Welding to an exhaust clamp

[Kayos]

The majority of my welding has been on car body work, I never did the start on thick stuff, straight into the thin

I now need to weld an exhaust up, so I've got an 8mm thick flange and 1.5mm ish thick tube, all brand new

Any special techniques? And do I set the amps for the flange or the tube?

It's all brand new and mild steel, my Mig is 150 amp max, 0.6 wire and correct gas

 

[Bill Edwards]

You'll need it cranked right up for welding the thick metal (otherwise you will get a cold weld with no penetration, 8mm is a bit much for 150 amps really) and to aim the weld onto the thick and just sort of wash over to the thin, then back to the thick - just sort of melting onto the edge of the thin but not concentrating all the heat on it or it'll be blown apart.

 

[Shedendman]

Start on the thick stuff and whip it onto the thin,do short bursts so you dont build up to much heat for the thin stuff.
Amps wise is down to your machine,if you can practice on some scrap bits,you doing this overhead or on the bench?

 

[Chris Stevens]

The best way to do that and get a good result with 150amps, is to vee out the 8mm part to maybe 3mm, tack parts together, check for fit, then weld fully. Better still would be to tack and get someone with a more powerful set to weld it for you, probably only want a drink for doing it, and might mean avoiding a lot of hassle if your weld failed at at any time in the future?

 

[eSCHEn]

Shame you're a bit far mate. You're welcome to use the TIG here as they're great at sticking thick to thin. Do you have access to one?

 

[Richard.]

The best way to do that and get a good result with 150amps, is to vee out the 8mm part to maybe 3mm, tack parts together, check for fit, then weld fully. Better still would be to tack and get someone with a more powerful set to weld it for you, probably only want a drink for doing it, and might mean avoiding a lot of hassle if your weld failed at at any time in the future?

The way I picture it the exhaust tube will be sitting flush on the flange so I don't think V prep on the thick flange is doable. A tig would be the nicest approach but if you don't have or can't use one then mig it is. 150 amps is a little light but it only needs to be an air tight seal and I can't see it been under enough pressure to come off. Adopt the thick to thin tech as bill said. Set it as hot as it goes and weld directly onto the flange while allowing the pool edges to wet onto the thin tube. This is the same approach id adopt with a tig. Good luck.

 

[Chris Stevens]

Only need to vee the 8mm flange on outside of the hole where pipe fits, then tack and fully weld. Thick to thin on something like an exhaust has to be reasonably good weld to prevent cracking due to vibration.

 

[Kayos]

Thanks for all the tips

Sadly no access to a Tig, however it's just a quick fix to get someone through Christmas, I've double checked and the flange is actually 6mm thick, I'm guessing that won't make a huge difference on my 150 amp set?

 

[Chris Stevens]

You just need to get a grindstone of some sort, and vee the holes on your flange, then you will be able to weld no problem.

 

[pondy]

I welded up a section of exhaust on my mums shogun when the cat was stolen, had my portamig 185, using about 3/4 of its total power output and it's been fine for the last year, the flanges were 8mm withthe pipe being about 1.5mm? (What ever standard exhaust thickness is) I just kept my travel speed slow to put heat into the flange and quickly whipped to the pipe. I don't think it needs to be mega strong, just gas tight and with enough penetration so it won't crack with vibrations etc. Have fitted alot of non gen exhausts and the welding on some of these is poor with cold, tall beads. but with customers coming back year after year for service work I get to see them still and they hold up ok. It would be an idea to bolt of clamp the flange down when welding as I didn't and got slight warpage