In order to have a successful welding job, it is important to know what type of welding gas you need. There are different types of welding gases for various applications and they all serve a particular purpose. If you don’t use the right one for your application, it can cause serious problems with your weld’s quality and strength.
Every sort of gas has its own set of purposes that affects the quality and durability of your weld, as well as how it withstands corrosion. The wrong gas could also leak into the atmosphere without being burned The shielding gases are used to keep the weld region dry and oxygen-free. These atmospheric contaminants can reduce the quality of the weld or make it more difficult, depending on the materials off, producing an ugly torch flame or making a hazardous situation if it ignites from the heat of the arc.
To get the best results from welding, you have to know which type of gas will work for you. There are a few types of gases that could be used in a wide variety of welding processes and knowing what they can do is essential.
In this article, we will discuss the many types of welding gas along with some examples that fall into each category to help you make sense of which one you might want to use for your next project.
Table of Contents
Primary reasons why gas is used in welding
a) Shielding Gases
These are non-combustible, semi-inert gas that is frequently employed in welding operations such as gas metal arc and gas tungsten arc welding.
Arc welding processes differ in how they protect the weld from the atmosphere. Shielded metal arc welding, for example, uses an electrode covered in a flux that produces carbon dioxide when consumed, as well as a semi-inert gas that is an acceptable shielding gas for steel.
b) Purging Gases
Gases such as Helium, Argon are used in gas purging to remove oxygen, water vapor, and any other gases or vapors that might be harmful to a welding joint while it is being welded and immediately after welding.
Stainless steels, duplex steels, titanium-, nickel- and zirconium alloys are susceptible to the presence of air, oxygen, hydrogen, water vapor, and other vapors or gases that might combine with the hot metal as it is being welded. Gases that harm metals and metal alloys may combine with the material to form detrimental compounds that may cause corrosion or contribute to fractures in metals.
The job of a purging gas is roughly the same as that of shielding gas, but it’s done on the underside of the weld.
c) Blanketing Gas
Blanketing gas is necessary for some welding processes to shield the material being welded from atmospheric contaminants. These gases are also used to prevent oxidation by removing oxidizers and other substances that might cause damage to the weld’s quality.
While it isn’t widespread, blanketing is sometimes used to guarantee that a weld does not get stained or tainted after it is completed. To remove any airborne pollutants, gas is filled the area surrounding the weld. This means the filler metal is not tainted by atmospheric contaminants as it is deposited, and there’s no need to use a purge gas.
There are two types of blanketing gases: one that simply prevents oxidation from occurring without removing any atmospheric contaminants, and another that provides a protective atmosphere for nitrogen-containing materials to prevent their reaction with oxygen or other environmental factors such as moisture.
d) Heating Gas
Heating gas is used when molten metals are not heated adequately in order to facilitate the reactions that take place when they cool. By increasing the temperature of welding components, you can speed up processes like diffusion and ensure that reactions happen at an appropriate rate.
This can be especially helpful in multiple-pass welding when the heat-affected zone has to be heated again after each pass. Not only does increasing the temperature of affected materials speed up diffusion reactions and make for a stronger weld, it can also prevent cracking due to thermal stress.
When the gas is providing heating power, there is no need for an arc. In many cases, preheating with gas is a standard welding procedure in which the workpieces are heated before welding begins, preventing cracks and other issues that may be brought on by thermal shock.
The different types of Welding Gases and their use in Welding Fabrication
Pure Gases
The three primary pure gases utilized in shielded arc welding are argon (Ar), helium (He), and carbon dioxide (CO2). The main objective of including additional gases such as oxygen (O2), nitrogen (N2), and hydrogen (H2) is to adjust the arc, the molten weld pool, or the weld.
Argon
Argon (Ar) is a colorless, odorless, tasteless, and non-toxic monoatomic gas that is chemically inert, hence suitable for welding on reactive or refractory metals. Argon gas has a smooth fluid like arc with a wide but penetration. It is a noble gas comprising 0.93 % of the earth’s atmosphere.
Uses
In the casting industry, flushes porosity from molten metals to eliminate flaws in castings.
The industry of metals fabrication – utilized to produce an optimized atmosphere and create a protective inert gas barrier during open arc welding. It is employed in both the primary welding operation and to clear the back of the connection.
Gas Metal Arc Welding (GMAW or MIG) – used to improve the arc characteristics and allow stable metal transfer in Helium by mixing with carbon dioxide (CO2), hydrogen (H2), Helium (He) or Oxygen (O2)
Helium
Helium (He) is a colorless, odorless, tasteless, and non-toxic monoatomic gas that is chemically inert making it suitable for welding on reactive or refractory metals. It makes an excellent choice as a shielding gas because of its heat conductivity and low viscosity. Helium has been used as a shield in the Welding industry since 1915.
