What Is Annealing in Metallurgy?

What is annealing?

The interior of an annealing furnace. ThyssenKrupp Electrical Steel

Annealing is a heat treatment process used to bring a metal closer to its equilibrium state.

In its heated, soft state, the uniform microstructure of a metal will allow for excellent ductility and workability. In order to perform a full anneal in ferrous metals, the material must be heated above its upper critical temperature long enough to fully transform the microstructure to austenite.

The metal must then be slow-cooled, usually by allowing it to cool in the furnace, so as to allow maximum ferrite and pearlite phase transformation.

Other metals such as brass, silver and copper may be fully annealed by the same process, but may be quickly cooled, even water quenched, to finish the cycle.

Other forms of annealing include process annealing, normalization and stress relief annealing.