Welding my exhaust system... (16ga 409 SS)

admin

I've been posting in the Harbor Freight section for some time since that's they type of welder I have, but have yet to post in the general forum asking for help. Here's my first question I'm bringing to the table....Long story short, my exhaust system was torn off my truck (mint condition) and I need to put it back on. I don't want to use exhaust clamps this time, so I'm hoping to weld it. I've looked up the exhaust system on the internet and it's 409 stainless steel. (can rust a little, magnetic) I also believe it to be 16 gauge thick tubing.I'm pretty sure my equipment is adequate, but I'm not sure what wire to use with it? Can I just get away with regular ER70S-6? Or do I need to purchase special SS wire? If so, what kind? I'd like only to purchase a 4" spool (the 2lb size). I'd also prefer .030" or .035". I found some wire on Lincoln's site which is specifically for automotive exhaust systems made of 409 SS, but it's .045 and only sold in 33lb & greater sizes.PS - I don't want the welds to be too brittle as my truck is one shakey diesel....Thanks for the help!Chicago Electric 131 Dual MIG Welder 120Vhttp://www.gr8lakeinnovations.com2x Associates of Automotive Technology: Transmission Technician & Under Car TechnicianAssociates of Electrical Engineering Technology
Reply:Yes you can weld SS with E70 wire, but the weld will rust. Some of the others here are probably more familiar with what alloys would be best for this as well as gas suggestions (you do have a mig as opposed to a FC machine right? It helps if you post up what you have to work with.)One suggestion I have is for you to get some similar tube for practice. Small tube mig is not the easiest in the world to do, and laying on your back under the truck will make that 10x harder. You will want to practice in position. Get a sheet of plywood and set it up so it's roughly at the height of the floor pan off the ground. Add some 2x's to simulate the frame rails and position you test pieces about how you will need to tack and weld them. Then lay on your back and try to do the weld. I'll almost grantee you will screw it up the 1st 4 or 5 time minimum, especially on top where you cant see/ work well. You might just think about using clamps in strategic places to avoid welding under the truck. It's simpler that doing a strange out of position weld on tube while on your back. If you can get access to a lift and work upright it will be slightly easier, but you'll still need to practice the tube joint over your head..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Most auto parts stores sells replacement hangers that utilize the factory attachment points on rubber isolators for your exhaust set up.I would go to a real weld shop and buy stainless steel mig wire and a bottle of 90-10 or pure argon - just to be on the safe side.My other suggestion - would be to pay someone to weld it for you with a professional machine.  There are times where you have to splurge and spend the couple extra bucks and just pay someone to do something for you.Even I have people weld for me on occasion.There is no shame in paying someone $40 or what ever to have the job done professionally.The best job would be to tack it in place and then take it off and weld it off the vehicle and then put it back on.
Reply:Originally Posted by DSWYes you can weld SS with E70 wire, but the weld will rust.
Reply:Originally Posted by sirhannick I have a tank of 100% argon that I use (for aluminum & steel).
Reply:Originally Posted by sirhannickThanks. That's some helpful info to know. I am aware of the difficulty of an upside down, under the car weld. Just haven't done stainless before. I have a MIG machine, not just a flux-core. I have a tank of 100% argon that I use (for aluminum & steel).If anyone is interested you can see my complete build here:http://www.4btswaps.com/forum/showthread.php?3928It's a long thread, but goes start to....almost finished i/e current.
