Spheroidite

What Does Spheroidite Mean?

A spheroidite refers to a microscopic constituent in some steels, composed of spherically-shaped cementite particles in an alpha ferrite matrix. Spheroidite is the most ductile and softest type of steel on the granular molecular level.

Its purpose is to soften higher carbon steels and produce more formability. Spheroidite structures have higher toughness and lower hardness than pearlite structures. Therefore, metals with spheroidite are easier to cold work.

Corrosionpedia Explains Spheroidite

Spheroidite is formed when carbon steel is heated for more than 30 hours at temperatures exceeding 690°C. It can also form at lower temperatures after a prolonged exposure in a diffusion-controlled process. This prolonged exposure to such temperature extremes results in a structure of spheres or rods of cementite within a primary structure (ferrite or pearlite).