Introduction
SUS304 is the most widely used stainless steel in the world — so prevalent that it has become virtually synonymous with "stainless steel" itself. Whether in the fastener industry, food processing, construction, or consumer electronics, 304 stainless steel is the default choice across virtually every sector.
In common usage, 304 refers to the ASTM A276/A276M designation, while SUS304 refers to the JIS G4303 designation. Since their chemical compositions are essentially identical, the two are used interchangeably in most industrial and commercial contexts. This page uses JIS G4303 as the primary reference.
SUS304 is an austenitic stainless steel containing chromium (Cr) and nickel (Ni). Its excellent corrosion resistance is derived from a stable passive oxide film that forms on the surface, effectively blocking corrosive media. In addition to Cr and Ni, SUS304 contains small amounts of carbon, silicon, manganese, phosphorus, and sulfur — all at levels low enough to have minimal impact on overall performance.
Content authorized for publication by FULLERKREG.
SUS304 Chemical Composition
Reference standard: JIS G4303
| Grade | C (%) | Mn (%) | Si (%) | P (%) | S (%) | Ni (%) | Mo (%) | Cr (%) |
|---|---|---|---|---|---|---|---|---|
| SUS304 | ≤ 0.08 | ≤ 2.00 | ≤ 1.00 | ≤ 0.045 | ≤ 0.03 | 8.00–10.5 | — | 18.00–20.00 |
Note: Molybdenum (Mo) is not a required element in the standard specification. However, in China's fastener industry, 304 raw material sometimes includes intentional additions of Mo (to improve corrosion resistance) and Cu (to improve cold heading formability).
SUS304 Composition Across Different Standards
While 304 stainless steel is defined by many international standards, minor compositional differences exist between them. The table below summarizes key variations:
| # | Standard | Grade | UNS | C | Mn | P | S | Si | Cr (%) | Ni (%) | N | Cu |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | ASTM A276/A276M | 304 | S30400 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–11.0 | — | — |
| 2 | ASTM A959 | 304 | S30400 | ≤0.07 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 17.5–19.5 | 8.0–11.0 | — | — |
| 3 | ASTM A240/A240M | 304 | S30400 | ≤0.07 | ≤2 | ≤0.045 | ≤0.03 | ≤0.75 | 17.5–19.5 | 8.0–10.5 | — | — |
| 4 | ASTM A182/A182M | F304 | S30400 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–11.0 | ≤0.1 | — |
| 5 | ASTM A193/A193M | 304 | S30400 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–11.0 | — | — |
| 6 | ASTM A269/A269M | TP304 | S30400 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–11.0 | — | — |
| 7 | ASTM A312/A312M | TP304 | S30400 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–11.0 | — | — |
| 8 | ASTM A320/A320M | 304 | S30400 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–11.0 | — | — |
| 9 | ASTM A493 | 304 | S30400 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–10.5 | ≤0.1 | ≤1 |
| 10 | ASTM A554 | MT-304 | S30400 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–11.0 | — | — |
| 11 | JIS G4303:2012 | SUS304 | — | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–10.5 | — | — |
| 12 | JIS G4304:2012 | SUS304 | — | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–10.5 | — | — |
| 13 | JIS G4305:2012 | SUS304 | — | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–10.5 | — | — |
| 14 | GB/T 20878-2007 | 6Cr19Ni10 | S30408 | ≤0.08 | ≤2 | ≤0.045 | ≤0.03 | ≤1 | 18.0–20.0 | 8.0–11.0 | — | — |
Physical and Mechanical Properties
Mechanical Properties (JIS G4303)
| Grade | Tensile Strength σb (MPa) | Yield Strength σ0.2 (MPa) | Elongation δ5 (%) | Reduction of Area ψ (%) | Hardness | Density (g/cm³) | Melting Point (°C) |
|---|---|---|---|---|---|---|---|
| SUS304 | ≥ 520 | ≥ 205 | ≥ 40 | ≥ 60 | ≤ 187 HB / ≤ 90 HRB / ≤ 200 HV | 7.93 | 1398–1454 |
Other Physical Properties
| Property | Value |
|---|---|
| Melting Point | 1398–1454 °C |
| Specific Heat Capacity (0–100°C) | 0.50 kJ/(kg·K) |
| Thermal Conductivity at 100°C | 16.3 W/(m·K) |
| Thermal Conductivity at 500°C | 21.5 W/(m·K) |
| Thermal Expansion (0–100°C) | 17.2 × 10⁻⁶ /K |
| Thermal Expansion (0–500°C) | 18.4 × 10⁻⁶ /K |
| Electrical Resistivity (20°C) | 0.73 × 10⁻⁶ Ω·m |
| Elastic Modulus (20°C) | 193 kN/mm² |
Applications of SUS304 Stainless Steel
SUS304 is used across virtually every industry. Key application areas include:
- Electronics & Appliances — inner drums of washing machines, microwave oven housings, range hood covers, control panels, pump housings, watch and phone casings
- Water Treatment — valves, flanges, water pipes, and purification equipment
- Medical Devices — surgical instruments, medical equipment housings
- Chemical Processing — tanks, pipelines, and valves in mildly corrosive environments
- Food Processing — food machinery, conveying equipment, storage vessels
- Automotive — exhaust systems, structural components, trim parts
- Power Generation — generator components, transmission infrastructure
- Marine Engineering — ship fittings, offshore platform components
- Furniture & Architecture — hardware fittings, decorative surfaces, handrails
- Instrumentation — precision instruments, optical equipment housings
In short, SUS304 stainless steel appears in almost every industrial and consumer application imaginable.
Browse our stainless steel fastener products: Stainless Steel Helical Inserts, Dome Nuts (DIN 1587) – A2 Stainless Steel, Weld Nuts (DIN 929) – Stainless Steel, and Carriage Bolts (DIN 603) – Stainless Steel A2.
Machinability and Fabrication
Formability (Plasticity)
SUS304 has excellent formability and responds well to both cold and hot working. It can be shaped by forging, drawing, bending, stamping, and roll forming — making it the standard choice for cold-headed fasteners such as screws, bolts, and nuts.
Weldability
SUS304 has good weldability and can be joined using common methods including arc welding and gas-shielded welding (MIG/TIG). Welded joints maintain high strength and corrosion resistance. This is a key advantage over free-machining grades such as SUS303, which has limited weldability due to its sulfur content.
Machinability
SUS304 has moderate machinability. While it can be turned, milled, and drilled to achieve high-precision parts, its work-hardening tendency makes it more challenging to machine at high speeds compared to free-machining grades. For applications requiring intensive CNC turning or automatic lathe operations, SUS303 is the preferred alternative.
Heat Treatment
SUS304 can be solution-annealed (solid solution treated) to improve toughness and reduce hardness and strength. This treatment is commonly applied for pipeline, valve, and pressure vessel applications.
Standards reference: JIS G4303 | JIS G4304 | JIS G4305 | ASTM A276/A276M | ASTM A959 | GB/T 20878 | GB/T 1220
Content authorized for publication by FULLERKREG.