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Industry-leading high-strength serrated flange bolts engineered for demanding structural and construction applications.
A serrated flange bolt is a specialized high-strength fastener featuring an integrated flange with serrated (toothed) teeth on its bearing surface. When tightened, the serrations bite into the mating surface, creating a powerful mechanical lock that dramatically resists loosening caused by vibration, dynamic loads, and thermal cycling โ challenges that are omnipresent in modern construction environments.
Unlike conventional hex bolts that require separate washers, the serrated flange bolt combines the bolt and locking washer into a single component. This not only simplifies the assembly process but also distributes the clamping load over a larger surface area, reducing the risk of surface damage and joint failure in structural steel connections, precast concrete anchoring, and curtain wall systems.
The serrations on the flange underside generate friction forces that are 30โ40% greater than smooth-flange alternatives, making them the preferred fastener for seismic-resistant structures, heavy-load bridges, industrial steel frames, and any application where joint integrity under dynamic stress is non-negotiable.
Manufactured to DIN6921 standard, Zhongli's serrated flange bolts are available in Grade 8.8 and Grade 10.9 with surface finishes including black oxide, zinc plated, and hot-dip galvanized. Diameters range from M10 to M48, accommodating virtually every structural construction requirement.
Serrated teeth mechanically grip the joint surface, preventing bolt loosening under continuous vibration and dynamic loading โ critical for bridges, machinery platforms, and seismic zones.
The enlarged flange distributes clamping force across a wider bearing area, eliminating the need for a separate washer and reducing component count in structural assemblies.
Grade 8.8 and 10.9 options provide tensile strengths of 800 MPa and 1000 MPa respectively, meeting the most demanding structural load requirements in modern construction.
Available in black oxide, electro zinc plated, and hot-dip galvanized (HDG) coatings to meet corrosion resistance requirements in indoor, outdoor, and marine construction environments.
Diameters from M10 to M48 with unlimited length options cover light-frame steel, heavy structural steel, and precast concrete connection applications without compromise.
Manufactured to DIN6921, ISO4014, ISO4017, and ANSI B18.2.1 standards with ISO9001, EN15048, EN14399, and CE certifications ensuring global project compliance.
The serrated flange bolt market is evolving rapidly alongside global infrastructure investment and industrial modernization.
The global construction fasteners market was valued at over USD 18 billion in 2023 and is projected to grow at a CAGR of approximately 5.2% through 2030, driven by surging infrastructure investment in Asia-Pacific, the Middle East, and North America. Within this landscape, serrated flange bolts represent one of the fastest-growing sub-segments, owing to their superior vibration resistance and simplified installation workflow.
In the commercial construction sector, the shift toward prefabricated steel structures and modular buildings has significantly increased demand for high-performance flange bolts. These structures rely heavily on precise, repeatable joint clamping โ exactly where serrated flange bolts outperform traditional hex bolt-and-washer assemblies by ensuring consistent friction coefficients and reducing assembly errors on-site.
The energy sector โ particularly wind turbine tower construction and solar farm mounting systems โ has emerged as a major growth driver. Wind turbine towers subject fasteners to millions of fatigue cycles annually; serrated flange bolts' inherent anti-loosening mechanism makes them the de facto standard for tower flange connections in IEC 61400-compliant installations worldwide.
Infrastructure renewal programs in Europe and North America, combined with China's Belt and Road Initiative driving construction activity across Southeast Asia, Africa, and Central Asia, are creating unprecedented export opportunities for Chinese high-strength fastener manufacturers. Ningbo Zhongli Bolts Manufacturing Co., Ltd. is strategically positioned to serve these markets with competitive pricing, ISO9001-certified quality, and rapid delivery capabilities.
Industry 4.0 is transforming fastener installation. Smart torque wrenches with IoT connectivity now log tightening data for every bolt in critical structures, and serrated flange bolts' predictable friction behavior makes them ideal for digital torque management systems used in high-rise construction and bridge engineering.
Sustainability mandates are pushing architects and engineers to specify longer-service-life fasteners that reduce maintenance frequency. Hot-dip galvanized serrated flange bolts with 50+ year corrosion protection are increasingly specified in LEED-certified and BREEAM-rated construction projects globally.
Growing awareness of seismic risk in emerging markets โ Turkey, Japan, Southeast Asia, and the Western US โ is driving adoption of vibration-resistant fastening systems. Serrated flange bolts are increasingly specified in seismic design categories C through F under ASCE 7 and Eurocode 8 frameworks.
With global wind capacity expected to triple by 2030, the demand for high-grade serrated flange bolts in tower construction, nacelle assembly, and foundation anchor bolt systems is set to accelerate significantly, creating a long-term structural demand driver for Grade 10.9 and 12.9 flange fasteners.
Post-pandemic supply chain restructuring has reinforced China's position as the world's primary high-strength fastener manufacturing hub. Ningbo โ home to Zhongli Bolts โ is one of China's premier fastener manufacturing clusters, offering unmatched scale, technical capability, and export logistics infrastructure.
From skyscrapers to wind farms, serrated flange bolts deliver unmatched joint integrity across the full spectrum of construction applications.
In multi-story steel frame buildings, serrated flange bolts are used for beam-to-column connections, moment frame joints, and base plate anchoring. Their anti-loosening serrations ensure joint integrity throughout the building's service life, even under wind-induced sway and occupancy vibration loads.
