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| Specification | Value |
|---|---|
| UNS Number | K21590 |
| ASTM Standard | A193/A193M Grade B16 |
| Tensile Strength | 860 MPa min |
| Yield Strength | 725 MPa min |
| Max Service Temperature | 593°C |
| Hardness | 321 HB max |
| Element | Composition (%) |
|---|---|
| C | 0.36–0.47 |
| Cr | 0.80–1.15 |
| Mo | 0.50–0.65 |
| V | 0.25–0.35 |
| Mn | 0.45–0.70 |
| Si | 0.15–0.35 |
| P | ≤0.035 |
ASTM A193 Grade B16 is a chromium-molybdenum-vanadium alloy steel engineered for high-temperature bolting applications. Chromium provides oxidation resistance and improves hardenability, while molybdenum enhances high-temperature strength and resistance to creep deformation. Vanadium refines the grain structure and contributes to secondary hardening during tempering, allowing the material to retain mechanical strength at elevated temperatures. Carbon content is carefully balanced to achieve the required tensile and yield strength without compromising toughness. This combination of alloying elements results in a fastener material capable of maintaining dimensional stability and load-bearing capacity under prolonged thermal exposure.
The engineering benefits of Grade B16 include excellent resistance to thermal relaxation, making it ideal for high-pressure, high-temperature service in power generation, petrochemical, and refinery applications. Its quenched and tempered condition ensures a favorable balance of strength and ductility, while its resistance to hydrogen embrittlement and stress corrosion supports long-term reliability. These properties make Grade B16 fasteners particularly suitable for flange connections, pressure vessels, and piping systems operating above 400°C, where maintaining bolt preload is critical to joint integrity.
Specifications
ASTM A193 Grade B16 Fasteners are high-strength alloy steel fasteners specified by ASTM A193 for elevated-temperature pressure applications, with dimensional and mechanical requirements governing bolt, nut, and stud performance. Their technical data centers on strength, hardness, and size tolerances for reliable service in demanding assemblies.
| Property | Value |
|---|---|
| Tensile Strength | 860 MPa min |
| Yield Strength | 725 MPa min |
| Elongation | 18% min |
| Reduction of Area | 50% min |
| Hardness | 321 HB max |
| Modulus of Elasticity | 200 GPa |
| Thermal Expansion | 12.2 µm/m·°C |
| Density | 7.86 g/cm³ |
| Max Service Temperature | 593°C |
| Standard | Details |
|---|---|
| Bolt Standard | ASME B18.2.1 |
| Stud Bolt Standard | ASME B16.5 / API 6A |
| Nut Standard | ASME B18.2.2 / A194 Grade 4/7 |
| Thread Form | UNC, UN8, 8-Thread Series |
| Diameter Range | 1/4" to 4" |
| Length Range | Up to 24 inches |
| Product Forms | Bolts, studs, screws, threaded rods |
| Custom Sizes | Available on request |
Applications
