welding SS exhaust , poor inside surface cond.

[ttype]

Am welding 3" SS ( 304 ) 1/16 wall tube for an exhaust system .

Tigged one joint , but the inside of weld is a mess. Lots of fluffy blobs.
Tried lowering heat, similar result.

Bought some ss mig wire, but forgot contact tips, so have not tried the mig yet.

Alot of guys are doing there own exhausts. Do they all purge the inside of pipe to get a decent finish ?

The stilagtites I'm getting would seriously effect the exhuast flow !

Any opinions welcome.

[MAC702]

There is also a product called Solarflux, designed to stop the "sugaring" on the inside of the weld. This assumes you can get to the inside of the joint.

Put your location in your profile, and also tell us which machines you have available.

[Anti-GMAW]

It really needs to be backed with ethier a gas, metal, or flux backer to avoid the cabide precipitation that your getting. It's a pain, I know but it's got to be done. Whats it going on?

[ttype]

gas, metal, or flux backer
Would a slice of tin can under the joint keep the O2 away ? Or are there commercial items to do this ?

Have seen metal "T" rings that go under the joint for header fabbing. But they only come in 2" ,max sizes .

Can the solar flux be applied before the joint is attached , without effecting weld ?

Was thinking about micky mousing a cap for each end of pipe, "T" ing a gas line in after the regulator & filling pipe with argon.
Would you have to have a leak at far end on pipe , or will possitive pressure in pipe not effect weld.

Exhaust is for a turbo buick hybred.

Once the exhaust is done will start on Alum intercooler piping.

[boldfabrication]

I just use tape to hold the gas in but you will want a leak or small hole on the other end. On the end with the flanges I use fiberglass tape. I have a y fitting at the moment coming from the flow meter when purging I run it about 20cfm.

[dabar39]

In the last 10 or so years, I've probably welded as many miles of 2" s.s. tubing together in juice plants. We do exactly as boldfabrication has pictured on his post. We have two regulators teed off at the tank just for this purpose, one for the tig and one for the purge line. Dave

[fun4now]

it dosent have to be hi teck. or anything. duct tape masking tape even cardbopard or aluminum foil will do the trick. there are some fancy options available but simple is just fine. gas in one end with a small exit hole at the other to keep air out and not create internal precher. you want it to be able to flow threw pushing out the air.
SS looks bad without the back gasing and is also going to create a bad weld that will likely crack soon if not right at the cooling stage.
good luck, be shore to post up some pic's of the project.