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 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. 90% or more argon, 5% or more carbon dioxide, and 5% or less oxygen are the components of the gas mixture for welding. 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. There are three things to consider when choosing this type of welding gas, namely, cost, metal thickness, and weld quality.
There isn’t much cost if it is just your hobby to do MIG welding. 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. Common for thinner metals are pure CO2 or a high percentage CO2/argon mixture. The reason for this is that on thin metals you typically weld using a short circuit metal transfer. 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 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. 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. The weld for this mixture is smooth, and depending on the voltage settings and wire feed speed, the arc can be stiff to soft. You can weld in all positions with this mixture.
Although carbon dioxide can be purely used for welding carbon steel, sometimes it is best to use a mixture of argon and carbon dioxide to get a good results on your welding project.