What Gas Should Mig Welders Use? Techniques for Achieving Beautiful Welds

The quality of Mig welds depends not only on choosing the right welding machine and mastering welding techniques but also on a crucial factor: selecting the appropriate shielding gas. Join RX Tradex to explore what gas Mig welders should use and how the choice of shielding gas directly impacts weld quality.

1. What is Shielding Gas in Welding?

During welding, an electric arc is generated. Shielding gas protects this arc from exposure to other gasses that can cause spattering of electric sparks. Additionally, shielding gas aids in creating deeper, stronger, and aesthetically pleasing welds.

Role of Shielding Gas in Mig Welding:

• Preventing Oxidation: Shielding gas forms an inert gas layer around the weld pool, preventing oxygen from the air from penetrating the molten metal. Oxidation of the metal reduces its mechanical strength, introduces impurities, and makes the weld brittle and prone to cracking.
• Stabilizing the Weld Pool: Shielding gas stabilizes the weld pool, ensuring a consistent and concentrated heat source. This stability facilitates easier welding and results in neater weld beads.
• Improving Metal Penetration: Shielding gas also enhances the penetration capability of the welding metal, enabling deeper fusion and stronger bonds.

2. What Gas is Used in MIG Welding?

Typically, MIG welding primarily uses CO2 or Argon gas, depending on the type of material being welded such as iron, steel, stainless steel, or aluminum. The choice of shielding gas ensures efficient operation and weld quality. Specifically:

• Inert gasses such as He and Ar: Pure Argon (Ar) is used as a shielding gas for welding non-ferrous metals or white steel. Meanwhile, pure Helium (He) is used for metals that expand when exposed to high temperatures, such as Cu, Mg, and AL.
• Mixed gasses: Mixed gasses like Ar + O2 + CO2, CO2, and Ar + CO2 combine different shielding gasses. Mixed gasses are suitable for low carbon steel welding, offering optimal weld quality. However, they are less common due to higher costs.
• Active gas (CO2): CO2 gas is commonly used for welding medium carbon steel, providing stable welds with deep penetration and high welding speed. However, CO2 may cause spattering when welding thin metals.

3. Why is CO2 Gas Widely Used in MIG Welding?

While Argon and mixed gasses yield aesthetically pleasing welds, Argon is expensive and less common. It is primarily used for special materials like aluminum, nickel, copper, titanium, and heavy industrial applications such as machinery manufacturing and shipbuilding. Therefore, CO2 gas is widely preferred for welding common metals like stainless steel and iron due to:

• Lower cost compared to Argon and mixed gasses.
• Easy availability and production, resulting in lower costs.
• High welding productivity, 2.5 times more efficient than manual arc welding.
• Producing high-quality welds with minimal deformation due to high welding speed and concentrated heat source.

4. Consequences of Incorrect Shielding Gas Usage in MIG Welding

Using the wrong shielding gas in MIG welding can result in porous, insufficiently fused, and aesthetically unappealing welds. Shielding gas plays a critical role in protecting the weld, preventing oxidation from infiltrating the weld area, and ensuring a clean and attractive weld appearance. Therefore, choosing the correct shielding gas for MIG welding is highly important.

Effects of Using the Wrong Shielding Gas in MIG Welding:

• Porous Welds: Inappropriate shielding gas allows oxygen to penetrate the weld pool, leading to the formation of pores on the weld surface. These pores decrease mechanical strength, load-bearing capacity, and aesthetic quality of the weld.
• Insufficient Fusion: Incorrect shielding gas can hinder the metal’s ability to fuse properly, resulting in incomplete penetration. Insufficient fusion leads to welds with very low strength, prone to cracking under stress.
• Loss of Aesthetic Appeal: The use of incorrect shielding gas can cause issues such as rough, uneven welds, discoloration, and overall reduced aesthetic quality of the weld.

Conclusion

Understanding the appropriate shielding gas directly impacts weld quality and product performance. Using the correct shielding gas is essential for producing high-quality MIG welds that meet technical and aesthetic standards. Join us this August in Hanoi at the Vietnam Manufacturing Expo 2024 organized by RX Tradex to experience and learn firsthand about the latest MIG welding techniques to enhance production quality.