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    2. ASTM A193/A193M Grade B8PA Class 1A

    ASTM A193/A193M Grade B8PA Class 1A Stud Bolts – UNS S30500

    Strain hardened high-nickel 305 stainless steel stud bolts combining non-magnetic stability with improved mechanical strength for specialty applications.

    ASTM A193/A193M Grade B8PA Class 1A Stud Bolts are produced from UNS S30500 austenitic stainless steel, a high-nickel variant of the 18-8 family specifically selected for its inherently low work hardening rate, and are strain hardened to achieve the elevated mechanical requirements of Class 1A as defined in ASTM A193, with proof testing performed on the finished fastener. Despite undergoing cold working, UNS S30500's stable austenitic microstructure — maintained by its elevated nickel content — ensures that the bolts retain exceptionally low magnetic permeability, an important characteristic in applications where electromagnetic neutrality must be preserved. Grade B8PA Class 1A stud bolts are selected for specialized uses in scientific instrumentation, magnetic resonance equipment environments, sensitive electronic systems, and certain aerospace and defense applications where conventional stainless grades may develop unacceptable magnetic properties under the cold work applied during strain hardening, yet the application still demands the enhanced strength of a Class 1A fastener.

    ASTM A193/A193M Grade B8PA Class 1A Chemical Composition - Austenitic Steels

    Grade Description and UNS Designatio Classes C Mn P S Si Cr Ni
    ASTM A193 Grade B8PA S30500 1, 1A, 1D, 2 0.12 2.00 0.045 0.030 1.00 17.0-19.0 11.0-13.0
    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 B8PA Class 1A 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 B8PA Class 1A All diameters carbide solution treated in the finished condition 75 30 30 50 192 HBW or 90 HRB
    • (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 B8PA Class 1A 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 B8PA Class 1A All diameters carbide solution treated in the finished condition 515 205 30 50 192 HBW or 90 HRB
    • (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 B8PA Class 1A Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8PA Class 1A TB B8H or TB B8PA

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8PA Class 1A?
    ASTM A193 Grade B8PA Class 1A is a bolting material covering 305 SS for cold-formed deep-draw (UNS S30500). Class 1A — solution treated in finished condition for corrosion resistance. 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 B8PA Class 1A?
    The UNS designation for ASTM A193 Grade B8PA Class 1A is UNS S30500. This corresponds to 305 SS for cold-formed deep-draw. The UNS code is universal across ASTM, ASME (SA-193), PED 2014/68/EU and NORSOK material specifications. The 'Class 1A' designator denotes the heat treatment condition under ASTM A193 Table 3.
    What is the use case for Grade B8PA (305 SS) (Class 1A)?
    Grade B8PA is 305 SS — a higher-Ni variant of 304 (10.5–13% Ni vs 8–10.5% for 304) with very low work-hardening rate. Used where bolts must be cold-formed (e.g. deep-headed or rolled-thread) without sensitivity to strain-induced martensite. Specific to ASTM A193 Grade B8PA Class 1A: Class 1A — solution treated in finished condition for corrosion resistance.
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