advice onmaking welds look good on exhaust joins

[stfezzy]

ive decided to make my own exhaust or atleast start bymaking a down pipe with stainless steel and buy pre bent bends!! When welding up the section togeather whats the best way to get a good looking weld with good penetration??? And so its still smooth inside the pipe??
Is it ok butt welding the sections togeather???

any help would be appreciated thanks

[dewismotorsport]

Tbh on stainless it's best to TIG weld it and back purge it so that you not get a nice smooth weld inside as well

If your using mig then just do trigger welding which is just a hot tack laid half over each other will look neet if done properly but you will always have the too back purge it to prevent unsmooth welds inside

[stfezzy]

How do you back purge it mate isthere a way!?

[jamied]

Back purge is when you fill the inside of the tube you are welding with the gas you are welding with at the same time (CO2/Argon) i use a second cylinder of gas which has a small valve on the end of the tube which has a bung or plate, this feeds gas into the tube you are welding.
Some people bung both ends of the pipes, some don't. i normally bung both ends but have a small pressure relief hole in the end bung.

[jamied]

I have made a table up that has the purge unit built in so i can clamp the manifold down to it and then weld the pipes, this stops heat distortion at the same time.

[Frisco]

Use masking tape to block both ends of the pipe (you have to block both ends or the gas wont fill the pipe properly) and just poke holes in the end for the vent (this is to let the air out so it has to be done). If you have the pipe tacked up then its a good idea to tape the unwelded joints as you go along to save gas

[king nero]

Back-purging; it's really a must-have for stainless. Both for corrosion resistance as for a clean weld.

If you don't make vent holes, pressure will build up and when finishing the weld it'll give you trouble as it tries to escape through your puddle.

[corsa-x14xe]

I have made a table up that has the purge unit built in so i can clamp the manifold down to it and then weld the pipes, this stops heat distortion at the same time.

tbh it looks a bit like a bomb lol

[Tathan]

Can't you just grind it

[stfezzy]

What weld and then grind it smooth!? Ill have grinder marks over it then

[dewismotorsport]

What weld and then grind it smooth!? Ill have grinder marks over it then

You can get the sanding discs with various grades if done properly can be very effective

[stfezzy]

Like a roloc disc mate? Thx what sort of setting should i be using the welder on ? Low current and wire speed? ?

[beeson1987]

when doing this in the past, i didnt bother "back purging" or any thing like that, if youve got a mig just set it slightly higher on the heat than the wire feed, i weld exhausts all the time and can get really neat welds with mig, only thing is the weld will eventually rust, unless using stainless wire.