ASTM F594 covers the chemical and mechanical requirements for stainless steel nuts in diameters ranging from 1/4″ to 1-1/2″ inclusive and for use with fasteners conforming to ASTM F593. These nuts are for general purpose usage and are available in seven alloy groups. Below is a basic summary of the common grades within the ASTM F594 specification. A number of other less common grades of ASTM F594 exist but are not detailed in the description below. The Mechanical table here is limited to Alloy groups 1 and 2, as those are the most common and the Chemical table is only showing the most common alloy grades used for their respective alloy groups. More detailed information can be found in the ASTM F594 standard on the ASTM website.
F594 Alloy Groups
| Alloy Group | Alloy Designation | Alloy Type |
|---|
| 1 | 303, 304, 304L, 305, 384, XM1, 18-9LW, 302HQ, 303Se | Austenitic |
| 2 | 316, 316L | Austenitic |
| 3 | 321, 347 | Austenitic |
| 4 | 430, 430F | Ferritic |
| 5 | 410, 416, 416Se | Martensitic |
| 6 | 431 | Martensitic |
| 7 | 630 (17-4) | Precipitation Hardening |
| *The selection of an alloy within each group is at the discretion of the manufacturer unless the purchaser requests a specific alloy. |
F594 Mechanical Properties / Condition
| Alloy Group | Condition | Marking | Diameter Range | Proof Stress, Hex Nuts, ksi | Proof Stress, Heavy Hex Nuts, ksi | Rockwell Hardness |
|---|
| 1 | AF | F594A | 1/4 to 1-1/2 | 70 | 76 | B85 max |
| A | F594B | 1/4 to 1-1/2 | 75 | 81 | B65 to 95 |
| CW1 | F594C | 1/4 to 5/8 | 100 | 108 | B95 to C32 |
| CW2 | F594D | 3/4 to 1-1/2 | 85 | 92 | B80 to C32 |
| 2 | AF | F594E | 1/4 to 1-1/2 | 70 | 76 | B85 max |
| A | F594F | 1/4 to 1-1/2 | 75 | 81 | B65 to 95 |
| CW1 | F594G | 1/4 to 5/8 | 100 | 108 | B95 to C32 |
| CW2 | F594H | 3/4 to 1-1/2 | 85 | 92 | B80 to C32 |
F594 Chemical Requirements
| Element, max except as shown | Alloy Group 1, Type 304 | Alloy Group 2, Type 316 |
|---|
| Carbon | 0.08% | 0.08% |
| Manganese | 2.00% | 2.00% |
| Phosphorus | 0.045% | 0.045% |
| Sulfur | 0.030% | 0.030% |
| Silicon | 1.00% | 1.00% |
| Chromium | 18.0 to 20.0% | 16.0 to 18.0% |
| Nickel | 8.0 to 10.5% | 10.0 to 14.0% |
| Copper | 1.00% | |
| Molybdenum | | 2.00 to 3.00% |
