ASTM A193 Grade B8MLCuN Class 2 Specification

ASTM A193 Grade B8MLCuN Class 2 Specification for high tensile bolts, screws, stud bolts, anchor bolts, threaded rods and other threaded fasteners, made from UNS S31254 / Alloy 254SMO stainless steel.

ASTM A193 Grade B8MLCuN Class 2 is a standard material specification for corrosion resistant & high strength Alloy 254 / UNS S31254 fasteners such as bolts, screws, studs, threaded rods and other externally threaded parts, for use in high tensile, high temperature and special purpose applications such as pressure piping & pressure vessels bolting. Grade B8MLCuN Class 2 is strain hardened and carbide solution treated 6% moly stainless steel having a minimum tensile requirement of 90 ksi, yield 50 ksi and maximum hardness limit of 321 HBW or 35 HRC. This specification covers requirements for chemical composition, mechanical properties, hardness, heat-treatment and recommended nuts-washers for Grade B8MLCuN Class 2 Fasteners.

Chemical Composition

Element Austenitic Stainless Steel
UNS S31254 / Alloy 254SMO / 1.4547
CompositionA, %
Carbon 0.02 max
Manganese 1.00
Phosphorus 0.030 max
Sulfur 0.010 max
Silicon 0.80 max
Chromium 19.50 - 20.50
Nickel 17.50 - 18.50
Molybdenum 6.00 - 6.50
Nitrogen 0.18 - 0.22
Copper 0.50 - 1.00

A: The intentional addition of Bi, Se, Te, and Pb is not permitted.

Mechanical Properties

Tensile Class Diameter, Inch Tensile Strength,
min, ksi		 Yield Strength,
min, 0.2% offset,
ksi		 Elongation
in 4D,
min, %		 Reduction
of Area,
min, %		 Hardness,
max


Class 2A		 3/4 and under 110 95 15 45

321 HBW or 35 HRC
over 3/4 to 1 inclusive 100 80 20 45
over 1 to 1-1/4 inclusive 95 65 25 45
over 1-1/4 to 1-1/2 inclusive 90 50 30 45

Heat Treatment: Carbide Solution Treated and Strain Hardened
A: For diameters 11⁄2 and over, center (core) properties may be lower than indicated by test reports which are based on values determined at 1⁄2 radius.

Recommended Nuts & Washers

Nut Specification Washer Specification
ASTM A194 Grade 8MLCuN ASTM A240 UNS S31254

Fasteners

Commonly Produced B8MLCuN Fasteners
Hex Bolts Heavy Hex Bolts Stud Bolts Threaded Rods Anchor Bolts
Eye Bolts Socket Head Cap Screws Countersunk Screws U Bolts Square Head Bolts