Release time：2020-01-16 18:44 Browse：
Here’s an expanded, technical point-by-point description with detailed specifications, manufacturing insights, and application scenarios:
### 1. **Product Standards & Design Compliance**
- **DIN 931 Conformance**:
- Specifies hexagon head bolts with full/half threads, matching DIN 933 (threaded length) and DIN 934 (nuts).
- Head dimensions: Width across flats (e.g., M10 = 16mm, M16 = 24mm) with 15–30° chamfer for wrench clearance.
- Tolerances: Head height ±0.2mm, thread pitch ±0.05mm (ISO 6g external thread).
### 2. **Material Science & Mechanical Properties**
- **Grade 4.8 Steel Composition**:
- Carbon (C): 0.15–0.35%, Manganese (Mn): 0.4–0.8%, Silicon (Si): ≤0.35% (low-carbon steel, e.g., EN 10025-2: S235JR).
- **Mechanical Data**:
- Tensile strength (σb): 400–520 MPa (verified via universal testing machine).
- Yield strength (σs): 320 MPa (0.2% proof stress).
- Elongation at break: ≥25% (ductile enough for non-critical applications).
- **Microstructure**: Ferrite-pearlite matrix (unhardened, no quenching/tempering).
### 3. **Dimension Specifications & Threading**
- **Length Range**:
- Extended lengths: 50–300mm (custom up to 500mm for special orders).
- Thread Length (per DIN 933):
- For M10×50mm: Thread length ~25mm; grip length ~25mm.
- For M16×100mm: Thread length ~40mm; grip length ~60mm.
- **Thread Details**:
- Metric coarse thread (ISO 68-1):
- M6×1.0, M8×1.25, M10×1.5, M12×1.75, M14×2.0, M16×2.0.
- Thread accuracy: 6g tolerance (external), compatible with 6H nuts (DIN 934).
### 4. **Surface Treatments & Corrosion Protection**
- **Galvanized Finish (Zn)**:
- Process: Electroplating or hot-dip galvanizing (HDG).
- Coating thickness:
- Electro-galvanized: 8–12μm (500+ hours salt spray, ASTM B117).
- HDG: 25–45μm (1,000+ hours, ideal for outdoor use).
- Appearance: Bright zinc (silver-gray) or passivated (blue/yellow iridescence).
- **Plain Finish (Uncoated)**:
- Surface: Mill finish (Ra 12.5μm), suitable for:
- Indoor dry environments (e.g., machinery covers).
- Post-painting applications (primer recommended within 24 hours).
### 5. **Design Engineering & Functional Features**
- **Half-Threaded Shank**:
- **Purpose**: Reduces stress concentration in shear-loaded joints (e.g., beam-to-column connections).
- **Grip Length**: Unthreaded portion allows direct metal-to-metal contact, enhancing load distribution.
- **Hexagon Head Reinforcement**:
- Head height: 0.7×d (e.g., M12 head height = 7.9mm) to prevent deformation under torque.
- Under-head radius: R0.5mm to minimize fatigue cracking.
- **Assembly Ease**:
- Chamfered thread end facilitates nut starting; no need for tap drilling in soft materials.
### 6. **Industrial Applications & Use Cases**
- **General Manufacturing**:
- Machinery frames, conveyor rollers, and agricultural equipment (e.g., tractor attachments).
- **Construction & Infrastructure**:
- Temporary formwork, scaffolding braces, and low-load partition walls (non-structural).
- **Automotive & Transportation**:
- Non-critical components: Interior brackets, cargo tie-downs, and trailer hitches.
- **DIY & Maintenance**:
- Furniture assembly, garden equipment repair, and household fixtures (e.g., gate hinges).
### 7. **Installation Parameters & Torque Values**
- **Recommended Torque (DIN 267-2)**:
| Size | Dry Thread (Nm) | Lubricated Thread (Nm) |
|-------|-----------------|-----------------------|
| M6 | 4–5 | 3–4 |
| M8 | 9–11 | 7–8 |
| M10 | 20–25 | 15–18 |
| M12 | 35–40 | 28–32 |
- **Installation Tips**:
- Use calibrated torque wrench; avoid overtightening (risk of bolt shear in grade 4.8).
- In wet environments, apply anti-seize compound to galvanized threads to prevent galling.
### 8. **Quality Control & Testing Regime**
- **100% Inspections**:
- Thread Go/No-Go gauging (e.g., M12 thread must pass 12.06mm Go gauge, fail 11.95mm No-Go).
- Head width/length measured via caliper (tolerance ±0.15mm for M10+).
- **Sample Testing (per batch)**:
- Tensile test: Random 5pcs/batch pulled to ≥400 MPa.
- Zinc coating thickness: X-ray fluorescence (XRF) measurement.
- **Certifications**:
- CE marking (for EU market); material test report (MTR) available on request.
### 9. **Packaging, Logistics & Customization**
- **Bulk Packaging**:
- 500pcs/carton (M6–M10); 200pcs/carton (M12–M16) with moisture-absorbing desiccant.
- Palletized loads: 10–20 cartons/wooden pallet (edge-protected for transit).
- **Lead Times**:
- Standard sizes (M6–M16×50–100mm): 24–48h shipping.
- Custom lengths (≥150mm) or special finishes: 5–7 working days.
- **OEM Options**:
- Laser-engraved part numbers/batch codes; custom packaging with client logos.
### 10. **Technical Advantages & Limitations**
- **Cost-Effective Solution**:
- 30–50% cheaper than grade 8.8 bolts, suitable for non-critical loads.
- Galvanized option balances corrosion resistance and budget (vs. stainless steel).
- **Performance Limits**:
- Not suitable for:
- Seismic zones (use grade 8.8+);
- High-temperature applications (>250°C);
- Cyclic loading (risk of fatigue failure).
### 11. **Environmental & Regulatory Compliance**
- **RoHS/REACH Compliance**:
- Zinc plating free of hexavalent chromium (CrVI); compliant with EU 2011/65/EU.
- **Recyclability**:
- Steel core 100% recyclable; galvanized coating recoverable via smelting.
### 12. **Application-Specific Engineering Notes**
- **In Concrete Applications**:
- Pre-drill hole diameter = bolt diameter + 1mm (e.g., M10 → 11mm hole) for optimal grip.
- **In Aluminum Assemblies**:
- Use nylon washers to prevent galvanic corrosion between steel bolts and aluminum parts.
