Other methods of casting
Melt spinning is the rapid cooling of a metal to form a metallic glass ribbon. A cooling rate of 107 K s-1 can be achieved by casting onto a water-cooled, rotating Cu wheel. Heat extraction is very rapid, and thin sections are formed (~50 mm), so Newtonian cooling is observed due to the small length scale.
A slowed down video of the process is shown below;
The fast cooling rate means that amorphous metal (metallic glass) is formed. This has very different properties compared to the alloy with a crystal structure. The metallic glass ribbon is often used in electronic applications, as when a magnetic metal (iron, cobalt, nickel) is used within the casting alloy, the amorphous material forms a magnet with low coercivity, due to the lack of regular structure. This means that the magnetic field can be easily removed.
Centrifugal casting is used to create hollow, cylindrical parts. The mould rotates, and is only partially filled with molten metal depending on the required thickness. The centrifugal force generated by the mould forces the metal against the wall, giving a good surface finish.
Centrifugal forces can also be used in casting when creating solid objects, the force being used instead of pressure or gravity to push the metal into the mould.
- Good external detail
- High control of the microstructure
- No core required to make hollow component
- Poor internal surface quality
- Inner cross section must be circular