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Help Center904L Ferritic Steel Sheet Plate | 1.5mm | No.4 Brushed | Appliance
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904L Stainless Steel Sheet (1.5mm, No.4 Brushed): A Technical Buyer's Guide
904L stainless steel sheet occupies a specific and demanding niche in the stainless family. When a 1.5mm sheet is finished to a No.4 brushed surface and specified for appliance or process-equipment use, buyers are usually weighing three things at once: corrosion performance in aggressive media, a controlled decorative-yet-hygienic surface, and predictable fabrication behavior. This guide explains what 904L actually is, why the grade is chosen over more common alternatives such as 316L, and how the 1.5mm gauge and No.4 finish influence real-world use.
What Is 904L Stainless Steel?
904L (UNS N08904, EN 1.4539) is a high-alloy austenitic stainless steel — not a ferritic grade. It is often described as a "super-austenitic" or "high-performance" stainless steel because its nickel, molybdenum, and copper content sit well above standard 300-series grades. The high nickel content stabilizes the austenite phase, giving the material its characteristic combination of toughness, formability, and non-magnetic behavior, while molybdenum and copper drive its resistance to reducing acids and chloride attack.
The low carbon ceiling (≤ 0.020%) is deliberate. It suppresses the precipitation of chromium carbides at grain boundaries during welding, which is what protects the heat-affected zone from intergranular corrosion. This is why 904L is a preferred sheet material for welded appliance housings, tanks, and process panels where post-weld corrosion is a concern.
Typical Chemical Composition
| Element | Symbol | Content (%) |
|---|---|---|
| Carbon | C | ≤ 0.020 |
| Silicon | Si | ≤ 1.00 |
| Manganese | Mn | ≤ 2.00 |
| Phosphorus | P | ≤ 0.030 |
| Sulfur | S | ≤ 0.010 |
| Chromium | Cr | 19.0 – 23.0 |
| Nickel | Ni | 23.0 – 28.0 |
| Molybdenum | Mo | 4.0 – 5.0 |
| Copper | Cu | 1.0 – 2.0 |
| Nitrogen | N | ≤ 0.10 |
The combination of high molybdenum and added copper is the defining feature. Copper specifically improves resistance to sulfuric and phosphoric acid, which is why 904L was originally developed for handling dilute sulfuric acid environments where 316L is inadequate.
Mechanical and Physical Properties
For a 1.5mm cold-rolled sheet in the annealed condition, 904L delivers the moderate strength and high ductility typical of austenitic stainless steels. The high elongation is what makes the grade friendly to deep drawing, bending, and roll forming — relevant when the sheet is destined for appliance panels or curved enclosures.
| Property | Value (Annealed, typical) |
|---|---|
| Tensile strength (Rm) | ≥ 490 MPa (71 ksi) |
| Yield strength (Rp0.2) | ≥ 220 MPa (32 ksi) |
| Elongation (A50) | ≥ 35% |
| Hardness | ≤ 90 HRB |
| Density | 7.95 g/cm³ |
| Modulus of elasticity | ~190 GPa |
| Thermal conductivity (20°C) | ~11.5 W/m·K |
| Coefficient of thermal expansion (0–100°C) | ~15.0 × 10⁻⁶ /K |
| Melting range | ~1300 – 1390°C |
| Magnetic response | Non-magnetic (austenitic) |
Because 904L is fully austenitic, a 1.5mm sheet will read as essentially non-magnetic in the annealed state — a practical way to distinguish it from ferritic grades on the shop floor, which are strongly magnetic.
Corrosion Resistance: Where 904L Earns Its Cost
The main reason to pay the premium for 904L is corrosion performance. Its resistance is best summarized by the Pitting Resistance Equivalent Number (PREN), calculated as %Cr + 3.3 × %Mo + 16 × %N. For 904L this typically lands around 34–36, placing it well above 316L and roughly on par with 2205 duplex for pitting resistance.
| Grade | Approx. PREN | Relative chloride pitting resistance |
|---|---|---|
| 304 / 304L | ~18 | Baseline |
| 316 / 316L | ~24 | Moderate |
| 904L (1.4539) | ~35 | High |
| 2205 Duplex | ~35 | High |
904L performs strongly in three failure modes that concern equipment designers:
Pitting and crevice corrosion in chloride-bearing environments, including brackish water, cleaning chemistries, and coastal atmospheres.
