Welding 304 SS to 409 SS

[snrusnak]

I'm a newbie welder, I have a lincoln MIG(I have only used it as flux core) I bought from home depot or lowes. It's pretty idiot proof, I've only used it to weld mild steel for household lawn equipment, etc.

I want to weld some exhaust pipe for my truck, I THINK the stock exhaust is 409 SS because I know it is stainless but it looks to have minor corrosion. The muffler I bought is 304 SS, can I weld these together using the flux core method? I assume I'll need a different spool of wire for the SS but I'm not really sure.

Any help from you guys that have more experience is appreciated.

 

[d_adams]

Most likely, use 309 ss filler or wire for dissimilar stainless types. Always go one grade higher for stainless for filler, so 304 needs 308, 316 should use 316L, etc. Welding mild steel to 304 stainless, use 309 filler. There's a lot to learn on welding and I know just enough to be somewhat dangerous.

Readily welded but a pre-heat of 150-260°C is recommended. Grade 409 or Grade 430 electrode or filler rods can be used, but AS 1554.6 pre-qualifies welding of 409 with Grade 309 rods or electrodes. These austenitic fillers result in a more ductile weld.

 

[snrusnak]

There's a lot to learn on welding

Yes I've certainly figured that out lol, and the fact that I know little about it and the materials.

I appreciate your help, I have one question I'm confused about. You say to use one grade higher but then say to use 309 ss wire for dissimilar ss types. Since one type will be 409 ss, should I use one grade higher(i.e. 410 or whatever it may be) or 309?

I'm not sure how the grade scale works but assume higher number = higher grade? I was under the impression 304 ss was better than 409 ss (for exhaust applications, anyway....as it is more corrosion resistant, it has more nickel and chromium I think).

Thanks again....I'll have to see if I can find a spool of flux core ss wire.

 

[snrusnak]

Found this:

UltraCore® FCP 309L

For welding dissimilar metals - stainless and mild or low alloy

Dissimilar Joints – Stainless types 410, 304L, 321, and 316L to mild and low alloy steels

Looks like what you recommended, 309 wire.

 

[d_adams]

304 won't really rust if it's polished, 409 is intended to get a surface rust or scale to preserve it. It will last forever, that's why magnaflow uses it. They build for the automotive market and the exhaust is typically hidden, so they win for longevity. I think 304 may be more prone to cracking over long term based on the material characteristics. It's got something to do with the crystaline structure.

 

[snrusnak]

The muffler I bought is like a knockoff magnaflow, but it is 304 IIRC. It is not polished. Do you think it will hold up ok? I'm not in a corrosive environment anyway, here in orlando.

So it pretty much won't matter much in my application if I weld the 409 to the 304, and I should try out the 309 wire?

Also, I found some T201 pipe cheaper and it seems to be a good corrosion resistant SS, just cheaper. Would this weld easily to the 304 and 409 with the 309 wire, in your opinion?

 

[d_adams]

The stock headers on xb's should be 304 as far as I know. If you're welding 409-304 then use 309 filler. I can't give an opinion on the 200 grade ss, but I wouldn't recommend it.

 

[Timeless]

You will be fine with the 304 muffler and it will definitely last assuming it is actually 304SS. If its an ebay can from China its hit or miss. Welding it in will be a whole other story.

If it were me...and I only had a flux core mig machine, I would go to an exhaust shop and have them weld the muffler in. I can't imagine it costing much and you wouldn't have to worry about your weld coming apart.

However, if you want to have some fun, d_adams is offering sound advice. Also, the 309L wire should work. However, from its spec. sheet, it seems to require a shielding gas.

 

[snrusnak]

I have a buddy that has a TIG, and he would do it for free. He is also fairly new to welding though, but knows more than I do and has better resources through people he knows through work.

I was looking to have some fun and practice/learn. It will probably take me more time than it's worth like you said but that's part of learning, and I'll be able to use these skills later on.

