COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 2HM NUTS
ASTM A194 Grade 2HM specifies high-strength, quenched and tempered carbon steel nuts engineered explicitly for severe high-pressure service in corrosive, hydrogen sulfide (H₂S) rich environments. The "HM" designation represents a critical modification to the standard Grade 2H heat-treatment process.
While standard Grade 2H nuts are hardened to achieve maximum tensile strength, Grade 2HM nuts undergo an intensely controlled, higher-temperature tempering process. This strictly restricts the material's maximum hardness to 22 HRC (235 HBW), guaranteeing full compliance with NACE MR0175 / ISO 15156 standards. This precise metallurgical control prevents catastrophic Sulfide Stress Cracking (SSC) and Hydrogen Embrittlement, making 2HM the essential carbon steel fastening solution for sour gas upstream and midstream infrastructure.
■ Product Overview & Specifications
ASTM A194 Grade 2HM is the foundational NACE-compliant carbon steel nut, offering a crucial balance of structural integrity and environmental safety for sour fluid containment.
| Material Classification | Quenched & Tempered Carbon Steel Heavy Hex Nuts |
|---|---|
| UNS Designation | K04002 |
| Microstructure | Tempered Martensite |
| Magnetic State | Magnetic |
| Density | ~7.85 g/cm³ (0.284 lb/in³) |
| Size Range | Metric: M6 to M100 | Imperial: 1/4" to 4" Custom oversized nuts available upon request. |
| Thread Types | UNC, UNF, 8UN, Metric Coarse, Metric Fine |
| Strengthening Method | Quenching & Tempering (Strictly controlled for NACE compliance) |
■ Proprietary Datasheet Download (GATED)
Access professional-grade technical data for ASTM A194 Grade 2HM, including NACE compliance parameters, restricted hardness limits, and sour-service torque charts.
ASTM A194 Grade 2HM — Complete Technical Datasheet
Contains detailed proof load thresholds up to 150 ksi, dimensional tolerances for ASME B18.2.2 heavy hex profiles, and specific dry and lubricated installation torque values for NACE-compliant B7M/2HM assemblies.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
Material traceability is the backbone of safety in lethal sour gas (H₂S) systems. Every lot shipped by Ananka is accompanied by fully authenticated documentation mapping back to raw steel mill certificates.
- EN 10204 Type 3.1: Issued by our independent quality department, providing specific heat-traceable test results (actual chemical analysis, mechanical test results, hardness testing verifying < 22 HRC, and proof load).
- EN 10204 Type 3.2: For critical subsea or "lethal service" applications, we facilitate third-party witness testing (e.g., TUV, BV, or SGS) to provide the highest level of material assurance.
■ Chemical Composition
Grade 2HM shares the exact same medium-carbon steel base chemistry as standard Grade 2H. The performance and safety difference lies entirely in the post-forging heat treatment parameters.
| Carbon (C) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Silicon (Si) |
|---|---|---|---|---|
| 0.40 Min | 1.00 Max | 0.040 Max | 0.050 Max | 0.40 Max |
■ Mechanical Properties
Because Grade 2HM is intentionally restricted in hardness to prevent hydrogen embrittlement in sour gas environments, its proof load stress is capped lower than standard Grade 2H (150 ksi vs 175 ksi for sizes under 1-1/2").
| Mechanical Property | Grade 2HM (Modified) Requirements |
|---|---|
| Proof Load Stress (Heavy Hex) | 150 ksi (1034 MPa) |
| Proof Load Stress (Standard Hex) | 120 ksi (827 MPa) |
| Hardness Range (Brinell) | 159 to 235 HBW (Maximum) |
| Hardness Limit (Rockwell) | 22 HRC Maximum (Strict NACE Limit) |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 2HM |
| Common Trade Name | A194 Gr. 2HM Sour Service Nuts |
| Compliance Code | NACE MR0175 / ISO 15156 |
■ Applications & Industries
Grade 2HM is mandated anywhere standard high pressures intersect with the presence of deadly Hydrogen Sulfide (H₂S) gas.
- Upstream Oil & Gas: Sour gas wellheads, blow-out preventers (BOPs), and production manifolds.
- Petrochemical Refineries: Downstream processing pipelines and sulfur recovery units.
- Subsea Engineering: Submarine pipelines and subsea hydraulic couplings requiring Xylan-coated NACE-compliant bolting.
