Project Description
Alloy 904L, designated UNS N08904 per ASTM and EN 1.4539 / X1NiCrMoCu25-20-5, is a high-alloy austenitic stainless steel with elevated nickel (23–28%), chromium (19–23%), molybdenum (4–5%), and a deliberate copper addition (1–2%). Originally developed by H.S. Company (France), 904L bridges conventional 300-series stainless steels and full super-austenitic grades. Its PREN of approximately 34–37, combined with copper’s unique ability to suppress active dissolution in reducing sulfuric acid, makes it the benchmark CRA for dilute-to-intermediate H₂SO₄, phosphoric acid, and warm seawater service where 316L and 317L fail. At SHUNFU METAL, every heat of 904L is produced via EAF + AOD / VOD refining and undergoes 100% PMI, ultrasonic testing (UT), eddy current inspection (ET), and hydrostatic pressure verification before dispatch.
Equivalent Grades — 904L / N08904
| Grade | UNS | EN / W.Nr. | GB | JIS | ASTM Pipe | PREN |
|---|---|---|---|---|---|---|
| 904L | N08904 | 1.4539 | 015Cr21Ni26Mo5Cu2 | SUS890L | A312 / B677 | ~36 |
| 316L | S31603 | 1.4404 | 022Cr17Ni12Mo2 | SUS316L | A312 | ~25 |
| 317L | S31703 | 1.4438 | 022Cr19Ni13Mo3 | SUS317L | A312 | ~30 |
| Duplex 2205 | S32205 | 1.4462 | 022Cr23Ni5Mo3N | SUS32205 | A790 | ~35 |
| Alloy 926 | N08926 | 1.4529 | 015Cr21Ni26Mo6Cu2N | — | B677 | ~46 |
| 254 SMO | S31254 | 1.4547 | 015Cr20Ni18Mo6CuN | SUS312L | A312 | ~43 |
Oil & Gas Applications — 904L / N08904 CRA Pipe
Acid cooler tubing, absorber recirculation piping, and weak-acid transfer lines in HF and H₂SO₄ alkylation units handling 85–98% acid at elevated temperatures.
Topside injection manifolds, booster pump discharge lines, and subsea water injection flowlines on offshore platforms and FPSO units exposed to warm, oxygenated seawater.
Crude oil desalter effluent piping, produced water treatment pipework, and open-drain caustic/chloride systems on fixed platforms undergoing continuous seawater-induced crevice corrosion.
Gas scrubber inlet/outlet piping, AGR amine-regenerator reboiler tubing, and sour water stripper overhead condensers handling hot H₂S/CO₂-saturated amines per NACE MR0175.
Wet-process evaporator tube bundles, flash cooler piping, and gypsum slurry transfer lines in phosphoric acid plants handling fluoride-contaminated, chloride-bearing 28–54% P₂O₅ acid.
Crude distillation unit overhead condenser tube bundles, naphtha hydrotreater feed-effluent exchanger tubes, and vacuum tower overhead piping handling acidic condensate with chlorides.
Small-bore hydraulic control tubing, methanol injection conduits, and chemical-dosing capillary lines in subsea tree and manifold systems where PREN ≥ 34 suffices and cost containment is essential.
Corrosion inhibitor, demulsifier, and scale inhibitor injection quills and distribution laterals on offshore topsides and subsea well annulus chemical-injection mandrels.
Spray header supply piping, recirculation slurry lines, and mist-eliminator wash water piping in coal-fired power plant FGD units where hot SO₂ condensate coexists with chloride-rich scrubber liquors.
Pipe Supply Range — 904L / N08904
| Product Form | Seamless Pipe, Welded Pipe (ERW / EFW), Capillary Tube, Boiler & Heat-Exchanger Tube, Instrumentation Tube |
| OD Range (Seamless) | 6 mm – 610 mm (1/4″ – 24″) |
| OD Range (Welded) | 16 mm – 914 mm (1/2″ – 36″) |
| Wall Thickness | 0.5 mm – 50 mm (SCH 5S – SCH 160 / XXS) |
| Length | Single Random (up to 6,100 mm), Double Random (up to 12,200 mm), Cut-to-Length |
| End Finish | Plain End (PE), Bevel End (BE), Threaded |
| Surface | Pickled & Passivated, Bright Annealed, 180- / 320- / 400-Grit Polished |
| Standards | ASTM A312 / ASME SA312, ASTM A213, ASTM A249, ASTM A269, ASTM B673, ASTM B677, EN 10216-5, JIS G3459, GB/T 14976 |
| Certification | EN 10204 3.1 / 3.2, PED 2014/68/EU, NACE MR0175 / ISO 15156 |
SHUNFU METAL maintains strategic stock of 904L seamless pipe in 1/2″–12″ diameters with SCH 40S/80S schedules. Large-diameter welded pipe (up to 36″ OD) and heavy-wall sections (> SCH 160) are manufactured to order with short lead times. Every pipe receives 100% hydraulic testing, and all welds undergo full radiography. Mill test certificates per EN 10204 3.1 are standard; 3.2 with third-party witness (TÜV, Bureau Veritas, Lloyd’s Register) is available upon request. NACE MR0175 compliance is verified per heat-lot.