Uses
In the casting industry – to eliminate porosity from molten metals.
The industry of metals fabrication – utilized to produce an optimized atmosphere and create a protective inert gas barrier during open arc welding. Like Argon, it may be employed in both the primary welding operation and to clear the back side of a connection.
Carbon Dioxide
Carbon dioxide (CO2) is a colorless, odorless, tasteless, and non-toxic monoatomic gas that is not chemically inert. Carbon dioxide has an increased heat conductivity in comparison to argon, this makes it effective in plasma cutting where the goal is to manage heat input into the workpiece.
Uses
Due to its high heat conductivity; used for welding light metals or stainless steel sheet metal because this type of material does not need to be preheated before welding due to carbon dioxide’s ability to remove all oxides from the surface quickly.
For mild steel applications using CO2 provides better fuel efficiency than argon, but it requires equipment for proper shielding during welding.
Acetylene
Acetylene (C2H2) is a colorless, highly flammable gas mostly used for oxy-fuel cutting and welding of steel. The flame it produces is hotter than that produced by commercial propane or MAPP gas.
Uses
Industry of metals fabrication – used for welding steels and low alloy steels, especially where preheat is required; acetylene is more suitable for use with cast steel because of the high level of carbon in this type of metal.
Oxyacetylene welding (cutting) – it can be used to repair plate metal (structural beams) and sheet metal (hulls). It may also be used to cut light gauge plate materials, especially when there are burn-through problems on dissimilar materials such as steel and aluminum sheet metal.
Propane
Propane (C3H8) is a colorless, flammable, liquefied gas with a distinct or natural gas odor. Is a type of petroleum gas used for oxy-fuel welding. Considered an alternative to acetylene for cutting, brazing, and heat treating applications and burns at lower temperatures than acetylene.
Uses
It’s a great way to cut through steel that isn’t as important, such as carbon steel in scrap yards.
It’s also a cost-effective source of fuel gas.
Propylene
Propylene (C3H6) is colorless, flammable gaseous liquefied gas with a faintly sweet odor. A type of petroleum gas used for oxy-fuel welding and cutting.
Uses
It provides greater peak security because it may be used up to full tank pressure.
It’s great for cold uses since it has a greater vapor pressure than propane, which combines the characteristics of an acetylene flame with the additional secondary heating capacity of propane. Therefore, the fuel gas burns hotter than propane. However, evaluate the cutting speed in each scenario before using it as fuel gas.
Oxygen
Oxygen (O2) is a colorless, odorless gaseous element that makes up 20.99% of the earth’s atmospheric gases. It’s vital for life and is commonly used in gas welding to achieve an oxidizing atmosphere for ignition during welding operations.
Uses
Oxygen promotes combustion, which magnifies the heat generated by fuel for gas welding and oxy-cutting metals.
It also has wetting and spray benefits when you combine oxygen with carbon dioxide and argon.
When used in shielding gases, it provides fluidity to the molten pool and speed to the welding operation.
It’s a gas that is used as the plasma cutting fuel (with Hafnium electrodes) on carbon steel.
It generates the hottest flame that can weld steel when combined with acetylene.
Because of the shielding effect, many metals can be welded with oxygen without the need for a shielding flux filler wire.
Hydrogen
Hydrogen (H2) is a colorless, nonmetallic, highly flammable diatomic gas with the molecular formula H2. It’s used as an arc-welding fuel and to increase the heat input for various welding operations such as plasma cutting steel.
Uses
Hydrogen promotes clean, highly atomized arcs when used with argon.
It is an effective cutting gas that forms a clean, sharp cut on carbon steel.
When combined with argon, it provides greater penetration and allows you to cut thicker materials.
It also helps reduce the spatter that forms on the edges of the plates during cutting operations.
Nitrogen
Nitrogen (N2) is colorless, odorless, nonreactive diatomic gas. It is colorless, odorless, tasteless, non-toxic, and non-flammable gas, which exists at atmospheric temperatures and pressures.
Uses
Small modifications to argon-based shielding gases can be used for welding stainless steel using the Gas Metal Arc Welding (GMAW or MIG) technique.
It’s used as a purge gas with stainless steel tube welding.
Nitrogen can improve plasma cutting and heat-treating.
This compound is often used alone as a shielding gas for laser welding and plasma cutting.
When shielding nitrogen-rich alloys, it improves the metal’s mechanical properties and can help with penetration while maintaining the arc.
It’s also utilized as a blanket gas after welding is completed in tanks and enclosed areas, keeping the material intact until it’s employed with its intended product.
