Mig welding copper

[Bsmith]

I'm completely new at this so I'll try not to ramble. I'm building a copper sink out of .064 copper and I'm welding (just learning to weld also) it with an old Cebora 200 amp welder, cranked all the way up and wire feed about as fast as it will go I think about 350-400 IPM, using .035 deoxydized copper wire and 100 percent argon at 40CFH. It works 1-1/2" at a time before burn thru, but there is a huge amount of soot covering the weld and about an inch of the metal on either side. There is also lots of splatter at the start of the weld, Is this normal?

[Dr Dean]

Well I've never welded copper before or even thought of it so I'm probably talking out of my backside. On mild steel a 200 amp welder cranked will blow holes in very short order. I would try running somewhere around 50 amps and slow your wire speed to match. You surely have some scraps use them for practice. Good luck and I would like to see some of the welds.

[Thomas Dean]

We used to weld 1/8" copper on a VERY regular basis here but have since shut down the plant where it was used. After much frustration we went to welding with TIG and using a light coating of flux. The flux you need is Bay State #11. You can also weld 316L SS to copper by this same procedure. Buff the area to be welded, lightly flux, weld. Helium is an excellent shield gas for welding thicker copper as it produces a much hotter weld arc but for your application 100% argon is good. If you are set on welding with the MIG process you may want to try to make your welds more down-hill instead of flat. As for the "black soot", buffing the area to be welded may help or you may need to go to a tri-mix shielding gas---something like 92-6-2---argon-CO2-oxy. Like I mentioned before, we found the welds to be much better using the TIG process and flux. I've been at this welding thing since 1973. Good luck!

[Mike Turner]

I have not welded copper with a mig or tig but have welded aluminum, stainless, and steel with both, and the tig just makes a cleaner weld, also less warping. I am sure that it would be just as well on the copper.

[Bsmith]

Originally Posted by Thomas Dean

We used to weld 1/8" copper on a VERY regular basis here but have since shut down the plant where it was used. After much frustration we went to welding with TIG and using a light coating of flux. The flux you need is Bay State #11. You can also weld 316L SS to copper by this same procedure. Buff the area to be welded, lightly flux, weld. Helium is an excellent shield gas for welding thicker copper as it produces a much hotter weld arc but for your application 100% argon is good. If you are set on welding with the MIG process you may want to try to make your welds more down-hill instead of flat. As for the "black soot", buffing the area to be welded may help or you may need to go to a tri-mix shielding gas---something like 92-6-2---argon-CO2-oxy. Like I mentioned before, we found the welds to be much better using the TIG process and flux. I've been at this welding thing since 1973. Good luck!

Thanks a bunch for the info. I would love to TIG it but this a poor boy operation and the old used mig welder is what I have to work with. The welds are fine and penetrate without burn thru if I weld an inch, skip an inch then come back and fill in the skips. The soot doesn't seem to be a problem and you can actually weld right thru it, (you just can't see where you're going) so I wire brush it off, but man it is some ugly welding no matter how you do it.

[Mikek]

its hard to weld thin sheet in one pass, most people when working with the thin stuff put a small weld skip a bit small weld like - - - - - all the way down the weld, work way around repeat process (filling in gaps a little at a time) over and over again until its completly welded, helps with heat buildup and usually looks pretty good
hope this helps

[PBARNHART]

Does anyone have experience using a copper backing plate in this situation?
Would this not help absorb some of the heat..?

[yesteryearforge]

we have some copper heatsinks that we fabricated with water jackets running thru them / cold water is circulated thru the heatsink and keeps it from ever getting too hot.

[Thomas Dean]

PBARNHART, Not sure but I would think that it would work. Just make sure not to have too much penatration as this would fuse your backing plate to your piece you are welding. Possibly if you have say 3/8" or thicker backing plate it would be better, it would draw the heat faster but not get so hot that it would weld to the working piece. Does this make sense?

[cracked]

i'm not sure if i'm too late with this reply, i only just joined up . but any way. do you have to weld it? that is with a mig/tig ( i also recomend tig by the way ,you can get a nice weld) i've spent a few years working as a copper smith, why don't you silver solder it? that would be the easiest, some phos. copper.(low grade silv. sold.the same stuff they use to join copper pipes together) no need for flux if your joining copper to copper and relatively low heat. plus cheap, all you need is an oxy torch. if your worried about strength, remember all your carbide tips are soldered on .might be easier than welding?



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