Blackened outer hexagon bolts, high-strength thick bar screws, hexagon head scre

Release time：2020-01-16 18:44 Browse：

1. Product Range & Specifications

• Blackened Outer Hexagon Bolts

• Full-threaded (ISO 4762) for thin materials or through-hole assemblies.

• Half-threaded (ISO 8765) with unthreaded shank for shear-loaded joints.

• Oxide Coating: Chemical conversion (black oxide) or electroplating (zinc-nickel alloy) for 500–1000 hours of salt spray resistance (ASTM B117).

• Appearance: Uniform matte black finish (Ra 3.2–6.3μm surface roughness) for aesthetic and anti-glare applications.

• Head Style: External hexagon (ISO 4014/DIN 931) with chamfered edges for tool clearance.

• Blackening Process:

• Thread Types:

• Size Range: M6–M36 (metric) or 1/4"–1-1/2" (inch), with lengths from 20mm to 300mm.

• High-Strength Thick Bar Screws

• 8.8 Grade: Tensile strength ≥800 MPa, yield strength ≥640 MPa (medium-carbon steel).

• 10.9 Grade: Tensile strength ≥1000 MPa, yield strength ≥900 MPa (alloy steel with boron/vanadium).

• Shank Diameter: ≥M12 (thick bars) for load-bearing applications requiring shear strength.

• Grade Options:

• Thread Engagement: Fine-pitch threads (e.g., M20×1.5) for precise torque control in critical joints.

• Hexagon Head Screws

• Full-point (sharp tip) for self-tapping into pre-drilled holes.

• Flat-point (blunt end) for non-threaded applications (e.g., set screws).

• Head Dimensions: Width across flats (e.g., M12 = 19mm) conforming to DIN 933/ISO 4017.

• Point Types:

2. Material & Manufacturing

• Steel Composition:

• 8.8 Grade: 0.25–0.55% carbon steel (e.g., 45#/1045), quenched and tempered.

• 10.9 Grade: Low-alloy steel (e.g., 35CrMo/42CrMo), heat-treated for enhanced ductility.

• Production Processes:

• Cold Forging: For bolts ≤M24, ensuring grain flow alignment and improved fatigue resistance.

• Hot Forging: For larger diameters (M27–M36), with controlled cooling to prevent cracking.

• Thread Rolling: Produces stronger threads than cutting, with 20–30% higher fatigue life.

• Quality Control:

• Thread Gauging: 100% inspection with Go/No-Go plugs to verify ISO 68-1 thread profile.

• Hardness Testing: Rockwell C scale (e.g., 8.8 grade: 22–32 HRC; 10.9 grade: 32–39 HRC).

• Magnetic Particle Inspection: Detects surface cracks in critical applications.

3. Surface Treatments & Coatings

• Black Oxide:

• Thickness: 0.5–1.5μm, providing mild corrosion resistance and lubricity.

• Common in automotive engines and machinery (e.g., cylinder heads).

• Zinc-Nickel Plating:

• 8–12μm thickness with 15–20% nickel content, offering 1000+ hours of salt spray resistance.

• Used in marine environments or industrial equipment exposed to chemicals.

• Dacromet/Geomet:

• Silicate-based coating (5–10μm) for extreme corrosion resistance (e.g., bridge components).

• PTFE (Teflon) Coating:

• Reduces friction coefficient (μ = 0.05–0.1) for applications requiring easy assembly/disassembly (e.g., adjustable machinery).

4. Applications & Use Cases

• Industrial Machinery

• Heavy Equipment: Earthmovers, cranes, and mining drills (thick bar screws for high-stress joints).

• Conveyor Systems: Blackened bolts prevent rust in food processing or outdoor installations.

• Automotive & Transportation

• Engine Components: Connecting rods, cylinder heads, and transmission mounts (10.9 grade for vibration resistance).

• Trailers & Trucks: Frame assemblies and suspension systems (half-threaded for shear loads).

• Construction & Infrastructure

• Structural Steel: Bridges, high-rise buildings, and prefabricated structures (compliant with EN 14399 for structural bolts).

• Solar/Wind Energy: Panel mounts and turbine towers (corrosion-resistant coatings for outdoor exposure).

• Electrical & Electronics

• Switchgear & Transformers: Blackened hex screws prevent sparking in high-voltage environments.

• Server Racks: Anti-glare finish for aesthetic appeal in data centers.

5. Technical Advantages

• Corrosion Resistance:

• Black oxide outperforms plain steel in humid environments; zinc-nickel is suitable for coastal areas.

• Torque Accuracy:

• Hex heads distribute torque evenly, reducing risk of stripping compared to Phillips or slotted heads.

• Vibration Resistance:

• High-strength grades and thread-locking patches (e.g., nylon inserts) prevent loosening in dynamic applications.

• Cost-Effectiveness:

• Lower cost than stainless steel alternatives while maintaining comparable strength in non-corrosive settings.

6. Installation & Maintenance

• Torque Specifications:

• Follow ISO 898-1 guidelines (e.g., M16 8.8 grade: 120–150 Nm for dry threads; 80–100 Nm with lubricant).

• Anti-Seize Compounds:

• Apply copper-based paste to prevent galling in stainless steel or aluminum assemblies.

• Inspection Protocol:

• Check for thread damage or corrosion annually in critical applications (e.g., infrastructure projects).

7. Compliance & Certifications

• International Standards:

• ISO 4014 (hexagon bolts), ISO 898-1 (mechanical properties), and ISO 10683 (fastener marking).

• Regional Certifications:

• Europe: CE marking for structural bolts (EN 14399); RoHS/REACH compliant.

• North America: ASTM A325/A490 equivalency for high-strength structural use.

• Industry-Specific:

• Automotive: TS 16949 quality management for OEM components.

• Marine: NACE MR0175 certification for sour gas environments.

8. Customization Options

• Non-Standard Sizes:

• Custom diameters (e.g., M22.5) or lengths (e.g., 450mm) for specialized machinery.

• Thread Modifications:

• Left-hand threads, UNC/UNF inch threads, or metric fine threads (e.g., M12×1.25).

• Special Markings:

• Laser-etched part numbers, batch codes, or customer logos for traceability.

9. Packaging & Logistics

• Standard Packaging:

• Bulk: 500–1000 pieces per carton with moisture-absorbing silica gel.

• Retail: Blister packs or plastic jars for small-quantity sales.

• Shipping Options:

• Air freight (7–10 days) for urgent orders; sea freight (20–30 days) for cost-effective bulk shipments.

10. Environmental Considerations

• Recyclability:

• Steel cores are 100% recyclable; zinc coatings are recoverable via smelting.

• Eco-Friendly Coatings:

• Water-based blackening solutions (vs. traditional hexavalent chromium processes).