SS 304 Stainless Steel — Complete Guide to Grades, Properties, and Applications
SS 304 is the world's most widely used stainless steel grade, accounting for over 50% of all stainless steel consumed globally. Its combination of excellent corrosion resistance, good formability, attractive appearance, and reasonable cost makes it the default choice for thousands of applications — from kitchen sinks to chemical reactors. As a leading stainless steel pipe manufacturer in India and SS pipe supplier in Vadodara, Creative Metal Industries stocks SS 304 in all product forms: pipes, plates, sheets, fittings, flanges, and bars.
What is SS 304 Stainless Steel?
SS 304 (also designated UNS S30400, EN 1.4301, or AISI 304) is an austenitic chromium-nickel stainless steel. The term "austenitic" refers to its face-centred cubic crystal structure, which gives it non-magnetic properties, excellent ductility, and the ability to be work-hardened but not heat-treated for strength.
The "18/8" designation that SS 304 is often called reflects its nominal composition: 18% Chromium (which forms the protective passive oxide layer) and 8% Nickel (which stabilises the austenitic structure). This combination creates a steel that resists oxidation and corrosion in a wide range of atmospheric, chemical, and food-processing environments without requiring protective coatings or painting.
First developed in the early 1900s, SS 304 has become the backbone of the stainless steel industry. Every stainless steel pipe manufacturer in India — including Creative Metal Industries — produces and stocks this grade in greater quantity than any other.
Chemical Composition of SS 304
| Element | SS 304 | SS 304L | Role in the Alloy |
|---|---|---|---|
| Carbon (C) | 0.08% max | 0.030% max | Strengthens but promotes sensitisation at high levels |
| Chromium (Cr) | 18.0–20.0% | 18.0–20.0% | Forms passive Cr₂O₃ oxide film — primary corrosion barrier |
| Nickel (Ni) | 8.0–10.5% | 8.0–12.0% | Stabilises austenite; improves ductility and toughness |
| Manganese (Mn) | 2.0% max | 2.0% max | Deoxidiser; partially substitutes for nickel |
| Silicon (Si) | 0.75% max | 0.75% max | Deoxidiser; improves high-temperature oxidation resistance |
| Phosphorus (P) | 0.045% max | 0.045% max | Impurity — kept low to prevent embrittlement |
| Sulphur (S) | 0.030% max | 0.030% max | Impurity — kept low; improves machinability in free-cutting variants |
| Iron (Fe) | Balance | Balance | Base metal matrix |
The key to SS 304's corrosion resistance is the minimum 10.5% chromium content (actually 18%+ in 304) which spontaneously forms an invisible, self-healing chromium oxide (Cr₂O₃) passive film on the surface. This film is only 1-5 nanometres thick but prevents oxygen and corrosive media from reaching the underlying iron.
Mechanical Properties of SS 304
| Property | Value (Annealed Condition) | Significance |
|---|---|---|
| Tensile Strength | 515 MPa min (75 ksi) | Resistance to being pulled apart |
| Yield Strength (0.2%) | 205 MPa min (30 ksi) | Stress at which permanent deformation begins |
| Elongation | 40% min (in 50mm) | Excellent formability — deep drawing, bending |
| Hardness | 92 HRB max (201 HBW max) | Relatively soft — easy to machine and form |
| Elastic Modulus | 193 GPa | Stiffness — same as carbon steel |
| Density | 8.0 g/cm³ | Slightly heavier than carbon steel (7.85 g/cm³) |
| Melting Range | 1400–1450°C | High — suitable for elevated temperature service |
| Thermal Conductivity | 16.2 W/m·K at 100°C | Lower than carbon steel — retains heat longer |
| Specific Heat | 500 J/kg·K | Higher than carbon steel — slow to heat and cool |
SS 304 cannot be hardened by heat treatment (unlike martensitic grades 410/420). It can only be strengthened by cold working — cold-drawn pipe and cold-rolled sheet have significantly higher tensile and yield strength but reduced ductility. For most piped applications, the annealed (solution treated at 1050°C, water quenched) condition is standard.
