ASTM A194 vs A563 Nuts: Scope, Grades and Substitution
ASTM A194/A194M and ASTM A563 are both nut specifications, but they are written for different service and they are not interchangeable. This comparison uses ASTM A194/A194M-20a and ASTM A563-15, clause by clause.
Clause-by-Clause Comparison
| Topic | ASTM A194/A194M-20a | ASTM A563-15 |
|---|---|---|
| Title | Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts for High Pressure or High Temperature Service, or Both | Carbon and Alloy Steel Nuts |
| Scope | Carbon, alloy and martensitic stainless nuts 1/4 to 4 in. and M12 to M100; austenitic stainless nuts 1/4 in. and M12 up; for high-pressure or high-temperature service (1.1) | Eight grades of carbon and alloy steel nuts for general structural and mechanical uses on bolts, studs and other externally threaded parts (1.1) |
| Grades | 1, 2, 2H, 2HM, 3, 6, 6F, 7, 7M, 16, the Grade 8 family and 9C (Table 1) | O, A, B, C, C3, D, DH and DH3 |
| Substitution | Grade substitution without the purchaser's permission is not allowed (1.1) | The supplier may furnish a stronger grade with notice to the purchaser, unless barred in the order (1.2) |
| Heat treatment example | Grade 2H: liquid quenched, tempered at 850 °F [455 °C] minimum (6.4) | Grades DH and DH3: liquid quenched, tempered at 800 °F minimum (4.3) |
| Coatings | Prohibited unless specified by the purchaser (4.2, Supplementary Requirements S7 and S8) | Hot-dip or mechanically deposited zinc coating covered when zinc-coated fasteners are required (4.7) |
| Weathering grades | None | C3 and DH3 have atmospheric corrosion resistance comparable to A242, A588 and A709 steels (1.3) |
When A194 Applies
A194 is the nut specification for bolting in high-pressure or high-temperature service (1.1). ASTM A193/A193M-20 (13.1) requires nuts supplied with A193 bolting to conform to A194/A194M, and ASTM A320/A320M-21 (10.1, 10.2) names A194 grades for its low-temperature bolting.
When A563 Applies
A563 covers nuts for general structural and mechanical uses (1.1), including weathering grades C3 and DH3 (1.3) and zinc-coated nuts (4.7).
Can A563 DH Replace A194 2H?
Not without the purchaser's permission. A194 forbids grade substitution without it (1.1), the heat treatment differs (2H tempered at 850 °F minimum against 800 °F for DH), and A563 is not written for high-pressure or high-temperature service. See Grade 2H substitutes.
A194 grade pages: Grade 2H · Grade 2HM · Grade 7 · Grade 8 · Grade 8M. More: all A194 grades · ASTM A194 PDF · A194 hub.