904L (UNS N08904 / EN 1.4539) is a superaustenitic stainless-steel bar grade engineered for environments where standard austenitic alloys fail — it combines high nickel, molybdenum and added copper to give markedly improved resistance to reducing acids (sulfuric, phosphoric), crevice/ pitting corrosion, and seawater exposure. For critical chemical, petrochemical and offshore components where longevity and low maintenance matter more than material cost, 904L bar is usually the correct selection; for ordinary stainless applications, 316/316L remains the economical choice.

What is 904L stainless steel bar?

904L is a high-alloy, superaustenitic stainless steel (UNS N08904; EN 1.4539; often called “904L” in commercial trade) designed for elevated corrosion resistance in aggressive media. It contains high nickel and significant molybdenum plus copper; the copper increases resistance to reducing acids (notably sulfuric and phosphoric), while molybdenum and chromium give pitting and crevice resistance. Typical product forms include hot-rolled and cold-drawn round bars, hex and square bars, and bars for machining into shafts, fasteners and pump parts for chemical and offshore duties.

Use cases: chemical processing vessels, heat exchangers, flue-gas cleaning, seawater equipment, pulp & paper bleaching machines, pharmaceutical process equipment, scrubbers and desulfurization plants.

Chemical composition — typical ranges for 904L bar (wt%)

Below is an industry-standard composition table assembled from mill datasheets and material references. Individual mill/heat certificates may vary inside these ranges; always request an MTC (mill test certificate) with chemical analysis for critical orders.

Note: Low carbon control (≤0.02%) and absence of stabilizers (Ti/Nb) are common to permit welded constructions without strong sensitisation issues.

Material properties — mechanical and physical

Interpretation: 904L has mechanical strengths similar to other austenitic grades in the annealed state but with much enhanced resistance to specific corrosive agents because of Mo and Cu content.

Standards, specifications and supply grades

Common standards and procurement specifications that cover 904L bar and wrought forms:

• UNS designation: N08904 (commonly used in material certificates).

• European / EN: 1.4539 (X1NiCrMoCu25-20-5).

• Common ASTM / ASME specifications for bars & shapes: ASTM A276 / A479 (bars and shapes) and ASME SA-479; for plates/sheets reference ASTM A240 / ASME SA-240. If specifying pressure-vessel tubing use appropriate ASTM/ASME tube specs (e.g., A269/A789/A790 where applicable).

Procurement tip: When ordering bar stock for pressure-containing or critical parts, specify the standard (e.g., “904L, UNS N08904, ASTM A479 / EN 1.4539, annealed”), required test certificates (EN 10204 3.1 or 3.2), and requested heat treatment and surface finish.

Typical bar forms, tolerances and sizes

Manufacturers and stockists commonly supply 904L in these forms:

• Round bright bars: cold-drawn (precision) and hot-rolled (bright or black).

• Hex & square bars: for fastening and machining stock.

• Flat bars & billets: for forging and heavy machining.

• Cut lengths, sawed, centreless ground, or polished depending on final use.

Common diameter / cross-section ranges (industry practice):

• Round: 3.0 mm up to 200 mm (typical stock up to 100 mm).

• Hex/square: according to standard stock ranges (5 mm–100 mm).

Specification table (example calling out common tolerances and standards):

Bar weight per metre — practical table

Calculation basis: circular cross-section weight = (π/4) × d² × ρ; used density = 7,980 kg/m³ (rounded industry figure; supplier datasheets typically cite 7.95–8.05 g/cm³).

These figures are for quick estimating; for tendering and final costing always use supplier-certified sizes and densities on the MTC.

What is 904L equivalent to?

Common technical equivalents and near-equivalents used in specifications:

• UNS: N08904 (direct).

• EN: 1.4539 (X1NiCrMoCu25-20-5).

• Mill trade names / proprietary: Some mills label very similar superaustenitic grades with brand names (e.g., Alleima® 2RK65, Outokumpu Ultra 904L / Ultra range). For interchangeability, review full chemical and mechanical certificates; small differences in Ni, Mo or Cu may affect corrosion performance.

Caution: Don’t substitute without evaluation. Duplex or other superaustenitic grades (6XN, 825, ALLOY 625) may have overlapping strengths but different cracking, weldability and corrosion profiles.

Which is better: 904L or 316L?

Short answer: Depends on environment and budget. 316L is economical and excellent for many marine and mild chemical environments. 904L is the superior choice when the service includes strong reducing acids (sulfuric, concentrated phosphoric), chloride-containing brines at elevated temperatures, or when long service life with minimal maintenance is paramount.

Head-to-head (key differences)

Recommendation: choose 316L for general service and cost-sensitive projects; specify 904L for aggressive chemical exposure or where lifecycle cost (replacement + downtime) dominates.

Machining, welding and fabrication notes

• Machining: 904L machines like other high-nickel austenitics but demands slower feeds and sharp tooling because of work-hardening tendency. Use generous coolant and carbide tooling for production runs.

