Welding Tips and Tricks

I have a job to weld two 1.5 inch thick copper plates together. The plates are 8 inches long, it is a butt joint with a double bevel. I am welding this for a UT inspection test plate for a University. The instructor wants me to use silicon bronze for a filler. I was questioning whether to use AC or DC. I weld small copper up to .250 thick with DC and silicon bronze, but for this application with all the passes I have to do and this is supposed to be flawless if I should use AC and maybe even deoxidized copper filler? Helium for sure.
Give me some ideas please. I will use 1/8 inch thoriated Wolfram tungsten, and a Dyn 280 DX. Thanks for you help!

Nobody????

Why would you use ac? You may need just a touch of ac like maybe 10% electrode positive if you were using aluminum bronze but not with silicone bronze. Besides, you can't weld as hot with ac as you can with dc and copper requires a ton of heat. Why would you weld it with oxygen free copper if you were asked specifically to weld it with silicon bronze? Besides, it's a fairly safe bet that you're working with some type of copper alloy and there is a very specific reason why you were asked to use silicon bronze.

You didn't give the full dimensions of the plates either. How wide, long and thick are they? If they're 1.5" thick then you're likely gonna need to preheat them a bit with a torch first. It's not a weld, it's a braze and that silicone bronze has a fairly low melting point but it also has a ton of copper in it so if you dilly dally around and let it cool between passes then you might have to preheat it again. I've never tried to do any build up with it so I'm not sure how it behaves once you start laying a really thick bead. I only use it for decorative stuff.

You may not have received a reply because A) your question is a bit vague and B) there's not a whole lot of this kind of stuff going on around here. I haven't seen anyone ask this kind of question since I've been on this forum. I've never welded any copper either but I know that it's some really mean shit from watching the old boss use it as a heat sink and from watching Jody use it for the same purpose in his videos.

Maybe someone else will have some better advice for you now that I've opened the door a bit. Sometimes shit be like that.

Ok...I'll bite...I have played around welding copper. It puddles and welds pretty normally but.... True de-oxygenated copper rods are more expensive than gold. Now the bad news...Your machine probably doesn't have enough ass to heat 1.5" copper enough to get a "flawless" weld or a braze, even with a double bevel. You need HUGE amperage to get an immediate puddle on copper otherwise you just wait for the metal to get hot enough to puddle or you can pre-heat it but by the time you get it hot enough you will have a dark orange glowing mass with strips of black oxidation peeling off of it....good luck trying to weld it then. This is my opinion only. Others may disagree but I messed around with it enough to know it's a pain in the ass because of its conductive qualities. You may have better luck with brazing but you still need to get it hot so you are pouring in heat while it is wicking it away until the whole piece gets too hot to work with. Using AC for silicon bronze makes for a nice shiny and really pretty weld but you can almost accomplish the same on DC. I would love to see pics of this if you pull it off. I am not trying to put you down, I am just pointing out the problems you are likely to encounter. Your post is kind of vague in description so if you could post up some pics that might help. Welding copper is in a class all by itself for a reason but good luck and post up some pics.

Yup I know. Deox copper is pricey I have it for small jobs. The exact dimensions are 1.5 inches thick, 5.5 inches in length and the width of the weld is 6 inches. Total of 11 inches in length when welded. So I came up with a plan,,,,please criticize. I have fire bricks to lay the to pieces on to save heat, I will of course get it hotter than a three dollar pistol with a torch, I will use Helium as a gas, I will use a 1/8 lanthenated tungsten with a 1 inch gas lens (16). I will put my little 280 Dx wide open with a foot peddle, I will use silicon bronze DC.

That being said the goal is to make a weld that UT students should not find any flaws. The next piece I weld, I actually have to put flaws in.

That next piece?

I can help you with that one for sure.



Kym

I don't think youre gonna be able to tig this thing up. You'll likely have to resort to oxy-acetylene and flux. Maybe I'm wrong but I just can't see this happening with a tig torch. I tried to tell a buddy of mine about this kind of stuff a few years back and he didn't believe me. So he asks my old boss about it and the boss gives him a hood to strap on. The old boss cranks his machine all the way up at 320A and takes a 2" round bar of copper that's six inches long and lays the beans to it for about 30 seconds. It didn't do shit to that copper other than soot it up.
I'm definitely interested in seeing your results. This ought to be good no matter if it's pass or fail. Who knows, maybe it won't take so much amperage since it's only a braze and not a weld. Please post pics.
Is this a school project or a job for a school?

I think you will be ok. It's not like your trying to weld it out in just a few passes. Something that thick will take 30-50 passes. To pass a UT test it just has to have no voids of trapped inclusions. So I'd brush it clean between each pass.

Exotic metals wrote:Yup I know. Deox copper is pricey I have it for small jobs. The exact dimensions are 1.5 inches thick, 5.5 inches in length and the width of the weld is 6 inches. Total of 11 inches in length when welded. So I came up with a plan,,,,please criticize. I have fire bricks to lay the to pieces on to save heat, I will of course get it hotter than a three dollar pistol with a torch, I will use Helium as a gas, I will use a 1/8 lanthenated tungsten with a 1 inch gas lens (16). I will put my little 280 Dx wide open with a foot peddle, I will use silicon bronze DC.

That being said the goal is to make a weld that UT students should not find any flaws. The next piece I weld, I actually have to put flaws in.

That is a viable plan. Maybe you can lay fire brick on top of the metal for some thing to shield you from the heat. Make sure you post pics. I definitely want to see this finished.

No this is not a school project but a job for a UT school (class)... I will post picks for sure and will have all details noted. Don't hold your breath,,those pieces of copper are sitting in my kitchen mocking me at the moment I am thinking next week.

Exotic metals wrote:those pieces of copper are sitting in my kitchen mocking me at the moment

I feel them mocking us all!