SUS304 vs SS304 Stainless Steel: Key Differences, Applications & Which One to Choose
Explore the differences between SUS304 and SS304 stainless steel, their chemical compositions, mechanical properties, and applications. Learn how to choose the right material for your project and how CSMFG can support your manufacturing needs.
SUS304 vs SS304 Stainless Steel: Key Differences, Applications & Which One to Choose
Stainless steel is one of the most versatile and widely used materials across industries, particularly for its corrosion resistance, strength, and ease of fabrication. Among the many grades of stainless steel, SUS304 and SS304 are two of the most commonly encountered. These materials are often confused due to their similar composition and properties, but there are key differences in the naming conventions, regional standards, and applications.
In this blog, we’ll break down the differences between SUS304 and SS304, compare their chemical compositions, mechanical properties, and typical applications, and provide insights on when to choose one over the other. Additionally, we’ll discuss how CSMFG can help meet your stainless steel needs with custom fabrication solutions.
What is SUS304 Stainless Steel?
SUS304 is a grade of stainless steel defined by the Japanese Industrial Standards (JIS). The “SUS” prefix stands for “Steel Use Stainless,” and this grade is essentially the Japanese version of AISI 304 stainless steel, with the same chemical composition and mechanical properties.
SUS304 is primarily used in Japan and other parts of Asia for applications requiring corrosion resistance, high strength, and formability. It’s commonly found in industries such as food processing, kitchen equipment, and chemical storage.
Common Applications of SUS304:
- Food processing equipment
- Kitchen sinks and utensils
- Building facades and structural components
- Chemical containers and tanks
SUS304 is renowned for its durability in both high and low-temperature environments, making it a versatile choice for various industrial and consumer applications.
What is SS304 Stainless Steel?
On the other hand, SS304 refers to the same grade of stainless steel, but under the American Iron and Steel Institute (AISI) and ASTM standards. SS304 is primarily used in North America and Europe and is considered the default grade for a wide range of applications.
Just like SUS304, SS304 belongs to the 18/8 family of austenitic stainless steels, meaning it contains approximately 18% chromium and 8% nickel. This composition provides excellent resistance to oxidation and corrosion, especially in mild environments.
Common Applications of SS304:
- Medical and pharmaceutical equipment
- Food and beverage processing tools
- Architectural finishes
- Household appliances
In the US and Europe, SS304 is often the baseline against which other stainless steel grades are measured, thanks to its balance of performance, affordability, and availability.
SUS304 vs SS304: Chemical Composition Comparison
The primary reason for confusion between SUS304 and SS304 is that their chemical compositions are nearly identical. Both grades belong to the 18/8 stainless steel family, which means they contain:
- 18% Chromium (Cr)
- 8% Nickel (Ni)
- Other elements like Manganese (Mn), Silicon (Si), Phosphorus (P), and Sulfur (S) in trace amounts.
| Element | SUS304 (JIS G4303) | SS304 (ASTM A240) |
|---|---|---|
| Carbon (C) | ≤ 0.08% | ≤ 0.08% |
| Chromium (Cr) | 18.0–20.0% | 18.0–20.0% |
| Nickel (Ni) | 8.0–10.5% | 8.0–10.5% |
| Manganese (Mn) | ≤ 2.0% | ≤ 2.0% |
| Silicon (Si) | ≤ 1.0% | ≤ 1.0% |
| Phosphorus (P) | ≤ 0.045% | ≤ 0.045% |
| Sulfur (S) | ≤ 0.03% | ≤ 0.03% |
The slight differences that may exist between the two materials are mainly due to regional tolerances, not intentional mechanical distinctions.
Mechanical Properties Comparison
In terms of mechanical properties, SUS304 and SS304 behave nearly identically under typical testing conditions. Both materials have an austenitic microstructure, which gives them their high toughness and strength. Below is a comparison of the typical mechanical properties:
| Property | Typical Value (Both SUS304 & SS304) |
|---|---|
| Tensile Strength | 515 – 750 MPa |
| Yield Strength | ≥ 205 MPa |
| Elongation (in 50mm) | ≥ 40% |
| Hardness (HRB) | ≤ 92 (annealed) |
| Corrosion Resistance | Excellent in oxidizing environments |
| Weldability | Excellent |
| Formability | Good |
Both grades are non-magnetic in the annealed condition, although some slight magnetism can develop after cold working. Their excellent corrosion resistance and ductility make them ideal for complex manufacturing processes such as deep drawing, bending, and spot welding.
Additionally, both grades offer superior weldability, which is essential for applications requiring fabricated structures. Their high nickel content helps reduce brittleness in the heat-affected zone, ensuring that post-weld mechanical strength is retained.
How to Choose Between SUS304 and SS304?
While SUS304 and SS304 are technically the same material, the choice between the two typically comes down to regional standards and sourcing preferences.
- Choose SUS304 if you are working within Asia, especially Japan, where JIS standards dominate.
- Choose SS304 if you are sourcing materials for projects in North America or Europe, where ASTM standards are prevalent.
Key Factors to Consider:
- Geographic Sourcing:
- SUS304 is more cost-efficient in Japan and other Asian markets, while SS304 is the preferred option in the US and Europe.
- Certification and Compliance:
- Ensure that the material meets the specific standards required by the project’s location or industry. For international projects, always verify material equivalency tables and certification documents.
- Application Needs:
- For critical applications, pre-production testing may be necessary to confirm that the material meets all performance requirements, regardless of whether it’s SUS304 or SS304.
Applications: Are They Really That Different?
In most cases, the SUS304 vs SS304 debate comes down to regional sourcing rather than significant performance differences. The two grades are essentially interchangeable, as long as you ensure that the material meets the required standards and certifications.
At CSMFG, we work with both SUS304 and SS304, providing custom stainless steel fabrication services that meet JIS, ASTM, and other international standards. Whether you’re looking for bending, machining, or welding solutions, we can deliver high-quality products that meet your specifications.
Why Choose CSMFG for Your Stainless Steel Needs?
At CSMFG, we offer ISO-certified stainless steel fabrication services that support international standards, including JIS, ASTM, and DIN. We understand the nuances of working with different stainless steel grades, including SUS304 and SS304, and can provide tailored solutions for your specific project needs.
If you need SUS304 or SS304 components customized to your specifications, or if you’re looking for assistance in navigating material certifications and standards, CSMFG is here to help.
Contact Us Today!
For more information or to request a custom quote, visit our website at CSMFG.com or contact our expert team directly.