The technical term of CO2MAG should be "CO2 MIG welding", and the full name of CO2MAG welding machine you mentioned is the welding machine specially used for this kind of welding. It can be written as a carbon dioxide MAG welder, or it can be written directly in your original text. Everyone in the welding industry knows that. Of course, I have been engaged in technical translation for decades and know a little.
For the definition of MAG welding, please refer to Baidu's:/view/view1499897.htm, which will give you more explanations about MAG welding technical terms.