| Standard | ASTM A194 / ASME B18.2.2 · A194M Grade 7L / Grade 7M |
|---|---|
| Material | ASTM A194 Grade 7L impact-tested / Grade 7M controlled-hardness alloy steel |
| Strength Grade | Grade 7L / Grade 7M |
| Size Range | M12-M64 / 1/2"-4" |
| Surface Treatment | Plain / Black Oxide / Phosphate / PTFE Coated / Zinc Plated |
Product Description
This page combines ASTM A194/A194M Grade 7L and Grade 7M alloy-steel heavy hex nuts for low-temperature pressure bolting. Grade 7L is paired with ASTM A320 Grade L7 stud bolts when the low-temperature qualification requires impact testing of the nut. Grade 7M controls maximum hardness and is paired with ASTM A320 Grade L7M studs.
Grade 7L and Grade 7M are not interchangeable labels. The applicable ASTM A194 edition and purchase order govern proof load, heat treatment, hardness, impact testing and marking. Thread fit, coating allowance and lubricant condition must also match the selected L7 or L7M stud bolt.
A Grade 7M marking does not by itself establish NACE MR0175 / ISO 15156 or NACE MR0103 / ISO 17945 compliance. State the nut and stud grades, minimum design temperature, Charpy test temperature and acceptance criteria, hardness limits, thread, coating, certificate scope and any applicable sour-service standard in the RFQ.
| Product type | ASTM A194 Grade 7L and Grade 7M alloy steel heavy hex nuts |
|---|---|
| Standard | ASTM A194/A194M Grade 7L / Grade 7M / ASME B18.2.2 dimensional reference |
| Grade characteristic | Grade 7L impact-tested low-temperature route; Grade 7M controlled-maximum-hardness route |
| Matched stud grade | ASTM A320 Grade L7 with Grade 7L; ASTM A320 Grade L7M with Grade 7M |
| Size range | M12-M64 / 1/2 in-4 in |
| Thread type | UNC / 8UN / metric thread matched to the stud specification |
| Surface finish | Plain / Black oxide / Phosphate / PTFE coated / Zinc plated |
| Low-temperature boundary | Minimum design temperature, Charpy test temperature and acceptance criteria must be confirmed for the Grade 7L route |
| Sour-service boundary | NACE MR0175 / ISO 15156 or NACE MR0103 / ISO 17945 only when explicitly invoked and verified |
| Documentation | MTC, Grade 7L impact report, proof-load or hardness report, heat traceability, thread inspection and coating report as specified |
| Parameter | 1 | 1/4 | 1/2 | 1-1/8 | 1-1/4 | 1-3/8 | 1-1/2 | 1-5/8 | 1-3/4 | 1-7/8 | 2 | 2-1/4 | 2-1/2 | 2-3/4 | 3 | 3/8 | 3/4 | 3-1/4 | 3-1/2 | 3-3/4 | 4 | 5/16 | 5/8 | 7/16 | 7/8 | 9/16 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| P | 8|12|20 | 20|28|32 | 13|20|28 | 7|12|18 | 7|12|18 | 6|12|18 | 6|12|18 | 6|12|18 | 5|8|12 | 6 | 4.5 | 4.5 | 4 | 4 | 4 | 16|24|32 | 10|16|20 | 4 | 4 | 4 | 4 | 18|24|32 | 11|18|24 | 14|20|28 | 9|14|20 | 12|18|24 |
| s/min | 1.575 | 0.448 | 0.85 | 1.756 | 1.938 | 2.119 | 2.3 | 2.481 | 2.662 | 2.844 | 3.025 | 3.388 | 3.75 | 4.112 | 4.475 | 0.669 | 1.212 | 4.838 | 5.2 | 5.562 | 5.925 | 0.546 | 1.031 | 0.728 | 1.394 | 0.909 |
| s/max | 1.625 | 0.5 | 0.875 | 1.812 | 2 | 2.188 | 2.375 | 2.562 | 2.75 | 2.938 | 3.125 | 3.5 | 3.875 | 4.25 | 4.625 | 0.688 | 1.25 | 5 | 5.375 | 5.75 | 6.125 | 0.562 | 1.062 | 0.75 | 1.438 | 0.938 |
| e/min | 1.796 | 0.556 | 0.969 | 2.002 | 2.209 | 2.416 | 2.622 | 2.828 | 3.035 | 3.242 | 3.449 | 3.862 | 4.275 | 4.688 | 5.102 | 0.763 | 1.382 | 5.515 | 5.928 | 6.341 | 6.755 | 0.622 | 1.175 | 0.83 | 1.589 | 1.037 |
| e/max | 1.876 | 0.577 | 1.01 | 2.093 | 2.309 | 2.526 | 2.742 | 2.959 | 3.175 | 3.392 | 3.608 | 4.041 | 4.474 | 4.907 | 5.34 | 0.794 | 1.443 | 5.774 | 6.207 | 6.64 | 7.073 | 0.65 | 1.227 | 0.866 | 1.66 | 1.083 |
| k/min | 0.956 | 0.218 | 0.464 | 1.079 | 1.187 | 1.31 | 1.433 | 1.556 | 1.679 | 1.802 | 1.925 | 2.155 | 2.401 | 2.647 | 2.893 | 0.341 | 0.71 | 3.124 | 3.37 | 3.616 | 3.862 | 0.28 | 0.587 | 0.403 | 0.833 | 0.526 |
| k/max | 1.012 | 0.25 | 0.504 | 1.138 | 1.251 | 1.378 | 1.505 | 1.632 | 1.759 | 1.886 | 2.013 | 2.251 | 2.505 | 2.759 | 3.013 | 0.377 | 0.758 | 3.252 | 3.506 | 3.76 | 4.014 | 0.314 | 0.631 | 0.441 | 0.885 | 0.568 |
Selection
Match Grade 7L nuts with A320 L7 studs and Grade 7M nuts with A320 L7M studs. Confirm minimum design temperature, Charpy scope, hardness, coating, lubricant and batch documents before production.
Oil and gas fastenersCompare the impact-tested L7/7L route with the controlled-hardness L7M/7M route before specifying the pressure-bolting set.
Fastener material selection guideAssembly
Manufacturing
FAQ
ASTM A320 L7 studs pair with ASTM A194 Grade 7L nuts when impact qualification of the nut is required. A320 L7M studs pair with controlled-hardness ASTM A194 Grade 7M nuts.
Grade 7L is the impact-tested low-temperature nut route commonly selected with A320 L7 studs. Grade 7M controls maximum hardness and is selected with A320 L7M studs. They should not be substituted by marking alone.
No. The 7M grade controls hardness, but the applicable NACE or ISO standard, edition, environmental limits and inspection requirements must be specified and verified separately.
Not automatically. The purchase order must state the minimum design temperature, Charpy test temperature and acceptance criteria, and the test documentation must verify them.
Send nut grade, size, thread, coating, matching L7 or L7M stud grade, minimum design temperature, Charpy and hardness requirements, certificate scope and quantity.
Send the nut grade, size, thread, coating, matching L7 or L7M stud details, minimum design temperature, Charpy and hardness requirements, certificate scope and quantity. We can quote matched L7/7L or L7M/7M flange bolting sets.
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