A Ciência da Têmpera do Aço - História e Tecnologia.

Initially, a brief historical review related to the discovery of iron is made. Studies of artifacts such as tools blades and weapons from more than 1000 years BC, allowed us to conclude that the knowledge already existed to increase the hardness of metals, both due to the increase in carbon content and sudden cooling from high temperatures (a process called tempering or hardening). This suggests that there was a considerable degree of sophistication on the part of these early blacksmiths. Next, the basics of materials theory and formation of the crystalline structure of iron- carbide iron (Fe-Fe3C) based on the phase diagram are presented. Modernly, materials science has shown that increasing temperature changes the atomic structure of ferrite (pure iron with BCC structure) to austenite (FCC), which allows the inclusion of other elements, such as carbon, for example. The quenching process, on the other hand, abruptly changes the atomic structure from austenite to martensite (BCT), keeping the carbon attached to the final structure, giving the new material a significant increase in hardness. Although the context of the article is, at first glance, historical, the controlled heat treatment of steel is essential for the modern world and is used to ensure that it has the desired properties in industry in general. [ABSTRACT FROM AUTHOR]