304 stainless steel plate and 304L stainless steel plate are chromium-nickel austenitic stainless steel flat products. They are supplied as plate, sheet and coil for tanks, process equipment, heat-exchanger components, fabricated panels and other formed or welded parts. Chromium forms a passive surface film that provides corrosion resistance, while nickel helps maintain the austenitic structure and fabrication performance.
Grade 304 corresponds to UNS S30400, while 304L corresponds to UNS S30403. The main difference is carbon content. Therefore, 304L is often selected for welded fabrication where resistance to sensitization and intergranular corrosion is important.
OCTAL Metals supplies 304/304L stainless steel plate, 304 stainless steel sheet and 304 stainless steel coil in project-specified dimensions and surface conditions. ASTM A240 and ASME SA240 are common specification references for these flat-rolled stainless steel products.
304/304L Stainless Steel Plate Supply Range
304 and 304L material can be supplied in plate, sheet and coil forms. The required form depends on thickness, surface finish and downstream fabrication. Plate is normally selected for heavier fabricated components, while sheet and coil are used for thinner formed parts and continuous processing.
| Supply Item | Available Range |
|---|---|
| Grades | 304 / 304L |
| Standards | ASTM A240 / ASME SA240 |
| Product Forms | Plate, sheet and coil |
| Thickness | 0.02–4 mm; 4.5–100 mm |
| Width | 900–2400 mm |
| Plate Length | 3000–12000 mm |
| Surface Conditions | Natural, 2B, mirror |
| Processing | Laser cutting, waterjet cutting and plasma cutting |
An ASTM A240 304 stainless steel plate order should therefore identify not only the grade and nominal dimensions, but also the required surface condition, processing method and inspection documentation.
304 vs 304L Stainless Steel Plate
304 and 304L belong to the same chromium-nickel austenitic stainless steel family. Their general forming, welding and corrosion characteristics are similar. However, the lower carbon limit of 304L creates an important difference during welded fabrication.
Welding heat can promote chromium-carbide precipitation in susceptible conditions. As a result, chromium near the grain boundaries may become locally depleted. 304L reduces this risk because of its lower carbon content. Therefore, it is often used for welded tanks, fabricated equipment and other assemblies where sensitization control is required.
This does not mean that 304L is automatically required for every project. Grade selection still depends on section thickness, welding exposure, service environment and the governing specification.
| Selection Item | 304 | 304L |
|---|---|---|
| UNS Designation | S30400 | S30403 |
| Material Family | Austenitic Cr-Ni stainless steel | Low-carbon austenitic Cr-Ni stainless steel |
| Carbon Control | Standard 304 composition limit | Lower carbon limit |
| Main Selection Consideration | General fabrication, forming and corrosion service | Welded fabrication where sensitization control is more important |
| Product Forms | Plate, sheet and coil | Plate, sheet and coil |
304 and 304L Stainless Steel Plate and Sheet Type
Chemical Composition and Mechanical Properties
304 and 304L use the same chromium-nickel austenitic alloy system. However, 304L has a lower carbon limit. This difference is especially important where welding creates a heat-affected zone.
The following tables show the main chemical composition and mechanical-property values for 304 and 304L. These values allow grade identification and preliminary material comparison before fabrication.
| Elements (%) | 304 (S30400) | 304L (S30403) |
|---|---|---|
| Carbon, Max | 0.07 | 0.030 |
| Manganese, Max | 2.00 | 2.00 |
| Phosphorus, Max | 0.045 | 0.045 |
| Sulphur, Max | 0.030 | 0.030 |
| Silicon, Max | 0.75 | 0.75 |
| Chromium | 17.5–19.5 | 17.5–19.5 |
| Nickel | 8.0–10.5 | 8.0–12.0 |
| Nitrogen, Max | 0.10 | 0.10 |
The lower carbon limit is the main composition difference between the two grades for welded fabrication. By contrast, the chromium and nickel ranges remain broadly similar.
Mechanical Properties
| Mechanical Property | 304 (S30400) | 304L (S30403) |
|---|---|---|
| Tensile Strength, Min | 75 ksi (515 MPa) | 70 ksi (485 MPa) |
| Yield Strength, Min, 0.2% Offset | 30 ksi (205 MPa) | 25 ksi (170 MPa) |
| Yield Strength, Min, 1% Offset | 36 ksi (250 MPa) | 35 ksi (240 MPa) |
| Elongation, Min | 40% | 40% |
| Hardness, Max | 92 HRB | 92 HRB |
304 Stainless Steel Plate, Sheet and Coil Forms
The required stainless steel product form depends mainly on thickness, dimensional format, surface condition and the downstream fabrication process. 304 stainless steel plate is generally selected for thicker fabricated parts, equipment sections and cut components where flat plate geometry is required. 304 stainless steel sheet is used for thinner formed, bent or surface-finished components, while 304 stainless steel coil supports continuous processing, slitting and repeated sheet production.
