A325 Carbon Steel Hex Bolts | Structural Fasteners

Product Introduction
ASTM A325 heavy hex structural bolts in carbon steel, manufactured to ASME B18.2.1 dimensions and available across a comprehensive range of metric property classes — 4.8, 6.8, 8.8, 10.9, and 12.9. The product line covers both standard mechanical assemblies and high-load tension joints where controlled preload is specified. Multiple surface finishes are available to match in-service environmental conditions.

Material & Mechanical Properties
Forged from medium carbon steel and heat-treated by quenching and tempering where required by the property class. Charpy impact values, proof load, and tensile strength per ISO 898-1 are certified by heat lot, with mill test reports supplied upon request. Classes 8.8 and 10.9 align with the mechanical requirements historically associated with A325 Type 1 bolting.

Geometry & Thread Form
The heavy hexagonal head provides a wrench-ready bearing surface for open-end, box, or power sockets, reducing radial tool slip during torque cycles. Coarse pitch metric thread per ISO 724 speeds assembly, lowers the risk of cross-threading in structural steel, and resists stripping under vibration better than fine-pitch alternatives.

Corrosion Protection
Zinc electroplated per ASTM B633 (Fe/Zn, 5–8 µm) is the standard finish, offering effective red rust resistance for sheltered outdoor and indoor environments. Hot-dip galvanized, zinc-nickel, and other engineered coating systems are specified for higher corrosivity categories (C3–C5 per ISO 9223).

Application Suitability
Steel-to-steel connections in commercial construction, pre-engineered metal buildings, heavy machinery frames, bridge secondary members, and industrial bracing where reliable clamp force and long-term durability are required.

Technical Parameters