Welding Exhaust With Gasless Mig. A combination of argon and carbon dioxide is recommended for MIG welding exhaust. Shielding gas isolates the molten metal from gases in the air preventing their interaction.
A MIG welder has a couple of different parts. Cobbler Yamhon Memmeddu and 5 others. The gasless MIG welders are actually self-shielding.
Im not sure the gauge of the header material i use but im sure its around 20 gauge maybe 18 at most.
What i have found is to maintain enough heat in the weld without getting. And most muffler shops dont butt weld they have overlaps on tubing with flanging one end larger than the other slip fits etc. Because the shielding gas escapes through the weld pool some gas can be caught in the weld some of which may may show as bubble deformation in the surface of the weld. Most welders use an external gas cylinder to shield their joints from oxygen in the air.