First Autogenous

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I do not post much but I sure read allot. Thought I would post my first attempt at autogenous stainless tube. I would like to get proficient enough to build a set of headers for my small block 400 and possibly pipes for my old Honda. The first weld was on the left and ofcourse the second on the right. I cleaned part of the second and left the colors on the remainder for reference. 304 ss .065 wall, Diamond Ground TriMix 1/16, #5 cup, 15 Argon, transformer machine at 75 amps, pedal and I set the pulse on the second weld at 10. It seemed to flow a little better. I did use filler for the first weld but only on a short stitch. I guess I need to cut this puppy open to see where I am at. I'll connect a purge soon,. Any comments???I see I missed a spot on the 2nd weld, will have to watch the closer. Attached ImagesLast edited by geezer; 09-14-2012 at 06:15 PM.Reason: Correcting contentGeezerPower Mig 255C185 TIGBlue 175 MIGRanger 8 Kohler 20HP1974 5K Lincoln/Wisconsin Powered (Cherry)Victor/Harris O/AK 487 Spool Gun
Reply:Can you run your pulse up to maybe 100? Use a gas lens if you have one.Other than that, practice, practice, practice.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Originally Posted by shovelonCan you run your pulse up to maybe 100? Use a gas lens if you have one.
Reply:You will never have good results welding thin wall stainless tubing without a proper purge, unless you are looking for a very superficial, shallow penetration weld.  Welded correctly with a proper purge, you won't get the "suck in/sinking" effect you are experiencing.  Don't know what your pulse settings are other than 10 pps, but it is common when doing this kind of thing to run more like 2.5 pps.  Gas lens is essential as well as practice.
Reply:Originally Posted by wijo0131You will never have good results welding thin wall stainless tubing without a proper purge, unless you are looking for a very superficial, shallow penetration weld.  Welded correctly with a proper purge, you won't get the "suck in/sinking" effect you are experiencing.  Don't know what your pulse settings are other than 10 pps, but it is common when doing this kind of thing to run more like 2.5 pps.  Gas lens is essential as well as practice.
Reply:Always, always you want to back purge with autogenous welds on thin wall stainless tube.   I think a lot of the irregular appearance on your welds is due to heavy, uncontrolled sugaring on the backside, and secondly due to "suck back". Purging has the additional benefit as the slight amount of back-pressure supports the weld puddle and prevents suck back. This is how you want autogenous welds on thin tubing to look:http://weldingweb.com/showpost.php?p...5&postcount=19Note that sugaring means loss of alloy content in your beads and unpredictable weld chemistry, I don't have a lot of experience with pulsing. I've never found a need and all my pipe and tubing welding has been with traditional constant current. Also I can't think of any practical benefit with pulsing for autogenous welds- that's just my opinion and other posters my disagree.75 amps would be on the excessive side for non-pulsed. I prefer to slow the hell down and, reduce current and let a very small puddle develop, using as little current as possible. This takes a bit of trial-error to find the lowest current that can be used and still get full penetration.For gasoline exhausts grade 347 is pretty much required, at least for the headers. 304 is good for practice on, and you might get away with using it past the cat converter. But it will develop leaks and cracks in short order if you try and use 304 for the really hot and dirty areas.
Reply:Originally Posted by JoshfromsaltlakeAlways, always you want to back purge with autogenous welds on thin wall stainless tube.   I think a lot of the irregular appearance on your welds is due to heavy, uncontrolled sugaring on the backside, and secondly due to "suck back". Purging has the additional benefit as the slight amount of back-pressure supports the weld puddle and prevents suck back. This is how you want autogenous welds on thin tubing to look:http://weldingweb.com/showpost.php?p...5&postcount=19Note that sugaring means loss of alloy content in your beads and unpredictable weld chemistry, I don't have a lot of experience with pulsing. I've never found a need and all my pipe and tubing welding has been with traditional constant current. Also I can't think of any practical benefit with pulsing for autogenous welds- that's just my opinion and other posters my disagree.75 amps would be on the excessive side for non-pulsed. I prefer to slow the hell down and, reduce current and let a very small puddle develop, using as little current as possible. This takes a bit of trial-error to find the lowest current that can be used and still get full penetration.For gasoline exhausts grade 347 is pretty much required, at least for the headers. 304 is good for practice on, and you might get away with using it past the cat converter. But it will develop leaks and cracks in short order if you try and use 304 for the really hot and dirty areas.
Reply:What are your background and peak settings?  If you want to see what a high quality autogenous weld looks like, just look into high purity/sanitary orbital welding a little bit.  There is a fair bit of literature out there and you can get a good grasp on how to do it manually (which is also commonly done).  Just remember, the behavior of the molten puddle is highly effected by the orientation of the weldment (1g, 3g, 6g, blah blah)Get the pulse settings set correctly, get your purge set correctly, and the only thing left is your technique (hotter than you think, faster than you think).
Reply:Originally Posted by geezerSo the accepted PPS is 2.5pps on .065 304 tube?
Reply:Originally Posted by wijo0131Yes, from what I'm familiar with; high vacuum/high purity plumbing and vessels.  I would normally run around 2.3 pps
Reply:I respectfully disagree that the WIlliam McCormick thread posted above is what you're looking for.I would suggest you read this thread:  http://weldingweb.com/vbb/showthread.php?t=116181for some additional information on fusion welding SS tube.Back purging is essential for a good serviceable outcome.  Pulse, if used, should be low (2-3 PPS) or high (40+PPS) because between 3-40 the pulse is extremely hard on the eyes...Best of luck.Last edited by Mr. Moose; 09-18-2012 at 12:09 PM.
Reply:Did this the other day.No purge.3" diameter, 304 stainless, .065" wall, autogeneous, 2 pps.No sugaring, no suckback, just some "mill scale" discoloring on the backside that came right off with a scotchbrite pad leaving shiney stainless.You can tell by the heat affected zone that it's not a superficial weld, plus I watched it fuse nicely.Last edited by MikeGyver; 09-18-2012 at 09:29 PM.Welding/Fab Pics: www.UtahWeld.com
Reply:When you are learning your PPS will be low, try 1-1.5. Try to match your weave with a pulse, meaning as you are zig-zagging allong, try to get a rhythm where each left movement has a blast, and each right movement has a blast. You could learn to do that by custom ordering your pulse as you see fit, with your foot, and turn off the pulser.  Riding a peddle, keeeping time with a pulser, and managing arc length on small tube is allot to learn at once.Constant Current Weldor.
Reply:Why would you zig zag?It's a single pass autogeneous weld, you want it as narrow as possible and with the least amount of heat input as possible while still getting the job done.Last edited by MikeGyver; 09-18-2012 at 09:45 PM.Welding/Fab Pics: www.UtahWeld.com