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Anybody TIG welded fine silver?

snowman

Diamond
Joined
Jul 31, 2004
Location
Southeast Michigan
I'm curious. I'd like to weld some rings closed. I know it's possible, but I'm curious how easy it is to add filler material, as well as how much you have to worry about oxidation given the thermal conductivity.
 
Oxidation with a shielding gas? Of course I have no idea how big or small these rings are so maybe large enough for hot metal to be outside the shielded area. Silver can be fused with a oxy/acet torch I believe but I have never done it, least not intentionally. Oxidation does happen with the torch but it is easily cleaned off by polishing. I have to ask, why not silver solder (high temp - not the plumbers type) them? You could use the TIG torch for your heat source.
 
Siu Carbondale grad students did this with normal sized tigs for thesis work.
Puk and omron make mini pulse tigs for this type of work. Laser welders too. If subbing out many jewelery repair shops have these welders, if buying the welder check rio-grande.

They are cool machines, you hold the parts in your hand under a scope and touch them to the electrode. The welder settings are all machine taken care of for your material.
 
Silver is an exceptionally good conductor of heat, so if it's a big item, you are going to find yourself with areas outside of the shielding gas. Hence my concern. Given the thermal conductivity, I was also worried about the transition from solid to liquid, essentially losing the whole piece.

Puk welders are just a tungsten spot welder of sorts.

The product I'm working on is .999 fine silver. I'd like to be able to stamp it as such. If I add any braze, I cannot do that, as it's no longer fine silver.
 
You can weld gold (higher conductivity) with the puk, no filler metal so your alloy stays the same.
It is a tig, just a spot at a time- and the spots happen fast if you step on the foot pedal.
Fine silver doesn’t tarnish readily.
 
Thermal conductivity is considerably lower. I've used a PUK. They have their place. It could work for this. Laser would work better. I'm not spending $5600 on a PUK or 25k on a laser when I have a syncrowave that should do the job. I was simply looking for people that had done it to say "yes, it TIG welds beautifully" (which Platinum does btw) Or people to say molten silver can absorb 20x it's volume in oxygen...so you need to do this. (which it absolutely can)
 
Hi snowman:
I have laser welded fine silver and I do recall some problems with it: the principal standout being the joy of holding it with my naked fingers, so yeah, it got toasty pretty quick, and I smoked a couple of fingerprints because of it before I let it go and made a rude noise.

This was for a cyclotron part and a big deal was made of it being fine silver, so I was asked to make my own filler wire from a slug the customer provided, and I'm confident it was not Sterling silver.
I think the normal wire that's available from the store is Sterling silver and has platinum in it.
This was all a decade or more ago, so don't quote me on it.

I seem to recall having to run it pretty hot because of the reflectivity of the puddle and the rapid heat transfer away from the melt zone.
(Long pulse duration and high voltage along with high pulse frequency)

If I remember right I also had to soot it with the oxyacetylene torch (acetylene only of course) to cut down the reflectivity enough to start a puddle.
(I doubt you'd have to do that with TIG...your heat source is not coherent monochromatic light as it is with a laser)

I had to fiddle with it a bit, and the weld carried no load, so I'm not sure how good a weld it actually was (I was asked to fill in a machining divot)
Whether you will see similar problems TIG welding it I cannot say.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
Ouch....Fine silver is the most reflective precious metal up until the point it develops a silver sulfide tarnish. You said sterling has some platinum, it's likely actually rhodium. It's plated on to some sterling to develop a protective layer so that that sulfide layer doesn't form. When I buy scrap sterling jewelry, the rhodium plated stuff jumps out at me because it's so reflective it looks fake.

The silver is 99.9% pure.

The weld quality is my biggest issues with PUK welders. There is nearly zero penetration the way most people use them.
 
