• View PDF
    Standard
  •   +91-22-66157017
  •   info@torqbolt.com
    • Home
    2. ASTM A193/A193M Grade B8 Class 1D

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

    Solution annealed UNS S30400 stainless steel stud bolts meeting Class 1D requirements including grain size control for elevated-temperature pressure bolting service.

    ASTM A193/A193M Grade B8 Class 1D Stud Bolts are manufactured from UNS S30400 Type 304 austenitic stainless steel and supplied in the solution annealed condition meeting the Class 1D designation, which under ASTM A193 imposes specific requirements including austenite grain size control — typically ASTM grain size number 7 or coarser — that are established to optimize creep and stress rupture properties at elevated service temperatures. Unlike standard Class 1 material that focuses primarily on room-temperature mechanical properties and corrosion resistance, the Class 1D qualification is specifically tailored for applications where the stud bolts must maintain adequate clamping force and resist time-dependent deformation (creep and relaxation) during sustained service at high temperatures. These stud bolts retain all the general corrosion resistance, weldability, and ductility characteristic of the 304 stainless steel family, making Grade B8 Class 1D an important specification for high-temperature flanges, steam piping, boiler components, and petrochemical reactors operating at elevated temperatures where long-term mechanical stability and controlled microstructure are critical.

    ASTM A193/A193M Grade B8 Class 1D 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 1D 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 1D All diameters carbide solution treated 75 30 30 50 223 HBW or 96 HRBC
    75 30 35 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 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 1D 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 1D 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 1D Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8 Class 1D TB B94

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8 Class 1D?
    ASTM A193 Grade B8 Class 1D is a bolting material covering 304 SS general-purpose austenitic (UNS S30400). Class 1D — Class 1 base properties for lower-temperature service. 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 1D?
    The UNS designation for ASTM A193 Grade B8 Class 1D 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 1D' designator denotes the heat treatment condition under ASTM A193 Table 3.
    When is ASTM A193 Grade B8 the right choice (Class 1D)?
    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 1D: Class 1D — Class 1 base properties for lower-temperature service.
    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.