Stainless Steel 304L Grade – SUS304L
Stainless Steel 304L (SUS304L) is the low-carbon variant of the standard 304 austenitic stainless steel. With carbon restricted to 0.03% maximum, 304L resists carbide precipitation at the grain boundaries during welding, eliminating the need for post-weld annealing in most applications. It offers the same excellent general corrosion resistance, formability, and hygienic properties as Grade 304 while being far less prone to sensitisation, making it the preferred choice for welded fittings, tanks, and process equipment in the food, beverage, pharmaceutical, and general chemical industries.
International Equivalent Designations – Stainless Steel 304L Grade
Stainless Steel 304L is recognised worldwide under several national and international designations. The table below lists the principal equivalents:
| Standard / Country | Designation | Description |
|---|
| AISI / ASTM / UNS (USA) | 304L / S30403 | American standard designation |
| Europe (EN / DIN) | 1.4307 / X2CrNi18-9 | European Werkstoff number and steel name |
| Japan (JIS) | SUS 304L | Japanese Industrial Standard |
| BS (United Kingdom) | 304S11 | British Standard designation |
| GB (China) | 022Cr19Ni10 | Chinese national standard |
| France (AFNOR) | Z2CN18-10 | French standard designation |
| ISO | X2CrNi18-9 | International Organization for Standardization |
Chemical Composition (Weight %)
| Element | Min (%) | Max (%) |
|---|
| Chromium (Cr) | 18.00 | 20.00 |
| Nickel (Ni) | 8.00 | 12.00 |
| Carbon (C) | – | 0.030 |
| Manganese (Mn) | – | 2.00 |
| Silicon (Si) | – | 0.75 |
| Phosphorus (P) | – | 0.045 |
| Sulphur (S) | – | 0.030 |
| Nitrogen (N) | – | 0.10 |
| Iron (Fe) | Balance |
Mechanical Properties (Annealed Condition – Room Temperature)
| Property | Value | Unit |
|---|
| Tensile Strength (UTS) | 485 min | MPa (70,000 psi) |
| Yield Strength (0.2% Proof) | 170 min | MPa (25,000 psi) |
| Elongation (in 50 mm) | 40 min | % |
| Hardness – Brinell | 201 max | HB |
| Hardness – Rockwell B | 92 max | HRB |
| Hardness – Vickers | 210 max | HV |
| Elastic Modulus | 193 | GPa |
| Poisson’s Ratio | 0.27 – 0.30 | – |
Physical Properties
| Property | Value | Unit |
|---|
| Density | 8.00 | g/cm³ |
| Melting Range | 1400 – 1450 | °C (2550 – 2650 °F) |
| Specific Heat Capacity (0–100°C) | 500 | J/kg·K |
| Thermal Conductivity (at 100°C) | 16.2 | W/m·K |
| Thermal Expansion Coefficient (0–100°C) | 17.2 × 10⁻⁶ | /°C |
| Electrical Resistivity (at 20°C) | 72 | µΩ·cm |
| Magnetic Permeability | 1.008 max | Non-magnetic (annealed) |
Corrosion Resistance
Stainless Steel 304L offers the same general corrosion resistance as standard Grade 304, with the added benefit of superior resistance to weld-decay. Key characteristics include:
- General Corrosion: Good resistance to a wide range of atmospheric environments, foodstuffs, sterilising solutions, organic chemicals, and dyestuffs.
- Pitting and Crevice Corrosion: Without molybdenum, 304L is more susceptible to pitting in chloride-rich environments than Grade 316L; not recommended for seawater or high-chloride service.
- Sensitisation: The low carbon content (≤0.03%) greatly reduces the risk of chromium carbide precipitation during welding, maintaining corrosion resistance in the heat-affected zone without post-weld annealing.
- Stress Corrosion Cracking (SCC): Can be susceptible to SCC in hot chloride environments above 60°C; duplex or higher-alloy grades are preferable in severe conditions.
Heat Treatment
- Annealing: Heat to 1010–1120°C and cool rapidly by water quenching or rapid air cooling to restore maximum corrosion resistance and softness.
- Hardening by Heat Treatment: Not possible. Strength and hardness can only be increased by cold working.
- Stress Relieving: Rarely required due to the low sensitisation risk of this grade; if performed, cool rapidly through the 425–860°C range.
Fabrication and Weldability
- Machinability: Moderate – rated approximately 45% of AISI 1212. Slow speeds, heavy feeds, sharp tools, and adequate coolant are recommended due to work hardening.
- Formability: Excellent – readily bent, drawn, spun, and deep drawn. Work hardens significantly during cold forming.
- Weldability: Excellent using GTAW (TIG), GMAW (MIG), SMAW (Stick), FCAW, and resistance welding processes. No pre-heat or post-weld heat treatment is required, making 304L the preferred choice over standard 304 for welded fabrications.
- Recommended Filler Metal: ER308L to match the low-carbon composition and preserve corrosion resistance across the weld.
Related Sub-Grades of Stainless Steel 304L Grade
| Grade | Relation to 304L |
|---|
| SS 304 | Standard carbon (0.08% max) version; higher strength but more prone to sensitisation when welded |
| SS 304H | Higher carbon (0.04–0.10%) version for improved elevated-temperature strength |
| SS 304N | Nitrogen-strengthened version offering higher mechanical strength |
| SS 316L | Molybdenum-bearing version offering superior pitting and crevice corrosion resistance |
| SS 321 | Titanium-stabilised version offering improved resistance to intergranular corrosion at high temperature |
Applicable Standards & Specifications
| Standard | Scope |
|---|
| ASTM A240 / A240M | Plate, sheet, and strip |
| ASTM A276 | Bar and shapes |
| ASTM A312 | Seamless and welded pipe |
| ASTM A403 | Wrought fittings |
| ASTM A182 | Flanges and forged fittings |
| ASTM A479 | Bar for boilers and pressure vessels |
| EN 10088-1 / EN 10088-3 | Stainless steels – list and technical delivery conditions |
| DIN 17440 | Stainless steel – plate, strip, bar, wire, forgings |
Typical Applications
- Welded pipes, tubes, and fittings for food, beverage, and dairy processing
- Brewery, winery, and pharmaceutical process equipment and reactors
- Chemical containers, storage tanks, and piping systems
- Kitchen equipment, sinks, and commercial food-service fittings
- Architectural trim and fasteners in mild environments
- Heat exchangers, condensers, and boiler components
- Sanitary and hygienic fittings for hospitals and cleanrooms
- Welded structural components requiring corrosion resistance without post-weld treatment
Supply Forms – Stainless Steel Fittings India (SSF)
At Stainless Steel Fittings India (SSF), we manufacture and export Stainless Steel 304L / AISI 304L / 1.4307 / SUS 304L components in the following forms:
- Pipe Fittings (Elbows, Tees, Reducers, Caps, Crosses)
- Tube Fittings (Compression & Push-to-Connect)
- Flanges (WN, SO, Blind, Threaded, Lap Joint, Socket Weld)
- Threaded Fittings (NPT, BSPT, BSPP)
- Fasteners (Bolts, Nuts, Washers, Studs, Screws)
- Investment Castings
- Precision Machined Components
- Sanitary & Hygienic Fittings
For technical queries, RFQs, or custom requirements in Stainless Steel 304L Grade (AISI 304L / SUS 304L / 1.4307 / UNS S30403), contact us today. Our engineering team is ready to assist with material certifications, mill test reports, and export documentation.
