Heavy Hex Structural Bolts (ASTM A325 / A490 / DIN 6914) – High Tensile Steel – Manufacturer Direct

Heavy Hex Structural Bolts: The Backbone of Steel Construction

At Handan Bolt, we engineer safety. Our Heavy Hex Structural Bolts are designed for the most demanding applications in civil engineering and industrial construction. Manufactured in our ISO-certified facility in Yongnian, China, these high-tensile fasteners are built to withstand immense shear and tensile loads. We supply steel fabricators and erectors worldwide with bolts that strictly adhere to ASTM and DIN standards.

What Defines a “Heavy Hex” Structural Bolt?

Unlike a standard hex bolt (DIN 931/933), a Structural Steel (Read more on Wikipedia) bolt features a larger, thicker head. This “Heavy Hex” design provides a wider bearing surface to distribute the clamping load effectively across the steel members, preventing the bolt head from crushing the steel or pulling through under extreme tension.

Product Standards and Specifications

We manufacture to the precise specifications listed in your requirements:

1. ASTM A325 (Type 1) / F3125 Grade A325

The industry standard for heavy hex structural bolts.

• Material: Medium carbon steel, quenched and tempered.
• Application: General structural steel connections in buildings and bridges.
• Strength: Minimum tensile strength of 120 ksi (for diameters up to 1 inch).

2. ASTM A490 (Type 1)

For applications requiring even greater strength.

• Material: Alloy steel, quenched and tempered.
• Application: Heavy industrial structures where higher loads are present.
• Note: These bolts are heat-treated to a higher hardness than A325 and require careful handling to avoid hydrogen embrittlement.

3. DIN 6914 (HV Bolts) / EN 14399

The metric standard for High-Strength Structural Bolting assemblies for preloading.

• Grade: 10.9 (High Tensile).
• System: Typically supplied as a set with DIN 6915 (Heavy Hex Nuts) and DIN 6916 (Hardened Washers).

Surface Treatments: Durability vs. Performance

Structural bolts must resist environmental corrosion while maintaining proper tensioning characteristics:

• Black (Plain/Oiled): The standard finish for indoor structures or A490 bolts. The oil coating ensures the nut runs down smoothly to achieve the correct pre-load tension.
• Hot Dip Galvanized (HDG): Essential for outdoor bridges and infrastructure. Our HDG coating (40-60 microns) provides cathodic protection against rust. *Note: We stick to strict protocols to prevent hydrogen embrittlement during the galvanizing of high-strength bolts.*

Critical Applications

Our Heavy Hex Structural Bolts are the fastener of choice for:

• Steel Frame Buildings: Columns and beam connections in skyscrapers.
• Infrastructure: Highway bridges, railway trusses, and overhead sign structures.
• Energy Sector: Wind turbine towers and power plant transmission structures.
• Mining Equipment: Heavy crushers and conveyor systems subject to vibration.

Quality Control: Safety First

We don’t just sell bolts; we sell structural integrity.

Tensile Testing: Every heat lot is tested to ensure it meets the minimum yield and tensile strength requirements.

Impact Testing: Charpy V-Notch testing is performed to ensure the bolts maintain ductility in cold weather.

Traceability: All our structural bolts come with full Mill Test Certificates (MTC) traceable to the raw material.

Get a Project Quote

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Need a price list for A325 or DIN 6914 bolts?

Please click here to Contact Our Engineering Team for a Quote. We support large project tenders.