I went back about six months in the technical forum, and did not see any discussion about welding copper. I have also spent a couple of hours web searching with limited success. My reference books make general statements about welding copper, but not much specific advice.
In my application, appearance is the key. I need to match the color of the copper, especially after it has weathered a bit, seen some moisture, etc. This is steering me away from soldering or brazing, and towards trying to match the base metal as closely as possible.
I am an engineer, but I have been away from the welding field for many years. I will probably be welding this with oxy-acetylene. Some sources say that oxy-acetylene is OK for copper, and some do not. TIG is probably better, but strength is not key for this application.
I understand that the 101 alloy is the oxygen free type, better for welding than the 110 alloy.
My biggest problem right now is trying to figure out what kind of filler metal I should be using. There are many brazing alloys, but I don't think that is what I should use, due to color differences. How can I match the base metal? I was wandering around the ESAB website, offering maybe 10 copper alloys, but it did not disclose much about the metalurgy of the alloys. The ESAB #21 caught my eye, but not much information. I would guess that whatever I would need would be a special order item, not in stock in my local welding shop.
Any good reference material on any aspect of welding copper would be appreciated, paper or web. I will probably pick up a 54 page pamplet that the Copper Development Association publishes about welding and brazing copper.
Thanks in advance.
Richard Ferguson
One way I have matched copper filler is to shear a piece off of the material to be welded and use it for filler. I have also welded it autogenously in a lap joint. I use GTAW. Doesn't copper react to acetylene? It also requires high heat input, possibly preheat, good restraint and lots of tack welds. I know there may be a lot of different ways to weld copper, but this is how I have done it. Hope this helps.
Respectfully,
Mike Sherman
Shermans Welding
I am not sure what sort of sections you are looking at, but if it is rather thick you will struggle with any process that is not capable of very high heat flux. I suggest using the GMAW (MIG/MAG)process.
Regarding the colour matching, you need to know exactly the composition of your alloy. Is it pure Cu or an alloy? If it is cast, it is probably an alloy. Try getting a matching filler metal.
I hope this helps.
Regards
Niekie Jooste
I would like to clarify that I am talking about relatively thin copper, probably 20 gauge (less than 1.5 mm).
Richard Ferguson
If you have ever tried to weld thin guage aluminum with oxy-fuel, you will have similar issues with copper. Heat control is really critical. If you don't keep things under control your base metal will go where gravity takes it in an instant. You really need a filler with a lower melting temp than the base metal, more than likely the color will be different, I strongly recommend TIG welding. The post referring to using the base metal to make filler strips is an exellent idea.
I have had good success with using copper wire that is found in Romex cable, like what you wire your house with. You should test on a small area to see if the color match is what you need. You also should be able to find filler rod from one of the manufacturers, try Filler Metals Inc.
Best of luck, Brad
I want to know process for Cu/Cu diffusion bonding, will you help me?
Diffusion bonding, or diffusion welding (DFW) is a solid state welding process. This means that it happens without the materials actually being melted. The surfaces to be welded are machined to be in very intimate contact. These surfaces are then placed under pressure and heated to a relatively high temperature while keeping the pressure for a certain time period. The diffusion of the atoms accross the planes seperating the materials results in the ellimination of this seperation plane. The result being that the materials are welded together.
DFW is a very specialized process usually only used in the aerospace, nuclear and electronics industries. I personally have never seen it in practice. I have only read about it in literature.
This process is only of use under certain situations, and uses very expensive equipment. My AWS handbook gives the cost of the equipment as a function of the area to be welded. It is $2000 - $4000 per square inch. (It may be higher by now because this book appears to have been written in 1987.)
Do you want to know anything else?
Regards
Niekie Jooste
Dear Niekie Jooste,
Thank you for your reply.I know DFW is a very complicated bonding process requiring expensive equipments,but I really need this process for my research. I want to bonding two pieces of Cu which is about 0.25mm thick and etched many grooves for cooling. So, DFW is a must for my work, will you help me find some process parameter?such as temperature, pressure, environment(vacuum or inert gas ),interlayer etc. Thanks
As I mentioned in my previous post, I have no practical experience with this process. As Such, I would have to search for the necessary information just as any other "novice".
My suggestion to you would be to first try to locate suitable equipment to perform this weld. As previously mentioned, the right place to start would be in the aerospace or nuclear industry. Once you have located the equipment, you will probably have located the best people to tell you how to operate it at the same time. (The people who own the equipment.)
Sorry I can't give you better information.
Regards
Niekie
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