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    2. ASTM A193/A193M Grade B8P Class 1

    ASTM A193/A193M Grade B8P Class 1 Stud Bolts – UNS S30500

    High-nickel UNS S30500 stainless steel stud bolts with minimal work hardening tendency, suited for precision and specialty bolting requirements.

    ASTM A193/A193M Grade B8P Class 1 Stud Bolts are produced from UNS S30500 austenitic stainless steel, a higher-nickel variant of the 300 series that exhibits a very low rate of work hardening during cold forming operations. With a nickel content typically ranging from 10.5% to 13%, UNS S30500 maintains a highly stable austenitic microstructure that resists transformation to martensite under deformation, making it particularly valued in applications requiring consistent non-magnetic properties throughout service. Supplied in the solution annealed Class 1 condition, these stud bolts meet the mechanical and chemical requirements of ASTM A193 for use in pressure vessels, flanges, and process piping systems. Grade B8P is less commonly specified than B8 or B8M but is selected in niche applications where magnetic permeability must be minimized, such as in instrumentation, electronics, or magnetically sensitive equipment environments, while still providing the general corrosion resistance characteristic of the 18-8 stainless steel family.

    ASTM A193/A193M Grade B8P Class 1 Chemical Composition - Austenitic Steels

    Grade Description and UNS Designatio Classes C Mn P S Si Cr Ni
    ASTM A193 Grade B8P 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 B8P 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 B8P 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 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
    • (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 B8P 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 B8P 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 B8P Class 1 Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8P Class 1 TB B8P

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8P Class 1?
    ASTM A193 Grade B8P Class 1 is a bolting material covering 305 SS for cold-formed deep-draw (UNS S30500). 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 B8P Class 1?
    The UNS designation for ASTM A193 Grade B8P Class 1 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 1' designator denotes the heat treatment condition under ASTM A193 Table 3.
    What is the use case for Grade B8P (305 SS) (Class 1)?
    Grade B8P 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 B8P Class 1: Class 1 — solution treated.
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