Product Description
Alloy 31 (Nicrofer 3127 hMo) is an advanced iron-nickel-chromium-molybdenum super-austenitic stainless steel with nitrogen additions. This high-performance alloy closes the gap between high-alloyed austenitic special stainless steels and nickel alloys, providing exceptional corrosion resistance in aggressive environments. Alloy 31 typically contains 30-32% nickel, 26-28% chromium, 6-7% molybdenum, and 0.15-0.25% nitrogen, creating a stable austenitic structure with outstanding performance characteristics.
The material’s well-balanced chemical composition delivers outstanding corrosion resistance in alkaline and acidic halide-containing media, excellent resistance to sulfuric acid (even in highly concentrated form), and superb resistance to corrosion and erosion in phosphoric acid media. Additionally, Alloy 31 offers excellent resistance in both reducing and oxidizing media as well as in boiling azeotropic nitric acid, making it an ideal choice for critical applications in harsh chemical environments.
The alloy’s high nitrogen content (0.15-0.25%) stabilizes the austenite and reduces the precipitation rate of intermetallic sigma phases, enhancing its structural stability in service. Alloy 31 is characterized by good workability and weldability, allowing for efficient fabrication of complex components.
Applications
Alloy 31 (Nicrofer 3127 hMo) is designed for applications requiring exceptional corrosion resistance in aggressive environments across various industries:
- Chemical Processing Industry: Components for handling sulfuric acids contaminated with chlorides, pickling plants for sulfuric acid and nitric-hydrofluoric acid, treatment of waste sulfuric acids, organic acids and ester synthesis, fine chemicals production
- Phosphoric Acid Production: Plants for the production of phosphoric acid via the wet digestion process, offering superior resistance to erosion-corrosion
- Environmental Engineering: Components for flue gas desulfurization plants, treatment of contaminated acids
- Marine Applications: Pipes containing ocean water and brackish water, condensers, chillers, and marine scrubbers for ship diesel engines
- Pulp and Paper Industry: Chlorine dioxide bleaching plants, providing outstanding resistance to surface corrosion and local corrosion
- Oil and Gas Industry: Mineral oil production and refineries, strain-hardened transport and feed pipes, slicklines, wirelines, and flowlines for oil and gas transport
- Mining Industry: Digestion of ores, including HIPAL (High-Pressure Acid Leach) plants for the digestion of laterite ores
- Salt Processing: Equipment for evaporation and crystallization of salts
The alloy’s versatility makes it suitable for numerous critical applications where standard materials would fail due to corrosive attack, particularly in environments containing halides (chlorides, fluorides) in combination with acids at elevated temperatures.
Standards
Alloy 31 (Nicrofer 3127 hMo) is covered by the following standards and specifications:
European Standards:
- Material designation according to DIN: 1.4562 – X1NiCrMoCu32-28-7
- VdTÜV Material Data Sheet 509 (for pressure vessels with operating temperatures from -196 to 550°C)
- SEW 400 (Stahl-Eisen-Werkstoffblatt)
American Standards:
- UNS N08031
- ASTM B625 (Plate, Sheet, and Strip)
- ASTM B581, B649 (Rod and Bar)
- ASTM B649 (Wire)
- ASTM B564 (Forgings)
- ASME SB625, SB581, SB649 (for pressure vessel applications)
- ASME approval for pressure vessels up to 800°F (427°C)
International Standards:
- ISO 15156/NACE MR0175:2003 (Certification for acid gas applications in the oil and gas industry up to level VI)
- API 5LD (for strip products)
The material is also included in the list of the German Federal Institute for Materials Research and Testing (BAM) for transport and storage containers for hazardous goods.
