Brazing or welding thick copper?

I will be making a gate for the entrance to a house and will need to join some thick copper rectangular bar. The 0.5" x 1" 110 copper bar is
for the gate frame and the infill of the gate will mostly be .5" x .5" square copper rod.
I've successfully fabricated copper grillworks for other gates using my Thermal Arc 185TSW. The grillworks were a mix .75" x .1875" flat bar and .1875" round bar and I've been very pleased with how the Thermal Arc works on copper.
However, I made some copper hinges out of .1875" x 2" sheet and found that my 185 amp welder is at the very limit of what it can do.
So knowing that my Thermal Arc won't be anywhere near able to handle the .5" x 1" bar, I was wondering what would be the best way to make the gate frame?
I have an O/A welding setup with #2 and #3 tips (and a 175 CuFt Acetylene tank) and was considering pre-heating the metal until it was red before trying to tig it. I guess another person holding the O/A torch would be useful?. But even preheating it, I'm afraid that won't be enough and I doubt I could get close with the tig torch to that much red hot copper.
I've been experimenting with tig brazing 3/16" copper using silicon bronze and haven't had very much luck. The bronze has been balling up -- I didn't have that problem when tig brazing steel.
So would it be best to mitre the joints on the thick bar stock to a 45 degree angle and braze it using O/A? Will my O/A setup be enough to braze copper this thick? Using coarse thread screws seems problematic since I doubt soft copper would hold screws well.
Thanks for any insight. (Yes, I was a fool for getting copper this thick, but that is what the homeowner wanted and I couldn't find square copper tubing).
-Aaron
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Make that a 75 CuFt acetylene tank... Only reason I mention this is that I'm not sure I can use a #3 or higher tip with that small of a tank.
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You might want to look into MAPP or Propylene. It is a LOT cheaper than Acetylene. It is sold in moderate-pressure bottles filled with liquid. So, you get many times more fuel in the same size cylinder, due to the liquid and the lack of packing needed to keep acetylene safe. It works great for brazing.
Jon
snipped-for-privacy@gmail.com wrote:

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Interesting question. I will be following this one because it seems impossible. My vision shows forging end cap T's onto the copper.

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On 20 Oct 2005 14:01:56 -0700, snipped-for-privacy@gmail.com wrote:

It might be possible with the TIG if you can insulate and preheat enough but copper is such a good conductor of heat that it wouldn't be easy.
As for brazing it's definitely possible if you use the right filler rod. If this is really copper (and not brass or bronze) then I'd recommend using Sil-fos, Sil-flux or any of the other trade names for the 90-95% copper, 5-10%silver, and trace amounts of phosphorus for fluxing rods. Refrigeration contractors use this rod for joining copper tubing and it's great for that job. No flux is needed do to the phosphorus in the rod.
Wayne Cook Shamrock, TX http://members.dslextreme.com/users/waynecook/index.htm
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Hello Wayne,
Thanks for the suggestions. I really am using 100% copper (Alloy 110).
I already figured out the insulating bit when I made the hinges. When I was welding the hinges on the metal table, I couldn't get a puddle. When I put the hinge in a little cave of fire bricks, I was able to get a puddle.
I can try welding two 1' sections of the bar. However, considering that copper seems to just suck up the heat, I'm not sure it would be a good test considering that I'll actually be joining a 4' length to a 6' length.
I like the end cap idea, but not sure how I would fabricate those. I can always screw on gussetts to the bottom since there will be a copper panel on the lower portion of the gate that would hide the gussets. However, gussets on top would be ugly.
When/if I finish this, is this the kind of thing people would like to see in the drop box?
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On 20 Oct 2005 15:30:16 -0700, " snipped-for-privacy@gmail.com"

