In stainless steel procurement and engineering projects, SS304L and SUS304L are frequently searched but often misunderstood grades. Common customer questions include:
Are SS304L and SUS304L the same material?
Why do they look the same but follow different standards?
Which one should be specified in export documents, tenders, or engineering drawings?
This article will explain the differences between SS304L and SUS304L, covering standards, chemical composition, mechanical properties, applications, and frequently asked questions from buyers.
What is the difference between SS304L and SUS304L?
SS304L and SUS304L refer to the same low-carbon stainless steel alloy, with "SS" (American/International) and "SUS" (Japanese JIS standard) simply indicating the naming standard, while the "L" signifies low carbon (≤0.03%), making it superior for welded applications needing corrosion resistance without post-weld treatment, unlike regular 304 (≤0.08% carbon).
What is the meaning of SS304L?
SS304L is a low-carbon version of the widely used 304 stainless steel, characterized by excellent corrosion resistance, strength, and fabricability, especially improved weldability due to its low carbon content (max 0.03%) preventing carbide precipitation, making it ideal for heavy-gauge components in food processing, chemical, and aerospace applications.
What is SUS304L material?
SUS304L, a low carbon version of SUS304, is highly resistant to intergranular corrosion. Because the precipitation of carbides is minimized during welding, SUS304L can maintain the corrosion resistance without any post-weld heat treatment. Post-weld annealing is required only for use under high stress conditions.
SS304L and SUS304L ：Standard System Comparison
| Item | SS304L | SUS304L |
|---|---|---|
| Standard System | ASTM / AISI | JIS |
| Common Standards | ASTM A240 / A276 / A312 | JIS G4303 / G4304 / G4305 |
| Grade Designation | 304L | SUS304L |
| Global Acceptance | Very High | High (Asia-focused) |
SS304L and SUS304L ：Chemical Composition (wt.%)
| Element | SS304L (ASTM) | SUS304L (JIS) |
| Carbon (C) | ≤ 0.03 | ≤ 0.03 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 |
| Chromium (Cr) | 18.0 – 20.0 | 18.0 – 20.0 |
| Nickel (Ni) | 8.0 – 12.0 | 8.0 – 12.0 |
SS304L and SUS304L ：Mechanical Properties Comparison
| Property | SS304L | SUS304L |
| Tensile Strength (MPa) | ≥ 485 | ≥ 480 |
| Yield Strength (MPa) | ≥ 170 | ≥ 175 |
| Elongation (%) | ≥ 40 | ≥ 40 |
| Hardness (HB) | ≤ 201 | ≤ 201 |
Corrosion resistance of SUS304L stainless steel
SUS304L stainless steel offers excellent resistance in many environments, particularly atmospheric and mildly corrosive ones, due to its 18% chromium and 8% nickel content, providing good resistance to organic acids, weak phosphoric/sulfuric acids, and fresh water, but it's susceptible to pitting/crevice corrosion in warm chloride solutions (like seawater) and stress corrosion cracking above 60°C, making 316L preferred for harsher chloride/marine conditions, while its low carbon prevents carbide precipitation, making it ideal for welding.
Weldability of SUS304L stainless steel
SUS304L stainless steel offers excellent weldability, superior to standard 304 due to its low carbon content, which prevents sensitization (intergranular corrosion/IGC) in the heat-affected zone (HAZ) without requiring post-weld heat treatment in most cases, making it ideal for heavy sections and corrosive environments, generally joined with TIG/MIG using 308L filler.
What are the differences between SUS304L and SS304?
SUS304L is the low-carbon version of SS304 (Type 304), with the key difference being carbon content: 304 has up to 0.08% carbon, while 304L has a maximum of 0.03%, making 304L ideal for welded applications as it prevents carbide precipitation and maintains corrosion resistance without needing post-weld annealing, whereas 304 may require it. SUS304L offers superior intergranular corrosion resistance after welding, making it better for thicker sections (over 5mm) and harsh chemical/marine environments, though 304 has slightly higher tensile strength.
What are the differences between SUS304L and SUS316L?
SUS304L and SUS316L are both low-carbon austenitic stainless steels, but SUS316L contains molybdenum, giving it superior resistance to chlorides (like saltwater) and pitting corrosion compared to SUS304L, making it better for marine, chemical, and pharmaceutical environments, while SUS304L is more common for general kitchen, food processing, and less corrosive applications. The "L" denotes low carbon, which improves weldability by preventing sensitization, though the primary difference in corrosion resistance comes from the molybdenum in 316L.
SS304L / SUS304L Product Supply and Customization Services
Available Product Forms
SS304L and SUS304L stainless steel are typically supplied in the following forms: plates, coils and strips, tubes (seamless/welded), bars, and custom fabricated parts.
Typical Specifications
Thickness: 0.3 mm – 50 mm (customizable)
Width/Length: Cut to size
Surface Finish: 2B, BA, No.1, No.4, HL, Mirror finish
Standards: ASTM, AISI, JIS, EN, DIN
Processing Services: Laser cutting/plasma cutting, bending and forming, welding and fabrication, drilling/punching
Certification and Quality Control: Mill Test Certificate (EN 10204 3.1), ISO certified production, third-party inspection available (SGS, BV, TUV)
