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    ASTM A320/A320M Grade L71 Impact Tested Carbon-Molybdenum Bolting

    Verified Low-Temperature Performance - AISI 4037 Impact Grade

    ASTM A320/A320M Grade L71 represents the impact-tested variant of the L7A specification, providing documented proof of toughness at -100°F through mandatory Charpy V-notch testing. Manufactured from AISI 4037 material with controlled carbon-molybdenum chemistry, L71 offers cost-effective reliability for moderate cryogenic applications while maintaining 125 ksi tensile strength. ASTM A320/A320M Grade L71 is bridges the gap between standard L7A and more expensive nickel-bearing alloys for sub-zero service conditions.

    ASTM A320/A320M Grade L71 Stud Bolts Properties

    ASTM A320/A320M Grade L71 Stud Bolts Chemical Requirements

    Ferritic Steels

    Grade Symbol Description C Mn P,  max S, max Si Mo
    ASTM A320 L71 C - Mo (AISI 4037) Range,% 0.38 - 0.48 0.70 - 0.90 0.035 0.04 0.15 - 0.35 0.20- 0.30
    Product Variation, % Over or Under 0.02 0.03 0.005 over 0.005 over 0.02 0.02

    ASTM A320/A320M Grade L71 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 L71 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 L71 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 L71 - 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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