Stainless steel is widely used in industries ranging from construction and kitchenware to medical and chemical equipment. Its versatility, durability, and corrosion resistance make it a top choice for engineers, architects, and manufacturers alike. Among the various grades, stainless steel SUS304 stands out for its excellent balance of mechanical properties and corrosion resistance. However, many people often wonder how it differs from SS304 and why understanding these differences matters. In this article, we explore the properties, applications, and distinctions of SUS304, providing a comprehensive guide for professionals and enthusiasts.

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What is SUS304 Stainless Steel?

SUS304 is a type of austenitic stainless steel defined under the Japanese Industrial Standards (JIS). The abbreviation “SUS” stands for Steel Use Stainless, indicating that it is a stainless steel suitable for general-purpose applications.

The composition of SUS304 typically includes:

• Chromium (Cr): 18–20%

• Nickel (Ni): 8–10.5%

• Carbon (C): ≤0.08%

• Other elements: Manganese (Mn), Silicon (Si), Phosphorus (P), Sulfur (S) in trace amounts

The austenitic crystal structure gives SUS304 excellent ductility, formability, and corrosion resistance. These characteristics make it ideal for manufacturing thin sheets, tubes, and complex components without compromising durability.

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SS304 vs SUS304: Key Differences

While SUS304 and SS304 refer to the same type of stainless steel, the key difference lies in the standards used for classification:

• SUS304 follows the Japanese Industrial Standards (JIS).

• SS304 adheres to American (AISI/ASTM) standards.

Chemically, both are nearly identical, with only minor variations due to regional standard tolerances. Mechanically, they share comparable properties:

• Tensile Strength: 515–750 MPa

• Yield Strength: ≥205 MPa

• Elongation: ≥40%

• Hardness (HRB): Similar in annealed condition

Due to these similarities, SUS304 and SS304 are largely interchangeable in most applications. However, for international projects, confirming the applicable standard and obtaining the proper material test certificate (MTR) is essential to ensure compliance.

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Properties of SUS304

SUS304 offers several advantages that make it widely used in multiple industries:

1. Corrosion Resistance
   The chromium and nickel content forms a passive oxide layer on the surface, protecting the metal from oxidation and many forms of chemical corrosion.

2. Formability
   Its austenitic structure allows cold forming, stamping, bending, and deep drawing without cracking.

3. Mechanical Strength
   SUS304 provides a good balance of strength and ductility, making it suitable for both structural components and thin sheet applications.

4. Maintenance and Durability
   It is easy to clean, highly durable, and has a long service life, which is critical for kitchen, medical, and industrial equipment.

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Factors to Consider When Choosing SUS304

Selecting SUS304 requires consideration of several factors:

• Environment: While SUS304 is corrosion-resistant, high-chloride environments (like marine settings) may cause pitting or crevice corrosion.

• Standards and Certification: Ensure the material meets the required JIS or ASTM standard and that the MTR is available.

• Engineering Requirements: Consider strength, elongation, weldability, and surface finish needed for your application.

By understanding these factors, engineers can select the right stainless steel grade for maximum performance and longevity.

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Applications of SUS304

SUS304’s versatility has made it a staple across various industries:

1. Kitchen and Food Industry

   • Sinks, cutlery, cookware, food processing equipment

   • Benefits: corrosion resistance, hygiene, and easy cleaning

2. Construction and Architecture

   • Facades, handrails, decorative panels

   • Benefits: aesthetic appeal and durability

3. Chemical and Pharmaceutical Equipment

   • Storage tanks, pipelines, valves

   • Benefits: resistance to many chemicals and ease of fabrication

4. Medical and Laboratory Equipment

   • Surgical instruments, lab benches, and equipment

   • Benefits: corrosion resistance and sterilization capability

SUS304’s combination of corrosion resistance, strength, and workability ensures it meets stringent industry requirements.

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Advantages and Limitations

Advantages:

• Excellent corrosion resistance in most environments

• Good formability and weldability

• Durable and easy to maintain

• Suitable for both structural and aesthetic applications

Limitations:

• Susceptible to pitting in high-chloride environments

• Material standard must be verified for international projects

• For highly aggressive environments, higher-grade stainless steels like SUS316 may be required

Understanding these pros and cons ensures correct material selection, avoiding potential issues in service.

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Conclusion

Stainless steel SUS304 is a high-performance austenitic stainless steel widely used in industrial, architectural, and household applications. While it is nearly identical to SS304 in chemical composition and mechanical performance, the distinction lies in the regional standard—JIS for SUS304 and ASTM/AISI for SS304.

Selecting SUS304 requires considering environmental conditions, mechanical requirements, and certification standards. Its corrosion resistance, ductility, and ease of fabrication make it ideal for kitchens, chemical plants, medical equipment, and architectural components. Correctly understanding the properties and limitations of SUS304 ensures durable, safe, and efficient applications in any industry.

By mastering the differences and applications of stainless steel SUS304, engineers and designers can make informed decisions that optimize performance, durability, and compliance across international projects.