COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF ASTM A194 GRADE 6 & 6F NUTS
ASTM A194 Grade 6 and Grade 6F specify high-strength, quenched and tempered martensitic stainless steel nuts (Type 410 and 416, respectively) engineered for high-temperature and high-pressure service. These grades provide a critical bridge in industrial fastening, offering higher tensile strength and wear resistance than standard austenitic stainless steels, combined with far greater corrosion and oxidation resistance than carbon steels.
Through a rigorous heat treatment process, Grade 6 achieves exceptional hardness, making it highly resistant to galling and thread wear in severe environments. Grade 6F is the free-machining variant, utilizing a controlled addition of sulfur or selenium to improve machinability for complex custom profiles without critically compromising the structural integrity of the fastener. Both grades are the premier choice for steam and gas turbine bolting, valve trim, and high-temperature pump systems.
■ Product Overview & Specifications
ASTM A194 Grade 6 / 6F represents the industry standard for high-strength stainless pressure piping components. This profile outlines the material's fundamental metallurgical classifications.
| Material Classification | Quenched and Tempered Martensitic Stainless Steel |
|---|---|
| UNS Designation | S41000 (Grade 6) / S41600 (Grade 6F) |
| Microstructure | Tempered Martensite |
| Magnetic State | Strongly Magnetic (Unlike Grade 8 / 300-Series Stainless) |
| Density | ~7.75 g/cm³ (0.280 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 (Heat Treatment) |
■ Proprietary Datasheet Download (GATED)
Access professional-grade technical data for ASTM A194 Grade 6 & 6F, including high-temperature yield limits, dimensional standards, and mating bolt torque charts.
ASTM A194 Grade 6 / 6F — Complete Technical Datasheet
Contains detailed proof load thresholds up to 135 ksi, dimensional tolerances for ASME B18.2.2 standard and heavy hex profiles, and specific installation torque values for high-temperature A193 B6 assemblies.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
Material traceability is the backbone of safety in high-temperature turbine and piping 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 projects, we facilitate third-party witness testing (e.g., TUV, BV, or SGS) to provide the highest level of material assurance.
■ Chemical Composition
Grade 6 relies on an 11.5% to 13.5% Chromium addition to provide atmospheric and thermal oxidation resistance. Grade 6F significantly bumps the sulfur (or selenium) content to break up chips during CNC machining operations.
| Element | Grade 6 (Type 410) | Grade 6F (Type 416) |
|---|---|---|
| Carbon (C) | 0.15 Max | 0.15 Max |
| Chromium (Cr) | 11.50 – 13.50 | 12.00 – 14.00 |
| Manganese (Mn) | 1.00 Max | 1.25 Max |
| Phosphorus (P) | 0.040 Max | 0.060 Max |
| Sulfur (S) | 0.030 Max | 0.15 Min (for free machining) |
| Silicon (Si) | 1.00 Max | 1.00 Max |
■ Mechanical Properties
Unlike standard 300-series stainless steels that rely on cold working, Grades 6 and 6F achieve their massive proof loads through a strictly monitored quench and temper thermal cycle.
| Mechanical Property | Value Limit (per ASTM A194) |
|---|---|
| Proof Load Stress (Heavy Hex) | 135 ksi (930 MPa) |
| Proof Load Stress (Standard Hex) | 120 ksi (827 MPa) |
| Hardness Range (Rockwell C) | 24 to 38 HRC |
| Hardness Range (Brinell) | 248 to 352 HBW |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASME Standard | SA194 Grade 6 / SA194 Grade 6F |
| Common Trade Name | Type 410 / Type 416 Martensitic Stainless Nuts |
| European Equivalent | EN 10269 / 1.4006 (X12Cr13) |
■ Applications & Industries
Grade 6 is utilized in environments where the strength of carbon steel is required, but the material must survive moderate corrosive attacks, high-temperature oxidation, and thermal cycling.
