Patriot Bolt machines ASTM A194 Grade 7 heavy hex nuts from chromium-molybdenum steel, quenched and tempered at 1100 °F minimum. Grade 7 is the usual nut for A193 B16 studs in hot service and, as Grade 7L with Charpy impact testing, for A320 L7 and L43 studs in low-temperature service.
We make Grade 7 and 7L nuts alone or with matching studs. Every order ships with mill test reports traceable to the heat, plus impact results for 7L.
A194 Grade 7 Heavy Hex Nuts at a Glance
Why Engineers Specify A194 Grade 7 Nuts
- Alloy steel. Chrome-moly steel with a 1100 °F minimum temper holds up better than carbon steel nuts in hot service.
- Full strength. 175 ksi proof stress at every size.
- Low-temperature option. A320 requires nuts for L7 and L43 studs to be impact tested. Grade 7 nuts tested at −150 °F are marked 7L.
- One nut, several studs. Grade 7 pairs with B16, L7, L43 and B7.
Older specifications sometimes list A194 Grade 4 with these studs. ASTM withdrew Grade 4 in 2017, and Grade 7 is the usual replacement.
A194 Grade 7 Specifications
Grade 7 has one proof stress and hardness range for all heavy hex sizes.
| Grade | Proof stress | Hardness | Impact test |
|---|---|---|---|
| 7 | 175 ksi | 248–327 HBW / 24–35 HRC | — |
| 7L | 175 ksi | 248–327 HBW / 24–35 HRC | Charpy at −150 °F per A320 |
For sour service, the hardness-limited version is Grade 7M.
A194 Grade 7 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.
Nut Styles
- Heavy hex nuts to ASME B18.2.2, the standard style for flange studs.
- Heavy hex jam nuts where a thinner nut is needed.
- Threads: UNC through 1 in and 8UN above 1 in, the usual flange series, or the thread on your drawing.
Applications and Industries
- Power generation: Steam turbine and high-pressure steam flanges with B16 studs. See Power Generation.
- LNG and cryogenic: 7L nuts with L7 and L43 studs. See Oil & Gas.
- Refining: Hot hydrocarbon lines and valve bonnets. See Petrochemical & Refining.
Certification and Traceability
Patriot Bolt is ISO 9001:2015 certified. Each Grade 7 order includes mill test reports traceable to the heat, along with a certificate of conformance to the specification on your purchase order.
Nuts are marked with the grade symbol and our identification on one face. 7L certifications include the Charpy impact results.
Compare Grade 7 with other bolting grades in our Fastener Materials Matrix.
A194 Grade 7 Heavy Hex Nuts FAQ
What is the difference between Grade 7 and 7L?
The material and strength are the same. 7L nuts are also Charpy impact tested to the A320 procedure for low-temperature service.
Can I still order A194 Grade 4 nuts?
ASTM withdrew Grade 4 in 2017. Where an older specification lists Grade 4 or 7, Grade 7 is normally used. Check your project specification.
Which nut goes with B16 studs?
A194 Grade 7. Its chrome-moly steel and higher temper suit the same high-temperature service as B16.
Do you make the matching studs?
Yes. We machine B16, L7 and L43 stud bolts, so the stud and nuts can come from one source.
Request a Quote
Send us the alloy, nut style, thread size, specification and quantity, or upload your drawing. Our team will confirm the material and lead time. Call (281) 581-0176 or request a quote.
Related: B16 stud bolts · L7 stud bolts · L43 stud bolts · All nuts