Product Overview
Bolted joints fail at the nut as often as at the stud. An ASTM A194 2H nut is the nut half of the standard B7/2H bolting pair used on flanged joints in refineries, petrochemical plants, power stations and heat exchangers - heat-treated, heavy hex, and made to take the same load and temperature the stud sees.
We supply 2H heavy hex nuts from 1/2" to 4" in UNC and 8UN threads, plain or hot-dip galvanized, with 2HM available as a sour-service variant. They're made to match our ASTM A193 B7 stud bolts, because the pair is bought together and should be supplied together.
Kennen Steel International Co., Ltd. is a China-based steel trading company and a first-tier mill agent. We don't run a factory - we buy direct from vetted source mills, hold them to the specification you agree, and manage the export side end to end. Three decades of steel trading in China and a vetted network of source mills is what stands behind every order.
Most of our nut shipments go to MRO distributors, valve and flange traders, and plant contractors across Africa, the Middle East and Southeast Asia - buyers who order studs and nuts as one line item and need the grade, the match and the paperwork to line up.
Key Advantages
Direct mill supply, not a resold catalogue
We buy from the mills and we inspect what they make. The grade stamped on the nut is the grade in the box, and if a batch doesn't meet the agreed specification it doesn't ship. You get mill quality with someone accountable for the order.
Matched to B7 studs as one bolting pair
A 2H nut is specified together with an A193 B7 stud, not chosen on its own - the pair works as a system. We supply both, so the thread series, grade and finish match and you're not chasing a compatible nut after the studs land.
Heat-treated for high-temperature service
2H is the nut grade that goes with B7 in elevated-temperature, high-pressure joints. It's heat-treated carbon steel to ASTM A194 2H, with the hardness and properties for the heat confirmed on the mill test certificate rather than taken on trust.
Heavy hex, sized for the job
Heavy hex dimensions follow ASME B18.2.2, which gives more bearing area and wall thickness than a standard hex nut - the right form for a flange stud under load. Sizes run 1/2" to 4", so the nut matches the stud without an adapter.
Threads that mate with your piping spec
UNC as the everyday imperial series; 8UN where the larger sizes call for it. Tell us the line spec and we'll supply the thread series it assumes.
Plain or hot-dip galvanized
Plain (black) for the usual high-temperature service, hot-dip galvanized where the joint sees outdoor or atmospheric exposure. Coating choice is a spec decision - tell us the service and we'll confirm what fits.
2HM available for sour service
Where the line is wet H2S, 2HM to NACE MR0175 may be the specified nut rather than plain 2H, with tighter hardness control. We can quote it as a related variant - availability and documentation are confirmed per order.
Documents that clear the gate
An EN 10204 3.1 mill test certificate per batch comes as standard, dimensional inspection is run to the cited standard, third-party inspection can be arranged on request, and we support the destination conformity paperwork some markets require, such as KEBS or PVoC.
Technical Specifications
| Item | Specification |
|---|---|
| Product Name | 2H Nuts (ASTM A194 2H heavy hex nuts for high-temperature bolting) |
| Standard | ASTM A194 2H (2HM to NACE MR0175 available as a related variant, to be confirmed) |
| Nut Form | Heavy hex, dimensions to ASME B18.2.2 |
| Material | Carbon steel, heat treated |
| Grade | 2H per ASTM A194 (matched to ASTM A193 B7 studs) |
| Size Range | 1/2"–4" (M12–M100) |
| Thread Series | UNC as standard; 8UN for larger sizes as specified (2B class) |
| Hardness | Per ASTM A194 2H - the specified range is confirmed per batch on the mill test certificate |
| Proof Load / Mechanical Properties | Per ASTM A194 2H - actual figures confirmed per heat on the mill test certificate |
| Service Temperature | Suitability confirmed against ASTM A194 2H and your joint design; the recommended limit is confirmed per application |
| Finishes | Plain (black), hot-dip galvanized (HDG) |
| Coating Thickness | Confirmed per order |
| Matching Studs | ASTM A193 B7 (supplied as a matched bolting pair) |
| Marking | Grade and heat / lot marking per the cited standard; confirmed per order |
| Dimensional Tolerance | In accordance with the cited standard; confirmed per size |
| Packing | Wooden cases or drums with protective lining, strapped for export |
| Certificate | EN 10204 3.1 mill test certificate per batch |
Grade, thread series, finish and packing are confirmed against your piping specification and destination before the order is placed.
Step-by-Step Manufacturing Process
- Bar / wire selection - carbon steel bar or wire of the required chemistry is inspected and cut to the blank size, since what goes in determines whether the nut can reach 2H.
