Bolts are typically made from steel, which is an alloy of iron and carbon that provides excellent strength and durability. Carbon steel is the most common material because it offers a good balance of strength, cost-effectiveness, and ease of manufacturing. The carbon content usually ranges from 0.1% to 0.6%, affecting the bolt's hardness and brittleness. For applications requiring better corrosion resistance, stainless steel bolts are used instead, containing chromium and nickel alongside iron. Specialized bolts are made from other materials depending on their intended use: brass or bronze bolts resist corrosion in marine environments, aluminum bolts are chosen for weight-sensitive applications despite lower strength, and titanium bolts provide exceptional strength-to-weight ratios for aerospace applications. Galvanized bolts have a zinc coating for additional corrosion protection. The manufacturing process involves drawing wire, cutting and forming the bolt head and thread, and heat-treating to achieve desired strength properties. Bolts are graded by standards such as ISO or SAE specifications, which define their material composition and minimum tensile strength. Higher-grade bolts (like grade 8.8 or 10.9 in metric systems) undergo greater heat treatment to achieve stronger crystalline structures. The choice of material depends on factors like mechanical requirements, environmental exposure, cost constraints, and whether the bolt will experience vibration, corrosion, or extreme temperatures during use.