Stainless Steel 304 Grade
Stainless Steel 304 Grade is the most widely used austenitic stainless steel in the world. It offers excellent corrosion resistance, good formability, and outstanding weldability. Known as 18/8 stainless steel due to its nominal 18% chromium and 8% nickel content, Grade 304 is used across a vast range of industries including food processing, chemical, pharmaceutical, architectural, and general engineering applications.
Chemical Composition – SS 304 Grade
| Element | Min (%) | Max (%) |
|---|
| Chromium (Cr) | 18.00 | 20.00 |
| Nickel (Ni) | 8.00 | 10.50 |
| Carbon (C) | — | 0.08 |
| 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 – SS 304 Grade
| Property | Value |
|---|
| Tensile Strength (min) | 515 MPa (75 ksi) |
| Yield Strength – 0.2% Proof (min) | 205 MPa (30 ksi) |
| Elongation (min) | 40% |
| Hardness (Brinell, max) | 201 HB |
| Hardness (Rockwell B, max) | 92 HRB |
| Density | 8.00 g/cm³ |
Physical Properties – SS 304 Grade
| Property | Value |
|---|
| Density | 8.00 g/cm³ |
| Melting Range | 1400–1450°C (2552–2642°F) |
| Thermal Conductivity (at 100°C) | 16.2 W/m·K |
| Electrical Resistivity | 720 nΩ·m |
| Modulus of Elasticity | 193 GPa |
| Coefficient of Thermal Expansion (0–100°C) | 17.2 × 10⁻⁶/°C |
| Specific Heat Capacity | 500 J/kg·K |
Corrosion Resistance – SS 304 Grade
Grade 304 offers excellent resistance to a wide range of atmospheric environments and many corrosive media. It resists oxidation up to 870°C (1598°F) in intermittent service and up to 925°C (1697°F) in continuous service. However, it is susceptible to pitting and crevice corrosion in chloride-containing environments, and stress corrosion cracking may occur above 60°C. For aggressive chloride environments, Grade 316 is recommended.
International Grade Equivalents – SS 304
| Standard | Designation | Description |
|---|
| USA (AISI/ASTM) | 304 / S30400 | American standard |
| Europe (EN) | 1.4301 / X5CrNi18-10 | European standard |
| Japan (JIS) | SUS 304 | Japanese Industrial Standard |
| BS (United Kingdom) | 304 S31 | British Standard designation |
| GB (China) | 0Cr18Ni9 | Chinese national standard |
| ISO | X5CrNi18-10 | International Organization for Standardization |
Relevant Standards – SS 304 Grade
- ASTM A240: Plate, sheet, and strip
- ASTM A276: Bar and shapes
- ASTM A312: Seamless and welded pipe
- ASTM A403: Wrought fittings
- ASTM A182: Flanges and fittings (forged)
- EN 10088-1: Stainless steels – list of stainless steels
- DIN 17440: Stainless steel – plate, strip, bar, wire, forgings
Heat Treatment
- Annealing: Heat to 1010–1120°C and cool rapidly (water quench or rapid air cool) to restore full corrosion resistance and relieve stress.
- Hardening by Heat Treatment: Not possible. Cold working is the only method to increase strength and hardness.
- Stress Relieving: Not recommended due to risk of sensitisation; if required, cool rapidly through the 425–860°C sensitisation range.
Fabrication and Weldability
- Machinability: Moderate – rated approximately 45% of AISI 1212. Slow speeds, heavy feeds, and sharp tools recommended.
- Formability: Excellent – can be readily bent, formed, and deep drawn. Work hardens significantly during cold working.
- Weldability: Excellent using GTAW (TIG), GMAW (MIG), SMAW (Stick), FCAW, and SAW processes. No pre-heat required. Post-weld annealing may be required for maximum corrosion resistance.
Typical Applications – SS 304 Grade
- Food processing equipment and kitchen appliances
- Chemical containers, pressure vessels, and piping
- Architectural cladding, facades, and handrails
- Pharmaceutical processing equipment
- Dairy and brewing industry equipment
- Heat exchangers and condensers
- Automotive trim and exhaust parts
- 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 304 Grade (AISI 304 / SUS 304 / 1.4301 / UNS S30400), contact us today. Our engineering team is ready to assist with material certifications, mill test reports, and export documentation.
