ASTM A193 Grade B8MN Class 2 Specification

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.

Recommended Nuts & Washers

Nut Specification Washer Specification
ASTM A194 Grade 8MN ASTM A240 UNS S31651

Fasteners

Commonly Produced B8MN Class 2 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