ASTM A193 Grade B8M Class 2 is a standard material specification for corrosion resistant 316 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 B8M Class 2 is strain hardened & carbide solution treated 316 stainless steel having minimum requirement of 100 ksi, yield 50 ksi with 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 B8M Class 2 Fasteners.
| Element | Austenitic Stainless Steel |
|---|---|
| AISI 316 / 316L | |
| 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 - 14.00 |
| Molybdenum | 2.00 - 3.00 |
AThe intentional addition of Bi, Se, Te, and Pb is not permitted.
| Tensile Class | Diameter, Inch min, ksi |
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 | 20 | 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.
| Nut Specification | Washer Specification |
|---|---|
| ASTM A194 Grade 8M | ASTM A240 TP316 |
| Commonly Produced B8M 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 |