Fasteners

 

 

 

Steel structure fasteners are bolt assemblies — matched bolts, nuts, and washers — manufactured to strict mechanical and dimensional standards for safety-critical connections in steel buildings, bridges, and transmission towers. Two connection types apply: bearing-type, where bolts bear against connected plates (secondary framing, purlins), and slip-critical, where pre-tensioned bolts clamp joint surfaces against reversal or fatigue loads (primary beam-to-column connections). Pre-tensioning is achieved via torque-control or twist-off bolts (F1852).

 

Standards include ASTM F3125 (A325/A490/F1852 heavy hex structural bolts), F1554 (anchor bolts), EN 14399, and GB/T 1228–1231. Grades range from 4.8 to 10.9/12.9. Coating must match grade and environment: hot-dip galvanizing for up to 8.8 (corrosion protection), dacromet/mechanical galvanizing for 10.9+ (hydrogen embrittlement prevention).

 

 

 

GNEE manufactures structural bolt assemblies to the four governing standards below. Each standard governs a specific regional market — grades are not interchangeable. Use this reference to match your project specification to the correct standard and grade.

 

Standard	Origin	Grade	Min. Tensile	Typical Application
ASTM F3125 A325	North America	—	120 ksi (827 MPa)	Bolted steel joints, building frames, bridges
ASTM F3125 A490	North America	—	150 ksi (1040 MPa)	High-strength primary connections, heavy trusses
ASTM F3125 F1852	North America	—	120 ksi (827 MPa)	Twist-off bolt for slip-critical connections
ASTM F1554	North America	36 / 55 / 105	60 / 75 / 125 ksi	Anchor bolts for foundation anchoring
EN 14399 HR	Europe	8.8 / 10.9	800 / 1040 MPa	European-standard structural bolting
EN 14399 HV	Europe	10.9	1040 MPa	Hex-socket assemblies for pre-tensioned joints
GB/T 1228–1231	China	8.8s / 10.9s	800 / 1040 MPa	Chinese-standard steel structures, bridges
ISO 898-1	International	4.8–12.9	400–1220 MPa	Mechanical property baseline for all grades

 

 

 

Selecting a structural fastener is a three-step decision: head style and drive method, material, then grade and surface treatment. Each step narrows the selection to match your connection type, load requirement, and service environment.

 

Head Styles & Drive Methods

 

In structural bolting, head style determines clamp load distribution and installation tooling. The six types below cover the majority of structural steel connections.

 

Head Style		Drive Method	Structural Application
Heavy Hex		Hydraulic torque wrench or impact gun	ASTM F3125 A325/A490 primary connections — wide bearing surface distributes clamp load across connected plies
Twist-Off (TC) F1852		Electric TC bolt gun; spline shears off at target pretension	Slip-critical and pre-tensioned connections — field-verifiable installation, no torque calibration needed
Anchor Bolt		Wrench or nut driver; cast-in or drilled-in setting	ASTM F1554 foundation anchoring — L-bend, J-bend, or headed configurations for column base plates
Socket Cap		Allen key (hex key)	Mechanical-grade connections, base plate fastening, and secondary structural members; suitable for applications where a compact cylindrical head with hex socket drive is preferred over a large external hex head
Countersunk		Phillips or hex socket	Architectural and pedestrian bridge connections where flush surface is required for aesthetics or clearance
Flange Bolt		Wrench or socket	Secondary structural connections — integrated flange distributes load without separate washer, faster installation

 

Material Reference

 

Structural fastener materials are selected by strength class and service environment. The four materials below cover structural steel applications from general framing to marine-grade connections.

 

Material	Standard Reference	Typical Grade	Service Environment
Carbon Steel	ASTM F3125 A325, ISO 898-1	4.8 / 8.8	General structural connections, indoor or coated for outdoor use. Low cost, high strength, requires coating
Alloy Steel	ASTM F3125 A490, ISO 898-1	10.9	High-strength primary connections, bridges, heavy trusses. Quenched & tempered; requires dacromet or mechanical galvanizing — no hot-dip galvanizing (hydrogen embrittlement risk)
Weathering Steel	ASTM F3125 A325 Type 3 / A490 Type 3	8.8 / 10.9 equiv.	Atmospheric corrosion resistance matching A588 weathering steel structures — forms protective oxide layer, no coating needed
Stainless Steel 304	ASTM F593, A2-70	A2-70	Outdoor, food, general corrosion service. Not recommended for chloride/marine exposure

 

Grade & Surface Treatment

 

The final step matches fastener grade and coating to the connection's load demand and environmental exposure. Grade determines tensile strength; surface treatment determines corrosion resistance and service life.

