Help with TIG welding stainless.

admin

I'm trying to TIG some stainless pipe for an exhaust and it seems that my welds are contaminated after I'm done.  They look all black and nasty.  Not like the pictures and products I've seen.  It seems to weld OK just looks like crap when in cools.  I can hit it with scotch brite and it looks better but not what I expected.  I'm using pure Argon, The red tipped Tungsten and ER308L filler rod.  The pipe says 304 stainless.  I've tried turning the gas flow up and down but no help.Any help would be great. Attached Images
Reply:Do you have any scrap you can practice on?Is the metal clean when you weld it?How many amps are you using?Do you have a pedal on your TIG?If you do, don't mash the pedal so that you get a puddle immediately. When you weld it, get it just hot enough to melt it.From your description it sounds like you are getting it too hot.Yup
Reply:Burnit, I have tried on all sorts of scrap, it all looks the same.  I wipe the metal with some brake cleaner.  I have a pedal and the miller 185 is set at about a 115 amps and I have the pedal about half way down when I'm welding.  Its seems to flow nice.  I can even weld the gaps with no filler rod but am using some for strength.  It just seems that I'm missing something basic, or have the wrong rod or something.
Reply:brake cleaner may leave a film most of us use acetone also clean the inside of your tubing but would agree your too hot ..what does the inside look like ? is there sugaring on the inside
Reply:What is surging?  I cannot clean the inside of the pipe since it is about 12 feet long with about 9 joints.  Here is what I found this morning. If I stick the tungsten inside the cup so that it only protrude 1/16 inch and use no filler rod the weld looks perfect. I have tried cleaning the filler rod and it helps a little.  You can see little crusties coming out of the weld when you use the rod.  I read that there is another type of cup that diffuses the gas better.  I have the regulator set at about 20 psi.  Jon T
Reply:Burnit is getting you on track.... black for stainless is and indication of too hot or insufficient gas coverage or maybe even both. What is the thickness of the tube? What dia. wire? Gas flow? Torch angle? Joint design and poor fit-up can kill you before you start. Make sure your tungsten is CLEAN and sharp, one dip and it's over. Try going back to your practice pieces on a much lower amerage setting and just run some (tiny) beads without wire. Pay attention to your torch angle, square is the best place to start. Stop and check your bead for colors, size and penetration after each inch. Find out what too little (amperage) is first, then work your way up. Quench your work after each bead or use multiple coupons so that each time you begin your metal is cool enough to touch. You were right that you're missing something basic, 9 times out of 10 that's what all welding problems are. I'm just trying to give you a way to break it all down to one fundamental at a time, find out what it is, then build back up to where you're getting desired results. Hope this helps...maniak
Reply:(I read that there is another type of cup that diffuses the gas better. I have the regulator set at about 20 psi..)its called a gas lense, lets you get into tight spots a bit better, but not a cure for correct procedure,lotsa practice...practice, practice...I try every day to practice tigging something different
Reply:Here is what I found.  Tungsten sticking out to far, turned gas up to 35 and I'm dirty.   I cannot clean the inside of the pipes now but with a clean area the weld has a nice gold clean look to it.  I will try to post a picture later.Thanks for the help.  I will be around more, I like this site.If anybody ever needs any car help please ask.Jon TLast edited by Jtroiano; 05-13-2009 at 01:57 PM.Reason: spelling
Reply:Higher gas flow can cause turbulence and contamination of the shield with air.
Reply:From my limited SS Tigging My method isLong sharp taper on the tungstenmake sure tungsten and metal is cleanLet the tungsten protrude from cup the thickness of the tungstenfor 1/4" and 1/8" I set my tig to 140 amps max No pulseWhile welding my amperage is around 70-85, once I get puddle I back it off and keep it at that rate unless it cools, just a tad more than it take to melt my filler which is 3/32" 304 rods usually, it does not take that much filler with the SS welding I do just enough to keep my bead going, and I am no expert but do have to weld alot of SS items, piping and brackets, but as others said black iand nasty is to hot back her down some
Reply:Back purging the pipe with argon will help the gas issues...
Reply:Here is the latest quality.  It seems that the filler rod makes it a little dirty also.  In the center, I used no rod and it looks the best.  I used scott brite on the rod and then wiped it with acetone. Attached Images
Reply:Jtro...,What I see there is someone who's just learning how to tig weld.  First and foremost, you're trying to tig weld stainless tube when it appears you haven't mastered torch movement and the addition of filler.Not trying to be a smart a$$, but you'd be better off working on your technique with some coupons in the flat position before you tackle tube.  No consistency in the torch movement to coincide with the addition of filler.  Severe undercut in places.  Pulled the torch away before the weld cooled (see the holes in the bead).  Went for stretches where you didn't add filler.  Couple of spots you added filler when the puddle wasn't hot enough to melt it.  Angle of the torch kept changing therefore the bead width kept changing. ETC, ETC.Don't try to put the cart before the horse.  Get proficient doing "in position" tig welds before you tackle tube/pipe.  Things will go a lot easier.You're better off setting your machine at about 10% higher than the amps you need (not twice as high).  That way you have better control of the amps.  Pedal movement is relative to the total amps dialed into the machine.  Less amps dialed in, finer amp adjustment with the pedal.  Use your filler to help control the puddle.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Sundown,  I agree.  I have a heck of a time being steady..  It was a practice piece.  I purposely didn't use filler in the middle just to see.  When I welded the actual good pipe I put it in the vise and welded a little and then rotated it.  I defenetly need practice.  I try to rest my hand on the work.. Do some people rest the cup on the work?Jon
Reply:If you get your fitup spot on you won't need filler so the weld just got easier.  To get the weld so it has good penetration set to around 55-60 amps and this is on the warm side, in fact set it to around 50amps (throw pedal away) , it's just more to confuse you.  Light up and hold the torch in one spot, sooner or later the weld pool will 'pop' and the little black dot in the middle will start spinning, once that happens you can start moving but make sure that dot keeps spinning, if it stops then your traveling to fast and are not getting good penetration.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:Originally Posted by JtroianoSundown, I agree.
Reply:Thanks for the ideas.  If I dont use filler, will the weld be strong enough?I like the gas pedal.  I can lay a nice bead on aluminum, it seems more predictable.Thanks again.  I will keep practicing.  I only use it about once a month.Jon T