Table of Contents
- ASTM A194 Grade 2HM Nuts Overview
- ASTM A194 Grade 2HM Specifications
- What are ASTM A194 Grade 2HM Nuts?
- Technical Properties & Composition
- Comparison: Grade 2HM vs. Grade 2H
- Why Sour Gas & Petrochemical Industries Prefer ASTM A194 Grade 2HM Nuts
- Key Technical Advantages
- Key Applications of Grade 2HM Nuts
- Quality Assurance & Hardness Testing
- Global Export Markets
- Frequently Asked Questions
- Contact Aurum Overseas
ASTM A194 Grade 2HM Nuts Suppliers & Exporters
Aurum Overseas is a globally recognized ASTM A194 Grade 2HM Nuts Supplier and ASTM A194 Grade 2HM Nuts Exporter, maintaining stock of heavy hex fasteners specifically heat-treated for sour oil and gas processing, wet hydrogen sulfide service, and high-pressure chemical refining.
Engineered to fulfill NACE MR0175 and ISO 15156 requirements, Grade 2HM nuts undergo post-quench tempering at elevated temperatures. This controlled thermal processing caps core and surface hardness levels to eliminate the threat of sulfide stress cracking when paired with sour service stud bolts like ASTM A193 Grade B7M and A320 Grade L7M.
As an international ASTM A194 Grade 2HM Nuts Exporter, Aurum Overseas delivers batch-tested sour service bolting hardware to engineering procurement contractors (EPCs), offshore operators, and valve manufacturers worldwide.
ASTM A194 Grade 2HM Specifications
| Parameter | Technical Specification / Standard Range |
|---|---|
| Material Standard | ASTM A194 / ASME SA194 Grade 2HM |
| Manufacturing Process | Hot Forged / Cold Formed, Quenched & Tempered Medium Carbon Steel |
| Compliance Standards | NACE MR0175 / ISO 15156 & NACE MR0103 Compliant |
| Size Range | 1/4" to 4" (UNC, UNF, 8UN) | M6 to M100 Metric |
| Dimensional Standards | ASME B18.2.2 (Heavy Hex), ASME B18.2.4.6M Metric Heavy Hex |
| Hardness Limit | Strictly capped at HRC 22 max / 235 HBW max |
| Proof Load Stress | 150 ksi (1/4" to 1-1/2") | 135 ksi (Over 1-1/2" to 4") |
| Minimum Tempering Temp. | 1150°F (620°C) |
| Surface Finishes | Plain Black Oil, Cadmium, PTFE / Xylan Coated, Zinc-Nickel, Hot-Dip Galvanized |
| Certification | EN 10204 3.1 MTR, NACE MR0175 Hardness Verification Report |
What are ASTM A194 Grade 2HM Nuts?
ASTM A194 Grade 2HM nuts are high-reliability heavy hex fasteners engineered to eliminate stress cracking in sour oil, gas, and refining environments. By undergoing high-temperature tempering at or above 1150°F (620°C), these medium carbon steel nuts restrict hardness to 22 HRC maximum to fully comply with NACE MR0175 standards.
As a leading ASTM A194 Grade 2HM Nuts Supplier, Aurum Overseas delivers factory-tested Grade 2HM nuts that ensure leak-free flange seals, maximum load retention, and reliable safety across high-pressure pipelines, valves, and offshore platforms.
Technical Properties & Composition
Chemical Composition (%)
| Element | ASTM A194 Grade 2HM Standard Limits |
|---|---|
| Carbon (C) | 0.15% min |
| Manganese (Mn) | 1.00% max |
| Silicon (Si) | 0.40% max |
| Phosphorus (P) | 0.040% max |
| Sulfur (S) | 0.050% max |
Mechanical Properties & Hardness Limits
| Size Range | Proof Load Stress | Maximum Hardness (Rockwell) | Maximum Hardness (Brinell) | Minimum Tempering Temp. |
|---|---|---|---|---|
| 1/4" to 1-1/2" Inclusive | 150 ksi | 22 HRC max | 235 HBW max | 1150°F (620°C) |
| Over 1-1/2" to 4" | 135 ksi | 22 HRC max | 235 HBW max | 1150°F (620°C) |
Comparison: Grade 2HM vs. Grade 2H
| Technical Parameter | ASTM A194 Grade 2HM | ASTM A194 Grade 2H |
|---|---|---|
| Target Application | Sour gas and wet hydrogen sulfide corrosive service | Standard high-pressure, high-temperature industrial flange bolting |
| NACE MR0175 Compliance | Mandatory (100% compliant) | Non-compliant (exceeds maximum allowed hardness) |
| Hardness Limit | Strictly capped at 22 HRC max (235 HBW) | 24 to 35 HRC (248 – 327 BHN) |
| Minimum Tempering Temp. | 1150°F (620°C) | 1000°F (538°C) |
| Proof Load Stress (Up to 1-1/2") | 150 ksi | 175 ksi |
| Hardness Testing Requirement | 100% batch core & surface hardness verification | Standard statistical quality sampling |
Why Sour Gas & Petrochemical Industries Prefer ASTM A194 Grade 2HM Nuts
Wet hydrogen sulfide corrosion generates free hydrogen ions that cause sudden hydrogen embrittlement and catastrophic joint failure in standard high-hardness bolting.
