PROPERTY CLASS 10.9 FASTENERS — TECHNICAL DATASHEET AND ENGINEERING REPORT
Property Class 10.9 represents a critical high-tensile tier in metric mechanical engineering and structural steel design. Governed primarily by the international standard ISO 898-1, these fasteners are engineered to deliver robust clamping forces under severe static and dynamic loading regimes. The designation "10.9" indicates a nominal ultimate tensile strength ($R_m$) of 1000 MPa and a yield ratio of 0.9, translating to a nominal yield strength ($R_{p0.2}$) of 900 MPa.
The narrow margin between yield strength (940 MPa minimum) and tensile strength (1040 MPa minimum) necessitates precise preload control during installation, as Class 10.9 fasteners exhibit high elastic capacity but a limited plastic deformation range before failure.
■ Chemical Composition and Material Routes
To satisfy core hardenability requirements, ISO 898-1 defines three distinct permissible material classifications. All fasteners must undergo mandatory quenching and tempering (Q&T).
| Material Route | Carbon (C, %) | Phosphorus (P, max %) | Sulfur (S, max %) | Min. Tempering Temp. |
|---|---|---|---|---|
| Carbon Steel w/ Additives | 0.15 – 0.55 | 0.025 | 0.025 | 425°C |
| Plain Carbon Steel | 0.25 – 0.55 | 0.025 | 0.025 | 425°C |
| Alloy Steel | 0.20 – 0.55 | 0.025 | 0.025 | 425°C |
■ Proprietary Datasheet Download
ISO 898-1 Class 10.9 — Complete Technical Yield & Tolerance Datasheet
Contains empirical data for stress simulations, international regulatory compliance audits, and advanced clamp load charts. Corporate/engineering credentials required.
⬇ DOWNLOAD DATASHEET■ Mechanical Performance Requirements
Minimum mechanical properties are elevated for larger diameters ($d > 16\text{ mm}$) to compensate for core cooling limits in larger cross-sections.
| Mechanical Property | d ≤ 16 mm | d > 16 mm |
|---|---|---|
| Min. Tensile Strength (Rm) | 1040 MPa | 1040 MPa |
| Min. Yield Strength (Rp0.2) | 940 MPa | 940 MPa |
| Stress Under Proof Load (Spf) | 830 MPa | 830 MPa |
| Min. Elongation (A5) | 9% | 9% |
| Min. Charpy Impact (KV) | 27 J | 27 J |
| Hardness (Vickers) | 320 – 380 HV | 320 – 380 HV |
■ Physical Properties
| Property | Value |
|---|---|
| Density | 7800 kg/m³ |
| Young's Modulus (E) | 210 GPa |
| Poisson's Ratio | 0.3 |
| Shear Modulus (G) | 80 GPa |
| Thermal Expansion (CTE) | 12 × 10⁻⁶/K |
■ Tightening Torque Guidelines (Coarse Threads)
Design clamp load is calculated at 75% of minimum proof load. Torque values vary significantly based on friction coefficients ($K$).
| Size | Preload (kN) | Lubricated Torque (Nm) | Dry Torque (Nm) |
|---|---|---|---|
| M10 | 25.2 | 37.8 | 50.5 |
| M12 | 36.7 | 66.0 | 88.0 |
| M16 | 68.3 | 164.0 | 219.0 |
| M20 | 110.3 | 331.0 | 441.0 |
| M24 | 158.9 | 572.0 | 762.0 |
■ Engineering Considerations
- Hydrogen Embrittlement: Due to high tensile strength (>1000 MPa), Class 10.9 fasteners are highly susceptible. Plated parts must undergo mandatory relief baking (200°C for ≥4 hours) within 4 hours of plating.
- Welding Prohibitions: Welding is strictly prohibited. Heat from welding destroys the tempered martensitic structure, reducing mechanical properties below Class 10.9 specifications.
- Thermal Limits: Continuous service temperature should not exceed 250°C. Service above 300°C causes strength degradation via tempering, and service above 500°C causes full annealing.
- Galvanic Risk: For marine or corrosive outdoor environments, specify HDG (Hot-Dip Galvanizing) or Zinc Flake coatings to prevent oxidation, ensuring compliance with ISO 10684.