| Standard | ASTM A320 · A320M Grade L7 / Grade L7M |
|---|---|
| Material | AISI 4140 / 4140H chromium-molybdenum alloy steel (ASTM A320/A320M L7 / L7M), quenched and tempered |
| Strength Grade | L7 / L7M |
| Size Range | M12 and above / 1/2 in and above |
| Surface Treatment | Plain / Black Oxide / PTFE / Zinc-Nickel with PTFE |
Product Description
We manufacture ASTM A320/A320M Grade L7 and L7M stud bolts from AISI 4140 / 4140H alloy steel bar, quenched and tempered, with Charpy impact testing at the temperature your specification requires. We supply metric sizes from M12 and imperial sizes from 1/2 in, with lengths to your drawing for LNG and cryogenic equipment, cold-climate flanges, valves, pressure vessels and process piping.
L7 or L7M: we supply both, and confirm the grade and test temperature before production.
L7 is not a relabelled B7. The alloy family is similar, but A320 carries the low-temperature impact-testing requirement, and we test and report it. If your project also calls for NACE MR0175 / ISO 15156 or NACE MR0103 / ISO 17945, send us the specification and edition with your inquiry. An M grade alone does not prove sour-service compliance.
What ships with every order
Finishes we supply: plain, black oxide, PTFE and zinc-nickel with PTFE, checked against operating temperature, nut fit and your specification.
To quote quickly, send us: minimum design temperature, required Charpy test temperature and acceptance values, diameter, length, thread, coating, nut grade and documentation requirements. We quote within one working day.
| Product type | ASTM A320 L7 and L7M low-temperature stud bolts |
|---|---|
| Standard | ASTM A320/A320M Grade L7 / Grade L7M |
| Material | AISI 4140 / 4140H chromium-molybdenum alloy steel, quenched and tempered |
| L7 selection | Higher-strength general low-temperature bolting; paired with impact-tested ASTM A194 Grade 7L nuts |
| L7M selection | Lower-strength, controlled-maximum-hardness bolting; commonly paired with ASTM A194 Grade 7M nuts |
| Impact testing | Charpy test temperature and acceptance values must follow the applicable edition, diameter and purchase order |
| Size range | M12 and above / 1/2 in and above |
| Length | Made to the customer drawing or project specification |
| Thread type | UNC / 8UN / metric thread by flange schedule or customer drawing |
| Surface finish | Plain / Black oxide / PTFE / Zinc-nickel with PTFE |
| Sour-service qualification | NACE MR0175 / ISO 15156 or NACE MR0103 / ISO 17945 only when explicitly invoked and verified |
| Documentation | Material test certificate with heat number and Charpy results, hardness and dimensional reports, and certificate of conformity with every order; third-party inspection accepted before shipment |
Manufacturing
Selection
L7 and L7M studs are used in cold process lines, valves and flange packages when project impact requirements are defined. Confirm minimum design temperature, Charpy test temperature, nut grade, coating and lubricant before production.
Oil and gas fastenersCompare the ASTM A320 low-temperature route with ASTM A193 high-temperature grades, stainless and nickel alloys before procurement.
Fastener material selection guideAssembly
FAQ
L7 is the higher-strength general low-temperature alloy-steel bolting grade. L7M has lower mechanical strength, controlled maximum hardness and grade-specific testing. Both remain subject to the impact requirements of the applicable ASTM A320 edition and purchase order.
ASTM A320 L7 studs pair with impact-tested ASTM A194 Grade 7L heavy hex nuts when low-temperature nut qualification is required. L7M studs pair with controlled-hardness ASTM A194 Grade 7M nuts.
They should not be treated as identical. Although both are chromium-molybdenum alloy-steel grades, ASTM A320 L7 follows a low-temperature service and impact-testing route. Substitution requires engineering review of temperature, impact, marking and documentation requirements.
No. L7M provides grade-specific hardness control, but the applicable NACE or ISO standard, edition, environmental limits and inspection scope must be stated and verified separately.
Send grade, diameter, overall length, thread, minimum design temperature, required Charpy test temperature and acceptance values, coating, nut grade, certificate scope and quantity.
Send the design temperature, grade, diameter, length, thread, coating, nut pairing, impact-test requirement, quantity and certificate scope. We can quote L7 with Grade 7L or L7M with Grade 7M matched sets.
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