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    2. ASTM A193/A193M Grade B8R Class 1C

    ASTM A193/A193M Grade B8R Class 1C Stud Bolts – UNS S20910

    High-strength nitrogen-strengthened Nitronic 50 austenitic stainless steel stud bolts in the solution annealed Class 1C condition for demanding pressure bolting service.

    ASTM A193/A193M Grade B8R Class 1C Stud Bolts are produced from UNS S20910, a nitrogen-strengthened austenitic stainless steel commercially known as Nitronic 50 or XM-19, and are supplied in the solution annealed Class 1C condition which delivers mechanical properties significantly superior to standard 304 and 316 types in the annealed state due to the high nitrogen content serving as a primary strengthening mechanism. UNS S20910 contains chromium, nickel, molybdenum, niobium, vanadium, and elevated nitrogen, yielding approximately twice the yield strength of Type 316 in the annealed condition while maintaining excellent corrosion resistance that meets or exceeds that of 316 in many environments. These stud bolts are particularly noted for outstanding performance in seawater, mildly reducing acids, and chloride-containing solutions, as well as excellent toughness at cryogenic temperatures. Grade B8R Class 1C is specified for subsea equipment, marine hardware, cryogenic pressure vessels, and high-pressure flanged assemblies where the elevated annealed-condition strength eliminates the need for strain hardening while still meeting demanding mechanical requirements.

    ASTM A193/A193M Grade B8R Class 1C Chemical Composition - Austenitic Steels

    Grade Description and UNS Designatio Classes C Mn P S Si Cr Ni Mo CbF V N
    ASTM A193 Grade B8R S20910 1C, 1D 0.06 4.0-6.0 0.045 0.030 1.00 20.5-23.5 11.5-13.5 1.50-3.00 0.10-0.30 0.10-0.30 0.20-0.40
    Product Analysis VariationB 0.01 0.05 0.005 0.005 0.05 0.25 0.15 0.10 0.05 0.02 0.02
    • (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 B8R Class 1C 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 B8R Class 1C All diameters carbide solution treated 100 55 35 55 271 HBW or 28 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 B8R Class 1C 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 B8R Class 1C All diameters carbide solution treated 690 380 35 55 271 HBW or 28 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 B8R Class 1C Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8R Class 1C TB B9A or TB B8R

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8R Class 1C?
    ASTM A193 Grade B8R Class 1C is a bolting material covering Nitronic 50 (XM-19) high-N austenitic (UNS S20910). Class 1C — solution treated, higher-strength austenitic. 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 B8R Class 1C?
    The UNS designation for ASTM A193 Grade B8R Class 1C is UNS S20910. This corresponds to Nitronic 50 (XM-19) high-N austenitic. The UNS code is universal across ASTM, ASME (SA-193), PED 2014/68/EU and NORSOK material specifications. The 'Class 1C' designator denotes the heat treatment condition under ASTM A193 Table 3.
    What is the corrosion-resistance advantage of Grade B8R (Nitronic 50) (Class 1C)?
    Grade B8R is Nitronic 50 (XM-19, S20910) — a high-nitrogen austenitic stainless with PREN ≈ 35 vs PREN ≈ 24 for 316. It provides superior chloride pitting and crevice resistance and is widely used in seawater service, oilfield downhole tools and high-strength chemical bolting. Specific to ASTM A193 Grade B8R Class 1C: Class 1C — solution treated, higher-strength austenitic.
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