ASTM A193 B7 Stud Bolt — Flange Service
ASTM A193 Grade B7 is the most widely specified stud material for flange bolting in petrochemical, refining, and power generation. Made from heat-treated AISI 4140 / 42CrMo alloy steel, B7 stud bolts deliver high tensile strength with excellent performance up to about 400 °C.
Specifications
| Standard | ASTM A193 / A193M Grade B7 |
|---|---|
| Material | AISI 4140 / 42CrMo, quenched and tempered |
| Mechanical | Tensile 125 ksi min (≤ 2-1/2"), Yield 105 ksi min |
| Service Temperature | Up to ~400 °C (above this, B16 is preferred) |
| Mating Nut | ASTM A194 Grade 2H heavy hex |
| Documentation | Mill Test Certificate per heat lot, head/end stamping |
Frequently Asked Questions
When should I specify A193 B7 vs B16?
B7 is suitable up to roughly 400 °C continuous service. Above this, B16 (chromium-molybdenum-vanadium alloy) maintains strength better. Both are widely available; the choice depends on flange service temperature.
What is A193 B7M?
B7M is the same chemistry as B7 but with controlled hardness (≤ 22 HRC) for sour-service environments where stress corrosion cracking from H2S is a concern. Specifically required by NACE MR0175 / ISO 15156 in oil and gas service.
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