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.