• View PDF
    Standard
  •   +91-22-66157017
  •   info@torqbolt.com
    • Home
    2. ASTM A193/A193M Grade B8MLN Class 1D

    ASTM A193/A193M Grade B8MLN Class 1D Stud Bolts – UNS S31653

    Molybdenum-bearing, low carbon, nitrogen-alloyed 316LN stainless steel stud bolts in the Class 1D condition combining pitting resistance with controlled creep performance.

    ASTM A193/A193M Grade B8MLN Class 1D Stud Bolts are manufactured from UNS S31653 Type 316LN austenitic stainless steel and supplied in the solution annealed Class 1D condition per ASTM A193, incorporating grain size control requirements that enhance creep and stress rupture resistance at elevated service temperatures. This grade combines three alloying benefits — low carbon content for weld sensitization resistance, 2–3% molybdenum for superior pitting corrosion resistance in chloride environments, and controlled nitrogen for solid solution strengthening — with the additional advantage of a controlled grain size microstructure optimized for long-term elevated-temperature service. The result is a stud bolt that performs reliably in demanding high-temperature, corrosion-intensive environments such as offshore chemical reactors, high-temperature desalination heat exchangers, and refinery pressure vessels, where the combination of molybdenum-bearing corrosion resistance, weld compatibility, and creep resistance is simultaneously required to meet design code and safety requirements.

    ASTM A193/A193M Grade B8MLN Class 1D Chemical Composition - Austenitic Steels

    Grade Description and UNS Designatio Classes C Mn P S Si Cr Ni Mo N
    ASTM A193 Grade B8MLN S31653 1, 1A, 1D 0.030 2.00 0.045 0.030 1.00 16.0-18.0 10.0-13.0 2.00-3.00 0.10-0.16
    Product Analysis VariationB 0.005 0.04 0.010 0.005 0.05 0.20 0.15 0.10 0.01
    • (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 B8MLN 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 B8MLN Class 1D All diameters carbide solution treated 75 30 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 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 B8MLN 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 B8MLN 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 B8MLN Class 1D Bolting Components Marking - Austenitic Steels

    Grade Class Grade Symbol
    ASTM A193 Grade B8MLN Class 1D TB B98

    Related ASTM A193 Grades & ASME Companion Dimensions

    Frequently Asked Questions

    What is ASTM A193 Grade B8MLN Class 1D?
    ASTM A193 Grade B8MLN Class 1D is a bolting material covering 316LN low-carbon nitrogen-enhanced (UNS S31653). 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 B8MLN Class 1D?
    The UNS designation for ASTM A193 Grade B8MLN Class 1D is UNS S31653. This corresponds to 316LN low-carbon nitrogen-enhanced. 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 benefit of Grade B8MLN over Grade B8M (Class 1D)?
    B8MLN is 316LN — Low-carbon (C ≤ 0.030%) Nitrogen-enhanced 316. The low carbon prevents sensitization during welding or in-service exposure; nitrogen restores strength to match B8M (75 ksi UTS minimum). Used in welded chloride or sour service. Specific to ASTM A193 Grade B8MLN 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.