• Welding: Low carbon minimizes sensitisation; common welding processes (TIG, MIG/Flux-cored) work well. Use matching filler metals (e.g., 904L filler or recommended superaustenitic weld consumables) for maximum corrosion performance. Preheat is usually unnecessary; post-weld anneal rarely required but follow project spec.

• Heat treatment: Solution anneal followed by rapid quench is the usual mill process; further normalisation is unusual for bar stock. Avoid temperatures that promote sigma phase formation in extended high-temperature service.

• Cold forming: Good ductility enables bending and forming, but springback and work hardening must be managed.

Corrosion behavior — environments where 904L excels

Strengths:

• Excellent resistance to reducing acids (sulfuric, phosphoric).

• Improved pitting and crevice resistance in chloride environments compared with 316/316L.

• Good performance in seawater cooling equipment up to moderate temperatures (consult design limits).

Limitations & considerations:

• Not universally immune — highly oxidizing media at elevated temperatures may still attack; evaluate with corrosion testing for critical services.

• Chloride stress-corrosion cracking (SCC) resistance is better than 316L but not unlimited; design to minimize crevices and ensure adequate flow/chemistry control.

904l stainless steel bar price 2025 — USA / Europe / China

Market pricing for 904L is highly volatile and driven by nickel and molybdenum markets, alloy surcharges, order quantity, form (bar vs plate), certification and freight. The table below presents indicative ranges (FOB / mill or distributor bulk buy levels) observed in mid-2025 sources. Use these only for high-level budgeting; obtain firm quotes for procurement.

How to read this: European mill-direct and regional distributors typically show tighter ranges; Chinese FOB listings may appear very low for mill-direct hot-rolled stock but exclude testing, QC, and export logistics. For critical parts insist on an MTC and 3.1/3.2 certificates and price the landed, inspected cost.

(Sources include independent alloy price writeups and supplier listings; market conditions (surcharges and nickel/Mo prices) changed frequently through 2025 — verify at quoting stage).

How MWAlloys supplies 904L bar

MWAlloys is a specialized supplier of high-performance stainless and nickel alloys. For customers buying 904L bar we offer:

• Factory-direct pricing: mill relationships allow direct pricing that avoids multiple distributor mark-ups — 100% factory direct pricing on many standard sizes for stock items.

• Stock & fast delivery: common round and hex sizes kept in bonded inventory for rapid shipment; custom cuts and finish work handled in our facility.

• QA & certificates: EN 10204 3.1 / 3.2 mill test certificates, chemical & mechanical analysis, PMI checks available on request.

• Value services: machining to drawing, centerless grinding, cold-drawn precision bars and specialist packing for export.

Procurement & inspection checklist

• Specify full material designation (e.g., 904L / UNS N08904 / EN 1.4539).

• Ask for mill heat number and EN 10204 3.1/3.2 certificate.

• Confirm product form (hot-rolled bright, cold-drawn, polished) and final dimensional tolerances.

• State required mechanical properties (yield, tensile) and testing (UT/UT/eddy for critical parts).

• Require PMI/optical emission report for traceability on first shipments.

• Specify surface finish and packaging for overseas transport.

FAQs

1. Is 904L magnetic?
   Generally non-magnetic in the annealed condition, but cold work can induce slight magnetic response.

2. Can I weld 904L to 316L?
   Yes, but the joint will not have uniform corrosion resistance; use suitable fillers and consider galvanic and corrosion performance of the weld area.

3. Is 904L heat-treatable for higher strength?
   904L is austenitic and is not hardened by normal heat treatment; strength adjustments are achieved by cold work.

4. Does 904L resist sulphuric acid?
   It performs significantly better than 316L in reducing acids (including many concentrations of sulfuric acid) — still validate with corrosion testing for concentration/temperature.

5. What are typical lead times?
   For stocked sizes from a mill/distributor: days–weeks. For custom or certificated orders: several weeks. MWAlloys offers fast shipment for stocked items.

6. What certifications are typical?
   EN 10204 3.1 / 3.2 mill test certificates; compliance with ASTM/ASME specs on request.

7. Is 904L suitable for marine fasteners?
   It can be used where seawater corrosion resistance is required, but cost may dictate alternatives; evaluate designs for crevice corrosion.

8. How does machining cost compare with 316L?
   Machining cost is higher: tooling, cycle time and consumables increase because of higher alloy content and work-hardening behaviour.

9. What inspection should I demand on arrival?
   Verify MTC, visual check, dimensional check, and spot PMI or chemical verification for critical orders.

10. Are there lower-cost alternatives with similar corrosion properties?
    Some superaustenitic or duplex grades (e.g., 6XN, 2507 duplex) may offer comparable or superior localized corrosion resistance for certain applications — selection depends on chloride, temperature and mechanical requirements.

Practical selection summary

Choose 904L bar when corrosion risk (reducing acids, chloride crevices, seawater) and long service life justify the alloy premium. For many applications where chloride exposure is moderate and operating costs and material budget are critical, 316L remains the appropriate choice. For seawater and heavy chloride environments at higher temperatures, investigate superaustenitic grades (904L, 6XN) and duplex alloys for the optimum lifecycle cost.