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    2. Grade 8MLCUN Nuts

    ASTM A194 Grade 8MLCUN Heavy Hex Nuts — UNS S31254

    Super austenitic stainless steel nuts engineered for highly corrosive service environments.

    ASTM A194/A194M Grade 8MLCuN Nuts are premium stainless steel heavy hex nuts developed for exceptional resistance against pitting, crevice corrosion, and chloride attack. These nuts are extensively used in offshore oil & gas, seawater handling systems, and chemical processing plants. They are commonly paired with ASTM A193/A193M corrosion-resistant bolting materials for critical industrial applications. ASTM A320/A320M low-temperature service standards, ASTM A563M structural requirements, and ASTM F2437/F2437M fastening systems are also associated with these advanced fastening solutions.

    ASTM A194/A194M Grade 8MLCUN Chemical Requirements

    Grade Description
    and
    UNS Designation    		 C Mn P SE Si Cr Ni Mo N Cu
    ASTM A194/A194M Grade 8MLCuN (254) S31254 0.020 1.00 0.030 0.010 0.80 19.5-20.5 17.5-18.5 6.0-6.5 0.18-0.22 0.50-1.00
    • (A) Total aluminum, soluble and insoluble.
    • (B) Maximum, unless minimum or range is indicated.
    • (C) Where ellipses (...) appear in this table there is no requirement.

    ASTM A194/A194M Grade 8MLCUN Hardness Requirements

    Grade and Type Completed Nuts
    Brinell Hardness Rockwell Hardness
    C Scale B Scale
    ASTM A194/A194M Grade 8MLCUN 126 to 300 32 max 60 min

    ASTM A194/A194M Grade 8MLCUN Proof Load Requirements (Inch Series)

    Nominal Size, in. Threads per Inch Stress Area in. 2 Proof Load, lbf A
    Grade 8MLCUN
    Heavy HexH HexI
    1/4 20 0.0316 2 540 2 380
    5/16 18 0.0524 4 190 3 930
    3/8 16 0.0774 6 200 5 810
    7/16 14 0.1063 8 500 7 970
    1/2 13 0.1419 11 350 10 640
    9/16 12 0.182 14 560 13 650
    5/8 11 0.226 18 080 16 950
    3/4 10 0.334 26 720 25 050
    7/8 9 0.462 36 960 34 650
    1 8 0.606 48 480 45 450
    11/8 8 0.790 63 200 59 250
    11/4 8 1.000 80 000 75 000
    13/8 8 1.233 98 640 92 450
    11/2 8 1.492 119 360 111 900
    • (A) See limit for proof load test in 8.2.2.1. The proof load for jam nuts shall be 46 % of the tabulated load.
    • (B) Based on proof stress of 130 000 psi.
    • (C) Based on proof stress of 120 000 psi.
    • (D) Based on proof stress of 150 000 psi.
    • (E) Based on proof stress of 135 000 psi.
    • (F) Based on proof stress of 175 000 psi.
    • (G) Based on proof stress of 150 000 psi.
    • (H) Based on proof stress of 80 000 psi.
    • (I) Based on proof stress of 75 000 psi.

    ASTM A194/A194M Grade 8MLCUN Proof Load Requirements (Metric Series)

    Nominal Size, mm Threads Pitch Stress Area mm 2 Proof Load, kNA
    Grade 8MLCUN
    Heavy HexH HexI
    M6 1.0 20.1 11.1 10.4
    M8 1.25 36.6 20.1 18.8
    M10 1.50 58.0 31.9 29.9
    M12 1.75 84.3 46.4 43.4
    M14 2.0 115.0 63.3 59.2
    M16 2.0 157.0 86.4 80.9
    M20 2.5 245.0 134.8 126.2
    M22 2.5 303.0 166.7 156.0
    M24 3.0 353.0 194.2 181.8
    M27 3.0 459.0 252.5 236.4
    M30 3.5 561.0 308.6 288.9
    M36 4.0 817.0 449.4 420.8
    • (A) See limit for proof load test in 8.2.2.1. The proof load for jam nuts shall be 46 % of the tabulated load.
    • (B) Based on proof stress of 895 MPa.
    • (C) Based on proof stress of 825 MPa.
    • (D) Based on proof stress of 1035 MPa.
    • (E) Based on proof stress of 930 MPa.
    • (F) Based on proof stress of 1205 MPa.
    • (G) Based on proof stress of 1035 MPa.
    • (H) Based on proof stress of 550 MPa.
    • (I) Based on proof stress of 515 MPa.

    Related A194 Grades & References

    ASTM A194 Grade 8MLCUN (UNS S31254) belongs to the austenitic family. Related grades: Grade 8, Grade 8M, Grade 8MA, Grade 8C, Grade 8T. Dimensions: ASME B18.2.2 heavy hex. Full standard: ASTM A194 PDF. A194 hub.

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