Stress corrosion cracking (SCC), where the high nickel content gives markedly better resistance than 316L in hot chloride conditions.
Uniform corrosion in reducing acids, particularly sulfuric and phosphoric acid, thanks to the molybdenum-copper combination.
For appliances that contact hard water, detergents, disinfectants, food acids, or salt-laden air, this translates into a longer service life and a lower risk of surface staining or perforation over time.
Understanding the 1.5mm Gauge
The 1.5mm thickness is a common structural-yet-formable gauge for sheet metal work. It is thick enough to provide rigidity for panels, doors, and enclosure walls without heavy reinforcement, yet thin enough to be sheared, laser cut, bent, and press-formed on standard equipment. In appliance manufacturing, 1.5mm strikes a balance between weight, dent resistance, and cost per square meter.
| Gauge context | Typical use |
|---|---|
| 0.5 – 1.0mm | Light panels, trim, splashbacks |
| 1.5mm | Structural panels, doors, enclosures, tanks |
| 2.0 – 3.0mm | Load-bearing frames, heavy process vessels |
At 1.5mm, cut edges and weld seams remain manageable, and the sheet retains enough stiffness to hold a flat No.4 finish without visible oil-canning when properly supported.
The No.4 Brushed Finish Explained
A No.4 finish is a directional, satin brushed surface produced by mechanical abrasion. It is the workhorse architectural and appliance finish because it hides fingerprints and minor scratches far better than a bright polish while remaining easy to clean and hygienic.
| Finish attribute | Specification |
|---|---|
| Finish designation | No.4 (satin / brushed) |
| Abrasive grit | ~120 – 180 grit |
| Surface roughness (Ra) | 0.5 – 1.0 μm |
| Grain direction | Unidirectional (linear) |
| Typical use | Appliances, kitchens, elevators, panels |
The controlled Ra range matters for hygiene-sensitive applications. A smoother, consistent brushed surface reduces sites where contaminants can lodge, supporting cleanability in food-contact and appliance environments. The unidirectional grain also gives finished products a uniform, professional appearance when panels are aligned in the same direction.
Why Choose 904L for Appliances?
Most appliances are built from 304 or 430, so specifying 904L signals a deliberate performance requirement. It becomes the right choice when the appliance operates in, or contacts, environments that would over-tax cheaper grades:
Commercial and industrial appliances exposed to aggressive cleaning agents, chlorinated sanitizers, or salt.
Coastal or high-humidity installations where atmospheric chlorides cause tea-staining on 304.
Process and laboratory equipment contacting acids or chemical solutions.
High-longevity or premium products where warranty exposure justifies a corrosion-resistant substrate.
In these cases, the higher raw-material cost is offset by reduced maintenance, fewer warranty claims, and a longer functional and cosmetic lifespan.
Fabrication Guidance
904L behaves like a highly alloyed austenitic stainless steel during fabrication, which brings both advantages and a few points of caution.
Forming. High elongation supports deep drawing and bending, but the grade work-hardens. Forming operations may require higher press forces and, for complex parts, intermediate annealing. Generous bend radii reduce the risk of surface cracking.
Welding. 904L is readily weldable by TIG (GTAW), MIG (GMAW), and other common processes. Matching or over-alloyed filler metals (such as 904L or nickel-based fillers like Alloy 625) are used to maintain corrosion resistance in the weld. Because the base metal is low-carbon and stabilized against sensitization, the heat-affected zone retains good corrosion performance when heat input is controlled.
Cutting. Laser, plasma, waterjet, and shearing all work at 1.5mm. Waterjet is preferred when a heat-affected zone must be avoided entirely.
Cleaning and passivation. Post-fabrication pickling and passivation restore the passive chromium-oxide film disturbed by welding and grinding, which is essential to achieving the grade's full corrosion potential.
