ASTM A193 Grade B8MN Class 2 Specification for high tensile bolts, screws, stud bolts, anchor bolts, threaded rods and other externally threaded fasteners, made from 316N stainless steel.

ASTM A193 Grade B8MN Class 2 is a standard material specification for high strength 316N stainless steel 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 B8MN is a strain hardened & carbide solution 316N stainless steel having a minimum tensile requirement of 90 ksi, yield 30 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 B8MN Class 2 Fasteners.

Chemical Composition

Element	Nitrogen Enhanced Stainless Steel
	AISI 316N / UNS S31651
	CompositionA, %
Carbon	0.08 max
Manganese	2.00
Phosphorus	0.045 max
Sulfur	0.030 max
Silicon	1.00 max
Chromium	16.00 - 18.00
Nickel	10.00 - 13.00
Molybdenum	2.00 - 3.00
Nitrogen	0.10 - 0.16

^AThe 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.