Mig 304SS with 75/25?

[65-408]

what happens if you use 75/25 to mig 304SS with 308L wire? it is an exhaust pipe, and my main concern is that it doesn't rust... doesn't have to be perfect looking...

[cruizer]

Alot of firms sell stainless exhausts that isn't really stainless, does a magnet stick to it?

If not then you should use straight argon, if the magnet sticks, just use reg mig wire.

[SundownIII]

Straight argon for SS? Really.

If the exhaust pipe really is SS, if you weld it with C25, it WILL rust, due to the introduction of carbon to the bead via the gas mix.

If the exhaust is SS and you want to "do it right", then you should use a tri-mix to preserve the rust resistance of SS. A couple guys have recommended a 98% Argon/2% CO2 mix, but I have no personal experience with that mix.

Having tri-mix on hand for "small jobs" can be an expensive pain, but it is the "accepted industry standard" mix. I don't do that much SS with mig, but I keep a 330 on hand for those situations that dictate SS/mig. (Marine fab).

Cruiser,

You put out a lot of good info, but think you're off on this one. Maybe you could refer me to a "recognized source" that recommends straight argon for SS.

[con_fuse9]

I was faced with the same dillema. For a cheap 409 stainless factory exhaust doing some welding away from my shop.
I could
1) Drag the dynasty out over the gravel driveway (hate doing that - mostly the bottle weight).
2) Drag the MIG out there and buy a spool of stainless wire and mix the gas (double PIA). Not to mention getting a spool gun in all those tight places is rough.

or

Drag stick welder out there and use stainless rods. Modern inverters like my Maxstar has a DIG feature which let me weld with 3/32 rods at something like 40 Amps. If you aren't butt welding this isn't an issue at all. I flaired one side of the pipe and it was essentially a lap joint.
I used the stick to tack everything in place and then lowered the pipe to get all the way around. Did everything off a 110V extension cord. I was going to finish it off with TIG (and drag a 100% argon bottle out) but I was having too much fun with the stick welder.
BTW, I have an air cooled torch for the Maxstar but no short cap - just the long one. I would not have been able to get it in all the places I needed.

Stainless stick rods are about 10x the cost of your basic 6010. My LWS has them in what I guess is 1# packs so its still the cheapest way to go. 3/32 is not so common but they stocked it at another location so I just had to wait a day.

Oh, and the final weld was not too bad. Pretty sure I got all the slag out of there and it actually didn't look like bird droppings. I'd say it look at least as good as the other obviously wire welded beads.

BTW, they make flux core wire for stainless steel welding with C25 - its just OMG expensive. Cheaper to get the right gas and use 308 or 309 wire.

If you see a future in 304 stainless exhaust work, go buy a TIG and use 100% argon. If you are doing one quick fix, consider a stick welder solution. Just keep in mind that 40 Amps on a 3/32 308 rod will typically stick a lot. DIG is a really nice feature for us amateurs.

If you have to MIG it, wait till you price out a roll of stainless wire... Check Craigslist, you might find stuff for less. So a 30# of stainless will be more like $100. If you can run a small spool go for it. Spool guns however have access problems under cars. Keep that in mind.

[Hillbilly69]

SS with 100% Argon

Sundown I don't see what the big deal is with straight Argon.

The initial post was obviously a one off project just doesn't want it to crack or rust?

I would find a bottle of pure Argon much more usefull than a bottle of Tri mix. At least with 100% Argon you can use it for a lot more uses. And he can purge with it.
I attached some documentation just like you asked.

http://www.advancedweldingsupply.com/gas%20guide.html

The O2 just helps wet out the puddle.

[SundownIII]

Hillbilly,

Pretty obvious you don't do much stainless steel mig welding.

I saw nothing in your "referenced article" that suggested the use of straight argon for mig welding SS was recommended.

