Release time：2020-01-16 18:44 Browse：
Here’s a detailed point-by-point description with expanded technical and application details: ### 1. **Material & Mechanical Properties** - **Grade 8.8 Carbon Steel**: - Composed of medium-carbon steel (0.25–0.5% carbon) heat-treated to achieve: - **Tensile Strength**: Min. 800 MPa (116,000 psi), suitable for heavy static and dynamic loads. - **Yield Strength**: Min. 640 MPa (93,000 psi), ensuring resistance to permanent deformation under stress. - Magnetic and weldable, with good ductility for formability. - **Galvanization (Zinc Plating)**: - **Hot-Dip or Electroplating**: Thickness ranges from 8–25μm (standard: 12–18μm for outdoor use), providing **500–1,000 hours of salt spray resistance** (ASTM B117). - Zinc coating acts as a sacrificial barrier, corroding before the steel substrate to protect against rust. ### 2. **Design Specifications** - **Outer Hexagon Head**: - Conforms to ISO 4014/DIN 931 standards, with width across flats (e.g., M12 = 19mm) and height (e.g., M12 = 7.9mm) for universal tool compatibility. - Chamfered edges for easy alignment during installation; radius under the head reduces stress concentration. - **Thread Types**: - **Full-Thread (ISO 4762)**: Threads run the entire shank length, ideal for applications requiring maximum clamping force (e.g., thin plates, flanges). - **Half-Thread (ISO 8765)**: Unthreaded grip length (shank) enhances shear strength in shear-loaded joints (e.g., structural connections, machinery mounts). - **Thread Pitch**: Metric coarse (e.g., M10×1.5, M20×2.5) or fine (e.g., M12×1.25) options available for specific torque requirements. - **Lengthened/Extended Lengths**: - Custom lengths from 20mm (M4) up to 300mm (M27) for deep installations in multi-layered structures, pipes, or heavy equipment. ### 3. **Size Range & Compatibility** - **Nominal Sizes**: - M4, M5, M6, M8, M10, M12, M16, M20, M24, M27 (standard metric diameters). - Lengths: 10–300mm (standard), with non-standard lengths available for OEM orders. - **Thread Tolerance**: - 6g for external threads (ISO 965-1), ensuring precise fit with 6H nuts and pre-threaded holes. ### 4. **Surface Finish & Corrosion Resistance** - **Galvanization Types**: - **Blue/White Zinc**: Standard for general corrosion protection (e.g., indoor machinery), salt spray resistance ~48–72 hours. - **Yellow/Black Zinc**: Thicker coatings (15–25μm) for harsh environments (e.g., outdoor construction, automotive), salt spray resistance ~100–500 hours. - **Passivated**: Post-galvanization treatment (chromate or trivalent chromium) to enhance adhesion and corrosion resistance. - **Optional Coatings**: - **Dacromet (Zinc Chromate)**: For extreme environments, offering 1,000+ hours of salt spray resistance (ideal for marine or industrial use). - **PTFE (Teflon) Coating**: Reduces friction for easier assembly and disassembly in high-temperature applications. ### 5. **Applications & Industries** - **Industrial Machinery**: - Fastening gears, motors, pumps, and conveyor systems in manufacturing plants. - Heavy equipment assembly (e.g., excavators, cranes) requiring high-strength, vibration-resistant connections. - **Construction & Infrastructure**: - Structural steel connections (beams, columns), bridges, and prefabricated buildings. - Foundation anchors and scaffolding in outdoor construction projects. - **Automotive & Transportation**: - Chassis components, engine mounts, and suspension systems in trucks and heavy vehicles. - Trailer and railcar assembly, where exposure to road salts and moisture demands corrosion resistance. - **Energy & Utilities**: - Wind turbine towers, solar panel支架 (mounts), and electrical substation equipment. ### 6. **Installation & Maintenance** - **Torque Guidelines**: - Follow ISO 898-1 torque tables (e.g., M12 8.8 grade bolt: ~70–80 Nm for dry threads, ~55 Nm with lubricant). - Use torque wrenches to avoid overtightening and bolt failure. - **Anti-Loosening Methods**: - Lock washers, thread-locking compounds (e.g., Loctite), or nyloc nuts for vibration-prone applications. - **Environmental Limits**: - Operating temperature: -40°C to +250°C (galvanized); higher with heat-resistant coatings. ### 7. **Quality Assurance & Compliance** - **Testing**: - **Tensile Testing**: Verified via universal testing machines to meet 8.8 grade requirements. - **Thread Gaging**: Go/No-Go gauges ensure compliance with ISO metric standards. - **Coating Thickness**: Measured via magnetic induction or X-ray fluorescence (XRF). - **Certifications**: - CE, ISO 9001, and RoHS compliant for European markets. - ASTM A325/A490 equivalent for structural applications in North America. ### 8. **Advantages Over Alternatives** - **Cost-Effective Strength**: Balances high tensile strength with lower cost compared to stainless steel or alloy steel bolts. - **Versatility**: Full/half-thread options and extended lengths reduce need for custom machining. - **Corrosion Protection**: Galvanization offers better value than stainless steel in non-critical corrosion environments. ### 9. **Limitations & Considerations** - **Not for High-Corrosion Environments**: Avoid marine, coastal, or chemical-processing applications (use 316 stainless steel or Dacromet-coated bolts instead). - **Risk of Hydrogen Embrittlement**: Heat-treated steel may require bake-out after plating to prevent brittle failure in high-stress applications. ### 10. **Packaging & Logistics** - **Standard Packaging**: - Bulk: 500–1,000 pieces per carton with moisture-proof paper. - Retail: 50–100 pieces per poly bag with size and grade labeling. - **Lead Times**: - Stock sizes: 1–3 days; custom lengths or coatings: 2–4 weeks. This comprehensive overview covers material science, design precision, application versatility, and industry compliance, making these bolts suitable for demanding industrial and structural applications.
