Product Summary

Longze High-Strength Flange Bolts are high-performance fasteners designed with an integrated circular flange under the hex head, eliminating the need for a separate washer and ensuring superior

load distribution. Manufactured in Yongnian, China, our flange screws are quenched and tempered to meet the highest mechanical classes (Grade 8.8, 10.9, and 12.9), making them the ideal choice

for automotive, heavy machinery, and structural steel applications.

• ✔ Self-Washer Design: The integrated flange increases the bearing surface, preventing embedment and spreading the clamping force evenly across the joint.

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• ✔ Vibration Resistance: Available with serrated or smooth flange bases to increase friction and prevent loosening under high-vibration conditions.

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• ✔ High Torque Capacity: Precision-forged hex heads allow for high-torque tightening without stripping or rounding the corners.

• Standards: DIN 6921, ISO 4162, ASME B18.2.1, EN 1665.

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• Diameter Range: M5 to M24 | 1/4" - 1".

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• Length Range: 10mm to 200mm.

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• Material Grade: Carbon Steel (Class 8.8, 10.9, 12.9) | Stainless Steel 304 & 316.

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• Surface Finish: Black Oxide, Zinc Plated, Dacromet, Geomet, Zinc-Nickel.

Mechanical Properties & Material Standards

• Matching the steel grade to the structural requirements of the transmission line.

• Property Class	Material	Tensile Strength (min)	Yield Strength (min)	Hardness Range
  Class 8.8	Medium Carbon	800 MPa	640 MPa	22 - 32 HRC
  Class 10.9	Alloy Steel	1040 MPa	940 MPa	32 - 39 HRC
  Class 12.9	Alloy Steel	1220 MPa	1100 MPa	39 - 44 HRC
  Stainless 304	A2-70	700 MPa	450 MPa	200 - 280 HV

Standard Cross Arm Dimensions

• Common angle steel configurations for standard utility pole mounting.

• Thread Size (D)	Flange Dia (dc)	Head Height (k)	Width Across Flats (s)	Pitch (Metric)
  M8	18 mm	8.1 mm	13 mm	1.25 mm
  M10	22.3 mm	9.2 mm	15 mm	1.5 mm
  M12	26.6 mm	11.5 mm	18 mm	1.75 mm
  M16	35 mm	14.4 mm	24 mm	2.0 mm

Galvanizing & Corrosion Resistance

• Ensuring 30+ years of service life in corrosive environments.

• Surface Treatment	Coating Thickness	Salt Spray Test	Best Application	Friction Coeff.
  Black Oxide	N/A	24 - 48 Hours	Oiled Engine Parts	0.12 - 0.18
  Zinc Plated	5 - 12 μm	72 - 144 Hours	Indoor Machinery	0.15 - 0.22
  Dacromet	8 - 12 μm	500 - 1000 Hours	Automotive / Chassis	0.10 - 0.16
  Zinc-Nickel	8 - 10 μm	1000 - 2000 Hours	EV / Marine	0.12 - 0.18

Avoid Pitfalls:

• Head-to-Flange Concentricity: We prevent tool slippage and uneven clamping by ensuring the hex head is perfectly centered on the flange using high-speed multi-station cold heading machines.

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• Hydrogen Embrittlement: For Class 10.9 and 12.9 bolts, we perform a strict de-embrittlement baking process (4 hours at 200°C) immediately after plating to prevent sudden brittle failure under stress.

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• Serration Fatigue: While serrated flanges increase grip, they can damage the mating surface. Longze offers both smooth and serrated options depending on whether your project requires high friction or surface protection.

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Perfect Fit Assembly:

• Washerless Efficiency: Our flange bolts eliminate the labor costs and inventory management associated with separate washers, reducing total assembly time by up to 25%.

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• Matched Flange Nuts: We provide DIN 6923 Flange Nuts specifically color-matched and grade-matched to your bolts for a complete "Zero-Washer" fastening system.

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Quality Control & Logistics:

• ISO 9001 Certified: 5-step QC including computerized sorting for dimension consistency, torque-tension testing, and microstructure analysis.

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• Sea-Worthy Packaging: Bolts are packed in heavy-duty 25kg cartons, plastic-lined for moisture protection, and shipped on reinforced Fumigation-Free Pallets.

• Q: Do you offer fine-pitch flange bolts for automotive applications? A: Yes, we can manufacture M10x1.25 and M12x1.25 fine-pitch flange bolts in Grade 10.9 to meet specific engine and chassis requirements.

• Q: Can you provide customized flange diameters? A: Absolutely. For applications requiring extra-wide bearing surfaces, we can customize the flange diameter (Large Flange) based on your engineering drawings.