Surface finish should be specified separately from grade. A 304 material designation identifies the alloy, but it does not define the final surface condition. Natural or mill-finished material may be suitable for general fabrication, while 2B or polished surfaces may be required where appearance, cleanability or downstream processing controls the finished component.
Stainless Steel Coil Type
Corrosion Resistance and Service Limits of 304/304L Stainless Steel
The corrosion resistance of 304 and 304L comes mainly from the chromium-rich passive film on the steel surface. This thin oxide layer separates the base metal from the surrounding environment. In suitable oxidizing conditions, the film can also reform after minor surface damage.
However, corrosion resistance is not unlimited. Temperature, chloride concentration, chemical composition, deposits, crevices and surface contamination can all change material performance. Therefore, the actual service environment must be considered before grade selection.
General Corrosion Behavior
304/304L performs well in many atmospheric and mildly to moderately corrosive environments. For this reason, it is widely used in fabricated equipment, tanks, panels and general process components.
Still, uniform corrosion is only one possible failure mode. Local conditions at welds, deposits, gaskets or stagnant zones can be more severe than conditions on an open plate surface. These locations should therefore be considered separately.
Pitting, Crevice Corrosion and Chlorides
Chlorides are an important service limitation for 304/304L. They can locally damage the passive film and initiate pitting corrosion. In addition, narrow gaps under deposits, gaskets or fasteners can promote crevice corrosion.
The risk increases as chloride concentration and temperature rise. Stagnant liquid and unfavorable geometry can further increase the local exposure. Therefore, 304 should not be selected only because it is generally described as corrosion resistant.
Welded Areas and Intergranular Corrosion
The lower carbon content of 304L reduces chromium-carbide precipitation during welding. As a result, the heat-affected area is less susceptible to chromium depletion at grain boundaries.
This is the main corrosion-related reason for selecting 304L stainless steel plate instead of standard 304 in many welded structures. However, the lower carbon content does not make 304L significantly more resistant to chloride pitting. These are different corrosion mechanisms and should not be confused.
Elevated-Temperature Service
Oxidation at elevated temperature differs from aqueous corrosion. Surface oxidation depends on temperature, atmosphere, exposure time and thermal cycling.
Prolonged thermal exposure can also affect sensitization behavior. Therefore, high-temperature material selection should consider both oxidation resistance and metallurgical stability rather than using one general maximum-temperature statement for every service condition.
When to Consider 316/316L Instead of 304/304L
304/304L is suitable for many general fabrication and mildly corrosive environments. However, another stainless grade may be required when chloride exposure becomes a controlling condition.
316/316L contains molybdenum, which improves resistance to pitting and crevice corrosion in certain chloride-containing environments. Therefore, the change from 304/304L to 316/316L should be based on service chemistry rather than on an assumption that 316 is simply a higher-grade stainless steel.
Important selection inputs include chloride concentration, operating temperature, cleaning chemicals, stagnant zones and crevice geometry. Weld condition should also be reviewed. For welded fabrication, the same carbon-content distinction applies between 316 and 316L.
316 stainless steel plate
For prolonged elevated-temperature service where sensitization resistance and high-temperature strength become design requirements, stabilized grades such as 321/321H may be considered instead of standard 304/304L.
Processing, Forming and Welding of 304/304L Stainless Steel
304/304L can be processed by cutting, bending, forming and welding. However, the fabrication route affects edge condition, work hardening, distortion and final surface quality. Processing should therefore be matched to thickness and finished-part requirements.
Cutting and Edge Preparation
Laser cutting is suitable for many sheet and thinner plate components where accurate profiles are required. Plasma cutting can be used for heavier sections, while waterjet cutting avoids a thermally affected cut edge.
Thermal cutting may leave oxide or heat tint near the edge. Therefore, additional edge preparation may be required before welding or corrosion-sensitive service. Stainless surfaces should also be protected from embedded carbon-steel particles during grinding and handling.
Cold Forming and Work Hardening
304/304L has good ductility and can be bent, rolled and formed. However, austenitic stainless steel work-hardens as deformation increases.
As a result, forming loads and springback can increase during severe bending or drawing. Tool condition and forming sequence should therefore control local strain rather than concentrating deformation in one area.
