Engineering Comparison
Grade 8.8 vs 10.9 Bolts: Tensile Strength Comparison
Compare the mechanical properties, yield strength, and applications of Grade 8.8 and Grade 10.9 high-tensile fasteners.
Key Differences at a Glance
| Property | Grade 8.8 | Grade 10.9 |
|---|---|---|
| Material | Medium Carbon Steel (Quenched & Tempered) | Alloy Steel (Quenched & Tempered) |
| Nominal Tensile Strength | 800 MPa | 1000 MPa (Actual 1040) |
| Nominal Yield Strength | 640 MPa | 900 MPa (Actual 940) |
| Core Hardness | 22-32 HRC | 32-39 HRC |
| Typical Application | General structural steelwork | Heavy machinery, automotive, high-load joints |
Decoding the Property Class
The numbers '8.8' and '10.9' represent a standardized property class. The first number represents 1/100 of the nominal tensile strength in MPa. The second number represents 10 times the ratio of yield strength to tensile strength. Thus, a 10.9 bolt has a tensile strength of 1000 MPa and a yield strength of 900 MPa.
Application Guidelines
While Grade 10.9 offers superior clamping force, it is also harder and more brittle than Grade 8.8. It is crucial to use the correct hardened washers (e.g., DIN 6916) with 10.9 bolts to prevent embedding into the softer parent metal.
Technical FAQ
When should I use Grade 10.9 instead of Grade 8.8?+−
Use Grade 10.9 for applications requiring higher tensile strength (min. 1040 MPa) and higher clamping forces, typical in heavy engineering and automotive. Grade 8.8 (min. 800 MPa) is standard for structural steelwork.