I'm no expert, but there was once a time when I had to weld copper. It was 3/4" thick, 4" wide, and a little over 2 feet long. No way could I weld it with a 300 amp tig torch. I called the welder who usually did our fancy stuff and he said a good pre-heat would do it. So, using fire bricks I was able to fill in the 1/2" deep 1" wide goof in the part using copper wire as filler. It seems to me that after heating the bar I covered it with fire brick. I for rested my hand on it while welding. Even with the preheat I think it took at least 250 amps. And I may have been using helium. We used helium for some aluminum jobs and ran the torch DC. The metal had to be real clean but boy, could you really lay in the rod. Eric
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wrote:

Seems a little odd to me that nobody has asked why you are doing this. I'm not a history buff, but I'm sure the bronze age was a long time ago and the copper age was earlier.
Today copper is a lot less available than other metals like steel. Why not ask how to coat some steel item with a thick coat of copper? Maybe the stupid waste of materials and disregard for strength is the point of your work.
Sorry. Just my opinion after reading what you are up to vs what I would be inclined to do.
Other than that -- traditionally copper gets soldered. I guess the whole point here is excess, though. I don't really mean that in a bad way, just a comment on what you are up to.
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Xray, you don't have anything constructive to say, so why bother posting? Why is it material I use to make a gate? The customer likes they way aged copper looks. And if you bothered to google for copper gates, you would find that there are plenty of gates made out of copper.
By the way, the total cost of copper was $400. I just finished a wooden gate that cost the same amount in materials. Do you go and complain about people making furniture out of walnut? Or do you believe everything should be made out of MDF? And as to coating steel with copper, do you have any great ideas on how to do that in a small shop?
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Well, it's usenet, just killfile the people who aren't worth reading. There'll always be more, but no reason to not keep the signal:noise ratio as good as you can.
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wrote:

True enough. My bad.
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In article <1129847416.285947.302270

I'll second Wayne's recommendation of phos/copper brazing. It's relatively inexpensive and a pretty good color match for pure copper. I've brazed heavier (though not as long) sections of copper bus bar than what you're looking at using oxy-propane.
Ned Simmons
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On 20 Oct 2005 15:30:16 -0700, " snipped-for-privacy@gmail.com"

Your 185 amp TIG might be a bit light for the task at hand. But don't get in a hurry with preheat. Even insulated, it'll "suck up the heat" until you have all of the copper within some distance hot -- which will be never if it isn't insulated.
Bulk thermal conductivity of copper is 5X that of steel. Resistance is resistivity * length / area so a bar of given length and cross section will have 1/25th the thermal resistance of a same-size bar of steel. (I missed that first go, Jon). That suggests (as Jon did) that you'll need to insulate for some length, perhaps the whole bar. If sufficiently insulated, then the conductivity doesn't matter. With heat input, the bar will continue to rise in temperature until heat loss rate = heat input rate. If you insulate for enough length, then *once preheated* it shouldn't be appreciably different than welding a same-size bar of steel -- perhaps easier, given the lower melting temp. Once adjacent copper is hot, its ability to "suck heat" is limited. However, it may take a while to pour enough heat in to get the part of the bar inside the blanket hot enough to proceed with welding.
The foregoing assumes that the insulation contains heat considerably better (25 times better) than a bar exposed to free air. I don't know if that's a reasonable assumption for an inch or two of ceramic blanket, but it might be worth a try. As said before, I'd preheat with O/A or oxypropane (lower temp but more heat) so as not to run into the dutycycle limit of your welder.

By all means, please do!
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Don Foreman wrote:

This has been bothering me since we started this discussion. I have this image in my head of Aaron K. getting this thing half built, and it is going slower and slower as the pieces are assembled. Finally he gets to a point where he's going to need every Oxy/Acetylene torch in the entire county all at once to do the preheating! The only other alternative is to do the entire job while sitting inside a furnace! That's what furnace brazing is for.
Maybe I'm overstating the heat loss problems here, I don't have a clear idea how many cross members there are. If this thing is a square frame with vertical bars, and no other members, maybe it can be built, but it may not support its own weight. If this is for a person to pass through, that may not be much of a concern. If it is to span a driveway, I really have doubts. Either way, if it has a few more horizontal bars of the .5 x 1" size across the middle of the gate, it is going to get messy as the joints are brazed and the number of heat paths increase.
Jon
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On Fri, 21 Oct 2005 17:18:11 -0500, Jon Elson

