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
| Grade | Tensile Class | Raw Material Description |
|---|---|---|
| B5 | 4-6% Chromium Ferritic Steel | |
| B6 | 13% Chromium Ferritic Steel | |
| B6X | 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 | Class 1 | AISI 304 Stainless Steel, Carbide Solution Treated |
| B8 | Class 2 | AISI 304 Stainless Steel, Carbide Solution Treated and Strain Hardened |
| B8A | AISI 304 Stainless Steel, Carbide solution treated in the finished condition | |
| B8C | Class 1 | AISI 347 Stainless Steel, Carbide Solution Treated |
| B8C | Class 2 | AISI 347 Stainless Steel, Carbide Solution Treated and Strained Hardened |
| B8CA | AISI 347 Stainless Steel, Carbide Solution Treated in Finished Condition | |
| B8M | Class 1 | AISI 316 Stainless Steel, Carbide Solution Treated |
| B8M | Class 2 | AISI 316 Stainless Steel, Carbide Solution Treated and Strain Hardened |
| B8MA | AISI 316 Stainless Steel, Carbide Solution Treated in Finished Condition | |
| B8M2 | AISI 316 Stainless Steel, Carbide Solution Treated and Strain Hardened | |
| B8M3 | AISI 316 Stainless Steel, Carbide Solution Treated and Strain Hardened | |
| B8P | Class 1 | AISI 305 Stainless Steel, Carbide Solution Treated |
| B8P | Class 2 | AISI 305 Stainless Steel, Carbide Solution Treated and Strain Hardened |
| B8PA | AISI 305 Stainless Steel, Carbide Solution Treated in Finished Condition | |
| B8N | AISI 304N Stainless Steel, Carbide Solution Treated | |
| B8N | AISI 304N Stainless Steel, Carbide Solution Treated and Strain Hardened | |
| B8MLCuN | AISI 304N Stainless Steel, Carbide Solution Treated and Strain Hardened | |
| B8MLCuN | UNS S31254 Stainless Steel, Carbide Solution Treated and Strain Hardened | |
| B8MLCuNA | UNS S31254 Stainless Steel, Carbide Solution Treated | |
| B8T | Class 1 | AISI 321 Stainless Steel, Carbide Solution Treated |
| B8T | Class 2 | AISI 321 Stainless Steel, Carbide Solution Treated and Strain Hardened |
| B8TA | AISI 321 Stainless Steel, Carbide Solution Treated in Finished Condition | |
| B8R | Nitronic 50/UNS S20910 Stainless Steel, Carbide Solution Treated | |
| B8RA | Nitronic 50/UNS S20910 Stainless Steel, Carbide Solution Treated in Finished Condition | |
| B8S | Nitronic 60/UNS S21800 Stainless Steel, Carbide Solution Treated | |
| B8SA | Nitronic 60/UNS S21800 Stainless Steel, Carbide Solution Treated | |
| B8LN | AISI 304LN Stainless Steel, Carbide Solution Treated | |
| B8LNA | AISI 304LN Stainless Steel, Carbide Solution Treated in Finished Condition | |
| B8MLN | AISI 316LN Stainless Steel, Carbide Solution Treated | |
| B8MLNA | AISI 316LN Stainless Steel, Carbide Solution Treated in Finished Condition | |
| B8CLN | AISI 347LN Stainless Steel, Carbide Solution Treated | |
| B8CLNA | AISI 347LN Stainless Steel, Carbide Solution Treated in Finished Condition |
Each alloy shall conform to the chemical composition requirements.