Does that mean that there is no such thing as a 309L flux core wire?

Thanks again guys.

Oh and the muffler is off ebay but not a china part. It is from an ebay company I think they are made in Hialeah Florida.

 

[Timeless]

The 309L wire that I found from Lincoln clearly says its flux core. However they seem to still be recommending shielding gas. Check it out here

I cannot comment on what would happen if you welded it with out shielding gas because I have no idea.

 

[snrusnak]

Ok thanks for the info. Maybe I'll try a welding forum at this point to see what they say about the wire.

Last resort I'll take it to my buddy to use his tig, I'd just like another skill in the toolbag...

 

[snrusnak]

Thanks again for the help guys. I went on a welding forum and everyone gave the same advice. They confirmed that it's pretty much not possible(or at least not correct) to weld SS with flux core without additional shielding gas. So I'm going to mock it all up and tack it together with the mild steel flux core wire then take it to my buddy to have it TIG welded. I might invest in some tanks soon...

 

[d_adams]

You can buy the really small argon tanks, but anything typically over 40 cubic feet is a lease. I have an 80 for traveling and a 300 for at home.

 

[snrusnak]

Another guy just commented and said I can use this certain wire I think it was called core bright, without additional gas, but it's smallest diameter was 0.045" and I think my machine will only go as large as 0.035" although not positive.

 

[snrusnak]

I got a plan. got a lot of good info from a welding forum. I decided to go with aluminized steel pipe for what I need and they said I can weld it to the SS with my wire, it just won't be stainless anymore. I can just put some high heat paint over it, I'm not in a corrosive area anyway, and will likely change the exhaust after some years. I chose aluminized since it's like 1/3 the price. I can weld it to the SS with my flux core MIG welder. My last question is what do I use to cut it? This is pretty cheap, would it work? I have several cuts to make in the exhaust pipe.

http://www.harborfreight.com/2-hp-14-inch-heavy-duty-cut-off-saw-91938.html

 

[theMelvster6]

Since we're on this topic...what is the proper way to back flow the stainless tubing?

 

[d_adams]

The chop saw you linked will work, plan on de-burring the tubing though and the cuts will not be perfect.

Back purging requires capping off both ends with a fill line on one end with a metered outlet on the other. Masking tape will work in a pinch, poke a couple of small holes in it with either the tungsten or the filler rod. Depending on the size & length of the tubing, purge for at least a couple of minutes, once it's filled/purged, the flow rate can be turned down some. I usually run 5-10 cfm on the back side. I think the correct displaced amount is 5x the volume of the pipe/tube, but I usually get caught up talking to someone on the phone and forget that it's sitting there running. [sad]

 

[snrusnak]

Maybe one day I'll get to that level lol. Most of this is way beyond my skill level currently, but I'm hopeful I can make this project work with what I have.

Thanks for the confirmation on that saw. Deburring is no problem, and as long as the cuts are decent it'll work. Can't be worse than free handing it with the sawzall(that's the other option)...

 

[snrusnak]

And just to confirm again....I have a miter saw, but it spins at like 5,000 rpm as opposed to the 2,500 of that metal cutting saw from HF. That won't work, correct(too fast)?

 

[snrusnak]

I bought that HF chop saw, works well. At least for this minor work. I just cut a couple pieces of 2" steel exhaust pipe and it went right through it, decent piece for the money.

I know a lot of HF stuff is crap(and made in china), but damn sometimes I just can't afford to buy all good tools, especially stuff like this that I'll rarely use.

Unfortunately.....my welding "skills" are less than adequate. I'll have to keep practicing before doing my exhaust lol. I've probably only welded for about 30-60 minutes since I got this welder. I eventually got a couple decent beads, but most of them were awful. I was throwing the breaker(I think the previous owner of my house spliced an outlet because there's a random outlet in some shelving in the garage, and that's what I was using). So every time I turned the welder up to get more heat it would run about 2" of bead then trip the breaker. I'll try another outlet...