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  • Rob Bite

What is the Best Gas for MIG Welding Mild Steel?


Today’s welders must know how to weld a wide range of materials, with steel being one of the most common materials. There are countless types and grades of steel, with mild steel being one of the most prevalent materials used by welders.


For mild steel, MIG welding is the most popular with many welders as it provides a cleaner finish for mild steel welding - but what gas is best used for MIG welding of mild steel? We answer your questions in this blog. Let’s first start with what mild steel actually is.


Firstly, what is mild steel?


Mild steel is a type of low carbon steel that, based on weight, has a carbon composition of between 0.05% to 0.25%. It is known as a low carbon steel, with higher carbon steels typically defined as having carbon content from 0.30% to 2%.


Since mild steel is not an alloy steel, it doesn’t contain a large amount of other elements besides iron. Less carbon means mild steel is typically more ductile, machinable and weldable than high carbon or other steels.


This, however, does mean it’s nearly impossible to harden and strengthen through heating and quenching, and the low carbon content also means it offers less tensile strength than high carbon and stainless steel.


Mild steel is typically used in applications such as:

  • Automobiles

  • Signs

  • Furniture

  • Decorations

  • Wire

  • Fencing

  • Nails

  • As structural steel


Why use MIG welding for mild steel?


Metal inert gas (MIG) welding is an arc welding process in which a continuous solid wire electrode is heated and fed into the weld pool through the use of a welding gun, melting the two base materials together to form a weld. The welding gun also feeds a shielding gas alongside the electrode to protect the weld pool from contamination.


MIG welding is popular with many welders because it provides a cleaner finish for mild steel welding.


What gas should I use when MIG welding mild steel?


To weld mild steel using MIG welding, the process relies on using a shielding gas to protect the weld pool from external contamination - but with so many options of industrial gases on the market, what is the best gas to choose for this type of welding?


There are two main industrial gases used by welders for MIG welding mild steel - 100% carbon dioxide (CO2) or 25-75 mix of CO2 and argon (known as NMAC25T in Simcoe Gase’s lineup of speciality welding gases).


Carbon dioxide is a semi-inert gas which is often used in MIG welding for mild steel fabrication as it provides deeper penetration, however its use also increases spatter and a rougher bead for the finished weld product.


It’s because of this that the 25-75 CO2 and argon mix is the most commonly used industrial gas for mild steel MIG welding. This blend is a great all-purpose shielding gas for mild steel, producing the least amount of spatter and the best bead appearance. It also does not promote burn-through on thinner metals.


Want to learn more about the best industrial gas for MIG welding mild steel? Contact Simcoe Gases today. Our team of industrial gas experts would love to help you find a gas suitable for your unique welding requirements.