Chemical Composition — 904L / N08904
| Element | Cr | Ni | Mo | Cu | N | Fe | C | Mn | Si | P | S |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Wt % | 19.00–23.00 | 23.00–28.00 | 4.00–5.00 | 1.00–2.00 | ≤0.10 | Bal. | ≤0.020 | ≤2.00 | ≤1.00 | ≤0.045 | ≤0.035 |
Composition per ASTM A312 / B677, UNS N08904. The 904L alloy distinguishes itself through its deliberate copper addition (1.0–2.0%) — a feature absent from conventional 300-series grades. Copper suppresses active dissolution in reducing sulfuric acid environments (0–98% H₂SO₄ up to 40 °C) by elevating the cathodic reaction overpotential, while the 4–5% molybdenum provides the benchmark chloride pitting resistance (PREN ~36). An ultra-low carbon ceiling of 0.020% ensures that chromium carbide precipitation is avoided during welding — the alloy remains free of intergranular attack in the as-welded condition without post-weld heat treatment. The elevated nickel content (23–28%) shifts the austenite stability field, conferring strong chloride SCC immunity. Nitrogen (≤0.10%) retards sigma-phase nucleation during fabrication. At SHUNFU METAL, all melt chemistry is verified by OES and inert gas fusion analysis before production release.
Mechanical Properties — 904L / N08904
Solution-annealed at 1090–1175 °C (2000–2150 °F) followed by rapid water quenching. Data per ASTM A312 / A240 at room temperature.
| Tensile Strength, Rm | ≥ 490 MPa (≥ 71 ksi) |
| Yield Strength, Rp0.2 | ≥ 220 MPa (≥ 31 ksi) |
| Elongation (2 in / 50 mm) | ≥ 35% |
| Hardness (Typical) | ≤ 90 HRB (≤ 200 HBW) |
| Modulus of Elasticity | ~190 GPa (28.0×10⁶ psi) |
| Density | 7.95 g/cm³ (0.287 lb/in³) |
| Melting Range | 1300–1390 °C (2372–2534 °F) |
| Thermal Conductivity | ~12.0 W/m·K at 20 °C |
| Service Temperature | −196 °C to +400 °C |
904L cannot be hardened by heat treatment — it is a fully austenitic solid-solution alloy with stable mechanical properties from cryogenic temperatures to 400 °C. Above 400 °C, the structural stability begins to degrade through sigma-phase precipitation, restricting continuous elevated-temperature service. The alloy is non-magnetic in all conditions (μr ≈ 1.01). SHUNFU METAL applies furnace-chart-controlled solution annealing on every production batch — soak temperature and duration are continuously logged, and a rapid water quench follows to suppress intermetallic precipitation.
904L exhibits excellent weldability by all standard methods (GTAW, GMAW, SMAW, SAW). Due to its ultra-low carbon content (≤0.020%), the alloy resists sensitization in the weld heat-affected zone — post-weld heat treatment is not required for corrosion resistance. Filler metals of matching composition (AWS ERNiCrMo-3 / ERNiCrMo-4) or nickel-base overalloyed fillers are recommended. SHUNFU METAL verifies corrosion resistance of weld zones through ASTM A262 Practice C (intergranular corrosion) and ASTM G48 Method A (pitting) on weld procedure qualification coupons.
Design codes: ASME B31.3 (Process Piping), ASME B31.1 (Power Piping), ASME Section VIII Div. 1 (Pressure Vessels — plate/strip form). For sour service, per-heat NACE MR0175 / ISO 15156 verification to the designated severity level is standard. The alloy is widely accepted across the full concentration range of pure sulfuric acid at ambient temperature (up to 40 °C) and in dilute hydrochloric acid below 2% — making it a workhorse CRA for refinery acid circuits and offshore produced-water systems.