[landcj01]

Hello, this is my first post after I have been watching many videos and learning alot about the tig welding process. I am trying out a new application that has me stumped and I wanted to see if anyone has any insight into my issue. First I'll explain that I am trying a different way to weld 0.04" copper foil to a 0.5" thick copper bar. I have a method that works but I am trying to figure out a new way that gives me some advantages. First I'll explain my setup and what is working for me.
Miller Dynasty 700
2% Lathinated 5/32 dia (sharped point with a blunt tip)
75/25 Helium/Argon mix
Pulsing at 1.5 pulse per second, Pulse low side at 60% of set amperage, pulse peak time 75%
No filler rod, just fusing the 2 materials together


Here is a picture of the prepping the parts that results in a good weld for me.

weld prep.jpg (68.79 KiB) Viewed 1716 times

Here is the what the finished weld looks like (I am cheating by the way with a buggo traverse, so I can't claim any skills).

good weld.jpg (23.32 KiB) Viewed 1716 times

In my application I need to attach multiple bars along a length of foil and I really need to figure out how to weld the foil to the bar without cutting it. I thought I would try and run a bead across the top of the foil that is on top of the bar. I start my arc on just the bar and get a good hot puddle going which gets the bar nice and warm before I get over to the foil (this is like using the welder to pre-heat the bar and get it hot in the weld area). The foil defiantly melts back right away compared to the foil but I can get a nice big puddle going and the pulsing really helps push the puddle out to blend in with the foil. Here is what it looked like. I can't figure out why the weld turns black (clean both pieces very well). I am running a very high amperage to get the large copper bar on the bottom side hot enough (around 500 amps at that pulse setting). It almost seems like I am overheating the foil material and could that be causing it to turn black? Is there contamination even though I cleaned with SS wire brush and ethol alcohol?

new style.jpg (40.91 KiB) Viewed 1716 times

Here is a picture of where I broke the weld to test it. It is very brittle and breaks easily. Notice the shinny copper at the break

break 1.jpg (20.09 KiB) Viewed 1716 times

Notice this break doesn't have any shinny copper at the breaking point.

break 2.jpg (17.67 KiB) Viewed 1716 times

Anyone have any thoughts on why the weld turns so black and is so brittle? Any thought are much appreciated!!!

[Arno]

First thing to do may be to get some sort of trailing argon shield like on titanium going to try to stop oxygen from oxidising the hot copper as it emerges from under the cup. That's likely the source of the blackening.

As to it going brittle/hard.. Perhaps the oxidation plays a role, but I assume your copper may actually be an alloy and various ones of these can be hardened.

Eg: http://www.totalmateria.com/Article71.htm

Bye, Arno.

[Coldman]

First thing I would try is loose the helium and go with straight argon. I think you might be overheating the foil with helium. The rest is puddling on the bar and washing over to the foil using whatever method works best- pulsing etc. I find a fast circular motion with the arc helps the puddle run on copper sometimes.

[Poland308]

The black is definantly oxidation. I wonder if a product like solar flux would help? When you braze copper with oxy/acy you use flux to keep it from oxydizing. Don't think bost brazing fluxes will handle the temps of a weld but I've never checked.

[exnailpounder]

I have played around welding copper before and it is like nothing else you will ever weld. The black is severe oxidation due to superheating the thinner metal. When you weld copper you need to use de-oxygenated copper filler so you don't get the brittleness you are seeing in that thin material. That thin material isn't de-oygenated and is overheating and basically breaking down. Welding copper isn't very common and there are reasons for that. You would think it would weld easily but that is not the case. You have the huge amperage you need to get the copper to puddle but you need de-oxygenated filler material to make it bond. My 2cts.

[Sandow]

I don't think that welding strategy would work well on most normal metals and copper is screwy. If you need a continuous weld, you are probably much better off with a 1/16 gap in the foil and then using the bar as the backing strap. You can get some solid core oxygen free wire and strip the sheath off to use as filler. If you don't need a continuous weld, just punch some 1/4" holes and do rosette welds.

I think your set up and the helium are good fwiw. Getting enough heat in quickly enough to melt anything without soaking the part would be hard otherwise.

-Sandow

[Markus]

1. Always use filler wire that contains deoxidizers
2. Preheat thick parts
3. Argon-Helium mix works well on copper

Take a minute or two and have a look at this http://www.twi-global.com/technical-kno ... art-1-111/

[Kevin_Holbrook]

try spot welding with a roller

[ajlskater1]

This is a very cool post! I have never welded copper but I would love to learn. Will be following this post closely. Hopefully someone has some advise that helps you out!

[landcj01]

Wow thats for all the thoughts and ideas! I have tried a few things and wanted to share my results.

First, this is a pure copper (no alloying elements).
I did trying going straight argon on a flushed joint (what produced a good weld for me in the pictures above). On thicker materials I think I can see how first hand the helium is key to be able to melt thicker pieces. The picture below was 1/4" copper). The left side was with helium mix and the right was pure argon. With pure argon I was never able to get a stable tig puddle to form and copper BB's would just blow around (was quite intersting to see) and did not give me good results.

20160610_092925.jpg (35.86 KiB) Viewed 1534 times

Whilte I don't have de-oxogenated filler rod, I did have some copper wire that is the same alloy as my bars and foil. I tried to keep my heat down as much as I could but was hard to do as it takes the heat to melt into the thick bar. The picture below shows how the welds arn't as black this time around. The biggest challenge at this point was not having a good way to hold down the foil to the bar and as soon as the heat gets to the foil it lifts up away from the bar. As soon as the foil lifts up away from the bar is when the foil tends to cut through. I had a small section that started to look good on one side with the filler. I am going to work on a way to hold down the foil better and get some better orientation out of my torch and see what happens then.

20160610_140537.jpg (44.56 KiB) Viewed 1534 times

I think the biggest thing I have leared at this point is I have to be careful with the heat and this thin foil. If I get it too hot I cook the foil and this black oxide. Using filler allows me to blend the two mateirals better and not just rely and blasting a huge puddle and violently pulse to stir everything together.

I like the connection of this weld much better than the the brittle ones above that broke in some places as they cooled. This cut away is from the better looking part of the weld above. You can really see how the foil lifted away from the bar. Now I am going to see if I can clamp the foil to the bar and get a good weld on both sides of the weld puddle.

20160613_090355.jpg (34.06 KiB) Viewed 1534 times

I agree with the comments about this not being a good strategy with any kind of material. This is much harder than simply welding on the ends. But I think this may be possible with filler rod and a better clamping method. I will share the results of my next test.

Thanks everyone for your input!!

[landcj01]

I got a chance to lay a couple beads yesterday and I can say that I got the two pieces to bond with a strong weld thats not brittle and can be folded many times and not show any signs of breaking at the weld joint.

First thing, I found I needed to clamp the foil down fairly close on both sides of my weld so the heat didn't lift the foil up and away from my bar.

The next thing is heat is key like has been mentioned by other posts. I thought I was pre-heating the bar enough, but found out when I laid two beads on one bar the second bead turned out really nice which was beacause the bar was nice and hot. Becasue I didn't have the bar pre-heated enough I had to crank up the amperage to try and get things to puddle together. This time I was around When I cranked up the amerage I got the entire piece and weld way to hot and it make the weld joint very brittle and it easily broke. I still struggled with the filler rod on this weld (this is the first time I have ever used filler rod and I have some more learning to do).

20160613_155656.jpg (57.73 KiB) Viewed 1135 times

The big black spot is where I ran out of bar on the bottom side and just burned through the foil : )