How Induction Melting Works in a Coreless Furnace

Induction heating is a way of transferring the energy from heat. Melting steel is one of the uses of an induction furnace. The U.S. imports more steel than any other country in the world. In 2017, imports to the United States included $27 billion worth of steel. Steel melting induction furnaces are used for melting and creating alloys from a range of metals. The melt loss is minimal, as is the refining of the metal. The coreless is one kind of induction furnace.

The Coreless Furnace

The coil is central to the functioning of the coreless steel melting induction furnaces. This coil is a hollow piece of highly durable, high conductivity tubing made of copper, and is formed in a helical shape. A steel shell keeps the coil’s shape, and heating of the supportive shell is prevented by magnetic shielding. The coil is cooled by water, and the water is recirculated to a cooling tower. Trunnions hold up the shell to enable pouring.

Frequency Ranges

A crucible takes shape when a granular refractory is pushed between the coil and a hollow former. This melts with the initial heating, resulting in a sintered lining. The voltage and frequency of the major supply is converted by the power cubicle; this conversion is necessary for electrical melting. In induction melting, frequencies range from 50 cycles per second, referred to as the mains frequency, to 10,000 cycles per second, referred to as high frequency. A higher frequency can increase the maximum power that can be used in the furnace and reduce the turbulence.


When the charge material has melted, the magnetic field and the currents of electricity in the induction coil interact. This causes stirring in the melted metal. This stirring makes the molten metal rise in the center, creating the expected meniscus on the metal’s surface. The amount of stirring depends on the frequency and power used. It is also dependent on the shape and size of the coil and the metal’s viscosity and density. Stirring in the bath is crucial because it contributes to alloy mixing and the melting of turnings, and it sets a uniform temperature everywhere in the furnace. Too much stirring may result in more gas pick up, wear in the lining, and alloy oxidizing.

If you’re considering buying a steel melting induction furnace, it’s important that you know the basics about how these furnaces operate. For more information, contact our knowledgeable team today.

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