As a high-capacity ASTM A194 Grade 2HM Nuts Exporter, Aurum Overseas supplies Grade 2HM fasteners tempered at 1150°F (620°C) to cap core hardness below 22 HRC. This controlled strain relief prevents hydrogen migration into grain boundaries, guaranteeing leak-free joint integrity across sour crude pipelines, amine units, and hydrotreaters.
Key Technical Advantages
Microstructural Strain Relief
High tempering temperatures eliminate internal stresses introduced during cold forging or thread rolling.
Heavy Hex Dimensioning
Expanded across-flats width provides an increased bearing surface area to evenly spread preloads across flange gaskets.
Matched Sour Service Pairing
Integrates with A193 B7M and A320 L7M stud bolts without inducing galvanic or hardness imbalances.
Coating Integration
Machined to thread tolerance standards that accommodate Xylan, PTFE, or cadmium anti-galling coatings.
Key Applications of Grade 2HM Nuts
| Industry Sector | Typical Equipment Application | Service Environment |
|---|---|---|
| Sour Oil Refining | Amine reboilers, hydrotreating reactors, sour water strippers | Wet hydrogen sulfide streams, high partial pressures, elemental sulfur exposure |
| Offshore Production | Subsea Christmas trees, wellhead manifolds, choke valves | High-pressure sour crude, marine atmospheres, dynamic line pressure |
| Gas Processing | Acid gas removal units, Claus sulfur recovery systems | Highly corrosive sour gas streams, thermal stress cycling |
| Petrochemical Distribution | Sour gas transmission pipelines, pig launchers, and receivers | Cyclic pressure surges, soil stress, hydrogen charging risk |
Quality Assurance & Hardness Testing
As an established ASTM A194 Grade 2HM Nuts Supplier and ASTM A194 Grade 2HM Nuts Exporter, Aurum Overseas enforces strict testing procedures to guarantee batch-wide NACE compliance.
- 100% Batch Hardness Testing: Individual Rockwell C surface and core hardness measurements on every production lot per ASTM A194 supplementary guidelines.
- Chemical Spectrometry: Optical Emission Spectroscopy (OES) verifying precise carbon, phosphorus, and sulfur limits.
- Proof Load Testing: Full-scale hydraulic tension testing confirming 150 ksi thread yield capacity.
- Dimensional Inspection: Thread pitch diameter and flank angle checks using calibrated Go/No-Go gauges.
- EN 10204 3.1 Certification: Documented Material Test Reports (MTRs) detailing heat treatment charts, chemistry, and hardness values.
Global Export Markets
As an international ASTM A194 Grade 2HM Nuts Exporter, Aurum Overseas maintains inventory ready for immediate shipment to energy infrastructure projects across global markets.
USA
Canada
Mexico
Germany
United Kingdom
France
Italy
Netherlands
Norway
UAE
Saudi Arabia
Qatar
Kuwait
Oman
Singapore
Malaysia
Australia
Frequently Asked Questions
The "M" indicates modified heat treatment parameters where high-temperature tempering restricts hardness to HRC 22 maximum, meeting NACE MR0175 standards for sour service.
Steel fasteners with hardness levels above 22 HRC are vulnerable to sulfide stress cracking in wet hydrogen sulfide environments.
Grade 2HM nuts are paired with ASTM A193 Grade B7M stud bolts or ASTM A320 Grade L7M studs in sour service piping systems.
Grade 2HM nuts are tempered at higher temperatures to cap hardness at 22 HRC max for sour service, while standard Grade 2H nuts allow hardness up to 35 HRC for general high-pressure applications.
Yes, ASTM A194 mandates strict hardness sampling and core verification for Grade 2HM lots to ensure no individual nut exceeds the 22 HRC threshold.
Contact Aurum Overseas
Aurum Overseas manufactures and stocks certified ASTM A194 Grade 2HM Nuts built for sour gas processing, refining, and subsea oil production systems with fast global dispatch.
Contact our technical sales team to request pricing, material test reports, and stock availability.