Advice on dealing with TIG starts and stops on tubular joints

admin

Guys,Thanks to everyone who provided advice in my prior threads.  Some of the advice is working but I still have a long way to go.One area I am still having trouble with is my starting and stopping.  Do you guys have some advice on how to approach the starts and stops.  Hopefully Zank or Zappy will give me some tips.Also please provide any feedback you think I need based on these photos.I am doing the joint in short sections.As you can see I have some visual inconsistency with the "tie in" that needs to occur when the section segments meet up.As always thanks for the help you guys have been giving me.
Reply:What size is this tubing?  Your bead looks really stacked, like puddle isn't moving far enough between filler dipping.  I can't tell though if it's just an illusion.  HAZ looks wide, but again, what size tubing and machine settings? Originally Posted by SundownIIIDon't get me wrong.  They are just as ill informed about politics as they are about welding, they just post more on that subject.
Reply:There's significant undercut in the red circled area.Controlling that, comes before nice tie-ins.http://weldingweb.com/attachment.php...1&d=1326077150 Attached ImagesBlackbird
Reply:Holy crap!  Is that what is happening there?  I hate using this tablet sometimes.  It jams this stuff up so much that I can't hardly tell what I'm looking at. Originally Posted by SundownIIIDon't get me wrong.  They are just as ill informed about politics as they are about welding, they just post more on that subject.
Reply:Tubing is 1.5" for the short little tube and about 1.2" for the smaller diameter tube.  Both tubes are 4130 bicycle tubing.The wall thickness for the thin tube is 0.031".  I am using 045 ER 70-S2 wire with a 1/16" ceriated tungsten.  The power comes from a Miller 150STH in pulse mode with the dial set on 65 amps.   Argon is set to 15 cfh.There are about 30 more photos of this joint on my blog:http://febikes.com/2012/01/08/bb-she...at-tube-joint/I think it looks like more undercutting then it actually is.  Sometimes the way the light catches things makes it look more undercut but don't get me wrong I need to work on more consistent bead fill.  For this joint I am walking the arc over the rod and with minimal pushing in.  I think this is what is described as "lay wire" technique.Last edited by febikes; 01-08-2012 at 10:19 PM.
Reply:Last edited by con_fuse9; 01-09-2012 at 06:49 PM.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:I don't see any undercut in the red area... I also think your previous welds were better ( a few months ago), and there's the huge HAZ... then I never welded that alloy so can't really comment about that.try a few cupons with more heat 10-15% and more (weld)speed also--------------------------------------------------------------www.becmotors.nlyup, I quit welding.. joined welder anonymous
Reply:Looks like undercut to me.  Also, looks like the heat is inconsistent (haz larger in some areas than other and beads looking convex in areas and concave in others).--Wintermute"No man's knowledge here can go beyond his experience." - John Lockewww.improvised-engineering.comManufacturer Agnostic:Blood----------Sweat---------Tears----|------------------|----------------|----Lincoln Red, Miller Blue, Esab Yellow
Reply:I would tack it up in four spots, in your alignment jig, then figure some way to set it up on some kind of rotating table, shaft, etc...that you can rotate the work slowly, and not have to move the torch around the work to weld it out...then go back to into your jig to make sure nothing moved.btw, i don't see any undercut, the shadows and lighting just make it appear that way....like magic!!Last edited by DLite; 01-10-2012 at 03:16 PM.
Reply:Hi Mark,Couple of things. What I try to think about while moving around a joint like this is I am moving from an area of a T-joint (the deep sections of the cope) to a lap joint ( the ears or sides of the cope). You don't need as much filler for the lap joint as you do the T-joint. Obviously, as you move, the joint is transitioning from T to lap and back again, so it's never really a true T or lap. But thinking about the "type" of joint I am currently welding while moving around the entire joint helps me gauge how much filler to add. If you are using wire diameter that we typically use on bike frames (0.035 or 0.045), the lay-wire technique may give you enough material on the ears, but it probably won't give you enough filler for the T areas. I use 0.035 wire, and I usually just dab on the ears but push more into the puddle in the T area, especially the acute side. This gets enough filler to prevent undercuts and also helps give the bead an even width and appearance as you transition from the ears to the deep section.Regarding starts and stops...what I strive for is to do the whole joint in 4 sections. It doesn't always work out, but now that I got some reading glasses and can see better, I am getting closer to that goal. What I do on my stops is add a little extra filler on my last weld deposit so that it crowns up a bit. Then I reposition and re-prop to do my next quadrant. I'll light up again where I stopped, watch the puddle form, then start to move just as the puddle is the size of that last weld deposit. The movement draws some of the extra filler I laid down and flattens the stop/start. Then I'll start getting into my rhythm from there. My starts and stops aren't great, but each time they get a little more seamless.Hope this helps. Just some things that have helped me as I've been learning and practicing.
Reply:Thanks everyone!There is lots to think about with this; I will be doing a lot of practice the next few weeks and will aim for four sections with more even fill and a flat bead as discussed in this thread.  I am also working on keeping the arc length consistent as we discussed in an earlier thread.