Welding Inspection & Metallurgy API ICP Self Study Notes

Introduction
The component elements in steel can be categorized in terms of their crystal
structures. At least a basic knowledge of the practical implications of these
crystal arrangements is essential to understand the performance of steel in
service. The structures are dependent upon the (1) concentrations of each
element, (2) the fashion in which the steel is cooled from furnace
temperatures, and (3) the amount of cold work performed on the steel.
Crystal Structures
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Ferrite
Ferrite (α), is the crystal arrangement for pure iron. This form exists as part
of the structure in most steels and can usefully absorb carbides of iron and
other metals by diffusion in the solid state. Ferrite takes a body centred cubic
(bcc) form and is soft and ductile.