C02 or Argon/C02 Mix For MIG Welding?

In the sports world, fans love getting into heated arguments over who’s the best player in the game. It becomes really exciting when they try comparing players from different eras. At the end of it all, neither party ever agrees, except to disagree. The Welding World has their ongoing arguments, too: what gas is the best for MIG welding? CO2 or Mixed Gas. It’s strange that each gas is well able to do the job but inherently different in many ways: from the physical contents of the cylinder to the actual weld.


Both gases use the same flowmeter BUT … they have different connections to the gas cylinder. CO2 tanks require a CGA320 fitting (it’s stamped on the cylinder valve and the regulator connecting nut). The cranky part (i.e. the part that can make you cranky) is the nylon washer that goes between the regulator and cylinder; this nylon washer is easily dropped or misplaced.


Figure 2 CO2 NUT & STEM


The Argon/CO2 mix has a CGA580 fitting on the cylinder valve and the regulator connecting nut.



Your flowmeter will have one of the 2 connections. If the connection isn’t the one you need, then there are 2 routes available. One, replace the existing inlet fitting. A word of warning, some manufacturers have been using a super adhesive for securing the inlet fitting. The adhesive is making it difficult for removing the fitting. So that in the process of removing it, you may end up damaging your regulator.
The easier solution is an adaptor. Another word of caution (and experince), if you’re ordering the fitting over the phone, it’s easy to create misunderstanding. As you can see below, if you get the wrong one, it’ll be useless to you.

Figure 5 Adaptor CO2 Cylinder to Mixed Gas Regulator

Figure 6 Adaptor Mixed Gas Cylinder to CO2 Regulator

Another big difference between the 2 gases is the way you determine how much gas is left in your cylinder. Your flowmeter will answer the question for your Mixed gas but be silent about CO2. The CO2 is stored as a liquid in the cylinder; the only way to know how much remains is by weighing the cylinder.

Figure 7 CO@ Heater

Figure 8 CO2 Regulator with Heater

Figure 9 CO2 Regulator with Fins

Probably the most irksome thing about CO2 and its relationship with regulators is gas flow. Under certain gas flows and temperatures, the CO2 can cause the regulator to freeze up or get bits of solid (snow) in the outlet. When this happens, you have 3 options. One, attach a CO2 heater to your existing regulator. Two, purchase a CO2 regulator with a built in heater. Three, purchase a CO2 flowmeter with fins that slows down the rapid cooling.
We’ve left off mentioning about how the 2 gases affect the actual weld. We’ll cover that another time. If we can help you on your gases, please give us a call or email. We’d be glad to help.




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