Ferrite - iron oxide compound

The interstitial solid solution formed when carbon dissolves in the interstices of the α-Fe lattice is called ferrite.

It has a BCC structure and shows equiaxed polygonal grain distribution, denoted by the symbol F. Its microstructure and properties are similar to those of pure iron, with good plasticity and toughness, but relatively low strength and hardness (30-100 HB).

In alloy steels, it is the solid solution of carbon and alloying elements in α-Fe. The solubility of carbon in α-Fe is very low; at the AC1 temperature, the maximum solubility of carbon is 0.0218%, but it decreases to 0.0084% as the temperature drops.

Therefore, under slow cooling conditions, tertiary cementite may appear at ferrite grain boundaries. As the carbon content in steel increases, the relative amount of ferrite decreases and the amount of pearlite increases, at which point ferrite appears in a network or crescent shape.

Ferrite cores can be used in transformers, electromagnets, and electronic inductors, where the ferrite's high electrical resistance leads to very low eddy current losses.

Commonly, they are seen as a lump in a computer cable, which is called a ferrite bead that helps to prevent high-frequency electrical noise (which is called the radio frequency interference) either from exiting or entering the equipment.

The early computer memories stored the data in the residual magnetic fields of the hard ferrite cores that were assembled into core memory arrays. Ferrite powders can be used in magnetic recording tape coatings.