Hangbo Alloy Group
Shanghai · Est. 2012
UNS N06059 / W.Nr. 2.4605 — Nickel-chromium-molybdenum alloy with outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking. The highest PREN value among Ni-Cr-Mo alloys.
Alloy 59 (UNS N06059 / W.Nr. 2.4605) is a nickel-chromium-molybdenum alloy developed by VDM Metals as the ultimate evolution of the Ni-Cr-Mo "C-family" of corrosion-resistant alloys. It represents a significant advancement over Alloy C-276 and Alloy C-22, with the highest PREN (Pitting Resistance Equivalent Number) value among all nickel-chromium-molybdenum alloys, typically exceeding 76. Alloy 59 was designed specifically to eliminate the microstructural limitations of earlier C-type alloys while maximizing resistance to both oxidizing and reducing corrosive media.
The alloy achieves its exceptional corrosion resistance through a carefully balanced composition: high chromium (23%) for oxidizing resistance, high molybdenum (16%) for reducing resistance, and extremely low carbon and silicon content to minimize grain boundary precipitates and maintain thermal stability. Unlike earlier Ni-Cr-Mo alloys, Alloy 59 has a single-phase austenitic microstructure that remains stable during welding and thermal processing, eliminating the risk of intergranular corrosion in the as-welded condition.
This combination of properties makes Alloy 59 the material of choice for the most demanding chemical processing environments, including hot sulfuric acid, hydrochloric acid, mixed acid systems, chlorine dioxide bleach plants, and flue gas desulfurization (FGD) systems. It is also widely used in pharmaceutical production, pollution control equipment, and offshore oil and gas applications where resistance to sour gas environments is critical.
The chemical composition of Alloy 59 is precisely engineered to achieve the highest possible corrosion resistance in both oxidizing and reducing environments. The high chromium content (23%) provides passivation in oxidizing acids, while the high molybdenum content (16%) delivers resistance to reducing conditions. The extremely low carbon and silicon levels prevent the formation of detrimental grain boundary precipitates during welding and heat treatment, ensuring the alloy remains corrosion-resistant in the as-welded condition without requiring post-weld solution annealing.
| Element | Min % | Max % |
|---|---|---|
| Nickel (Ni) | Balance | Balance |
| Chromium (Cr) | 22.0 | 24.0 |
| Molybdenum (Mo) | 15.0 | 16.5 |
| Iron (Fe) | — | 1.5 |
| Aluminum (Al) | 0.10 | 0.40 |
| Manganese (Mn) | — | 0.50 |
| Silicon (Si) | — | 0.10 |
| Carbon (C) | — | 0.010 |
| Copper (Cu) | — | 0.50 |
| Phosphorus (P) | — | 0.015 |
| Sulfur (S) | — | 0.010 |
| Cobalt (Co) | — | 0.30 |
Alloy 59 possesses a fully austenitic face-centered cubic (FCC) crystal structure that remains stable across the entire range of operating temperatures. This single-phase structure is critical for maintaining uniform corrosion resistance, as it eliminates the risk of intermetallic phase precipitation that plagues earlier C-type alloys. The alloy's physical properties contribute to excellent fabricability, including good weldability and formability comparable to austenitic stainless steels.
| Property | Value | Unit |
|---|---|---|
| Density | 8.60 | g/cm3 |
| Melting Range | 1310–1360 | °C |
| Specific Heat (20°C) | 414 | J/kg·K |
| Thermal Conductivity (20°C) | 10.2 | W/m·K |
| Electrical Resistivity (20°C) | 1.26 | μΩ·m |
| Modulus of Elasticity (20°C) | 210 | GPa |
| Mean Coefficient of Thermal Expansion (20–100°C) | 12.1 | μm/m·°C |
| Thermal Diffusivity (20°C) | 2.8 × 10-6 | m2/s |
Alloy 59 is supplied in the solution-annealed condition and offers a good combination of strength and ductility. The mechanical properties below represent minimum values for solution-annealed material per ASTM B575 (plate) and ASTM B622 (seamless pipe). The alloy's ductility and toughness are excellent, with Charpy impact values exceeding 200 J at room temperature.
