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    2. ASTM A193/A193M Grade B8R Class 1D

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

    Nitronic 50 nitrogen-strengthened austenitic stainless steel stud bolts in the Class 1D condition with grain size control for high-strength creep-resistant pressure bolting.

    ASTM A193/A193M Grade B8R Class 1D Stud Bolts are produced from UNS S20910 Nitronic 50 austenitic stainless steel and supplied in the solution annealed Class 1D condition under ASTM A193, which requires grain size control — typically ASTM grain size 7 or coarser — to optimize resistance to creep and stress rupture under sustained elevated-temperature loading. Nitronic 50 already delivers approximately twice the yield strength of Type 304 in the annealed condition through its high nitrogen content, and the coarse grain size requirement of Class 1D further enhances long-term elevated-temperature mechanical stability, making Grade B8R Class 1D a particularly capable fastener for high-temperature, high-pressure service. Combined with superior corrosion resistance that meets or exceeds Type 316 in many environments, excellent cryogenic toughness, and the controlled microstructure of Class 1D, these stud bolts are suitable for the most demanding thermal and mechanical service conditions encountered in advanced power generation, aerospace ground support systems, and high-performance chemical processing equipment.

    ASTM A193/A193M Grade B8R Class 1D 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 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 B8R Class 1D 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 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 B8R Class 1D 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 1D Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8R Class 1D TB B101

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8R Class 1D?
    ASTM A193 Grade B8R Class 1D is a bolting material covering Nitronic 50 (XM-19) high-N austenitic (UNS S20910). 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 B8R Class 1D?
    The UNS designation for ASTM A193 Grade B8R Class 1D 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 1D' designator denotes the heat treatment condition under ASTM A193 Table 3.
    What is the corrosion-resistance advantage of Grade B8R (Nitronic 50) (Class 1D)?
    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 1D: Class 1D — Class 1 base properties for lower-temperature service.
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