| Ferritic Steels | ||||
|---|---|---|---|---|
| Element | Grade B5 | Grade B6, B6X | Grade B7, 7M | Grade B16 |
| Carbon | 0.10 min | 0.08-0.15 | 0.37-0.49 | 0.36-0.47 |
| Manganese, max | 1.00 | 1.00 | 0.65-1.10 | 0.45-0.70 |
| Phosphorus, max | 0.040 | 0.040 | 0.035 | 0.035 |
| Sulfur, max | 0.030 | 0.030 | 0.040 | 0.040 |
| Silicon | 1.00 max | 1.00 max | 0.15-0.35 | 0.15-0.35 |
| Chromium | 4.00-6.00 | 11.5-13.5 | 0.75-1.20 | 0.80-1.15 |
| Molybdenum | 0.40-0.65 | -- | 0.15-0.25 | 0.50-0.65 |
| Vanadium | -- | -- | -- | 0.25-0.35 |
| Aluminium, max | -- | -- | -- | 0.015 |
| Austenitic Steels, Classes 1, 1A, 1D, and 2 | |||
|---|---|---|---|
| Element | Grade B8, B8A | Grade B8C, B8CA | Grade B8M, B8MA, B8M2, B8M3 |
| Carbon, max | 0.08 | 0.08 | 0.08 |
| Manganese, max | 2.00 | 2.00 | 2.00 |
| Phosphorus, max | 0.045 | 0.045 | 0.045 |
| Sulfur, max | 0.030 | 0.030 | 0.030 |
| Silicon, max | 1.00 | 1.00 | 1.00 |
| Chromium | 18.0-20.0 | 17.0-19.0 | 16.0-18.0 |
| Molybdenum | -- | -- | 2.00-3.00 |
| Columnium + Tantalum | -- | 10 x carbon content, min – 1.10 max | -- |
| Austenitic Steels, Classes 1A, 1B, 1D, and 2 | |||
|---|---|---|---|
| Element | Grade B8N, B8NA | Grade B8MN, B8MNA | Grade B8MLCuN, B8MLCuNA |
| Carbon | 0.10 min | 0.08-0.15 | |
| Manganese, max | 1.00 | 1.00 | |
| Phosphorus, max | 0.040 | 0.040 | |
| Sulfur, max | 0.030 | 0.030 | |
| Silicon | 1.00 max | 1.00 max | |
| Chromium | 4.00-6.00 | 11.5-13.5 | |
| Molybdenum | 0.40-0.65 | -- | |
| Columnium + Tantalum | -- | ||
| Austenitic Steel, Classes 1, 1A and 2 | |||
|---|---|---|---|
| Element | Grade B8T, B8TA | ||
| Carbon | 0.10 min | ||
| Manganese, max | 1.00 | ||
| Phosphorus, max | 0.040 | ||
| Sulfur, max | 0.030 | ||
| Silicon | 1.00 max | ||
| Chromium | 4.00-6.00 | ||
| Molybdenum | 0.40-0.65 | ||
| Austenitic Steels, Classes 1C and 1D | |||
|---|---|---|---|
| Element | Grade B8R, B8RA | Grade B8S, B8SA | |
| Carbon, max | 0.10 min | 0.08-0.15 | |
| Manganese | 4.00-6.00 | 1.00 | |
| Phosphorus, max | 0.040 | 0.040 | |
| Sulfur, max | 0.030 | 0.030 | |
| Silicon | 1.00 max | 1.00 max | |
| Chromium | 4.00-6.00 | 11.5-13.5 | |
| Molybdenum | 0.40-0.65 | -- | |
The material as represented by the tension specimens shall conform to the requirements at room temperature after heat treatment. Alternatively, stainless strain hardened fasteners (Class 2, 2B, and 2C) shall be tested full size after strain hardening to determine tensile strength and yield strength and shall conform to the requirements prescribed in Table 2 and 3. Should the results of full size tests conflict with results of tension specimen tests, full size test results shall prevail.
| Grade | Diameter | Tensile Strength | Yield Strength | Elongation | Reduction | Hardness |
|---|---|---|---|---|---|---|
| Grade B5 | Up to M100, inclusive | 690 | 550 | 16 | 50 | -- |
| Grade B6 | Up to M100, inclusive | 760 | 585 | 15 | 50 | -- |
| Grade B6X | Up to M100, inclusive | 620 | 485 | 16 | 50 | 26 HRC |
| Grade B7 | M64 and under | 860 | 720 | 16 | 50 | 321 HBW or 35 HRC |
| Grade B7 | Over M64 to M100 | 795 | 655 | 16 | 50 | 321 HBW or 35 HRC |
| Grade B7 | Over M100 to M180 | 690 | 515 | 18 | 50 | 321 HBW or 35 HRC |
| Grade B7M | M100 and under | 690 | 550 | 18 | 50 | 235 HBW or 99 HRB |
| Grade B7M | M100 and over | 690 | 515 | 18 | 50 | 235 HBW or 99 HRB |
