Induction Melting Furnace for Precious Metal Melting Industry

When it comes to melting metals through an electromagnetic induction process, some materials are more suitable than others for achieving efficient melting.

In this technical article, we will discuss the behavior of common precious metals when subjected to a high-frequency rippling magnetic field, how to tap into the electrical properties of precious metals with induction melting furnaces, and how this can boost the efficiency of the precious metal melting industry.

Precious metals melting in an Induction Furnace

When the same quantity of two different metals with the same geometric shape and similar melting points are placed in the same rippling magnetic field for the same time interval, their behavior in terms of heat energy will

metal melting equipment design concept
metal melting equipment design concept


According to Faraday’s law of electromagnetic induction, the induced voltage in both metallic masses will be identical.

However, the Joule effect, i.e., the property that causes a material to heat up when an electric current passes through it, will differ for each material due to their resistivity (represented by the Greek letter rho, ρ).

This magnitude, ρ, is the specific resistance for each material, measured in Ω * m.

So, if Q is the heat energy that can be dissipated in the metallic load when a varying electromagnetic field surrounds it, we have:

Q = I2 * R * t


Q = Heat energy produced by the current. In the international system of measurements, it is expressed in joules (J)

I = Intensity of the current that circulates expressed in amperes (A). It equals the Eddy currents circulating through the metallic load.

R = Electrical resistance of the conductor expressed in ohms (Ω).

t = Time, in seconds (s)

But it happens that the resistance R is not the same as the resistivity ρ. Resistance R of two conductors made of different materials but with the same geometric shape, let’s say cylindrical, will be:


R = ρ *


R = resistance in ohms

ρ = resistivity in ohms * meter

l = length in meters

S = cross-section in m2

The different behaviors of these materials under the specified conditions can be explained by their electrical resistivity.

Silver, copper, and gold are the best natural conductors of electricity, and their low resistivity makes them ideal for induction casting.

The induction casting process relies on the rapid increase of the factor I squared in the expression Q = I2 * R * t. This factor more than compensates for the low resistivity of these metals, allowing them to be cast with low energy requirements and in less time than other materials.

Tapping into the electrical properties of precious metals to achieve efficient melting can only be done with an induction melting furnace.

As mentioned above, gold and silver are ideal for casting in induction melting furnaces.

However, other materials that are not as efficient in the melting process are also used in the precious metal melting industry, including platinum, ruthenium, osmium, iridium, and rhodium.

Some of these precious metals are smelted to manufacture fashion jewelry, while others are smelted for industrial, automotive, and aerospace uses.

These materials can also be suitably smelted in induction furnaces, even though the melting process will take longer and require more electric power due to their higher resistivity and higher melting points compared to gold and silver.

Nomenclature of Induction Smelting Furnace Assembly
Nomenclature of Induction Smelting Furnace Assembly

Although resistivity increases with temperature, as shown in the graph above, the relative ease with which different precious metals melt tends to decrease proportionally for all cases as temperature increases.

Thus, our statement that gold and silver are easier to melt than other metals holds true under any temperature scenario.

In the following comparative table (where ρ is at 20 °C), it can be seen that the resistivity of rhodium, iridium, ruthenium, osmium, platinum, and palladium is higher than that of silver and gold, and their melting points are also higher.

However, this high melting point is what justifies their use in equipment that requires great hardness and heat resistance, such as car catalytic converters where rhodium plays a major role, along with palladium and platinum.

Electrical Conductivity

* Although copper is not a precious metal, its presence in the table serves as an element of comparison since it is the material most commonly used as an electrical conductor

**Another electrical magnitude that also gives us an idea of how good is a material as a conductor is its conductivity, which is denoted by σ (sigma). Conductivity is the inverse of resistivity ρ: σ = 1/ρ

How Induction Melting Furnaces Can Boost the Efficiency of the Precious Metal Melting Industry

If we were to define efficiency in the precious metal melting industry, it would be the least amount of resources, energy, and time used to achieve the greatest amount of molten material, with the expected quality and at the minimum environmental cost.

large size metal melting induction furnace
large size metal melting induction furnace

Efficiency means higher profits.

In induction melting furnaces, heat is not applied from external sources, so the absence of direct contact of the material with flames results in a neat and spotless valuable material.

Some of its benefits include:

  • No preheating
  • No long start-up time
  • With no unnecessary high temperatures, which entails more safety and more furnace life
  • It saves maintenance costs

So, the precious metal melting industry has a formidable ally in induction melting furnaces to achieve their efficiency goals: they are the natural choice for producing valuable material in greater quantities, with these advantages:

  • The lowest waste of energy
  • In less time
  • With no fumes
  • Spotless outcomes.

Precious metals such as platinum, palladium, ruthenium, rhodium, osmium, and iridium are used in highly developed industries where state-of-the-art technology is required.

These industries manufacture:

  • Electrical and electronic components such as capacitors and electric contacts
  • Surgical instruments and reagents to measure blood sugar
  • Permanent biocides in plasmonic applications
  • Watches and jewelry
  • Fuel cells for the automotive sector
  • Aircraft engines and spark plugs
  • Petrochemical catalysts
  • Catalytic converters to decontaminate automotive emissions

The supply of the required amounts of these metals as raw material for these industries, with the quality they demand, can only be achieved with high-precision equipment, including induction melting furnaces.



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