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Welding gases are vital for any welding job as they play crucial roles, such as shielding the arc from dust and other impurities and heating the metal. However, there are various gas types used in welding for different purposes. If you are a new welder or even an experienced one that wants to be sure of the correct welding gas to use, here we look at some of the most common types and their uses to ensure you know what you require for varying welding tasks.
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What is the Purpose of Gas in Welding?
Besides just shielding an arc from impurities, a welding gas does much more, including protecting the metal after welding. Here is a more detailed breakdown of the purpose of gas when welding.
Inert and Reactive Gases
Gases are typically either inert or reactive. The inert gases will not change even when they contact other substances, while the reactive ones create a change in state or change the different materials they touch.
Given they do not change, inert gases come in handy when you want to achieve a natural weld without distortion from the welding gas changing its state. On the other hand, reactive gases are ideal for enhancing how the materials fuse when welding.
Shielding Gas
When air and other impurities get into your weld, it can get weak and ugly. These foreign materials often form air bubbles in the molten metal, affecting how it settles once hardened. A shielding gas protects the weld from air and impurities like dust.
For both TIG and MIG welding, you cannot weld without using a shielding gas, and this is more so if you do not have a flux coated filler wire. Flux-coated and flux-cored filler materials serve the same purpose as shielding gas but work differently.
Shielding gases are typically inert, meaning they remain stable even when exposed to high heat and other extreme conditions.
Purging Gas
Purging gas works the same way as a shielding gas. However, it covers the underside of the material you are welding, and it is not part of the regular weld process. As you fuse the top section of the material, a purging gas helps seal the joint’s bottom part to ensure you end up with a better quality weld.
Heating Gas
As the name suggests, the heating gas helps heat the filler wire and metal you intend to weld, ensuring they will be ready for welding. Heating gases can eliminate the need for an arc and are very handy for welding types where you first need to pre-heat the metal. This gas is often a type of fuel mixed with oxygen.
Blanketing Gas
While blanketing is not very common when welding, it ensures the weld you make is not contaminated or even stained after finishing the job. Here, the space around your weld is filled with gas to keep up any impurities in the air.
10 Different Types of Pure Welding Gases
1. Argon
Argon is one of the most common pure welding gases, and it is one of those basic ones you can almost be certain every welder will use at some point. It is an inert gas that will not react with any other substances, making it very ideal for keeping environments around the weld unreactive.
Welding Purpose: In most instances, argon’s purpose is to keep air out of the welding arc, which makes it vital for the primary welding stage. However, argon also comes in handy for purging the underside of the weld joint.
2. Carbon Dioxide
Carbon dioxide comes from organic matter, and it is also a prevalent gas given that it is what many animals breathe out. However, the industrial-grade one used for welding comes from natural gas.
Welding Purpose: Like argon, carbon dioxide is often used as a shielding gas. Carbon dioxide is a more affordable option, but the weld quality it provides is not as good since it spatters a lot. However, mixing it with argon seems to address this issue, but some jobs like carbon steel MIG welding and flux core welding might require the use of this gas in its pure state.
3. Oxygen
Oxygen is an odorless, tasteless and colorless gas. Given that people breathe it, many often assume it is a passive or even friendlier gas type, which could not be further from the truth. Oxygen is one of the most reactive gases and can be pretty dangerous to use.
Welding Purpose: Oxygen supports oxyfuel cutting, and it is often added to shielding gasses in a small quantity to enhance their effectiveness and speed up the welding jobs. Other purposes of oxygen include welding steel when mixed with acetylene.
4. Helium
Helium is quite a unique gas, given it is one of the few substances in the world that will not freeze. Despite being one of the most abundant gases in the universe, it is in short supply on earth, and its production is often quite hectic. Hence its supply is steadily dwindling.
Welding Purpose: For welding, the primary purpose of helium is to create an inert shielding gas. Helium effectively prevents oxidation when dealing with materials like aluminum, copper, magnesium alloys, and stainless steel. What’s more, the addition of helium can increase the weld pool’s travel speed and fluidity.
5. Hydrogen
Hydrogen is an abundant gas on earth, and it is often regarded as one of the simplest among all welding gases. This gas is more straightforward to produce than most others and burns more cleanly with no emission since water is the final byproduct.
Welding Purpose: When welding, hydrogen works as a shielding gas, and it is often part of a mixture that includes argon and carbon dioxide. Additionally, it is also used for atomic hydrogen welding with is a unique form of welding that uses pure hydrogen. This type of welding is used for metals like tungsten with high very high melting points.
6. Nitrogen
About 80% of the earth’s surface is covered by nitrogen, making it the most abundant gas type in the atmosphere. Nitrogen is part of every living thing, and it is widely used to preserve and protect various kinds of products from the damaging effects of exposure to oxygen.
