Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature or High Pressure Service and Other Special Purpose Applications
ASTM A193 specification covers alloy and stainless steel bolting for pressure vessels, valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications. Several grades are covered, including ferritic steels and austenitic stainless steels designated B5, B6, B7, B8, B8M, etc.
Selection will depend upon design, service conditions, mechanical properties, and high temperature characteristics. This specification is expressed in both inch-pound units
and in SI units; however, unless the purchase order or contract specifies the applicable A193M specification designation (SI units), the inch-pound units shall apply
Bolting Grade B8
| Grade |
Tensile Class |
Raw Material Description |
| B8 |
Class 1 |
AISI 304 Stainless Steel, Carbide Solution Treated |
| B8 |
Class 2 |
AISI 304 Stainless Steel, Carbide Solution Treated and Strain Hardened |
ASTM A193 Grade B8 Chemical Composition
| Austenitic Steels, Classes 1, 1A, 1D, and 2 |
| Element |
Grade B8, B8A |
| Carbon, max |
0.08 |
| Manganese, max |
2.00 |
| Phosphorus, max |
0.045 |
| Sulfur, max |
0.030 |
| Silicon, max |
1.00 |
| Chromium |
18.0-20.0 |
| Molybdenum |
-- |
| Columnium + Tantalum |
-- |
ASTM A193 Grade B8 Mechanical Properties
| Grade |
Diameter |
Tensile Strength |
Yield Strength |
Elongation |
Reduction |
Hardness |
| Grade B8, B8M, Class 1, 1D |
All Diameters |
515 |
205 |
30 |
50 |
223 HBW or 96 HRB |
| Grade B8, B8C, B8T, Class 2 |
M20 and under |
860 |
690 |
12 |
35 |
321 HBW or 35 HRC |
| Grade B8, B8C, B8T, Class 2 |
M20 to M24, inclusive |
690 |
550 |
20 |
45 |
321 HBW or 35 HRC |
| Grade B8, B8C, B8T, Class 2 |
M24 to M30, inclusive |
655 |
450 |
25 |
45 |
321 HBW or 35 HRC |
| Grade B8, B8C, B8T, Class 2 |
M30 to M36, inclusive |
620 |
345 |
30 |
45 |
321 HBW or 35 HRC |
| Grade B8, B8M2, Class 2B |
M48 and under |
655 |
515 |
25 |
40 |
321 HBW or 35 HRC |
| Grade B8, B8M2, Class 2B |
M48 to M64, inclusive |
620 |
450 |
30 |
40 |
321 HBW or 35 HRC |
| Grade B8, B8M2, Class 2B |
M64 to M72, inclusive |
550 |
380 |
30 |
40 |
321 HBW or 35 HRC |
Heat Treatment
ASTM A193 Grade B8 Marking Requirements
| Class |
Grade |
Grade Symbol |
| Class 1 |
B8 |
B8 |
| Class 1D |
B8 |
B94 |
| Class 2 |
B8 |
B8SH |
| Class 2B |
B8 |
B9 |
Recommended Nuts & Washers
| Bolting Grade |
Nut Grade |
Washer Grade |
| ASTM A193 Grade B8 |
ASTM A194 Grade 8 |
SS 304 |