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Sheet · Grade 304 / S30400
304 stainless steel sheet is a chromium-nickel austenitic flat product for formed panels, covers, enclosures and general fabricated equipment. This guide gives the UNS/EN identifiers, sheet chemistry and strength reference, then explains how finish, thickness tolerance, flatness and forming route must be specified for the actual order.
Unsure whether 304 sheet is suitable for a washdown, chloride or forming duty? Share the medium and forming details.
A practical starting grade for indoor equipment, kitchen and food-process equipment, architectural panels, formed housings and general fabrication when the medium is mild to moderately corrosive and cleanability/formability matter. It is a familiar 18% Cr-8% Ni austenitic grade; final suitability still depends on the specific chemistry, temperature and cleaning cycle.
Reassess the grade for warm chloride solutions, seawater or salt spray, stagnant deposits, narrow crevices, aggressive acidic cleaning, or a high-temperature design requirement. Do not infer food-contact compliance or pressure-vessel approval from “304” alone; product condition, finished surface, jurisdiction and the complete equipment design govern.
UNS S30400; EN 1.4301. Verify the ordered product standard and certificate.
The published composition and mechanical values below are a product-data reference for sheet. They are not a guarantee for every thickness, condition or heat.
Published ATI 304 sheet composition by mass (%), shown as a manufacturer product-data example. Chemistry limits differ by product specification and form; check the governing purchase standard and heat certificate. Published ATI 304 sheet data: tensile strength 515 MPa minimum, yield strength 205 MPa minimum, elongation 40% minimum and hardness 92 HRB maximum. Verify exact acceptance requirements for the ordered grade, thickness and standard.
| Element | Minimum | Maximum | Unit |
|---|---|---|---|
| Cr | 17.5 | 19.5 | wt % |
| Ni | 8.0 | 10.5 | wt % |
| Mn | N/A | 2.00 | wt % |
| Si | N/A | 0.75 | wt % |
| N | N/A | 0.10 | wt % |
| C | N/A | 0.07 | wt % |
| P | N/A | 0.045 | wt % |
| S | N/A | 0.030 | wt % |
| Fe | Balance | N/A | wt % |
| Property | Minimum | Maximum / range | Unit | Condition / reference |
|---|---|---|---|---|
| Tensile strength | 515 | N/A | MPa | Sheet; product-specification minimum |
| 0.2% proof / yield strength | 205 | N/A | MPa | Sheet; product-specification minimum |
| Elongation | 40 | N/A | % | Sheet; product-specification minimum |
| Hardness | N/A | 92 | HRB | Sheet; maximum |
| Property | Published value | Basis / note |
|---|---|---|
| Density | 7.9 kg/dm³ | Typical published 304 value at 20°C |
| Elastic modulus | 200 GPa | Typical published 304 value at 20°C |
| Thermal expansion (20–100°C) | 16.0 × 10⁻⁶/K | Typical published 304 value |
| Thermal conductivity | 15 W/(m·K) | Typical published 304 value at 20°C |
| Specific heat capacity | 500 J/(kg·K) | Typical published 304 value at 20°C |
Data note: These values are material-screening references. The governing product specification, ordered condition, dimensions and heat-specific certificate determine acceptance. Review the technical resources for the applicable purchasing basis.
Build the sheet callout from thickness × width × length, quantity, edge/trim condition, flatness, surface finish and delivery condition. Coil-derived cut sheet, hot-rolled sheet and plate are different supply routes; confirm the chosen product form, dimensional tolerance specification and units in the quotation. No stock range or lead time is implied here.
| Duty / item | Starting option | Advantage | Limitation | Alternative / action |
|---|---|---|---|---|
| Flat architectural or equipment panel | 304 sheet, ASTM A240/A240M | Familiar forming, welding and general corrosion performance | Finish, chloride exposure and flatness remain specification-dependent | 304L where welded fabrication benefits from lower carbon |
| Deep-formed cover or enclosure | 304 sheet after forming-trial review | Austenitic sheet can support complex cold-formed parts | Work hardening, springback, tooling and surface protection affect yield | Adjust blank, temper/condition or forming route after trial |
| Warm chloride or retained-deposit zone | Do not default to 304 | Early service review avoids relying on grade name alone | Pitting and crevice attack can occur as chloride severity rises | Review 316L, higher alloy or redesigned drainage with engineer |
Product standard: ASTM A240/A240M covers chromium and chromium-nickel stainless plate, sheet and strip for pressure-vessel and general applications. ASTM A480/A480M supplies general requirements for flat-rolled products, including dimensional and delivery provisions where applicable. Confirm the ordered grade and edition.
