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    2. ASTM A320/A320M Grade B8C

    ASTM A320 / ASME SA-320 Grade B8C Stud Bolts (UNS S34700)

    AISI 347 niobium-stabilized austenitic stainless steel · Solution-treated (Class 1) or strain-hardened (Class 2)

    ASTM A320 Grade B8C is an austenitic stainless steel bolting grade specified per ASTM A320/A320M-22 for low-temperature service. Assigned UNS number S34700. Manufactured from AISI 347 niobium-stabilized 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 B8C resists intergranular corrosion in elevated-temperature service through niobium stabilization. Grade B8C is intended for stud bolts and hex bolts in pressure vessels, valves, flanges, and fittings exposed to corrosive or low-temperature environments. Grade B8C is equivalent to ASME SA-320 Grade B8C in the ASME Boiler and Pressure Vessel Code Section II Part A.

    ASTM A320 Grade B8C properties

    ASTM A320 Grade B8C chemical composition

    Grade Symbol UNS Designation C, max Mn, max P, max S, max Si, max Ni Cr Nb E + Ta
    ASTM A320 B8C S34700(347) Range,% 0.08 2.00 0.045
    0.030    		 1.00 9.0- 12.0 17.0- 19.0 10 × C content, min -1.10 max
    Product Variation, % Over or Under 0.01 over 0.04 over 0.010 over 0.005 over 0.05 over 0.15 0.20 0.05 under

    ASTM A320 Grade B8C mechanical properties

    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 B8C Class 1 All diameters carbide solution treated 75 [515] 30 [205] 30 50 223 HBWDor  96 HRB
    ASTM A320 B8C 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 B8C?

    For low-temperature service consistency, ASTM A320 Grade B8C 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 B8C + 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 B8C

    TorqBolt’s ASTM A320 Grade B8C 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 B8C 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

    ASTM A320 Grade B8C: related product searches

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  • ASME SA 320 Grade B8C Class 2 Bolts
  • SA 320 Gr B8C Cl 2 Screws
  • A320 B8C Class 2 Heavy Hex Screws
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  • ASME SA 320 Gr B8C Class 2 Studs
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  • ASME SA 320 Grade B8C Class 2 Bolting
  • ASTM A320 B8C Class 2 Square Bolts
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