Welding 16ga stainless exhaust pipe

[rangerfredbob]

It's been near 90F for most of the last week so projects have been slow...

I did have a thought... structure wise and welding wise I think it would probably be a reasonable idea to cut a short sleeve of tubing (say an inch or bit more) to go on the inside of the seams instead of just butt welding then leaving a wall thickness gap for the butt for filler material.

I looked and I have a 2lb spool of .030" stainless MIG wire so the twisted pair should be reasonable for a filler rod I imagine after watching some more video's and such...

 

[BukitCase]

If you know which stainless your mig wire is, it'd be good to check the filler metal section on the link I posted; hopefully the mig wire is 308 or 309... Steve

https://www.google.com/search?q=308L+mig+wire+2+lb+roll&client=firefox-b-1-d&ei=EpNmZJb4IIiJ0PEPk6OmoAE&ved=0ahUKEwiWyZbN4v_-AhWIBDQIHZORCRQQ4dUDCA8&uact=5&oq=308L+mig+wire+2+lb+roll&gs_lcp=Cgxnd3Mtd2l6LXNlcnAQAzIFCCEQoAE6CggAEEcQ1gQQsAM6BQgAEIAEOgYIABAWEB46CAgAEIoFEIYDOgUIIRCrAjoICCEQFhAeEB1KBAhBGABQmBpYnnJg-31oAXABeACAAdQCiAGNDpIBBzAuOS4wLjGYAQCgAQHIAQjAAQE&sclient=gws-wiz-serp

 

[rangerfredbob]

It's Fourney ER308 so I should be fine

 

[jwmorris]

I much prefer to work with aluminum for cold side plumbing. That said, TIG looks best but you can MIG stainless just fine with regular ER70 wire

 

[rangerfredbob]

I did think about that just didn't want it rusting but I guess there wouldn't be too much in the air pathway with a straight butt weld... I mean it's an old diesel so there's going to be oil in the air from blowby anyway... trying to expand my options for fabrication anyway... Aluminum would have been nicer but stainless exhaust kits were cheaper and I didn't think about it plus even harder to weld but I'm going to try my hand at aluminum welding soon...

Haven't gotten very far on anything related to welding stainless, hopefully pulling the transmission out of the F350 tonight...

 

[etpm]

Please don't use twisted MIG wire. Just buy some TIG rod. It is not that expensive and will work much better. You can use 309 TIG rod or 316, it won't hurt to go higher in the number. Scratch TIG tends to pollute your electrode which will then give off light which makes it harder to see the weld. If you can, try laying a tungsten electrode right next to your work. Then do the scratch arc off of the tungsten. This will tend to keep your electrode cleaner. You will for sure get "sugaring" on the inside of the pipe. The term "sugaring" comes from the appearance of the heat affected zone looking like burnt sugar. You cannot avoid sugaring unless the area can be protected with argon. You can certainly MIG weld the joints with pure argon using stainless but it will look like ****. To get good looking MIG welds with stainless wire you need to use tri-mix gas. For your job it may be worth it to use a small cylinder of tri-mix. If you are already good at MIG welding then using tri-mix gas might just be the best way to go. Better welds, less sugaring on the inside of the pipe because the heat will be less. TIG welding stainless is deceptive because stainless does not transmit heat very well. This means that the heat affected zone heats up quickly and stays hot, so less heat needs to be put into the weld. Without a foot pedal you amperage is set to start welding but then you need much less heat. Since you can't control the heat and the metal is relatively thin the weld will get too hot and fall through unless you can move really fast and add rod at the same rate. This is tough to do for a novice TIG welder.
Eric

 

[rocco611]

stainless steel is one of the easiest metals to weld. If you decide to mig or tig weld the tubing plug the ends and flood the tube with inert gas. You said your familiar with stick welding, you could practice welding some 16 gauge stainless with 3/32 stainless stick rod .

 

[rangerfredbob]

Now that you mention that, I do have a few pounds of small stainless rods that I forgot about... I really need to get all my rods together and in the shop instead of in a pile in the garage...

 

[rocco611]

A few years ago I found a bunch of new 2" .065 stainless tubing at a scrap yard for $2 a lb. I bought it , then asked a muffler shop to bend it, they said they couldn't. I ended up making a bunch or 15 degree pie cuts and tig welded them together for the exhaust system on my falcon. There were very few places I actually had to use any filler rod, I was able to run a puddle all the way around most of the tubes without any filler . Cool thing about pie cuts is they make really smooth tight turns real easy.

 

[rScotty]

Did you ever do the welding? Some stainless alloys are very easy to weld. I liked your idea to sleeve instead of just butt weld. BTW, almost any type of welding will work with stainless. I use oxy/acet and start with some spot welds just to hold all into position and then either add rod if it is flowing well or else switch to hi-nickle bronze rod for making the joint stronger and as a filler.
Sleeve it appropriate to the geometery. I've never had luck sleeving bends so I try to put the joints elsewhere.