ASTM A325 Heavy Hex Structural Bolt Carbon Steel High Tensile Bolt

Engineered for general heavy-duty steel structure connection projects, ASTM A325 Heavy Hex Structural Bolt Carbon Steel High Tensile Bolt is a heat-treated medium carbon steel fastener compliant with official ASTM industry standards. This series of structural bolts features balanced mechanical toughness and stable tensile performance, serving as the most widely adopted standard fastener for North American steel construction. Manufactured and supplied by Ningbo Gangtong Zheli Fasteners Co., Ltd., the product covers complete UNC inch specifications and supports diversified surface treatment solutions. Every production procedure follows standardized industrial requirements, with strict raw material screening and finished product testing to ensure long-term structural connection stability in various civil and industrial engineering scenarios.

Main Technical Parameters

Item	Specification Details
Executive Standard	ASTM A325 Type 1 / Type 3, F3125 Standard System
Production Material	Premium Medium Carbon Steel, Integral Quenched & Tempered Treatment
Thread Form	UNC American Standard Coarse Thread, Standard Half Thread Design
Available Size Range	1/2”, 5/8”, 3/4”, 7/8”, 1”, 1-1/8”, 1-1/4”, 1-3/8”, 1-1/2”
Mechanical Properties	Minimum Tensile Strength 120ksi, Minimum Yield Strength 92ksi
Thread Tolerance Grade	Class 2A High-precision External Thread Tolerance

Surface Treatment Options

Different from ultra-high-strength alloy steel bolts, medium-carbon A325 structural bolts allow multiple safe and reliable surface finishing processes without hydrogen embrittlement risks, adapting to indoor, outdoor, coastal and high-humidity working environments. Each coating process is independently produced in batches to guarantee uniform surface texture and stable anti-corrosion performance. Flexible finishing selection effectively meets differentiated engineering budget and service life requirements, making ASTM A325 Heavy Hex Structural Bolt Carbon Steel High Tensile Bolt highly adaptable for diverse construction scenarios.

Surface Treatment	Applicable Working Environment	Core Performance & Engineering Features
Black Oxide & Phosphating	Indoor steel workshops, closed steel frame structures, dry working conditions	Forms compact protective film on the surface with low friction coefficient, ensuring smooth high-torque assembly. Matched with anti-rust oil for effective short-term rust prevention, cost-effective for indoor conventional projects.
Hot Dip Galvanized (HDG)	Outdoor buildings, highway bridges, coastal salt spray areas, open-air steel structures	Features thick and uniform zinc coating with excellent salt spray and oxidation resistance. Completely compliant with ASTM standards, specially equipped with over-tapped nuts to solve assembly obstacles caused by thick zinc layer.
Dacromet Zinc Flake Coating	High humidity, mild chemical corrosion, severe coastal weather environments	No hydrogen embrittlement hazard, ultra-stable anti-corrosion performance, longer service life than traditional galvanizing. Ideal for high-demand outdoor engineering with strict durability requirements.

Core Performance Advantages

This series of structural bolts adopts carefully proportioned medium carbon steel raw materials with pure internal texture and stable chemical composition. After integral quenching and tempering heat treatment, the bolt achieves perfect balance of hardness and toughness, avoiding brittle fracture or deformation under long-term alternating loads. The optimized heavy hex head structure enlarges the stress-bearing area, evenly dispersing tightening torque during installation and preventing slippage or cracking. Precision thread rolling technology ensures accurate tooth pitch and smooth engagement, delivering stable locking force for long-term structural operation. With excellent comprehensive performance and cost advantages, ASTM A325 Heavy Hex Structural Bolt Carbon Steel High Tensile Bolt has become the preferred conventional fastener for global steel structure engineering.

Application Fields

With reliable load-bearing capacity and diverse anti-corrosion options, standard carbon steel structural bolts are widely used in various civil construction and industrial manufacturing fields. Covering standard steel structure workshops, high-rise building steel frames, highway and railway steel bridges, power transmission tower supports, port mechanical equipment and municipal engineering steel structures, these bolts undertake key connection and load-bearing tasks. For most conventional steel structure projects that do not require ultra-high strength but demand stable quality and cost control, engineering designers always prioritizeASTM A325 Heavy Hex Structural Bolt Carbon Steel High Tensile Bolt for structural node fixation.

