Heat-treatable steels are in the mechanical construction steel range. They are characterized by carbon content usually in excess of 0.25%, and may or may not be alloys.
Heat-treatable steels are used to fabricate parts that require a combination of strength and tenacity, with relatively uniform values throughout the cross section or down to a certain depth. These properties are attained by means of quenching and tempering, which comprise the heat-treatment process.