The gases that can be used when welding carbon steel is a mixture of certain gases or you can also use carbon dioxide by itself. 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 disadvantage of using CO2 gas for welding is that the weld will have a rough appearance, and will produce a lot of smoke compared to the other shielding gases.
Argon and Hialeah Co2 gas mixtures are most commonly used. This mixture contains 90% or more Argon, 5% or more carbon dioxide, and 5% or less oxygen. The quality of the weld is somehow affected adversely by oxygen, yet it is important because it help produce a hotter, smoother arc when added in small amounts. If you will use this welding gas mixture, then you need to consider three things namely cost, metal thickness, and weld quality.
If you are just doing MIG welding as a hobby, then cost is not really a big deal. You only go for pure CO2 gas or a high percentage of CO2 gas mixture if cost is a big factor to you.
Metal thickness plays a big role when choosing shielding gas. Common for thinner metals are pure CO2 or a high percentage 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.
Changing the type of gas used will greatly affect weld quality. CO2 is the best choice for deep penetration. If you want a smooth weld, the you need to add argon to the mixture, or use a mixture with high percentage of Hialeah argon gas mixed for a smoother weld. This works well and makes globular and spray transfer easier to set.
If you use C25 or 25% argon and 25% carbon dioxide, you are using the best all-around welding gas for carbon steel. With this mixture, you can weld thin to thick steel and the machine can be set to produce any transfer type. The weld for this mixture is smooth, and depending on the voltage settings and wire feed speed, the arc can be stiff to soft. With this mixture, you can weld in all positions.
If you are doing MIG welding as a hobby or as part of your job, then you should be aware of the different types of gases and gas mixtures that can be used for any welding project.