roll cage

[Speed Raycer]

There's "knowing" how to weld, then there's KNOWING how to weld. I've seen cages that were welded together by people who "know" how to weld with zero penetration. I've also seen cages welded together with a stick welder... apparently with their eyes closed ;)

Anyway, MIG is completely acceptable for use on a 1018/1020 Mild Steel cage. 1018/1020 can also be TIG welded.

4130 is TIG only and should be avoided if it's your first cage. 4130 isn't lighter than Mild Steel.. you're just allowed to use thinner wall sizes, which is where the weight savings come from. With steel prices as crazy as they are right now, 4130 isn't all that much more expensive, but the install time is 3-4 times as long (as mentioned above).

TIG will get you a prettier weld with almost 100% guaranteed penetration, better fitment of the tube to tube joints.

Also, just like Paint and bodywork... the quality of the weld starts at the prep of the joint. No more than 1/16" gaps, shiny metal at least 1" from the cope and wiped down with acetone before you even make a tack weld.

Just my $.02