⚡ Quick Specs: Alloy 926
What Is Alloy 926?
Alloy 926 — also known as 6Mo super-austenitic, UNS N08926, or DIN W.Nr. 1.4529 — is a fully austenitic stainless steel engineered for the most demanding chloride, seawater, and process-industry environments. Its chemistry combines roughly 20% chromium, 25% nickel, 6.5% molybdenum, copper, and nitrogen, producing a Pitting Resistance Equivalent Number (PREN) above 43. That single number places Alloy 926 in the elite tier of corrosion-resistant materials, well above 904L, 254 SMO competitors, and 316L.
Where 316L stainless steel routinely suffers pitting, crevice corrosion, and chloride stress-corrosion cracking within months of seawater service, Alloy 926 remains passive year after year. As a long-established Alloy 926 supplier and manufacturer, Hangbo Alloy Group supplies the grade in all standard product forms to offshore, desalination, FGD, chemical, and pulp & paper customers worldwide.
Chemical Composition
The nominal chemical composition of Alloy 926 per ASTM B649 / EN 10088 is shown below. All values are in weight percent (wt%).
| Element | Content (wt%) |
|---|---|
| C | ≤ 0.020 |
| Si | ≤ 0.50 |
| Mn | ≤ 2.00 |
| P | ≤ 0.030 |
| S | ≤ 0.010 |
| Cr | 19.0 – 21.0 |
| Ni | 24.0 – 26.0 |
| Mo | 6.0 – 7.0 |
| Cu | 0.5 – 1.5 |
| N | 0.15 – 0.25 |
| Fe | Balance |
The 6.0–7.0% molybdenum content — roughly 2.5× the Mo in 316L — is the single most important contributor to Alloy 926's chloride resistance. The deliberate 0.15–0.25% nitrogen addition further raises the PREN, stabilizes the austenite phase, and significantly increases yield strength compared to non-nitrogen-bearing grades.
Physical Properties
| Property | Value |
|---|---|
| Density | 8.1 g/cm³ (0.293 lb/in³) |
| Melting Range | 1320 – 1390 °C (2408 – 2534 °F) |
| Specific Heat (20 °C) | ~ 500 J/kg·K |
| Thermal Conductivity (20 °C) | ~ 12.5 W/m·K |
| Electrical Resistivity (20 °C) | ~ 0.85 µΩ·m |
| Young's Modulus | ~ 195 GPa |
| Magnetic Permeability | ~ 1.01 (fully non-magnetic) |
| Mean CTE (20–200 °C) | ~ 15.0 × 10⁻⁶ /K |
Mechanical Properties (Room Temperature, Solution Annealed)
| Property | Value |
|---|---|
| Tensile Strength (Rm) | ≥ 650 MPa (94 ksi) |
| Yield Strength (Rp0.2) | ≥ 295 MPa (43 ksi) |
| Elongation (A%) | ≥ 35% |
| Hardness | ≤ 250 HB |
| Impact Toughness (Charpy V, 20 °C) | ≥ 100 J |
| Condition | Solution Annealed (1150–1200 °C, water quenched) |
The nitrogen addition lifts yield strength by roughly 30% over a non-nitrogenated 6Mo grade, allowing thinner wall sections in pressure equipment without compromising corrosion performance.
Seawater & Chloride Corrosion Resistance
Alloy 926 was designed to solve the chronic failure of 316L and even 904L in warm seawater, chlorinated cooling water, and chloride-bearing process streams. The combined Cr + Mo + N chemistry produces a self-healing passive film that resists pitting, crevice attack, and chloride stress-corrosion cracking far beyond the limits of standard austenitic grades.
- Pitting Resistance: PREN ≥ 43 (Cr + 3.3·Mo + 16·N). 316L has PREN ~24; 904L has PREN ~34. In ASTM G48 Method A testing at 50 °C, Alloy 926 typically shows no pitting at 24 h exposure, while 316L fails in hours.
- Crevice Corrosion: Far superior to 6Mo super-duplex 2507 in stagnant seawater and crevice geometries (e.g., flange faces, gasketed joints). Critical Critical Design Temperature (CCT) for 926 is around 30–35 °C, vs ~5–10 °C for 316L.
- Stress Corrosion Cracking: Immune to chloride SCC up to ~120 °C in concentrated chloride brines, owing to the high nickel content (25%) and stable austenitic structure.
- Seawer General Corrosion: Typical corrosion rate < 0.01 mm/yr in natural seawater, vs 0.10–0.30 mm/yr for 316L.
- Sour Service (H₂S): Qualified under NACE MR0175 / ISO 15156 for use in sour oil & gas environments up to a defined partial pressure of H₂S.