Reply:What in the world are you doing that you ripped your exhaust out of the truck??    Did it just come apart at the clamp locations?The front of the aftermarket stainless muffler on my truck is welded into the stock 4" tubing.  I had a muffler guy do that and he said he had a hard time welding the pieces together.  I don't know what setup he was using but he got a lot of popping.  I have no idea if he was worth a hill of beans or not but my stuff hasn't fallen off.  The rest of the exhaust is just in the hangers and clamped on at the down pipe and cat.  The expanded ends area generous length so there's no room for it to move out of place.  That and the corrosion I'm sure keeps it stable.  So you shouldn't have to weld it up overkill I don't think but just enough.  I've got a rattly diesel too.  One thing I won't do is just tack weld a tip.  That will break off Lincoln AC225 and CartLincoln WeldPak HD and CartOne hand
Reply:308L or 309L stainless steel filler metal will work.  your 409 stainless base metal has barely enough chromium to even qualify as stainless steel.  As someone else mentioned, you can weld with ER70S-6 wire for low carbon steel, but you will sacrafice all the corrosion resistance in the weld bead and heat affected zone around the weld.If you're going to go to the trouble of welding this with stainless steel filler, you must use either a tri-mix shielding gas(expensive) or an Ar/CO2 mix with 5% or less CO2.  Higher levels(>5%) of CO2 will contribute carbon to the weld bead.  The carbon pickup will ruin the corrosion resistance of the stainless steel weld metal.  If you can't get 95/5 or 98/2 Ar/CO2 shielding gas, you might as well just use ER70S-6 and standard 75/25 shielding gas mix.  It'll corrode at about the same rate either way.Do not use 100% CO2 with stainless filler.  Even if you can establish an arc, you will not make a sound weld.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:A lot of 409 exhaust systems are actually coated with Aluminum to keep them from turning brown too fast.  I bet the aluminum was causing the popping.I changed around the exhaust system on my Superduty to clear the gooseneck hitch and get rid of a couple restrictions.  I used 309 filler and tig'd it all together.  That took quite a bit of time and those welds all flash rusted pretty fast so I don't see much advantage of using the stainless filler metal.  I'd probably vote for just using ER70 with the mig. Originally Posted by MonicaWhat in the world are you doing that you ripped your exhaust out of the truck??    Did it just come apart at the clamp locations?The front of the aftermarket stainless muffler on my truck is welded into the stock 4" tubing.  I had a muffler guy do that and he said he had a hard time welding the pieces together.  I don't know what setup he was using but he got a lot of popping.  I have no idea if he was worth a hill of beans or not but my stuff hasn't fallen off.  The rest of the exhaust is just in the hangers and clamped on at the down pipe and cat.  The expanded ends area generous length so there's no room for it to move out of place.  That and the corrosion I'm sure keeps it stable.  So you shouldn't have to weld it up overkill I don't think but just enough.  I've got a rattly diesel too.  One thing I won't do is just tack weld a tip.  That will break off
Reply:Originally Posted by ChuckA lot of 409 exhaust systems are actually coated with Aluminum to keep them from turning brown too fast.  I bet the aluminum was causing the popping
Reply:I doubt you got hosed on the muffler, if it says its 304 stainless than it probably is.  But you said he welded it to the stock pipe.  I'll bet the stock pipe was 409, and possibly coated with Aluminum.This kind of explains it.http://www.aksteel.com/pdf/markets_p...a_Bulletin.pdf Originally Posted by MonicaInteresting.http://www.aeroexhaust.com/index.php...l-exhaust.htmlThat's an AeroTurbine 4040xl muffler.  The product info states "composed of high quality 304 stainless steel".For nearly $200 I got hosed!