Finish and condition: Identify the requested surface finish and side, protective film, surface acceptance criteria and post-fabrication polish/passivation if needed. Finish codes and achievable appearance depend on the supply route; confirm the selected finish on the quote and inspect against an approved sample.
Order checks: confirm exact dimensional basis, tolerance, finish, edge/end preparation, quantity and delivery requirements before quotation.
Send the bend radius, finish, cleaning regime and exposure conditions for an application review.
For a formed cover, panel or process-equipment housing, define blank dimensions, bend radii, grain direction when relevant, joining method and final cleaning. Austenitic 304 can be cold-formed, but work-hardening and springback influence tooling and repeatability. Confirm surface protection and trial criteria before a production run.
| Failure mode | Typical trigger | Control / verification |
|---|---|---|
| Springback or forming cracks | Small bend radius, heavy draw, unfavorable grain direction or excessive work hardening | Confirm condition and thickness; conduct representative forming trial and inspect the formed part |
| Chloride pitting or crevice corrosion | Salt deposits, warm chloride, stagnant liquid, tight lap joints or poor drainage | Document chemistry and temperature; remove crevices or review a more suitable alloy |
| Surface contamination or weld discoloration | Carbon-steel tooling, embedded particles, retained heat tint or poor post-weld cleaning | Segregate tooling, define weld finish and validate cleaning/passivation procedure |
Inspection and acceptance: At receipt, reconcile heat/lot identity and certificate to the purchase order. Inspect thickness, width, length, flatness, edge condition and surface under the agreed sampling plan. Put measurement method, tolerances, finish acceptance, certificate type and any PMI or supplementary test in the order.
Use the product standard for sheet and the applicable general requirements for finish, tolerances and delivery. Verify the edition and any supplementary requirements in the purchase order.
| Standard / designation | Grade designation | Product scope | Procurement caveat |
|---|---|---|---|
| ASTM A240/A240M | 304 | Chromium and chromium-nickel stainless plate, sheet and strip for pressure-vessel and general applications. | Confirm the ordered edition, grade, thickness scope, condition and supplementary requirements. |
| ASTM A480/A480M | General requirements | General requirements for flat-rolled stainless and heat-resisting steel plate, sheet and strip. | Applies where referenced by the product specification; confirm tolerance annex and units in the order. |
State thickness, width and length, quantity, edge condition, flatness/tolerance basis and units. Also name the governing sheet/plate specification and finish, because route and dimensional provisions vary.
304 has good general formability, but its work-hardening and springback affect draw load, tooling and final dimensions. A complex or multi-stage draw should be validated with the selected thickness, condition, blank, lubrication and tooling.
A finish designation identifies a surface route or appearance class, not every acceptance detail. State the finish and side, protective film, roughness or visual criteria if required, and agree how the delivered surface will be inspected.
Not automatically. Concentration, temperature, dwell time, deposits, crevices and rinse effectiveness influence pitting and crevice-corrosion risk. Review the actual cleaning chemistry and compare alloys if exposure is severe.
Match heat/lot identification and certificate to the order, then inspect dimensions, flatness, edge and surface against the agreed sampling and tolerance basis. Any special finish, film, PMI or test must be stated in the purchase order.
Share your sheet dimensions, finish and acceptance plan to build a quote-ready specification.
Example enquiry checklist (not a customer case): 304 sheet; ASTM A240/A240M edition; thickness × width × length; finish code and side; edge/flatness tolerance; forming and weld route; quantity and destination; certificate and inspection requirements.
Record thickness × width × length, grade, ASTM A240/A240M edition, finish, edge and flatness acceptance.
Confirm blank layout, bend radii, grain direction if relevant, joining, surface protection and representative forming trial.
Match heat certificate and lot identity to order; inspect dimensions, finish and edge using the agreed sampling plan.
The data basis is drawn from manufacturer product information and the named sheet purchase standards. The heat-specific certificate and ordered edition govern acceptance.
Published manufacturer sheet values; order-specific cert governs.
Confirm current edition and exact order basis.
Typical grade-level reference, not acceptance values.
A clear sheet enquiry defines the purchased flat product and the fabricated part it must become.
Product-specific review: Confirm commercial availability, minimum order, finish, tolerance and certificate against the current quotation.
