What is SUS 304 Stainless Steel: Properties, Differences, and Applications

  • Nov, Tue, 2025
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Stainless steel is one of the most widely used metals in modern industry due to its excellent corrosion resistance, strength, and versatility. Among the various grades, SUS 304 stainless steel stands out as a popular choice for a wide range of applications. But what exactly is SUS 304 stainless steel, and why is it preferred in so many industries?

In this article, we will explore the definition, chemical composition, mechanical properties, corrosion resistance, differences from SS304, applications, advantages, and limitations of SUS 304. Understanding these factors helps engineers, designers, and manufacturers make informed choices when selecting materials for industrial and commercial projects.

What is SUS 304 Stainless Steel?

SUS 304 stainless steel is a type of austenitic stainless steel defined under the Japanese Industrial Standard (JIS). The acronym “SUS” stands for “Steel Use Stainless,” and the “304” denotes the specific grade. SUS 304 belongs to the austenitic family, known for its excellent formability, ductility, and corrosion resistance.

In international standards, the equivalent grade is SS304, commonly referenced in ASTM and AISI standards. While the naming differs, the chemical composition, mechanical properties, and performance characteristics of SUS 304 and SS304 are largely identical. This equivalence allows for flexibility in sourcing and cross-border projects.

Chemical Composition of SUS 304

The typical chemical composition of SUS 304 stainless steel is carefully controlled to ensure its strength and corrosion resistance:

  • Chromium (Cr): 18–20% – forms a protective oxide layer for corrosion resistance

  • Nickel (Ni): 8–10.5% – stabilizes the austenitic structure and improves ductility

  • Carbon (C): ≤0.08% – maintains strength while reducing carbide precipitation

  • Manganese (Mn), Silicon (Si), Phosphorus (P), Sulfur (S): present in small amounts for processing and performance stability

  • Iron (Fe): serves as the base metal

The balance of these elements gives SUS 304 stainless steel its characteristic corrosion resistance, mechanical strength, and formability. Proper chemical control is essential for achieving the expected performance in different environments.

Mechanical Properties

SUS 304 is known for its excellent mechanical properties, which make it suitable for a variety of applications:

  • Austenitic Structure: Provides high ductility and toughness even at low temperatures

  • Tensile Strength and Yield Strength: High enough to withstand mechanical stress in structural and industrial components

  • Elongation: Typically ≥ 40%, allowing for effective forming and shaping

  • Fabrication Flexibility: Can be cold worked or hot worked to improve strength or shape components

  • Weldability: SUS 304 can be easily welded using TIG, MIG, and other techniques, making it suitable for complex assemblies

These mechanical properties make SUS 304 an ideal choice for components that require both durability and precision.

Corrosion Resistance

One of the most important features of SUS 304 stainless steel is its corrosion resistance:

  • Passive Chromium Oxide Layer: The chromium content forms a thin, protective oxide layer on the surface that prevents rusting and oxidation

  • Typical Environments: SUS 304 performs well in atmospheric, freshwater, and many industrial environments

  • Limitations: In chloride-rich environments, such as seawater or salt-laden air, SUS 304 may experience pitting or crevice corrosion

  • Comparison with Higher Grades: For highly corrosive environments, grades like SUS 316 are preferred due to higher resistance to chloride attack

With proper design and maintenance, SUS 304 provides long-lasting performance in a wide range of applications.

SUS 304 vs SS304 – Key Differences

While SUS 304 and SS304 are often used interchangeably, there are subtle distinctions:

  • Standard Systems: SUS 304 follows the Japanese JIS standard, whereas SS304 follows the American ASTM/AISI standards

  • Chemical Composition and Properties: Largely identical; both offer similar corrosion resistance, strength, and ductility

  • Global Sourcing: Understanding the equivalence is important for international projects and procurement

  • Material Certification: Ensure that material certificates (MTRs) comply with the required standard to avoid quality issues

This knowledge is crucial for engineers and purchasing teams managing cross-border projects or sourcing components globally.

Applications of SUS 304 Stainless Steel

SUS 304 stainless steel is widely used across various industries due to its versatility:

  1. Kitchen & Home Appliances

    • Sinks, cookware, cutlery, and other kitchen fixtures benefit from SUS 304’s corrosion resistance and ease of cleaning

  2. Food Processing Equipment

    • SUS 304 is commonly used in food-grade containers, conveyor systems, and processing machinery

  3. Construction & Architecture

    • Pipes, structural supports, and decorative metal elements utilize its strength and aesthetic appeal

  4. Medical Devices

    • Surgical instruments, laboratory equipment, and medical devices rely on SUS 304 for hygiene, strength, and corrosion resistance

  5. Industrial Equipment

    • Valves, pumps, and machinery components take advantage of SUS 304’s mechanical properties and durability

Its wide-ranging applications demonstrate the reliability and versatility of SUS 304 in both industrial and commercial contexts.

Advantages and Limitations

Advantages:

  • Excellent corrosion resistance in most environments

  • High ductility, toughness, and formability

  • Good weldability for complex assemblies

  • Cost-effective compared to higher alloy stainless steels like SUS 316

Limitations:

  • Susceptible to chloride-induced corrosion in seawater or high-salt environments

  • Welded areas may require passivation to maintain corrosion resistance

  • Not ideal for extremely harsh chemical or high-temperature applications

Understanding these advantages and limitations helps engineers choose SUS 304 for the right projects, balancing cost, performance, and longevity.

Conclusion

SUS 304 stainless steel is a highly versatile and widely used material in modern industry. Its combination of corrosion resistance, mechanical strength, ductility, and ease of fabrication makes it ideal for applications ranging from kitchen appliances to medical devices and industrial equipment. While similar to SS304 in chemical composition and performance, SUS 304 follows the Japanese JIS standard, making standard verification important in international projects.

For most industrial and commercial environments, SUS 304 provides a reliable, cost-effective, and high-performance solution. When considering material selection, engineers should account for environmental factors, welding practices, and required standards to ensure the optimal performance of SUS 304 components.