Ferrite is a body-centered cubic (BCC) form of iron, in which a very small amount (a maximum of 0.02% at 1333°F / 723°C) of carbon is disolved. This is far less carbon than can be dissolved in either austenite or martensite, because the BCC structure has much less interstitial space than the FCC structure. Ferrite is the component which gives steel and cast iron their magnetic properties, and is the classic example of a ferromagnetic material. This is also the reason that tool steel becomes non-magnetic above the hardening temperature - all of the ferrite has been converted to austenite. Most "mild" steels (plain carbon steels with up to about 0.2 wt% C) consist mostly of ferrite, with increasing amounts of cementite as the carbon content is increased, which together with ferrite, form the mechanical mixture pearlite. Any iron-carbon alloy will contain some amount of ferrite if it is allowed to reach equilibrium at room temperature.
|Body Centered Cubic Unit Cell||Photomicrograph of Ferrite Structure|
This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Ferrite (iron)".
Body Centered Cubic Unit Cell image from the Wikipedia article "Crystal structure".
Ferrite Photomicrograph Copyright © British Steel; Used with permission, Courtesy of Corus.
Copyright © 2006 Peter L Berglund. (except for Ferrite photomicrograph) Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".