| Standard | DIN EN 14399 · ISO 898-1 · ASTM A325 · A490 / A307 |
|---|---|
| Material | 35CrMo / 42CrMo / Alloy Steel |
| Strength Grade | 8.8 / 10.9 / 12.9 / A325 / A490 |
| Size Range | M12-M64 |
| Surface Treatment | Hot Dip Galvanized / Zinc Flake Coating |
Product Description
Heavy structural hex head bolts are supplied for bridges, steel frames, towers and heavy structural joints where high-strength bolting and controlled bearing geometry are required. Material options include 35CrMo, 42CrMo and alloy steel, with 8.8 / 10.9 / 12.9 and ASTM A325 / A490 references.
These bolts are different from general-purpose hex bolts because structural applications may require heavy hex geometry, compatible nuts and washers, lot traceability, preloading procedure, rotational capacity testing and coating control. Standards include ASTM A325 / A490 / A307, ISO 898-1 and DIN EN 14399 depending on the project system.
Hot-dip galvanized coating is common for outdoor bridge and steelwork corrosion protection, while zinc flake coating can support corrosion performance with controlled coating thickness. Final selection should confirm bolt grade, nut grade, washer type, thread length, grip range and installation method.
| Product type | Heavy structural hex head bolts |
|---|---|
| Standards | ASTM A325 / A490 / A307, ISO 898-1, DIN EN 14399 |
| Material | 35CrMo / 42CrMo / Alloy Steel |
| Strength grade | 8.8 / 10.9 / 12.9 / A325 / A490 |
| Size range | M12-M64 |
| Common models | M20 x 70, M22 x 80, M24 x 90, M30 x 120, M36 x 150 |
| Thread type | Structural thread length by standard or drawing |
| Surface finish | Hot-dip galvanized / Zinc flake coating |
| Documentation | MTC, CoC, lot traceability and inspection report on request |
| Parameter | 1 | 1/2 | 1-1/8 | 1-1/4 | 1-3/8 | 1-1/2 | 3/4 | 5/8 | 7/8 |
|---|---|---|---|---|---|---|---|---|---|
| P | 8 | 13 | 7 | 7 | 6 | 6 | 10 | 11 | 9 |
| ds/max | 1.022 | 0.515 | 1.149 | 1.277 | 1.404 | 1.531 | 0.768 | 0.642 | 0.895 |
| ds/min | 0.976 | 0.482 | 1.098 | 1.223 | 1.345 | 1.47 | 0.729 | 0.605 | 0.852 |
| k/max | 0.627 | 0.323 | 0.718 | 0.813 | 0.878 | 0.974 | 0.483 | 0.403 | 0.563 |
| k/min | 0.591 | 0.302 | 0.658 | 0.749 | 0.81 | 0.902 | 0.455 | 0.378 | 0.531 |
| s/max | 1.625 | 0.875 | 1.812 | 2 | 2.188 | 2.375 | 1.25 | 1.062 | 1.438 |
| s/min | 1.575 | 0.85 | 1.756 | 1.938 | 2.119 | 2.3 | 1.212 | 1.031 | 1.394 |
| r/max | 0.093 | 0.031 | 0.093 | 0.093 | 0.093 | 0.093 | 0.062 | 0.062 | 0.062 |
| r/min | 0.062 | 0.009 | 0.062 | 0.062 | 0.062 | 0.062 | 0.021 | 0.021 | 0.031 |
Selection
A325 / A490 and EN 14399 structural bolts are used for bridge splice plates, steel frame joints and heavy construction connections. Common RFQs include M20 x 70, M24 x 90 and M30 x 120.
Construction fasteners10.9 / 12.9 structural bolts with HDG or zinc flake coating can be specified for towers, platforms and outdoor steelwork where corrosion protection and traceability are required.
Power generation fastenersHeavy structural bolts support selected railway bridges, station steelwork and transit infrastructure. Confirm whether the project uses ASTM, EN 14399 or metric ISO bolting systems.
Railway fastenersAssembly
Manufacturing
See how heated alloy-steel blanks are die forged and learn which dimensions, inspections and downstream processes must be confirmed for a finished bolt.
Watch the hot forging video and read the technical guide →FAQ
It is a high-strength structural bolt used in steel connections, usually with specified nut and washer assemblies, lot traceability and installation requirements. It should not be treated as a generic hex bolt.
A490 bolts have higher strength than A325 bolts. The correct grade depends on the structural design, connection type, coating rules and project specification.
Many A325 and metric structural bolts can be HDG coated when permitted by the standard. A490 galvanizing has restrictions, so coating selection must follow the project specification.
Common RFQ models include M20 x 70, M22 x 80, M24 x 90, M30 x 120 and M36 x 150. Final length and thread length should follow the steel connection drawing.
Yes. Heavy structural bolts can be supplied with compatible structural nuts and hardened washers when the required assembly standard is confirmed.
Send your standard, grade, diameter, length, coating, nut/washer requirement, testing scope and lot traceability needs. Our team can quote structural bolting assemblies for bridge and steelwork projects.
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