Fasteners are often made of steel, but there are many different types of steel. Here are the steels most commonly used for fasteners:
Alloy steels: Steels alloyed with molybdenum, nickel, and chromium (AISI 4037, 4130, 8630) are best if strength is required. These steels also have good cold-forming properties when annealed and can be heat-treated for the best combination of strength, toughness, and shock resistance.(…)
via A Quick Look at Steels Used for Fasteners | Fasteners content from Machine Design.