Bridge girder connections, expansion joint hardware, and bearing plate assemblies are subject to millions of fatigue cycles from traffic loading. Grade 10.9 serrated flange bolts specified to EN14399 provide the slip-critical joint performance required by bridge design codes including AASHTO LRFD and Eurocode 3.
Tower flange connections in onshore and offshore wind turbines require fasteners capable of withstanding billions of fatigue cycles over a 25-year design life. Serrated flange bolts in Grade 10.9 with hot-dip galvanized coating are the standard specification for IEC 61400-compliant tower flange bolting in global wind projects.
Chemical plants, oil refineries, and power stations rely on serrated flange bolts for equipment base frames, pipe rack structures, and pressure vessel supports. The vibration-resistant locking mechanism prevents costly unplanned maintenance shutdowns in 24/7 production environments.
Utility-scale solar installations use thousands of serrated flange bolts to secure panel mounting rails to driven piles and ground screws. The self-locking feature eliminates the need for thread-locking compounds, reducing installation cost and enabling faster deployment across large solar farm footprints.
Glass curtain wall systems and aluminum composite faรงades use serrated flange bolts to attach sub-frame brackets to the primary structural frame. The enlarged flange provides superior pull-through resistance in thin-section aluminum extrusions, while serrations prevent bracket rotation under wind pressure cycling.
Rail track fastening systems, overhead line equipment masts, and station canopy structures all utilize serrated flange bolts where vibration from passing trains would rapidly loosen conventional fasteners. High-speed rail projects in Europe and Asia specify Grade 10.9 HDG flange bolts for critical track-structure interfaces.
Jetty structures, port cranes, and offshore platform topsides operate in highly corrosive marine environments. Hot-dip galvanized serrated flange bolts with 85+ ฮผm zinc coating provide decades of corrosion protection while maintaining joint integrity under wave-induced dynamic loading and tidal movement.
Ningbo Zhongli Bolts Manufacturing Co., Ltd. founded in 2003, is a professional manufacturer of high-strength fasteners in different specifications for various models, which is covering an area of about 10,000 square meters, registered capital of 1,500,000 RMB, with the total annual productivity of 8,000 tons per year. The company has set up several sales branches in different provinces in China. Meanwhile, the company's products are exported to Europe, USA, Middle East, Africa, Southeast Asia and other regions. The company has strong technical ability, complete testing equipments and a variety of fully automatic multi-station cold and hot heading machines, so as to provide you with reliable and high quality products.
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Our main products ZYL brand fasteners include structural hex bolts ASTM A325 type 1, A490, hex head bolts DIN931, DIN933, EN14399, DIN6914, ISO4014, ISO4017 Gr8.8 Gr10.9 Gr12.9, ANSI B18.2.1 UNC and UNF Gr5, Gr8, fine pitch hex bolts DIN960, DIN961 Gr8.8 Gr10.9 Gr12.9, hex socket cap screws DIN912, ISO4762 Gr8.8 Gr10.9 Gr12.9 with surface Black, Zinc plated, Hot dip galvanized. Diameters from M10 to M48, length no limited. Hex Flange bolts DIN6921 Gr8.8 Gr10.9 with serration, thread rod A193 B7 long sizes and short sizes with 2H nuts, stud bolts. We also can supply hex nuts DIN934, DIN6915, plain washers DIN125, DIN126, DIN6916, spring washers DIN127 with Black, Zinc plated and Hot dip galvanized surface.
Our physical and mechanical test results can reach to ISO898-1 for bolts and ISO898-2 for nuts.
Through scientific management, Ningbo Zhongli Bolts Manufacturing Co., Ltd. obtained ISO9001 certificate of Quality Management System. Quality is the most important for us. We have strict production and inspection equipments to support this point.
We hope to establish business relationship with all over the world, and our business can bring in mutual benefits for both parties.
Every serrated flange bolt undergoes a rigorous 8-stage manufacturing process to ensure dimensional accuracy and mechanical performance.
State-of-the-art manufacturing equipment ensures every serrated flange bolt meets the highest quality standards.
A Professional Sales and Technical Team with More Than 20 Years History.
We Have Our Own Testing Equipment and Laboratory, Our Products Have Initial Inspection, Patrol Inspection, And Final Inspection.
Our Factory Has Its Own Cold Forged, Hot Forged, And Heat Treatment Equipment.
Standard Fasteners in Stock, Non-standard Fasteners Can Be Customized.
We Have Passed ISO 9001, EN 15048, EN 14399, AD2000 and CE Certificates.
We hope to establish business relationship with all over the world, and our business can bring in mutual benefits for both parties.
Every serrated flange bolt undergoes comprehensive multi-stage quality inspection to ensure full compliance with international construction standards and customer specifications.
EN 15048 CE Certification ยท EN14399 CE Certification ยท ISO9001 Certificate ยท AD2000 Certification
Grasp first-hand information โ what our global construction clients say about Zhongli serrated flange bolts.
Explore our complete range of high-strength construction fasteners โ all manufactured to international standards.
Ningbo Zhongli Bolts Manufacturing Co., Ltd. founded in 2003, is a professional manufacturer of high-strength fasteners in different specifications for various models, which covers an area of about 10,000 square meters, registered capital of 1,500,000 RMB, with the total annual productivity of 8,000 tons per year. The company has set up several sales branches in different provinces in China.
Our serrated flange bolts for construction are exported to Europe, USA, Middle East, Africa, Southeast Asia and other regions, trusted by engineers and contractors worldwide for their superior vibration resistance and consistent quality.
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