Stainless Steel 304 (SUS304) Specifications & Guide

If you walk into any industrial plant, pharmaceutical facility, or commercial kitchen, approximately 70% of the stainless steel you see is Grade 304 (or SUS304 under Japanese JIS G4305 standards). Although it is the most common grade in the market, from an engineering perspective, it represents the ultimate balance of properties. In this article, Trinity Dynamic unpacks the "Technical Specifications" to reveal what exactly makes up Grade 304 and why it remains the most cost-effective choice.

1. Chemical Composition

The secret to its exceptional rust resistance lies in its precise alloy formulation. According to the ASTM A240 standard, the composition for Grades 304 and 304L is specified as follows:

Element	Type 304 (%)	Type 304L (%)	Primary Metallurgical Function
Chromium (Cr)	18.0 - 20.0	18.0 - 20.0	Reacts with oxygen to form the self-healing passive film
Nickel (Ni)	8.0 - 10.5	8.0 - 12.0	Enhances ductility and elasticity for easy cold-forming
Carbon (C)	Max 0.08	Max 0.03	Provides tensile strength (Lower in "L" grades to improve weldability)

*Should you choose Grade 304 or 304L for your fabrication project? Read our comprehensive comparison guide here: 304 vs 304L In-Depth Comparison

2. Mechanical Properties

For structural engineers and draftsmen, these mechanical values are critical for safe load-bearing and stress-limit calculations:

Tensile Strength (Maximum load before fracturing): ≥ 515 MPa (Excellent load resistance)
Yield Strength (Elastic limit of deformation): ≥ 205 MPa
Elongation (Maximum stretching limit): ≥ 40% (Highly ductile, bends smoothly without cracking)
Hardness (Indent resistance): ≤ 201 HB (Not overly brittle)

3. Grade 304 Product Forms We Supply

Trinity Dynamic stocks Grade 304 in every shape to meet the demands of any industry at factory-direct wholesale pricing:

1. Flat Products (Plates & Sheets)

2B Finish: The standard for mixing tanks, food prep counters, and enclosures
No.1 Finish: Heavy-duty hot-rolled plate for industrial silos, flanges, and bases
Hairline & Mirror (HL/No.8): Pre-coated with premium protective film for elevators and luxury decor

2. Long Products (Bars & Tubes)

Solid Round Bars: High-precision shafts, bushings, and fasteners
Equal Angles & Flat Bars: Rigid frameworks, handrails, and industrial platforms
Hollow Sections: Both Industrial Pipes (A312) and Ornamental Tubes (A554)

Conclusion: Why is 304 the Undisputed "King of Stainless Steel"?

It represents the absolute perfect intersection of Price and Performance. Unless your application is located near corrosive marine environments or involves extremely aggressive acids (which strictly requires Grade 316L), Stainless Steel 304 remains the most cost-effective and highly reliable material choice globally.

Need Mill Test Certificates (MTC) for Grade 304?

We guarantee the absolute quality of our materials. Every single production lot of Grade 304 we deliver comes with its original, verified ASTM A240 / JIS G4305 certificate. We offer professional shearing, custom bandsaw cut-to-length, and CNC Plasma cutting services, along with secure nationwide delivery across Thailand.

Request a Quote & Spec Sheet Now

Frequently Asked Questions (FAQ)

The main difference is the carbon content. Grade 304 allows a maximum carbon content of 0.08%, whereas Grade 304L (L = Low Carbon) strictly limits carbon to a maximum of 0.03%. The primary benefit of using Grade 304L is that it prevents 'Weld Decay' (sensitization/carbide precipitation) near welded joints, preserving corrosion resistance after welding without needing post-weld annealing.

Grade 304 belongs to the Austenitic family, which is naturally non-magnetic. However, when the material undergoes severe cold-forming processes on the workshop floor—such as deep drawing, roll-forming, or tight bending—the local crystal structure at the bent area transforms from non-magnetic austenite to magnetic martensite. This is a normal physical reaction and does not indicate fake or low-quality steel.

Yes, Grade 304 can rust under harsh environmental conditions. The most common cause is exposure to high-salinity marine environments or concentrated chlorides (like bleach/salt brines), which break down the protective chromium oxide film. Another major cause is cross-contamination, which occurs when fabricators use grinding wheels or brushes previously used on carbon steel, leaving iron particles embedded in the stainless surface.

They are chemically identical. SUS304 is the designation used by the Japanese Industrial Standards (JIS G4305), whereas Grade 304 refers to the American Society for Testing and Materials (ASTM A240) standard. Both contain roughly 18% Chromium and 8% Nickel and are fully interchangeable in industrial specifications.

Yes, absolutely. Grade 304 is the global standard for food and beverage contact. Its high nickel-chromium composition makes it highly non-reactive to organic acids, preventing heavy metals from leaching into food. For maximum hygiene, we recommend smooth finishes like 2B or BA to ensure easy washdown and complete sanitization.

At Trinity Dynamic, we provide precision Shearing for flat sheets to ensure straight, burr-free edges, custom Bandsaw Cut-to-Length services to reduce material scrap, and heavy-duty CNC Plasma profile cutting for thick plates. We support all shipments with Mill Test Certificates (MTC) and offer secure nationwide delivery across Thailand.