk oxidation occurring.

Mixtures with more helium (up to 90%) promote short-circuit transfer. The argon and carbon dioxide help stabilize the arc and increase penetration.

Mixtures with more argon (up to 80%) promote spray transfer with the helium giving a smoother bead profile and wetting.

Argon/Helium/CO2 is best for the following processes:

  • Gas metal arc welding (GMAW) on stainless steel
  • Flux-cored arc welding (FCAW) on carbon steel
  • Flux-cored arc welding (FCAW) on stainless steel

Argon/Helium

You’ll see argon/helium mixes used on reactive metals and non-ferrous metals like copper, nickel alloys, or aluminum. Usually, you can use pure argon, but higher helium concentrations work on heavier materials, reducing penetration.

The helium increases the heat on the surface, giving a more fluid weld pool. The fluidity allows air bubbles or impurities to rise to the surface and escape, reducing the porosity of the final product.

We use this mix most commonly in:

Argon/Nitrogen

Though not a typical mix, argon and nitrogen work together if you keep a very low nitrogen concentration. The added nitrogen helps produce a completely austenitic (low-corrosive, non-magnetic) stainless steel weld. Higher nitrogen levels increase fumes and porosity.

Argon and nitrogen mixes can be used with: Gas metal arc welding (GMAW) on 347 stainless steel

Argon/Helium/O2

A mixture of argon, helium, and oxygen can increase arc energy and surface heat when welding on ferrous materials. You would typically use just helium and argon for this purpose on non-ferrous materials.

This tri-mix increases the fluidity of the weld pool, giving an even bead profile and less porosity. Gas metal arc welding (GMAW) on ferrous materials

Argon/Hydrogen

Argon and hydrogen are a less common mixture but can be used to weld austenitic steel using gas tungsten arc welding (GTAW), also known as the TIG method.

Hydrogen is added to argon to increase the speed and bead profile of the final weld. It helps maintain a narrow and precise arc while increasing heat transmission. Gas tungsten arc welding (GTAW) on austenitic steel

Argon/CO2/Hydrogen

Low amounts of carbon dioxide and hydrogen can be added to argon to support arc stability, minimize carbon pick-up, and increase wetting on stainless steel welding. You should not use this blend on low alloy steels as it will cause significant issues with cracking.

Gas Welding Safety

Storage and Handling

  • Keep cylinders away from physical damage, heat, and tampering.
  • Securely chain equipment to prevent falling.
  • Store away from flammable and combustible materials.
  • Store extra gas and oxygen cylinders separately.
  • Store in an upright position.
  • Close cylinder valves before moving.
  • Protective caps or regulators should be kept in place.
  • Roll cylinders on bottom edges to move—Do not drag.
  • Allow very little movement when transporting.

General Gas Welding Safety Tips

  • Inspect equipment for leaks at all connections using approved leak-test solution.
  • Inspect hoses for leaks and worn places.
  • Replace bad hoses.
  • Protect hoses and cylinders from sparks, flames, and hot metal.
  • Use a flint lighter to ignite the flame.
  • Stand to the side (away from the regulators) when opening cylinder valves.
  • Open cylinder valves very slowly to keep sudden high pressures from exploding the regulators.
  • Only open the acetylene cylinder valve ¼-¾ turn; leave wrench in place so the cylinder can be quickly closed in an emergency.
  • Open and light acetylene first, then open and adjust oxygen to a neutral flame.
  • Follow the manufacturer’s recommendations for shutting off the torch. If the guidelines are not readily available, the commonly accepted practice is to close the oxygen valve first.
  • When finished, close cylinder valves, bleed the lines to take pressure off regulators, neatly coil hoses, and replace equipment.
  • Have a fire extinguisher easily accessible at the welding site.