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    ASTM A320 / ASME SA-320 Grade B8F Stud Bolts (UNS S30300)

    AISI 303 free-machining austenitic stainless steel · Solution-treated (Class 1) or strain-hardened (Class 2)

    ASTM A320 Grade B8F is an austenitic stainless steel bolting grade specified per ASTM A320/A320M-22 for low-temperature service. Assigned UNS number S30300. Manufactured from AISI 303 free-machining austenitic stainless steel. The grade is supplied in Class 1 (solution-treated) or Class 2 (strain-hardened) condition, with Class 2 offering higher tensile strength through controlled cold work. Grade B8F is the free-machining variant of 304 stainless, used where rapid machining is required. Grade B8F is intended for stud bolts and hex bolts in pressure vessels, valves, flanges, and fittings exposed to corrosive or low-temperature environments. Grade B8F is equivalent to ASME SA-320 Grade B8F in the ASME Boiler and Pressure Vessel Code Section II Part A.

    ASTM A320 Grade B8F properties

    ASTM A320 Grade B8F chemical composition

    Austenitic Steels

    Grade Symbol UNS Designation C, max Mn, max P, max S, max Si, max Ni Cr Se
    ASTM A320 B8F S30300(303) Range,% 0.15 2.00 0.20 00.15, min 1.00 8.0 - 10.0 17.0- 19.0 0.15-0.35
    Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.20 0.05 over 0.10 0.20 ...

    ASTM A320 Grade B8F mechanical properties

    Austenitic Steels

    Grade and Class Diameter, in. [mm] Heat Treatment 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 B8F : Class 1 All diameters carbide solution treated 75 [515] 30 [205] 30 50 223 HBWDor 96 HRB
    ASTM A320 B8F : Class 2 3/4 [20] and under carbide solution treated and strain hardened 125 [860] 100 [690] 12 35 321 HBW or 35 HRC
    over 3/4 to 1 [20 to 25], incl 115 [795] 80 [550] 15 30 321 HBW or 35 HRC
    over 1 to 11/4 [25 to 32], incl 105 [725] 65 [450] 20 35 321 HBW or 35 HRC
    over 11/4 to 11/2 [32 to 40], inclA 100 [690] 50 [345] 28 45 321 HBW or 35 HRC

    What nuts and washers are specified for ASTM A320 Grade B8F?

    For low-temperature service consistency, ASTM A320 Grade B8F stud bolts are paired with ASTM A194 Grade 8 series stainless heavy hex nuts and ASTM F436 hardened steel washers. TorqBolt supplies kit-matched A320 B8F + A194 + F436 sets with a single EN 10204 3.1 or 3.2 certificate covering all three components.

    NORSOK M-650 qualification & EN 10204 3.1 / 3.2 certificates for A320 Grade B8F

    TorqBolt’s ASTM A320 Grade B8F stud bolt production route is qualified to NORSOK M-650 for North Sea oil & gas offshore service. Each manufacturing record links heat number, melt analysis, heat-treatment batch, mechanical test, dimensional inspection, surface treatment, and dispatch. Standard certification is EN 10204 Type 3.1 (manufacturer’s test report); Type 3.2 third-party witnessed by Lloyd’s Register, DNV, BV, ABS, or TUV is available on request. The qualification packet covers ASME SA-320 B8F equivalence, NACE MR0175 / ISO 15156-2 sour-service compliance (where applicable), and PED 2014/68/EC for European pressure-equipment buyers.

    Related ASTM A320 grades & companion specifications

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