Tig lap joint ?

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I'm struggling with tigging a lap joint on 16 guage steel plate.  Tungsten is 2% thorated sharpened with the tip ground off slightly.  Amperage is at 60.  Plate is ground down with a dedicated wheel to remove all rust and scale.  Argon is set to 20CFH.  Machine is a miller cc/cv350 (? not sure thats right ) with water cooled torch head. Filler is ER80S-D2.   I've adjusted work and travel angles but I just cant seem to get a proper bead down without the leading edge of the top plate receding back into the plate or the leading edge forming one puddle and the lower plate forming another.  Should the electrode be centered over the edge of the top plate with a 10% travel and 90% work angle or should it be over the lower plate or above the edge of the top plate and how far above the plate should the tungsten be for a proper arc?
Reply:Try putting the arc on the bottm plate right next to the top plate. Once you get a puddle formed, manipulate it back and forth slightly until you get one started on the edge of the top plate, and keep working it until the two snap together. as soon as they do, add some filler, let it "wet out" and start moving along. If your having to much trouble getting it started, try a little more heat, then once you do get it started back off the amp-trol a little."SOUTHPAW" A wise person learns from another persons mistakes;A smart person learns from their own mistakes;But, a stupid person.............never learns.
Reply:Tried that and it either splits the bead or the top plate gets eaten away though I think that may have something to do with the plates being warped and a cavity being underneath causing a suck back of the bead.  Heat wise I'm almost wondering if 60 amps is not enough as it seems that it takes a really long time to get the bead to form and to keep it going with the arc gap being around an electrode diameter so I will try increasing the heat to 65 and then 70.  The only time heat seems to be an issue is when I get to the end of the plate at which point I am working on cutting down the heat in time.
Reply:get as short an arc length as you can, concentrate on the plate and let the puddle wash over to the edge ..
Reply:Originally Posted by weldbeadget as short an arc length as you can, concentrate on the plate and let the puddle wash over to the edge ..
Reply:Are you clamped up tight, to be sure the pieces don't move/warp from the heat? A heat sink bar clamped down may help. Also, try hitting it hotter, and fast to get your tacks down. Then, go over it well and fill it in.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:If it's taking so long to get the two to snap together that you're burning through the bottom plate or burning away you're top plate, then definitely try more heat (amps).Last edited by papabear; 12-17-2009 at 11:16 PM.
Reply:What size tungsten?Lincoln precision TIG 275Millermatic 140 MIG
Reply:I'll get pics up today and tung size.
Reply:If at all possible, it will help immensly if the lap joint is clamped and tack welded with tight contact between the sheets.  Clamp or push on the top sheet to close the gap, and zap a tack right there, then repeat every few inches along the joint before trying to weld the joint.  Zero gap is the biggest factor that can help make this easy.  You can weld it with a gap, but as you are seeing, it is difficult and not uniform.
Reply:Things turned out better today, I was able to get the quality of the bead to hit about %90 or so and the last one is at about %97 or so.  The 16 gauge we have to cut from a 5'x5' sheet with a plasma cutter and then grind down the scale and slag and straighten out the edges.  By the end of all this the plates are out of whack so I have been using channel locks to put the plates together for tacks.  Next topic is done and took only an hour though the prep work took an additional 45 mins.  16 and 11 gauge corner joints with and without filler, nailed without filler on 16 gauge on the first try, first try on 11 gauge had undercut to one plate so I went back over it and corrected it very nicely.  Adding filler to the 16g I had to do it twice to get it right and nailed it the first try on the 11g plate.  Pics coming.
Reply:Glad to see you got things worked out. There is no end to the learning.
Reply:Progression pics.  From worst to best with lap joints, I know that its still a bit crude in the last but I think that laps will be my nemesis in the tig world.  The first pic is the machine that I'm using for all phases of welding. Attached ImagesLast edited by Big65mopar; 12-18-2009 at 03:18 PM.
Reply:Second set.  Corner joints with and without filler, I'm struggling with when to add filler but I'm getting better at it and I'm doing good with joints other than lap. Attached ImagesLast edited by Big65mopar; 12-18-2009 at 03:21 PM.
