welding stainless steel exhaust
 

working on finishing up 3" stainless steel exhaust. its is tack welded with a mig ( passport plus ) using .035 308 wire and stain mix gas. been practicing on scrap pieces but it seems like i'm going to need to get it tig welded,


so my question has anyone accomplished a good looking weld with mig and if so please share ,settings, process ,pics:D. I will be grinding down weld for esthetics but trying to minimize as much as possible. I'm sure I will need to purge if I decide to tackle this if its possible. .



stain mix has a lot splatter should I be using cO2 or other shielding gas.

http://www.pro-touring.com/showthrea...(-back-purging)

heres a great thread regarding stainless exhaust. I run a separate tank and regulator to purge it. Temps are 29-38 on my Miller 180 SD tig.

Its all in the prep. Get your joints nice and tight. I get lazy sometimes on fitment but I can get by. For me its easier to TIG weld exhaust thank MIG. Slower but easier.

Practice-Practice-Practice

your vid..

I WOULD NOT grind down welds on the SS exhaust.... they'll tend to crack. SS expands and contracts more than mild steel.

The SS exhaust on my roadster has a hairline crack at almost every weld (butt welded) joint.. it was ground down and mirror polished. I will have to re-do the entire system.

Talking with Roy Brizio about this -- he said they no longer use SS for exhaust and if they do they NEVER grind the welds.

Frank --

You don't mention if you're building a SEMA quality show car or a driver hot rod etc... if you're building a show car - I'd ONLY TIG weld. There's no way you're going to MIG it and have it look show quality. But if you're building a PT style driver that you're going to hammer... then MIG would be fine.

It really just makes a difference in what you're building.

Vince thanks for info !
Greg that's one of the reasons I really would like to grind as least as possible while Have it looking good. It's going to be a daily driver / show car/ autocrosser, did not start out that way but that's where it's going now.

I'm hoping to get a descent mig weld but yes tig is the way to go. Worst case I'll see if I can find some one local to finish if.

Hairline cracks that's got to suck!!!

Yes they do! And given the cost of a full custom built - food grade stainless - polished - headers to the tip system... I'm not happy about it!

But I'll just take the whole system off this winter and blast the insides and re-weld it and then polish the welds. It's like everything else on that little POS -- I've had to re do the entire car...

here is what SS exhaust looked like after running it @ RTTC this weekend on Blu Balz... I had to drive the car back from Irvine to LAX to drop off Karl @ the airport then drive to Oxnard.. I was deaf when I got home!

Notice that it did not break @ the welds.. I think my exhaust system is a little to stiff.. need some more rubber exhaust hangers..

http://i1015.photobucket.com/albums/...n/IMG_2747.jpg

http://i1015.photobucket.com/albums/...n/IMG_2746.jpg

Interesting cross-over, tough to factor all the stress points with expansion/contraction and I'll assume torque twist.
Looks like some of the beads could have caused stress-risers?
Some broke behind the bead, material became brittle after welding?

Looks like stress fracture. starts from no where.

Drill a hole in each end, weld it, then lap some new .065" stainless sheet over it.

Just a thought.

Mine is not cracked like that -- mine is tiny HAIRLINE cracks that just follow the part line (weld line) where the tubing was butted. It annoys me only in the fact that this exhaust system was several grand... :unibrow:

They hard mounted the system - and that was their first mistake - and I think it was that initial expansion and contraction with it being hard mounted that set up the hairline cracks... It's since been re hung allowing for some movement.

My system "grows" at least ONE INCH in length... And Tim came up with a masterful redesign of the hanger to accommodate that.

Hmm surprised they didnt do a fusion "root" pass then a cap..

/weld inspection theory.

I guess a root and cap -- on tubing that's .060 or .080 wall ... and then grind it off and mirror polish?

I want to see what your cars look like -- you must have some AWESOME stuff!! :D

My stuff is all junk haha.

