Greetings, If this is posted elsewhere I apologize. I couldn't find any specific info. I have a US Solid 15kw High Freq. Induction Heater 30-80 KHz 220v that I use for forging knives and swords. I have a customer that wants silver hardware on his sword including Tsuba (guard) and other fittings. I know next to nothing about foundry work and was wondering if could get a crucible and melt silver down to pour into a mold of these various items? Any ideas?
I'm under the impression (and could be wrong) that there's some differences between induction heating ferrous and non ferrous metals. Not to mention differences between induction heaters and induction furnaces. First up would be to contact the manufacturer and hit them up with the idea.
First, when you use an electric (can also be induction) that powerful, get one on 380/400V three phase, that is usual with such power. 220/230V is for standard household appliacnces for max. 25-35A (5.5-7.7kW). Second, how much silver do you want to melt ? For amounts up to one kg, a small DIY propane or natural gas paint can furnace with forced air suffices or just an electrical furnace of only 2kW which indeed runs on 220V household supply, unless you want to melt bullion bars of several kilos. For small amounts up till 700g (bronze, copper or silver alloy) I use such a paint can furnace indoors inside a fume hood, with fire safety precautions. It can reach 1300ºC inside the crucible and it melts within 15-20 minutes, assumed starting with a cold furnace. Induction melding is much more efficient, but these furnaces are brutally expensive, unless you are an electronics hobbyist. There are lots of Youtube videos on how to DIY an induction furnace. Commercial foundries however do use induction furnaces because the cost is feasible for the much larger quantities.
This guy melts small quantities of silver and casts it using a Mapp gas torch and very small crucible. For what you want to do it looks like a practical way to go with absolutely minimal investment of time and equipment. Denis
Silver and copper are extremely difficult to melt relative to ferrous alloys. They do not undergo hysteresis. I would highly recommend you lost wax cast the hardware. You can use your power supply to melt but you will need to use a small graphite crucible as a susceptor to couple with the field. I melt silver quite frequently using gas and prefer it over induction because I can keep the atmosphere rich. Molten silver dissolves considerable amounts of molecular oxygen when molten and gives it up as it solidifies, sometimes spitting and leaving a rough, spalled surface.
Lou has it right. Lost wax all the way. We torch it in a small crucible and pour into a flask under vacuum. Research how they cast jewelry. https://www.youtube.com/user/brotherbanzai does bronze accoutrements for his swords. His method is ceramic shell. Silver is a bit on the expensive side for using with ceramic shell. Lots of waste.
One other option would be to have a talk with a local dental lab that makes gold crowns assuming they are still in business these days. They use a washing machine sized induction/centrifugal casting machine to make investment castings of dental crowns. They could even supply the hard/tough gold-cobalt alloys to make your parts.
