Home » DIN 6921 Class 8.8 Hex Flange Bolt Zinc Finish

DIN 6921 Class 8.8 Hex Flange Bolt Zinc Finish

DIN 6921 Hex Flange Bolt — Class 8.8 | Zinc CR3 Finish | FULLERKREG

FULLERKREG DIN 6921 Class 8.8 Hex Flange Bolts deliver reliable, high-strength fastening for automotive and new energy vehicle (NEV) assemblies. Manufactured at our Wuhu, Anhui facility — situated in China's premier automotive manufacturing hub, home to Chery Automobile — these bolts are produced to the full dimensional and mechanical requirements of DIN 6921 and DIN EN ISO 898-1, with a RoHS-compliant Zinc CR3 (trivalent chromate) surface finish per DIN 267-11.

Product Overview

  • Standard: DIN 6921
  • Type: Hexagon Flange Bolt (with or without serration)
  • Material: Alloy Steel 10B21 (boron steel) or Carbon Steel 35K
  • Property Class / Grade: 8.8 (per DIN EN ISO 898-1)
  • Surface Treatment: Zinc CR3 (trivalent chromate zinc electroplate)
  • Thread: Metric coarse thread (ISO 68-1)
  • Brand: FULLERKREG
  • Manufacturing Origin: Wuhu, Anhui, China

Two Flange Head Types Available

① Non-Serrated Flange (Smooth Flange)

The standard DIN 6921 configuration featuring a smooth, flat flange underhead bearing surface. The enlarged flange diameter distributes clamping load over a wider area, reducing surface pressure on the joint and eliminating the need for a separate washer in most applications.

  • Smooth flange underside — no surface marking on mating parts
  • Large bearing area reduces contact stress on softer substrates
  • Suitable for painted panels, aluminium castings, and plastic brackets
  • Preferred in body-in-white (BIW), interior trim, and cover assemblies
  • Compatible with thread-locking compounds and prevailing torque nuts for vibration resistance

② Serrated Flange (Toothed Flange)

Features radial serrations machined into the flange underside. Upon tightening, the teeth bite into the mating surface, creating a mechanical lock that resists vibration-induced loosening without any additional locking element.

  • Integral serrated locking feature — no separate lock washer required
  • Superior resistance to vibration and dynamic loosening
  • Ideal for powertrain, chassis, and battery enclosure joints subject to continuous vibration
  • Widely used in EV motor mounts, battery pack frames, and suspension brackets
  • Not recommended for soft or easily damaged mating surfaces

Material Options

Option A — Alloy Steel 10B21 (Boron Steel)

10B21 is a boron-alloyed low-carbon steel widely used in automotive fastener manufacturing. The addition of boron significantly improves hardenability, allowing Class 8.8 mechanical properties to be achieved with lower alloy content and excellent cold-forging characteristics.

  • Superior hardenability vs. plain carbon steel
  • Excellent cold-heading formability — ideal for high-volume production
  • Consistent mechanical properties across large production lots
  • Preferred material for automotive OEM and Tier-1 supply chains

Option B — Carbon Steel 35K

35K is a medium-carbon steel offering good strength and toughness at an economical cost. Suitable for Class 8.8 fasteners in general industrial and automotive applications where boron-alloyed steel is not specifically required.

  • Good balance of strength and ductility
  • Cost-effective for high-volume standard fastener applications
  • Widely available and well-understood in global supply chains
  • Suitable for non-critical structural joints and general assembly

Mechanical Properties — Class 8.8

Property Specification Standard Reference
Material Alloy Steel 10B21 or Carbon Steel 35K DIN EN ISO 898-1
Property Class 8.8 DIN EN ISO 898-1
Nominal Tensile Strength (Rm) ≥ 800 MPa DIN EN ISO 898-1
Proof Load Stress (Sp) 600 MPa DIN EN ISO 898-1
Yield Strength (Rp0.2) ≥ 640 MPa DIN EN ISO 898-1
Hardness (Vickers) 250 – 320 HV DIN EN ISO 898-1
Core Hardness (Rockwell) 22 – 32 HRC DIN EN ISO 898-1
Elongation after fracture ≥ 12% DIN EN ISO 898-1
Surface Treatment Zinc CR3 (trivalent chromate electroplate) DIN 267-11
Corrosion Resistance ≥ 480 hours neutral salt spray (NSS) DIN 267-11 / ISO 9227

Dimensional Reference — DIN 6921 Key Parameters

Thread Size Pitch (mm) Width Across Flats s (mm) Flange Diameter dc (mm) Head Height k (mm)
M5 0.8 8 14.2 3.5
M6 1.0 10 17.0 4.0
M8 1.25 13 22.0 5.5
M10 1.5 15 / 16 27.0 6.5
M12 1.75 18 32.0 8.0
M14 2.0 21 37.0 9.0
M16 2.0 24 43.0 10.0
M20 2.5 30 54.0 12.5

Full dimensional tables per DIN 6921. Custom lengths and thread pitches available upon request.

