Flange bolts are specialized fasteners featuring a broad, flat washer-like base integrated directly beneath the bolt head. This design distributes clamping force more evenly, reducing the risk of surface damage and enhancing stability, making them ideal for applications requiring high torque and vibration resistance, such as automotive engines, industrial machinery, and pipeline connections.
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Standard
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Country/Region
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Description
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ISO 4162
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International
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Defines dimensions, tolerances, and mechanical properties of hexagon flange bolts
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DIN 6921 / DIN 6922
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Germany
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Specifies high-strength and standard-strength hexagon flange bolts respectively
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ASME B18.2.1
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USA
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Covers unified inch series flange bolts with various head styles
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GB/T 5787 / GB/T 5788
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China
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Details product specifications for metric hexagon flange bolts
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JIS B 1186
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Japan
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Japanese standard for hexagon flange bolts with different thread lengths
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Grade
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Material
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Tensile Strength (MPa)
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Application Scenarios
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4.8
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Low-carbon steel (e.g., Q235)
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400/320
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General-purpose assembly, light-duty machinery
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8.8
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Medium-carbon steel (e.g., 45# steel)
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800/640
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Automotive components, industrial equipment
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10.9
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Alloy steel (e.g., 35CrMo, 42CrMo)
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1000/900
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High-stress applications like heavy trucks and engines
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12.9
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Alloy steel (e.g., 20MnTiB)
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1200/1080
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Extreme-load scenarios, aerospace, high-performance machinery
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A2-70 (Stainless Steel)
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304 stainless steel
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700
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Corrosion-prone environments (marine, food processing)
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A4-80 (Stainless Steel)
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316 stainless steel
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800
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High-corrosion and high-temperature settings, such as chemical plants
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Aluminum Alloy
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6061 or 7075 aluminum
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276 - 572
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Lightweight applications in aerospace or automotive interiors
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Treatment Method
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Abbreviation
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Description
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Zinc Plating
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Zn
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Basic anti-rust protection; available in blue, yellow, or white finishes
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Hot-Dip Galvanizing
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HDG
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Robust corrosion resistance, suitable for outdoor and heavy-industrial use
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Zinc-Nickel Plating
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Zn-Ni
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Superior corrosion resistance compared to zinc, often used in automotive applications
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Dacromet Coating
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Dacromet
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Environmentally friendly, chromium-free coating with excellent anti-corrosion and anti-galling properties
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Black Oxide Coating
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Black
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Creates a black, non-reflective surface with mild rust resistance, ideal for internal machinery
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PTFE Coating
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PTFE
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Provides lubricity, reducing friction and wear, commonly used in high-torque applications
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