ASTM A193 Specification for high tensile alloy and stainless steel bolts including most popular grade B5, B6, B7, B7M, B8, B8M, B8T, B16, etc.
ASTM A193 specification covers high tensile alloy and stainless steel fasteners for pressure vessels, valves, flanges, and fittings for high temperature or high pressure service, or other special purpose bolting 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.
(For Metric Units, please visit ASTM A193M Specification)
| Bolt Grade | Raw Material |
|---|---|
| B5 | 5% Chromium Ferritic Steel |
| B6 | 13% Chromium Ferritic Steel |
| B7 | Chromium Molybdenum Alloy Steel, Quenched & Tempered |
| B7M | Chromium Molybdenum Alloy Steel, Quenched & Tempered |
| B16 | Chromium-molybdenum-vanadium Alloy Steel, Quenched & Tempered |
| B8 | AISI 304 Stainless Steel, Carbide Solution Treated |
| B8 Class 2 | AISI 304 Stainless Steel, Carbide Solution Treated and Strain Hardened |
| B8M | AISI 316 Stainless Steel, Carbide Solution Treated |
| B8M Class 2 | AISI 316 Stainless Steel, Carbide Solution Treated and Strain Hardened |
| B8T | AISI 321 Stainless Steel, Carbide Solution Treated |
| B8T Class 2 | AISI 321 Stainless Steel, Carbide Solution Treated and Strain Hardened |
(For all grades, please visit ASTM A193 Grades)
| Element | Grade B5 | Grade B6 | Grade B7, 7M | Grade B16 | Grade B8 | Grade B8M | Grade B8T |
|---|---|---|---|---|---|---|---|
| Carbon | 0.10 min | 0.08-0.15 | 0.37-0.49 | 0.36-0.47 | 0.08 | 0.08 | 0.10 min |
| Manganese, max | 1.00 | 1.00 | 0.65-1.10 | 0.45-0.70 | 2.00 | 2.00 | 1.00 |
| Phosphorus, max | 0.040 | 0.040 | 0.035 | 0.035 | 0.045 | 0.045 | 0.040 |
| Sulfur, max | 0.003 | 0.030 | 0.040 | 0.040 | 0.030 | 0.030 | 0.030 |
| Silicon | 1.00 | 1.00 max | 0.15-0.35 | 0.15-0.35 | 1.00 | 1.00 | 1.00 max |
| Chromium | 4.0-6.0 | 11.5-13.5 | 0.75-1.20 | 0.80-1.15 | 18.0-20.0 | 16.0-18.0 | 4.00-6.00 |
| Molybdenum | 0.40-0.65 | -- | 0.15-0.25 | 0.50-0.65 | -- | 2.00-3.00 | 0.40-0.65 |
| Vanadium | -- | -- | -- | 0.25-0.35 | -- | -- | -- |
| Aluminium, max | -- | -- | -- | 0.015 | -- | -- | -- |
| Bolt Grade | Diameter, in. | Tensile Strength, ksi | Yield Strength ksi | Elongation, % | Reduction, % | Hardness |
|---|---|---|---|---|---|---|
| B5 | Up to 4, inclusive | 100 | 80 | 16 | 50 | -- |
| B6 | Up to 4, inclusive | 110 | 85 | 15 | 50 | -- |
| B7 | 2.5 and under | 125 | 105 | 16 | 50 | 321 HBW or 35 HRC |
| Over 2.5 to 4 | 115 | 95 | 16 | 50 | 321 HBW or 35 HRC | |
| Over 4 to 7 | 100 | 75 | 18 | 50 | 321 HBW or 35 HRC | |
| B7M | 4 and under | 100 | 80 | 18 | 50 | 235 HBW or 99 HRB |
| over 4 to 7 | 100 | 75 | 18 | 50 | 235 HBW or 99 HRB | |
| B16 | 2.5 and under | 125 | 105 | 18 | 50 | 321 HBW or 35 HRC |
| Over 2.5 to 4 | 110 | 95 | 17 | 45 | 321 HBW or 35 HRC | |
| Over 4 to 8 | 100 | 85 | 16 | 45 | 321 HBW or 35 HRC | |
| B8, B8M, Class 1 | All Diameters | 75 | 30 | 30 | 50 | 223 HBW or 96 HRB |
| B8, B8T, Class 2 | 3/4 and under | 125 | 100 | 12 | 35 | 321 HBW or 35 HRC |
| Over 3/4 to 1, inclusive | 115 | 80 | 20 | 45 | 321 HBW or 35 HRC | |
| Over 1 to 1 1/4, inclusive | 105 | 65 | 25 | 45 | 321 HBW or 35 HRC | |
| Over 1 1/4 to 1 1/2, inclusive | 100 | 50 | 30 | 45 | 321 HBW or 35 HRC | |
| B8M, Class 2 | 3/4 and under | 110 | 95 | 15 | 45 | 321 HBW or 35 HRC |
| over 3/4 to 1, inclusive | 100 | 80 | 20 | 45 | 321 HBW or 35 HRC | |
| over 1 to 1 1/4, inclusive | 95 | 65 | 25 | 45 | 321 HBW or 35 HRC | |
| M30 to M36, inclusive | 620 | 345 | 30 | 45 | 321 HBW or 35 HRC |