Quality Inspection Standard

We implement full-process quality supervision and multi-dimensional batch inspection mechanisms for all finished structural bolts. Relying on independent professional testing laboratories, each production batch undergoes systematic testing including chemical composition analysis, Rockwell hardness detection, ultimate tensile fracture test, yield strength verification and thread dimension calibration. All inspection data is recorded in detail and archived permanently to support customer quality traceability and engineering audit. Unqualified products are completely screened out to ensure zero defective delivery, and all test indicators fully verify the stable quality of ASTM A325 Heavy Hex Structural Bolt Carbon Steel High Tensile Bolt.

Packing & Shipment

Targeting the long-distance cross-border transportation characteristics of engineering fasteners, we adopt standardized export-grade protective packaging solutions suitable for all UNC specifications of 1/2”, 3/4”, 1”, 1-1/2” and other common sizes. Finished bolts are strictly sorted by size, thread type and surface treatment process to avoid mixed packaging of different products. Each product is wrapped with waterproof and moisture-proof inner bags firstly, then placed into thickened five-layer reinforced cartons for anti-collision protection. Bulk orders adopt professional pallet packaging with stretch film winding and strapping reinforcement to resist extrusion and vibration during sea transportation. Custom brand labels, batch numbers and specification marks are supported. Complete customs clearance documents and packing lists are prepared in advance to fully protect the intact state of ASTM A325 Heavy Hex Structural Bolt Carbon Steel High Tensile Bolt during transshipment and ocean delivery.

Why Choose Ningbo Gangtong Zheli Fasteners Co., Ltd.

As a professional manufacturer focusing on ASTM standard structural fasteners, our factory owns complete independent production lines, dedicated heat treatment equipment and standardized quality inspection systems. With years of rich experience in high-strength bolt production and export, we are deeply familiar with North American engineering procurement standards and on-site construction requirements. From raw material incoming inspection, precision processing and heat treatment strengthening to surface finishing and finished product packaging, every link implements standardized process control to eliminate batch quality differences. We support personalized customization, complete COA material certificate provision and professional pre-sales technical guidance. With stable quality and high cost performance, ASTM A325 Heavy Hex Structural Bolt Carbon Steel High Tensile Bolt has won long-term recognition from global engineering customers.

FAQ

Q1: What is the core difference between ASTM A325 and ASTM A490 structural bolts?

A1: ASTM A325 is medium carbon steel structural bolt with moderate strength and excellent toughness, supporting hot dip galvanizing and various surface treatments without hydrogen embrittlement risks, suitable for most conventional steel structures. ASTM A490 belongs to ultra-high strength alloy steel bolt with higher tensile performance, but hot dip galvanizing is strictly prohibited. A325 features higher cost performance and wider application range in general engineering projects.

Q2: What is the difference between A325 Type 1 and Type 3?

A2: Type 1 is conventional medium carbon steel type, the most mainstream specification in the market, suitable for most indoor and outdoor conventional steel structure projects. Type 3 is weathering steel type, with stronger atmospheric corrosion resistance, specially customized for harsh outdoor atmospheric environments and long-term exposed structural engineering.

Q3: Can hot-dip galvanized A325 bolts be matched with standard nuts?

A3: Not applicable. Considering the thick zinc coating of hot-dip galvanized bolts, we will support matched over-tapped heavy hex nuts to ensure smooth on-site assembly and effective locking, avoiding thread jamming and assembly failure caused by zinc layer thickness.

Q4: What surface treatments are available for ASTM A325 bolts?

A4: Three mainstream compliant treatments are available: black oxide for indoor dry environments, hot dip galvanizing for outdoor bridge and coastal projects, and Dacromet zinc flake coating for high-corrosion and high-humidity scenarios. All processes comply with ASTM standard specifications and pass professional engineering inspections.

Q5: Can official batch quality certificates be provided?

A5: Yes. We can provide complete official COA material test certificates for each shipment, including raw material chemical composition, mechanical property test data, hardness detection results and batch production qualification information, fully meeting international engineering inspection and customs clearance requirements.