All steels are alloys, however, not all of them are called “alloy steels.” Alloy steel requires the intentional addition of additional elements to the iron and carbon composition. When alloying elements are introduced in modest amounts, usually no more than 5%, these metals can improve a variety of qualities, including corrosion resistance and machinability. Manganese, Silicon, Molybdenum, Chromium, Vanadium, and Nickel are some of the most popular elements that are added to create alloy steels.