螺栓类型和应用指南：完整技术参考

Hex bolts (hex head bolts) are the most common, accounting for 60% of construction fastener use. They provide high clamping force and are easy to install with standard wrenches. Carriage bolts are used in wood and timber construction where a smooth finished appearance is needed.

Grade 8.8 bolts have minimum tensile strength of 800 MPa, suitable for most construction applications. Grade 10.9 bolts have 1000 MPa tensile strength and are used for high-stress applications like bridge construction and heavy machinery. Always consult structural engineer specifications for your application.

Use stainless steel (A2/A4 or 304/316) in coastal environments, chemical plants, food processing facilities, and applications where corrosion resistance is critical. Stainless steel costs 3-5x more than carbon steel but provides superior corrosion resistance. For inland construction in dry environments, hot-dip galvanized carbon steel bolts are typically sufficient.

General rule: bolt length should be 2-3x the diameter for proper engagement. For a M20 bolt, minimum embedment depth is 40-60mm. Always follow the manufacturer's specifications for your specific connection design.

Bolts should typically not be reused in critical structural connections. Thread damage, bending, or coating wear during removal can significantly reduce bolt strength. For non-structural applications, inspect carefully and replace if any damage is visible.