Technical Did Muffler Shop Weld my 304 Stainless System with Steel Wire?

A highly recommended shop did at really crappy job on a full 304 stainless system.

They didn't route pipes over crossmembers (are hanging low looks like crap when viewing from the side), the welds look like bird shit, and worst of all, they appear to be strongly magnetic, just like steel.

I know even with 308 or 309 wire, welds can vary from non-magnetic to mildly magnetic. I believe 310 is what you use if you need a non-magnetic weld (some applications required non-mag welds.) The reason for the magnetic welds is the type of iron in the wire, if it is austenite like in 310, it won't be magnetic. NOTE: Again, not sure about what I just said, info is sketchy on net - no real in depth discussion for dummies like me.

Anyone have any positive way to determine if they used ordinary mild steel rod for the welds?

NOTE: I know there is a "passivation" method using nitric acid that is supposed to restore the ability for the chrome oxide to form over welds that got too hot - or "something like that." Haven't found a good explanation, but maybe might be useful to identify steel wire???

 

You might ask the shop what type of wire they used.

 

Spark test.

 

I only want to bring that up only if I know they used the wrong wire. I have to get them to bend up some more pipe to route properly and don't want to "pile on" with complaints.

SPARK TEST: I totally forgot about that. I will try but I'm concerned I'll be grinding welds with a die grinder stone and it may not be that obvious. Fortunately I have a scrap piece of welded tube that split and may be able to get it on the bench grinder.

 

If it is steel wire, it will rust. So maybe wrap a wet towel around the weld?

Also, I doubt a muffler shop would have 304 wire, not the type of work they normally do, plus the cost of the wire and different shielding gas.

 

They already screwed up once.. Do you think they will get it right the second time? 99%of exhaust shops use standard solid mig wire. Some shops use flux core wire with shielding gas and it honestly creates a great looking weld that they can stack buttons with. Its Magnetic for sure. For SS wire your looking at CO2 shielding gas... I doubt they even have that around or know where to get it.

A bad welder and bad fitup at a shop means your chances of getting things right is very minimal... I wouldnt hold your breath on getting what you want out of this shop... Suggestion is to get your own SS exhaust kit, clamp it together till you can find a qualified SS welder...

 

Problem is it's on a daily driver and I don't have a 2nd DD car.

The other problem there is a shorty y-pipe (exhaust manifold is twin port) and a torsion bar right where you'd normally route the pipe. So you have to get the y-pipe positioned correctly and then the exhaust pipe. And it get worse, the manifold is sitting high and there isn't a lot of room between the frame and the oil pay (plus the torsion bar where your arm and welder want to be.)

They can bend pipe so rerouting they can do (they chinched on the reroute because they split a tube when expanding while welding up the y-pipe and ran out of tubing. I told them I'd get more, but they decided to reroute straight under crossmember to get job done.)

I'm an excellent welder and could have done the job, but since a DD driver, job must be done fast AND I don't have a lift AND I'm 69 and am so done crawling around under cars with jackstands. Last welding job was overhead welding directly over my chest not even 12" away. If it wasn't for scoring a high quality welding jacket with snap off apron, I don't know how I would have gotten that job done.

The shop isn't a rip off joint, they just had problems which I can appreciate. The deal was I would find the 304 materials (flange, pipe, muffler, clamps) AND free up the brass nuts at the flange. They had to fab a hanger or two and the total bill for the labor & welding was $436 which is cheap by todays standards - I doubt they made $50/hr. With other shops charging $100-150/hr, I appreciate any genuine effort a shop makes at a low labor rate.

My plan is to politely ask them I really need to get the pipes routed better. I'll tell them I'll get a 4' piece and some clamps and they can bend and swage. IF they welded with steel wire, then I'll tell them they said they had the right wire to do the job and using steel means the weld will rust AND eventually crack because the thermal expansion rate between steel and SS is difference - so each time the exhaust system thermally cycles, the weld interfaces are stressed.

My hatred of doing this kind of work is so great, I am still "showing a profit" for my decision to use them and the work they did.

I won't deal with drama anymore.

 

I think most muffler shops use a MIG welder these days. Changing the spool out to stainless wire is too much work for a single job for most shops. They run on a volume basis. Get 'em in, then get 'em out

 

A close up pic would help

 

Welding of stainless steel is typically done with C2 or 2% Carbon Dioxide and 98% Argon. In some cases there is tri-mix shielding gas containing 90% Helium, 7.5% Argon, and 2.5%Carbon dioxide.
Gas is ready available at the same place you buy 75/25 gas.

 

How much stainless work does the shop do ? If more than just an occasional one-off they could have a mig set-up with ss wire and appropriate gas ready to go. I'd ask.

 

If you can't/won't provide the name of the shop, can you at least tell us in which state it's located so we can avoid it?

 

Forgot about trimix... its been a while... Yep its readily available at most welding supplies... Good welders will backpurge the entire pipe with shielding gas to ensure weld integrity...
Like I said, I don't think that shop will change out wire and a bottle for this job... Doesn't sound like that kind of establishment. Interested to see what the job looks like now vs their fix......

 

I used to deal with a guy who owned an industrial supply house that's primary product was sanitary stainless tubing. He was a life long rodder who had a 34 Ford two door and when he took it to Portland to have a full stainless exhaust system put on it and took his own tubing they found out that the sanitary tubing didn't bend well in a regular tube bender. He ended up having to buy stainless tubing made for exhaust work.

