Guide to Welding Carbon Steel
In welding carbon steel, you can use carbon dioxide by itself or you can also use a mixture of gases. The mixture of gases used in MIG (Metal Inert Gas) welding include carbon dioxide (CO2), argon (Ar), and Oxygen (O), although oxygen is the least common of the gases.
You can use carbon dioxide (CO2) gas by itself and the kind of weld that it produces are deep and penetrating. The reason why carbon dioxide is not really the best option although it produces deep weld is that the final result appears rough, and during welding there is a lot of smoke produced compared to using the other shielding cases.
Welder most often use the mixture of argon and carbon dioxide gases when welding carbon steel. The contents of this mixture is 90% or more argon, 5% or more carbon dioxide, and 5% or less oxygen. When oxygen is added in small amount while welding, it produces a hotter, smoother arc which makes oxygen necessary for welding even though it adversely affects the quality of the weld. Cost, metal thickness, and weld quality are the three things to consider when choosing this type of welding gas.
There isn’t much cost if it is just your hobby to do MIG welding. You should go with CO2 or a high percentage of CO2 gas mixture if cost is a big factor.
Metal thickness plays a big role when choosing shielding gas. If you are welding thin metal, then you can use pure CO2 or a high percentage of CO2/argon mixture. It is best to use pure CO2 or a high percentage CO2/argon mixture on thin metals because you typically weld it using a short circuit metal transfer. If you are welding thicker metals and globular or spray transfer, then it is best to use a mixture of 75% or more argon, the rest CO2 and 5% or less oxygen.
The quality of the weld is affected if your change the gas type. For deep penetration, use CO2. If you want a smooth weld, the you need to add argon to the mixture, or use a mixture with high percentage of argon gas mixed for a smoother weld. This works well and makes globular and spray transfer easier to set.
The best all-around welding gas for carbon steel, ultimately is C25 or 25 % carbon dioxide and 75% argon. Thin and thick steel can be welded with this mixture and you can set your machine to produce any transfer type. It has a smooth weld, and the arc can be stiff to soft depending on the voltage settings and wire feed speed. This mixture will make it possible for your to weld in all positions.
These are the guidelines when choose gases for your MIG welding.