Stainless Steel 304
Stainless Steel 304 (UNS S30400) is the most widely used austenitic grade in the 300 series. Its 18% chromium and 8% nickel composition produces a stable passive oxide layer, broad corrosion resistance, and consistent weldability for general-purpose industrial use.
1. Chemical Composition
The table below lists the elemental limits for Stainless Steel 304, including the chromium, nickel, and impurity thresholds that define its corrosion performance and austenitic structure.
| Grade | C | Mn | P | S | Si | Cr | Ni | Mo | Other |
| TP304 | ≤ 0.080 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | ≤ 1.00 | 18.00–20.00 | 8.00–11.00 | — | — |
2. Mechanical Properties
The following table lists minimum tensile, yield, and ductility values for Stainless Steel 304 in the annealed condition. These apply to seamless and welded pipe and tube forms.
| Grade | Condition | Tensile Strength Min, MPa (ksi) | Yield Strength Min, MPa (ksi) | Elongation Min, % | Heat Treatment Temp |
| TP304 | Annealed | 515 (75) | 205 (30) | 35 | 1040°C (1900°F) min |
3. Equivalent Grade
This table provides Stainless Steel 304 equivalent designations across major international standards. This helps procurement and engineering teams confirm material equivalency.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 304 | S30400 | S30408 | 06Cr19Ni10 | SUS304 | X5CrNi18-10 | 1.4301 | 08X18H10 |
4. Key Technical Advantages
- Passive Layer Stability: The 18% chromium content forms a stable chromium oxide passive layer that resists oxidising acids, atmospheric corrosion, and mild aqueous environments.
- Weldability: Grade 304 can be welded by all standard fusion methods without post-weld heat treatment in most applications. However, inter-granular sensitisation risk exists in heavy-section welds.
- Formability: Good cold-working characteristics make it suitable for deep-drawn components, rolled tube forms, and complex fabricated assemblies.
- Low-Temperature Toughness: Retains austenitic structure and impact toughness at sub-zero temperatures, with no ductile-to-brittle transition behavior typical of ferritic steels.
Technical Note: In chloride-containing environments above 60°C, 304 is susceptible to stress corrosion cracking. Grade 316 or duplex grades should be evaluated for such conditions.
5. Common Manufacturing Standards
Stainless Steel 304 is produced and tested under the following international manufacturing standards:
ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes.
ASTM A213: Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes.
ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service.
DIN EN 10216-5: Seamless steel tubes for pressure purposes — Technical delivery conditions for stainless steel tubes.
JIS G3459: Stainless Steel Pipes.
JIS G3463: Stainless Steel Boiler and Heat Exchanger Tubes.
GB/T 14976: Seamless stainless steel tubes for fluid transport.
GOST 9941: Seamless cold- and warm-deformed pipes from corrosion-resistant steel.
Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Pipe | A312 | EN 10216-5 | G3459 | 14976 | 9941 |
| Welded Pipe | A312 | EN 10217-7 | G3459 | 12771 | - |
| Heat Exchanger Tube | A213 / A249 | EN 10216-5 | G3463 | 13296 | 9941 |
| General Service Tube | A269 | EN 10216-5 | G3463 | 14976 | - |
6. Primary Applications
- Food and Beverage Processing: Sanitary piping, vessels, and fittings used in dairy, brewing, and juice processing, where mild corrosive cleaning agents are used.
- Heat Exchangers: Shell-and-tube heat exchangers, condensers, and evaporators in chemical plants and HVAC systems that need reliable oxidation resistance.
- Pharmaceutical and Biotech: Pure water systems, sterile transfer lines, and process vessels where surface cleanliness and chemical inertness matter.
- Architectural and Structural: Exterior cladding, handrails, and structural tubing where finish appearance and atmospheric corrosion resistance are needed.
- Water Treatment: Filtration housings, distribution piping, and reverse osmosis system components exposed to treated water streams.