What Is SUS304? Understanding Its Properties, Differences, and Applications

  • Nov, Tue, 2025
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Stainless steel has become one of the most widely used materials in modern manufacturing due to its excellent corrosion resistance, mechanical strength, and versatility. Among the various grades of stainless steel, SUS304 is one of the most popular. For engineers, manufacturers, and procurement specialists, understanding what is SUS304 is essential to ensure proper material selection, compliance with standards, and optimal performance in applications ranging from industrial components to consumer goods. This article explores the definition, chemical composition, mechanical properties, differences from SS304, applications, and considerations for using SUS304 in modern manufacturing.

1. Introduction to SUS304 Stainless Steel

The term SUS304 originates from the Japanese Industrial Standard (JIS), where “SUS” stands for “Steel Use Stainless” and 304 refers to the specific alloy composition. Essentially, SUS304 is Japan’s standard designation for what is commonly known in Western countries as SS304. This grade belongs to the austenitic stainless steel family, characterized by its face-centered cubic (FCC) crystal structure, which contributes to its excellent ductility, corrosion resistance, and formability.

SUS304 is widely used in both industrial and consumer applications due to its ability to withstand a wide range of environmental conditions. Understanding what is SUS304 helps manufacturers select materials that provide durability, reliability, and compliance with both Japanese and international standards.

2. Chemical Composition of SUS304

SUS304 is an 18‑8 stainless steel alloy, meaning it contains approximately 18% chromium (Cr) and 8% nickel (Ni). The chromium provides corrosion resistance by forming a passive oxide layer on the surface, while nickel enhances the steel’s toughness and ductility. Minor elements such as carbon, manganese, silicon, and phosphorus may also be present in trace amounts to improve mechanical properties and manufacturability.

The typical chemical composition of SUS304 is:

  • Chromium (Cr): 17.5–18.5%

  • Nickel (Ni): 8–10%

  • Carbon (C): ≤0.08%

  • Manganese (Mn): ≤2%

  • Silicon (Si): ≤1%

  • Phosphorus (P): ≤0.045%

  • Sulfur (S): ≤0.03%

This composition allows SUS304 to maintain a balance of corrosion resistance, strength, and formability, making it suitable for a wide variety of applications.

3. Mechanical Properties of SUS304

SUS304 exhibits excellent mechanical properties that contribute to its versatility in manufacturing:

  • Tensile Strength: Approximately 520–750 MPa

  • Yield Strength: Around 205–215 MPa

  • Elongation at Break: 40–60%, indicating good ductility

  • Hardness: Typically 70–90 HRB

These properties make SUS304 resistant to deformation under normal use conditions, yet still formable enough for processes such as bending, drawing, and deep drawing. Its austenitic structure also ensures that the steel remains tough at low temperatures, which is important for components exposed to varying environmental conditions.

4. SUS304 vs SS304: Key Differences

One common question is whether SUS304 is different from SS304. The answer is that both are essentially the same alloy, but they are governed by different standards:

  • SUS304: Japanese JIS standard

  • SS304: American AISI/ASTM standard

The chemical compositions of SUS304 and SS304 are almost identical, and their mechanical properties are comparable. In most practical applications, these two grades can be used interchangeably. However, there are minor differences in allowable tolerances, trace elements, and certification requirements depending on the standard. For global sourcing or international projects, it is crucial to specify the standard to ensure consistency in quality, testing, and compliance.

5. Applications of SUS304 Stainless Steel

The combination of corrosion resistance, formability, and strength makes SUS304 highly versatile. Common applications include:

  • Industrial Components: Tanks, heat exchangers, piping, and pressure vessels

  • Construction and Architecture: Handrails, cladding, staircases, and structural components

  • Consumer Goods: Kitchen appliances, cookware, cutlery, and medical instruments

  • Automotive and Aerospace: Exhaust systems, brackets, and structural supports

The ability to fabricate SUS304 into sheets, tubes, rods, and complex shapes without losing structural integrity makes it ideal for manufacturing processes that require precision and durability.

6. Advantages of SUS304 Stainless Steel

SUS304 offers several advantages that contribute to its widespread use:

  • Corrosion Resistance: The chromium content protects against rust and oxidation in various environments.

  • Formability: Its austenitic structure allows bending, drawing, and deep drawing without cracking.

  • Weldability: Can be welded without significant loss of corrosion resistance, making it suitable for structural and industrial assemblies.

  • Durability: Maintains mechanical properties over a wide range of temperatures and environmental conditions.

  • Hygienic Properties: Non-porous surface is ideal for food processing and medical applications.

These features make SUS304 a reliable choice for both heavy industrial use and high-end consumer products.

7. Considerations When Using SUS304

While SUS304 is highly versatile, there are important considerations:

  • Standard Compliance: Ensure that the material meets the required standard (JIS for SUS304, ASTM/AISI for SS304) and comes with a material certificate.

  • Environmental Conditions: In highly chlorinated or marine environments, consider higher-grade stainless steel (e.g., SUS316) for improved corrosion resistance.

  • Surface Treatment: Depending on the application, SUS304 may require polishing, passivation, or coating to enhance corrosion resistance and aesthetics.

  • Mechanical Processing: When bending, forming, or welding, follow proper guidelines to maintain material integrity and avoid defects such as stress corrosion cracking.

Proper handling and quality control ensure that SUS304 components perform reliably over time.

8. Common Misconceptions

  • SUS304 is not a completely different alloy from SS304. They are chemically and mechanically equivalent; differences are mainly in naming and standards.

  • Interchangeability is possible, but specifying the standard is critical for certification, testing, and compliance purposes.

  • Some assume that SUS304 is weaker or less corrosion-resistant; in reality, it meets or exceeds performance requirements of SS304 in most environments.

9. Conclusion

Understanding what is SUS304 is essential for engineers, manufacturers, and procurement specialists. SUS304 is a Japanese standard designation for 304 stainless steel, widely recognized for its corrosion resistance, formability, and mechanical strength. While minor differences exist between SUS304 and SS304, in most practical applications they are interchangeable. Its versatility in industrial, architectural, consumer, and medical applications makes it one of the most popular stainless steel grades worldwide.

Proper material selection, standard compliance, and quality control are critical when working with SUS304. By knowing its properties, advantages, and limitations, manufacturers can design and produce components that are reliable, durable, and suited for a variety of challenging environments.