ASTM A194 Grade 3 is a standard material specification for high tensile nuts and other internally threaded fasteners, made from ferritic stainless steel grade AISI 501. Grade 3 nuts can be produced by means of hot forging, cold forging or machining from bar stock (Grade Type AISI 501) followed by heat treatment. ASTM A194 specification covers requirements for chemical composition, heat treatment, hardness, proof load, etc., for Grade 3 nuts.
Element |
Ferritic Steel |
|---|---|
| AISI 501 Stainless Steel | |
| CompositionA, % | |
| Carbon | 0.10 min |
| Manganese | 1.00 max |
| Phosphorus | 0.04 max |
| Sulfur | 0.03 max |
| Silicon | 1.00 max |
| Chromium | 4.00 - 6.00 |
| Molybdenum | 0.40 - 0.65 |
AThe intentional addition of Bi, Se, Te, and Pb is not permitted.
| Grade | Completed Nuts | Sample Nut After Heat Treatment | |||
|---|---|---|---|---|---|
| Brinell Hardness, BHN |
Rockwell Hardness | Brinell Hardness, BHN, min |
Rockwell Hardness, HRB, min |
||
| HRC | HRB | ||||
| 3 | 248 - 327 | 24 - 35 | ... | 201 | 94 |
Heat Treatment: Grade 3 shall be quenched and tempered at a temperature of at least 1050 °F [565 °C].
| Nominal Size, Inch. | Threads Per Inch | Proof Load, lbf | |
|---|---|---|---|
| Heavy HexA | HexB | ||
| 1/4 | 20 | 5 570 | 4 770 |
| 5/16 | 18 | 9 170 | 7 860 |
| 3/8 | 16 | 13 560 | 11 620 |
| 7/16 | 14 | 18 600 | 15 940 |
| 1/2 | 13 | 24 830 | 21 280 |
| 9/16 | 12 | 31 850 | 27 300 |
| 5/8 | 11 | 39 550 | 33 900 |
| 3/4 | 10 | 58 450 | 50 100 |
| 7/8 | 09 | 80 850 | 69 300 |
| 01 | 08 | 106 000 | 90 900 |
| 1-1/8 | 08 | 138 200 | 118 500 |
| 1-1/4 | 08 | 175 000 | 150 000 |
| 1-3/8 | 08 | 215 800 | 185 000 |
| 1-1/2 | 08 | 261 100 | 223 800 |
A: Based on proof stress of 175 000 psi.
B: Based on proof stress of 150 000 psi.
| Commonly Produced Grade 3 Nuts | ||||
|---|---|---|---|---|
| Hex Nuts | Heavy Hex Nuts | Jam Nuts | Heavy Hex Jam Nuts | Castle Nuts |
| Coupling Nuts | Square Nuts | Thin Square Nuts | All Metal Lock Nuts | Dome Nuts |