Material Designation and Chemical Composition
Alloy 31 is known under the following designations:
| Standard | Designation |
|---|---|
| UNS | N08031 |
| DIN | 1.4562 – X1NiCrMoCu32-28-7 |
| Common Trade Name | Alloy 31, Nicrofer 3127 hMo |
The chemical composition of Alloy 31 according to UNS N08031 specification is as follows:
| Element | Minimum (%) | Maximum (%) |
|---|---|---|
| Nickel (Ni) | 30.0 | 32.0 |
| Chromium (Cr) | 26.0 | 28.0 |
| Iron (Fe) | Balance | Balance |
| Molybdenum (Mo) | 6.0 | 7.0 |
| Copper (Cu) | 1.0 | 1.4 |
| Nitrogen (N) | 0.15 | 0.25 |
| Carbon (C) | – | 0.015 |
| Silicon (Si) | – | 0.3 |
| Manganese (Mn) | – | 2.0 |
| Phosphorus (P) | – | 0.020 |
| Sulfur (S) | – | 0.010 |
Physical and Mechanical Properties
Alloy 31 offers an exceptional combination of high strength and excellent corrosion resistance. The following physical and mechanical properties apply to the material in the solution-annealed and quenched condition:
Physical Properties:
| Property | Value |
|---|---|
| Density at 20°C (68°F) | 8.05 g/cm³ (0.29 lb/in³) |
| Melting Range | 1,330-1,370°C (2,426-2,498°F) |
| Relative Magnetic Permeability at 20°C (68°F) | 1.001 |
| Thermal Conductivity at 20°C (68°F) | 11.7 W/(m·K) or 81.2 Btu·in/(sq.ft·h·°F) |
| Electrical Resistivity at 20°C (68°F) | 104 μΩ·cm |
| Modulus of Elasticity at 20°C (68°F) | 198 GPa (28.7 × 10³ ksi) |
| Coefficient of Thermal Expansion (20-100°C) | 14.3 × 10⁻⁶/K (7.94 × 10⁻⁶/°F) |
Mechanical Properties at Room Temperature:
| Property | Value (Metric) | Value (Imperial) |
|---|---|---|
| 0.2% Yield Strength (Rp0.2) | ≥ 280 MPa | ≥ 40.6 ksi |
| 1.0% Yield Strength (Rp1.0) | ≥ 310 MPa | ≥ 45.0 ksi |
| Tensile Strength (Rm) | ≥ 650 MPa | ≥ 94.3 ksi |
| Elongation (A) | ≥ 40% | ≥ 40% |
| ISO V-notch Impact Toughness (average value) | ≥ 185 J/cm² | – |
| ISO V-notch Impact Toughness at -196°C (-320.8°F) | ≥ 140 J/cm² | – |
Heat Treatment
To achieve optimal properties, Alloy 31 should undergo solution annealing at temperatures between 1,150 and 1,180°C (2,102 and 2,156°F). The retention time during annealing depends on the semi-finished product thickness:
- For thickness d ≤ 10 mm (0.39 in): retention time t = d × 3 min/mm
- For thickness d = 10 to 20 mm (0.39-0.79 in): retention time t = 30 min + (d – 10 mm) × 2 min/mm
- For thickness d > 20 mm (0.79 in): retention time t = 50 min + (d – 20 mm) × 1 min/mm
For maximum corrosion resistance, workpieces must be quickly cooled from the annealing temperature of at least 1,100°C (2,012°F) to 500°C (932°F) with a cooling rate of >150°C/min (>302°F/min).
Corrosion Resistance
Alloy 31 offers exceptional corrosion resistance in various environments:
- Outstanding resistance to pitting and crevice corrosion in chloride-containing environments
- Excellent resistance to sulfuric acid across a broad range of concentrations and temperatures up to 80°C (176°F)
- Superior resistance to erosion-corrosion in phosphoric acid production
- Excellent performance in chlorine dioxide bleaching plants in the pulp and paper industry
- High resistance to intergranular corrosion, with critical pitting temperatures significantly higher than conventional austenitic stainless steels
Note: The material has limited resistance to hydrochloric acid, with suitable applications only where HCl occurs in low concentrations (below 5%) at room temperature or slightly elevated temperatures.
