COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 2 & 2M NUTS
ASTM A194 Grade 2 and Grade 2M specify medium-carbon steel nuts engineered for moderate to high-temperature and pressure service. While sharing the same fundamental metallurgical chemistry as the high-strength Grade 2H, these grades undergo specific manufacturing and heat-treatment protocols to achieve tailored hardness profiles, making them ideal for distinct industrial environments.
The defining breakthrough of Grade 2M (Modified) is its strictly controlled maximum hardness limit (typically 22 HRC / 235 HBW). This precise heat treatment ensures full compliance with NACE MR0175 / ISO 15156 standards, making Grade 2M the premier fastening choice for sour gas (H₂S) environments where resistance to sulfide stress cracking (SSC) is an absolute safety requirement.
■ Product Overview & Specifications
ASTM A194 Grade 2 and 2M represent the industry benchmark for specialized pressure piping nuts, particularly in upstream oil and gas applications requiring sour service compliance.
| Material Classification | Medium-Carbon Steel Heavy Hex Nuts |
|---|---|
| UNS Designation | K04002 |
| Microstructure | Pearlitic / 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 Grade 2M) |
■ Proprietary Datasheet Download (GATED)
Access professional-grade technical data for ASTM A194 Grade 2 and 2M, including NACE compliance parameters, hardness limits, and mating bolt torque charts.
ASTM A194 Grade 2 & 2M — 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/2M assemblies.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
Material traceability is the backbone of safety in high-pressure and sour service 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, and proof load).
- EN 10204 Type 3.2: For critical infrastructure 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 2 and 2M share the same medium-carbon chemistry profile as Grade 2H. The performance difference lies entirely in the post-forging heat treatment and hardness mapping.
| 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
The mechanical properties highlight the critical difference between the grades: Grade 2M is intentionally restricted in hardness to prevent hydrogen embrittlement in sour gas environments.
| Property | Grade 2 Requirements | Grade 2M (Modified) Requirements |
|---|---|---|
| Proof Load Stress (Heavy Hex) | 150 ksi (1034 MPa) | 150 ksi (1034 MPa) |
| Hardness Range (Brinell) | 159 to 352 HBW | 159 to 235 HBW (Maximum) |
| Hardness Limit (Rockwell) | ~ 38 HRC Max | 22 HRC Maximum (NACE Limit) |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 2 / SA194 Grade 2M |
| Common Trade Name | A194 Gr. 2M Sour Service Nuts |
| Compliance Code | NACE MR0175 / ISO 15156 (For Grade 2M) |
■ Applications & Industries
While Grade 2 is used in general high-pressure systems, Grade 2M is specifically mandated for highly corrosive, hydrogen-sulfide-rich environments.
- Upstream Oil & Gas: Wellheads, Christmas trees, and manifold systems exposed to sour crude and H₂S gas (Grade 2M).
- Petrochemical Refineries: Desulfurization units, catalytic crackers, and downstream processing pipelines.
- Pressure Vessels: Heat exchangers and separation tanks handling aggressive, low-pH hydrocarbons.
- Fluid Control Valves: Bolting for heavy-duty pipeline valves requiring NACE MR0175 certification.
■ Compatible Fastener Assemblies
To maintain NACE compliance across the entire joint, Grade 2M nuts must be paired with equivalently certified sour-service bolting.
| Nuts (A194) | Mating Bolts | Mating Studs |
|---|---|---|
| Grade 2M Heavy Hex Nuts | ASTM A193 Grade B7M Heavy Hex Bolts | A193 Grade B7M Fully Threaded Studs |
| Grade 2 Heavy Hex Nuts | ASTM A193 Grade B7 / B16 Bolts | A193 Grade B7 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 / 2M Pairing)
Because ASTM A193 Grade B7M studs have a lower yield strength (80 ksi) compared to standard B7 studs (105 ksi) to meet NACE limits, the required installation torque is correspondingly lower to prevent yielding 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 2M nut falls safely below the 22 HRC threshold.
- 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 difference between Grade 2, 2M, and 2H?
All three share the same medium-carbon steel chemistry. Grade 2H is quenched and tempered to a high hardness for extreme strength. Grade 2 is standard strength for moderate pressure. Grade 2M ("Modified") is specifically quenched and tempered with a restricted upper hardness limit (max 22 HRC) to safely operate in sour gas environments.
2. Why is a maximum hardness limit important for Grade 2M?
In environments containing Hydrogen Sulfide (H₂S), highly hardened steels are susceptible to Sulfide Stress Cracking (SSC), which can cause catastrophic, sudden fastener failure. Keeping the hardness below 22 HRC (235 HBW) prevents this embrittlement.
3. What bolts or studs are typically paired with Grade 2M nuts?
To maintain a fully NACE MR0175 compliant joint, Grade 2M nuts must be paired with ASTM A193 Grade B7M studs or bolts, which are similarly restricted in hardness.
4. Can Grade 2M nuts be coated with Teflon/Xylan?
Yes. Grade 2M nuts are frequently coated with fluoropolymer coatings like Xylan 1070 or PTFE to provide excellent saltwater corrosion resistance, reduce friction during installation, and extend the lifespan of subsea equipment.
For project-specific technical support or to request a quote for ASTM A194 Grade 2/2M 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.