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Induction Heating and Precious Metal Refining

Induction furnace and power supply

A common question we receive at Manhattan Gold & Silver is how we are able to melt down precious metal scraps and form them into bars. Precious metals can be delicate in terms of wear and tear. But when it comes to heat, they can be really tough with melting points of 1946 °F for gold, 1762 °F for silver, 2831 °F for palladium, and a whopping 3220°F for platinum. In order to generate that kind of heat, we use an induction furnace.

Induction furnaces gained much of their popularity near the end of World War II when they earned a reputation for being able to melt and weld weapon parts faster, cheaper, and more precisely than other furnaces. After the war, they easily transferred into peacetime applications – including precious metals refining.

Although the term “furnace” evokes images of roaring flames, an induction furnace doesn’t use any fire of combustible fuel. Rather, it uses the principles of electromagnetic induction to create vast amounts of heat. The furnace itself is essentially a box built around a coil of high conductivity copper tubing that is magnetically shielded and water cooled. Yes, water actually flows though the copper tubing. The power supply controls the heat levels in the furnace. Gold scraps are placed within a crucible, which is placed into the furnace. High-frequency alternating current (AC electricity) is passed through an electromagnet and generated in the precious metal. The metal’s resistance to the electric current generates heat – the level of which can be increased or decreased by changing the flow of electricity.

Induction furnaces are widely used throughout metallurgy not just because of their efficient melting abilities, but also because of their usefulness in forging new alloys. Because induction is a no-contact process that doesn’t utilize combustion, induction furnaces can work in inert atmospheres and vacuums – which is necessary when creating alloys that oxidize if heated in the presence of air. As an additional benefit, the magnetic forces in an induction furnace can be directed to stir the molten metal, which is very useful for creating fully homogenized alloys.

You can certainly witness your metal being melted for a first-hand look at how induction melting works. Also, you can see our induction furnace in action by visiting the MGS YouTube page. The electromagnets in the furnace emit a high-pitched whine when operating, so we’ve recorded our videos without any sound. While induction furnaces may not be pleasant to listen to, they sure are cool to watch!

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