ASTM A194 Grade 2H Equivalent: What Can Substitute for 2H?
ASTM A194/A194M-20a does not list equivalent grades for Grade 2H, and clause 1.1 states that grade substitutions without the purchaser's permission are not allowed. Any substitute therefore needs the purchaser's written approval. This page sets out what defines Grade 2H in the standard, so a proposed alternative can be checked against it.
What Defines A194 Grade 2H
- Material (Table 1): carbon steel, 0.40 % carbon minimum (the same row as Grades 2 and 2HM).
- Heat treatment (6.4): liquid quenched and tempered at 850 °F [455 °C] minimum; the certificate states the minimum tempering temperature (12.1).
- Hardness (Table 2): 248 to 327 HB, 24 to 35 HRC up to 1-1/2 in. or M36; 212 to 327 HB above that.
- Proof stress (Tables 5 and 6): 175 000 psi [1205 MPa] heavy hex, 150 000 psi [1035 MPa] hex.
- Marking (Table 7): 2H, or 2HB when machined from bar stock.
Grade 2H vs Other A194 Grades
- Grade 2: same chemistry, stress relieved instead of quenched and tempered, 159 to 352 HB, 150 000 psi heavy hex proof stress.
- Grade 2HM: same chemistry, tempered at 1150 °F [620 °C] minimum, 159 to 235 HB, every nut hardness tested (8.1.3), 150 000 psi heavy hex proof stress.
- Grade 3, Grade 7 and Grade 16: alloy grades in the same 175 000 psi proof stress group with the same 248 to 327 HB hardness (Tables 2 and 5), but different chemistry and tempering temperatures (Table 1, 6.4).
ASTM A563 Grade DH Is Not a Like-for-Like Equivalent
ASTM A563-15 covers carbon and alloy steel nuts for general structural and mechanical uses (1.1), not high-pressure or high-temperature service. Its rules also differ: A563 lets the supplier furnish a stronger grade with notice to the purchaser unless barred (1.2), while A194 forbids substitution without permission. A563 Grade DH is quenched and tempered at 800 °F minimum (4.3), against 850 °F minimum for A194 Grade 2H. See A194 vs A563.
National Standard Equivalents
None of the standards used for this site states a BS, DIN, EN, ISO or JIS equivalent for A194 Grade 2H, so this page lists none. A metric property-class nut to ISO 898-2 is a different specification with different tests; treat it as a substitution that needs approval.
Bolting Used with Grade 2H
ASTM A193/A193M-20 (13.1) requires nuts supplied with A193 bolting to conform to A194/A194M but does not tie a nut grade to each bolt grade; the purchase order names the nut grade. Dimensions: Grade 2H nut dimensions · ASME B18.2.2 heavy hex. More: Grade 2H page · all A194 grades · ASTM A194 PDF · A194 hub.