Choosing the Right Gas for MIG Welding Carbon Steel
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.
Welder most often use the mixture of argon and carbon dioxide gases when 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. If you will use this welding gas mixture, then you need to consider three things 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.
When selecting shielding gas, metal thickness also plays a big role. Common for thinner metals are pure CO2 or a high percentage 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. For thicker metals and globular or spray transfer types, the best choices contain 75 % or more argon, and the rest CO2 and 5% or less oxygen.
Changing the type of gas used will greatly affect weld quality. The best choice for deep penetration is CO2. You need to add argon or use a high percentage of argon gas mixture for a smoother weld. Globular and spray transfers would be easier to set and it works well.
The best all-around welding gas for carbon steel, ultimately 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.
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.