Furnaces at a Glance

Technologies of Melting Furnaces in Foundries

| Editor: Johanna Erbacher

The heart of every foundry is the melting furnace in which the metal is liquefied. These furnaces use different technologies to melt the material. The aim of every furnace, however, is to consume as little heat and fuel as possible.

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Different technologies are used to melt metal. But which furnaces are used by the companies?
Different technologies are used to melt metal. But which furnaces are used by the companies?
(Source: CC0 / Pixabay)

Step 1: Questions in Advance

When purchasing a melting furnace, several factors must be taken into account. Foundries clarify the following questions in advance:

  • Which alloys are used and what is their melting point?
  • What quantity of metal is to be melted and how high is the required melting capacity?
  • Is the installation and operation of the furnace economical?
  • Which environmental and disposal requirements have to be considered?

Lenaal also had to deal with these questions and decided in favor of the Westomat, which convinced the automotive and electronics supplier with its reliable dosing technology, excellent service and fast supply of insert parts.

Step 2: Selection of the most suitable Furnace Technology

The second step is to select a melting furnace. Metal casting manufacturers use a wide variety of furnace technologies. Foundries need furnaces which can produce metal alloys and additives in a wide variety of casting qualities. These four furnaces are most frequently used in manufacturing foundries:

Induction Furnaces
As the name implies, these furnaces use induction technology with alternating electric currents to achieve the required melting temperature of the metal. Induction furnaces are widely used in foundries because they are high quality, easy to operate and energy efficient. A further advantage of this type of furnace is that it can melt both small quantities of less than 1 kg up as well as larger volumes of up to 100 tons.

An inductor, i.e. a cooled coil, transfers the energy into the molten material. These coils are specially adapted and manufactured to suit the respective furnace shape or individual workpieces. The water-cooled inductor is located outside the electrically non-conductive crucible.

Crucible Furnaces
Crucible furnaces are made of refractory materials such as ceramics because they are exposed to very high temperatures and have to withstand them. The crucible is placed above a heat source to melt the metal and additives it contains. The sizes of the crucibles vary greatly. There are also differences in the design and heating system of the furnaces. Apart from movable and fixed crucible furnaces, there are tiltable and fixed crucible furnaces. A distinction must also be made between resistance-heated and fuel-heated furnaces.

The advantages of a crucible furnace are its low investment costs and simple operation and maintenance. In addition, it is also possible to melt small quantities of metal and quickly change the contents of the crucible. However, crucible furnaces are no longer economical for melting large quantities, as energy consumption increases enormously, and manual operation becomes very time-consuming.

Cupola Furnaces
Cupola furnaces have been used in foundries for a long time. Characteristic of these furnaces is the high, cylindrically shaped chimney, which in turn is lined with clay, bricks and blocks to protect the interior of the furnace from the enormous heat, abrasion and oxidation. For the melting process, several layers of ferroalloys, coke and limestone are placed in the furnace before the metal is added. This results in a chemical reaction in which the impurities in the furnace float on the surface of the metal. In practice, only a few foundries still use cupola furnaces, as the more energy-efficient induction furnaces have prevailed over the classic cupola furnaces.

Electric Arc Furnaces
The electric arc furnace is an electric furnace in which an electric arc generates the heat required to melt the metal. To this end, carbon electrodes are used. In practice, electric arc furnaces are primarily used for melting steel scrap that is used to manufacture new produces.

Step 3: Use Cases of successfully implemented Furnaces

When choosing a suitable furnace, it can also help to find out which furnaces are used by competitors in the industry.
Material recycling is also the focus of many smelting furnace manufacturers, such as ZPF, who produces highly efficient aluminum smelting furnaces. The manufacturer has developed a furnace that melts aluminum chips and recycles material and ingots to ensure sustainable use. Here you can find more information on the melting furnace.

The recycling plant of TRIMET Aluminum SE also focuses on recycling. The company has commissioned a new rotary furnace for melting aluminum scrap in order to meet the growing demand for this light metal. Around 90 % of the aluminum in circulation can be recycled in this way.

While smaller plants already use new, energy-efficient recuperation gas burners with lower CO2 emissions, this technology is now also available for the proven dosing and melting furnaces with high melting capacities offered by RAUCH Ofentechnik.

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