SUS304 Material: Composition, Properties, and Applications Explained
Discover everything about SUS304 material — its chemical composition, mechanical properties, corrosion resistance, and industrial applications. Learn why SUS304 remains one of the most widely used stainless steels in global manufacturing.
What Is SUS304 Material?
SUS304 material is one of the most common types of austenitic stainless steel used across various industries worldwide. Known for its excellent corrosion resistance, high strength, and formability, it is the go-to choice for products ranging from kitchen equipment to industrial machinery.
The term “SUS304” originates from the Japanese Industrial Standard (JIS), where “SUS” stands for Steel Use Stainless. In the United States and Europe, this same alloy is referred to as SS304 or AISI 304. Although the names differ, the composition and performance are practically identical. Understanding this equivalence is essential for global sourcing and engineering standardization.
Origin and Standard of SUS304
The SUS304 material follows the JIS G4303 standard in Japan. This standard defines the allowable chemical composition, mechanical properties, and heat treatment conditions. Meanwhile, the American equivalent—AISI 304 or ASTM A240 Type 304—follows U.S. specifications.
While the naming conventions differ, both materials share similar metallurgical characteristics. Engineers and procurement specialists should always verify which standard applies to a specific project, as documentation requirements, such as Mill Test Reports (MTRs), may vary.
In international projects, SUS304 is often interchangeable with SS304, but ensuring compliance with the correct standard is critical to avoid quality or certification issues.
Chemical Composition of SUS304 Material
SUS304 material is a chromium-nickel alloy that achieves corrosion resistance through the formation of a passive oxide film on its surface. The typical chemical composition under JIS G4303 is as follows:
| Element | Percentage (%) | Function |
|---|---|---|
| Carbon (C) | ≤ 0.08 | Improves strength but reduces weldability |
| Chromium (Cr) | 18.0 – 20.0 | Enhances corrosion resistance |
| Nickel (Ni) | 8.0 – 10.5 | Improves toughness and ductility |
| Manganese (Mn) | ≤ 2.0 | Aids in deoxidation and improves strength |
| Silicon (Si) | ≤ 1.0 | Improves oxidation resistance |
| Phosphorus (P) | ≤ 0.045 | Kept low to maintain toughness |
| Sulfur (S) | ≤ 0.03 | Enhances machinability but must be limited |
This balanced composition makes SUS304 one of the most versatile and reliable stainless steels for both structural and aesthetic applications.
Mechanical and Physical Properties
The mechanical properties of SUS304 material make it suitable for forming, welding, and machining. Below are the typical values:
- Tensile Strength: 520–750 MPa
- Yield Strength (0.2% Proof): ≥ 205 MPa
- Elongation: ≥ 40%
- Hardness: ≤ 187 HB
- Density: 7.93 g/cm³
- Melting Point: 1400–1450°C
When annealed, SUS304 is non-magnetic, but after cold working, it can exhibit slight magnetism. This characteristic is often used to distinguish between annealed and work-hardened states.
The combination of strength, ductility, and non-magnetic behavior makes it ideal for both industrial and consumer applications.
Corrosion Resistance and Surface Behavior
A major advantage of SUS304 material is its excellent resistance to corrosion. Thanks to its chromium and nickel content, it can resist oxidation in both atmospheric and chemical environments. This makes it suitable for use in humid conditions, food processing, and general industrial exposure.
However, SUS304 is not completely immune to chloride-induced corrosion. In environments with high concentrations of chlorides—such as coastal areas or swimming pools—it may suffer from pitting or crevice corrosion. In such cases, engineers often switch to SUS316, which contains molybdenum for enhanced protection.
Surface treatments such as passivation, electropolishing, or mirror finishing can further improve the corrosion resistance and aesthetics of SUS304. These processes remove impurities and strengthen the protective oxide layer.
