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    2. ASTM A193/A193M Grade B8 Class 1

    ASTM A193/A193M Grade B8 Class 1 Stud Bolts – UNS S30400

    Solution annealed 304 stainless steel stud bolts for general-purpose high-pressure and high-temperature bolting applications.

    ASTM A193/A193M Grade B8 Class 1 Stud Bolts are manufactured from UNS S30400 austenitic stainless steel and produced in the solution annealed condition, which relieves internal stresses and provides uniform mechanical properties throughout the fastener. These stud bolts conform to the ASTM A193 specification, which governs alloy and stainless steel bolting materials intended for use in high-temperature or high-pressure service, including flanged joints, pressure vessels, valves, and fittings. The Class 1 designation indicates that the bolts are solution annealed only and are not strain hardened, resulting in lower tensile strength compared to Class 2 but offering superior corrosion resistance and ductility. Grade B8 in UNS S30400 chemistry provides excellent resistance to a wide range of corrosive environments including atmospheric oxidation and many chemical media, making it one of the most widely used grades under the A193 standard across oil and gas, petrochemical, and power generation industries.

    ASTM A193/A193M Grade B8 Class 1 Chemical Composition - Austenitic Steels

    Grade Description and UNS Designatio Classes C Mn P S Si Cr Ni
    ASTM A193 Grade B8 304, S30400 1, 1A, 1D, 2 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0
    Product Analysis VariationB 0.01 0.04 0.010 0.005 0.05 0.20 0.15
    • (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 B8 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 B8 Class 1 All diameters carbide solution treated 75 30 30 50 223 HBW or 96 HRBC
    75 30 35 50 223 HBW or 96 HRBC
    over 3/4 to 1, incl carbide solution treated and strain hardened 115 80 15 35 321 HBW or 35 HRC
    over 1 to 11/4 ,incl 105 65 20 35 321 HBW or 35 HRC
    over 11/4 to 11/2 ,incl 100 50 28 45 321 HBW or 35 HRC
    over 2 to 21/2 incl 90 65 30 40 321 HBW or 35 HRC
    over 21/2 to 3 incl 80 55 30 40 321 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 B8 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 B8 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 B8 Class 1 Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8 Class 1 TB B8

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8 Class 1?
    ASTM A193 Grade B8 Class 1 is a bolting material covering 304 SS general-purpose austenitic (UNS S30400). 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 B8 Class 1?
    The UNS designation for ASTM A193 Grade B8 Class 1 is UNS S30400. This corresponds to 304 SS general-purpose austenitic. 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.
    When is ASTM A193 Grade B8 the right choice (Class 1)?
    Grade B8 (304 SS) is specified when general atmospheric corrosion resistance is needed at moderately elevated temperatures up to 538 °C (1000 °F). It is NOT recommended in chloride or sour-service environments — switch to B8M (316 SS with Mo) or B8C (347 Nb-stabilized) instead. Specific to ASTM A193 Grade B8 Class 1: Class 1 — solution treated.
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