I've found out the hard way that you do not use a steel wire brush on stainless as it will leave steel fragments in the stainless that will rust. I did that on my rear bumper when I wire brushed the welds on it.

 

I built these on my roadster, used tri mix gas (75% argon) and SS wire in a Miller MIG. It doesn't work really well IMHO. Good enough to sand and polish but they were kinda crappy looking welds right out of the torch.

 

Pre bent u bends and ss pipe made for exhaust would be my preferred method. Tack the pipes together while under the car and then remove to TIG weld up joint while purging the pipe. Too much work for me if a daily driver. No muffler shop is going to the expense of buying a gas bottle for $300-$400 and pay to have it filled with gas plus the wire for maybe one or two cars a year that need a ss exhaust system.

 

Why go to the trouble and expense of stainless on a daily driver ?
And besides,,,,,you should have asked if they had the correct wire for stainless.
Also,,,,since the welds look like crap,,,and the pipes were not routed correctly ,,.,could they have really been all that good to start with ?
Sorry for your misfortune .

Tommy

 

I worked at a shop that did custom exhaust .

we just used plain old mig welding ware and shielding gas.
Had a can of high heat silver paint to paint the welds with a thin brush so they looked “ clean “ and where protected.

not great , but the amount of stainless we did we never had a complaint.

I did exhaust on some cats you swear you could not get a pipe cleaner in the space you needed to get the exhaust pipe to fit. Patience and time would get you any desired bent and fitment. There where times after a road test you would need to tweak something as body roll or big bounces would cause some contact or noise. Patients was key.

had a customer come in with a 69 convertible camaro that was just mint with an exhaust kit , what a hunk of trash!!!!! Did not look good at all, re fit it 3 times for the guy , he was still not happy, finally talked him into using just the mufflers snd a few bits snd let us bend up a system for him that tucked up nice and neat.

exhaust work is an art form into itself to do it as nice looking as possible .

 

the exact reason that I started doing my own exhaust work

 

There was a guy here that did all the good work for over 30 years now .
He would custom fit every pipe he made,,,,tucked everything up close,,,,super job .
It all goes back to how hard are you willing to try ,,,he did .

Tommy

 

Agree 100%. I've got about 9# of a 10# spool of 308L that's been sitting on top of my MIG power supply for probably 15 years. Has a job back then to build a storage box from 16ga 304. Customer wanted it mig welded so I got the wire and a cylinder of trimix. Fooled with voltage, wire speed, and slope for an hour or more on some practice pieces I'd sheared, and the best combination I could come up with still looked barely better than a string of bird turds.

I'd formed everything possible in a press brake and a box brake to minimize the welds. Welded the damn thing up, and everything looked good except for the welds. No way was anything going out the door looking like that, so I knocked it down to somewhat even with a flap disc and then walked all the joints with the Tig torch. Thus ended my short lived career of mig on stainless.

Talked later with a couple shop owners who do a good bit of stainless fab work, and both said wire works good on 11 ga and heavier, but neither had any luck in making nice looking welds with wire on light gauge SS material.

 

Made an error, on my '31 roadster S.S. header mods. Didn't flush the interior gap regions, w/a second feed of inert gas. TiG. Ended up w/a depleated chrome ring that rusted. Likely as they run, heated, even only in damp weather.

 

309 TIG wire is for stainless-to-mild steel application.
308/310 for stainless material (will work on mild steel too)
I never could get 70-S2 to flow right on stainless and IF it did it would not hold.
I agree with the other guys.......I DOUBT a commercial muffler shop used SS wire to weld your stuff!
Unless they had a SS rig already set-up....prolly some 'jack-leg welder' just slung-what-he-had-in-the-gun on your pipes.
I DOUBT they will do it any different the second time around.
Shouls-woulda-coulda used mild steel tubing to begin with if you're depending on a commercial shop .
Maybe I'm worng
6sally6

 

Could very well be mild steel wire used. But also look up sensitization. I have replied about it many times. It is what causes rusting even when using stainless filler wire.

 

I don't care how good a shop's intentions are. If they don't have the skills/equipment to do a professional job, I'll take mu business elsewhere. I can't afford to pay twice. I don't like to see businesses fail, but sometimes you have to wonder why they got into the business in the first place.

 

A lot of new cars (since the early 90s) have stainless steel exhaust systems from the factory. Due to the higher exhaust temperatures.

 

I bought a stainless cat-back system for an OT car some years ago, discovered that they welded mild steel flanges and hangars on it. Took it to work and made new pieces out of 304 stainless, then cut out the MIG welded sections because the welds burned the tubing on the inside. Put an argon purge through the whole thing and TIG welded it back together. That system had over 200k on it and still looks decent despite being subjected to Maine roads and weather...my son saved it for one of his project cars. .

 

I built my entire system out of 409 SS alloy. I simply bought a spool of 308 off of eBay, put that in my Miller and used the same tanks and settings I had in the welder for welding mild steel. This produced great welds with absolutely no changes needed.

 

409 (a 400 series) is a magnetic grade of stainless steel. Less chromium and not much else for alloy addition. It is what most OEM stainless exhaust systems are made from. 300 series are non magnetic, and have more chromium and also nickel that provide more corrosion resistance.
Not trying to say your exhaust is bad. Just pointing out that the chemistry is why it welded better. It should stay nice and corrosion free on your hot rod.