ASTM A193 Grade B8MN Class 1B 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 1B 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 Class 1B is a carbide solution treated 316N stainless steel further having a minimum tensile requirement of 80 ksi, yield 35 ksi and maximum hardness limit of 223 HBW or 96 HRB. This specification covers requirements for chemical composition, mechanical properties, hardness, heat-treatment and recommended nuts-washers for Grade B8MN Class 1B 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 1B & 1D	All Sizes	80	35	30	40	223 HBW or 96 HRBA

Heat Treatment: Carbide Solution Treated
A: For sizes 3⁄4 in. in diameter and smaller, a maximum hardness of 241 HBW (100 HRB) is permitted.