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Product Overview
Structural bolts are heavy-duty fasteners designed for steel-to-steel connections in load-bearing structures. They feature a heavy hex head, a short thread length, and a controlled shank diameter to provide consistent clamp load and shear strength. These bolts are manufactured to strict dimensional and mechanical property standards including ASTM A325, A490, and DIN 6914.
Zhejiang Chance & Union supplies structural bolts in carbon steel and alloy steel grades, with hot-dip galvanized, zinc-plated, or plain finishes. Each batch is tested for tensile strength, hardness, and elongation to ensure compliance with project specifications.
Key Engineering Features
- Heavy hex head: Larger bearing surface for high-torque tightening
- Short thread length: Reduced thread engagement area for improved shear resistance
- Controlled shank: Precision-diameter body for consistent fit in bolt holes
- Material grades: ASTM A325 (Type 1), A490, Grade 8.8 / 10.9 / 12.9 metric
- Coating options: Hot-dip galvanized, zinc plated, plain, Dacromet
Typical Specifications
Diameter rangeMetric and inch series available
Length rangeStandard and custom lengths
Thread class2A (UNC) · 6g (metric) · rolled threads
Material gradesASTM A325 · ASTM A490 · 8.8 · 10.9 · 12.9
Finish optionsHot-dip galvanized · zinc plated · plain · Dacromet
StandardsASTM A325 · ASTM A490 · DIN 6914 · ISO 7412
Production & Supply Chain
30,000 m²
Facility Area
80+
Cold Heading Units
800 t
Monthly Capacity
2,000 t
Warehouse Stock
Manufacturing Capability
- Multi-station cold headers for high-volume production
- CNC machining centers for precision dimensions
- Heat treatment facilities for grade-specific hardening
- Automated coating lines for consistent finish quality
- Support for both prototyping and mass production
Logistics & Inventory
- Permanent stock of 5,000+ specifications
- Storage capacity exceeding 2,000 tons
- 24-hour order processing
- 3-day rapid shipping for standard sizes
- Lead time for custom orders: 7–25 days
Quality Assurance & Testing
Testing Equipment
- Optical sorting for 100% dimensional inspection
- Salt spray test chamber (72-hour test)
- Tensile testing machine per ASTM E8
- Hardness tester per ASTM E18
Quality Standards
- ISO 9001 certified
- IATF 16949 certified
- Ex-factory pass rate: 99.9%
- ≤30-minute factory response time
Traceability
- Material test reports (MTR) with heat numbers
- Full traceability from raw material to finished product
- Batch-specific testing records
- Third-party inspection available
R&D & Engineering Support
With nearly 20 years of industry experience, our R&D team has developed over 1,000 custom fastener solutions for clients across 25 countries. We invest 5% of annual revenue into R&D, focusing on:
- Joint design analysis: Clamp load calculation, torque-tension correlation, and preload optimization
- Custom development: Non-standard head dimensions, thread configurations, and material specifications
- Prototyping services: Rapid sample production for fit and performance validation
- Coating advisory: Selection guidance based on corrosion resistance requirements and service life
Application Scenarios
- Structural steel construction: High-rise buildings, bridges, stadiums, and industrial facilities
- Infrastructure projects: Highway bridges, railway structures, and transmission towers
- Heavy equipment: Crane booms, excavator arms, and mining machinery frames
- Offshore & marine: Oil platform structures, shipbuilding, and port equipment
- Wind energy: Turbine tower flange connections and foundation bolting
Selection Guide for Structural Bolts
When specifying structural bolts for a project, consider these critical parameters:
- Grade selection: ASTM A325 for general structural applications; ASTM A490 for higher strength requirements; metric grades 8.8, 10.9, or 12.9 for international projects.
- Coating: Hot-dip galvanized for outdoor exposure and corrosion resistance; zinc plated for indoor applications; plain for painted or controlled environments.
- Thread length: Standard short thread for most structural connections; full thread (if specified) for certain applications.
- Washer compatibility: Structural bolts are typically used with hardened washers (F436 or equivalent) to distribute load under the nut.
- Standard compliance: Verify project specifications for ASTM, DIN, or ISO requirements.
Frequently Asked Questions
What is the difference between ASTM A325 and A490 structural bolts?
ASTM A325 is a medium-carbon steel bolt with a minimum tensile strength of 120 ksi (for diameters up to 1 inch) or 105 ksi (for larger diameters). ASTM A490 is an alloy steel bolt with a higher minimum tensile strength of 150 ksi, offering greater load capacity for heavy-duty connections. A490 bolts have higher hardness and require more careful installation.
What coatings are available for structural bolts and when should each be used?
Hot-dip galvanized coating provides the highest corrosion resistance, suitable for outdoor and marine environments. Zinc plating (electroplated) offers moderate corrosion protection for indoor applications. Dacromet provides superior salt spray resistance for demanding environments. Plain (uncoated) bolts are used in controlled environments where painting will be applied after installation.
How do you ensure the quality of structural bolts?
We perform 100% optical sorting for dimensional accuracy, plus tensile, hardness, and elongation tests per batch. Each batch is accompanied by material test reports (MTR) with heat numbers. Our ISO 9001 and IATF 16949 certified quality systems ensure full traceability and consistent product quality.
What is your typical lead time for structural bolts?
Standard sizes in stock can ship within 3 days. For custom diameters, lengths, or coatings, lead time is typically 7 to 25 days depending on order quantity and specification complexity. We support both small-batch and large-volume orders.
Can you produce structural bolts to non-standard specifications?
Yes. Our R&D team has developed over 1,000 custom fastener solutions. We can accommodate non-standard head dimensions, thread configurations, custom materials, and special coating requirements based on your project needs.
