Copper Welding

Solder. How big?

I wouln't say solder but rather weld I think and the length initially could be meters upon meters. Later probably into the hundreds of meters as it depends how sucessfull the trial will be.

The size of the copper pipe is @1/2".

Depending on the joint strength and reliability required, solders (generally lead or tin based) are used for lower strength/temperature applications. The next step up in temperature range and strength is brazing (Cu-Zn, Cu-P, silver alloys, gold alloys, and some Ni alloys). Generally brazing will give you strength levels approaching that of welds, and depending on joint design even stronger than welds. Brazing can be done using induction, various gas torches (oxyacetylene being one of the most popular), or even using a GTAW (TIG) torch. Finally, copper alloys in the thickness range of 1mm are commonly welded with GTAW (TIG) or GMAW (MIG) processes.

From your brief description of your problem, I would suggest looking at brazing with Cu-P first. If you do not think this would meet your needs then I would consider GTAW with a filler rod, or GMAW. GTAW is going to give you a smoother looking weld and it will also be cooler. GMAW tends to be hotter and can give you more spatter, but can deposit material quicker.

Hope this helps.

Thanx for the reply.

I was thinking along the line of automation like a roller type mahine that can do a continous spot welding (same as they do with carbon steel like hollow sections and all) I do not know even the name of the process just thinking out loud so you can all guess what I'm on about.

The reason for this is heat transfer.

If the big reason for the welding/joining is heat transfer, I would recommend that you seriously look at brazing rather then welding. It is much easier to get a reliable heat transfer path with brazing.

What process would that be? Is it fast? Just asking cos I never did that sort of thing.

http://www.thefabricator.com/RepairFieldWelding/RepairFieldWelding_Article.cfm?ID=1569

Here is a web link that will tell you about brazing. I do not know how much of this brazing you need to do. A lot of brazing is done with hand torches. However, this could be done with a travelling torch.

One of the biggest issues you may have to deal with is what flux to use and how to clean the flux off after the brazing operation. I believe Handy and Harman has people in London, these would be good people to talk with. Otherwise, Umicore is another company that makes brazing filler material and would be a good source of information.

a lot depends on the gap size and the operating temperature of the final product.

Solder is a lower temperature process and if the joined metals will not melt the solder in operation will give good thermal conductivity. If the pipe will run above the melt point of solder = no go.. In addition, the lower temperatur is easier to handle. Copper has such high thermal conductivity that you get large amounts of expansion when you heat to welding or brazing temperatures as well as join site cooling that requires a high heat inpu to do the job.

Automated TIG process would be best, although it depends very much on where the wire goes. if it is stuck on like fur you could use automated MIG and cut the wire to length then move to next spot. If you are trying to weld one long wire to a piece of pipe, then TIG it. if you are going to coil the wire again TIG but maybe a braze bath might be easier. perhaps you could use thin sheet metal pressings instead like on oil coolers?

Well, when I tried rebuilding soldering tips using 6% SBA, I found that heat transfer was so disrupted(read lower) as useless- so I fusion welded copper wire to the tip using oxy-acetylene(no flux) & no more worries- just manipulate shape to size using hammer on anvil(red heat) then file to shape- much cheaper than buying new- & has better heat transfer than iron plated original- & can be whatever point you require.

I used to work in a solar energy fabrication ship. We soldered brass tubes into copper header pipes. It was pretty bad for the fumes, as we were using liquid flux poured on, and then we would perform 3 passes. There was also a narrow strip of copper in the seam, and so it took all 3 passes on each side (flip table) to complete the seal.

I am curious as to what your application is. If I knew more about it, I could help more.

There is also friction welding. but the choice of methods is really application dependent.

why dont you try with tig welding

Welding copper become difficult due faster rate of heat dissipation. Therefore the process of welding should be the one which provides faster rate of heat in-put than the rate of dissipation. Therefore most suitable welding process becomes Gas-Tungsten-Arc Welding. Soldering is possible where weld strength is of less concern. Automation depends upon the quantity of weld per hour.

Hi,

welding copper is not a good idea as thermal conductivity will require a lot of heat and a high intensity flame.

And shrinkage on cooling will likely distort your parts severely.

Easyest is silver-phosphorous braze (may be copper-phosphor is available now), no flux necessary, the P is acting as deoxidiser.

This is widely used in copper tubing for household heating to industrial heating and cooling circuits. Heating with any "flame" you like gives good results.

