Tungsten Carbide Method--Information From a Professional Chemist!

I read a post a few days ago and it got me thinking of new methods for cleaning metals. I have seen gold finger harvesting done and I thought to myself, "there has got to be an effective way to isolate only the WC (Tungsten Carbide) from saw blades. I mean to remove the silver solder and the steel centers. I posted a question looking for a chemist to respond. I got just that and it is taking my brain to a whole new level of ideas on how to remove/isolate elements and compounds by using some chemistry. I sold a scrap gold ring and the guy at the shop tested it with Nitric Acid which got me thinking.
This was in response fr the best method for removing saw blade teeth. Maybe even have some silver power/dust too!!!




"I still think the best way to remove the teeth is through melting the solder, though you might look for a more efficient way of doing it. An oxy-acetylene torch is hotter, and would be quicker than the MAPP.. Special burners heating several teeth at once - or a whole blade - would help too. Alternatively, the blades could be treated in batches in a furnace and the teeth collected afterward.

The proper acid for dissolving silver solder would be nitric acid, but there are several problems with this method. First, it would take more time than you might think because the action of the acid along the very thin bond line between the blade and the tooth would be slow. Second, the carbide teeth are typically made from tungsten carbide powder that's been cemented together with cobalt. Since nitric acid also attacks cobalt (but not the carbide), long exposure to the acid may cause the teeth to disintegrate. Third, the acid will also attack the steel (if it's not stainless). The problem with this is that it will use up a lot of the acid and greatly increase the overall acid requirement. Finally, the large amount of spent acid, contaminants, and residues would present a significant disposal problem and cost.

If you really want the teeth free of the silver solder, I'd suggest removing the teeth with heat and then using a brief acid treatment to remove the solder from them. This would use far less acid, and exposure of the teeth to the acid would be much shorter. Further, if the teeth do disintegrate to any degree the carbide powder would settle to the bottom of the tank and could be recovered. As a bonus, silver could be recovered from the acid solution. I think this approach would be the most economical solution, all things considered.

BTW, though tungsten carbide powder itself is not attacked by nitric acid alone, it can be dissolved in a nitric-hydrofluoric acid mixture. As if nitric acid is not nasty enough, hydrofluoric is a whole problem of its own. My advice, however, if to leave it alone."


Very Cool
--Mike

i think you missed the part where it is too laborous when you have a substantial amount. this would be fine if one had say only a hundred or so blades but with a lot(1000+) this would be insane!

could this be done by the batch in some form of oven or furnace? if you could run 50 or so at a time, you'd move pretty quick

then again who's getting that large volume of blades?!