Stainless Steel SS304
Stainless Steel SS304 is the most widely used austenitic stainless steel, known for its excellent corrosion resistance, formability, and weldability. It contains 18% chromium and 8% nickel, which provide outstanding resistance to oxidation and most atmospheric environments. SS304 maintains its strength and toughness across a wide range of temperatures, making it suitable for both industrial and household applications.
This grade is non-magnetic in the annealed condition but may become slightly magnetic after cold working. SS304 is also highly hygienic, easy to clean, and resistant to food acids, making it a preferred material for kitchen equipment, chemical containers, and architectural structures.
In short, SS304 is an all-purpose, corrosion-resistant, and durable stainless steel, ideal for environments where cleanliness, strength, and longevity are essential.
Applications
Used in food processing equipment, dairy, and beverage industries due to its hygienic surface and corrosion resistance.
Ideal for kitchen utensils, sinks, and cookware.
Extensively used in chemical containers, storage tanks, and pipelines.
Applied in architectural structures and decorative components.
Commonly used in automobile trim and exhaust systems.
Utilized in pharmaceutical and medical equipment where cleanliness is essential.
Used in marine environments for fittings, fasteners, and hardware.
Found in pressure vessels and heat exchangers in industrial plants.
Chemical Composition
| Element | Carbon (C) | Manganese (Mn) | Silicon (Si) | Phosphorus (P) | Sulphur (S) | Chromium (Cr) | Nickel (Ni) | Nitrogen (N) | Iron (Fe) |
|---|---|---|---|---|---|---|---|---|---|
| Percentage (%) | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | ≤ 0.045 | ≤ 0.030 | 18.00 – 20.00 | 8.00 – 10.50 | ≤ 0.10 | Balance |
Hardness
Stainless Steel SS304 has a Brinell Hardness (HB) of approximately 160–190 HB in the annealed condition.
When cold worked, its hardness can increase significantly, reaching up to 250 HB or more, depending on the degree of deformation.
It is a non-hardenable grade by heat treatment, but work hardening can improve strength and hardness.
Equivalent Grades
- AISI / SAE 304
- UNS S30400
- EN / DIN 1.4301
- BS (British Standard) 304S15 / 304S31
- JIS (Japan) SUS 304
- ISO X5CrNi18-10
- GOST (Russia) 08Х18Н10
- IS (India) IS 6911 304
Heat Treatment
Annealing:
Performed at a temperature range of 1010°C to 1120°C, followed by rapid cooling in water or air.
This process helps relieve internal stresses and restore ductility after cold working.
Stress Relieving:
Conducted at 450°C to 600°C for 1 hour per 25 mm of thickness, followed by slow cooling.
Used to reduce residual stresses without significantly affecting corrosion resistance.
Hardening:
SS304 cannot be hardened by heat treatment, as it is an austenitic stainless steel.
It can only be hardened through cold working.
Hardening
SS304 cannot be hardened by conventional heat treatment methods because it is an austenitic stainless steel, which means it does not undergo a martensitic transformation on cooling.
However, hardness and strength can be increased through cold working processes such as rolling, drawing, or forging. Cold working significantly enhances tensile strength and hardness but reduces ductility.
For applications requiring higher hardness with similar corrosion resistance, SS301 or SS302 may be used as alternatives, as they respond better to cold working.
Welding
Recommended Filler Materials: Use AWS E308L or ER308L filler rods/wires for best corrosion resistance and strength match.
Preheating: Not required for SS304.
Post-Weld Heat Treatment: Generally not necessary; however, annealing at 1050–1100°C followed by rapid cooling can help restore corrosion resistance if sensitization occurs.
Precautions: Avoid overheating during welding to prevent carbide precipitation (which can cause intergranular corrosion).
Machinability
Cutting Tools: Use carbide-tipped or high-speed steel (HSS) tools with sharp edges to minimize work hardening.
Speed and Feed: Employ slower cutting speeds and higher feed rates to reduce heat buildup.
Coolant: A sulfur-based cutting fluid or coolant is recommended to enhance tool life and surface finish.
Work Hardening: SS304 tends to work harden rapidly, so continuous cutting without dwelling is important.
Surface Finish: With proper tooling and coolant, an excellent surface finish can be achieved.
Physical Properties
| Property | Value |
|---|---|
| Density | 7.93 g/cm³ |
| Melting Point | 1400 – 1450 °C |
| Thermal Conductivity | 16.2 W/m·K (at 100 °C) |
| Electrical Resistivity | 0.072 × 10⁻⁶ Ω·m (at 20 °C) |
| Specific Heat Capacity | 500 J/kg·K |
| Modulus of Elasticity (Young’s Modulus) | 193 GPa |
| Poisson’s Ratio | 0.29 |
| Coefficient of Thermal Expansion | 17.2 × 10⁻⁶ /°C (0–100 °C range) |
| Magnetic Properties | Essentially non-magnetic in the annealed condition, may become slightly magnetic when cold worked. |
| Tensile Strength | 515 – 720 MPa |
| Yield Strength (0.2% Proof) | ≥ 205 MPa |
| Elongation | ≥ 40% in 50 mm gauge length |
Chemical Properties
| Property | Value |
|---|---|
| Corrosion Resistance | Excellent — resists corrosion in a wide range of atmospheric and chemical environments, including many acids, alkalis, and chlorides. |
| Oxidation Resistance | Outstanding — maintains integrity up to 870°C in continuous service and up to 925°C in intermittent service. |
| Acid Resistance | Good resistance to nitric acid and organic acids; limited resistance to hydrochloric and sulfuric acids. |
| Alkali Resistance | Resists most weak and moderate alkaline solutions. |
| Pitting Resistance | Moderate — may pit in chloride environments; improved with higher molybdenum grades (e.g., 316). |
| Scaling Resistance | Good — forms a stable chromium oxide layer protecting the surface from scaling and corrosion. |
| Chemical Stability | Excellent — remains chemically inert in most neutral environments. |
| Atmospheric Resistance | Excellent — resists rusting and tarnishing in humid and industrial atmospheres. |
Dealer
Tata Steel Limited – Major supplier of stainless steel products across India.
Jindal Stainless Limited (JSL) – One of India’s largest stainless steel manufacturers offering SS304 sheets, rods, and bars.
Virat Special Steels Pvt. Ltd. – Supplier of stainless and tool steels in various grades including SS304.
Metal Udyog (Mumbai) – Stockist and exporter of stainless steel bars, sheets, and tubes.
Aesteiron Steels LLP – Exporter and dealer of SS304 and other stainless grades in various forms.
Rajendra Industrial Corporation – Specializes in SS304 pipes, fittings, and flanges.