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. 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.
Welder most often use the mixture of argon and carbon dioxide gases when welding carbon steel. 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.
The cost is not a big deal if you are just MIG welding as a hobby. 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. With this mixture, you can weld 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.