Surface Treatment: Zinc CR3 (Trivalent Chromate)

The Zinc CR3 finish applied to FULLERKREG DIN 6921 Class 8.8 bolts provides robust corrosion protection while meeting the strictest environmental compliance requirements for automotive supply chains. CR3 denotes trivalent chromium passivation — free of hexavalent chromium (Cr⁶⁺), fully compliant with RoHS, ELV Directive, and REACH regulations.

  • Chromate Type: Trivalent chromate (Cr³⁺) — no hexavalent chromium (Cr⁶⁺)
  • Appearance: Bright silver / clear to light blue iridescent finish
  • Corrosion Protection: ≥ 480 hours neutral salt spray (NSS) to first red rust
  • Coating Standard: DIN 267-11 / DIN EN ISO 4042
  • RoHS Compliant: ✅ Yes — no restricted substances
  • ELV Directive Compliant: ✅ Yes — suitable for automotive OEM supply
  • Hydrogen Embrittlement Relief: Controlled baking process post-plating per DIN EN ISO 4042 to eliminate embrittlement risk in Class 8.8 fasteners
  • Coating Thickness: Typically 5–12 µm (per DIN EN ISO 4042 tolerance class)

Primary Application Sectors

🔋 New Energy Vehicles (NEV / EV)

FULLERKREG DIN 6921 Class 8.8 Zinc CR3 bolts are engineered for the demanding fastening requirements of electric vehicle platforms:

  • Battery pack enclosure panels and module frames
  • Electric motor and reducer housing assembly
  • High-voltage cable tray and busbar bracket fastening
  • Thermal management system (TMS) — coolant plate and heat exchanger mounting
  • Onboard charger (OBC) and power distribution unit (PDU) enclosures
  • Chassis cross-members and subframe structural joints
  • Seat rail and occupant safety system anchoring

🚗 Conventional Automotive & Commercial Vehicles

  • Engine peripheral components — timing covers, oil pans, valve covers
  • Transmission and gearbox housing assembly
  • Suspension components — control arms, stabilizer bar brackets, knuckles
  • Brake system — caliper mounting, disc shield, ABS sensor brackets
  • Exhaust system heat shields and catalytic converter brackets
  • Body-in-white (BIW) structural joints and door hinge assemblies
  • Interior trim and dashboard bracket fastening
  • HVAC system and air conditioning compressor mounting

Why Choose FULLERKREG DIN 6921 Class 8.8?

  • ✅ Automotive-Grade Manufacturing: Produced in Wuhu, Anhui — China's premier automotive manufacturing hub, co-located with Chery Automobile's global headquarters. Our facility operates within a mature automotive supply chain ecosystem with decades of fastener manufacturing expertise.
  • ✅ Dual Material Options: Choose between Alloy Steel 10B21 (boron steel, preferred for OEM supply) or Carbon Steel 35K (cost-effective for general applications) — both meeting Class 8.8 mechanical requirements.
  • ✅ RoHS & ELV Compliant Finish: Zinc CR3 trivalent chromate coating meets EU automotive environmental directives — no hexavalent chromium, suitable for global OEM supply chains.
  • ✅ Full DIN Compliance: Every batch manufactured and inspected to DIN 6921, DIN EN ISO 898-1, and DIN 267-11 standards.
  • ✅ Full Traceability: Material certificates (MTC), mechanical test reports, salt spray test records, and coating inspection data available per shipment.
  • ✅ Both Flange Types Stocked: Non-serrated and serrated flange variants available across the full size range.
  • ✅ High-Volume Capability: Consistent lot-to-lot quality suitable for OEM and Tier-1 supplier procurement programs.
  • ✅ Flexible Packaging: Bulk, box, and custom packaging options available to suit assembly line requirements.

Applicable Standards & References

  • DIN 6921 — Hexagon bolts with flange (metric coarse thread)
  • DIN EN ISO 898-1 — Mechanical properties of fasteners: bolts, screws and studs (property class 8.8)
  • DIN 267-11 — Fasteners: technical delivery conditions — electroplated coatings
  • DIN EN ISO 4042 — Fasteners: electroplated coatings (coating thickness, hydrogen embrittlement relief)
  • ISO 9227 — Corrosion tests in artificial atmospheres — neutral salt spray (NSS) test
  • RoHS Directive 2011/65/EU — Restriction of hazardous substances
  • ELV Directive 2000/53/EC — End-of-life vehicles (hexavalent chromium restriction)

Ordering & Customization

FULLERKREG supplies DIN 6921 Class 8.8 Zinc CR3 bolts in standard and custom configurations. Please specify the following when placing an inquiry:

  • Thread diameter and pitch (e.g., M8 × 1.25, M10 × 1.5)
  • Nominal length (e.g., 20 mm, 35 mm, 50 mm)
  • Flange type: Non-Serrated or Serrated
  • Material preference: Alloy Steel 10B21 or Carbon Steel 35K
  • Required quantity and packaging format (bulk / box / reel)
  • Certification requirements (PPAP, IATF 16949, material certificates, salt spray reports)

Contact our technical sales team for datasheets, samples, and volume pricing.

FULLERKREG — Precision Fasteners for the Automotive Future. Manufactured in Wuhu, China.

Sorry, this collection is empty.
Continue shopping