A194 2HM Heavy Hex Nuts
The sour-service heavy hex nut — 2H tempered to 235 HBW max for NACE MR0175, matched to A193 B7M and A320 L7M studs.
Robust fastener with a thicker, wider hexagonal shape for high-stress applications. Manufactured and stocked across ASTM A194 grades from 2H to 8MA, plain or coated.
ASTM A194 Grade 2HM is the controlled-hardness version of 2H. The same medium-carbon steel is tempered at a higher temperature to a hardness of 159 to 235 HBW, keeping it under the 22 HRC limit NACE MR0175 sets for wet H₂S service. Proof load stress is 150 ksi, still well above the 100 ksi strength of a B7M stud.
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What A194 2HM must meet.
| Nut style and size (in.) | Proof load stress (ksi) | Hardness, min | Hardness, max |
|---|---|---|---|
| Heavy hex, all sizes | 150 | 159 HBW / 84 HRB | 235 HBW / 99 HRB |
| Hex (finished pattern), all sizes | 135 | 159 HBW / 84 HRB | 235 HBW / 99 HRB |
Values per ASTM A194/A194M-24, Tables 1, 2 and 5 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. 100 percent hardness testing; final stress relief after machining at not less than 50 °F below the original tempering temperature (1200 °F minimum in a furnace after an induction temper above 1300 °F).
Quenched in liquid and tempered at 1150 °F (620 °C) minimum. Hardness verified on every nut.
Full A194 2HM data sheet: chemistry, physical properties and standards →
Made to standard or to your drawing.
- Sour gas wellhead and flange bolting
- H₂S process piping and vessels
- Amine and sulfur recovery units
- Offshore production equipment
- Any 2H application requiring NACE compliance