High-Temperature Behavior
Alloy 926 is principally a corrosion-resistant grade for ambient-to-moderate service. It is suitable for continuous exposure up to about 400 °C (752 °F). Above 450 °C the risk of sigma-phase and chi-phase precipitation rises sharply, which embrittles the alloy and reduces impact toughness and corrosion performance. For applications above 500 °C, switch to high-nickel superalloys such as Alloy 625 (Inconel 625) or Alloy 825 (Incoloy 825).
Applications
Alloy 926 is the workhorse material where 316L fails and full nickel alloys are over-specified. The combination of high PREN, full austenitic structure, and excellent weldability has made it the standard for seawater systems and chloride-rich process service worldwide.
| Application Area | Typical Components & Notes |
|---|---|
| Seawater Systems | Seawater cooling piping, plate heat exchangers, condensers, firewater mains, ballast lines — the canonical use of 6Mo grades |
| Offshore Oil & Gas | Topsides cooling, subsea manifolds, produced-water piping, water injection systems |
| Desalination | Multi-stage flash (MSF), multi-effect distillation (MED), and reverse osmosis (RO) plant tubing and high-pressure piping |
| FGD Scrubbers | Coal-fired power plant flue-gas desulfurization absorber towers, outlet ducting, and stack liners handling chloride-laden slurries |
| Chemical Processing | Sulfuric acid coolers, phosphoric acid evaporators, acetic acid equipment, chlorinated organic plants |
| Pulp & Paper | Bleach plant washers, filtrate tanks, and piping handling ClO₂ and chlorination stages |
| Marine Hardware | Pump shafts, propeller hubs, valve stems, instrument fittings, naval seawater systems |
| Pharmaceutical & Food | Process piping, reactors, and heat exchangers where chloride cleaning chemicals (e.g., NaCl brine) are routine |
Available Product Forms
| Product Form | Typical Dimensions |
|---|---|
| Round Bars (ASTM B649 / A276) | φ 6 – φ 350 mm, hot-rolled, cold-drawn, forged |
| Plates & Sheets (ASTM A240) | Thickness 0.5 – 80 mm, width up to 2500 mm |
| Seamless Pipe & Tube (ASTM A312 / A269) | OD 6 – 273 mm, WT 0.5 – 25 mm |
| Welded Pipe (ASTM A312) | OD 10 – 1219 mm, WT 1.0 – 20 mm |
| Fittings (ASTM A403) | Elbows, tees, reducers, caps — butt-weld & socket-weld |
| Flanges (ASTM A182 / B649) | WN, SO, BL, TH — ASME B16.5 / B16.47 |
| Forgings (ASTM A182) | Rings, discs, shafts, custom shapes |
| Welding Consumables | ERNiCrMo-3 (Inconel 625) and matching ER2594 super-duplex |
Related Standards & Specifications
| Standard | Product Scope |
|---|---|
| ASTM A240 / ASME SA-240 | Plate, sheet & strip |
| ASTM A276 / A479 | Bar & shapes |
| ASTM A312 / A358 | Seamless & welded pipe |
| ASTM A249 / A269 / A270 | Seamless & welded tube |
| ASTM A403 | Wrought fittings |
| ASTM A182 | Forged flanges, fittings, valves |
| ASTM B649 | Ni-Fe-Cr-Mo-Cu-N rod, bar & wire (UNS N08926) |
| EN 10028-7 / EN 10088 | European pressure-vessel plate and bar standards |
| NACE MR0175 / ISO 15156 | Sour service in oil & gas |
| DIN / W.Nr. | 1.4529 |
Frequently Asked Questions (FAQ)
1. What is Alloy 926?
Alloy 926 (UNS N08926 / W.Nr. 1.4529) is a 6% molybdenum super-austenitic stainless steel. Its chemistry of roughly 20% Cr, 25% Ni, 6.5% Mo, plus copper and nitrogen gives it a Pitting Resistance Equivalent Number (PREN) above 43, making it the workhorse material for seawater piping, heat exchangers, and offshore process equipment. As a leading Alloy 926 manufacturer and supplier, Hangbo Alloy Group supplies the grade in bar, plate, tube, pipe, fittings, and forgings.
2. What is the chemical composition of Alloy 926?
Nominal Alloy 926 composition (wt%): C ≤0.020, Si ≤0.50, Mn ≤2.00, P ≤0.030, S ≤0.010, Cr 19.0–21.0, Ni 24.0–26.0, Mo 6.0–7.0, Cu 0.5–1.5, N 0.15–0.25, Fe balance. The combination of high Cr, high Mo, and nitrogen produces the high PREN that defines the 6Mo super-austenitic family.
