T-joint TIG Q's

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I'm TIG welding some tubing for a control arm but I'm running into kind of a snag. I'm using this little project as a means to improve my round tube TIG welds. I'm very satifiied with my TIG capabilities on a flat surface but I seem to turn retarded when it comes to round tubing. Following the profile of the tubing seems to be a bit of a problem for me. So I'm looking for feedback as how some of you more seasoned guys in the tubing area would set something like this up.I have an 1.5"x.120x1-3/8" piece of tubing at the end of a 1.25"x.120 at a T-joint:I've been welding quite a few ends for practice and I had one run that turned out pretty well but I don't have the coveted dime roll bead.Here's the worst of my litter so far:The undercut there seems very hard to avoid on something like this. I keep the heat up and throttle the pedal to try and compensate but this more so goes back to my ability to follow the profile of the tubing. Most of the undercut is coming from the torch not being perpendicular to the tube surface. I weld the piece with the joint towards me and the 1.25" pointing away and elevated so I can see the weld area better. I rotate the tubing around as necessary obviously. If you look at the first pic, the illustration, I basically try to weld from the outside towards the middle of the pic. I angle the piece in such a way it's almost a straight line in a way. But it's easier said than done for me.I have the machine set at 80 amps and using a 1/16" thoriated tungsten. On that particular piece pictured I was using an 1/8" copper coated ER70S filler wire. I was using 3/32" filler prior to that run. I've noticed the weld bead looks better if I move faster and use the higher end of my pedal to compensate for the speed. This is why I switch to 1/8" filler on it. By no means is it good looking but you can see it was beading up.But primarily I'm looking for advice all around like any suggestions for setup and positioning. I don't believe the undercut is a huge deal as it seems to be the nature of the beast but figure I get some feedback from you guys.Last edited by Kubs; 02-21-2010 at 11:48 PM.Miller Syncrowave 180SDMillermatic 175
Reply:while that weld isn't perfect it sure isn't going to fall apart either. getting your wrist to roll around the tube just takes practice, you are on the right track just give it some time. a couple of suggestions though. 1/16 tungsten is a waste of money for most people. 3/32 is fine for damn near everything, I use it welding tubing down to .020 and don't have any issues. I also think 1/8 filler is a little big for that and 3/32 or maybe even 1/16 would be better. they will flow much more easily and won't cool the puddle as much as the big wire. you can also give it a couple of pushes and wait until the bead looks full before you move on. the last thing I will suggest is try stacking your dips closer together. for me it always seems like the closer I space my additions of filler the better my beads will look.
Reply:Hello Kubs, to add a bit to what you've already been told, using a smaller tungsten may only make a difference when you are operating at really low amps(arc stabilization issues), the 3/32" tungsten will work perfectly fine for your given application and will likely help with tungsten life as well. When you are considering filler wire size you should also consider that a specific filler wire size will generally require a specific minimum heat setting to allow for an even melt into the puddle, meaning, if you are using an oversized filler wire you will need too much heat to get it to melt properly for a particular base metal thickness, instead you will possibly overheat the base metal and cause undo penetration and burn-through in order to keep an even flow of the filler on the surface. Reducing the heat to prevent overheating the base metal while using an oversized filler might cause sticking of the filler rod or a rough uneven surface appearance of your bead. You mentioned torch angle, yes, being able to keep the torch angle the same as you progress around the joint will help with consistency and evenness of the bead, keeping your arc length as tight as possible will also aid in minimizing undercut, especially when you are welding on steel. Practice, practice, practice is really the key, your welds look pretty good, with more practice you will likely become much more pleased with your results.      If you are welding bosses on the ends of tubes such as your picture shows you could additionally help yourself by providing a heat-sink in the I.D. of the boss. The boss is small and heats up rather quickly compared to the pipe that is intersecting it. By providing a heat sink in the boss you will have much better control where the two parts intersect and be less likely to experience undercut issues. This heat-sink could be made from copper or possibly aluminum, doesn't need to be really tight but shouldn't necessarily be a clanger either. Using a piece that is about the same diameter as the boss and machining a step in it that is just slightly under the I.D. of the boss would be helpful, especially if you are making a weld right near the end of the boss where it meets the mouth of the cope on the other tube. Hope that makes sense. A bit more for your consideration. Best regards, Allanaevald
Reply:quasi is right, that's a sound looking weld. You could probably sand the undercut at the edge down if it's a concern.  Or even go back and add a dab of filler. Looks like you welded it in quarter turns, that's what I would've done. You could probably use a little more build up on the sides, they look a little concave.As for the stack of dimes look, practice, practice, practice, as always. Took welding several hundred couplings and bosses for me to get the stack of dimes look around a tube down pat.
