HIGH STRENGTH LARGE HEXAGON HEAD BOLT FOR STEEL STRUCTURES — PRODUCT INTRODUCTION

The high strength large hexagon head bolt for steel structures is a critical fastener for steel structure connections. Designed and manufactured according to national standard GB/T 1228, it must be used together with GB/T 1229 high strength large hexagon nuts and GB/T 1230 high strength washers to form a bolt connection assembly. By applying a specified pre-tension force, it generates strong friction or bearing capacity between connection plates, thereby achieving high stiffness, high load-bearing friction-type or bearing-type connections. The bolt performance grades are primarily 10.9S and 8.8S, with specifications ranging from M12 to M30 and above. It is widely used in building, bridge, tower and mast steel structure engineering, and is a core component ensuring structural safety and service life.

I. PRODUCT FEATURES

LARGE HEXAGON HEAD DESIGN: The head’s across-flats dimension is larger than that of ordinary hexagon heads, increasing wrench contact area. It resists slipping during tightening, facilitates applying and controlling high torque, and ensures stable pre-tension force.

HIGH STRENGTH MATERIAL AND PERFORMANCE: Manufactured from high-quality alloy steel or medium carbon steel through quenching and tempering treatment, Grade 10.9S achieves tensile strength above 1040 MPa. It possesses high strength and high yield ratio, capable of withstanding enormous pre-tightening force and working loads.

STRICT TORQUE COEFFICIENT CONTROL: The standard deviation of torque coefficient for connection assemblies of the same batch is strictly regulated. This ensures that accurate and uniform pre-tension force can be obtained with small dispersion by controlling torque when using the torque method for construction.

CONNECTION ASSEMBLY SUPPLIED AS COMPLETE SET: Bolts, nuts and washers are factory-supplied as matched sets by batch. The performance, dimensions and surface treatment condition of the three components are mutually matched and must not be arbitrarily interchanged, ensuring the reliability of the overall mechanical characteristics of the connection assembly.

DIVERSIFIED SURFACE PROTECTION: Surface treatment options include blackening, phosphating, galvanizing (note: hydrogen embrittlement risk requires dehydrogenation treatment), Dacromet or hot-dip galvanizing, etc., to adapt to durability requirements in different corrosive environments.

II. PRODUCT ADVANTAGES

CONVENIENT CONSTRUCTION AND INSPECTION: Use calibrated torque wrenches for tightening. After construction completion, pre-tension force can be conveniently verified using the “turn-of-nut method” or “loosening check torque method.” Quality is traceable and easy to control, superior to twist-off type bolts that rely on broken tail marks.

WIDE RANGE OF APPLICATION: Good adaptability to connection plate thickness deviation and hole wall clearance, suitable for various field conditions. Applicable to both friction-type and bearing-type connections.

GOOD REUSABILITY: After evaluation and re-treatment, some large hexagon head bolts can be reused in non-critical locations; during installation, they can be conveniently loosened for adjustment without being scrapped due to tail fracture.

FATIGUE AND VIBRATION RESISTANCE: Through accurate pre-tension force, high friction is formed on connection surfaces, effectively reducing stress amplitude variation and fretting wear. Joint fatigue performance is superior, suitable for steel structures subjected to dynamic loads and seismic action.

HIGH DEGREE OF STANDARDIZATION, CONVENIENT PROCUREMENT MANAGEMENT: Fully compliant with domestic GB standard system, strong component interchangeability, clear quality basis, convenient acceptance, and abundant market supply.

III. APPLICATION SCOPE

INDUSTRIAL AND CIVIL BUILDING STEEL STRUCTURES: Rigid connection nodes of steel columns and steel beams in high-rise and super high-rise buildings, main connection areas of large-span factory buildings, stadiums, exhibition centers and other spatial structures.

BRIDGE ENGINEERING: Member splicing and cross beam connections of highway and railway steel bridges, especially critical joints bearing heavy vehicle loads and wind loads.

TOWER, MAST AND HIGH-RISE STRUCTURES: Transmission towers, communication towers, wind power tower flange connections, chimney steel frameworks, etc., capable of withstanding reciprocating loads and fatigue stress.

LIFTING, TRANSPORT AND HEAVY EQUIPMENT: Connection of main beams and end beams for overhead traveling cranes and gantry cranes, steel structure body fastening for large excavators and port machinery.

METALLURGY, CHEMICAL AND OFFSHORE ENGINEERING: Steelmaking plant buildings, offshore platform module connections, and some steel structure nodes requiring pressure bearing or weather resistance, where bolts with appropriate surface protection can be selected according to environment.