at least 150 amps, you will need a bigger electrode though, 2.4 or even 3.2, the problem is getting enough heat into the 10mm, without melting the 2.5mm, really you should stick weld it. If you try to tig it remove the millscale off the joint before you start, Is it a bench?, you could tig up the frame and bolt the top on.
Hi,
What settings/electrode etc do you reccomend for the box section?
Cheers,
Paul.