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.
