Metal Melting Furnaces and Die Casting: Types and Processes
Metal Melting Furnaces
A melting furnace is a device where either the combustion of a material or electric power is supplied to provide the heat needed to melt metal. The molten metal acquires the fluidity necessary for proper mold filling.
Furnace Classification:
- Cuba Oven: The metal is in contact with the fuel (e.g., blast furnace, cupola furnace).
- Hearth Furnace: The metal is in contact with exhaust gases (e.g., Martin Siemens oven, hearth oven).
- Controlled Atmosphere Furnace: No contact with fuel (e.g., crucible furnace, muffle furnace).
- Electric Arc Furnace:
Advantages of Electric Arc Furnaces:
- Temperatures over 3500°C can be obtained in some models.
- Precise control over the rate of temperature elevation and maintenance of boundaries with fully automatic regulation.
- The charge is completely free of contamination from combustible materials.
- Complete control of the atmosphere in contact with the melt, making it oxidizing or reducing at will. Some types of furnaces can even operate in a vacuum.
- Refractory linings have a longer duration than in other types of furnaces.
- They are quick to set up.
Resistance Furnaces:
- Non-Metallic Resistance (Graphite)
- Metallic Resistance
Induction Furnaces:
- High Frequency
- Low Frequency
Die Casting
Die casting, or injection molding, is a process where molten metal is introduced at high pressure into a mold, facilitating the creation of intricate geometries.
Benefits of Die Casting:
Advantages of this process include high productivity, good surface finish, and dimensional accuracy. A notable disadvantage is the intrinsic porosity of the manufactured parts, which significantly influences their mechanical strength. Commonly used metals include Aluminum (Al), Copper (Cu), Zinc (Zn), and Magnesium (Mg).
Warm chamber machines are typically used for metals with lower melting points, such as zinc or lead. Using these machines for metals with higher melting points would cause rapid wear of the machine’s materials due to prolonged exposure to high temperatures.
Centrifugal Casting:
In centrifugal casting, molten metal is poured into a rotating mold through a sprue. The mold contains clusters of parts placed symmetrically around the periphery. As the system rotates, a horizontal centrifugal force is generated. After the outer layer solidifies, the mold is raised to a vertical position, allowing the metal to flow into the core and the collars.
Combustible Material
A combustible material is any substance that can burn under certain conditions.
- Solid Fuels
- Liquid Fuels
- Gaseous Fuels
Refractory Materials
Refractory materials are those whose properties allow them to withstand very high temperatures without suffering any deterioration, such as corrosion. This makes them suitable for use in furnace construction. These materials are typically composed of tiny particles of a refractory material, bound together by another material with different, but finer, characteristics.