Silver Brazeing Rods

[nicknitro]

Hi all,

My company uses Silver Solder 15% for brazeing of copper. Is this an overkill?

What are the advantages of useing this high a silver content solder when you can use say 10%, or 5%.

Is the higher content stiffer? A lot of the brazes are for 1/4 inch plus terminals, upwards of 1" thick terminals connected to 14+ sheets of 0.031 copper sheet.

Also, what types of this scrap be worth refining? Like the grindings, or maybe the stubs of the 1/8 inch rods. I am venturing into a private plateing buisness with this company, and am trying to get some more side buisness from refining as well.

Thanks,
Nick

 

[qst42know]

There are many factors to consider when choosing a brazing alloy.

Flow characteristics, joint strength, types of joints, the ability to form smooth fillets, different metals to be joined, electrical properties, joint appearance, color matching, the temperature required to make the bond, tolerance to less than ideal conditions such as somewhat dirty connections.

Depending on the job a higher or lower silver content may perform better.

I spent 6 years brazing with 45% silver. The extra cost was worth it. Several other alloys were tried but the lower silver alloys just would not flow correctly and could not match the speed of application.

I would guess saving all of this scrap would be worth while over time. But rod stubs can often be stuck to the next rod to be used up.

 

[nicknitro]

Qst2Know,

What was the added value from using 45% silver braze, what was the aplication?

Currently that is how the stubs are dealt with, however they are currntly saved up in a box of hundreds of 1" to 2" stubs that are just as time consumeing to join into a rod.

I have attained a small test sample, which I have inundated with HCL to remove the Tin, however, I believe the rods contain Si as well for filler purposes. This or some other compound seems to shield the rods.

The acid refining process does not seem viable for his type of material unless the materials were ground to a fine powder, and even his option seems taxing as the test materials were hard to cut even with hardened steel cutting tool. They broke most non-hardened steel tools.

I think I shall have to look into smelting procedures for a viable refining process to report to the upper-ups.

Anyone reccommend a good flux process?


Thanks Qst, and all,
Nick

 

[qst42know]

I had to produce water tight seal on 2" diameter thin wall copper tubing one inside the other with a rolled rim. As rolled, the gap varied a great deal. This alloy flowed very well when the gap was close and could fill wide gaps as they came around in the motor driven fixture. This had to be done quickly and at the lowest possible temperature as the components would fail a dielectric test if overheated and the assembly had to be scraped. Flux was supplied in the fuel gas.

Hard cold rolled wire may not be very open to acid treatment. Annealed at a red heat may help.

Or have you tried melting a batch poured into water to form cornflakes?

Or perhaps an electrolytic separation?

Probably the best thing, because you have a line on the source of this alloy you can look up what it contains and develop a plan from there.

 

[butcher]

I have been taking contact points from breakers and switchs etcetera, melting them into impure silver bars with a little bit of 15% silver solder rod,to make impurersilver Anodes, a tall jar, using an old sterling silver braclett, for the cathode, the silver plates out to the cathode, impuritys drop from anode.
as of yet I have just been letting these just mix in the bottom of the jar and using acids to refine the powders.

if anode is bagged or a split cell was used the silver could be seperated with a much purer product,

my intent right now is just to break them down to powders where my acids can remove most of the base metals, and save me on acids,
I can use the silver from this to make back a Higher grade scrap silver to melt to bars and run again through a silver cell , or use to inquart my gold.

to me the silver solder is worth more as silver solder.

I also have used alot of silver solder in my trades,
if I have alot of silver solder in small pieces, I would smoke soot a piece of angle Iron small piece welded on end,for a running mold, set it at an angle over a sooted mold to catch anyting that makes it to the end, sheet rock with pocket carved into it, can also be used,melt the silver solder pieces pour down the angle iron to make large soldering rods or rods for your cell if you plan to electrically refine them, but I would save them to silver braze with.

another idea melt them with the copper powder (dropped from our processes) and flux , to make impure copper anodes, electro- refine the copper using anode bag, or sell the copper bars.

 

[nicknitro]

Thanks again Guys,

I will check into the overall make-up of the rods, I have seen it before, but the newer brand we use doesn't specify.

I totally spaced on shotting Qst2Know, sounds like a good idea, wonder what it will add to the labor tally though. As it stands it will be hard to present a win-win situation to my company with silver prices as they are.

I have researched the silver cell as of yet, what does it use as an electrolyte? Is the anode the material? The cathode I'm guessing is copper?

I have heard a silver cell is kinda costly to set-up from other posts, why?

Thanks,
Nick

 

[butcher]

electrolyte silver (60g/liter)nitrate and water some use a tiny bit copper to start but not needed,anode impure silver usually about 96% pure, cathode usually stainless steel, voltage 3 to 4 volts, PH 2 to 6, electrode spaced about 3 inches, cathode at least 2 times larger than anode, current density abiut 25 to 50 amps per square foot, filter cloth muslin or cotton, container can be glass with cathode plate in bottom stainless steel, with a basket with filter cloth in bottom of it, sitting in electrolyte about 3 inch's from cathode plate silver anode sitting in this basket, anode to positive of power source and cathode to negative, filter catchs impuritys such as base metals gold platinum some silver Etc. I see no reason to spend much money on building a cell, even power supply's can be built or old used supply from the scrap bin would work, it would be best if current cappable and voltage and current can be controlled, amp and volt meter also a plus.

 

[Anonymous]

Nick, HCL will not work with silver, it form AgCl and shield the metal, you need nitric acid.

Jim

 

[qst42know]

Some brazing alloys have a significant tin content. Nitric may be a big problem.

