The Right Welding Gases for Welding Carbon Steel
In welding carbon steel, you can use carbon dioxide by itself or you can also use a mixture of gases. MIG (Metal Inert Gas) welding typically uses a mixture of gases including carbon dioxide (CO2), Argon (Ar), and Oxygen (O) which is the least common.
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.
The mixture or argon and carbon dioxide gases are the most commonly used in welding carbon steel. This mixture contains 90% or more Argon, 5% or more carbon dioxide, and 5% or less oxygen. Oxygen is actually an enemy to weld quality, but it is necessary since it helps 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 should go with CO2 or a high percentage of CO2 gas mixture if cost is a big factor.
The role that metal thickness plays in selecting shielding gas is quite a big role. Pure CO2 or a high percentage of CO2/argon gas mixture is used on thinner metals. 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. 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 argon gas mixed for a smoother weld. This works well and makes globular and spray transfer easier to set.
Ultimately, the best all-around welding gas for carbon steel 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. With this mixture, ou can have an arc that can be stiff to soft depending on the voltage setting and wire feed, and the weld for this mixture is smooth. You can weld in all positions with this mixture.
These are the guidelines when choose gases for your MIG welding.