Any silver containing braze is wetting much better on brazing so preferred if the prize is not an obstacle. Same with Indium.

Temperature can be as low as 620°C on brazing, welding would require 1100 to 1200°.

Low temperature coolers (copper tubing on stainless steeel containers) we did glue with epoxi that we filled with silicon-carbide.

RHABE

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The replies here seem to be pointing towards brazing which I would tend to agree with as the surface area of the joint should give good heat transfer. The size of your tube means that you could consider using an induction coil for heating instead of flame, this will give a cleaner process.

We regularly braze copper & copper alloys to ceramic or nickel steel & the process works well.

One other thing to note is that, once brazed, the copper will have softened. This can make subsequent machining difficult as the softened material tends to tear however you can restore the original properties by re-heating.

This is a question (may be a silly one too).

Does Ultra-Sonic welding of copper exist or is it more like a dream?

I don't believe that ultrasonic welding of metals is possible, I'm sure that someone will correct me if I'm wrong.

Ultra-sonic welding of metals is possible - but it's a different mechanism than for plastics. For copper, I understand** it to be somewhat akin to a high-pressure (cold) weld, which is a well-tried method for copper; the difficulty is that such a horizontal ultrasonic weld process could become self-limiting (vibration amplitude becomes smaller close to the initial welds), so the conditions could be rather critical.

**I've used pressure welding for vacuum enclosures, but have no experience or knowledge of ultrasonic welding of metals, so what follows the stars could all be wrong (but that's astrology for you)

I think Physicist comfirmed it to me what I saw and was told years ago that Ultrasonic welding is apperantly possible. I was told about it once by a sales person and I wasn't sure of it as I do not normaly trust sales people.

On a small scale I believe solder brazing is good enough but on a larger scale there must be faster and more economical way of doing it.

Thanx all.

If you can use non-annealed drawn pipe and annealed sheeting, you may be able to cold weld the sheet to the pipe. I haven't tried this, so it is possible that the sheet won't weld properly to the pipe. If that is a problem, the edge of the pipe that is to be welded to the sheet could be annealed with a localised reducing flame (the idea would be to keep the majority of the pipe hard enough to maintain its shape). The durability would probably be improved if you were to anneal the assemblies after jointing.

If you can afford high-cost automation (and are far from noise-sensitive neighbours), it could be possible to cold-weld soft copper wire to both surfaces by continuously projecting it into the gap at high speed. If the wire is light compared with the tubing and the sheet, you can use annealed materials for all three components. But the process is highly dependent on the properties of the three copper materials...

If u want a continuous contact betwen the tube & sheet with sufficient strength & good thermal conductivity, Brazing is the proper process.

Due to capillary action brazing will ensure proper joint & since the joint thickness is less (usually 50 microns) conductivity is not affected. It can be easily automated with preplaced filler metals & some braze flux dispensing unit. Again heating temp is less so deformation is less. Cost of process is less with Cu-p as filler metal & oxy-acetylene heating.

Ultrasonics may deform the shape of tube.

It exists.

About 20 years ago I designed a drive system for a copper foil slitting line.

When a new coil came into the line they used a roller excited with ultrasonics and created a very fast fusion weld.

Unfortunately I do not have the details of the welder or its limitations. The foil ran upto about .01" thick. The company processing the copper was Ratcliffes in Toronto Canada.

This is done every day by people who make finned tubing but the attachment is by brazing and it is an oven braze process. Your inquiry isn't clear enough to reply in full but welding of "copper tube" isn't as simple as it seems. First "copper tube" isn't pure copper but an alloy and it is not easy to weld. TIG Braze using sil-fos is a good way and it is reasonably easy to do. Remember when you truly "weld" copper you can punch a hole in it and develop leaks in the tube because welding melts both the parent metals ( tube and fin). Laser welding, electron beam welding are viable options but not cheap. Many respondents suggest brazing or soldering, I have to throw support behind that option. From somone who uses copper finned tubing to make heat exchangers, brazing or even soldering will give adequate heat transfer for a fin on a tube.

Copper may be GTAW welded. See the following link for some discussion of alloys and parameters.

http://www.brazing.com/TechGuide/procedures/copper_welding.asp

The preheat of the part before welding is a very important variable. The preheats listed in this link are not as hot as I remember from when my company did this, but you should start with their recommendations and experiment until you get good welds.

