January 18th, 2012
Mechanical properties of iron and its alloys are evaluated through various tests, such as scale Brinell, Rockwell scale or tensile tests, among others, the results are so consistent that iron is often used to calibrate measurements or to compare the results of a test of another. Those measurements revealed that the mechanical properties of iron depend on purity: the purer iron crystals are much softer than aluminum. The addition of only 10 parts per million of carbon can double hardness. Hardness increases rapidly with a carbon content of 0.2% and is saturated at ~ 0.6%. Iron industrial product, which is the purest (about 99.99% purity) has a Brinell hardness of 20-30.
Allotropic iron is an example of a metal, knowing at least four allotropic forms thereof, called α, γ, δ and ε, high pressure, there is some experimental evidence considered controversial for a stable β form at temperatures and pressures high.
As the molten iron cools, it crystallizes at 1538 ° C in its allotropic δ, which has centered cubic crystal structure. Continued cooling of these crystals, changing the 1394 ° C, when the structure is known as γ-iron or austenite.
