Related Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
ASTM A320 / ASME SA-320 Grade L7 Stud Bolts (UNS G41400)
AISI 4140 / 4142 chromium-molybdenum alloy steel · Quench-and-tempered
ASTM A320 Grade L7 is the most widely used low-temperature alloy steel bolting grade, manufactured from AISI 4140 or 4142 chromium-molybdenum steel that has been quenched and tempered. Assigned UNS number G41400, Grade L7 meets a minimum tensile strength of 125 ksi (860 MPa) and yield strength of 105 ksi (725 MPa) for diameters up to 2-1/2 inches. The specification requires Charpy V-notch impact testing at -150°F (-101°C), with a minimum average energy of 40 ft-lbf (54 J) for full-size 10 × 10 mm specimens. Hardness is limited to 321 HBW maximum to ensure toughness. Grade L7 is equivalent to ASME SA-320 Grade L7 in the ASME Boiler and Pressure Vessel Code, Section II Part A.
ASTM A320 Grade L7 properties
ASTM A320 Grade L7 chemical composition
| Grade Symbol | Description | C | Mn | P, max | S, max | Si | Cr | Mo | |
|---|---|---|---|---|---|---|---|---|---|
| ASTM A320 L7 | Cr - Mo - B | Range,% | 0.38 - 0.48C | 0.75 - 1.00 | 0.035 | 0.04 | 0.15 - 0.35 | 0.80 - 1.10 | 0.15 - 0.25 |
| Product Variation, % Over or Under | 0.02 | 0.04 | 0.005 over | 0.005 over | 0.02 | 0.05 | 0.02 | ||
ASTM A320 Grade L7 mechanical properties
| Class and Grade, Diameter, in. [mm] | Heat Treatment | Minimum Tempering Temperature, °F [°C] | Tensile Strength, min, ksi [MPa] | Yield Strength, min, ksi [MPa] (0.2 % offset) | Elongation in 2 in. or 50 mm, min, % | Reduction of Area, min, % | Hardness, max |
|---|---|---|---|---|---|---|---|
| ASTM A320 L7 21/2[65] and underA | quenched and tempered | 1100 [593] | 125[860] | 105[725] | 16 | 50 | 321 HBW or 35 HRC |
ASTM A320 Grade L7 Charpy V-notch impact requirements
| Grade | Test Temperature | CVN Specimen Section Size, mm | Min Average Impact Toughness of Three Test Specimens, ft-lbf [J] | Min Impact Value of a Single Specimen of Set of Three, ft-lbf [J] | |
|---|---|---|---|---|---|
| °F | °C | ||||
| ASTM A320 L7 | - 150 | - 101 | 10 × 7.5 | 16 [22] | 12 [16] |
| 10 × 10 | 40 [54] | 30 [41] | |||
What nuts and washers are specified for ASTM A320 Grade L7?
For low-temperature service consistency, ASTM A320 Grade L7 stud bolts are paired with ASTM A194 Grade 4 or Grade 7 heavy hex nuts (Charpy-tested per A194 Supplement 3 when the service temperature drops below -50°F) and ASTM F436 hardened steel washers. A194 Grade 7 nuts are chemically equivalent to A320 L7 bolts (4140/4142 quench-and-tempered) and are the most common pairing for refinery, LNG and cryogenic pipeline service. TorqBolt supplies kit-matched A320 L7 + A194 Gr 7 + F436 sets with a single EN 10204 3.1 or 3.2 certificate covering all three components.
NORSOK M-650 qualification & EN 10204 3.1 / 3.2 certificates for A320 Grade L7
TorqBolt’s ASTM A320 Grade L7 stud bolt production route is qualified to NORSOK M-650 for North Sea oil & gas offshore service. Each manufacturing record links heat number → melt analysis → quench-and-temper batch → mechanical test → Charpy V-notch curve at -150°F → dimensional inspection → coating → dispatch. Standard certification: EN 10204 Type 3.1 (manufacturer’s test report). On request: Type 3.2 (third-party witnessed by Lloyd’s Register, DNV, BV, ABS, or TUV). The qualification packet covers ASME SA-320 L7 equivalence, NACE MR0175 / ISO 15156-2 for sour-service variants (Grade L7M), API 6A PSL-3/PSL-4, and PED 2014/68/EC for European pressure-equipment buyers. No competitor publishes this combined qualification scope for A320 Grade L7.
Related ASTM A320 grades & companion specifications
- ASTM A320 Grade L7M: same UNS G41400 chemistry, tempered at ≥620°C for NACE MR0175 sour-service hardness limits (≤22 HRC).
- ASTM A320 Grade L43: AISI 4340 Ni-Cr-Mo alloy steel; chosen when deep hardenability is required.
- ASTM A320 Grade B8: AISI 304 austenitic stainless equivalent for corrosive low-temperature service.
- ASTM A320 Grade B8M: AISI 316 molybdenum-bearing stainless for chloride exposure.
- ASME B18.31.2 inch double-end stud bolts: dimensional reference for L7 studs mating ASME B16.5 flanges.
- ASME B18.2.1 hex bolts: dimensional reference for L7 hex bolts.
ASTM A320 Grade L7: related product searches
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