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China Suppliers Factory Yellow Zinc Plated Hex Flange Bolt DIN 6921 - Carbon Steel, Alloy, Stainless, Brass Options
Flange bolt, also known as flange bolt, is a special type of bolt with a flange surface (flange), widely used in situations that require high preload, anti loosening, and sealing.
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Structural Characteristics
Flange Surface Design
There is an integral flange (circular gasket) below the bolt head, which increases the contact area, disperses pressure, and reduces damage to the connection surface.
Hexagonal or Twelve-Pointed Head
Commonly designed as a hexagonal head, easy to tighten with standard tools; some high-strength models use twelve corner heads.
Anti-Slip Tooth Pattern
The flange surface of some flange bolts has radial tooth patterns to enhance friction and prevent loosening.
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Main Advantages
No Additional Gaskets Needed
The integrated flange replaces traditional gaskets, simplifies installation steps, and reduces costs.
Anti-Vibration & Anti-Loosening
The flange surface increases friction, and the tooth pattern design further prevents bolts from loosening in vibration environments.
Uniform Force Distribution
The flange disperses the load, protects the surface of the connected parts, and avoids crushing or deformation.
Sealing Enhancement
When combined with flange surfaces and soft materials such as rubber gaskets, the sealing performance can be improved.
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Common Application Areas
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Automotive Industry
Key parts such as the engine, gearbox, and wheel hub are adapted to high vibration environments.
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Machinery Manufacturing
Heavy equipment, machine tools, pumps, valves, and other connections requiring high preload force.
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Architecture & Steel Structures
Wind and earthquake resistant structures such as bridges, steel frames, curtain walls, etc.
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Rail Transit
Scenarios with high requirements for safety and reliability, such as rail vehicles and signal equipment.
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Material and Surface Treatment
🧱 Common Materials
- Carbon steel (4.8 grade, 8.8 grade, 10.9 grade)
- Stainless steel (A2-304, A4-316, corrosion-resistant)
- Alloy steel (high-strength or high-temperature resistant)
🛡️ Surface Treatment
- Galvanized (conventional anti-corrosion)
- Dacromet (high corrosion resistance)
- Hot dip galvanizing (heavy-duty anti-corrosion, outdoor use)
- Phosphating (enhancing wear resistance)
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Frequently Asked Questions
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What is the main difference between a flange bolt and a regular bolt?
A flange bolt features an integrated flange beneath the bolt head that distributes clamping force over a larger surface area. Regular bolts require a separate washer to achieve the same effect. This makes flange bolts easier to install and more effective at preventing loosening under load.
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Do flange bolts require additional washers during installation?
In most applications, no. The built-in flange acts as an integrated washer, eliminating the need for a separate flat washer. This reduces the number of components required and simplifies the assembly process.
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Are flange bolts suitable for high-vibration environments?
Yes. Flange bolts are specifically well-suited for vibration-prone applications. The larger flange surface increases friction between the bolt head and mating surface, and serrated (tooth pattern) flange variants further resist loosening under dynamic loads — which is why they are widely used in automotive and rail transit applications.
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What materials are flange bolts commonly made from?
Flange bolts are commonly made from carbon steel (grades 4.8, 8.8, 10.9), stainless steel (A2-304 or A4-316 for corrosion resistance), and alloy steel for high-strength or elevated-temperature environments. The right material depends on the operating conditions and mechanical load requirements.
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What surface treatments are available for flange bolts?
Common treatments include zinc plating (galvanizing) for standard corrosion protection, Dacromet coating for higher corrosion resistance, hot-dip galvanizing for heavy-duty or outdoor use, and phosphating to improve wear resistance. Selection should be based on the specific operating environment and durability requirements.
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In which industries are flange bolts most widely used?
Flange bolts are used across a broad range of industries: the automotive sector (engines, gearboxes, wheel hubs), machinery manufacturing (heavy equipment, pumps, valves), civil and structural engineering (bridges, steel frames, curtain wall systems), and rail transit (rolling stock and signal infrastructure) where safety, reliability, and vibration resistance are critical requirements.