 

[nicknitro]

Thanks Butcher,

It may take a while to understand your process, and I will do some more research on silver cells.

Would Tin interfere any way with the silver nitrate electrolyte? That seems like it would eliminate the AgCl problem, and create my electrolyte at the same time.

I do believe there is a significant amount of tin in the rods. The name brand we currently use is Harris Stay Silv 15.

I stand corrected, the MSDS on these say the chemical composition is 14.5-15.5 % Silver 5 % phosphorous, and the remainder copper. HMM, I wonder why so hard to cut then.

Any ways I guess I could try some nitric now either way. Couldn't hurt, and I believe the HCL Bathed rods did have the AgCl covering them they went from shiny to dull.


Thanks Again All,

Nick

 

[goldsilverpro]

Would Tin interfere any way with the silver nitrate electrolyte? That seems like it would eliminate the AgCl problem, and create my electrolyte at the same time.

A place I worked for ran a lot of dental amalgam. They first sent it out to have the mercury removed by retort. The remainder was melted and it ran about 45% silver and 55% tin. This was run through a silver cell. The tin was all converted to metastannic acid, which stayed on top of the filter cloth. It grew considerably and ended up about 2" thick.


The Bureau of Mines developed a process for removing Au and Ag from 60/40, Sn/Pb solder. They melted the solder and stirred in aluminum, which collected the Au and Ag. The Al/Au/Ag was skimmed off the top. I don't remember the temp, what form of Al was added, or how they got the PMs out of the Al. It was all written up in a RI, a Report of Investigation. I used to have a copy, but no more. A little research would probably dig one up.

The Parkes process worked similarly. They added zinc to molten lead to collect the Ag. The zinc/silver was skimmed off and the Zn was evaporated off, leaving a fairly pure silver. This last part doesn't sound safe at all. Instead, the zinc could probably be dissolved with a 10% sulfuric. The process is for lead but would probably work with tin.

The advantage of these last two processes is that the valuable tin remains metallic.

 

[nicknitro]

GSP,

I've heard that amalgam is some pretty harsh stuff to deal with? Older stuff containing significant mercury, was this your case as well? You say that most was retorted, ever have any issues with residual?

Very interesting info about the tin staying on top of the filter cloth, did you siphon off the bottom solution, "I'm pictureing the meta-stannic staying on top Jelly like, silver nitrate and traces of copper at the bottom of the cell", No?

Forgive me, I still haven't had a chance to research the cell more.

Thanks,
Nick

 

[nicknitro]

Hi all,

Update,


I have switched out the sample that was in HCL"washed", to a dilute nitric solution. The results are night and day. The dilute nitric was all I had availabe at the moment, so it took a while, but the rods dissolved nicely, and I i think the 80 percent copper of these rods also takes care of the cementation process, as a grey precipitant was clearly present.

This process could be very viable with a descent source of tech grade nitric. "Set and forget" style processing. I still need to look into further refining to produce a higher quality AG.

Thank you Jim for the nitric suggestion, once I reallized I had no tin in the material, I was all for it.

Keep updating till I can show a bar of some sorts. First I need some nitric, then hit up Steve for more melting dishes, and research a final refining step. I can see a wash cycle in there, but what about left over copper nitrate? Will there be a residual, produceing more of a sterling?
HCL is out?

Thanks again,

Nick

 

[qst42know]

Some silver will be in solution as well. Test a drop with a few grains of table salt or a drop of HCL watching for the white curds of silver chloride. Don't try to melt the silver nitrate directly. It still needs converted to metallic silver with copper bar. The copper will replace the silver in solution. The solution can be saved to charge the silver cell.

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=2868&start=0&postdays=0&postorder=asc&highlight=sterling+nitric

 

[nicknitro]

Qst42know,

I was under impression that the precipitant from my nitric solution is silver metal. It is a dull grey powder, not a white crystalline substance like silve nitrate. I believe because the rods are 80% copper and only 15% silver, thecopper from the rods is cementing out the silver metal. I have added buss-bar to the filtered solution to see if any more silver drops, but I don't see much after 24 hours.

I have another question about this process. What happens to the 5% phosphorous from these rods? I don't think I wanna use HCL in this solution , because ofthe phosphoric.

Thanks All,
Nick

 

[Harold_V]

You are most likely correct that the copper content will cement the silver nitrate. As long as the silver that is alloyed with the copper doesn't create a barrier, there's no reason for it to not work that way. In a sense, you can dissolve some of the rod, then use more to recover the silver.

As far as the phosphorous is concerned, I am of the impression that it won't be an issue-----but it might be in your best interest to get comments from those that understand chemistry.

Rinse the recovered silver well with water (tap water is fine) until the wash is clear, then melt the silver. A little borax is quite useful. Pour to a cone mold if you have one available, then you can clean the flux and remelt the silver to pour to an ingot or anode. With some luck, you can expect 99% purity.

For greater purity, a silver cell is your next move. They're easy to build and operate. Something as simple as a stainless pan can function perfectly well as the container, which would also be the cathode.

Harold

 

[qst42know]

Though my silver experience is admittedly limited and very much so compared to Harold's. My solutions tested positive for silver until I added a surplus of copper. Both clarity of the solution and the texture of the solids improved after the copper sheet was added.

Perhaps this is from the ratio of materials dissolved, or a condition of using poormans nitric?

 

[nicknitro]

Thanks again guys.

For as far as putting the refined silver into a marketable form, I think I will have look into some silver cell concepts. Best advice for an assay service? Again, to be profitable, I would probably need to build up a stock of at least couple hundred ounces.

Thanks again,
Nick