Reply:I appreciate the comments guys. Thanks!Quasi, I'll try filling it more before continuing.Aevald,I hope to get some sort of heat sink or backer for this as I use this particular size fairly often.Grimm, I think we have the same idea. I do try to weld the thing in quarter sections.I should correct myself here from what I originally stated in my first post. I mistakenly said 3/32" and 1/8" filler. In actuality its 1/16" and 3/32" that I use. So for what its worth...As far as using the 1/16th tungsten. I had a similar project awhile back where I was making control arms. However instead of using round tubing I was using rectangular tubing. The problem I had with 3/32" is the same undercutting issue. I found using the 1/16" mitigated it and just became accustomed to it. I can step up the electrode no problem.I took some pics of my better piece. This one I used the 1/16th electrode and 1/16th filler.I should also inquire about what I should expect in regards to penetration, something else I'm tackling here as well. I bevel the ends down to the meat of the tubing to help with penetration. Like so:I've tried a multitude of angles. The one in my first post was a 30*. The one in my 2nd set of pics and the one picture above is a 15* bevel.This is the penetration I got with this last piece pictured:Normally I wouldn't be asking about penetration but due to the complexity of this type of weld I'm not sure what to expect. They type of weld joint is constantly changing as you weld around the tubing.I have some more material awaiting prep work to be welded and I'm going to go at it again using some of this insight. I appreciate it guys!(sorry about the big pics)Last edited by Kubs; 02-22-2010 at 04:46 PM.Miller Syncrowave 180SDMillermatic 175
Reply:if you're experiencing under-cut, put your wire where the undercut occurs.. and if you can, leave some tube on the ends before you weld and cut off after you weld.. i personally walk the cup around those kinda welds.. and i hold the tig torch upside-down too.. always use a 3/32 for your first pass.. 1/8 is too big and won't flow, and 1/16 will run away from ya'.. and yeah.. switch to a larger size tungsten and you won't have to sharpen so much..if you're not livin on the edge, you're takin up too much room..
Reply:hell.. those picture there looked pretty good to me..if you're not livin on the edge, you're takin up too much room..
Reply:The welds look fine.  I think if you make a smaller bead the undercut will go away.  Under cut is operator controlled, not near as much due to heat or tungsten size.  I would use 3/32 tungsten and 3/32 filler.When welding the joint, stick the filler, don't dab it.  More filler in the joint will take care of the undercut.Are you moving the torch in a circle?  That could also be causing the undercut.  Straight  movement following the groove pointed directly in the center with a forward angle should be all you need.Your welds are fine, appearance will get better with time.I don't worry about the vaulted stack of dimes.  Just get good penetration and a smooth weld.  As  you get more seat time, it will look better.A positioner would solve some of your problemsDavid Real world weldin.  When I grow up I want to be a tig weldor.
Reply:All the above advice is great also try to get as comfy as you can and break it down into maybe 4-6 sections and when you get around to the outside where you are getting under just like dave said feed it or concentrate the heat on the bottom pipe and wash the weld upCigweld Transmig 265seBoc 140amp StickBoss 200amp AC/DC TIGLincoln Electric Invertec V260-S
Reply:the joint looks on the under filled side, if you add more rod it will help with the under cut. Also as mentioned undercut in this situation has more to do with torch control that machine settings.   On Tee joints, you generally can't get away with just aiming right at the root and get no penetration.on Tee joints I usually dab the filler closer to the outside edges rather than try to put it all in the middle of the puddle.  Also you have to rotate your torch angle towards the toes on each zig. The filler will follow the heat and torch angle If you just move your torch back and forth without rotating it out towards the edge you'll generally find undercut, especially on the vertical leg of the joint.
Reply:Looks like you got it to me but you can go slower and concentrate on keeping things more "Even"...Since they are bench parts get as comfortable as you can with your arms...Do a "Dry Run" to see if you can get as far with the torch as you would like in one pass...Not saying that you did but..Never start and stop in the middle of the mouth on the joining piece...Thats not good.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:i think a heat sink would cause you more harm than good. .120 wall is pretty thick stuff and unless the ID is critical it will just be one more thing to heat up and create a greater risk for undercut.
Reply:I think that by chamfering the tube you're making this weld far more difficult than it needs to be, nothing wrong with that if you're trying to hone your skills, but IMO really isn't necessary for your application (or many others, for that matter).  Personally, I would use a kind of variation of the "walking the cup" method for this weld (doing it 1/4 at a time if it wasn't in a fixed position), not because I can't do it freehand, but because it's by far the easiest way to follow the profile of the tube.The undercut could be due to many things, but I would say it's most likely because you're not adding enough filler.Last edited by Baila La Pinza; 02-23-2010 at 01:49 PM.