- Pipeline Valves: Heavy-duty gate, ball, and check valves operating in corrosive onshore and offshore environments.
■ Compatible Fastener Assemblies
To ensure uniform compliance and prevent stress-related joint failures in sour environments, Grade 2HM nuts must strictly be paired with equivalently certified NACE bolting.
| Nuts (A194 Gr 2HM) | Mating Sour-Service Bolts | Mating Sour-Service Studs |
|---|---|---|
| Heavy Hex Nuts | ASTM A193 Grade B7M Heavy Hex Bolts | ASTM A193 Grade B7M Fully Threaded Studs |
| Standard Hex / Jam Nuts | ASTM A193 Grade B7M Socket Head Cap Screws | ASTM A193 Grade B7M Double End Studs |
■ Standards & Specifications
Manufactured to meet the most stringent international dimensional and material codes.
- ASTM A194 / ASME SA194: Standard Specification for Carbon and Alloy Steel Nuts for Bolts for High Pressure or High Temperature Service.
- ASME B18.2.2: Dimensional standard for Square and Hex Nuts (specifically Heavy Hex profiles).
- NACE MR0175 / ISO 15156: Materials for use in H₂S-containing environments in oil and gas production.
- ASME B1.1 / B1.13M: Unified Inch and Metric Screw Thread profiles.
■ Torque & Installation Guidelines (Typical B7M / 2HM Pairing)
Because ASTM A193 Grade B7M studs have a lower yield strength (80 ksi) compared to standard B7 studs (105 ksi) due to NACE hardness restrictions, the required installation torque is significantly lower. Over-torquing will stretch and permanently yield the stud.
| Nominal Diameter | Threads Per Inch (UNC) | Target Torque — Dry (ft-lbs) | Target Torque — Lubricated (ft-lbs) |
|---|---|---|---|
| 1/2" | 13 | 65 | 50 |
| 5/8" | 11 | 130 | 95 |
| 3/4" | 10 | 225 | 170 |
| 1" | 8 | 540 | 400 |
■ Why Choose Ananka Group?
Ananka Group is a leading manufacturing-driven organization specializing in NACE-compliant bolting packages for the global energy sector.
- In-House Manufacturing: Complete production control from raw material selection and hot forging through to precision thread tapping and CNC machining.
- 100% Traceability & NACE Compliance: Strict heat-treatment controls and hardness testing ensure every Grade 2HM nut falls safely below the 22 HRC threshold. Heat marks and the '2HM' grade identifier are permanently stamped on every nut.
- Custom Surface Coatings: Supplied plain, hot-dip galvanized (HDG), zinc-plated, or PTFE/Xylan coated (such as Xylan 1070 or 1424) for superior offshore corrosion resistance.
- Certifications: ISO 9001:2015, ISO 14001:2015, and strict adherence to ASME and PED 2014/68/EU quality protocols.
■ Frequently Asked Questions
1. What is the main difference between Grade 2H and Grade 2HM?
Standard Grade 2H is quenched and tempered for maximum strength and hardness. Grade 2HM ("Modified") is specifically tempered at a higher temperature to intentionally soften the material, capping its hardness at 22 HRC to prevent Sulfide Stress Cracking (SSC) in H₂S environments.
2. What is the difference between Grade 2HM and Grade 7M?
Both are NACE-compliant sour service nuts restricted to 22 HRC maximum hardness. However, Grade 2HM is a carbon steel, while Grade 7M is a Chromium-Molybdenum alloy steel. The Cr-Mo alloying in 7M provides superior high-temperature strength and creep resistance compared to 2HM.
3. What bolts or studs are typically paired with Grade 2HM nuts?
To maintain a fully NACE MR0175 compliant joint, Grade 2HM nuts must be paired with ASTM A193 Grade B7M studs or bolts.
4. Can Grade 2HM nuts be coated with Teflon/Xylan?
Yes. Grade 2HM nuts are frequently coated with fluoropolymer coatings like Xylan 1070/1424 or PTFE. This provides excellent saltwater corrosion resistance, reduces friction during subsea installation, and dramatically extends the lifespan of offshore equipment.
For project-specific technical support or to request a quote for ASTM A194 Grade 2HM fasteners, please contact the Ananka Group Sales and Engineering Team at sales@anankafasteners.com or via WhatsApp at +91 86557 47687. Secure your high-pressure systems with certified components and world-class manufacturing expertise.