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    2. Grade 8 Nuts

    ASTM A194 Grade 8 Heavy Hex Nuts — UNS S30400

    Stainless steel heavy hex nuts with excellent corrosion resistance and mechanical strength.

    ASTM A194/A194M Grade 8 Nuts are manufactured from stainless steel materials and provide outstanding corrosion resistance for marine, chemical, and industrial applications. These heavy hex nuts are widely used in piping systems, offshore projects, and food processing equipment. Grade 8 nuts are commonly paired with ASTM A193/A193M stainless steel stud bolts for corrosion-resistant bolting assemblies. ASTM A320/A320M low-temperature bolting standards are also applicable in cryogenic and chilled service environments, while ASTM A563M and ASTM F2437/F2437M specifications support structural and engineered fastening requirements.

    ASTM A194/A194M Grade 8 Chemical Requirements

    Grade Description
    and
    UNS Designation    		 C Mn P SE Si Cr Ni
    ASTM A194/A194M Grade 8 (304) S30400 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
    • (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 8 Hardness Requirements

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

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

    Nominal Size, in. Threads per Inch Stress Area in. 2 Proof Load, lbf A
    Grade 8
    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 8 Proof Load Requirements (Metric Series)

    Nominal Size, mm Threads Pitch Stress Area mm 2 Proof Load, kNA
    Grade 8
    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 Grades & References

    Grade 8 is solution-treated Type 304 austenitic stainless (UNS S30400), the most widely used stainless nut for non-oxidizing chemical service paired with A193 B8 studs. For Class 1A finished-condition heat treatment, see Grade 8A. For molybdenum-bearing chloride-pitting resistance, use Grade 8M (316). For titanium-stabilised intergranular-corrosion resistance, see Grade 8T (321) or Grade 8C (347 Nb-stabilised). Dimensional standards: ASME B18.2.2 heavy hex · ISO 4032 metric. Reference: ASTM A194 PDF · A194 hub.

    International Equivalents

    StandardRegionNotes
    ASTM F593 Group 1USA304 stainless fastener (general)
    ASTM A194-8AUSAClass 1A finished condition variant
    BS EN 10088-3 1.4301EUAustenitic 304 stainless
    DIN X5CrNi18-10GermanyMaterial number 1.4301 (304)
    ISO 3506-2 A2-70ISOClass A2 stainless nut property
    JIS SUS304JapanType 304 austenitic stainless

    Frequently Asked Questions

    What is ASTM A194 Grade 8?

    ASTM A194 Grade 8 is a solution-treated Type 304 austenitic stainless steel nut (UNS S30400), used in corrosive-service bolting with carbon steel studs in non-oxidizing chemical environments. Solution-treated condition provides resistance to intergranular corrosion.

    What is the difference between Grade 8 and Grade 8A?

    ASTM A194 Grade 8 and Grade 8A both use Type 304 stainless (UNS S30400). Grade 8 is solution-treated; Grade 8A is solution-treated in the finished condition (Class 1A), providing slightly improved corrosion resistance for the finished thread.

    Is ASTM A194 Grade 8 nut compatible with ASTM A193 Grade B8?

    Yes. ASTM A194 Grade 8 nuts (UNS S30400) are designed to match ASTM A193 Grade B8 stud bolts (also UNS S30400). Both grades use the same Type 304 austenitic stainless steel and are commonly paired in pressure-vessel and flange bolting service.

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