904L vs Common Alternatives
| Criterion | 316L | 904L (1.4539) | 2205 Duplex |
|---|---|---|---|
| Structure | Austenitic | Austenitic | Ferritic-austenitic |
| Molybdenum | 2 – 3% | 4 – 5% | ~3% |
| Nickel | 10 – 14% | 23 – 28% | 4.5 – 6.5% |
| Sulfuric acid resistance | Limited | High | Moderate |
| Chloride SCC resistance | Moderate | Good | Excellent |
| Strength | Moderate | Moderate | High |
| Relative cost | Lower | Higher | Moderate–High |
The decision usually comes down to the specific chemistry. Where reducing acids (sulfuric, phosphoric) dominate, 904L is typically the stronger performer. Where mechanical strength and hot-chloride SCC resistance are the priorities, 2205 duplex may be preferred. 316L remains the value choice for milder conditions.
Standards and Quality Assurance
Reputable 904L sheet is supplied against recognized international standards, which buyers should confirm on the mill test certificate (MTC / EN 10204 3.1):
ASTM A240 / A240M and ASME SA-240 — plate, sheet, and strip for pressure vessels and general applications.
EN 10088-2 — technical delivery conditions for corrosion-resisting steel sheet and strip.
UNS N08904 / EN 1.4539 — grade designations.
A complete quality package typically includes chemical composition analysis, mechanical test results, verification of the No.4 finish and Ra range, thickness tolerance to the relevant flatness standard, and traceability by heat number. Requesting the MTC before purchase confirms that the delivered material matches the specification.
Frequently Asked Questions
Is 904L magnetic?No. As a fully austenitic grade, 904L sheet is essentially non-magnetic in the annealed condition, unlike ferritic stainless steels.
Is 904L better than 316L?For corrosion resistance in chloride and reducing-acid environments, yes — its higher molybdenum, nickel, and copper content give it a meaningfully higher PREN. For milder service, 316L is often adequate and more economical.
Can 904L sheet be welded?Yes. It is readily weldable with matching 904L or nickel-based fillers, and its low carbon content protects the weld zone from sensitization when heat input is controlled.
What does the No.4 finish mean?It is a directional brushed satin finish produced with roughly 120–180 grit abrasives, giving a surface roughness (Ra) of about 0.5–1.0 μm — the standard appliance and architectural finish.
Is 1.5mm suitable for structural panels?Yes. At 1.5mm the sheet offers panel rigidity and dent resistance while remaining easy to cut, bend, and form on standard equipment.
Wuxi Zhongxin Special Steel Co., Ltd. – One-Stop Global Special Steel Export Service Provider
Wuxi Zhongxin Special Steel Co., Ltd. – One-Stop Global Special Steel Export Service Provider
Wuxi Zhongxin Special Steel Co., Ltd. is located in Xishan District, Wuxi City, nestled in the core special steel distribution hub of the Yangtze River Delta. Benefiting from a complete steel industrial chain and convenient marine logistics with easy access to Shanghai and Ningbo ports, we are an integrated special steel foreign trade enterprise integrating direct mill procurement, spot inventory storage, precision metal processing, and global steel import & export. We hold full self-operated import and export qualifications, and provide one-stop supporting solutions of full-range steel products and non-ferrous metals for global industrial purchasers and overseas engineering projects.
With years of experience in steel export, we have established long-term strategic cooperation as authorized distributors with leading domestic steel manufacturers including TISCO, Baosteel, JISCO and Dongfang Special Steel. All goods are supplied directly from original factories with stable supply, and manufactured in strict compliance with international standards such as ASTM, ASME, EN, DIN, JIS and GB to meet customs clearance and engineering inspection requirements worldwide.
Full Range of Main Export Steel Products
1. Stainless Steel Series: Hot-rolled & cold-rolled stainless steel sheets, coils and strips in grades 304/316L/321/2205 duplex steel; BA bright seamless pipes, EP electrolytic polished seamless pipes, industrial welded pipes; stainless steel round bars, angle steels, flanges and pipe fittings. Custom surface finishes including 8K mirror polishing, wire drawing, matte finishing and embossing are available.
2. Carbon Steel & Seamless Pipe Series: ASTM A106 Gr.B seamless carbon steel pipes in SCH40/SCH80, API 5L oil & gas casings, hot/cold rolled carbon steel sheets & coils, medium plates, checkered plates, round bars, H-beams, channel steels and angle steels for construction engineering.
3. Electrical Silicon Steel Series: Grain-oriented & non-oriented silicon steel sheets and coils, ultra-thin silicon steel specially for transformers, suitable for export orders of motors, transformers and new energy electrical equipment.
