How Does a Melting Furnace Work?
Melting furnaces are used to overheat solid materials until they liquefy. Often, thermal processing equipment is used to alter the surface or internal characteristics of materials by carefully elevating their temperature. In the case of metals, this typically increases ductility at the expense of both hardness and strength. This requires an industrial furnace capable of generating and maintaining temperatures below that of the material’s melting point.
A melting furnace, by comparison, generates overhot temperatures that exceed the metal’s melting point and cause decomposition of its physical structure which leads to liquefaction. This phase transition is utterly dependent on both temperature and pressure. Few metals can exist in a liquid state at ambient temperatures, with the exception of mercury (Hg) and known eutectics like gallium-based (Ga-) alloys.
To achieve a homogeneous molten mixture, the melting furnace must be capable of generating and maintaining the requisite temperatures over a sustained period. There are several melting furnace architectures capable of performing this process. In this blog post, Thermcraft will explore some of the primary types of melting furnaces available on the market today.
Cupola Melting Furnaces
A cupola melting furnace typically comprises a vertical heating chamber in a shaft-like arrangement, which is filled with layers of combustible matter such as coke and limestone. Inlets allow air into the chamber to facilitate combustion while a working door enables easy access to the lowest portion of the cupola. This is where raw materials are reduced to a molten mixture that can be periodically extruded through the drop-bottom spout.
Cupola furnaces are the preferred tool for melting procedures in ferrous metal foundries. The architecture is simple and robust, but additional considerations must be made for safe venting and control of emissions. Often, the top of the cupola shaft will be capped with an innovative filter designed to remove particulates from gaseous waste.
Induction melting furnaces operate on a radically different principle to the cupola version. They use coiled heating elements embedded within a crucible or integrated into the walls of the heating chamber itself. These convert electrical energy into heat which is radiated through the material with outstanding degrees of thermal uniformity.
Limiting the use of combustible fuels in a facility, particularly for routine melting applications, translates into safer daily operation for personnel and for components. Helically-wound induction coils engineered from refractory heating metals and ceramics improve service longevity and enable good compatibility with additional controls. Thermal cycling can be automated and additional controls can be implemented to reduce the generation and emission of toxic metal vapors in metal melting furnaces.
Melting Furnaces from Thermcraft
Thermcraft specializes in the design and construction of bespoke thermal processing equipment for demanding applications. We can engineer melting furnaces for standard foundry processing, or for novel areas of research and development such as crystal growth.