• View PDF
    Standard
  •   +91-22-66157017
  •   info@torqbolt.com
    • Home
    2. ASTM A193/A193M Grade B8M Class 1

    ASTM A193/A193M Grade B8M Class 1 Stud Bolts – UNS S31600

    Molybdenum-bearing 316 stainless steel stud bolts offering enhanced corrosion resistance in chloride-rich and chemical processing environments.

    ASTM A193/A193M Grade B8M Class 1 Stud Bolts are manufactured from UNS S31600 austenitic stainless steel, commonly known as Type 316, which incorporates 2–3% molybdenum to significantly improve resistance to pitting and crevice corrosion in chloride-containing environments compared to standard 304 stainless steel. Supplied in the solution annealed condition, these stud bolts offer excellent ductility, weldability, and uniform mechanical properties, making them suitable for use in flanged connections, pressure vessels, and heat exchangers across a broad range of industries. The Class 1 designation confirms that these bolts are not strain hardened and meet the base tensile and yield strength requirements specified in ASTM A193. Grade B8M is widely specified in offshore oil and gas, marine, pharmaceutical, pulp and paper, and chemical processing industries where exposure to aggressive corrosive media, seawater, and acidic conditions demands a more robust stainless alloy than standard Grade B8.

    ASTM A193/A193M Grade B8M Class 1 Chemical Composition - Austenitic Steels

    Grade Description and UNS Designatio Classes C Mn P S Si Cr Ni Mo
    ASTM A193 Grade B8M 316, S31600 1, 1A, 1D, 2 0.08 2.00 0.045 0.030 1.00 16.0-18.0 10.0-14.0 2.00-3.00
    Product Analysis VariationB 0.01 0.04 0.010 0.005 0.05 0.20 0.15 0.10
    • (A) Values are maximums unless a range or a minimum is indicated. Where ellipses appear in this table, there is no requirement and the element need not be determined or reported. The intentional addition of Bi, Se, Te, and Pb is not permitted.
    • (B) Product Analysis-Individual determinations sometimes vary from the specified limits as shown in the tables. The several determinations of any individual element in a heat may not vary both above and below the specified range. Product variation limits are over for maximums, over or under for ranges, and under for minimums, unless otherwise indicated.
    • (C) Typical steel compositions used for this grade include 4140, 4142, 4145, 4140H, 4142H, and 4145H.
    • (D) For bar sizes over 31/2 in. [90 mm], inclusive, the carbon content may be 0.50% max. For the B7M grade, a minimum carbon of 0.28% is permitted, provided that the required tensile properties are met in the section sizes involved, the use of AISI 4130 or 4130H is allowed.
    • (E) Total of soluble and insoluble.
    • (F) Columbium and Niobium are alternate names for element 41 in the Periodic Table of the Elements.

    ASTM A193/A193M Grade B8M Class 1 Mechanical Requirements - Austenitic Steels (Inch)

    Grade Diameter,
    in.     		Heat TreatmentB Tensile Strength,
    min, ksi     		Yield Strength, min,
    0.2 % offset, ks     		Elongation in 4 D,min Reduction of Area, min Hardness,
    max
    ASTM A193 Grade B8M Class 1 All diameters carbide solution treated 75 30 30 50 223 HBW or 96 HRBC
    over 3/4 to 1 incl carbide solution treated and strain hardened 100 80 20 45 321 HBW or 35 HRC
    Over 1 to 11/4 ,incl 95 65 25 45 321 HBW or 35 HRC
    over 11/4 to 11/2 ,incl 90 50 30 45 321 HBW or 35 HRC
    • (A) To meet the tensile requirements, the Brinell hardness shall be over 200 HBW (93 HRB).
    • (B) Class 1 is solution treated. Class 1A is solution treated in the finished condition for corrosion resistance; heat treatment is critical due to physical property requirement. Class 2 is solution treated and strain hardened. Austenitic steels in the strain-hardened condition may not show uniform properties throughout the section particularly in sizes over 3/4 in. in diameter.
    • (C) For sizes3/4 in. in diameter and smaller, a maximum hardness of 241 HBW (100 HRB) is permitted.
    • (D) For diameters 11/2 and over, center (core) properties may be lower than indicated by test reports which are based on values determined at1/2 radius.

    ASTM A193/A193M Grade B8M Class 1 Mechanical Requirements - Austenitic Steels (Metric)

    Grade Class ,
    mm     		Diameter Heat TreatmentB Tensile Strength,
    min,MPa     		Yield Strength, min,
    0.2 % offset, MPa     		Elongation in 4 D,min % Reduction of Area, min % Hardness,
    max
    ASTM A193 Grade B8M Class 1 All diameters carbide solution treated 515 205 30 50 223 HBW or 96 HRBC
    • (A) To meet the tensile requirements, the Brinell hardness shall be over 200 HBW (93 HRB).
    • (B) Class 1 is solution treated. Class 1A is solution treated in the finished condition for corrosion resistance; heat treatment is critical due to physical property requirement. Class 2 is solution treated and strain hardened. Austenitic steels in the strain-hardened condition may not show uniform properties throughout the section particularly in sizes over M20 mm in diameter.
    • (C) For sizes M20 mm in diameter and smaller, a maximum hardness of 241 HBW (100 HRB) is permitted.
    • (D) For diameters M38 and over, center (core) properties may be lower than indicated by test reports which are based on values determined at1/2 radius.

    ASTM A193/A193M Grade B8M Class 1 Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8M Class 1 TB B8M

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8M Class 1?
    ASTM A193 Grade B8M Class 1 is a bolting material covering 316 SS Mo-bearing for chloride/sour (UNS S31600). Class 1 — solution treated. Used in high-temperature, high-pressure flange, pressure-vessel and heat-exchanger bolting service per ASTM A193/A193M.
    What is the UNS designation for ASTM A193 Grade B8M Class 1?
    The UNS designation for ASTM A193 Grade B8M Class 1 is UNS S31600. This corresponds to 316 SS Mo-bearing for chloride/sour. The UNS code is universal across ASTM, ASME (SA-193), PED 2014/68/EU and NORSOK material specifications. The 'Class 1' designator denotes the heat treatment condition under ASTM A193 Table 3.
    Why is ASTM A193 Grade B8M preferred over B8 (Class 1)?
    Grade B8M (316 SS with 2–3% Mo) provides significantly improved pitting and crevice corrosion resistance vs B8 (304 SS) in chloride, sour-service and marine environments. PREN ≈ 24 for 316 vs ≈ 19 for 304. Specific to ASTM A193 Grade B8M Class 1: Class 1 — solution treated.
    Specifications
    Surface Treatments
    Certifications
    About Us
    Questions? Contact us.
    Showcase of our Microsites.
    Satisfaction Survey

    survey

    TUVRheinland CRETIFIED

    © TorqBolt P(Ltd) · Built with in INDIA.