roll cage query

[Phred]

hi to all motorsports enthusiats,

I am currently building a rollcage into a Mitsubishi Evo 6 for Grp N FIA level rallying in Africa. I see from some of the posts that TIG is the recomended form of welding. Why is this and what is the reason MIG cannot be used? The cage is manufactured from T45 seamless tube and we have fully profiled the ends. What would be the best filler rod or wire to use as we only have er70s or er100s std availble in this country ( Zimbabwe ), or i will have to import the correct filler

Phred

[Portable Welder]

I'm not familiar with T-45 Tubing I would assume it would fall into the category of the 7018 wire, as for the process I would get a copy of the weld proceedure from your racing organization, I would be ok with mig welding the cage, However Tig welding is a slower process and lets you see exactly what is going on and if you are flowing the metal good.
Try doing some weld testing, weld two pcs of tube together that are 8" long each, then weld one end to the bench, and take a sledge hammer to it, if the tube breaks where you welded them together than I recomend you finding a certified welder.
Good luck

[Teeps]

Heat is controlled more precisely with Tig (depending on the user).

A proper mig weld, will result in a larger HAZ, Heat affected zone, and affect the properties of the metal, possibly making the metal more brittle.

Tig insures proper fusion, and less HAZ, less affect on the metal properties, and stronger joint.

Some racing bodies here in the states require tig only welds, and no grinding allowed.

However I would follow the rules of the league the car will be racing in.