Reply:Originally Posted by ChuckI doubt you got hosed on the muffler, if it says its 304 stainless than it probably is.  But you said he welded it to the stock pipe.  I'll bet the stock pipe was 409, and possibly coated with Aluminum.This kind of explains it.http://www.aksteel.com/pdf/markets_p...a_Bulletin.pdf
Reply:Okay, so it sounds like more than the filler metal I'm using, the gas is key. And I'm all wrong with the gas I've been using (except for Aluminum). I will have to buy another tank I suppose so I can have the correct gas for steel and stainless. I might just stick with the ER70, but even still, my gas is wrong. Thanks a lot guys. I didn't even realize that was a flaw in my "plan". I need to get a better welding book than the one I have....Chicago Electric 131 Dual MIG Welder 120Vhttp://www.gr8lakeinnovations.com2x Associates of Automotive Technology: Transmission Technician & Under Car TechnicianAssociates of Electrical Engineering Technology
Reply:409 is a pain to weld and still get corrosion resistance.   BTW, 409 stainless should be magnetic so its a pretty easy test.409 is most commonly welded with 309L or 309 filler.  409 filler can be used and it can be welded autogenously (welding without filler).   You should preheat a bit - like 400deg F or 200deg C but typically don't have to on thin tubing.  This is a very easy stainless to overheat.  Use minimal welding heat.Shielding gas should be low CO2 as well.  There are some high dollar inner shield wires that might work for you - I believe you can find some that will work with C25.  That might be a cheaper way to go that  tri-mix.  ESAB makes a flux core wire called shield bright that can work with C25 (or 100% CO2).The nickle content in the 309 rod will compensate to an extent to any hardening of 409.  The L means low carbon and will help keep the carbon out of the base metal (carbon helps chromium precipitate out).I've only recently played with quenching 304 stainless welds (it improves corrosion resistance) and I have not found anything on the practice with 409 except to say that 409 has similar sensitivities to carbon.  Basically you should back purge and keep carbon out.  I did find one article promoting rapid cooling in order to maximize post weld corrosion resistance (they mean either quenching or forced air).Bottom line, don't let what little chromium is there leak out.Last edited by con_fuse9; 08-31-2010 at 07:19 PM.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:Chuck,  agree with your comment about aluminum.I suspect the problem you ran into was TIG welding exhaust pipes that had seen some use.  If upstream of the CAT converter, or on a car without CATs, you'll get a lot of carbon deposited on the walls of the tubing.  Raise the temp into the range of 600F - 1500F and you'll get that carbon reacting with the chromium in the stainless.  When this happens all the corrosion resistance of the stainless dissappears.The fix is:1 - only to weld on new clean, stainless with low carbon stainless filler filler(309L) and TIG(pure AR) or MIG with 95/5 or 98/2 Ar/CO2.  If your base metal isn't a low carbon stainless steel grade to start with, then you may be screwed no matter how careful you are.  2 - Try to clean all carbon residue out of used tubes and follow #1.  Think flap wheels, solvents, and/or acid to remove all surface contaminants before welding...3 - weld and then heat treat the stainless.  Take up to 1600F in an inert atmosphere or vacuum furnace.  Then rapidly quench down to below 600F.  This will dissolve all the chromium carbides in the weld and HAZ, and the quench will prevent them from reforming.  It's slow cooling through 1500-600 that's killing your corrosion properties.  Distortion may make this option pointless.#2 is hard to do#3 is usually impractical to do.and #1 may be beyond your control.I didn't read the OP's initial post, or I'd have mentioned this items earlier.   Originally Posted by ChuckA lot of 409 exhaust systems are actually coated with Aluminum to keep them from turning brown too fast.  I bet the aluminum was causing the popping.I changed around the exhaust system on my Superduty to clear the gooseneck hitch and get rid of a couple restrictions.  I used 309 filler and tig'd it all together.  That took quite a bit of time and those welds all flash rusted pretty fast so I don't see much advantage of using the stainless filler metal.  I'd probably vote for just using ER70 with the mig.
Reply:Originally Posted by sirhannick... I will have to buy another tank I suppose so I can have the correct gas for steel and stainless. ....
Reply:Nice reference from the AK steel website.  I hadn't seen that before.  For the OP and others reading all stainless steels are suceptible to this problem to some extent or another.  304 is more resistant than 409 to sensitization; another term used to describe the loss of corrosion resistance.The more chromium the alloy has and the less carbon, the more likely the alloy is to retain it's corrosion resistance after welding/heating. The real jump in performance comes from using grades of stainless that contain titanium,niobium(aka columbium), or tantalum.  All three of these elements act to shield the chromium from any carbon that is present.  They act like a sponge for carbon, soaking it up and preventing it from reacting with the chromium, which provides all the corrosion resistance.  The reason you don't see these grades in exhaust components is simply that they're too expensive to use.  Nobody would pay for a muffler welded from these 'stabilized' grades of stainless steel. Originally Posted by ChuckI doubt you got hosed on the muffler, if it says its 304 stainless than it probably is.  But you said he welded it to the stock pipe.  I'll bet the stock pipe was 409, and possibly coated with Aluminum.This kind of explains it.http://www.aksteel.com/pdf/markets_p...a_Bulletin.pdf
Reply:Last edited by Fat Bastard; 09-03-2010 at 11:52 AM.