- Hot forming - the blank is forged and punched to the heavy hex profile, with the chamfer and bearing faces formed so the nut seats flat on a flange washer.
- Heat treatment - the nuts are quenched and tempered to develop the hardness and mechanical properties called for by ASTM A194 2H.
- Threading - internal threads are cut or tapped to the specified series (UNC or 8UN) so the nut mates cleanly with its B7 stud.
- Thread gauging - threads are gauged per size and series against the specified class, because a nut that won't run down the stud is scrap regardless of grade.
- Coating - plain or hot-dip galvanized finish is applied where specified; the coating step and any pre-treatment are confirmed per order.
- Testing and marking - hardness and mechanical tests are run on samples from the batch, the nut is marked with grade and lot, and the batch certificate is raised.
- Packing - nuts are packed with protective lining into wooden cases or drums, strapped for export, and where ordered, held as a set with their matching B7 studs.
Quality Assurance & Certificates
- EN 10204 3.1 mill test certificate per batch - chemistry, mechanical properties and hardness
- Dimensional inspection against the cited standard (ASTM A194 2H / ASME B18.2.2)
- Thread gauging per size and series (UNC / 8UN, 2B class)
- Hardness verification, including the tighter control 2HM requires where that variant is specified
- Coating check for hot-dip galvanized finishes
- Third-party inspection available on request (SGS, BV, Intertek)
- Documentation support for destination conformity schemes (for example KEBS or PVoC)
- Every shipment is checked against the agreed specification before it leaves, so what lands matches what was ordered
Core Applications
- Flanged joints in refinery and petrochemical piping
- Power-station piping, steam lines and turbine connections
- Heat exchangers, pressure vessels and reactors
- Valve, pump and flange assemblies
- Oil, gas and process pipelines in high-temperature and high-pressure service
- MRO distributor stock and plant maintenance programmes
- Sour-service (wet H2S) duty with 2HM, where specified
FAQ
What is an ASTM A194 2H nut used for?
It's the nut for high-temperature and high-pressure bolted joints - flanged connections in refineries, petrochemical plants, power stations and heat exchangers. A194 2H is the nut grade that pairs with an A193 B7 stud, so wherever the piping spec says B7, it normally says 2H alongside it.
What's the difference between a 2H nut and a standard hex nut?
A 2H nut is a heavy hex nut - thicker and larger across the flats than a standard hex nut, per ASME B18.2.2 - and it's heat-treated carbon steel to a defined grade (ASTM A194 2H) rather than a general-purpose nut. It's made to carry the load of a B7 flange stud at temperature, which an ordinary hex nut isn't specified for.
What's the difference between 2H and 2HM?
2H is the standard nut grade for B7 bolting. 2HM is the variant for sour service, specified to NACE MR0175, with a lower and tighter hardness limit. If the line handles wet H2S, your spec will usually say 2HM. We can supply it as a related variant - tell us the service and we'll confirm availability and documentation.
Do the nuts come with studs?
Yes. We supply these nuts matched to our ASTM A193 B7 stud bolts, since the two are a system and are normally ordered together. Tell us the stud size and thread series and we'll supply the matching 2H nuts as one line.
Should I use UNC or 8UN thread?
UNC is the everyday imperial series; 8UN is common on larger sizes and where the piping spec calls for it. It's a spec decision, not a preference - send us the line specification and we'll supply the series it assumes.
Which finish should I choose?
Plain (black) for the usual high-temperature service, hot-dip galvanized where the joint sees outdoor or atmospheric exposure. Finish choice depends on the service environment - tell us where the joint is going and we'll confirm what fits.
What hardness do the nuts meet?
Hardness is per ASTM A194 2H, with the actual range for your batch stated on the mill test certificate. We quote the certificate rather than a brochure number, and for 2HM the tighter control that grade requires is verified the same way.
Do you provide test certificates and inspection?
Yes. Every batch ships with an EN 10204 3.1 mill test certificate covering the agreed details. Third-party inspection (SGS, BV, Intertek) can be arranged on request, and we can support destination conformity documentation such as KEBS or PVoC where your market requires it.
Can you supply non-standard sizes or a specific thread form?
Heavy hex nuts run 1/2" to 4" (M12–M100) as standard. Send us the size, thread series and finish from your piping spec and we'll confirm before you commit.
Are you the manufacturer?
No. We're a China-based steel trading company and a first-tier mill agent. We buy direct from vetted source mills, verify grade and dimensions, and manage the export - finishes, packing, certificates and shipping. You get mill quality with someone accountable for the order.