[jelias]

I have welded stainless with 75/25, 90/10, 98/2, and trimix. The trimix is definetly the best gas. And it will rust with 75/25, but it will not be extreme like mild steel. It just a matter of how much your willing to spend. Depending on how much welding you have to do it might be cheaper to take it to a shop and have them weld it. To buy a roll of wire and a bottle of gas your looking at a bill over 100 bucks.
But like said make sure it is real stainless before you put the money in it. If its not than just weld it with whatever you have.

You have alot of options it all deoends on how much money you want to spend. If it were me i would tack it up with whatever you have and take it some where to be welded. Chances are it will be cheaper than getting everything you neeed to do it right. Unless you have a stick welder like suggested or a tig.

[cruizer]

figured Argon would be a cost effective alternative, though i'm mistaken. Just tryed it. arc is ok, not alot of penetration though, (kinda ropey). Went to 98/2 (2%) CO2. Welds were much better, good penenatration. but didn't flow so good. Tryed 98/2 (2% oxygen) flowed great, good penatration. Tri mix had best flow, penatration and cleanest welds.

Now I get to play for free, as companys give me the bottles. I'd go with the 98/2 (2 % oxygen) as you can use the bottle for other materials.

[Hillbilly69]

Ss mig

LMAO

Sundown you treat everything like it's for NASA........?

The poster just wants to bubble gum some exhaust together.

IMO critical or important stainless is not worth welding together unless it's GTAW or FCAW

[MMW]

quote; what happens if you use 75/25 to mig 304SS with 308L wire?

It will be more likely to rust/corrode than if you used tri-mix which is the recommended gas.

This does not mean that it will rust out right away as it will still be more corrosion resistant than carbon steel.

[65-408]

thanks guys for the replies, it helps alot. The job I have is the exhaust system for my 65 mustang fastback.

I want a custom routing, I want real SS so that it never rusts, and I like to do stuff myself.... The plan is to buy 304SS bends and piece it together, it is a pretty simple system. I already have the small spool of 308L wire, sounds like I just need to get the right gas...

[diamondback]

so it isn't a bubble gum project? I would want a top notch job on that car.

Cherry pick the right answer and do a good job.

[big mike]

If you decide to go with tri mix be aware that the tri mix they are talking about is helium base tri mix......sometimes called A-1025 and not argon/CO2/oxygen for mild steel.

[SundownIII]

No Hillbilly, I don't work for NASA, but I do believe in doing things right.

Just last year I had to "redo" the entire bridge handrail on an overseas built trawler. The bridge rail had been "repaired" using SS mig wire and C25. Every one of the welds had rusted through.

What should have been a $500-600 repair ended up costing the owner over $2,200 for me to grind out the old crap and repair with tig. Had he broght it to me in the first place, the repair (less grinding) would have been much less.

As Cruizer has found out, straight argon will produce a bead that will not "flow out". Even though I mix my own gas and have the capability to mix Argon/O2 and Argon/CO2, I only do so for a spray mix. The 98%Ar/2%CO2 mix is a recommendation from Ed Craig, and I clearly stated in my previous post that I had not used that mix for SS. 98%Ar/2%O2 is a good mix for spray transfer on mild steel.

[Markswelding]

Straight argon for SS? Really.

If the exhaust pipe really is SS, if you weld it with C25, it WILL rust, due to the introduction of carbon to the bead via the gas mix.

If the exhaust is SS and you want to "do it right", then you should use a tri-mix to preserve the rust resistance of SS. A couple guys have recommended a 98% Argon/2% CO2 mix, but I have no personal experience with that mix.

Having tri-mix on hand for "small jobs" can be an expensive pain, but it is the "accepted industry standard" mix. I don't do that much SS with mig, but I keep a 330 on hand for those situations that dictate SS/mig. (Marine fab).

Cruiser,

You put out a lot of good info, but think you're off on this one. Maybe you could refer me to a "recognized source" that recommends straight argon for SS.

That would be ok if your Gas tungsten arc welding, or tig, heliarc, what ever verse you choose but not mig welds.
Yep tri mix I need a bottle myself.