Reply:Her you go.  Attached Imagestig weld - Alibre Design Professional.pdf (61.1 KB, 104 views)
Reply:That's your problem right thereYour welder's all sidewaysyLincoln precision TIG 275Millermatic 140 MIG
Reply:My welder works better upside down! It looks like your arc isnt focused enough either from being to long or improper tungsten prep. Try tapering your tungsten more and using a 20deg travel angle. I like to taperd a 3/32 tungsten back about a 1/4 or more with almost no flat on the tip when i'm doing lower amperage work. I then use that 1/4 taper as my stickout(#8 cup).
Reply:Any reason you are practicing with ER80S-D2? Seems like er-70s2 would be better for practice unless you are welding an alloy steel which I`m guessing you are not since it`s hot rolled??
Reply:Originally Posted by i4sillypwrMy welder works better upside down! It looks like your arc isnt focused enough either from being to long or improper tungsten prep. Try tapering your tungsten more and using a 20deg travel angle. I like to taperd a 3/32 tungsten back about a 1/4 or more with almost no flat on the tip when i'm doing lower amperage work. I then use that 1/4 taper as my stickout(#8 cup).
Reply:Well what size cup are you using? Is it a gas lens?  It could use better gas coverage so maybe a bigger cup or try switching to a gas lens. I use one exclusively if I can access  the joint properly with one.Play with the push angle of the torch until you get prettier colors.  You may try getting some cold rolled steel as well. Hot rolled just TIG`s like garbage a lot of the time anyway even if you take the scale off.
Reply:Originally Posted by BrianNye Welding guyWell what size cup are you using? Is it a gas lens?  It could use better gas coverage so maybe a bigger cup or try switching to a gas lens. I use one exclusively if I can access  the joint properly with one.Play with the push angle of the torch until you get prettier colors.  You may try getting some cold rolled steel as well. Hot rolled just TIG`s like garbage a lot of the time anyway even if you take the scale off.
Reply:Wow those welds look hot. It looks to me like you're either going to slow, have the heat up too high, or are weaving too much. But I'm not there to look over your shoulder while you're working so I could be wrong.
Reply:Have you tried turning the welder around backwards? That might help too.  And I don't know if this helps you any, one of my small welders at home just naturally produces a very harsh arc, lots of penitration. Makes it a pain on 16 guage and smaller. My other welder makes a very smooth arc which is helpful for thin stuff. Their both cheap hobby inverters. I have a similar problem at work. Two miller syncrowave 250, same year model, run like two completely different machines. One runs a beautiful bead, and the other one I have to fight with to get the puddle to flow right with out burning through. See if you can try using a different machine. If the problem persists, then it's you, keep practicing.
Reply:Originally Posted by weldbeadif you grind the scale off hr it tigs ok
Reply:Originally Posted by Grimm1It looks to me like you're either going to slow, have the heat up too high, or are weaving too much. But I'm not there to look over your shoulder while you're working so I could be wrong.Originally Posted by BrianNye Welding guy I`ve been TIG welding sheet metal for quite a few thousand hours too so I`m not a garage hobbyist.
Reply:Ok I'm not sure whether the steel was cold or hot rolled.Cup size I will have to measure tomorrow.Bead looking hot is probable as I have the heat set to 65V ( 5 above the recommended settings for the lap only ) because I was having difficulty in getting the bead to form between the two plates ( 16G ).  I'm aware that it is my lack of experience with tig and with trying to weld on such a thin material however I didn't know that the stuff being pre-cut with a plasma cutter would cause issues with weld quality but that's good to know.  I would use the metal shear but there's a tiny gap that ends up bending the plate at that size.Since this is tig and my heats are low I'm going to change the shade on my shield to #9 and hope that helps me see more clearly so I'm more sure of my angle.  As for trying another machine that's going to be a bit hard and is a long story but to shorten it it comes down to I take care of my booth and equipment while others don't both in my class and others so its part pride and part a principals issue that I'm getting ready to take to the director of education ( same guy that I indirectly called a fool along with the rest of the administrators who failed to close the school during a perfect storm here in November and he found out about it ) to get the issue resolved because I'm tired of cleaning spatter that I didn't make off my tables every morning.