| Property | Value |
|---|---|
| Tensile Strength (Rm) | 690 MPa (100 ksi) |
| Yield Strength, 0.2% offset (Rp0.2) | 340 MPa (49 ksi) |
| Elongation in 50 mm | 40% |
| Reduction of Area | 55% |
| Hardness (Rockwell B) | 88–95 HRB |
| Impact Strength (Charpy V-notch, 20°C) | >200 J |
| Shear Modulus | 79 GPa |
| Poisson's Ratio | 0.31 |
While Alloy 59 is primarily used for its corrosion resistance rather than high-temperature strength, it retains good mechanical properties at moderately elevated temperatures. The alloy is suitable for continuous service up to approximately 450°C (840°F) in corrosive environments. Above this temperature, long-term exposure may lead to microstructural changes that could affect corrosion resistance, though short-term excursions to higher temperatures are acceptable.
| Temperature (°C) | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| 20 (Room) | 690 | 340 | 40 |
| 100 | 640 | 300 | 42 |
| 200 | 590 | 270 | 43 |
| 300 | 555 | 250 | 44 |
| 400 | 530 | 235 | 46 |
| 500 | 505 | 225 | 48 |
Alloy 59 represents the pinnacle of corrosion resistance in the Ni-Cr-Mo alloy family. Its balanced composition of 23% Cr and 16% Mo, combined with extremely low impurity levels, provides outstanding resistance to virtually all forms of corrosive attack. The alloy's critical pitting temperature (CPT) in oxidizing chloride environments exceeds 120°C, and its critical crevice corrosion temperature (CCT) exceeds 85°C in 6% FeCl3 per ASTM G48 Method D.
Alloy 59 is readily weldable using all common arc welding processes, including GTAW (TIG), GMAW (MIG), SMAW (stick), and SAW (submerged arc). The alloy's low carbon and silicon content eliminates the need for post-weld heat treatment to restore corrosion resistance — a significant advantage over earlier C-type alloys like C-276 which require solution annealing after welding to prevent intergranular attack.
Recommended welding consumables include ERNiCrMo-13 (AWS A5.14) for filler wire and ENiCrMo-13 for covered electrodes. The weld metal matches the base metal corrosion resistance. Hot working is performed at 1200–950°C with final solution annealing at 1100–1180°C followed by rapid water quenching or air cooling depending on section thickness.
Alloy 59 is the preferred material for the most aggressive chemical processing environments where standard stainless steels and even other nickel alloys fail. Its unique combination of properties enables it to handle conditions that would rapidly destroy competing materials:
Hangbo Alloy Group manufactures and supplies Alloy 59 in the following product forms, conforming to ASTM, ASME, and VDM specifications:
| Standard | Description |
|---|---|
| ASTM B575 | Plate, Sheet, and Strip |
| ASTM B574 | Bar and Rod |
| ASTM B622 | Seamless Pipe and Tube |
| ASTM B619/B626 | Welded Pipe and Tube |
| ASTM B564 | Forgings |
| ASTM B366 | Fittings |
| AWS A5.14 | Welding Wire (ERNiCrMo-13) |
| ASME SB-575 | Boiler and Pressure Vessel Code — Plate |
| NACE MR0175 | Sour Service (H2S) Compliance |
| VDM Nicrofer 5923 | Proprietary Grade Designation |
Hangbo Alloy Group maintains inventory of Alloy 59 in all standard product forms and sizes. We can provide mill test certificates (MTC) per EN 10204 3.1, third-party inspection reports (SGS, TUV, Lloyd's Register), and custom processing services including cutting, machining, and surface finishing.
For quotations, material certifications, or technical consultation on Alloy 59 for your application, contact our technical sales team or call +86-136-1165-6360. We typically respond within 10 minutes during business hours.
Request a quotation for Alloy 59 round bars, tubes, plates, or forgings. We stock standard sizes and accept custom orders with mill certification.