Description
Impact-tested low-temperature alloy-steel bolting
ASTM A320 L7 Low Temperature Stud Bolts
ASTM A320 Grade L7 fully threaded stud bolts for low-temperature flange, valve, fitting and pressure-equipment joints, manufactured and tested to the ordered project requirements.
Quick answer
ASTM A320 Grade L7 is an alloy-steel bolting grade for low-temperature service. Its key distinction from similar high-pressure grades is the A320 low-temperature qualification, including the impact-test requirements and test temperature specified by the standard and purchase order.
Product at a glance
What are ASTM A320 L7 stud bolts?
ASTM A320 L7 stud bolts are heat-treated alloy-steel bolting components intended for pressure vessels, valves, flanges and fittings in low-temperature service. Impact toughness is a procurement-critical requirement, so the inquiry should state the governing standard edition and any project-specific test temperature or energy criteria.
L7 can share similar alloy families with other bolting grades, but it is not simply B7 renamed for cold weather. Material certification, heat treatment, impact testing, finished dimensions and matching nut qualification must support the exact A320 order.
ASTM A320 L7 stud bolt specifications
| Material | Heat-treated alloy steel meeting ASTM A320/A320M Grade L7 |
|---|---|
| Low-temperature test | Charpy impact testing at the specified test temperature and acceptance criteria |
| Configuration | Fully threaded stud bolt; double-end studs by approved drawing |
| Threads | UNC, 8UN or project-specified series and class to ASME B1.1 |
| Dimensions | ASME B18.31.2, flange bolting schedule or approved drawing |
| Matching nuts | ASTM A194 Grade 7 or other project-specified compatible nut, with required impact qualification |
| Finish options | Plain, black or approved low-temperature coating system |
| Documentation | MTC, impact results, mechanical tests, hardness, dimensions and traceability |
Final dimensions, tolerances, heat treatment, mechanical properties, impact or hardness requirements, coating and acceptance criteria follow the purchase order and the contractually specified standard edition.
Why specify this grade?
Select L7 when the approved material specification requires alloy-steel bolting qualified for low-temperature service. The grade is common in low-temperature pressure systems where tensile properties alone are not sufficient and impact toughness must be demonstrated.
Critical engineering note
The impact-test temperature is not automatically the minimum design metal temperature of the complete flange joint. The designer must correlate code rules, thickness, stress, flange and nut materials, gasket behaviour and actual operating or upset conditions.
Stud, nut and finish options
Typical applications
Quality, inspection and documentation
For L7, the certificate package should identify the impact-test temperature and results, not merely state that the material is suitable for low temperature. Heat traceability and the required nut documentation are maintained across the assembly.
- EN 10204 3.1 material test certificate when ordered
- Heat-number and manufacturing-batch traceability
- Chemical composition and mechanical-property results
- Hardness testing at the frequency required by the ordered grade
- Charpy impact testing for low-temperature grades as specified
- Dimensional inspection and calibrated thread gauging
- Coating thickness or surface-condition inspection when applicable
- Third-party inspection, marking and export packing by agreement
Information required for quotation
- ASTM standard, grade and contractually required edition
- Stud diameter, overall length, thread series and thread class
- Quantity and whether two nuts per stud are required
- Matching nut specification, grade, style and finish
- Plain, coated or plated finish and the approved coating system
- Design temperature, impact-test temperature and sour-service requirements when relevant
- MTC, PMI, hardness, impact, coating and third-party inspection requirements
- Delivery destination, packing method and required schedule
Frequently asked questions
What is ASTM A320 Grade L7?
L7 is a heat-treated alloy-steel bolting grade under ASTM A320/A320M for low-temperature pressure vessels, valves, flanges and fittings.
Is ASTM A320 L7 the same as ASTM A193 B7?
No. Although related alloy steels may be used, A320 L7 carries low-temperature requirements, including impact testing. The grades are not interchangeable by name.
What impact-test temperature applies to L7?
Use the test temperature and acceptance criteria required by the ordered ASTM edition, governing design code and project specification. State any project-specific value in the inquiry.
Which nuts are used with L7 stud bolts?
ASTM A194 Grade 7 or another compatible project-specified nut may be used, with impact testing and documentation as required by ASTM A320 and the purchase order.
Related stud bolt products
Reference standards
Material requirements are controlled by ASTM A320/A320M. Matching heavy hex nut requirements are specified separately under ASTM A194/A194M when applicable. Thread form and stud dimensions may reference ASME B1.1 and ASME B18.31.2, subject to the purchase order. Always state the required edition instead of assuming the latest edition applies to an existing project.
Request a technical quotation
Send your flange bolting schedule, bill of materials, drawing or project specification. SASA FLANGE will review the grade, nuts, threads, dimensions, finish, documentation and delivery requirements before quotation.
