ASTM A193 Grade B8 Class 2 is a standard material specification for corrosion resistant austenitic stainless steel fasteners, for use in high tensile, high temperature and special purpose applications such as pressure piping & pressure vessels bolting. Grade B8 Class 2 is a carbide-solution-treated & strain-hardened 304 stainless steel with minimum tensile requirement of 125 ksi, yield 100 ksi and maximum hardness of 35 HRC. This specification covers requirements for chemical composition, mechanical properties, hardness, heat-treatment and recommended nuts-washers for Grade B8 Class 2 Fasteners.
| Element | Austenitic Stainless Steel |
|---|---|
| AISI 304 / 304L | |
| CompositionA, % | |
| Carbon | 0.08 max |
| Manganese | 2.00 |
| Phosphorus | 0.045 max |
| Sulfur | 0.030 max |
| Silicon | 1.00 max |
| Chromium | 18.00 - 20.00 |
| Nickel | 8.00 - 11.00 |
AThe intentional addition of Bi, Se, Te, and Pb is not permitted.
| 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 2B,C |
3/4 and under | 125 | 100 | 12 | 35 | 321 HBW or 35 HRC |
| over 3/4 to 1 inclusive | 115 | 80 | 15 | 35 | ||
| over 1 to 1-1/4 inclusive | 105 | 65 | 20 | 35 | ||
| over 1-1/4 to 1-1/2 inclusive | 100 | 50 | 28 | 50 |
B: Carbide Solution Treated and Strain Hardened
C: 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 8 | ASTM A240 TP304 |
| Commonly Produced B8 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 |