Patriot Bolt machines ASTM A194 Grade 2H heavy hex nuts, the standard companion nut for A193 B7 stud bolts. 2H nuts are medium-carbon steel, quenched and tempered for high proof strength in high-pressure and high-temperature flange bolting.
We make 2H nuts in standard and special thread sizes, alone or with matching B7 studs. Nuts machined from bar are marked 2HB, as the specification requires. Every order ships with mill test reports traceable to the heat.
A194 2H Heavy Hex Nuts at a Glance
- Specification
- ASTM A194 / ASME SA194 Grade 2H
- Material
- Medium-carbon steel, quenched and tempered at 850 °F min
- Proof stress
- 175 ksi (heavy hex)
- Hardness
- 24–35 HRC (1-1/2 in and under)
- Matching stud
- A193 B7
- Marking
- 2H, or 2HB when machined from bar
Why Engineers Specify A194 2H Nuts
- Strength to match B7. A 175 ksi proof stress lets the nut carry the full load of a B7 stud without stripping.
- Heat treated. Quenching and tempering give consistent hardness from nut to nut.
- Widely specified. 2H is the nut named with B7 in most piping and vessel specifications.
2H is not acceptable for sour service. Use A194 2HM with B7M studs.
A194 2H Specifications
A194 sets proof stress and hardness by nut size.
| Nut size | Proof stress | Hardness, min | Hardness, max |
|---|---|---|---|
| Heavy hex, 1-1/2 in and under | 175 ksi | 248 HBW / 24 HRC | 327 HBW / 35 HRC |
| Heavy hex, over 1-1/2 in | 175 ksi | 212 HBW / 95 HRB | 327 HBW / 35 HRC |
A194 2H Chemical Composition
| Element | Weight % |
|---|---|
| Carbon | 0.40 min |
| Manganese | 1.00 max |
| Phosphorus | 0.040 max |
| Sulfur | 0.050 max |
| Silicon | 0.40 max |
Limits per the current edition of the specification. The mill test report for your heat is the controlling document.
Nut Styles
- Heavy hex nuts to ASME B18.2.2, the standard style for flange studs.
- Heavy hex jam nuts where a thinner nut is needed.
- Threads: UNC through 1 in and 8UN above 1 in, the usual flange series, or the thread on your drawing.
Applications and Industries
- Flange stud sets with A193 B7 studs in refining, petrochemical and power service. See Petrochemical & Refining.
- Oil and gas: Wellhead, valve and pipeline flanges in non-sour service. See Oil & Gas.
- Pressure vessels: Manways, covers and nozzle flanges.
Certification and Traceability
Patriot Bolt is ISO 9001:2015 certified. Each 2H order includes mill test reports traceable to the heat, along with a certificate of conformance to the specification on your purchase order.
Nuts are marked with the grade symbol and our identification on one face.
Compare 2H with other bolting grades in our Fastener Materials Matrix.
A194 2H Heavy Hex Nuts FAQ
What is the difference between 2H and 2HB?
The grade is the same. A194 adds the letter B when the nut is machined from bar stock instead of being forged or cold formed.
Can 2H nuts be used with B7M studs?
No. Sour service needs the hardness-limited 2HM nut with B7M studs.
What is the difference between 2H and Grade 7 nuts?
2H is carbon steel. Grade 7 is chrome-moly alloy steel with the same proof stress and a higher tempering temperature, so it is often chosen for hotter joints and for B16 and L7 studs.
Do you make matching B7 studs?
Yes. We machine B7 stud bolts, so the stud and nuts can come from one source.
Request a Quote
Send us the alloy, nut style, thread size, specification and quantity, or upload your drawing. Our team will confirm the material and lead time. Call (281) 581-0176 or request a quote.
Related: B7 stud bolts · A193 B7 fasteners hub · A194 Grade 7 nuts · All nuts