Key Applications of SS 304
Food & Kitchen Equipment
Sinks, countertops, cookware, commercial kitchen surfaces, food processing conveyors, storage tanks, dairy equipment. SS 304's non-reactive surface doesn't impart taste or colour to food.
Chemical Processing
Tanks, reactors, heat exchangers, piping for organic acids, mild inorganic acids, and alkali solutions. Not recommended for hydrochloric acid or hot concentrated sulphuric acid.
Pharmaceutical & Biotech
Process vessels, piping (316L preferred for higher grades), water treatment equipment, clean room fittings. Surface finish Ra ≤ 0.8µm achievable for hygienic applications.
Architecture & Construction
Curtain wall panels, handrails, elevator doors, signage, roofing, facade cladding. No.4 brushed and mirror finishes are popular for architectural use.
Automotive & Transport
Exhaust systems, trim, fuel tanks, structural components. SS 304's resistance to heat and road salt makes it ideal for underbody and exhaust applications.
Water Treatment
Filter housings, tank linings, distribution piping, desalination pre-treatment. For high-chloride water, 316L is recommended instead.
Welding and Fabrication Tips for SS 304
SS 304 is highly weldable by all common processes — TIG (GTAW), MIG (GMAW), MMA (SMAW), and SAW. However, certain precautions are essential to avoid corrosion problems in service:
- Use 304L or ER308L filler: Low-carbon filler prevents sensitisation (carbide precipitation at 450-850°C) in the heat-affected zone
- Minimise heat input: Austenitic SS has low thermal conductivity — excessive heat causes distortion and wider HAZ. Use stringer beads, not wide weave
- Back-purge with argon: The root side of TIG welds must be shielded with argon to prevent oxidation (sugaring) which creates corrosion initiation sites
- No preheat required: Unlike carbon and alloy steel, SS 304 should NOT be preheated. Interpass temperature should not exceed 150°C
- Post-weld treatment: Pickle and passivate (HNO₃ + HF) all welds to restore the chromium oxide passive layer. Remove all heat tint colours
- Avoid carbon steel contamination: Use dedicated stainless steel wire brushes, grinding discs, and tools. Carbon steel particles embed in SS and cause rust spots
Why Source SS 304 from Creative Metal Industries?
As one of India's established stainless steel pipe manufacturers and a trusted SS pipe supplier in Vadodara, we offer distinct advantages when you source SS 304 from us:
Complete Product Range
SS 304/304L in pipes (seamless + welded), plates, sheets, fittings, flanges, bars, and structural sections — all from one supplier.
Mill-Direct Stock
Authorised stockist for Sandvik, Ratnamani, Venus, POSCO, Jindal. No middlemen — full traceability from mill to your site.
All Certifications
MTC (EN 10204 3.1/3.2), IBR Form III-C, PMI verification, IGC test (ASTM A262), and third-party inspection under DNV/TUV/SGS.
Same-Day Dispatch
Standard sizes dispatch same day from our 1092 sq.mtr GIDC Makarpura, Vadodara warehouse. Pan-India delivery in 2-5 days.
Frequently Asked Questions — SS 304
What is SS 304 stainless steel made of?
SS 304 contains approximately 18% Chromium and 8% Nickel (18/8 stainless), with max 0.08% Carbon, up to 2% Manganese, and balance Iron. This creates a stable austenitic structure with excellent corrosion resistance in most environments.
Can SS 304 rust?
SS 304 is rust-resistant, not rust-proof. It can develop surface corrosion in chloride-rich (coastal) environments, at contaminated surfaces (carbon steel particles), or at sensitised weld zones. For chloride service, upgrade to 316L. Proper passivation prevents most issues.
What is the difference between SS 304 and SS 304L?
304L has lower carbon (0.03% max vs 0.08%). This prevents sensitisation during welding — eliminating intergranular corrosion risk in the HAZ. For any welded construction, specify 304L. Strength is nearly identical (485 MPa vs 515 MPa tensile).
Need SS 304 Pipes, Plates or Fittings?
Ready stock at Vadodara. Mill-direct pricing. MTC + IBR + PMI on every consignment.