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    2. ASTM A193/A193M Grade B8M3 Class 2C

    ASTM A193/A193M Grade B8M3 Class 2C Stud Bolts – UNS S31600

    Maximum strain hardened UNS S31600 stainless steel stud bolts meeting Class 2C highest yield strength requirements for the most demanding pressure bolting applications.

    ASTM A193/A193M Grade B8M3 Class 2C Stud Bolts are produced from UNS S31600 Type 316 molybdenum-bearing austenitic stainless steel and strain hardened to achieve the highest mechanical property levels within the Class 2 family of ASTM A193, designated Class 2C, which specifies minimum yield strength requirements significantly above those of Class 2 and Class 2B for equivalent bolt diameters. This maximum level of cold work transforms the relatively soft austenitic stainless steel into a high-strength fastener material capable of bearing very high clamping loads while retaining the essential corrosion resistance properties of 316-type stainless steel — specifically the superior pitting and crevice corrosion resistance attributable to its 2–3% molybdenum content. Grade B8M3 Class 2C stud bolts represent the highest-strength standard stainless steel stud bolts available under the A193 specification and are specified for the most pressure-intensive, mechanically demanding bolted joint applications in advanced chemical processing, high-pressure testing equipment, and critical safety applications where both maximum strength and corrosion resistance cannot be compromised.

    ASTM A193/A193M Grade B8M3 Class 2C 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 B8M3 Class 2C 2 and under carbide solution treated and strain hardened 85 65 30 60 321 HBW or 35 HRC
    over 2 85 60 30 60 321 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 B8M3 Class 2C 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 B8M3 Class 2C M48 and under carbide solution treated and strain hardened 585 450 30 60 321 HBW or 35 HRC
    over M48 585 415 30 60 321 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 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 B8M3 Class 2C Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8M3 Class 2C TB B9H or TB B8M3

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8M3 Class 2C?
    ASTM A193 Grade B8M3 Class 2C is a bolting material covering 316 SS strain-hardened Class 2C (UNS S31600). Class 2C — strain hardened modified. 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 B8M3 Class 2C?
    The UNS designation for ASTM A193 Grade B8M3 Class 2C is UNS S31600. This corresponds to 316 SS strain-hardened Class 2C. The UNS code is universal across ASTM, ASME (SA-193), PED 2014/68/EU and NORSOK material specifications. The 'Class 2C' designator denotes the heat treatment condition under ASTM A193 Table 3.
    What is the difference between B8M Class 2 and Class 2C (Class 2C)?
    B8M Class 2C is a strain-hardened 316 stud-bolt class with a UTS minimum of 100 ksi (same as Class 2) but with a hardness modification. Used for high-strength 316 bolting in specific industrial sub-applications. Specific to ASTM A193 Grade B8M3 Class 2C: Class 2C — strain hardened modified.
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