Heat Treatment
304 and 304L are not hardened by conventional quench-and-temper heat treatment. Instead, their strength can increase through cold working.
Solution annealing may be used where the fabrication route requires restoration of the austenitic condition after substantial thermal or mechanical processing. Aging treatment, however, is not a normal strengthening treatment for 304/304L.
Welding
304 and 304L can be welded using common stainless-steel welding processes. Joint preparation, filler selection, heat input and welding sequence depend on thickness and fabrication requirements.
Austenitic stainless steel also has relatively high thermal expansion. Therefore, welding sequence and restraint need to be controlled to reduce distortion. 304L is especially useful where welded sections require lower sensitization risk.
Post-weld annealing is not normally required for many standard 304/304L fabrications. However, heat tint and surface oxide may need to be removed where corrosion performance of the finished surface is important.
Weight of 304 Stainless Steel Plate
Plate weight is required when calculating material quantity, transportation load, lifting requirements and quotation weight. The theoretical weight of rectangular 304 stainless steel plate can be calculated from the plate dimensions and the material density.
A practical calculation using a nominal density factor of 7.93 is:
Plate Weight (kg) = Length (m) × Width (m) × Thickness (mm) × 7.93
304 and 304L austenitic stainless steels have a reference density of approximately 7.9 kg/dm³, with small differences possible depending on the exact chemical composition and reference used.
Weight Calculation Example
For a 304 stainless steel plate measuring 2,000 mm × 1,000 mm × 5 mm:
| Calculation Item | Value |
|---|---|
| Length | 2.0 m |
| Width | 1.0 m |
| Thickness | 5 mm |
| Density Factor | 7.93 |
| Theoretical Weight | 79.3 kg |
2.0 × 1.0 × 5 × 7.93 = 79.3 kg
The calculated value is a theoretical weight used for material planning and quotation. Actual shipment weight can vary slightly because of permissible thickness tolerance, dimensional tolerance, edge processing and the actual composition of the supplied material.
Applications of 304/304L Stainless Steel Plate and Sheet
Food-Processing and Fabricated Equipment
304 stainless steel sheet is used for fabricated panels, enclosures, work surfaces and equipment components where corrosion resistance, cleanable surfaces and forming capability are required. Surface finish, joint design and cleaning exposure should be confirmed according to the finished equipment rather than inferred from grade alone.
Tanks and General Process Equipment
304/304L plate can be fabricated into tanks, covers, supports and process-equipment components operating in environments compatible with the alloy. Where welded fabrication is extensive, 304L may be selected to reduce sensitization risk associated with welding heat.
Heat-Exchanger and Equipment Components
Plate and sheet can be cut, formed and welded into equipment parts where dimensional stability, corrosion resistance and fabrication compatibility are required. Material selection must still account for process temperature, fluid chemistry and chloride exposure.
Architectural and Fabricated Stainless Components
304 sheet and plate are also used for panels, covers, trim and fabricated structural or equipment components where both surface appearance and corrosion performance influence material selection. Finish requirements should be stated separately from the stainless grade.
OCTAL Metals Supply and Processing Scope
As a 304 stainless steel plate supplier, OCTAL Metals provides 304 and 304L material in plate, sheet and coil forms together with project-specified cutting and surface-processing requirements. Supply can be coordinated with laser cutting, plasma cutting or waterjet cutting according to the required thickness, component geometry and finished edge condition.
The quotation and production basis should define the material grade, governing standard, dimensions, surface finish, quantity, processing requirements and inspection documentation before order release. Special sizes and project-specific processing can then be reviewed against available production and stock conditions.
FAQ
Q1: Can 304L stainless steel plate be dual certified as 304/304L?
A1: Yes, when the actual chemical composition and mechanical properties satisfy both grade requirements. Dual certification should be confirmed on the material certificate rather than assumed from the 304L designation.
Q2: What should be specified when ordering ASTM A240 304 stainless steel plate?
A2: Specify the grade, standard, product form, thickness, width, length, surface finish, quantity, processing requirements and required inspection documentation.
Q3: How can delivered 304/304L stainless steel plate be verified?
A3: Match the material certificate to the heat or lot identification, then verify dimensions, surface condition and specified test results. PMI or third-party inspection can be added where required.
Q4: Does a 2B, No.1 or polished finish change the 304 stainless steel grade?
A4: No. Surface finish defines the delivered surface condition, while 304/304L defines the alloy grade. Grade and finish should therefore be specified separately when ordering.