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ASTM A320/A320M Grade L70 Impact Tested Chromium-Molybdenum Bolting
Premium Low-Temperature Fasteners - AISI 4140 Impact Verified
ASTM A320/A320M Grade L70 is the impact-tested designation of the standard L7 grade, offering verified notch toughness at -100°F for critical bolting applications. Sharing the same 0.38-0.48% carbon and 0.80-1.10% chromium chemistry as standard L7, L70 provides additional quality assurance through mandatory Charpy impact testing. ASTM A320 specification is preferred for offshore platforms, cold storage facilities, and petrochemical equipment where documented low-temperature performance is essential for safety compliance.
ASTM A320/A320M Grade L70 Stud Bolts Properties
ASTM A320/A320M Grade L70 Stud Bolts Chemical Requirements
Ferritic Steels
| Grade Symbol | Description | C | Mn | P, max | S, max | Si | Cr | Mo | |
|---|---|---|---|---|---|---|---|---|---|
| ASTM A320 L70 | 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/A320M Grade L70 Stud Bolts Mechanical Requirements
Ferritic Steels
| 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 L70 21/2 [65] and underA | quenched and tempered | 1100 [593] | 125[860] | 105[725] | 16 | 50 | 321 HBW or 35 HRC |
ASTM A320/A320M Grade L70 Stud Bolts Impact Test 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 L70 | - 100 | - 73 | 10 × 10 | 20 [27] | 15 [20] |
| 10 × 7.5 | 16 [22] | 12 [16] | |||
| 10 × 10 | 20 [27] | 15 [20] | |||
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