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    2. Grade 2H Nuts

    ASTM A194 Grade 2H Heavy Hex Nuts — UNS K04100

    Widely used heavy hex nuts for high-pressure and elevated temperature industrial applications.

    ASTM A194/A194M Grade 2H Nuts are among the most commonly used heavy hex nuts for refinery, petrochemical, and pressure vessel bolting systems. These quenched and tempered nuts offer excellent tensile strength, durability, and thermal resistance. Grade 2H nuts are frequently matched with ASTM A193/A193M B7 stud bolts in flange connections and valve assemblies. They are also suitable for ASTM A320/A320M low-temperature bolting projects, while ASTM A563M and ASTM F2437/F2437M standards provide additional fastening compatibility across industrial sectors.

    ASTM A194/A194M Grade 2H Chemical Requirements

    Grade Description
    and
    UNS Designation    		 C Mn P SE Si
    ASTM A194/A194M 2H C 0.40 min 1.00 0.040 0.050 0.40
    • (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 2H Hardness Requirements

    Grade and Type Completed Nuts Sample Nut after Treatment
    Brinell Hardness Rockwell Hardness Brinell Hardness, min Rockwell Hardness B Scale, min
    C Scale B Scale
    ASTM A194/A194M Grade 2Hto 11/2 in. or M36, incl 248 to 327 24 to 35 ... 179 89
    ASTM A194/A194M Grade 2H over 11/2 in. or M36 212 to 327 35 max 95 min 147 79

    ASTM A194/A194M Grade 2H Proof Load Requirements (Inch Series)

    Nominal Size, in. Threads per Inch Stress Area in. 2 Proof Load, lbf A
    Grade 2H
    Heavy HexD HexE
    1/4 20 0.0316 4 770 4 300
    5/16 18 0.0524 7 860 7 070
    3/8 16 0.0774 11 620 10 460
    7/16 14 0.1063 15 940 14 350
    1/2 13 0.1419 21 280 19 160
    9/16 12 0.182 27 300 24 570
    5/8 11 0.226 33 900 30 510
    3/4 10 0.334 50 100 45 090
    7/8 9 0.462 69 300 62 370
    1 8 0.606 90 900 81 810
    11/8 8 0.790 118 500 106 700
    11/4 8 1.000 150 000 135 000
    13/8 8 1.233 185 000 166 500
    11/2 8 1.492 223 800 201 400
    • (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 2H Proof Load Requirements (Metric Series)

    Nominal Size, mm Threads Pitch Stress Area mm 2 Proof Load, kNA
    Grade 2H
    Heavy HexD HexE
    M6 1.0 20.1 20.8 18.7
    M8 1.25 36.6 37.9 34.0
    M10 1.50 58.0 60.0 53.9
    M12 1.75 84.3 87.3 78.4
    M14 2.0 115.0 119.0 107.0
    M16 2.0 157.0 162.5 146.0
    M20 2.5 245.0 253.6 227.8
    M22 2.5 303.0 313.6 281.8
    M24 3.0 353.0 365.4 328.3
    M27 3.0 459.0 475.1 426.9
    M30 3.5 561.0 580.6 521.7
    M36 4.0 817.0 845.6 759.8
    • (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 Grades & References

    Grade 2H is the workhorse heavy hex nut for refinery and petrochemical bolting. For sour-service applications, switch to Grade 2HM (NACE MR0175 hardness-controlled). For Cr-Mo alloy strength up to 1100°F, use Cr-Mo alloy nuts (companion to A193 B7). For stainless service, see Grade 8 (304), Grade 8M (316), or Grade 8T (321 Ti-stabilised). Dimensional standards: ASME B18.2.2 heavy hex. Full specification: ASTM A194 PDF · A194 hub.

    International Equivalents

    StandardRegionNotes
    ASTM A563-DHUSAQ&T carbon steel structural nut
    ASTM A194-2HMUSASour-service variant (NACE MR0175)
    BS 6105 Grade 5UKQ&T carbon steel hex nut
    DIN 267-7 Class 10GermanyMetric property class 10 nut
    ISO 898-2 Class 10ISOMetric mechanical property class 10
    JIS B 1181 Class 10JapanJapanese property class 10 hex nut
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