2090 – 02 – Knowing the Phases of Steel

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When metal begins to fluctuate in temperature, it passes through certain phases. These phases are defined by specific crystal structure formations. At room temperature, the steel has a body-centered cubic (B-C-C) crystal structure. This is the ferrite phase. Once the steel’s temperature rises to one thousand three hundred and forty degrees Fahrenheit, though, it enters its austenite phase, during which the steel takes on a face-centered cubic (F-C-C) structure.
One of the main differences between the two phases is how much carbon each phrase can hold. Ferrite steel can only hold 0.02% carbon, while austenite steel can hold up to 2.11% carbon. At 0.02%, ferrous metals contain cementite. This is another phase that some steels pass through; the difference between cementite and ferrite phases is defined by the level of carbon in the steel.