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. There are some gases that are mixed in order to do MIG welding and these gases include carbon dioxide (CO2), argon (Ar), and oxygen (O) which is the least common among them.
Carbon Dioxide or CO2 gas by itself works well and produces the deepest penetrating weld. 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. Read more about Hialeah electrodes here.
The mixture or argon and carbon dioxide gases are the most commonly used in 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. 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.
The role that metal thickness plays in selecting shielding gas is quite a big role. If you are welding thin metal, then you can use pure CO2 or a high percentage of CO2/argon mixture. In welding thin metals, you use a short circuit metal transfer and this is why it is best to use pure CO2 or a high percentage CO2/argon mixture. Use 75 % or more argon, and the rest CO2 and 5% or less oxygen for thicker metals and globular or spray transfer types.
Changing the type of gas at http://discountwelds.com/gasses used will greatly affect weld quality. 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. Globular and spray transfers would be easier to set and it works well.
Ultimately, the best all-around welding gas for carbon steel is C25 or 25% carbon dioxide and 75% argon. This mixture works well from thin to thick steel and the machine can be set 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. You can weld in all positions with this mixture.
These are the guidelines when choose gases for your MIG welding.