Common Applications of SUS304 Material
The versatility of SUS304 material has made it a staple across countless industries. Its balance of strength, corrosion resistance, and affordability supports its widespread use in:
1. Food and Beverage Industry
SUS304 is approved for contact with food and beverages, making it perfect for kitchen sinks, cookware, brewing tanks, and dairy equipment. Its smooth surface prevents bacterial accumulation and ensures easy cleaning.
2. Chemical and Pharmaceutical Equipment
Tanks, pipelines, and reactors made from SUS304 resist corrosion caused by acids, alkalis, and solvents. This makes it a safe and durable choice for chemical processing plants.
3. Construction and Architecture
In modern architecture, SUS304 is widely used for facades, handrails, claddings, and roofing systems due to its elegant appearance and long-lasting surface finish.
4. Automotive and Mechanical Components
The material’s formability and strength make it suitable for exhaust systems, fasteners, and brackets. Its corrosion resistance also ensures longer service life under harsh environmental conditions.
5. Household Appliances
Refrigerator panels, washing machine drums, and kitchen utensils are often made from SUS304 because it combines durability with a polished, high-end look.
SUS304 vs SS304 — Understanding the Difference
Although often discussed as separate materials, SUS304 and SS304 are essentially identical in composition and performance. The primary difference lies in regional naming conventions:
- SUS304 → Defined by JIS (Japanese Industrial Standard)
- SS304 / AISI 304 → Defined by ASTM / AISI (American Standards)
From a metallurgical perspective, both materials share the same chromium-nickel ratios and mechanical properties. Therefore, they are often interchangeable in design and manufacturing.
However, engineers should always verify that the supplier’s material certification (MTR) aligns with the required standard to ensure compliance in global projects.
Processing and Fabrication of SUS304 Material
SUS304 material can be easily formed, welded, and machined, offering excellent versatility during fabrication.
- Cold Working: Enhances strength through strain hardening; suitable for deep drawing or stamping.
- Welding: Compatible with TIG, MIG, and resistance welding methods. Low-carbon variants like SUS304L help prevent carbide precipitation during welding.
- Heat Treatment: Annealing at 1010–1120°C followed by rapid cooling restores ductility and removes internal stress.
- Surface Finishing: Brushed, mirror, or matte finishes improve corrosion resistance and visual appeal.
Its adaptability in manufacturing makes it ideal for producing components that require both functional and aesthetic performance.
Advantages and Limitations
Advantages
- Excellent corrosion resistance in various environments
- High ductility and good mechanical strength
- Non-magnetic after annealing
- Easy to weld and process
- Attractive surface finish for decorative purposes
Limitations
- Susceptible to chloride corrosion in salt-rich environments
- Not ideal for high-temperature, long-term applications above 870°C
- More expensive than carbon steel alternatives
These factors must be evaluated when selecting materials for cost-sensitive or harsh-environment projects.
Tips for Choosing SUS304 Material
- Assess the environment: Determine exposure to moisture, chlorides, or chemicals to ensure SUS304 is appropriate.
- Verify standards: Always check if your project requires JIS (SUS304) or ASTM (SS304) certification.
- Request MTRs: Ask suppliers for material certificates detailing chemical composition and test results.
- Consider alternatives: For improved resistance, use SUS316 or 316L when higher corrosion resistance is needed.
Selecting the right stainless steel grade ensures reliability, safety, and compliance in every application.
Conclusion — Why SUS304 Material Remains a Global Standard
SUS304 material continues to dominate the stainless steel market due to its remarkable balance of strength, corrosion resistance, and cost efficiency. Whether in food-grade equipment, architectural designs, or heavy industrial applications, it delivers consistent performance with minimal maintenance.
While the distinction between SUS304 and SS304 mainly lies in naming conventions, understanding their equivalence helps engineers make smarter procurement and design decisions.
In essence, SUS304 material represents the foundation of modern stainless steel engineering—an alloy trusted worldwide for its durability, versatility, and timeless reliability.