SUS 304 Stainless Steel: Composition, Properties, and Industrial Applications
SUS 304 Stainless Steel: Composition, Properties, and Industrial Applications
Learn everything about SUS 304 stainless steel — its composition, properties, corrosion resistance, and key differences from SS304 and 316. Discover why SUS 304 remains the most widely used stainless steel in global manufacturing.
Stainless steel has become an essential material in modern engineering and daily life, known for its strength, corrosion resistance, and aesthetic appeal. Among the many grades of stainless steel, SUS 304 is one of the most popular and versatile. Recognized under the Japanese Industrial Standard (JIS), SUS 304 stainless steel is equivalent to AISI 304 or SS304 in the American system.
This grade is widely used across industries due to its excellent mechanical performance, high corrosion resistance, and ease of fabrication. Whether in food processing, architecture, or chemical equipment, SUS 304 continues to be the material of choice for engineers and manufacturers seeking durability and cost efficiency.
1. What Is SUS 304 Stainless Steel?
The term SUS 304 comes from the Japanese designation “Steel Use Stainless,” part of the JIS G4303 standard. It belongs to the austenitic family of stainless steels, which are known for their ductility, non-magnetic behavior, and excellent weldability.
SUS 304 is often referred to as an “18/8” stainless steel — meaning it contains approximately 18% chromium and 8% nickel. This chemical balance creates a protective oxide layer on the surface that resists rust and oxidation, making it ideal for applications exposed to moisture or chemical environments.
Although SUS 304 and SS304 are labeled differently, they share nearly identical compositions and physical properties. The difference mainly lies in the national standards used to define them.
2. Chemical Composition of SUS 304
The properties of SUS 304 stainless steel are determined by its carefully controlled chemical composition.
| Element | Content (%) | Function |
|---|---|---|
| Chromium (Cr) | 18.0–20.0 | Provides corrosion resistance and surface hardness |
| Nickel (Ni) | 8.0–10.5 | Enhances ductility and toughness |
| Carbon (C) | ≤ 0.08 | Improves strength while maintaining weldability |
| Manganese (Mn) | ≤ 2.0 | Increases strength and deoxidation during melting |
| Silicon (Si) | ≤ 1.0 | Improves oxidation resistance |
| Phosphorus (P) | ≤ 0.045 | Controlled to maintain toughness |
| Sulfur (S) | ≤ 0.03 | Improves machinability in small amounts |
| Iron (Fe) | Balance | Base element |
This balanced composition allows SUS 304 to maintain both strength and corrosion resistance, making it suitable for a broad range of applications.
3. Mechanical Properties and Workability
One of the key reasons SUS 304 is so widely used is its excellent mechanical performance combined with ease of fabrication.
- Tensile Strength: 515–750 MPa
- Yield Strength: ≥ 205 MPa
- Elongation: ≥ 40%
- Hardness: ≤ 92 HRB
These mechanical properties allow SUS 304 to be deep drawn, rolled, or bent without cracking — a critical advantage for manufacturers of sinks, kitchen utensils, and architectural panels.
Its austenitic structure ensures toughness even at cryogenic temperatures, making it suitable for low-temperature environments such as storage tanks and cryogenic vessels.
4. Corrosion Resistance and Surface Protection
The superior corrosion resistance of SUS 304 stainless steel comes from its chromium oxide layer, which forms naturally when exposed to oxygen. This self-healing passive film protects the steel from rust and oxidation.
SUS 304 performs exceptionally well in most environments, including:
- Atmospheric conditions
- Freshwater and mild chemical exposure
- Food and beverage processing environments
However, in chloride-rich environments, such as marine applications or swimming pool areas, SUS 304 can suffer from pitting or crevice corrosion. In such cases, SUS 316, which contains molybdenum, offers better protection against chloride attack.
Regular cleaning and passivation can further enhance the corrosion resistance of SUS 304, ensuring a longer lifespan even in harsh environments.
5. SUS 304 vs SS304 — Are They the Same?
One of the most common questions in material selection is the difference between SUS 304 and SS304. The answer is simple: they are essentially the same material, defined by different national standards.
- SUS 304: Japanese Industrial Standard (JIS G4303)
- SS 304: American Iron and Steel Institute (AISI) or ASTM Standard
Both have nearly identical chemical compositions, physical properties, and mechanical performance. Engineers and manufacturers can use them interchangeably, provided the project specifications allow for equivalent standards.
Globally recognized equivalents include:
- EN 1.4301 (Europe)
- UNS S30400 (United States)
- DIN X5CrNi18-10 (Germany)
- GB 06Cr19Ni10 (China)
6. SUS 304 vs SUS 316 – Choosing the Right Grade
While SUS 304 is suitable for general applications, SUS 316 includes 2–3% molybdenum, providing superior resistance to chlorides and acids.
| Property | SUS 304 | SUS 316 |
|---|---|---|
| Molybdenum | No | 2–3% |
| Corrosion Resistance | Excellent (general) | Superior (chloride resistance) |
| Cost | Lower | Higher |
| Common Uses | Kitchenware, piping, architecture | Marine, chemical, medical equipment |
When selecting between the two, SUS 304 is often preferred for indoor and general industrial use, while SUS 316 is better suited for harsher, marine, or chemical environments.
7. Fabrication and Welding Characteristics
Fabricators value SUS 304 for its excellent weldability, machinability, and formability. It can be easily welded using all standard fusion techniques, including TIG, MIG, and resistance welding.
For thicker sections, low-carbon variants like SUS 304L are recommended to reduce the risk of carbide precipitation and maintain corrosion resistance after welding.
Other key fabrication notes:
- Avoid contamination with carbon steel tools.
- Use dedicated brushes and grinding wheels.
- Apply post-weld cleaning or pickling to remove heat tint and restore the protective film.
These practices ensure that the final product maintains both aesthetic quality and long-term corrosion performance.
8. Applications of SUS 304 Stainless Steel
The versatility of SUS 304 makes it a preferred material across numerous industries:
Industrial Applications
- Food processing tanks and machinery
- Heat exchangers, piping systems, and pressure vessels
- Chemical containers and storage units
Commercial and Architectural Applications
- Building facades, handrails, and structural supports
- Elevator panels, kitchen appliances, and decorative finishes
Consumer Goods
- Cookware, cutlery, and household fixtures
- Medical equipment and laboratory devices
Its balance of strength, formability, and corrosion resistance ensures performance in both functional and aesthetic applications.
9. Global Standards and Material Equivalents
Manufacturers worldwide rely on SUS 304 stainless steel and its equivalents. Below are some standard designations used globally:
- JIS G4303 – SUS304 (Japan)
- ASTM A240 / A276 – Type 304 (USA)
- EN 10088 – 1.4301 (Europe)
- GB/T 20878 – 06Cr19Ni10 (China)
Understanding these equivalents allows engineers to source compatible materials from different regions without compromising on quality or performance.
10. Conclusion
SUS 304 stainless steel remains one of the most widely used and trusted materials in the world. Its combination of durability, corrosion resistance, and cost efficiency makes it suitable for countless applications — from industrial fabrication to everyday consumer products.
Although it shares its characteristics with SS304, the Japanese designation highlights the same exceptional quality that has made this grade a global standard for stainless steel production.
Whether used in architectural designs, food processing plants, or high-precision equipment, SUS 304 continues to set the benchmark for reliability and performance in stainless steel engineering.