Reply:Originally Posted by KubsI'm TIG welding some tubing for a control arm but I'm running into kind of a snag. I'm using this little project as a means to improve my round tube TIG welds. I'm very satifiied with my TIG capabilities on a flat surface but I seem to turn retarded when it comes to round tubing. Following the profile of the tubing seems to be a bit of a problem for me. So I'm looking for feedback as how some of you more seasoned guys in the tubing area would set something like this up.
Reply:I had some time today, so I found a piece of .122" tube and cut it.  I fit it on the bench grinder, so you can see it was not perfect, but close enough.  Set the machine at 120 amps and only used it to start the bead.  After that I used less.  1/16" ER70S-6 filler with 3/32 tungsten of unknown type.  It wasn't green (pure).  I only pointed the tungsten directly in the groove.  No side to side or forward and back motion.  Just add filler when the puddle looked ready.  I don't count or anything, I just weld it.  I did this one in 3 passed, then I did another one in 4 passes.  Each one I started on the side as low as I could go and went up hill, around the top.  I have a positioner but didn't use it.  There was no undercutting anywhere.  As far as the stinkin dimes, mine looks no better than yours.  I just weld stuff.  I got no rhythm.The first one I did I used a whole length of filler, the second one I used about 2/3 of the 1/16" filler.  David Last edited by David R; 02-23-2010 at 04:55 PM.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Kubs, your welds look sound to me. Only problem I can see besides lack of rythm (it will come with time) is some of your starts and stops. Just make sure you over lap your stops a little better. I'm used to pressure vessel work, and that would be a pottential leak.
Reply:I don't know about making a bunch of dimes, but when welding tubing i roll my wrist and a joint the size you are working on would probably take 3 or 4 repostions to get all around it.  The sample (unless you cut it in a band saw for examination) has greater mass on one side so to minimize the undercut i would angle my tig to favor that side, if you simply go down the seam you'll have to use greater heat to form the puddle and that'll pull metal from the short side and that could be where the undercut comes from.Try not to let the tig get 'ahead of you' either, if it is out there too far when you roll the wrist to go around the corner you'll lose focus on the heat and a greater area will get preheat, you'll lose your pattern (it'll look kinda buttery).  Not as big a deal on .134 wall but when you get to .058 or so it'll matter.  Your welds look ok to me, i'm just passing on what i've learned.  Good luck, ojWhen doing tubing it is good habit to make a gas relief hole, not necessary in your practice samples but i am just mentioning it in the odd chance you weren't aware of them.Last edited by ojh; 02-26-2010 at 10:02 AM.Reason: Afterthought
Reply:Little updateGetting the hang of it90 AMPs3/32 tungsten3/32 fillerWhat I did differently was the dressing of the materials. As Baila La Pinzar (and I think maybe someone else too) suggested instead of beveling the end of the tubing I just ground it down till I was at the meat of the material. It seemed a bit easier to weld. As far as the sides went I concentrated more of the heat on the main tube. I was surprised how much heat I could put into it without fear of blowing through the end piece. I filled it accordingly when I saw the end piece liquifying.Miller Syncrowave 180SDMillermatic 175
Reply:This one looks way overheated - the base metal should not show anywhere near that much coloring or dulling from the weld.  The weld itself should be brighter, too.  It almost looks like a long arc length or moving too slow for some other reason.  You don't need the whole end of the tube liquidifying.This isn't the most uniform; but shows how everything should still be shiny after welding: http://tubularfab.com/gal2/main.php?g2_itemId=1684
Reply:Looking better there Kubs. More uniform than the first pics. Doesn't look like you're having any undercut issues from what I can see. Still think you could overlap the starts and stops better. TubularFab is right, your weld is a little grey. Don't let that bother you to much, yet. I bet it's because you were probably running slower to control your weld better. As you practice you'll pick up speed and hopefully the grey will go away. The grey (non-shiny) look of your weld can be an indication of over heating (moving to slow). This can affect the grain structure of the metal, which can mean potential problems down the road (brittle material, stress fractures, etc.) So while you're practicing it's not a problem, your building muscle memory skills. But hopefully you'll have nice shiny welds (at least less grey any way) on your finished parts. Like the color of the welds in the first pics.
Reply:Kubs, see two pics below. It appears that there are cratercracks (or heat cracking)  in the 2 red circled areas. Crater cracks occur when the arc is stopped abruptly, instead of fading the arc out gradually.These may or may not show as indications in particle inspection-regardlessthey stand out in visual inspection.I'm mentioning this, since control arms are a rather critical, high stress application.http://weldingweb.com/attachment.php...1&d=1267673639http://weldingweb.com/attachment.php...1&d=1267673598 Attached ImagesBlackbird
Reply:Good notes on the cracking and overheating. I'll take it into consideration on my next trial. Bit warmer today so I can have a bit more fun in the garage. I really appreciate the feedback guys. Originally Posted by dave powelsonI'm mentioning this, since control arms are a rather critical, high stress application.