 

Coating	Suitable Grade	Environment	Note
Black / Plain	4.8–12.9	Indoor, protected structures	Lowest cost, no corrosion protection
Zinc-Plated	4.8–8.8	Indoor or mild outdoor	Thin coating, limited corrosion resistance
Hot-Dip Galvanizing	Up to 8.8	Outdoor, industrial, coastal	Heavy coating, 50+ years service life in most environments
Dacromet / Mechanical Galvanizing	10.9–12.9	Outdoor, high-strength applications	Hydrogen embrittlement safe for high-grade bolts
Weathering Type 3	8.8 / 10.9 equiv.	Atmospheric corrosion zones, A588 steel structures	Self-healing oxide layer, no coating needed

 

 

 

GNEE structural bolt assemblies have been exported to projects across Asia, the Middle East, South America, and Africa — supporting high-rise steel frames, bridge connections, power transmission towers, and industrial plants. Every shipment matches the exact standard, grade, and site-specific coating required by local codes and project specs.

 

 

Our steel structure fasteners are manufactured through a complete in-house production system, from raw steel to finished product. The main manufacturing process includes:

 

 

 

GNEE verifies quality at every production stage — not just at final inspection. Each stage carries its own standard, method, and acceptance criteria, with test reports (EN 10204 3.1) issued per batch.

 

Stage	QC Item	Standard	Method
Raw Material	Chemical composition, mechanical properties	ASTM F3125, GB/T 3098.1, EN 10204 3.1	Spectrometer, tensile per heat
Forming	Dimensions, surface cracks	ISO 4759-1	First-article + per 200 pcs, MT
Thread	Pitch diameter, thread fit	ISO 965, GB/T 197	Go/no-go gauge per ASTM F3125
Heat Treatment	Hardness, microstructure, tensile & proof load	ASTM F3125, ISO 898-1	HRC per batch, tensile per furnace, metallographic
Surface	Coating thickness, hydrogen embrittlement, thread fit	ASTM F1941, A153	Magnetic gauge, HE test 10.9+, go-gauge
Final	Proof load, tensile, wedge load, hardness, dimensions	ASTM F3125, EN 14399, ISO 898-1	EN 10204 3.1 MTC, samples 2 yrs, SGS/BV/TUV EN
Packaging	Labeling, moisture protection, segregation	Internal standard	VCI + desiccant, heat-number label, loading photos

 

 

 

 

 

Beyond standard catalog sizes, GNEE can manufacture non-standard fasteners to your drawings, samples, or technical requirements — with tolerance control and inspection records.

 

 

 

All steel structure fasteners are packed as matched assemblies (bolt + nut + washer), labeled for full traceability, and shipped with complete documentation to ensure smooth customs clearance and on-site installation.

 

Packaging & Shipping

Stage	Packaging Method	Protection
Bolting Assembly	Bolts, nuts, and washers are packed as matched sets per ASTM F3125 — each unit contains one bolt, one nut, and required washers, eliminating on-site mismatch	—
Inner Packaging	5-ply corrugated cartons (350–500 kg), woven bags (25–50 kg), or small bags (1–5 kg) — selected by product size and order volume	Galvanized and black surfaces packed with VCI bags and desiccant to prevent white rust and humidity corrosion during 30–45 day ocean transit
Special Protection	Threaded ends, twist-off splines, and anchor bolt bends are protected with plastic caps or wooden blocks to prevent transit damage	Weathering Type 3 surfaces packed with rust-inhibitor paper to preserve protective oxide layer
Palletizing & Loading	Cartons stacked on ISPM-15 heat-treated pallets (1,200×1,000mm or 1,100×1,100mm), shrink-wrapped and strapped for container optimization	—

Note: Each package is labeled with: product name, standard (ASTM F3125 / F1554 / GB), grade (A325 / A490 / 8.8 / 10.9), size (M), quantity, lot number, heat number, and destination project name.

 

Lead Time

Category	Standard Lead Time	Custom Lead Time
Standard sizes (M12–M36, A325/A490/8.8/10.9)	15–25 days	25–35 days (special coatings, custom packaging)
Non-standard sizes (M36–M64)	25–35 days	30–45 days (custom threading, bending, head style)

Note: Lead time is calculated from drawing confirmation and deposit receipt. Rush production is available upon request.

 

Shipping Terms & Documentation

Item	Detail
Incoterms	FOB (Tianjin), CIF, DDP
Shipping Methods	FCL (20'GP / 40'GP / 40'HQ), LCL for small orders, air freight for urgent projects
Export Documentation	Commercial invoice, packing list (carton-level breakdown), bill of lading (B/L), certificate of origin (CO)
Quality Documentation	EN 10204 3.1 MTR per batch, coating thickness report, third-party inspection certificate (SGS / BV / TÜV)
Customs Clearance	Full export documentation provided; third-party inspection by SGS, BV, or TÜV supported
Multi-Product Consolidation	Consolidate with structural steel members (beams, columns, trusses, purlins, bracing) to optimize logistics cost for full-project procurement

Note:Consolidated shipment with structural steel components is available to optimize logistics cost for full-project procurement.

 

 

 

As one of the most professional fasteners manufacturers and suppliers in China, we have world-leading production equipment and strong manufacturing capabilities. Please rest assured to buy customized fasteners at competitive price from our factory. For quotation, contact us now.

Countersunk Socket Head Cap Bolt, fasteners, Full Thread Hex Bolt