My system "grows" at least ONE INCH in length... And Tim came up with a masterful redesign of the hanger to accommodate that.[/QUOTE]

Hard mount cross my mind but I also noticed on my truck that it reall grows quite a bit so I'm going to be running flex line at headers and at tips . its going to be hung real close go body with high temp grommets. Hopefully that will help a bit.
See you @ sema

Im a big fan of those SS flex sections that RS and Marquez Design use. Look to those ring and rod style hangars. Seem to work well for the OEM's.

Stainless shrinks a bunch when you weld it. If you pass multiple welds on the same seam the area will be lower. If you are trying to remove the weld and polish then there will be low areas where you welded. IMHO smoothed out stainless exhaust is for show cars that won't be driven much. It's expensive to build and has poor longevity. Leave the welds on stainless exhaust if you plan on driving it. Be sure to back purge the tubing or use a weld flux to prevent sugaring.

I've started integrating flex couplers whenever possible into my exhaust systems. Just like an OE system... anyway you can eliminate vibrations the better. Vibrant Performance makes serveral sizes and styles.

http://vibrantperformance.com/catalo...Path=1022_1064

a few thoughts for you one of the trucks that I built was done completely in stainless and I will not do that again for the same reason as Greg has stated I tig welded the whole thing and stainless warps badly from the heat way way worse . I tacked the whole system and then starting welding 1 inch random welds at a time it pulled so bad in every direction I had to cut many of the welds apart ad do the over again to make things line up where they were to go though hangers and such. the crossover pipe cracked in no time and that bright shiny look lasted about a week the it turns gold colored. if you bring it to some one to redo it in tig it will pull all over the place and the guy you bring it to will hate you for have to try to make it look good if he has to grind down all the welds. the more it is welded the more brittle it will become. don't weld it solid just tack it with the wire then tig it with a purge to prevent sugaring.tri mix gas is what you should be using for the mig. don't mean to disappoint just trying to help.

Thanks to all for the Info.
My original intentions were to get a good solid weld with mig preferably (because I have no tig) but it seems more like I will need to get it tigged to get what I'm looking for. I'm not going to gring the welds down or polished it.

Now if I could weld it with mig and not get Sugar on the inside. I will gring just a tad ( no where near flush )

I will second this 100%... as the food grade SS exhaust on my Steve Frisbee built '32 Ford... has had to be repaired now for the second time. They (SAR) flushed the welds and polished the entire system... I drive the crap out of my stuff... and the system has/had hairline cracks at every seam. The SS also GROWS a BUNCH... and this has caused other issues.

I will nurse this thru this summer and then the car goes to Brizio for an all new exhaust system. :thumbsup: You know - one that actually works.:D

try triggering the weld just doing one tack after another not doing it solid turn your heat down and purge it with any inert gas it will work just practice a bit more it is possible just not the best way but it does work. good luck with any way you choose.myself would use mild steel and send it out to get it ceramic coated after looks better and stays that way.:D

All said and done I agree. Stainless has too many drawbacks for my application.

I agree... even Brizio said they stopped doing stainless exhaust systems...



If you're going to do SS exhaust -- use 321 stainless from a supplier like Burns Stainless.

I guess I am the odd man out. I like stainless exhaust. If built properly it will last the life of the car, it is easier to maintain than a coated exhaust, and actually does a better job of retaining heat than mild steel.

Like most things Donny -- you've got to use the correct materials for the job.

Most failures on stainless exhaust come from improper mounting of the exhaust. Since the stainless grows then shrinks a ton using multiple expansion couplers, and making sure the rest of the mounts can move on the car is paramount.

I always laugh when I tell a customer that his side exhaust tip is going to stick out up to an 1" from where it is cold, and that it will return. The response is "really I've never seen that before, my buddies doesn't do that." LOL Well then your "buddies" isn't stainless...

Im wondering if the wrong grade stainless was used. It seams that most over-the counter stainless is the 304 grade.

Anybody use the 321, 347 or the specific 409 grade for exhaust.

I was just looking at the stainless grade chart and the 321,347 is a stabilised grade for heavy section welding and high temperatures.

Then I saw that the stainless grade 409 is listed as automotive exhaust grade that is weld stabilised.