As for automated machines, if you have a joint that resembles a T, with the tube / pipe being the stem and the plate being flat (or roughly so), this resembles a tube to tubesheet joint commonly used in heat exchanger manufacture. Arc Machines Inc. (and others, but we use these) manufacture automatic welding machines. Both fully automatic machines without filler wire and semi-automatic machines that add filler wire are available.

http://www.arcmachines.com/Pages/screen3.html

Automation can be a bit tricky. The joint configuration and fitup has to be very regular and repeatable. Otherwise, you will get a lot of weld defects. Manual welding will compensate for irregular fitup (within reason) because the welder sees the gap between the parts and how the puddle is working. The automatic welder just runs an arc over a proscribed area and it better be configured correctly or else the results won't be correct.

Hi,

To know the answer, please tell the full dimentions of the copper pipe & copper sheet because this is necessary for proper heat transfer.

I would use a 90/10 silver soldier as it would be quicker than TIG process and not generate the fumes associated with melting the copper.

pipewelder

isti80 are you attempting yo weld the tube perpendicular or parallel to the sheet and what is the thickness of the tube is it the same as the pipe?? what is the alloy of copper you are using? copper.0rg has a lot of information and links on welding the many types of copper alloys

touch copper bracing would be ideal for strength and heat transfer . never use any available type of solder alloy due to formation of intermetallic rendering it unrealiable. Heavy Lightning grounding used molten copper to fuses copper wires to copper rods , but that is beyond your requirements for a 1 mm plate and application

Eric See

If you don't need superior strength for pressure, etc the sweat it like a normal pipe ( mapp gas if you are connected to large runs because propane may not be enough heat or just straight up acetylene )

Brazing would be next step up

FWIW I had problems brazing a car radiator during the winter, so resorted to an electric heat gun - the type used for stripping paint. I intended to use it to pre-heat the material, but it produced enough heat to complete the job. Copper radiator, silver rod.

I am assuming you are making solar panels with 1/2" copper tubing, and using the copper sheeting as your collecting face?

I have worked in the industry when it was in its infancy in this country. We made this type of flat plate collector. We used 1/2" hard copper with an aluminum face collector. The aluminum collector was extruded with a 2/3 round on the back side to accept the 1/2" copper which was simply pressed in to position.

We also made a concentrating collector which had a simple lens that concentrated the suns energy like a magnifying lens. The copper tube was 1 1/2" anodized black and slightly flatten to make a larger face for collection. These were programed to follow the sun via two photovoltaic cells set back to back at approximately 45 degrees, a small controller board constantly adjusted via a small reduction motor to move the cells so that equal voltage was coming from each thus keeping the photovoltaic cells, and the concentrating collectors centered on the sun.

When the cells voltage dropped below a given point, the program reversed the motor and moved reverting back to its home position awaiting the sun in the east.

If you want to solder the copper to copper you can set up small production type torched that have double tips and move the parts not the torch.

I am sure there is better technology today, but maybe this will give you some insight into the past processes and some food for thought.

Larry

Thanx SAS you're a smart guy, must be from OZ, and you gussed it right.

I was indeed thinking of building some water heating solar-panels for a place I'm thinking of buying.

Yesterday Physicist comfirmed it to me that Ultrasonic welding of copper is after all possible.

Actually, I was told about this by a sales person when I saw a section of a solar-panel to show how the copper pipe is attached to the copper sheet.

After having read the article about ultrasonic welding I now belive it, and that some sales people can be trusted after all.

On a small scale I believe solder brazing is good enough but on a larger scale there must be faster and more economical way of doing it.

What you have described is amazing how they simply pressed (clipped?) the copper pipe into the aluminium plate. I wonder how they joined these panels to the heads as I am thinking of making the hole setup expandable by adding more panels to it, if it is necessary, and enabling them to track the Sun.

I know it is a slightly ambitious plan but...First I must bring the price down of the property I am wanting to buy, it's my uncle's.

You could swage a channel into your panels with a machine like this.

I think you would get perfectly adequate contact for the amount of heat you are transferring simply by tying the pipe down through holes spaced by the diameter of the pipe. You could use heavy steel wire or heavy fishing line (either way it would need to be in a sleeve - but for different reasons), and tension it up by twisting after tying/crimping.

Hi,

yes ultrasonic welding is possible and stir-welding too.

But both will require heavy investments so if total production will be below 1000m then torch brazing with CuP will be the best and chep and ready to use.

RHABE

Did you figure out how to make this copper joint? If you are still trying to decide, let me know. My company manufactures copper and solder materials.