spheroidized

Spheroidized is an adjective describing something that has become spheroidal, or nearly spherical, in shape. In materials science, the term most often refers to a specific microstructural state in steels in which the cementite particles of pearlite have transformed into small, rounded particles dispersed in a ferritic matrix. This microstructure is commonly called spheroidite.

In metallurgy, spheroidizing refers to a heat-treatment process used on medium- to high-carbon steels to improve machinability and ductility. The steel is heated to a temperature just below the lower critical temperature (the A1 line) and held for an extended period, then cooled slowly. The goal is to promote the coarsening and rounding of cementite into spherical particles, yielding a softer, more ductile, and more formable material. Variants of the process, such as full annealing, are designed to produce different spheroidite sizes and distributions.

Industrial relevance includes enhanced machinability for high-carbon steels and improved formability for components that require deep drawing or shaping. While spheroidized steels sacrifice some high-strength performance compared with pearlitic steels, they offer a favorable balance of ductility, toughness, and ease of processing.

Geology also uses the term in a related sense: spheroidal weathering describes the rounding of rock blocks through chemical weathering and physical abrasion, often affecting granitic or other homogeneous rocks and producing rounded outcrops and boulders over time.

In powder metallurgy and additive manufacturing, spheroidized powders—particles with near-spherical shapes—are valued for improved flow, packing density, and sintering behavior. See also pearlite, cementite, spheroidal graphite, and spheroidization.