The Hot Dip Galvanized Double End Stud Bolt (also known as an HDG tap-end stud, double-ended threaded stud bolt, or DIN 938/939 galvanized stud) is a heavy-duty industrial connection fastener specifically designed for severe outdoor atmospheric exposure, electric utility substations, overhead power transmission lines, and structural steel bridge assemblies. Engineered with external threads at both ends separated by an unthreaded center shank and coated with a thick metallurgical zinc layer (45–85 µm), this fastener provides self-healing sacrificial rust protection in compliance with global ISO standards.
Technical Specifications of Hot Dip Galvanized Double End Stud Bolt
We manufacture hot-dip galvanized double end studs in Class 4.8 low-carbon steel for standard power line fittings and Grade 8.8 quenched and tempered alloy steel for heavy structural dynamic loads. Threads are specially undercut before galvanizing or nuts are over-tapped to ensure smooth, hand-tightened assembly without stripping the protective zinc coating.
| Parameter | Class 4.8 HDG Double End Stud | Grade 8.8 High Tensile HDG Stud |
|---|---|---|
| Core Material Grade | Low Carbon Steel (Q195 / Q235B) | Medium Carbon Steel (45#) / 40Cr Steel |
| Tensile Strength (Min) | 400 N/mm² (400 MPa) | 800 N/mm² (800 MPa) |
| HDG Coating Standard | BS EN ISO 1461 / ASTM A153 Class C | BS EN ISO 1461 / ASTM A153 Class C |
| Average Coating Thickness | 45 µm – 65 µm (300–450 g/m²) | 65 µm – 85 µm (450–600 g/m²) |
| Salt Spray Endurance | 500 Hours Neutral Salt Spray (NSS) | 1000 Hours Neutral Salt Spray (NSS) |
Hot-Dip Galvanizing and Production Process for Double End Stud Bolt
At our manufacturing plant in Handan, China, double end stud bolts undergo precision forging, dual-end thread rolling, molten zinc dipping, and high-speed centrifugation:
- Precision Cutting & Dual-End Thread Rolling: Carbon steel rods are cut to exact lengths, and 6g/6h pitch threads are cold-rolled on both ends to ensure fatigue resistance under cyclic vibration.
- Thermal Quenching & Tempering (Grade 8.8): High-strength Grade 8.8 studs are heat-treated in continuous mesh-belt furnaces to achieve homogeneous 800 MPa tensile strength.
- Molten Zinc Dipping (450°C): Studs are immersed in molten pure zinc, forming a multi-layer zinc-iron alloy metallurgical bond that resists mechanical abrasion and impact.
- Centrifugal Spin Drying & Thread Clearing: High-speed centrifugal spin drying immediately clears excess molten zinc from thread roots, ensuring smooth fit with over-tapped HDG hex nuts.
Heavy Duty Applications of Hot Dip Galvanized Double End Stud Bolt
Due to their superior outdoor weatherability and pre-assembled nut design, hot-dip galvanized double end studs serve as critical structural fasteners in major infrastructure projects:
- Overhead Power Lines & Substation Structures: Fastening strain clamp assemblies, cross-arm brackets, insulator strings, and steel tower bases.
- Highway Guardrails & Traffic Infrastructure: Securing W-beam guardrail posts, bridge expansion joints, and highway sign gantries.
- Coastal Pipelines, Valves & Flanges: Connecting outdoor pipeline flanges, water treatment valves, and petrochemical storage vessel covers.
Quality Assurance and Export Packaging for Hot Dip Galvanized Double End Stud Bolt
Handan YiHao Fastener enforces rigorous Quality Assurance (QA) standards for all overseas export orders. Testing procedures include magnetic coating thickness gauge checks across multiple points, dual-end thread ring/plug gauge fit tests with over-tapped nuts, tensile load testing, and neutral salt spray validation.
All export items are packed in heavy-duty 25kg inner cartons, neatly stacked on ISPM 15 compliant fumigated wooden pallets, and wrapped in protective stretch film to ensure safe ocean transport.
Request Factory Direct Pricing for Hot Dip Galvanized Double End Stud Bolts
Looking for a trusted manufacturer in Handan, China for Class 4.8 or Grade 8.8 hot-dip galvanized double end stud bolts (DIN 938 / DIN 939 / GB 898)? Contact Handan YiHao Fastener today for technical datasheets, pre-assembled over-tapped HDG nuts, coating test reports, and direct bulk export quotes.