3. What is the density and melting point of Alloy 926?
Alloy 926 has a density of approximately 8.1 g/cm³ (0.293 lb/in³) and a melting range of about 1320–1390 °C (2408–2534 °F). Its density is comparable to standard 300-series austenitic stainless steels.
4. What are the mechanical properties of Alloy 926?
Solution-annealed mechanical properties (typical): tensile strength ≥650 MPa (94 ksi), 0.2% yield strength ≥295 MPa (43 ksi), elongation ≥35%, hardness ≤250 HB. The alloy is fully austenitic and non-magnetic even after severe cold work.
5. How does Alloy 926 compare to 316L stainless steel?
Alloy 926 contains roughly 2.5× more Mo (6.5% vs 2.5%) and 25% Ni (vs 10–12% in 316L), giving a PREN above 43 vs 24 for 316L. In seawater and chloride-rich environments 316L suffers pitting and crevice corrosion, while Alloy 926 remains passive. 926 is the practical upgrade when 904L and even 6Mo variants are challenged.
6. What is the maximum service temperature of Alloy 926?
Alloy 926 is designed for ambient to moderate temperatures and is used continuously up to about 400 °C (752 °F). Above 450 °C, microstructural changes (sigma phase precipitation) reduce toughness and corrosion resistance, so 926 is not recommended for high-temperature structural service — super-austenitic alloys such as 254 SMO or nickel-rich alloys like Alloy 625 are preferred above 500 °C.
7. Is Alloy 926 resistant to seawater corrosion?
Yes — seawater resistance is the defining property of Alloy 926. It is highly resistant to pitting, crevice corrosion, and stress corrosion cracking in natural seawater, chlorinated seawater, and brine. It is widely used for seawater-cooled heat exchangers, firewater piping, ballast lines, and offshore platform process piping where 316L fails within months.
8. Can Alloy 926 be welded?
Yes. Alloy 926 is readily welded by GTAW (TIG), GMAW (MIG), and SMAW. Recommended fillers are AWS A5.14 ERNiCrMo-3 (Inconel 625) for highest corrosion performance, or AWS A5.9 ER2594 (matching 6Mo super-duplex) for seawater lines. No preheat is required, interpass temperature should be kept below 150 °C, and post-weld heat treatment is not normally needed.
9. What standards apply to Alloy 926?
Alloy 926 is produced under ASTM A240 (plate/sheet), ASTM A276/A479 (bar), ASTM A312 (seamless & welded pipe), ASTM A249/A269 (tube), ASTM A403 (fittings), ASTM B649 (rod/bar), EN 10028-7, EN 10088, and the corresponding ASME SA equivalents for pressure equipment. It also appears in NACE MR0175 for sour service.
10. What are the typical applications of Alloy 926?
Primary applications: (1) Seawater systems — piping, heat exchangers, condensers, firewater mains; (2) Offshore oil & gas — process piping, subsea manifolds, topside cooling; (3) FGD scrubbers in coal-fired power plants; (4) Chemical processing — sulfuric, phosphoric, and acetic acid service; (5) Pulp & paper — bleach plant equipment; (6) Desalination — MSF, MED, and RO plants; (7) Marine shaft seals, pump shafts, and propeller hubs.
11. What is the price and lead time for Alloy 926?
Alloy 926 is a premium 6Mo grade priced roughly 4–6× standard 316L. Indicative pricing: bars $25–40/kg, plates $30–45/kg, seamless tubes $50–90/kg, welded pipes $40–70/kg. Lead time is typically 6–12 weeks depending on size and mill schedule. Hangbo Alloy Group maintains stock of common dimensions for fast shipment. MOQ: 100 kg for stock items, 500 kg for custom specs. Contact hangbo@nickel-alloy.com for a quote.
12. How does Alloy 926 compare to super-duplex 2507?
Alloy 926 is a fully austenitic 6Mo stainless with a PREN above 43, while 2507 is a super-duplex with PREN around 42–43. 926 is fully austenitic and remains non-magnetic, with better formability, weldability, and resistance to chloride SCC at moderate temperatures. 2507 has roughly 2× the yield strength, lower nickel cost, and slightly better chloride pitting resistance at room temperature. For thick-wall or high-pressure offshore piping, 2507 is often preferred; for complex fabrications and broad chemical compatibility, 926 is the safer choice.
Need Alloy 926 for Your Seawater or Chemical Project?
Hangbo Alloy Group is a trusted global manufacturer and supplier of Alloy 926 (UNS N08926 / 1.4529) in bars, plates, tubes, pipes, fittings, and forgings. Mill test certificates to EN 10204 3.1, full traceability, and competitive pricing on every order.