Welding Stainless Exhaust with Flux

[redlig]

I am also a beginner to TIG and intend making a stainless exhaust. I did look into using the paste and found it expensive so bought a larger bottle of Argon instead, I hope to practice to make a reasonable job. How important is the flexy pipe? my engine is inline not transverse.

All engines vibrate. anything that will lessen the effect will help . I've put a suzuki 3 swift engine in my Liege trials car and not only used a flexy but have held the manifold to the pipe using strong springs in tension. As used by the m/c racing world . And others. Also rewelded in a new position the cast manifold using MIG . Its all held for 4 years now with no problems.

 

[Munkul]

I would never build an exhaust without a flexible section. You just end up with bent flanges and horrible exhaust blows.

 

[PSweeney]

If you want to make a technically perfect stainless exhaust, you need to purge and being honest your skill level will be a greater factor in it's strength and integrity than whether you purge it or not. 99% of all stainless production exhausts are MIG welded without purging (some with ER70S wire) and they're not falling apart. Purging is a must for anything upstream of an inlet (and you'd typically use ally further negating the need purging) but in an exhaust IMO it's a waste of gas unless you're building something which will be subjected to severe duty, excessive EGT or just has to look and be 100%. People get hung up on butt welding mandrel bends and pie cutting etc.....

I use dairy bends in 312L, have tried autogenious welding which is fine for tight butt joints, but its no more work to add rod and build up some wall strength around the weld. You want a flex joint between the system and manifold and I'd personally be choosing different silencers, those ebay boxes are a bitch to weld to nicely like that, having a slip fit which you run a lap weld around it so much easier

 

[Popcorn]

Aren't most stainless exhaust usually made from 409 stainless ? I always assumed this was why you can get away with welding them with normal mig.

 

[Munkul]

Aren't most stainless exhaust usually made from 409 stainless ? I always assumed this was why you can get away with welding them with normal mig.

standard fit ones often are, and cheaper aftermarket... higher quality ones are usually made from 304.
Boy racers such as myself would only consider 304 as "proper" stainless as it still looked nice after a few thousand miles. 409 at best goes brown, and at worst, starts pitting and rusting.

 

[bluebenz1]

A bit late to the party with this thread...as an retired coded thin walled stainless steel pipe welder...I can assure there are situations that purging is not practical or possible....I'm welding a complex thin sheet stainless form at the moment, over all about 1.2m long 650mm wide and 100mm deep with lots of angles and bits sticking out... I looked up alternatives to purging and saw SIF purging flus along with Solar flux and wanted to try it but didn't want to fork out 40 quid....so I crushed up some stainless electrode coating to a fine powder mixed it with washing up liquid, coated on the back of a test butt joint and welded....I was amazed at the result....there was a lot of hard to remove slag type deposit but where the weld was exposed it was absolutely clean with no burning or contamination...so have now bought a pot of SIF purging flux.....

 

[Brad93]

A bit late to the party with this thread...as an retired coded thin walled stainless steel pipe welder...I can assure there are situations that purging is not practical or possible....I'm welding a complex thin sheet stainless form at the moment, over all about 1.2m long 650mm wide and 100mm deep with lots of angles and bits sticking out... I looked up alternatives to purging and saw SIF purging flus along with Solar flux and wanted to try it but didn't want to fork out 40 quid....so I crushed up some stainless electrode coating to a fine powder mixed it with washing up liquid, coated on the back of a test butt joint and welded....I was amazed at the result....there was a lot of hard to remove slag type deposit but where the weld was exposed it was absolutely clean with no burning or contamination...so have now bought a pot of SIF purging flux.....

You could have stereo welded it. Or even just made a 6” purge box and moved it along every so often.