TIG: Thin copper issues

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Hi,I am new to Tig, and trying to butt weld thin copper, around 20-22 ga. I Have a Dynasty DX, am using silicon Bronze rod, and a 1/16 pointed electrode.I have tried plain DC and pulsed. Is there any trick to keeping the butt edges from rapidly heating and pulling away from the edge before I get a chance to feed a puddle with the rod? I have tried various head sink backgrounds like aluminum block. I have tried creeping up on a melting temp very slowly, which doesnt seem to work. I have tried warming away from the edge and moving in, but as soon as I get close, it draws away from the edge.Any advice would be appreciated.thanksdan
Reply:You're on the right track with pulsing, but I bet you parameters could use some adjustment. Try this:Amps: 200A (vary with pedal, but you will probably use all of them)Peak: 1-5%Background: 1-5%PPS: .3 - .7The idea is for a very hot, fast pulse.  The low PPS gives it time to cool between peaks, background just enough to keep the arc established.  You should position the filler so that it gets consumed and pushed into the weld bead during the peak time, don't let it drag behind.That has worked great for me welding 28ga to 18ga 304 SS.Have we all gone mad?
Reply:Hey zargnut,Have you tried to weld with copper filler? Are you using a backing? Copper is not difficult & you can easily use plain 'ol solid copper wire as it is deoxidized. Probably for that thin, I'd try some 16 or 18ga solid copper wire. It welds beautifully. Here's a repair I did a while back.http://weldingweb.com/vbb/showthread.php?t=51268DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:For very thin metal, I have had better luck with higher pulse frequencies(120 - 200 Hz), background current about 33%, and duty cycle about 33%. I don't have a Dynasty so I'm not sure how that translates to your machine.When starting the weld, lay the wire very close to the arc so the arc melts the wire along with the base metal. Keep the wire as close as possible but make sure you are getting fusion and not just "blobbing" the filler metal on.I don't know what your application is, but keep in mind that silicon bronze has much lower thermal and electrical conductivity than pure copper. If conductivity is important, use deoxidized copper filler. It'll give you better color match, too.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Thanks. I will try these methods.I have noticed that when I do lay the rod nearby, it does blob up, and by the time it melts, the base metal has drawn away, so there is nothing for it to adhere to... I have tried copper wire 14ga, and it works, but the SIBr melts at a lower temp, so I thought it would be easier to use. It is for artistic stuff, so strength is not important.I think I can pulse at 200 and set the background % in time and current... So I will try this as well as the slower pulse to see what works.What are thoughts on heat sinks? What about starting at an edge vs starting 10mm in and backing out to edge with rapid filler feeding to prevent burn back?Is this really hard, or am I just being an impatient newbie? It is certainly more challenging than .065 box tube :-)
Reply:What size filler are you using? You mention trying 14g copper wire. That is way to thick. Pick up a small spool of .035 mig silicon bronze wire and try it. I am not a fan of using electrical wire for fill but to try something smaller get some stranded electrical wire and pull it apart. The little wires are probably around .020 or so and if you can work that then you can pick up the silicon bronze mig wire. Copper is tricky cause it sucks the heat away so fast till it gets saturated.Millermatic 252Lincoln 175 plusTA 185tswTA 161stlhypertherm pmax 45Victor torchHenrob torchAn S10 for each day of the week
Reply:Hey zargnut,Using very thin material as you are, I would definitely use a heat sink. Since you indicate "strength is not important", you may want to opt for low-temp silver-solder with O/A instead. It is quite easy to use, flows nicely via capillary action, quite strong(up to 35K) and has enough flex that it can bend a bit. Since color may be important, especially in a judged presentation, copper filler is best. My customer always specifies filler he wants because of aesthetics. Actually, any radii pieces should be already fixed in place using a radiused backing. I have used both methods for a customer who makes artistic taxidermy mounts. Don't get a mindset that TIG is the only option.DennyComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:Can you bend the edges parallel to change the weld joint from butt to edge joint, and just fuse them together?  (fuse weld meaning, autogenous welding, without filler rod?)  The weld shown in picture is a humidifier tray, and welded this way, turned out water tight.  Its copper sheet was somewhere in the neighborhood of.018"-.020" thick; similar it sounds to what you are working with.Based on the tests I've done copper is best welded very "hot and fast" to avoid excessive oxidation.  Without adequate welding power, the heat will quickly spread beyond the inert gas envelope of the tig cup, and cause rapid oxidiation.  So if you want to have the best chance of outrunning the heat, you'll need to use much more current for its thickness than you would with any other materials.  Designing the weld joint to not require filler rod will enable you to travel that much faster (and input less heat into the work, therefore less oxidation.)  AC seems to have no cleaning affect on copper oxidation (like it does with aluminum), so use DC, and also if available, the "super pulse" suggestion earlier in this thread is a great idea (to further reduce heat input and oxidation.)  If you have a helium/argon gas mix at your disposal, consider using that as well. Attached ImagesLast edited by jakeru; 10-08-2011 at 04:36 PM.
Reply:I took a few pieces of copper and tried doing butt welds using both the settings recommended above. The slower pulse blew through the copper with each peak pulse. Did work better with less heat, but I found it hard to control.The faster pulse was easier to control the weld puddle, but it was hard to melt the 1/16 SiBr rod. It kept balling up because I was never able to get a nice puddle. It was either melt back at the edge of the joint or not enough heat to flow the filler.I will try to send pics tomorrow demonstrating my errors.I actually got a Henrob? OA torch. But found it messy, and flux is a pain... If it is feasible, I would rather work on my technique... assuming what I want to do is feasible...
Reply:Originally Posted by zargnutI took a few pieces of copper and tried doing butt welds using both the settings recommended above. The slower pulse blew through the copper with each peak pulse. Did work better with less heat, but I found it hard to control.
Reply:I am back at it... and not doing much better. This was with a dynasty DX Max 150A, pulsed 25% top time, 33% of max base amperage. There is a lack of starting material, and a small gap. I am using .040 SiBronze rod. I was hoping I could get it warm enough to flow, but it doesn't get hot enough to flow the filler before it retracts (blows holes). Given this image with blobs, and blowouts... any recommendation?I can try the 200A, 2% High, 5% base A... but will it matter with no backing and a gap. Is there any way to fill the gap without it retracting?
Reply:I went back and tried welding some lap joints in 16oz copper using combinations 10-60pps5-8% at top 5-10% base amperage200AThey were slightly better, but still pulled away. The butt joint option worked well, but is not really an option in many pieces. Other than using a backer, any other advice?
Reply:Not clear what your goal is here.
Reply:Sorry...For this particular project, I bent a simple box and wanted to weld the corners. There was a small gap between sides at each corner which blew out. Other tests were with sheets of 16oz copper with butt and lap joints...
Reply:Design the filler into the joint.
Reply:So use an overlap as filler? Tight fit-up is always a good idea. I've done some smaller pieces of copper, the whole piece gets red, then the welding starts! Using silver would double your cost, at least.SqWave 200Millermatic 190Airco 200 ACHypertherm PM45Boice-Crane Band SawVictor O/A