Welding Purpose: Nitrogen can be an excellent shielding gas for you when laser welding and plasma cutting. Also, you can use it as a purging gas for stainless steel tube welding, and it works well as a blanketing gas once you finish welding in enclosed spaces.
7. Acetylene
Acetylene is among the most dangerous welding gases you can use, given it can be highly combustible when mixed with the air. In most instances, it is used to produce chemicals for industrial use.
Welding Purpose: Acetylene works best for oxyfuel welding jobs. However, it is also great for brazing, welding and even cutting steel alloys, provided they are not thicker than 1-inch.
8. Propane
Propane, or LPG as it is better known, is a highly combustible gas that is often used as a fuel source in different contexts.
Welding Purpose: Propane is not typically used as a primary gas for welding despite the fact it burns very hot. Unlike acetylene, it does not form a reducing zone when burning in oxygen. However, it is used for brazing after making the weld and can also be used for the oxyfuel process for scrap yards where the cut’s quality is not vital.
9. Propylene
Propylene gas burns hotter than propane and many other welding gases out there. But, it is not necessarily a pure welding gas since it often has an oxygen blend. Many welders often have an issue with the fact this gas comes in small canisters that do not work very well for welding.
Welding Purpose: Propylene gas is highly suited for welding applications like brazing, heating metal, and even non-structural fusion welding.
10. Compressed Air
Since compressed air is just “air’, it is often the cheapest welding gas type you can get. Sometimes it is purified a little to improve its quality, and when you mix it with a fuel source, you should get a strong enough flame for welding.
Welding Purpose: Compressed air is used mainly by welders to get more control over the thickness of carbon coating over their weld.
Common Welding Gas Combinations
For most welding jobs, you will typically end up using a gas combination mixture with a percentage of the different gases depending on the application. Some of the most common welding gas combinations include the following.
1. Argon and CO2
Argon and carbon dioxide mix is the most common option for shielding when welding. Typically the argon makes up the highest percentage of the mixture because, in most instances, you get between 80% and 95% of it, while carbon dioxide is only about 5% to 20%.
Having more argon than carbon dioxide in the gas mix ensures you get a pleasantly smooth weld with no spatter. For this gas combination, it is essential to note that the thicker the metal you are welding, the more carbon dioxide you need.
2. Argon, CO2, and Oxygen
Sometimes, oxygen is added to the argon and carbon dioxide mixture to create relatively more fluidity for the weld pool. For this gas composition, oxygen forms less than 5% of the total volume.
The good news is that this mix still provides the spatter-free welds you get with the argon and carbon dioxide combination and comes with the advantage of speeding up the job.
3. Argon, Helium, CO2
Depending on the gas’s purpose, you can get mixtures dominated by either helium or argon and a small carbon dioxide percentage. One of the most common combinations includes 90% helium, 7.5% argon and 2.5% carbon dioxide. These gas compositions are best suited for welding metals such as aluminum, stainless steel or carbon steel.
4. Helium & Argon
When welding aluminum or other similar alloys, a helium-rich gas mix is often the best choice. However, for the best results, you should mix it with some argon. Adding argon ensures you can maintain a spatter-free weld and get deeper penetration. In most instances, this mixture is usually 75% argon and 25% helium.
5. Argon & Hydrogen
When TIG welding and want to get a clean weld, a gas mix with argon and hydrogen is ideal. With this mix, hydrogen ensures no oxidation as oxygen from the air does not get to the weld. You can typically have 1, 3 or 5% hydrogen for these mixtures, with the rest being pure argon.
6. Nitrogen and Hydrogen
Some specialty gas mixes like nitrogen and hydrogen come in handy as a shielding gas when preparing austenitic stains steels for a weld. For these metals, the gas mix also allows for deeper penetration, improves the material’s mechanical properties, and speeds up the job.
Safety Tips for Using Welding Gases
- Always wear protective clothing such as helmets, apron and sleeve corners when using welding gases
- Keep your gas cylinders away from potential tampering, heat and physical damage
- Inspect all your equipment and hoses for leaks and replace worn-out ones
- Store any extra gas or oxygen cylinders separately and always keep them upright
- Close the cylinder valves tight before moving the gas
- Make sure you bleed the lines to remove pressure from the regulators when finished
- Remember always to keep a fire extinguisher close when welding
Conclusion
Welding gases play vital roles when welding anything as they help with everything from shielding and purging the weld to heating the metal. However, with the different types of pure welding gases and mixtures, it is vital to ensure you make the right choice. The kind of metal you will be welding, your welding style, and the weld quality you want should guide you when choosing a gas.
Sources
- What Are Welding Shielding Gases, And Why Are They Important? – TWS-Jacksonville
- Gas Welding Safety – National Ag Safety Database: NASD
- Choosing shielding gases for arc welding – The Fabricator