Hi again snowman:
It's actually Sterling silver welding wire that has a bit of platinum in it (I believe).
Somehow the platinum makes it weld better.
I looked it up when I did the project but my memory is a bit hazy about the details.
Apparently the alloying elements in that welding wire would have totally ruined the part, so many hoops were jumped to avoid it and get what they wanted.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
wow, just wow. sooo much wrong in this thread...

sterling silver is .925 silver remainder copper and trace elements. absolutely no platinum or rhodium. it was sometimes plated with rhodium, but not any more with the price of it now.

"fine" silver, as snowman says, is the trade term for .999 silver, usually electrolytically refined. fine silver does NOT oxidize much, to the point you can melt it, cool in air, and it stays bright and shiny, kind of freaky if you haven't ever done it. it IS highly reactive with sulfur, and "tarnish" on common silver items is a combination of copper oxide and silver sulfide. the copper in common alloys does react readily with O2, and also absorbs a LOT at molten temps. (I think a lot more than silver).

silver is actually the most conductive element, the" whitest" metal (thus the use for mirrors), the most thermally conductive element. all for the same reason, lots of free electrons.

gold, even pure gold, is LESS conductive, less conductive than copper even. gold is used on contacts for its corrosion resistance not it's conductivity . common jewelry alloys such as 14KT and 18KT are MUCH less conductive VS pure silver.

ALL pure metals (most?) are ""very fluid". the slushy state of most metals we melt are a transition between the solidus and liquidus points on a phase diagram.

I have GTAW (TIG) welded 22KT gold. works reasonably well. pure silver, probably because of the resistance to oxidation, can be fused in a thin wire with a torch flame (with care, some will ball up if you don't pull the heat in time). it might be possible to do that depending on the surface area of the parts you are working on. without more info on the size, shape, and application of the "rings" its hard to know. are they for jewelry? what size and how many?

fine silver makes a pretty crappy jewelry metal, too soft for all but the most massive pieces.
 
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thanks Marcus, that is a VERY specialized, rare and unusual alloy and wire. never herd of it. who is/was making that?
(from re-reading it it seems to be for laser jewelry welders, so I assume marketed for that use?)
 
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Hi again cyanidekid:
Yeah it's a laser welding wire and I have no idea who makes it or where you can buy it.
I only looked into it because I had this weirdass job that I got sweet talked into (I'm a real fool for challenges!)
I knew silver was going to be a struggle to laser weld because of the reflectivity you were talking about...it's like shining a flashlight into a mirror.

So I did some research after failing miserably in my first attempts to weld it, and although it was soooo promising I couldn't use it, and had to figure out another way.

I lost my ass on it but I DID it!
The soot did the trick, and I never said a word.
All went well and the customer never complained, so I wiped my brow and kept schtumm (until today).
Now I'm retired and the customer went belly-up years ago, so all is good.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
wow, just wow. sooo much wrong in this thread...

sterling silver is .925 silver remainder copper and trace elements. absolutely no platinum or rhodium. it was sometimes plated with rhodium, but not any more with the price of it now.

"fine" silver, as snowman says, is the trade term for .999 silver, usually electrolytically refined. fine silver does NOT oxidize much, to the point you can melt it, cool in air, and it stays bright and shiny, kind of freaky if you haven't ever done it. it IS highly reactive with sulfur, and "tarnish" on common silver items is a combination of copper oxide and silver sulfide. the copper in common alloys does react readily with O2, and also absorbs a LOT at molten temps. (I think a lot more than silver).
It is actually the silver that absorbs the O2 at molten temps. Upon freezing, it expells that oxygen and spits it out, causing cavitation. The copper is added to silver for a number of reasons, one being to bind the oxygen as copper oxide. You can melt it and cool it in air, but it will become porous unless you kept it in a reducing atmosphere until it freezes. This is a common phenomenon in the fire assay process when assaying bullion. Upon cooling, your silver bead will sprout, sometimes so violently that you lose silver, erroneously decreasing your assay. This is why silver, when molten, has to be kept in a reducing or inert atmosphere.
 