Available Dimensions
FUSHUN METAL provides Alloy 31 in a wide range of product forms and dimensions:
Sheet and Plate:
| Condition | Thickness | Width | Length |
|---|---|---|---|
| Cold-rolled | 1-10 mm (0.04-0.39 in) | Up to 3,000 mm (118.11 in) | Up to 13,000 mm (511.81 in) |
| Hot-rolled | 3-100 mm (0.12-3.94 in) | Up to 3,000 mm (118.11 in) | Up to 13,000 mm (511.81 in) |
Strip:
| Thickness | Width | Coil – Inside Diameter |
|---|---|---|
| 0.02-3 mm (0.0008-0.12 in) | 4-800 mm (0.16-31.5 in) | 300-600 mm |
Rod and Bar:
| Outside Diameter | Length |
|---|---|
| 6-800 mm (0.24-31.5 in) | 1,500-12,000 mm (59.06-472.44 in) |
Wire:
| Drawn | Hot-rolled |
|---|---|
| 0.16-12 mm (0.006-0.47 in) | 5.5-25 mm (0.22-0.98 in) |
Custom dimensions and forms are available upon request to meet specific application requirements.
Fabrication Information
Alloy 31 can be readily fabricated using conventional methods, with some specific considerations for optimal results:
Hot and Cold Forming
Hot forming should be performed in the temperature range of 1,200 to 1,050°C (2,192 to 1,922°F) with subsequent rapid cooling in water or air. For cold forming, the material should be in the annealed condition, with intermediate annealing necessary for major cold forming work. Any cold forming exceeding 15% requires final solution annealing.
Welding
Alloy 31 can be welded using conventional processes such as GTAW (TIG), GMAW (MIG/MAG), and plasma welding. Welding should be performed using the stringer bead technique with low heat input. The interpass temperature should not exceed 120°C (248°F). Suitable filler metals include those matching the Alloy 31 composition or nickel-based alloys with similar or higher alloying content.
Machining
The alloy should be machined in the heat-treated condition. Due to its increased work hardening rate compared to conventional austenitic stainless steels, machining should be performed with lower cutting speeds, adequate depth of cut to penetrate below the work-hardened layer, and sufficient cooling.
Descaling and Pickling
Oxides on Alloy 31 are more adherent than on standard stainless steels. Grinding with fine abrasive belts or discs is recommended before pickling. Oxide layers should be destroyed by abrasive blasting or fine grinding before pickling in nitric-hydrofluoric acid mixtures.
Why Choose FUSHUN METAL for Alloy 31
When selecting a supplier for high-performance Alloy 31 (Nicrofer 3127 hMo) products, FUSHUN METAL stands as your premier choice for several compelling reasons:
- Superior Material Quality: At FUSHUN METAL, we ensure all our Alloy 31 products meet the strictest international standards and specifications, providing materials with consistent chemical composition and mechanical properties for reliable performance in demanding applications.
- Comprehensive Product Range: We offer Alloy 31 in a complete range of forms including sheet, plate, strip, rod, bar, and wire – all available in various dimensions to suit your specific project requirements.
- Technical Expertise: Our metallurgical specialists possess extensive knowledge of super-austenitic stainless steels and can provide valuable guidance on material selection, fabrication considerations, and corrosion resistance for your particular operating environment.
- Quality Assurance: Every Alloy 31 product from FUSHUN METAL undergoes rigorous testing and inspection to ensure compliance with international standards and your specific requirements, with full material certification provided.
- Global Supply Capabilities: With our extensive production capacity and logistics network, we can deliver Alloy 31 products to customers worldwide with competitive lead times, supporting your project schedules effectively.
- Custom Solutions: Beyond standard offerings, we can provide custom-sized products, specialized processing, and technical support tailored to your unique application challenges.
For your next project requiring the exceptional corrosion resistance of Alloy 31 in aggressive chemical processing, marine, or oil and gas environments, we invite you to contact our team with your specifications and requirements. Our technical experts are ready to assist you in selecting the optimal material configuration for your application, ensuring long-term performance and reliability in even the most demanding conditions.
