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| Specification | Value |
|---|---|
| UNS Number | S31600 / S31603 |
| ASTM/ASME Standard | A193/A193M Grade B8M |
| Tensile Strength | 515 MPa (min) |
| Yield Strength | 205 MPa (min) |
| Density | 8.00 g/cm³ |
| Max Service Temperature | 815°C |
| Element | Composition (%) |
|---|---|
| Cr | 16.0–18.0 |
| Ni | 10.0–14.0 |
| Mo | 2.0–3.0 |
| Mn | ≤2.0 |
| C | ≤0.08 |
| Si | ≤0.75 |
| Fe | bal |
ASTM A193 Grade B8M fasteners are manufactured from AISI 316 austenitic stainless steel, with molybdenum content of 2-3% serving as the defining alloying element. Chromium levels of 16-18.5% provide the foundation for passive oxide layer formation, while nickel content of 10-14% stabilizes the austenitic microstructure and enhances ductility. The added molybdenum significantly improves resistance to localized corrosion, particularly in chloride-rich and marine environments, distinguishing B8M from standard B8 grade fasteners.
This chemical composition delivers exceptional engineering benefits for demanding fastener applications, including superior pitting and crevice corrosion resistance, excellent performance at elevated temperatures up to 815°C, and reliable mechanical strength across a wide operating range. The low carbon content minimizes sensitization risk during welding-adjacent thermal cycles, ensuring long-term structural integrity. These properties make B8M fasteners ideal for chemical processing, marine, offshore, and pharmaceutical industries where corrosion resistance and mechanical reliability are critical requirements.
Specifications
ASTM A193 Grade B8M Fasteners are specified under ASTM A193 for austenitic stainless steel service, with mechanical properties, dimensional tolerances, and technical data governing strength, hardness, and size requirements. Their performance is defined by corrosion-resistant properties and precise fastener dimensions for demanding applications.
| Property | Value |
|---|---|
| Tensile Strength | 515 MPa min |
| Yield Strength (0.2% offset) | 205 MPa min |
| Elongation | 35% min |
| Reduction of Area | 50% min |
| Hardness | 223 HB max / 96 HRB max |
| Modulus of Elasticity | 193 GPa |
| Thermal Expansion (20-100°C) | 15.9 µm/m·°C |
| Thermal Conductivity | 16.2 W/m·K |
| Density | 8.00 g/cm³ |
| Melting Range | 1375-1400°C |
| Heat Treatment | Solution Annealed |
| Max Service Temperature | 815°C |
| Standard/Parameter | Details |
|---|---|
| Bolt Standard | ASME B18.2.1, DIN 931/933 |
| Stud Bolt Standard | ASME B16.5, MSS SP-75 |
| Nut Standard | ASTM A194 Grade 8M |
| Washer Standard | ASME B18.22.1 |
| Thread Form | UNC, UNF, Metric Coarse |
| Diameter Range | M6 to M100 / 1/4" to 4" |
| Length Range | 20mm to 500mm |
| Available Product Forms | Hex Bolts, Studs, Screws, Threaded Rods |
| Custom Sizes | Available on request |
| Manufacturing Standards | ASTM A193/A193M |
| Inspection Standards | NACE MR0175, PMI Testing |
| Surface Finish | Passivated, Black Oxide Optional |
Applications
