Descripción
Impact-tested alloy steel bolting for low-temperature service
ASTM A320 Grade L7 Alloy Steel Heavy Hex Bolts
ASTM A320 Grade L7 alloy steel heavy hex bolts are impact-tested, quenched-and-tempered fasteners for low-temperature pressure vessels, valvulas, bridas, fittings and industrial equipment.
Cuáles son ASTM A320 L7 heavy hex bolts?
ASTM A320/A320M covers alloy steel and stainless steel bolting for low-temperature service. Grade L7 is a ferritic alloy steel grade with mechanical properties broadly comparable to B7 in common sizes, plus low-temperature Charpy impact requirements that address toughness in cold service.
When a headed bolt is required, Grade L7 can be manufactured with a heavy hex head to the dimensional basis stated on the order. The design minimum metal temperature, impact-test temperature, specimen requirements, nut toughness and complete joint specification must be provided before manufacture.
Key procurement advantages
ASTM A320 Grade L7 Alloy Steel Heavy Hex Bolts specifications
| Bolting standard | ASTM A320/A320M, ordered edition |
|---|---|
| Calificación | L7 |
| Material | Quenched-and-tempered chromium-molybdenum alloy steel |
| Service basis | Low-temperature pressure service with required impact testing |
| Head / dimensiones | Heavy hex head to ASME B18.2.1 or project drawing |
| Thread system | UNC, UNF or 8UN to ASME B1.1 según lo ordenado |
| Typical supply range | 1/2 a través de 4 in. diameter; size and impact-test requirements subject to review |
| Compatible nut | ASTM A194 Calificación 4 or Grade 7 heavy hex nut with required impact testing when specified |
| Compatible washer | ASTM F436 hardened washer or project-specified washer suitable for the service |
| Impact testing | Charpy V-notch energy and test temperature to the ordered A320 and project requirements |
| Documentación | EN 10204 3.1 MTC, Charpy results, trazabilidad del calor, mechanical and dimensional reports |
Published ranges are procurement guidance, no es una aprobación de diseño. The purchase order, governing code, standard edition and approved drawing control final dimensions, properties and acceptance criteria.
How to select this grade
| Punto de selección | ASTM A320 Grade L7 Alloy Steel Heavy Hex Bolts | When to review another grade |
|---|---|---|
| Primary service | Low-temperature pressure equipment | A193 B7 for high-pressure or elevated-temperature service |
| Impact testing | Required to the ordered L7 basis | Not the defining B7 requirement |
| Common nut | A194 Grade 4 o 7 with impact requirements as ordered | A194 Grade 2H commonly used with B7 |
| Selection input | Design minimum temperature and Charpy criteria | Presión, temperature and equipment specification |
Matching nuts, washers and coatings
Cold-service performance depends on the entire assembly. Specify impact-tested ASTM A194 Calificación 4 or Grade 7 heavy hex nuts where required, compatible hardened washers, and the project test temperature. A room-temperature nut or unverified replacement can undermine the low-temperature bolting specification.
Aplicaciones típicas
| Industria | Typical duty | Why this grade is specified |
|---|---|---|
| LNG | Liquefaction, storage and transfer equipment | Impact-tested alloy steel for specified low temperatures |
| Refrigeration | Compressors, vessels and cold piping equipment | Verified toughness below ambient temperature |
| Natural gas | Cold-climate and low-temperature process skids | Traceable L7 material and impact records |
| Procesamiento químico | Low-temperature valves and pressure equipment | Heavy hex headed configuration with cold-service documentation |
Application examples do not replace engineering review. Confirm load, temperatura, presión, environment, joint design, installation method and governing code before selection.
Inspección, pruebas y documentación
SASA FLANGE can prepare a project-specific inspection and documentation package. Requirements must be agreed before manufacture so the test frequency, traceability and acceptance criteria are built into the production route.
Test temperature, absorbed energy and specimen orientation recorded as ordered.
Properties verified for the finished-product diameter and heat-treatment condition.
Bolt, nut and washer records linked to the ordered assembly.
Head, longitud, body and thread gauging documented for project acceptance.
RFQ and ordering checklist
- ASTM standard, calificación, type and required edition
- Heavy hex dimensional standard or approved drawing
- Diámetro, overall length and thread length
- Thread series, pitch and class of fit
- Matching nut and washer standards and grades
- Acabado superficial, revestimiento, lubrication and color
- Temperatura de servicio, environment and design code
- Cantidad, calificación, packing and delivery destination
- EN 10204 MTC, mechanical, impacto, dureza, PMI and NDE requirements
- Third-party inspection or project hold points
Preguntas frecuentes
Cuáles son ASTM A320 L7 heavy hex bolts?
They are quenched-and-tempered alloy steel headed bolts with low-temperature impact requirements for pressure equipment and special cold-service applications.
What is the difference between A320 L7 and A193 B7?
L7 adds low-temperature Charpy impact requirements. B7 is primarily specified for high-pressure or elevated-temperature service without L7 being automatically interchangeable.
Which nut is used with L7 bolts?
ASTM A194 Calificación 4 or Grade 7 heavy hex nuts are commonly specified, with supplementary impact testing when required by the low-temperature design.
Is L7 suitable for LNG service?
It is widely considered for LNG and low-temperature equipment, but the materials engineer must confirm the design temperature, impact-test criteria, joint design and applicable code.
Which documents prove low-temperature compliance?
Request the EN 10204 3.1 MTC, Charpy impact report, heat-treatment records, mechanical results, heat traceability and dimensional inspection.
Request a heavy hex bolt quotation
Send the standard, calificación, drawing, tamaño, assembly, service condition, quantity and documentation requirements for technical review.
