"Silver solder" questions

[pacifica]

Silver solder with 30-45 % silver,copper zinc and 20% cadmium wets and flows much better than non-cadmium. Don't inhale the fumes.
Harris black stay-silv flux works very well for higher temps, ssbf1.
HVAC pros use a rod that is 15% silver, 5 % phosphous(fluxes) and 80% copper-like sil-sol 15.

 

[benmychree]

Another possibility is SilPhos, it contains 15% silver, I think and copper and phosphorus; it does not require flux on a copper to copper joint, it is used extensively for refrigeration work, as without having to use flux there is no chance of contamination in the closed system, for copper to brass, flux is required.

 

[aliva]

I've silver soldered 1/2" copper pipe with MAPP gas. On a 22mm piece it may not be enough, give it a try. And it was Silver Solder flux coated rod.
Expensive, about 90$ for 10 rods 14" long. I would stick to the proper flux. it's cheap Harris makes a good product.

GSParts Harris Stay-Silv Silver White Brazing Flux Paste for Hi Temperature, SSWF7 - - Amazon.com

GSParts Harris Stay-Silv Silver White Brazing Flux Paste for Hi Temperature, SSWF7 - - Amazon.com

www.amazon.com

 

[graham-xrf]

Oh one thing to keep in mind with copper TIG is that it’s the most current-hungry material (due to the thermal conductivity) so machines quickly run out of oomph as the thickness increases. I only did it briefly as an experiment; my machine is 250A.

That's not such good news.
.. and, if MIG is possible with copper, the same thing would apply.

The 22mm pipe is 22mm OD, and 20mm ID, so apparently about 1mm thick wall. That's about 40 thousandths (0.0394").

 

[graham-xrf]

I have used jewelry silver solder for soldering sterling (.925%), and fine silver (.999%). The solder I used had hard, medium, and easy varieties, hard melting at the highest temperature, then medium, then easy. These were expensive, kind of like sterling expensive, but you don’t need much. I have used propane, acetylene air, and oxy acetylene torches successfully. I used boric acid powder mixed with alcohol as a flux. I also have used white-out or yellow ochre where I didn’t want solder to flow.
I have also joined copper, brass, and occasionally steel with the same materials. I once made a t-handled nut driver by cutting off the plastic handle and silver soldering a steel rod to make the “T” part. Turned out to be an incredibly strong joint.

Thanks for the flux recipe. I do have some boric acid, as well as the tub of borax.
At least some of these are things I can try out.

One thing - I think the decimal place inadvertently got messed in your sterling proportion. I think you meant 92.5% and 99.9%. I can believe it was expensive. That stuff is also called "bullion"!

 

[graham-xrf]

Looking at "How to weld Copper | TIG Time" from weld.com on YouTube..
Apparently, the "secret to success" is 100% Helium at 25--40 CFH.
Helium at 40CFH? - I don't think so!

I don't understand what he means by "Helium has 1.7 x more amperage drive than argon". I suspect he means using Helium works better, but Helium does not, in itself, posses "amperage". Just possibly it might have less ability to carry heat away somehow. In their example, they are using 1/8" thick copper. I suspect I might do better with my 40 thousands. I am going to have to binge-watch YT on copper TIOG before I get the sense of this!

At least I know where I can get copper rod

 

[WaneB]

Thanks for the flux recipe. I do have some boric acid, as well as the tub of borax.
At least some of these are things I can try out.

One thing - I think the decimal place inadvertently got messed in your sterling proportion. I think you meant 92.5% and 99.9%. I can believe it was expensive. That stuff is also called "bullion"!

I should have left out the percentage symbol altogether! I did jewelry fabrication work for 4-5 years, (about 25 years ago). I found it to be an interesting field, but didn’t make much Of an income from it.

 

[graham-xrf]

Regarding what is the difference between "soldering", and "brazing".
Here I exclude all the flux-flowed low temperature soldering, such as is done between electrical connections, plumbing pipes, etc.

As I understand it, soldering is where the filler material flows into an overlap between two pieces of material to be soldered together. The offered metal can even seem to flow up into thin gaps by itself.

Brazing, on the other hand, is where a filler material can be built up on its own, at a junction of materials, just like any other welding, only done at a lower temperature than normally would happen if it were (say) welding steel to steel, or TIG copper to copper.

This begs the question - if "silver soldering" with 55% Ag rod, and either borax, or boric acid type flux. will the metal flow up into the gap?

----
A thing I know about low temperature tin/lead soldered joints on copper. The solder "wets" the copper in a layer of amalgam , where there is a thin tin/lead diffusion into the copper. This amalgam is harder and stronger than either the copper, or the solder by themselves. If the joint is made so close that there is little or none of the pure solder in the gap, just amalgam, the joint is way stronger than one with large dobs of solder in the gap. Anyone who has tried to clean away solder tinning from a copper pipe with wire wool can attest this. I know it from my own experience.

Generally, electrical solder joints should not rely on the solder to make the electrical connection. That is achieved by the cold weld of the wrap on sharp edges, and in various other ways. The solder is only used as a tenacious and durable "glue" to hold the wire terminal joint together. In my case, I could use low temperature tin/lead, or lead free solder. I know that these very high currents in a low temperature soldered joint can actually melt in the joint, and it can fall apart. This especially if it was a poorly cooled crystaline joint solder attempt, also known as a "dry joint".

 

[pontiac428]

Hard soldering behaves very much like soft soldering, with a lot more heat. Flux is nothing fancy, I use the same Ruby Red for both. I would not use the recipe with table salt- why (oh why) would you add a halogen to your melt? That's just a bad plan. I also would give you the strongest warning I can to avoid cadmium at all costs. I won't waste anyone's time here, but look up cadmium poisoning on the web. Personally, I'd rather be tortured with a pair of pliers than have a good hit of cadmium. Warnings aside, hard soldering is easier than welding copper. The result will be more dimensionally true with hard solder. Welding shrinks gaps and leaves an undercut on the edge of the beads, if that's important to you.

As for amperage capacity simplified, just calculate the cross sectional area of your copper and compare it to an ampacity table from the electrical code book. I'm not sure if 40mm dia at 1mm thick will carry 200A, but I'm just guesstimating.

 

[graham-xrf]

@pontiac428 :
Thanks so very much for your contribution. I will not get anything involving cadmium.
I thought the same as you about the salt.
As to the 200A. the pipe is 22mm diameter, I can figure out the power dissipation, but I assure you the copper pipe will carry that current, though it does get warm to the touch.

It has the 6 metres of length in it to dissipate heat,and the resistivity of copper is 16.8E-9 ohm.m
The mean 21mm diameter has circumference near 66m, and at 1mm thick, gives a 65mm2 conductor. That is way more than needed to run 200A.