4. Coated Anti-Corrosion Steel: Hot-dip galvanized sheets & coils, color coated steel and weathering steel, widely used in overseas factory buildings, photovoltaic power stations and steel structure infrastructure projects.
5. Special Alloys & Non-Ferrous Metals: Nickel-based alloys, copper and aluminum sheets, pipes and bars to satisfy supporting demands of high-end chemical and new energy industries.
Supporting Precision Export Processing Capacity
We own a 10,000-square-meter-level warehousing and processing center equipped with imported laser cutting machines, waterjet cutting equipment, high-precision slitting & leveling lines and CNC polishing production lines. We provide one-stop deep processing services including pipe beveling, plate cutting, bending and mirror polishing to fixed lengths. All delivered goods can be supplied with EN 10204 3.1 Material Test Certificates, SGS/BV third-party inspection reports, together with hydrostatic testing, non-destructive testing and full heat number traceability documents.
Core Advantages of Foreign Trade Export
1. Mass Spot Inventory: Thousands of tons of conventional specifications are kept in stock for quick order arrangement of standard 4m/6m/12m fixed-length pipes and various sheets & coils. Special steel grades and non-standard sizes can be scheduled directly from steel mills, supporting both small-batch inquiries and bulk supply for large engineering projects.
2. Mature Global Sales Network: Our professional multilingual foreign trade team exports products to over 40 countries covering the Middle East, Southeast Asia, Europe, Africa, South America and Australia, serving customers from petrochemical, pressure vessel, photovoltaic new energy, food & pharmaceutical, electric power, overseas infrastructure, engineering machinery and other sectors.
3. One-Stop Quotation under All Trade Terms: We offer complete quotations on FOB China port, CFR and CIF overseas destination port basis, supporting full container load and less-than-container load shipments. We can issue certificates of origin, inspection certificates and a full set of customs clearance documents, and track marine logistics throughout the whole process.
4. Standardized Seaworthy Export Packaging: Steel pipes are fitted with plastic end caps, bundled with steel straps and wrapped in waterproof films; steel sheets are covered with anti-rust films. Each bundle is clearly marked with specification, wall thickness, material grade, heat number and country of origin to realize anti-rust protection during long-distance ocean transportation.
5. Transparent & Comprehensive Commercial Services: Quotation validity period, payment terms, loading/unloading fees, inspection charges, bank commissions and other extra costs are fully listed without hidden charges. Our technical team provides 24-hour online support for material selection, standard interpretation and delivery schedule follow-up, along with long-term after-sales guarantee.
Upholding the business philosophy of Quality First, Sincerity for Win-Win, Global-Oriented Service, we strive to be your long-term trusted partner for special steel export with a complete product portfolio, stable original factory supply, professional processing supporting capacity and mature foreign trade delivery system.
Q1：Can I get a sample before placing a large order?
A：Absolutely. We offer free samples for existing stock items, but the shipping cost will be at your side. The sample fee will be fully deducted from your first bulk order.
Q2：Is there a minimum order quantity?
A：We are flexible. While our MOQ is typically 1 ton per size, we welcome trial orders as low as 200 kg for first-time cooperation. Mixed sizes in one container are also acceptable.
Q3：Do you offer cutting or machining services?
A：Yes. We provide precision cutting, slitting, edge milling, and drilling per your technical drawings. Tolerances can be controlled within ±0.05mm if required.
Q4：What quality documents do you supply?
A：We supply full traceability documents including EN 10204 3.1 certificates, heat analysis, and mechanical property reports. Independent lab test reports are also available upon request at extra cost.
Q5：How fast can you ship?
A：For standard items, we can dispatch within 5–10 days. For made-to-order products, production usually takes 15–25 days. Urgent orders can be expedited with prior notice.
Q6：What finishes do you support?
A：We offer a wide range of finishes: 2B, BA, No.4, mirror, pickled, sandblasted, powder-coated, and oiled. Just tell us your end-use, and we’ll recommend the best option.
Q7：What are your payment methods?
A：We accept T/T, L/C, D/P, and flexible terms like 30% deposit + 70% before shipment or against BL copy. For regular clients, we can also discuss credit terms.
Q8：How do you pack products for ocean freight?
A：All products are packed in sturdy wooden crates or steel-framed bundles with waterproof wrapping, edge protectors, and export-standard fumigation. Custom branding and labeling are also available.
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