Copper braze

You can use pure copper. Many furnace-brazed steel parts assembled commercially use pure copper for braze. One famous old example was the Crosley Hot-Shot engine.

When you use copper to join copper, however, you're actually welding, not brazing. I've done it using electrical wire for filler, but that was 30 years ago. You can find information on how to do it around the web. It's tricky but not particularly difficult. Maybe somebody else will have some links for you.

Ed Huntress

try this link

Mark & Shauna wrote:

I was hoping to catch everyone before they replied. I didnt used the best search string in google groups and after I sent the post on page six of my search there it was, hehe just use copper wire for filler as the first reply stated.

Thanks for the info, and sorry to have added an uneeded post.

Mark

Mark & Shauna wrote:

TIG weld them. The trouble with brazing copper parts with copper filler is that the entire thing melts at the same temperature.

If this is being furnace brazed it will wind up as big puddle.

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

IIRC their descriptive name for that engine was COBRA. From COpper BRAzed.

Damn; why the hell can I remember that...but am now sometimes noticing my fly is still open half an hour after I return from the bathroom?

Jeff

You can weld copper with electrical wire, which is what I often do when I need a color match. I was TIG welding copper today. I have done it with oxy-acetylene, I have done it with TIG. Welding copper is trickier than welding steel, and takes more heat. Usually you need a lot of heat to get started, and then less heat after you start to form a puddle, or it will melt through. I think TIG is the best process, easy to reduce the heat input, but I have more experience with oxy-acetylene than TIG, so I tend to prefer the process with which I am more comfortable.

I would warn you that copper welds do not have the quality of the base metal, tend to be brittle. Welding or brazing gets the copper in the area of the weld so hot that it is annealed and very soft, so you need to plan for that.

Richard http://www.fergus>

You can, as you discovered, use copper wire as filler for joining copper parts, but you'll be welding, not brazing. If you want to braze copper parts (i.e., if you don't want to melt the parent metal in the process), you can use a phosphorus-copper (or "phos-copper") rod. It provides a very good color match when joining copper, and responds to patina chemicals about the same as copper. It's not a perfect match, but it's infinitely better than brass brazing material. You should be able to find it at your local welding supply shop.

Bert

Mark & Shauna wrote:

Because that's the way our brains work after we pass a certain age. For example, the bore and stroke of a 1957 Alfa Romeo Guilietta was 74 mm x 74 mm. What I had for breakfast today is an open question.

Ed Huntress

Joining "copper parts with copper filler" isn't brazing; it's welding.

Bert

(clip)My only other option that I can think of is to solder these joints and then use a stained glass patina on them however we were hoping for a joint with more strength than a lead joint.(clip) ^^^^^^^^^^^ This gives me another idea, if welding copper with copper wire makes you uncomfortable. You could braze or silver solder the copper, and then dip the whole thing in a copper sulfate solution. That will put a light copper coating on it. Or, if you want to really do it up first class, have it copper plated. Copper plating is often done under chrome, so it should be a piece of cake to a plating shop.

Thanks to all who responed. I spent a bit of time in the studio today welding some test pieces and it worked out pretty well. They are not quite as clean as I would like but the last couple were more than acceptable to me.

I would like to have the option to TIG them though I dont have the equipment. Every time I go into my welding supply I look at the TIG setup for my Ranger250 but never have the work to justify the expense. I am lucky enough to have a neighbor with an LN-25 that he never uses so its at my disposal but no TIG as of yet.

I am going to pick up some of the phos copper the next time out just for the hell of it but from the first half a dozen welds I think after another few it will be old hat and they will get better each time.

As for the softening, I have been cooling them very slowly and they havent softened much that I can tell but I am keeping an eye on it.

Thanks again to all, Mark

FYI, once you have heated copper to a cherry red or so (and certainly after welding it) it will be fully annealed, no matter how quickly or slowly you cool it. The only way to re-harden it is by working it (forging, planishing, bending, shot-peening, etc.). Whether or not it has adequate strength and hardness in an annealed state will of course depend on your application.

Bert

About the softening, it will depend on what state the copper was in when you started. If it's annealed to begin with, you won't notice any difference. If it's in the condition in which you bought it, which likely would be as-rolled for sheet or as-drawn for wire or rod, it's work-hardened and it will soften a lot if you heat it with a torch or with TIG, and there is nothing you can do to change that, except to work-harden it again. And that isn't usually a practical thing to do.

It doesn't matter if you cool it slowly or if you quench it with water. Copper can't be hardened by heat treatment, and the degree to which you anneal it depends only upon the temperature to which you heat it. Welding will raise it all the way to a completely annealed state, for some distance from the weld.

Good luck. It sounds like you have it under control.

Ed Huntress

Could use brass as normal and dip it in hydrochloric acid to de-zinc the surface layer.

Tim

I don't like the color match of phos-copper rod. It comes out pretty much a silver color when you grind it. If you leave it in the as welded condition, it usually looks OK, dark like the copper. It is easy to use, no flux needed. The Silicon Bronze wire has a closer color match to copper, but requires flux. Brazing is easier than welding, but if you can weld it, however, you are in business.

Richard

Mark & Shauna wrote:

Hmmmmm, good idea Tim. I'm going to experiment a bit..

~Dave