| Grade B16 | M64 and under | 860 | 725 | 18 | 50 | 321 HBW or 35 HRC |
| Grade B16 | Over M64 to M100 | 760 | 655 | 17 | 45 | 321 HBW or 35 HRC |
| Grade B16 | Over M100 to M180 | 690 | 585 | 16 | 45 | 321 HBW or 35 HRC |
| 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 |
| Grade B8A, B8MA, B8CA, B8TA, B8MLCuNA, Class 1A | All Diameters | 515 | 205 | 30 | 50 | 192 HBW or 90 HRB |
| Grade B8M, B8MLCuN, Class 2 | M20 and under | 760 | 655 | 15 | 45 | 321 HBW or 35 HRC |
| Grade B8M, B8MLCuN, Class 2 | M20 to M24, inclusive | 690 | 550 | 20 | 45 | 321 HBW or 35 HRC |
| Grade B8M, B8MLCuN, Class 2 | M24 to M30, inclusive | 655 | 450 | 25 | 45 | 321 HBW or 35 HRC |
| Grade B8M, B8MLCuN, Class 2 | M30 to M36, inclusive | 620 | 345 | 30 | 45 | 321 HBW or 35 HRC |
| Grade B8M3, Class 2C | M48 and under | 585 | 450 | 30 | 60 | 321 HBW or 35 HRC |
| Grade B8M3, Class 2C | Over M48 | 585 | 415 | 30 | 60 | 321 HBW or 35 HRC |
| Grade B8C, B8T, Class 1 | All Diameters | 515 | 205 | 30 | 50 | 192 HVW or 90 HRB |
| Grade B8R, Class 1C, 1D | All Diameters | 690 | 380 | 35 | 55 | 271 HBW or 28 HRC |
| Grade B8RA Class 1C | All Diameters | 690 | 380 | 35 | 55 | 271 HBW or 28 HRC |
| Grade B8S, Class 1C, 1D | All Diameters | 655 | 345 | 35 | 55 | 271 HBW or 28 HRC |
| Grade B8SA Class 1C | All Diameters | 655 | 345 | 35 | 55 | 271 HBW or 28 HRC |
Ferritic steels shall be allowed to cool to a temperature below the cooling transformation range immediately after rolling or forging. Materials shall then be uniformly reheated to the proper temperature to refine the grain (a group thus reheated being known as a quenching charge), quenched in a liquid medium under substantially uniform conditions for each quenching charge, and tempered. The minimum tempering temperature shall be as specified in Tables 2 and 3.
| Class | Grade | Grade Symbol |
|---|---|---|
| Class 1 | B8 B8C B8M B8P B8T B8LN B8MLN B8CLN |
B8 B8C B8M B8P B8T B8F or B8LN B8G or B8MLN B8Y or B8CLN |
| Class 1A | B8A B8CA B8MA B8PA B8TA B8LNA B8MLNA B8NA B8MNA B8MLCuNA B8CLNA |
B8A B8B or B8CA B8D or B8MA B8H or B8PA B8J or B8TA B8L or B8LNA B8K or B8MLNA B8V or B8MA B8W or B8MNA B9K or B8MLCuNA B8Z or B8CLNA |
| Class 1B | B8N B8MN B8MLCuN |
B8N B8Y or B8MN B9J or B8MLCuN |
| Class 1C | B8R B8RA B8S B8SA |
B9A or B8R B9B or B8RA B9D or B8S B9F or B8SA |
| Class 1D | B8 B8M B8P B8LN B8MLN B8N B8MN B8R B8S B8CLN |
B94 B95 B96 B97 B98 B99 B100 B101 B102 B103 |
| Class 2 | B8 B8C B8P B8T B8N B8M B8MN B8MLCuN |
B8SH B8CSH B8PSH B8TSH B8NSH B8MSH B8YSH B0JSH |
| Class 2B | B8M2 B8 |
B9G or B8M2 B9 |
| Class 2C | B8M3 | B9H or B8M3 |
| Bolting Grade | Nut Grade | Washer Grade |
|---|---|---|
| ASTM A193 Grade B6, B6X | ASTM A194 Grade 6 | Mild Steel |
| ASTM A193 Grade B7,7M | ASTM A194 Grade 2H, 2HM | ASTM F436 |
| ASTM A193 Grade B16 | ASTM A194 Grade 16 | ASTM F436 |
| ASTM A193 Grade B8 | ASTM A194 Grade 8 | SS 304 |
| ASTM A193 Grade B8M, B8MA, B8M2, B8M3 | ASTM A194 Grade 8M, 8MA | SS 316 |
| ASTM A193 Grade B8C, B8CA | ASTM A194 Grade 8C, 8CA | SS 347 |
| ASTM A193 Grade B8T, B8TA | ASTM A194 Grade 8T, 8TA | SS 321 |
| ASTM A193 Grade B8MLCuN, B8MLCuNA | ASTM A194 Grade 8MLCuN, 8MLCuNA | 254SMO / UNS S31254 |
| ASTM A193 Grade B8R, B8RA | ASTM A194 Grade 8R, 8RA | Nitronic 50/UNS S20910 |
| ASTM A193 Grade B8S, B8SA | ASTM A194 Grade 8S, 8SA | Nitronic 60/UNS S21800 |