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    2. Grade N06686

    ASTM F468/F468M Grade N06686 686 Ni-Cr-Mo-W Fasteners

    High quality ASTM F468 Ni-Cr-Mo-W fasteners manufactured for industrial and corrosion resistant applications.

    ASTM F468/F468M Grade N06686 Ni-Cr-Mo-W fasteners are manufactured in accordance with ASTM specifications for nonferrous bolts, hex cap screws, socket head cap screws, and studs.

    Chemical Requirements

    UNS Designation Number Alloy General Name Al C, max Cr Cu A Fe, max Mn, max Ni A P, max Si, max Ti Co, max Mo S, max V W Cb
    Grade N06686 686 Ni-Cr-Mo-W . . . 0.010 max 19.0- 23.0 . . . 5.0 max 0.75 max balance 0.04 max 0.08 max 0.02- 0.25 15.0- 17.0 0.02 max . . . 3.0- 4.4 . . .
    • (A) Elements shown as balance shall be arithmetically computed by deducting the sum of the other named elements from 100.
    • (B) Cobalt is to be counted as nickel.
    • (C) Alloy 625 material shall be refined using the electroslag remelting process (ESR), or the vacuum arc remelting process (VAR).

    Mechanical Requirements

    Alloy Mechanical Property Marking Nominal Thread Diameter, in. Hardness A Full-Size Tests B Machined Specimen Tests
    Tensile Strength, ksi Yield Strength, min, ksi C Tensile Strength, min, ksi Yield Strength min, ksi C Elongation in 4D, min, % D
    Alloy Ni 686 Grade 1 F468BN All 21-45 HRC 120-165 85 120 85 20
    • (A) Where both tension and hardness tests are performed, the tension tests shall take precedence for acceptance purposes. For aluminum and titanium alloys, hardness tests are for information only. See 6.5.
    • (B) The yield and tensile strength values for full-size products shall be computed by dividing the yield and maximum tensile load by the stress area for the product diameter and thread pitch as given in table on tensile stress areas.
    • (C) Yield strength is the stress at which an offset of 0.2 % gage length occurs.
    • (D) Elongation is determined using a gage length of 4 diameters of test specimen in accordance with Test Methods E8/E8M.
    • (E) "HF" denotes a hot-formed product.
    • (F) Aluminum alloy temper designations are in accordance with ANSI H35.1.
    • (G) Full-size test mechanical properties apply to fasteners with a maximum diameter of 76 mm. Mechanical properties of larger sections shall be negotiated between the material manufacturer and the fastener producer.
    • (H) Ti 5 Class A requires wedge tensile testing in accordance with Ti 5 Class B requires wedge tensile testing in accordance.

    ASTM F468/F468M Grade N06686 686 Ni-Cr-Mo-W Tensile Stress Areas and Threads(Inch)

    Nominal Size, in. Coarse Threads-UNC Fine Threads-UNF 8 Thread Series-8UN
    Threads/ in. Stress Area A , in. 2 Threads/ in. Stress Area A , in. 2 Threads/ in. Stress Area A , in. 2
    1 / 4 20 0.0318 28 0.0364 . . . . . .
    5 / 16 18 0.0524 24 0.0580 . . . . . .
    3 / 18 16 0.0775 24 0.0878 . . . . . .
    7 / 16 14 0.1063 20 0.1187 . . . . . .
    1 / 2 13 0.1419 20 0.1599 . . . . . .
    9 / 16 12 0.1820 18 0.2030 . . . . . .
    5 / 8 11 0.2260 18 0.2560 . . . . . .
    3 / 4 10 0.3340 16 0.3730 . . . . . .
    7 / 8 9 0.4620 14 0.5090 . . . . . .
    1 8 0.6060 12 0.6630 . . . . . .
    1 1 / 8 7 0.7630 12 0.8560 8 0.790
    1 1 / 4 7 0.9690 12 1.0730 8 1.000
    1 3 / 8 6 1.1550 12 1.3150 8 1.233
    1 1 / 2 6 1.4050 12 1.5810 8 1.492
    • (A) Tensile stress areas are computed using the following formula:
    • A s = 0.7854 [ D - 0.9743/n ]
    • where:
    • As = tensile stress area, in.2,
    • D = nominal size (basic major diameter), in., and
    • n = number of threads per inch.

    ASTM F468/F468M Grade N06686 686 Ni-Cr-Mo-W Tensile Stress Areas (Metric)

    Nominal Product Diameter and Thread Pitch Stress Area, A mm 2 Nominal Product Diameter and Thread Pitch Stress Area, A mm 2
    M6 × 1 20.1 M16 × 2 157
    M8 × 1.25 36.6 M20 × 2.5 245
    M10 × 1.5 58.0 M24 × 3 353
    M12 × 1.75 84.3 M30 × 3.5 561
    M14 × 2 115 M36 × 4 817
    • (A) Tensile stress areas are computed using the following formula:
    • A s = 0.7854 (D − 0.9382 P) 2
    • where:
    • As = stress area, mm2,
    • D  = nominal thread diameter, mm, and
    • P  = thread pitch, mm.

    Frequently Asked Questions

    What is Alloy 686 (N06686)?

    Alloy 686 is a Ni-Cr-Mo-W alloy (~58 Ni, 20.5 Cr, 16.3 Mo, 3.9 W) - effectively an enhanced C-276 with more chromium for improved oxidizing-acid resistance while retaining tungsten for localized-corrosion protection. Per ASTM F468 for the most severe chemical-process bolting and FGD scrubber applications.

    How does Alloy 686 compare to Hastelloy C-276?

    Alloy 686 has ~5% more Cr (20.5 vs 15.5) for better oxidizing-acid + hot-chloride resistance, with the same Mo + W giving it equivalent reducing-acid + pitting performance. Use 686 in mixed-chemistry service that defeats C-276; both are F468-covered.

    Is Alloy 686 NACE MR0175 acceptable?

    Yes. N06686 is listed in NACE MR0175 / ISO 15156 for sour-service bolting subject to standard hardness and condition requirements.

    Where is Alloy 686 used in fastener applications?

    FGD scrubber bolting, hazardous-waste incinerator hardware, chlorine + chlorine-dioxide bleach plant fasteners, and high-temperature concentrated-acid process equipment. Pairs with Alloy 686 nuts per ASTM F467 for matched-alloy assemblies.

    References & Standards

    • ASTM F468 / F468M - Standard Specification for Nonferrous Bolts, Hex Cap Screws, and Studs for General Use
    • ASTM F467 / F467M - Companion specification for Nonferrous Nuts (mate with F468 for matched-alloy assemblies)
    • ASTM F436 / F436M - Hardened steel washers (ferrous washer companion when nonferrous washers are not specified)
    • NACE MR0175 / ISO 15156 - Sour-service hardness limits for petroleum and natural gas industries
    • ASME B18.2.1 / B18.2.3 series / B18.3 / B18.6.7M / B18.31 / B16.5 - Dimensional standards referenced by F468
    • DIN 912 / 933 / 931 - Metric hex socket head and hex head cap screw dimensional standards
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