MIG wire size question

Chamfer the ends of the box section and give it a try with the wire you are running at the moment................this is going to take a lot longer than with a more powerful set, but may well work out fine if you dont have that many to do.

Alternatively if the MIG doesnt seem suitable, then you can TIG it no problem, and there is really no need for a cooler, although this makes high amp TIG work a lot more comfortable to do.

"Ken" wrote: Chamfer the ends of the box section and give it a try with the wire you are running at the moment (clip) ^^^^^^^^^^^^^^^ However, it IS true that going to a smaller wire will produce a hotter arc, since the current density goes up. So, it should aid penetration. It will take a long time to lay down a bead, but that's the cost of running a small welder.

I see you are still going with the solid steel spars rather than some sort of box section. Not what I would do but then it's your choice.

Using a smaller wire will allow you to get a small but hot bead. You will need it since the solid mass of the spar will suck up all the heat, tends to give you a cold weld on the spar side. Use proper weld prep: clean metal, good fit, 45 degree v, very slight flat at the bottom of the grove, .5mm space at the bottom. Your resulting fillet weld needs to be no more than 5 or 6 mm wide to get full strength so you should be able to do it with 3 passes.

If you want another > I need to weld some 60 x 60 mm 3.5 mm wall thickness box section steel, end

If your TIG is DC why not use stick??? Use a 3mm electrode or larger. Generally when doing structural welding once the material is 25 mm or over preheat is used. ( 100 C ) This is to prevent the material from cooling too fast. I would use E 7018 electrode positive 5/32 diameter and around 130-150 amps. Keep the majority of the puddle on the thick material to prevent melting though. Randy

-- Best Regards, Chris.