Stainless Steel welding im new here...

admin

Hey guys its nice to meet all of you i do have a good idea of the operation of the tig machine i did take a class through college on it but im wanting some input.im looking to make a custom exhaust for one of my cars 4" stainless pipe can someone tell me the best way to back purge something like this i have a single tank and single flow meter on it currently using 100% argonwhats the best type of tungsten to use and filler rod for 304 stainless like this http://www.speedymetals.com/pc-4516-...-annealed.aspxthanks guys
Reply:I'm pretty new at this so feel free to question anything I say.The web link showed a 4" pipe w/ .120" wall.  That seems pretty thick for an exhaust pipe.  I'm thinking more like 16 ga (.063"). I see 308 filler recommended for 304 sst base metal.  I've used this with good results.  I also use 2% thoriated tungsten ground to a long taper...small flat on the end. Miller's GTAW handbood says for 1/8" material, use 3/32" tungsten, 120 to 150 amps, 1/16" filler rod dia., 3/8" gas cup (#6), 20 scfm 100# argon.  For 1/16" material, use 1/16" tungsten, 80 to 120 amps, same rod dia, cup, flow as before.As far as back purging, I've used Solar flux instead of back purging and had very good results.  J W Harris sells it for about $40 a can and one can lasts a long time.Hope this helps.Miller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:thats a nifty way of doing it instead of back purging you say you still have good results with it ? does it do as nice of job as back purging?
Reply:Guys here that know exhaust systems may give you better feedback, but I'm sure the 1/8" thick material is thicker than normal for this application and overkill, but for a beginner this could make welding alot easier for you.  At this this thickness, for an exhaust application, you would not need full penetration, so you would not need to back purge or use solar flux if you dialed in your amps for about 1/16 to 3/32" of partial penetration (pulsed if you have that option).  With this extra cushion of thickness your could more easily do an autogeneous weld without having to add any filler.  Again to make it easier for yourself, so you don't need to add filler, you want a perfect, square butt joint fitup, with no gap at all.  Practice on a joint mockup first and see what amperage the joint can handle at your welding speed before buring holes and sugaring your actual exhaust system.  Thinner material is only going to be more challenging, needing purging, and more precise joint fitup and welding technique.As for tungsten and filler:  2% thoriated, ceriated, or lantanated, anything but pure tungsten.  This weld will only take about 60 to 80 amps constant current or average pulsed current, so the electrode could be 1/16" or larger, shapened to like a pencil with a blunted end.If you need filler because your fitup is not good, or because you cannot weld like automated orbital tube welder, 308 is the common filler for 304, any 300 series filler would be ok, 316, 309, 312, 321, 347.
Reply:To be honest, I haven't used back purging so I can't compare.  I have welded stainless w/o any back purge or flux and got a lot of sugaring.  The flux stopped that.  I'm sure the back purging would have as well.One thing's for sure.  Using Solar flux saves argon so your tanks last longer and you don't have to rig up tubing, plugs, dams, seals, etc. like you do with purging.What you will notice is that the flux leaves a very hard, glass like residue that's difficult to get off.  Of course, on an exhaust pipe I wouldn't think that would matter.Miller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:very true im gonna have to measure how thick the pipe is i have now thats just mild steel thank you for the responses it helps out greatlyanyone have any method to there madness when it comes to cup size collection?also when it comes to tungsteni know with aluminuim pure with steel 2% but as far as using thoriated or ceriated or lantanated?thanks again guys!
Reply:I'd suggest you visit Miller's website.  They have alot of information regarding machine settings, electrode selection, cup sizing, gas flows, filler materials, etc.Another good source is Weldingtipsandtricks.com.  The moderator has a common sense plain english style and he's funny.  Makes it easy to learn.If you can afford $25, I strongly recommend buying "The Procedure Handbook of Arc Welding" published by Lincoln.  It basically covers everything you need to know re arc welding.https://ssl.lincolnelectric.com/linc...dnum=PH&PID=16Miller 211 w/ spool gunMiller Dynasty 200DXLongevity 60i IGBT plasmaO/A w/ crappy chinese torch/gaugesSouth Bend 10K latheGrizzly 4029 10x54 millGrizzly 7x12 hor bandsawangle grnders, bench grnder, bench belt sndr7.5 hp 80gal cmprsor
Reply:You could also use some type of integrated backing ring (like a piece of 18 gauge stock rolled and tacked to the ID)  Instead of doing a purge. I agree .120 wall seems very thick. It won't be possible in a single pass and ideally you would want a slight bevel.  Stainless welds up easy but has lower penetration than carbon steels.Anyways that's my advice, on exhaust I would just use a piece of sheet rolled to make a backing.
Reply:well i appriciate all the comments i did double check today my mild steal pipe that i am currently running is 1/16 thick so that would change lot of variables its been a while since ive looked at it