| Feature | Grade B7 (Alloy Steel) | Grade B8 (Stainless Steel 304) |
|---|---|---|
| Material | Chromium-Molybdenum Alloy Steel | Austenitic Stainless Steel (AISI 304) |
| Tensile Strength | 125,000 PSI (860 MPa) | 75,000 PSI (Class 1) or 125,000 PSI (Class 2) |
| Corrosion Resistance | Low (Requires coating like PTFE or Cadmium) | High |
| Temperature Range | Up to 400°C (750°F) | Cryogenic up to 800°C (1472°F) for low stress |
| Typical Mating Nut | ASTM A194 Grade 2H | ASTM A194 Grade 8 |
The Verdict
Use B7 for high-pressure, high-stress applications where raw tensile strength is paramount (typical oil & gas flanges). Use B8 when the primary concern is corrosion resistance or cryogenic temperatures.
Frequently Asked Questions
What is the difference between B8 Class 1 and Class 2?
Class 1 is carbide solution treated, offering standard strength. Class 2 is strain hardened, which significantly increases its tensile and yield strength to match B7 levels.