ASTM A194
Grade 7L & 7ML
Low-Temperature Nuts
Why Impact Testing Matters Here
Grade 7L and Grade 7ML share the same chromium-molybdenum alloy steel base as our standard Grade 7 — the distinguishing requirement is Charpy V-notch impact testing performed at a specified low temperature, confirming the material retains adequate toughness (resistance to brittle fracture) at the actual minimum service temperature the joint will experience, not just at room temperature.
This distinction matters because steel’s fracture behavior changes fundamentally as temperature drops — a perfectly strong nut at ambient temperature can fail suddenly and brittlely at cryogenic or sub-zero temperatures if its composition and grain structure aren’t controlled for low-temperature toughness. Charpy testing is the standard method for verifying that toughness margin is genuinely present, not simply assumed from room-temperature mechanical properties.
Grade 7L and 7ML are the direct nut counterparts to ASTM A320 Grade L7 and L7M stud bolts — A320 is the specification governing low-temperature service bolting broadly, and the L7/L7M grades within it are among its most common designations, paired here with A194’s matching low-temperature nut grades under the same testing philosophy.
Akbar Fasteners Pvt. Ltd. exports to over 50 countries, and we manufacture Grade 7L and 7ML to order with low-temperature impact testing performed and documented under our ISO 9001:2015 quality system — please confirm your specified test temperature when ordering.
A Note on Confirming Your Test Temperature
Low-temperature grades within the A194/A320 family are typically qualified to a specific minimum design metal temperature stated in the project specification (common examples include -20°F/-29°C, -50°F/-46°C, and -150°F/-101°C for cryogenic service, though the exact figure is always project-specific). We manufacture and impact-test to the temperature your governing specification calls for — please include this figure with your inquiry so we can confirm testing and documentation accordingly.
Where This Grade Genuinely Applies
Genuine Low-Temperature Toughness
Charpy impact testing confirms real resistance to brittle fracture at the specified service temperature.
Correct Default Pairing With L7/L7M Studs
Matched material and low-temperature qualification for cryogenic bolted-joint compatibility.
Available in Inch (7L) or Metric (7ML)
Manufactured to the sizing convention your project drawings specify.
Verified Impact Test Documentation
Charpy test results provided at your specified minimum design metal temperature.
Choosing Between Related Alloy Steel Grades
Grade 7
Same chromium-molybdenum base, no low-temperature impact testing — the correct choice above 0°F/-18°C.
View Grade 7 →Grade 7L / 7ML (This Page)
Same chromium-molybdenum base, Charpy-tested for genuine cryogenic and low-temperature service.
You Are HereGrade 7M
Same chromium-molybdenum base, hardness restricted for NACE sour service instead of low temperature.
View Grade 7M →Grade 7 vs Grade 7L/7ML — Quick Reference
Confirming whether the actual minimum design metal temperature genuinely requires impact-tested toughness before specifying the low-temperature grade. This table is the quick reference we use with buyers before quoting.
| Aspect | Grade 7 | Grade 7L / 7ML |
|---|---|---|
| Base Material | Chromium-molybdenum alloy steel | Identical composition |
| Impact Testing | Not required | Charpy V-notch, at specified low temperature |
| Matching Bolt | ASTM A193 Grade B7 | ASTM A320 Grade L7 / L7M |
| Best Suited For | Ambient to elevated temperature | Genuine low-temperature/cryogenic service |
Grade 7L / 7ML Specification Details
Nominal Composition
- Chromium Present, Alloy Grade
- Molybdenum Present, Alloy Grade
- Base Type Low-Alloy Steel
- Composition Same as Grade 7
Typical Mechanical Range
- Impact Testing Charpy V-Notch, Low Temp
- Test Temperature Per Governing Specification
- Condition Quenched and Tempered
- Proof Load Per ASTM A194 Grade 7L/7ML
Fastener Types We Manufacture
- Hex Nuts Standard & Heavy Hex
- Jam Nuts Thin Profile
- Sizing Inch (7L) or Metric (7ML)
- Custom Sizes On Request
Application Areas
Wherever the specified minimum design metal temperature is genuinely low enough to require impact-tested toughness.
LNG & Cryogenic Storage Equipment
genuine low-temp exposure
Cold Climate Piping & Structures
below the low-temp threshold
Refrigerated Process Equipment
bolted assemblies
Low-Temperature Pressure Vessels
ambient design temperature
Standard Export Documentation
Prepared as standard practice for every Grade 7L or 7ML nut shipment.
Mill Test Certificate (MTC)
Heat number, chemical composition, and mechanical property verification for every lot.
Charpy Impact Test Report
Confirms toughness at the specified minimum design metal temperature.
Certificate of Conformance
Confirms the shipment matches the purchase order grade/size specification in full.
Certificate of Origin (COO)
Confirms India as country of manufacture for destination customs purposes.
Dimensional Inspection Report
Confirms correct inch or metric thread sizing per your specified sizing convention.
Commercial Invoice & Packing List
Itemized value, Incoterm, and detailed carton/weight breakdown for customs clearance.
Internationally Recognised Standards Coverage
Related Fastener Grades & Materials
ASTM A194 Grade 7
Our standard chromium-molybdenum grade, for ambient-to-elevated temperature service.
View Grade 7 →ASTM A194 Grade 7M
Our restricted-hardness variant, for NACE sour service instead of low-temperature service.
View Grade 7M →ASTM A194 Grade 2 / 2M
Our everyday quenched-and-tempered grade, matching ASTM A193 Grade B7 for non-cryogenic service.
View Grade 2 / 2M →Stainless Steel Fasteners Manufacturer India
Our broader fastener manufacturing capability across all major carbon, alloy, and stainless grades.
View SS Manufacturer Guide →Cryogenic or
Low-Temperature Service?
Share your minimum design metal temperature and sizing requirement — we’ll confirm testing, manufacturability, and quote with full documentation. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Sales: +91 724 0000 733 · Support: +91 800 9315 333 · sales@akbarfasteners.in