This TECH TIP provided by the experts at ESAB.
Choosing the right shielding gas is key for weld quality and efficiency, as well as keeping costs low.
For the vast majority of applications, the choice is relatively simple: either straight CO2 or a 75/25 blend of Argon and CO2 (C25) for flux core wires based on classification; however for GMAW there are many options. Here’s a look at the pros and cons of both, so you can decide.
Straight CO2 means a less stable and greater fume and spatter-generating arc. The upside? This option provides the best penetration profile. It’s also cheaper than C25 and gives you good cleaning action, so it’s ideal for home hobbyists or light industrial applications. Even in heavy industrial applications, if you’re dealing with rust and mill scale, 100% CO2 delivers.
Argon and CO2
C25, on the other hand, will get you a less fume-generating, more stable arc, with less spatter and improved cold weather impact toughness. However, you won’t get the broad penetrating arc the same way straight CO2 does. So, if you’re welding fillets, for instance, and you want to make sure you get good penetration at the root of the joint, you can opt for straight CO2 instead or pay close attention to where the welding arc is focused in the joint.
For gas metal arc welding (GMAW) carbon steel, utilizing solid and metal cored wires (excluding aluminum and stainless steel), you can opt for choices such as C25, 90/10 blend of Ar/CO2 or others which may include blends with oxygen as well. The C25 gives you good penetration and short-circuiting transfer for welding on sheet metal if you don’t have pulsing capabilities. If, however, you want to go into spray transfer and achieve a cleaner weld profile, all with minimal spatter, then blends with greater than 80% argon are recommended.