Steel is the major material for fastener, include low/midium/high carbon.

Carbon Steel：

Based on the Carbon (C) content, carbon steel is broken down into four classes based on carbon content:

Low-carbon steel: 0.05 to 0.30% carbon (plain carbon steel) content. Eg. 1008,1015,1022

Medium-carbon steel: Approximately 0.3–0.6% carbon content. Balances ductility and strength and has good wear resistance; used for large parts, forging and automotive components.

High-carbon steel: Approximately 0.60 to 1.00% carbon content. Very strong, used for springs, edged tools, and high-strength wires.

Alloy steel: With a variety of elements in total amounts between 1.0% and 50% by weight to improve its mechanical properties, eg SCM435