I was thinking of building a light weight stainless exhaust similar to an airplane, but now I maybe second quesing that idea based on what Im seeing here.

409 is NOT for nice cars exhaust systems.... as it forms a light layer of rust. That's not the kind of stainless exhaust "we" are looking for.

321 does NOT polish well.... but otherwise works well for our purposes. I'll add that it is better for higher heat applications than normal 304

The food grade stainless in my '32 exhaust is polished to a mirror grade -- but the growth/shrinkage rate is really unacceptable in an exhaust system other
than a "show" car. The food grade tubing works great for bends - since the diameter matches up no matter where you cut it. In other words - you can buy a 90 or 180 and cut it and match it to another cut curved piece and the diameters match up. Nice in a show car exhaust system -- really not very critical in an under car
"used/abused" PT car.

Most failures on stainless exhaust come from improper mounting of the exhaust. Since the stainless grows then shrinks a ton using multiple expansion couplers, and making sure the rest of the mounts can move on the car is paramount.

Very nicely put :thumbsup: I'm making mine all 304 SS ( headers to the tailpipe) don't want corrosion holes down the line among its other benefits.

That is my struggle, giving it room to expand while keeping it tight to the body.

IMO , stay away from the mig , tig only
When I weld stainless, I only use straight argon, tight gap, and purge
Remember stainless expands 4 times more than carbon steel , expansion in the way of long hangers
Good luck:thumbsup: :thumbsup: :thumbsup: :thumbsup:

Got this on mind, 321 SS bellows w interior sleeve ( directional ) these will compress , stretch , handle vibration and heat so they can be used close to or at collector. Like everything else it has its limitations but I'm not sending this thing to the moon:D

A stainless steel single or multiply bellows designed to accommodate pipe growth due to thermal conditions in engine exhaust piping. Series EFB bellows are also constructed to absorb vibration normally associated with engines and generators. Bellows are series 300 stainless steel and can incorporate internal flow liners where necessary. The light weight bellows is highly flexible and will protect the low pressure exhaust piping. End connections can be standard commercial 150# ANSI drilling, beveled weld ends, or special flange styles such as Caterpillar, Cummins, or Detroit Diesel. Exhaust bellows expansion joints are made to order, according to the pipe motion expected, temperature, velocity, vibration, and end connections.

Not to jump on your thread but ....
That's actually a awesome idea, I was thinkin the same thing.
Well actually I was talkin with a union brother and we came up with it together, we use these in the oil and gas industry coming of headers, usually 18+ " in diameter , these expansion bellows.
But your suggestion , who would supply those, you have a contact with 300 series stainless in a 3 " scenario

Yeah I found some 3" 321 SS With sleeve as mentioned. If interested let me get my hands on them and I'll post up results

Just one source...there are many others.


http://www.stainlessworks.net/produc...ex-joints.html

This one had a good selection too:
http://vibrantperformance.com/catalo...php?cPath=1022

flex joints are readily available just about anywhere but the bellows in mind ( picture below ) are just a bit harder to find locally. since they are normally about $100 a pop I want to get to see it before I buy.

I already have the flex joints in there but those well not stretch or compress as much they're more for vibration. these bellows are more durable and suitable for this application.
http://i1232.photobucket.com/albums/...kv11/photo.jpg

some pictures of the progress
http://i1232.photobucket.com/albums/.../photo2-16.jpg
http://i1232.photobucket.com/albums/.../photo4-15.jpghttp://i1232.photobucket.com/albums/...1/photo5-7.jpg
these are the ones I'm looking to replace since they're right at the collector..

What you have will do the job as they also help with expansion and vibration issues....


Read the description on this "flex" joint and they say that the bellows style creates turbulence.... and I'd agree. Whether it's critical for your application is a different issue.


3" versions.

http://www.treadstoneperformance.com...Coupler+Bellow


Vibrant does NOT carry flex bellows in 3"

These guys supply the BELLOWS style with an internal slip joint for smoothness....



http://www.spdexhaust.com/pdfs/AccPDFs/Bellows.pdf