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0102030405
China Suppliers Factory Yellow Zinc Plated Hex Flange Bolt DIN6921 - Carbon Steel, Stainless Steel, ISO Certified
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. Here is a detailed introduction:
🔩 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.
✅ Main Advantages
No Need for Additional Gaskets
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.
🏭 Common Application Areas
🚗
Automotive Industry
Key parts such as the engine, gearbox, and wheel hub — adapted to high vibration environments.
⚙️
Machinery Manufacturing
Heavy equipment, machine tools, pumps, valves, and other connections requiring high preload force.
🏗️
Architecture & Steel Structures
Wind and earthquake-resistant structures such as bridges, steel frames, and curtain walls.
🚆
Rail Transit
Scenarios with high requirements for safety and reliability, such as rail vehicles and signal equipment.
🛡️ Material & Surface Treatment
🔧 Common Materials
Carbon Steel (4.8 / 8.8 / 10.9)
Stainless Steel A2-304
Stainless Steel A4-316
Alloy Steel (High-Strength)
Alloy Steel (High-Temp)
🎨 Surface Treatment
Galvanized
Dacromet
Hot Dip Galvanizing
Phosphating
❓ Frequently Asked Questions
Q What is the main difference between a flange bolt and a regular bolt?
A flange bolt features an integrated flange (washer-like disc) beneath the head. This eliminates the need for a separate washer, distributes the clamping load over a larger area, and provides built-in anti-loosening properties — advantages that standard bolts do not offer on their own.
Q Why are flange bolts preferred in vibration-heavy environments?
The serrated or toothed pattern on the flange surface grips the mating surface tightly, significantly increasing friction. This prevents the bolt from rotating or backing out under repeated vibration — making them ideal for automotive engines, gearboxes, and rail transit applications.
Q What materials are flange bolts commonly made from?
Flange bolts are available in carbon steel (grades 4.8, 8.8, 10.9), stainless steel (A2-304 for general corrosion resistance, A4-316 for harsh environments), and alloy steel for high-strength or high-temperature applications. The choice depends on load requirements and environmental conditions.
Q Which surface treatment is best for outdoor flange bolts?
Hot-dip galvanizing provides the thickest zinc coating and is best suited for heavy-duty outdoor use such as bridges and steel structures. Dacromet is also an excellent choice for high corrosion resistance in demanding outdoor environments. Standard electroplated zinc (galvanized) is suitable for general indoor or mildly corrosive conditions.
Q Can flange bolts be reused after removal?
Flange bolts can generally be reused if they show no visible damage, thread wear, or deformation of the flange. However, high-strength bolts (grade 10.9 and above) that have been torqued to their yield point should be replaced, as re-tightening may compromise their clamping integrity and safety.
Q Are flange bolts compatible with standard tools?
Yes. Most flange bolts use a standard hexagonal head, meaning they can be installed and removed using common wrenches, sockets, and torque wrenches. Some high-strength variants feature a twelve-point (double hex) head for higher torque application, which requires a matching twelve-point socket.