COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 7M NUTS
ASTM A194 Grade 7M specifies high-strength, quenched and tempered chromium-molybdenum alloy steel nuts engineered explicitly for severe high-pressure, elevated-temperature, and highly corrosive sour gas (H₂S) environments. The strategic addition of chromium and molybdenum provides greater thermal stability and creep resistance compared to standard carbon steel grades like 2M.
The "M" designation indicates a Modified heat treatment process. While standard Grade 7 nuts are hardened for maximum proof load, Grade 7M is rigorously tempered to restrict its maximum hardness to 22 HRC (235 HBW). This precise metallurgical control ensures absolute compliance with NACE MR0175 / ISO 15156, preventing catastrophic Sulfide Stress Cracking (SSC) and Hydrogen Embrittlement in critical upstream and petrochemical infrastructure.
■ Product Overview & Specifications
ASTM A194 Grade 7M is the premier NACE-compliant fastening solution for high-temperature sour service applications, offering superior alloy stability over Grade 2M.
| Material Classification | Quenched & Tempered Alloy Steel (Cr-Mo) Heavy Hex Nuts |
|---|---|
| UNS Designation | G41400 (Typically AISI 4140 / 4142 modified) |
| 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 7M, including NACE compliance parameters, hardness limits, and sour-service torque charts.
ASTM A194 Grade 7M — 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/7M 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 7M features a robust Chromium-Molybdenum alloy profile. This provides enhanced elevated-temperature strength and oxidation resistance compared to the medium-carbon Grade 2M.
| Carbon (C) | Manganese (Mn) | Chromium (Cr) | Molybdenum (Mo) | Phosphorus (P) | Sulfur (S) | Silicon (Si) |
|---|---|---|---|---|---|---|
| 0.37 – 0.49 | 0.65 – 1.10 | 0.75 – 1.20 | 0.15 – 0.25 | 0.035 Max | 0.040 Max | 0.15 – 0.35 |
■ Mechanical Properties
Grade 7M sacrifices maximum tensile capability in exchange for environmental safety. The restricted hardness guarantees the material remains ductile enough to resist hydrogen-induced cracking.
| Mechanical Property | Grade 7M (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 7M |
| Common Trade Name | A194 Gr. 7M Cr-Mo Sour Service Nuts |
| Compliance Code | NACE MR0175 / ISO 15156 |
■ Applications & Industries
Grade 7M is mandated anywhere elevated temperatures combine with high pressures and deadly Hydrogen Sulfide (H₂S) gas.
- Upstream Oil & Gas: High-temperature sour gas wellheads, blow-out preventers (BOPs), and Christmas trees.
- Petrochemical Refineries: Hydrocracking units, flare stacks, and high-temp desulfurization pipelines.
- Subsea Manifolds: Deepwater drilling infrastructure requiring Xylan-coated NACE-compliant bolting.
- Pipeline Valves: Actuators and heavy-duty gate valves operating in corrosive onshore and offshore environments.
■ Compatible Fastener Assemblies
To ensure uniform compliance and prevent galvanic or stress-related failures, Grade 7M nuts must strictly be paired with similarly alloyed, NACE-certified bolting.
| Nuts (A194 Gr 7M) | 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 / 7M 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 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 7M nut falls safely below the 22 HRC threshold. Heat marks and the '7M' 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 2M and Grade 7M?
Both are NACE-compliant sour service nuts restricted to 22 HRC maximum hardness. However, Grade 2M is a medium-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 2M.
2. What is the difference between Grade 7 and Grade 7M?
Standard Grade 7 is quenched and tempered for maximum strength and hardness (similar to 2H). Grade 7M ("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.
3. What bolts or studs are typically paired with Grade 7M nuts?
To maintain a fully NACE MR0175 compliant and thermally compatible joint, Grade 7M nuts must be paired with ASTM A193 Grade B7M studs or bolts.
4. Can Grade 7M nuts be coated with Teflon/Xylan?
Yes. Grade 7M 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 7M 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.