Different Types of Welding Gases and Their Use in Welding Fabrication

Categories of Gas Uses in Welding

Purging gases – used to cover the underside of the material you’re welding. It is applied mostly on stainless steel items.

Heating gas – certain types of welding require preheating of the metal before the actual welding. This gas comprises a fuel mixed with air or oxygen, which is lit by a flame to heat the metal.

Blanketing gas – this is a process of filling tanks and confined spaces with gas after completion to keep air and other foreign material from contaminating the finished product.

Types of Welding Gases and Their Use in Welding Fabrication

1. 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

• Casting industry – used to flush porosity from molten metals to eliminate defects in castings.
• Metal fabrication industry – used to create an optimized atmosphere during open arc welding and create an inert gas shield during welding. It is used in both the primary welding stage and to purge the backside of the joint
• Gas Metal Arc Welding (GMAW or MIG) – used to enhance the arc characteristics and facilitate stable metal transfer in Helium by blending it with carbon dioxide (CO2), hydrogen (H2), Helium (He) or Oxygen (O2)

2. Helium

Helium (He) is a colorless, odorless, tasteless, non-toxic, and monatomic gas that is inert and commonly used for GTAW on nonferrous materials. Helium is non-flammable and has high thermal conductivity and ionization potential

Uses

• Helium produces a very hot weld with good weld productivity and mild penetration with a fluid arc.
• To create an inert gas shield and prevent oxidation during welding of metals such as aluminum, stainless steel, copper, and magnesium alloys.
• Increases weld pool fluidity and travel speed.
• Addition of Helium to the shielding gas mixture enhances deeper penetration, faster travel speeds and brings a higher heat input to welds
• Reduces the formation of welding ozone when welding on aluminum alloys.
• As a shielding gas, in both its pure form and as a mixed solution with other gases in MIG and TIG welding
• It creates the right mix when used with argon. The argon excels in consistent arc starts, and the Helium adds the extra heat needed for specific applications like welding aluminum, and TIG welding in particular.

3. Carbon Dioxide

Carbon dioxide (CO2) is a tasteless, colorless, odorless, non-flammable gas usually used for GMAW short-circuit transfer and FCAW.

Uses

• In its pure form, it is used in flux core welding, some carbon steel MIG welding, and plasma shielding.
• When mixed with argon, it can be used as a shielding gas during the welding of carbon and stainless steel. Sometimes it is used in its pure form, therefore helping to prevent atmospheric contamination of molten weld metal during gas shielded electric arc welding process.
• Produces a deep narrow penetration with a stiff harsh arc that works well in out of position welding.
• Adding Carbon Dioxide to Argon or Helium deepens penetration and stiffens the arc improving out of position welding.
• Combining carbon dioxide with oxygen gives a comprehensive penetration profile at the surface of the weld, while the low ionization potential and thermal conductivity create a hot area at the center of the arc column resulting in a well-balanced width-to-depth penetration of the weld.

4. Acetylene

Acetylene (C2H2) is a colorless, highly flammable gas mostly used for oxy-fuel cutting and brazing applications.

Uses

• Has the hottest flame temperature of up to 6,300 °F/3,480 °C, therefore, an excellent choice for welding, brazing, and cutting of steel alloys.
• 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.

5. Propane

Propane (C3H8) is a colorless, flammable, liquefied gas with a distinct or natural gas odor. The flame temperature of the oxy-propane flame is lower and releases lower BTU compared to propylene and acetylene.

Uses

• It is commonly used by scrap yards for cutting of carbon steel where the cut quality is less critical.
• It can also be used as cost-effective fuel gas.

6. Propylene

Propylene (C3H6) is a colorless, flammable, liquefied gas with a faintly sweet odor. It has moderate BTU capacity in its primary flames and high BTU capacity in its secondary flames.

Uses

• It offers more excellent safety as it can be utilized up to full tank pressure.
• With a more significant vapor pressure compared to propane, it is well suited for use at cold temperatures as
• Combines the qualities of an acetylene flame with the secondary heating capacity of propane; therefore, the fuel gas burns hotter than propane. However, before choosing it as a fuel gas, compare the cutting speed based on individual cases.

7. Oxygen

Oxygen (O2) is a colorless, odorless, and tasteless gas comprising 21% of the earth’s atmosphere.

Uses

• Oxygen supports combustion, which amplifies heat with fuel for gas welding and oxy-cutting metals oxy-fuel cutting operations.
• When you mix oxygen with carbon dioxide and argon, it provides wetting and spray advantages
• It is beneficial if added in small quantities to shielding gases benefits as it adds fluidity to the molten pool and speed to the welding process.
• It is used as the plasma cutting gas (with Hafnium electrodes) on carbon steel.
• 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.

8. Hydrogen

Hydrogen (H2) is the lightest of all gases. It is colorless, odorless, tasteless, non-toxic and exists as a gas at atmospheric temperatures and pressures

Uses

• Mainly used with austenitic stainless steels to promote oxide removal and increase heat input. Hydrogen may be used in higher percentages of 30 – 40% in plasma cutting operations on stainless steel to increase capacity and reduce slag.
• In metal fabrication, hydrogen serves as a protective atmosphere in high-temperature operations such as stainless steel manufacturing
• Commonly mixed with argon for welding austenitic stainless.
• Used in atomic hydrogen welding which is a specialized process used to weld materials with extremely high melting points, like tungsten

9. Nitrogen

Nitrogen (N2) is a diatomic gas comprising 78% of the earth’s atmosphere. It is colorless, odorless, tasteless, non-toxic, and non-flammable gas, which exists at atmospheric temperatures and pressures.

Uses

• Mainly used for the promotion of austenite and to improve corrosion resistance in duplex and super duplex steels.
• Small additions to argon based shielding gases can be used for welding stainless steel by the Gas Metal Arc Welding (GMAW or MIG) process.
• It is utilized as a purge gas with stainless steel tube welding.
• Nitrogen can enhance plasma cutting and heat-treating.
• Used by itself as a shielding gas for laser welding and plasma cutting
• When shielding nitrogen-rich metals, it increases the alloy’s mechanical properties and can deepen penetration while stabilizing the arc.
• It is used as a blanketing gas once welding is finished inside tanks and enclosed spaces, to preserve the material until it is used with its intended product.

10. Nitric oxide

Nitric Oxide When added, it serves to reduce the production of ozone and also stabilize the arc when welding aluminium and high-alloyed stainless steel