Release time：2020-01-16 18:44 Browse：
Here’s a detailed point-by-point description with technical specifics and application insights: ### 1. **Size Range & Thread Configurations** - **Diameter Range**: M8, M10, M12, M16, M20, M24, M30, M36 (metric sizes), covering lightweight to ultra-heavy-duty applications. - **Thread Types**: - **Full-Threaded**: Threads extend along the entire shank (ISO 4762), maximizing clamping force in through-hole assemblies (e.g., flanges, thin plates). - **Semi-Threaded (Partial-Threaded)**: Unthreaded grip length (shank) enhances shear strength in load-bearing joints (e.g., structural steel, machinery mounts), per ISO 8765. - **Length Options**: - Standard lengths: 20–300mm for M8–M16; 50–500mm for M20–M36. - **Lengthened/Extended Lengths**: Custom lengths up to 1,000mm for deep installations in multi-layered structures, pressure vessels, or industrial equipment. ### 2. **Material & Corrosion Resistance** - **304 Stainless Steel (A2 Grade)**: - Composition: 18% chromium, 8% nickel, <0.08% carbon, offering: - **Corrosion Resistance**: Resistant to rust in mild acidic/alkaline environments, freshwater, and indoor/outdoor settings (not recommended for marine/saltwater without additional coatings). - **Temperature Range**: -196°C to +800°C, suitable for cryogenic and high-heat applications. - **Tensile Strength**: ~520 MPa (annealed), with heat-treated variants reaching 700+ MPa for high-strength needs. - **Black Finish**: - **Passivation**: Chemical treatment to remove free iron and form a thin chromium oxide layer, enhancing corrosion resistance (salt spray test: ~500 hours for passivated 304). - **PVD (Physical Vapor Deposition) Coating**: Black DLC (diamond-like carbon) or TiN (titanium nitride) for aesthetics, reduced friction, and mild wear resistance (ideal for automotive or architectural applications). - **Electrophoretic Coating**: Uniform black finish with improved adhesion, suitable for outdoor machinery. ### 3. **Design & Engineering Features** - **Hexagonal Head Geometry**: - Conforms to ISO 4014/DIN 931 standards (width across flats: e.g., M12 = 19mm, M36 = 55mm) for compatibility with standard wrenches, sockets, and automated assembly tools. - Reinforced head thickness (e.g., M16 head height = 10mm) resists deformation under high torque (up to 500 Nm for M36 bolts). - **Thread Precision**: - ISO metric threads with **6g tolerance** (external) and **6H tolerance** (nuts) ensure tight, vibration-resistant fits. - Roll-formed threads (vs. cut threads) for improved fatigue strength (up to 20% higher tensile stress resistance). - **Lengthened Shank Design**: - Reduces the need for spacers or adapters in thick assemblies, minimizing installation complexity. - Ideal for applications requiring extended reach, such as: - Industrial boilers and heat exchangers. - Large-scale pipeline flanges. - Multi-story building structural connections. ### 4. **Applications & Industries** - **Heavy Industry**: - Machinery: Turbines, presses, and conveyor systems in manufacturing plants. - Oil & Gas: Pumps, valves, and storage tanks in non-corrosive environments. - **Construction & Infrastructure**: - High-rise buildings (steel beam connections), bridges, and stadium structures. - Precast concrete joints and solar panel mounting systems. - **Automotive & Aerospace**: - Heavy-duty vehicle chassis, truck trailers, and aircraft ground support equipment. - High-temperature engine components (e.g., exhaust systems) due to 304’s heat resistance. - **Marine (Limited Use)**: - Suitable for non-submerged applications (e.g., deck hardware) with regular maintenance; upgrade to 316 stainless steel for saltwater immersion. - **Architectural & Decorative**: - Black-finished bolts for visible structural elements in modern buildings, bridges, or sculptures. ### 5. **Performance & Compliance** - **Mechanical Testing**: - Tensile tests confirm compliance with ASTM A193/A320 (for stainless steel fasteners). - Proof load testing ensures bolts withstand specified stress without permanent deformation. - **Corrosion Testing**: - Salt spray tests (ASTM B117) verify passivated 304’s resistance to 500+ hours of exposure (white rust <5% surface coverage). - **Certifications**: - RoHS/REACH compliant for use in EU markets. - CE marking available for structural applications meeting EN 14399 standards. ### 6. **Installation & Maintenance Tips** - **Tooling**: Use torque wrenches to avoid over-tightening (e.g., M16 304 bolt: ~120–150 Nm for full-threaded joints). - **Anti-Seizing**: Apply nickel-based anti-seize compound to prevent galling in stainless steel-to-stainless steel connections. - **Environmental Considerations**: - Avoid contact with chloride-rich materials (e.g., wet wood) to prevent stress corrosion cracking. - In high-vibration applications, use lock washers or thread-locking adhesives (e.g., Loctite 242). ### 7. **Advantages Over Alternatives** - **Corrosion vs. Cost**: 304 offers better corrosion resistance than carbon steel at a lower cost than 316 stainless steel. - **Aesthetic Versatility**: Black finishes provide design flexibility in visible applications (e.g., architectural metalwork). - **High-Temperature Stability**: Outperforms zinc-plated carbon steel in environments above 200°C. ### 8. **Limitations & Upgrades** - **Not for Severe Corrosion**: 304 may corrode in marine,泳池 (pool), or chemical-processing environments; upgrade to **316 stainless steel** (M8–M36 available on request). - **Thread-Locking Options**: For critical joints, specify bolts with pre-applied nylon patches or lock collars. ### 9. **Packaging & Customization** - **Standard Packaging**: - Bulk: 200–500 pieces per carton (M8–M16); 50–100 pieces per carton (M20–M36). - Retail: Poly bags with rust-inhibiting paper for small orders. - **Custom Services**: - Non-standard lengths (e.g., M24×450mm). - Special finishes (e.g., black oxide, PTFE coating). - Laser marking for traceability (part numbers, batch codes). This detailed breakdown highlights the technical excellence, design versatility, and industry applicability of these high-strength stainless steel fasteners.