Reply:I stand by the too hot, or too slow theory papabear. Here's what I whipped up in the garage with my scratch start hobby welder. 16 guage, OA cut to warp it some so I would have similar working conditions. Mill scale still on it, 60 amps, 20cfh argon flow, 1/16th tungsten. I know you're new Big65mopar, but you'll get there, keep practicing, your corner welds look great. Cleaned metal would make a better looking weld. You'll notice mine is a little narrower than yours, and you can see the heat marks from the lap weld on the backside. No burn through though. Attached Images
Reply:Oh yeah, filler was 1/16" ER70-S2
Reply:Nice work, especially for scratch start.  No way to slope down, and no burn through at the finish.
Reply:Well again as I have stated before I have had a problem getting a bead to form and to continue on the lap joints.  I'm still not sure what the problem was and I will work with it later on at the end of the mod.  Today was a slacker day and most of us watched movies and I joined in it as I seem to be fighting off a sinus infection and wasn't in the mood to burn.
Reply:Your problem is very perplexing!  I just cant imagine why you're having such difficulty getting those two plates to fuse at 65 amps. Your description of how you're running the weld sounds correct. I know you take pride in taking care of a specific work space and tools, but I really think you should try a different machine, just for a couple of passes at least.Or ask the instructor to run a pass or two. Sometimes watching some one else do it can make a world of difference.
Reply:I've had two different instructors in the booth run beads on 16g lap so its something I'm doing.  Regardless though I did finally get it but not the best.  As for working as a tig welder I don't see that happening due to the lack of tig employment adds around here as compared to mig and stick which are heavy in the paper.
Reply:I didn't get any real work done today because I walked into the booth and both welding tables were covered heavily in spatter, arc strikes, and beads and I made it clear that I was not going to spend another day grinding down a table that someone else should have done when they finished up with their welding.  So I started work on making my own table using tig to join a length of corrugated fence pole to a 12"x16" 11guage plate.  Despite some initial difficulty the pipe welded onto the plate pretty well and I did the foot overhead which was my first time with tig and it came out ok.  Pictures will have to wait till the 4th as school is out.
Reply:Reading through the replies  to your post, I think that you've already got the answers that you need, but anyway, here's my take on it....you're way too hot (you can see by the texture of the bead in your first foto), this could be one(or a combination) of at least 3 things...1, sharpen your tungsten up like a needle, don't even bother putting a flat on it with thin steel2, keep your arc length shorter, you want the point of the tungsten as close to the join as you can (slightly angled towards the bottom plate) without dipping it, 2mm ish would be about perfect.3, turn your amps down a bit, try it on about 55 or maybe a bit less, and see how you get on.Also, with lap joints on thin steel you don't need to weave the arc as you go, rest your hand on the plate and run it in a straight line along the joint, you want the weld to be much thinner, like the foto in one of the replies. Add your filler rod right on the top corner of the top plate, this will help with the under cut, and while we're on the subject of filler IMHO, you'd be better of with 1mm and not 1.6mm. Also, if you are having problems fusing the 2 plates at the start point, if you're adding filler you don't need to wait for them to fuse, once they both start to melt quickly dip a bit of filler in, and then wait slightly before you move on, to ensure good fusion/pen.This is only how I would do it, welding is like handwriting, everyone has their own way of doing it, so don't be afraid to experiment a bit to find out what works best for you.HTH
Reply:Thanks for the tip on the tungsten, I'll regrind that and leave the point.  I've noticed a change in the arc bloom with a longer taper going from an umbrella to a more focused line.
Reply:Originally Posted by Baila La PinzaThis is only how I would do it, welding is like handwriting, everyone has their own way of doing it, so don't be afraid to experiment a bit to find out what works best for you.HTH
Reply:Originally Posted by papabear                                                                                                    weldbead, It looks good from here. And yes, you're right you can get nice clean TIG welds w/hot rolled. Not as easily as cold, but definitely do-able.