I have a belt buckle with gold fused to fine silver, it was done at a bench- no special atmosphere. My daily driver belt has fine silver cast into “pure” iron then forged- that was done in a shop with dirt floors and 1/2 a roof.
I have cast both fine and sterling, never in a chamber. Repaired mixed metals professionally for years- never more than flux to weld it with smith micro torch’s. Sometimes a ti pick to get two puddles into one. I preferred welding over solder because less porosity when filling big gaps.
Moms use fine silver pmc in kitchens with mapp torches every day- fine silver was the first pmc because it is inert and cheap.
Native and Chinese traditional jewelry is near fine silver cast into wood, bone, dirt, leather.... melted over a fire in the dust and rain.
Pure metals want to be worked. Silver likes being cast (melted), copper likes to be upset and bent, iron likes to be squished and twisted.
 
Yes, you can work silver with a torch. The torch provides a reducing environment. This is the reason you hold your torch over molten silver until it solidifies. The flux not only protects the surface of the sterling from oxygen but also dissolves the small amount of copper oxide created. Without flux, the oxygen oxidizes the copper to create fire scale.

Now, cast the same fine silver with an oxidizing flame on your torch. All of a sudden you have a porous piece of shit. Molten silver absorbs 10x it's own volume in gaseous oxygen. Upon cooling, any of that gaseous oxygen violently erupts from it.

(I said 20x previously, it's actually 10x)

The reason PMC clay works is because it's tiny particles intertwined with a cellulose binder, often just rice starch. The rice starch burns locally, both fluxing the tiny silver particles as well as maintaining a reducing environment for the momentarily molten silver.

I work with silver daily. I have books written about silver. None covered welding, and I've never TIG welded it on a macro scale.
 
Re read your sources. Silver absorbs copper oxide (sterling).
Fine silver does not. You do not have to keep flame over silver.
Sterling is a mixed bag, some is wonderful, some has zinc.
Siu Carbondale. Call the metals department- they where big on tig silver for a few years.
I have read and been to a snag conferences and a few of the Santa Fe symposiums, never herd of silver sucking up 10 x air. That would look cool if you could get that foam.
 
It is actually the silver that absorbs the O2 at molten temps. Upon freezing, it expells that oxygen and spits it out, causing cavitation. The copper is added to silver for a number of reasons, one being to bind the oxygen as copper oxide. You can melt it and cool it in air, but it will become porous unless you kept it in a reducing atmosphere until it freezes. This is a common phenomenon in the fire assay process when assaying bullion. Upon cooling, your silver bead will sprout, sometimes so violently that you lose silver, erroneously decreasing your assay. This is why silver, when molten, has to be kept in a reducing or inert atmosphere.
I haven't noticed that, perhaps I usually allow fine silver to solidify in the reducing flame. copper does absorb O2 for sure as well. ill have to do a test later...melt some precipitate ive got.
 
Re read your sources. Silver absorbs copper oxide (sterling).
Fine silver does not. You do not have to keep flame over silver.
Sterling is a mixed bag, some is wonderful, some has zinc.
Siu Carbondale. Call the metals department- they where big on tig silver for a few years.
I have read and been to a snag conferences and a few of the Santa Fe symposiums, never herd of silver sucking up 10 x air. That would look cool if you could get that foam.

"The high solubility of oxygen in molten silver is familiar enough. In air at atmospheric pressure (ie, under a partial pressure of about one-fifth of an atmosphere of oxygen) silver, when just above it's melting point, can take into solution about 10 times its volume of oxygen. When silver so saturated with oxygen freezes, solidifcation commences at about 951 deg C, which is below the melting point of pure silver, 960.8 deg C, and is not completed until the temerpature has fallen to about 930 deg C. Most of the dissolved oxygen is vigorously evolved just before solidification is complete, giving rise to the familiar phenomenon of "spit."

Silver Economics, Metallurgy, and Use. Butts and Coxe, 1967, Chapter 20 "Oxygen in Silver", second paragraph.
 








 
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