I agree, if the whole thing were made of heavy stock like that it would eventually become a humongous radiator. I had the (perhaps erronious) impression that most of the stock would be considerably smaller, just the outer frame was the heavy stuff.
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I'm beginning to think I got in way over my head on this one. The gate was supposed to look something like this:
     +--------------------------+      | |      | | |      | | |      | | | | |      |     | | | |      | | | | | | |      | | | | | | |      | | | | | | | | |      | | | | | | | | |      | | | | | | | | |      | | | | | | | | |      | | | | | | | | |      +--+--+---+---+---+---+--+-+      |**************************|      |**************************|      |**************************|      |**************************|      +--------------------------+
with the bottom portion a copper panel attached with brass rivets. So there would be three horizontal members and two verticals. The spikes in the center are .5"x.5".
As far as sagging, I figured if the bottom panel was tightly attached, it would add some rigidity to the gate.
I could use the copper for some other projects. I'm thinking now that this project just isn't going to work with the tools I have.
Thanks for all of the insight and help.
-Aaron
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snipped-for-privacy@gmail.com wrote:

Well, I wouldn't give up without at least a test. You say the sheets will be riveted on. No brazing there at all? Then you'd definitely want to put that on LAST. So, you are going to have the spikes unsupported for most of their length? Some delinquents might be able to bend them and make a total mess of the thing. I guess once the copper work hardens in the weather, that might be real hard to do, though. I think a person could do that in the annealed state.
So, these spikes are welded just into the middle crossmember? Or do they pass through into the bottom horizontal? If the former, I think maybe you could assemble the spikes to the crossmember, build the square frame, and then you only have two difficult joints to do. Those might be possible to do with sufficient heat sources and insulating blankets. Anyway, you ought to try preheating and then TIG welding a sample of the material. If it seems a breeze, you might try to push ahead with it. If the simple test proves a very difficult job, then you know that it is going to get worse as the parts are assembled.
Keep us informed, some info on what turns up is always useful when trying to advise on unusual projects like this.
Jon
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wrote:

Yeah, I'm curious too. If I had some chunks of copper I'd have tried it -- have the blanket and TIG, but no copper.
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I would not give up without thinking about it a little more. I know you have the design already done and approved, but do the spikes have to be square?
I am thinking 1/2 inch copper pipe with 1/2 inch steel rod inside for the spikes. And a pointy copper arrow head added to the top afterwards. If it really has to be square, then make a tapered steel piece and pull it through either 1/2 or 3/4 copper pipe. Obviously this will take some experimentation. But I think it could be done. Start with copper pipe that is longer than you need and braze on at one end something to hold it. Use 1/4 inch steel cable and a come-a-long to do the pulling. You may have to make several square tapered steel pieces of increasing size and anneal the copper pipe after each pass. And of course use lube. I can see you now doing this between two trees.
If you can make square copper tubing, then you can use two of them brazed together ( or welded ) to make your 1/2 by 1 rectangular bit. Or if you can use rounded pieces then two copper pipes side by side or spaced so the " spikes can fit between.
Whitman college in Walla Walla, WA has some gates made of copper pipe that are attractive. As I remember they are of quite a bit bigger pipe and so probably don't have the steel inside.
Dan
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" snipped-for-privacy@krl.org" wrote: ...

...

...
I think pulling the pipe through two sets of rollers (one set vertical, one set horizontal) would work better than using the interior square mandrels you suggest.
I don't have a good size chart handy for copper pipe, but imagine that 1/2" type M copper pipe is 0.625" OD and 0.569" ID. So the inner periphery would be 1.788", and the outer 1.963", which would give an inner width of 0.447" and outside width of 0.491". Half-inch rod wouldn't fit inside, but 7/16" would. Or perhaps use 4 sets of rollers angled at 45 degree intervals, and roll an octagonal shape with .5" steel rod already inside.
-jiw
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