Nitric oxide
Nitric oxide (NO) is a colorless gas with the molecular formula NO. It’s commonly used in oxy-fuel cutting applications when you have to cut through high alloy metals, such as stainless steel.
Uses
Nitric oxide is used as a plasma-cutting gas due to its whiter flame and the ability to achieve greater speeds than nitrogen.
When performing stainless steel cutting, it provides better bead formation and less smoke than oxyacetylene flame.
It’s also helpful for reducing the number of contaminants that can cause corrosion by removing them from the surface of stainless-steel tubes.
This compound produces an inert atmosphere when combined with argon, which benefits many welding processes such as those involving titanium or aluminum alloys.
The different types of Mixed Gases used in Welding
The most frequently used gas mixtures for improving performance are as follows:
Argon & CO2
Carbon, Low-Alloy, and some Stainless-Steel alloys can be welded using these mixtures.
- CO2 in low levels can be used in a pulsed arc or spray arc operation, while higher concentrations (more than 20%) are best utilized for short arc welding and the protection of some flux-cored wires.
- Increasing the CO2 level will improve weld penetration and wetting of the bead.
Argon, CO2, & Oxygen
This mixture is primarily used when welding dissimilar metals such as stainless steel and carbon steel.
- It’s also utilized to anneal the weld metal in preparation for grinding and finishing operations.
Argon, Helium, CO2
This tri-mix combination is ideal for short-circuiting transfer welding of stainless steel in all welding positions.
- Reduce carbon dioxide content to minimize carbon absorption and improve corrosion resistance, especially in multiphase welds.
- The exceptionally high helium content allows for a significant amount of heat to be supplied, which is essential for the stainless-steel weld pool’s mending.
- The combination of argon and carbon dioxide provides excellent arc stability and depth of fusion.
Helium & Argon
Useful in a wide range of Gas Tungsten Arc Welding (GTAW or TIG) applications, such as when greater heat input to the base material is required while maintaining good arc starting and stability.
- Useful for thick aluminum components and other nonferrous materials that require increased heat input to the base material for improved welding performance.
- It is used to weld light gauge steel, stainless steel, and aluminum in such applications as bicycle frames, food service equipment, and recreational boats.
Argon & Oxygen (O2)
It is used to weld ferritic and austenitic stainless-steel parts with a spray arc technique.
- Suitable for welding big sections of Carbon Steel, such as farm equipment, military vehicles, ships, and automobile components.
- Mostly utilized for spray transfer on clean, bare Carbon and Stainless Steel.
Argon & Hydrogen
It is the preferred gas mixture for welding heat-resistant superalloys.
- Helps maintain arc stability during spray transfer operations on clean, bare Carbon and Stainless Steel.
- Hydrogen temperature can be adjusted to weld high alloy steels with excellent mechanical properties.
Nitrogen & Hydrogen
It is a high-performance nonoxidizing gas mixture for welding heat-resistant superalloys.
- Nitrogen does not react with Carbon or low alloy steels, allowing it to uncover porosity and aid in penetration without causing embrittlement.
- Useful when welding Titanium, Inconel, Monel, Alloy 20Cb3 stainless steel, and fine grain steel.
Benefits of Various Welding Gases
We’ve discussed a few of the most frequent gas mixes in welding, but what sets one combination apart from another? Let’s take a look at the advantages of each sort of gas to better understand this.
Oxygen
Take note of how you use oxygen. In the correct situations, it may improve flow, penetration, and welding arc stability. It does oxidize the metals you’re working with, however, so employ oxygen cautiously.
Helium
You can also weld thicker materials together using helium. Helium makes for a more powerful arc, allowing you to weld faster and more efficiently.
Hydrogen
Welding with hydrogen does not require the use of flux. This gas also allows you to weld at higher temperatures, which can help you finish your project faster.
Argon
The least reactive of the noble gases is argon, which inhibits weld spatter and promotes a flatter bead profile when combined with carbon dioxide.
Nitrogen
Like argon, is widely accessible and inexpensive to purchase. It’s nonreactive and lighter than argon.
Carbon dioxide
When welding thick materials together, use this gas.
Frequently asked questions:
When does welding gas expire?
Gas is only useful before a certain date. If it’s expired, the gas will not mix properly and you may be at risk for injury.
What is the most common gas used in welding?
This depends on the material you’re working with. For example, if your project requires stainless steel, argon and carbon dioxide is the best combination for your needs.
Which gas is best for MIG welding?
The best mix is argon with either carbon dioxide or helium.
Conclusion
In conclusion, there are a variety of gases used in welding. The correct gas will depend on your project’s needs. Be sure to keep your gas fresh and take safety precautions when using argon, hydrogen, helium, oxygen, nitrogen, carbon dioxide, and other substances.