ASTM A193 Grade B8MN Specification

ASTM A193 Grade B8MN 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 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 heat-treated, work-hardened (or both) austenitic stainless steel further divided into class 1B, class 1D and class 2, each having a distinguished tensile strength. This specification covers requirements for chemical composition, mechanical properties, hardness, heat-treatment and recommended nuts-washers for Grade B8MN Fasteners.

Tensile Class

Property Description
Class 1B & 1D Carbide Solution Treated
Class 2 Carbide Solution Treated & Strain Hardened

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 & 1DA All Sizes 80 35 30 40 223 HBW or 96 HRBB


Class 2C,D		 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

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