Spheroidizing refers to a heat treatment material modification process that is used to convert granular structures of the material into a spheroidal form. The process is performed to improve a metal’s cold forming capability.

Spheroidizing is performed by annealing steels with more than 0.8% carbon. The metal is heated to a temperature of about 1200°F (650°C) and maintained at this temperature for a predetermined amount of time to convert its microstructure. This allows for a cementite steel structure to change from a lamella formation to an alpha ferrite matrix. The alpha ferrite matrix is made up of particles of spheroidal cementite formations.

Spherodizing is industrially performed in an endothermic atmosphere to prevent oxidation and decarburization.

Spheroidizing is used primarily to treat various types of steels, and is used to improve the machinability of hypereutectoid and tool steels. This is accomplished by lowering the metal’s steel flow stress.

Spherodizing is typically done on parts that have been work hardened for improved ductility, toughness, strength and reduced hardness.