Project Description
UNS N08926, also designated EN 1.4529 and commercially known as Alloy 926 / Incoloy 25-6Mo, is a 6% molybdenum super-austenitic stainless steel engineered for exceptional resistance to chloride pitting, crevice corrosion, and stress corrosion cracking (SCC). With a PREN of approximately 46 — achieved through synergistic additions of Cr 19–21%, Mo 6–7%, and N 0.15–0.25% — Alloy 926 bridges the cost-performance gap between standard austenitics (316L, 317L) and premium nickel alloys (625, C276). At SHUNFU METAL, every heat of Alloy 926 is produced via VIM + ESR dual refining and undergoes 100% PMI, ultrasonic testing (UT), eddy current inspection (ET), and hydrostatic pressure verification before shipment.
Equivalent Grades — Alloy 926 / N08926
| Grade | UNS | EN / W.Nr. | DIN | GB | ASTM Pipe | PREN |
|---|---|---|---|---|---|---|
| Alloy 926 | N08926 | 1.4529 / X1NiCrMoCuN25-20-7 | 1.4529 | 015Cr21Ni26Mo6Cu2N | B677 | ~46 |
| 254 SMO | S31254 | 1.4547 | 1.4547 | 015Cr20Ni18Mo6CuN | A813 | ~43 |
| 904L | N08904 | 1.4539 | 1.4539 | 015Cr21Ni26Mo5Cu2 | B677 | ~36 |
| Alloy 28 | N08028 | 1.4563 | 1.4563 | 00Cr27Ni31Mo4Cu | B668 | ~38 |
| Alloy 31 | N08031 | 1.4562 | 1.4562 | NS1404 | B622 | ~48 |
| Alloy 625 | N06625 | 2.4856 | 2.4856 | NS3306 | B444 | ~50 |
Oil & Gas Applications — Alloy 926 / N08926 CRA Pipe
Headers, distribution manifolds, and risers for seawater injection (SWI) systems on offshore platforms and FPSO units.
Absorber inlet ducting, slurry recirculation lines, and spray nozzle headers in coal-fired power plant FGD systems.
Brine heater tubes, high-pressure RO feed lines, and multi-stage flash (MSF) evaporator piping.
Treatment module pipework and overboard discharge lines on offshore vessels and FPSOs handling full-strength seawater.
Moderate sour service piping under NACE MR0175 Level I–IV, including acid gas removal (AGR) amine contactor and regenerator circuits.
Methanol, corrosion inhibitor, and scale inhibitor injection quill and distribution piping in chloride-rich environments.
Produced water treatment skids and reinjection piping handling hot, high-chloride brine with residual hydrocarbons and CO₂.
Shell-and-tube heat exchanger tubes and shells in crude distillation unit overhead systems where HCl and H₂S condensate forms.
Small-bore control line tubing and umbilical conduits in subsea production systems exposed to seawater at depth.
Pipe Supply Range — Alloy 926 / N08926
| Product Form | Seamless Pipe, Welded Pipe, Capillary Tube |
| OD Range (Seamless) | 6 mm – 219 mm (1/4″ – 8″) |
| OD Range (Welded) | 16 mm – 914 mm (3/8″ – 36″) |
| Wall Thickness | 0.5 mm – 40 mm (SCH 5S – SCH 80S / XXS) |
| Length | Random (5–7 m), Double Random (10–12 m), Cut-to-Length |
| End Finish | Plain End (PE), Bevel End (BE), Threaded |
| Surface | Pickled & Passivated, Bright Annealed, Polished |
| Standards | ASTM B677, ASME SB-677, EN 10216-5, NACE MR0175 / ISO 15156 |
| Certification | EN 10204 3.1 / 3.2, PED 2014/68/EU, API 6ACRA |
SHUNFU METAL maintains Alloy 926 pipe inventory in standard diameters and schedules. Non-standard sizes, heavy wall, and custom lengths are produced to order with short lead times.
Chemical Composition — Alloy 926 / N08926
| Element | Ni | Cr | Mo | Cu | N | Fe | C | Mn | Si | P | S |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Wt % | 24.0–26.0 | 19.0–21.0 | 6.0–7.0 | 0.50–1.50 | 0.15–0.25 | Bal. | ≤0.020 | ≤1.00 | ≤0.50 | ≤0.030 | ≤0.010 |
Composition per ASTM B677 / ASME SB-677. The high Ni content (24–26%) suppresses the austenite-to-martensite transformation and imparts immunity to chloride SCC, a critical advantage over duplex and standard austenitic grades. The deliberate addition of 0.15–0.25% nitrogen provides solid-solution strengthening — raising minimum yield strength to approximately 295 MPa — while simultaneously enhancing pitting resistance (PREN = %Cr + 3.3×%Mo + 16×%N ≈ 46) without compromising weldability. Copper (0.5–1.5%) improves resistance to sulphuric and phosphoric acid. At SHUNFU METAL, every melt is verified by optical emission spectroscopy (OES) and inert gas fusion analysis for nitrogen accuracy.
Mechanical Properties — Alloy 926 / N08926
Solution-annealed at 1120–1180 °C followed by rapid water quenching. Data per ASTM B677 / ASME SB-677 at room temperature unless noted.
| Tensile Strength, Rm | ≥ 650 MPa (94 ksi) |
| Yield Strength, Rp0.2 | ≥ 295 MPa (43 ksi) |
| Elongation (50 mm) | ≥ 35% |
| Hardness (Max) | ≤ 223 HBW / ≤ 96 HRB |
| Modulus of Elasticity | ~200 GPa (29×10⁶ psi) |
| Density | 8.1 g/cm³ (0.293 lb/in³) |
| Melting Range | 1320–1390 °C (2408–2534 °F) |
| Thermal Conductivity | ~12 W/m·K at 20 °C |
| PREN (Calc.) | ~46 |
The solution-annealed + water-quenched condition yields a fully austenitic microstructure free of deleterious sigma or chi phases. SHUNFU METAL performs furnace-chart-controlled annealing on every batch: temperature is logged across the entire soak duration, and hardness testing on each heat-treated lot confirms uniform grain structure per ASTM E112.
For sour service, SHUNFU verifies compliance with NACE MR0175 / ISO 15156 via ASTM A262 Practice C (Huey) and ASTM G48 Method C & D (critical pitting / crevice temperature) testing. PMI is performed on every pipe before dispatch.
Service temperature range: −196 °C to +400 °C in chloride-bearing environments. Welding is performed with matching over-alloyed filler (ERNiCrMo-3 / ENiCrMo-3) to maintain corrosion resistance in the as-welded condition.