- Power Generation: Bolting for steam turbine casings, gas turbine exhaust systems, and high-temperature boiler mounts.
- Valve & Pump Manufacturing: Securing valve trim components, high-wear pump housings, and shafts susceptible to galling.
- Petrochemical Processing: Fasteners for thermal cracking units and desulfurization equipment needing mild sulfide/chloride resistance.
- Nuclear Power: Selected secondary cooling loop systems requiring robust, wear-resistant stainless bolting.
■ Compatible Fastener Assemblies
To ensure uniform thermal expansion and galvanic compatibility across the joint, Grade 6 nuts are strictly paired with martensitic stainless steel bolts.
| Nuts (A194 Gr 6 / 6F) | Mating Bolts (A193 Gr B6) | Mating Studs (A193 Gr B6) |
|---|---|---|
| Heavy Hex Nuts | ASTM A193 Grade B6 Heavy Hex Bolts | Fully Threaded Type 410 Studs |
| Standard Hex / Jam Nuts | ASTM A193 Grade B6 Hex Bolts | Double End Studs (Type 410) |
■ 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).
- ASME B1.1: Unified Inch Screw Threads (UNC, UNF, 8UN).
- ASME B1.13M: Metric Screw Threads (M Profile).
■ Torque & Installation Guidelines (Typical B6 / Gr 6 Pairing)
The following torque values are approximate for A193 B6 (Type 410) studs mated with A194 Grade 6 heavy hex nuts. Because martensitic stainless steels are highly prone to thread galling, high-quality, high-temperature anti-seize lubrication is functionally mandatory.
| Nominal Diameter | Threads Per Inch (UNC) | Target Torque — Dry (ft-lbs) | Target Torque — Lubricated (ft-lbs) |
|---|---|---|---|
| 1/2" | 13 | 75 | 55 |
| 5/8" | 11 | 150 | 115 |
| 3/4" | 10 | 260 | 195 |
| 1" | 8 | 630 | 475 |
■ Why Choose Ananka Group?
Ananka Group is a leading manufacturing-driven organization specializing in high-performance stainless bolting packages for the global energy and infrastructure sectors.
- In-House Manufacturing: Complete production control from raw material selection through hot forging, rigorous heat treatment, and precision thread tapping.
- 100% Traceability: Heat numbers are stamped directly on the nuts (alongside the '6' or '6F' mark) for absolute supply chain transparency.
- Custom Machining: Utilizing Grade 6F stock, we can rapidly CNC-machine custom-dimensioned nuts, slotted nuts, and specialized collars.
- Certifications: ISO 9001:2015, ISO 14001:2015, ensuring uncompromising quality management for every fastener leaving our facility.
■ Frequently Asked Questions
1. What is the difference between Grade 6 and Grade 6F?
Grade 6 is made from standard Type 410 martensitic stainless steel. Grade 6F is made from Type 416, a "free-machining" variant that incorporates added sulfur or selenium. The added sulfur allows chips to break off cleanly during heavy CNC machining, though it slightly reduces the material's overall corrosion resistance.
2. Is Grade 6 magnetic?
Yes. Unlike 300-series austenitic stainless steels (such as Grade 8/Type 304), Grade 6 (Type 410) has a martensitic crystalline structure, which makes it strongly magnetic.
3. How does Grade 6 compare to Grade 8 (Type 304) nuts?
Grade 6 boasts significantly higher hardness, proof load strength, and wear resistance due to its ability to be heat-treated. However, Grade 8 provides far superior corrosion resistance in severe chemical and marine environments.
4. What bolts are typically paired with Grade 6 nuts?
To ensure uniform thermal expansion rates in high-temperature systems, Grade 6 nuts are strictly mated with ASTM A193 Grade B6 bolts and studs, which are also manufactured from Type 410 stainless steel.
For project-specific technical support or to request a quote for ASTM A194 Grade 6/6F 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.