To hold a steel alloy at a temperature just below its critical point for many hours, causing the cementite lamellae to break down and form spherical particles within a ferrite matrix. This process creates the softest and most ductile state possible for high-carbon steels. Machinists and formers require this structure to cut or cold-work the metal without breaking their tools.
We need to spheroidize this batch of 52100 bearing steel for 24 hours before they can machine it.
Related terms
Spheroidizing
Long holds near the lower critical temperature that turn carbides into small round particles.
Cementite
Iron carbide, Fe3C: the hard, brittle compound that carries most of the carbon in slowly cooled steel.
Dead soft
Fully annealed to the lowest hardness the metal can reach, with no work hardening left in it.
Annealing
Heating metal and cooling it slowly to soften it, relieve stress and make it easier to machine or form.