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.  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.


The deepest penetrating weld can be produced using carbon dioxide (CO2) alone.  However, when one welds using CO2 gas, the appearance of the weld is rough, and it produces more smoke than other shielding gases.


The mixture or argon and carbon dioxide gases at 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.  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.  Cost, metal thickness, and weld quality are the three things to consider when choosing this type of welding gas.


There isn't much cost if it is just your hobby to do MIG welding.  However, if cost is a big factor then you should go with CO2 or a high percentage of CO2 gas mixture.


When selecting shielding gas at, metal thickness also plays 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.  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.  This mixture works well and makes globular and spray transfer set easily.


If you use C25 or 25% argon and 25% carbon dioxide, you are using the best all-around welding gas for carbon steel.  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.  This mixture will make it possible for your to weld in all positions.


If you are doing MIG welding as a hobby or as part of your job, then you should be aware of the different types of gases and gas mixtures that can be used for any welding project.

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