Patriot Bolt machines ASTM A193 Grade B7 stud bolts from certified chromium-molybdenum round bar (AISI 4140 or 4142), quenched and tempered to the specification. B7 is the most widely used alloy steel bolting grade for pressure flanges, valves and fittings in refining, petrochemical, oil and gas and power service.
We make B7 studs in any length and thread, to your purchase order or drawing, and supply the matching A194 2H heavy hex nuts. Every order ships with mill test reports traceable to the heat.
A193 B7 Stud Bolts at a Glance
- Specification
- ASTM A193 / ASME SA193 Grade B7
- Material
- AISI 4140 / 4142 chrome-moly steel, quenched and tempered
- Strength
- 125 ksi min tensile, 105 ksi min yield (2-1/2 in and under)
- Hardness
- 321 HBW / 35 HRC max
- Matching nut
- A194 Grade 2H heavy hex
- Configurations
- Fully threaded, double-end and tap-end
Why Engineers Specify A193 B7 Stud Bolts
B7 is the default stud for ASME B16.5 and B16.47 flanges because it combines high strength, predictable heat treatment and wide availability.
- High strength. 125 ksi minimum tensile and 105 ksi minimum yield up to 2-1/2 in let the joint reach high bolt preload.
- Consistent properties. Quenching and tempering at 1100 °F minimum gives a uniform, tough structure through the section.
- Moderate temperature range. B7 is the economical choice for most flanges up to about 800 °F. Hotter joints usually move to B16.
- Simple matching. A194 Grade 2H nuts are the standard companion.
B7 is not acceptable for sour (H2S) service under NACE MR0175. Specify B7M instead.
A193 B7 Stud Bolt Specifications
ASTM A193 sets B7 properties by diameter. Larger studs have lower minimums because the core of a thick section cannot harden as fully.
| Diameter | Tensile, min | Yield (0.2%), min | Elongation, min | Reduction of area, min | Hardness, max |
|---|---|---|---|---|---|
| 2-1/2 in and under | 125 ksi | 105 ksi | 16% | 50% | 321 HBW / 35 HRC |
| Over 2-1/2 to 4 in | 115 ksi | 95 ksi | 16% | 50% | 321 HBW / 35 HRC |
| Over 4 to 7 in | 100 ksi | 75 ksi | 18% | 50% | 321 HBW / 35 HRC |
For low-temperature service, the same steel is ordered to A320 L7 with Charpy impact testing at −150 °F.
A193 B7 Chemical Composition
| Element | Weight % |
|---|---|
| Carbon | 0.38–0.48 |
| Manganese | 0.75–1.00 |
| Phosphorus | 0.035 max |
| Sulfur | 0.040 max |
| Silicon | 0.15–0.35 |
| Chromium | 0.80–1.10 |
| Molybdenum | 0.15–0.25 |
Limits per the current edition of the specification. The mill test report for your heat is the controlling document.
Stud Configurations
- Fully threaded studs, threaded end to end, for flange bolting where grip length varies.
- Double-end studs, threaded on both ends with an unthreaded center.
- Tap-end studs, with one end made to thread into a tapped hole.
Send the thread length on each end for double-end and tap-end studs.
Applications and Industries
- Refining and petrochemical: Process piping flanges, heat exchangers and valve bonnets. See Petrochemical & Refining.
- Oil and gas: Wellhead, manifold and pipeline flanges in non-sour service. See Oil & Gas.
- Power generation: Pump, valve and piping flanges at moderate temperature. See Power Generation.
Certification and Traceability
Patriot Bolt is ISO 9001:2015 certified. Each B7 order includes mill test reports traceable to the heat, along with a certificate of conformance to the specification on your purchase order.
Studs are marked with the grade symbol and our identification, as the specification requires.
Compare B7 with other bolting grades in our Fastener Materials Matrix.
A193 B7 Stud Bolts FAQ
What is the difference between B7 and B7M?
B7M is the same chrome-moly steel tempered to a lower hardness, 235 HBW maximum, with 100 ksi minimum tensile. Every B7M stud is hardness tested. The lower hardness makes B7M acceptable for sour service, where B7 is not.
Which nut goes with a B7 stud?
The standard companion is the ASTM A194 Grade 2H heavy hex nut. Grade 7 nuts are also used where the design calls for an alloy steel nut.
What temperature can B7 handle?
B7 is generally used up to about 800 °F. Above that, B16 holds its clamp load better. Follow the allowable stresses in your design code for the exact limit.
Can you make B7 studs to my drawing?
Yes. We machine B7 studs in any diameter, length and thread, including tap-end and reduced-shank designs, from your drawing or purchase order.
Request a Quote
Send us the stud configuration, diameter, length, thread, specification and quantity, or upload your drawing. Our team will confirm the material and lead time. Call (281) 581-0176 or request a quote.
Also in B7: A193 B7 fasteners hub · A194 2H heavy hex nuts · Heavy hex bolts · All stud bolts