Overview
Type 304 is the most common austenitic stainless steel — often called "18/8" for its 18% chromium / 8% nickel composition. It offers excellent general corrosion resistance, good formability, and ease of fabrication. 304 is the baseline stainless grade for food processing, architectural, chemical, and general industrial applications where moderate corrosion resistance is needed.
ρ = 7930 kg/m³, Composition: Fe-18Cr-8Ni, max 0.08% C
Mechanical Properties
| Property | 304 (Annealed) | 304L (Low Carbon) |
|---|---|---|
| Density | 7,930 kg/m³ | 7,930 kg/m³ |
| Yield Strength (0.2%) | 205 MPa | 170 MPa |
| Ultimate Tensile | 515 MPa | 485 MPa |
| Elongation | 40% | 40% |
| Hardness | 180 BHN max | 180 BHN max |
| Young's Modulus | 193 GPa | 193 GPa |
Corrosion Resistance
304 provides excellent resistance to:
- Atmospheric environments (rural, urban, mild marine)
- Fresh water, steam
- Most organic chemicals, food products
- Oxidizing acids (nitric acid)
- Neutral and alkaline solutions
It is NOT suitable for:
- Chloride environments (seawater, brine, bleach) — causes pitting and crevice corrosion
- Chloride stress corrosion cracking (SCC) above ~60°C
- Reducing acids (hydrochloric, sulfuric at high concentrations)
- Long-term exposure above 425°C without low-carbon grade
Thermal Properties
| Property | Value |
|---|---|
| Melting Range | 1400-1455°C |
| Thermal Conductivity (100°C) | 16 W/m·K (much lower than carbon steel) |
| Specific Heat | 500 J/kg·K |
| Coefficient of Thermal Expansion | 17.2 × 10⁻⁶ /°C (~50% higher than carbon steel!) |
Applications
- Food processing equipment, brewing, dairy
- Architectural trim, building facades, handrails
- Kitchen equipment, appliances, sinks
- Chemical tanks (non-chloride), pharmaceutical equipment
- Process piping for clean water, steam, non-chloride chemicals
- Heat exchangers, fasteners, springs
Fabrication Notes
- 304 work-hardens rapidly; deep drawing may require intermediate annealing
- Weld with 308L filler (over-alloyed by ~2% Cr/Ni)
- Post-weld cleanup (pickling paste or mechanical) restores corrosion resistance
- Non-magnetic in annealed condition (can become slightly magnetic after cold work)
Summary
Type 304 (18/8, density 7930 kg/m³) is the general-purpose stainless steel for non-chloride environments. Use 304L for welded construction to avoid sensitization. Excellent formability, weldability, and general corrosion resistance. For marine, chloride, or reducing acid service, upgrade to 316L.