Cracked tig weld on aluminum Help

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I am making a box for a fellow out of 1/4 5053. The side was made out of two pieces and to be but welded together, I left a 1/16 gap and felt that was enough. I started about 1 inch out and then went back to the inside corner and as I was welding it up to the start weld it split. I am using 4043 rod 3/32 dia 250 amps pulsed at 1.5 pps and 35% on time. What is going on?? I am not a novice but this is the first time that this has happened to me (except for 6061 Duh) What am I missing?? Could it be as simple as not enough gap or V?? I have been successful with the mig on the long runs but that is another problem for another thread.Thanks I think that I will go out and see if I can cut this out and have a beer.There is a big tack weld that is on the outer edge out of sight in the picture. Attached ImagesLast edited by Lucky Eddie; 06-30-2009 at 05:15 PM.Wilmington, NC
Reply:I'd quit pulsing and use different filler. I bet 4043 filler isn't recommended for 5053 material. Can't find 5053 base material in european filler tables though, I bet it's AlMg2,5 but not sure, so I'd use 5183 or 5356 filler.
Reply:5053??? do you mean 5052?If so probem is you didnt tack it together. Real common. Good heavy tack every couple inches for that material. Then start your weld about a 1/4 " from a tack and weld away from it, the tack keeps the weld from "pulling appart" so to speak. 4043 is an OK filler, Id rather use 5356 myself as its got higher ductility.
Reply:Yes 5052The weld is 6 inches long with one heavy tack on the end. I think that without a proper V the weld was not heavy enough to withstand the expansion. I am now cutting a V into it and off to try it again.I hope that 4043 filler is ok cause I used 4043 mig wire to put the rest of it together and a friend built a boat out of the same combination with a MIG.I really like 316 SSWilmington, NC
Reply:Originally Posted by Lucky EddieYes 5052The weld is 6 inches long with one heavy tack on the end. I think that without a proper V the weld was not heavy enough to withstand the expansion. I am now cutting a V into it and off to try it again.I hope that 4043 filler is ok cause I used 4043 mig wire to put the rest of it together and a friend built a boat out of the same combination with a MIG.I really like 316 SS
Reply:Originally Posted by makoman1860Tacks on the ends arent the same as tacks in the middle. for a 6" weld I would have about 4 tacks. Weld from the middle out. Figured those others were mig welds, just cant get away from the manure spreader look of tig on aluminum ( no offense, just they way the process looks ). Good Luck!
Reply:Eddie,Not trying to be critical, but from the photos, it appears technique/consistency, is as much a culprit here as anything else.Here's a couple suggestions for welding that up with the Sync 250:Turn the pulser OFF.Aluminum likes to be run hot and fast (Tig or Mig)Tack first, about every 1 1/2".  Aluminum "shrinks" about 6% when going from a liquid to a solid state.Get rid of those craters.  Leaving a crater like that is like saying "OK crack, here's a nice crater for you to start in".  Add additional filler at the end of the bead as you back off on the amps.Practice to get your beads a little more "consistent".Personally, I wouldn't gap it at all.  With the proper heat, you won't have a problem with full penetration.  Maybe a slight edge bevel on each piece where they butt.As has already been mentioned, I'd use 5356 vs 4043 for this application.Just for $hit and giggles, try butt welding a couple pieces of 1/4" scrap at 225A, no pulse.  Move fast.  Play with your amp setting to find that Amp/Speed that works best for you.Seeing you're from the Wilmington area, have you ever run into a guy named Eddie Keith.  Ed used to run Quality Welding back in the late 80's-early 90's.  Did most of the tower fab for Carolina Yacht Sales (Bertram dealers)there on Atlee Rd in Wrightsville Beach.  One of the best aluminum welders I've seen.  His dad ran a large SS tank fabrication company there in town.  Built a lot of the SS Tractor Trailer tank rigs.  If Ed's still around, he could square you away in half a heartbeat.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:I know that you are right about the crater but this split while I was welding it. Stress from expansion. I cut the weld out and put in a V then it went together without problem.  This is the largest and thickest project that I have undertaken, I have made tanks and fixtures from aluminum before but only out of ,093 where the force is not as great. I have not run across a Eddie Keith but the Gore family owns a T top shop and they will help. They run SW250 machines like mine but they use a on off switch to pulse their welds. They also do not clean the anodise off of the aluminum tube that they use but make pretty and strong welds non the less. I was using the pulsar to keep from getting out my thumb control..Oh well today is a better day so far and thanks for your advice.RobertWilmington, NC
Reply:Actually Eddie, the cracking is from contraction as the material cools. You will see it from time to time, you can't just pull aluminum together like steel and stick it, it likes to retract quickly. If shrinkage cracking is a problem, preheat the general area a bit, and/ or try a heat blanket around it. Also, heat sinks under your weld will help hold the heat to minimize the rapid shrinking and resultant cracks.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:Originally Posted by RojodiabloActually Eddie, the cracking is from contraction as the material cools. You will see it from time to time, you can't just pull aluminum together like steel and stick it, it likes to retract quickly. If shrinkage cracking is a problem, preheat the general area a bit, and/ or try a heat blanket around it. Also, heat sinks under your weld will help hold the heat to minimize the rapid shrinking and resultant cracks.
Reply:I run an Invertec 205 also. The pulse feature is great, that's not much of an issue. I usually don't use it, I just work my pedal a lot. For a really long run, I will use it from time to time. I just find it easier to modulate with the footpedal. I find 4043 filler cracks a LOT. I am not much of a fan of it. If you use 5356, you'll get less cracking. I use 4043 on thinner stuff, but not that often.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:Preheat is a major culprit here. The surrounding metal is sucking out the heat too fast.It is in essence a "quench" effect. Just like crater cracking at the end of a weld, the rate of contraction is too fast. The pulse is compounding this issue. Pour the heat into it, after some mild preheat.If you have a sync 250, turn the balance higher numerically to gain penetration also.Good luck, this is the single greatest thing about little mishaps, the learning process.We've all been there.
Reply:Originally Posted by revhardPreheat is a major culprit here. The surrounding metal is sucking out the heat too fast.It is in essence a "quench" effect. Just like crater cracking at the end of a weld, the rate of contraction is too fast. The pulse is compounding this issue. Pour the heat into it, after some mild preheat.If you have a sync 250, turn the balance higher numerically to gain penetration also.Good luck, this is the single greatest thing about little mishaps, the learning process.We've all been there.
Reply:Nice work. I need to get into water stuff. I'm just breaking into aircraft now. Seems nobody believes you are any good unless you charge an arm and a leg. A learning curve for me.I have alot of advanced certifications, but it's all in who you know.That job looks cool, something to be proud of for sure!
Reply:Originally Posted by revhardNice work. I need to get into water stuff. I'm just breaking into aircraft now. Seems nobody believes you are any good unless you charge an arm and a leg. A learning curve for me.I have alot of advanced certifications, but it's all in who you know.That job looks cool, something to be proud of for sure!