Austenitizing steel about 55 °C above Ac3 (or Acm for high-carbon grades), then cooling in still or moving air. The result is a fine, uniform ferrite and pearlite structure that is stronger and harder than a full anneal. Forgings and castings are normalized to erase coarse or banded structure before machining and hardening, and parts that need rehardening are usually normalized first.
Forgings get normalized at 1,650 before rough machining, the as-forged grain is all over the place.
Normalize before rehardening a lot. Going straight back to the hardening heat on an already-hardened part invites cracks and mixed grain.
Also heard as
- normalize
- normalise
Related terms
Annealing
Heating metal and cooling it slowly to soften it, relieve stress and make it easier to machine or form.
Grain size
The average size of the crystals in a metal, usually reported as an ASTM number where higher means finer.
Pearlite
A layered mix of ferrite and cementite that forms when austenite cools slowly through the eutectoid range.
Rehard
To harden a part again after it misses hardness, usually after normalizing or annealing it first.