S355JOW is a type of weathering structural steel specified in the European (EN) standard. It is a self-protective steel that resists atmospheric corrosion by forming a dense oxide layer upon rusting. Below is a detailed explanation:
1. Standards and Specifications
European Standard Code: EN 10025-5 (Hot-rolled structural steels - Part 5: Weathering steels)
Similar international grades:
American Standard: ASTM A588 Grade K (similar performance)
Japanese Standard: JIS G3114 SMA570W
National Standard: Q355NH (GB/T 4171-2008)
2. Name Meaning
S355: Indicates a minimum yield strength of 355 MPa (same grade as ordinary structural steel S355, but with enhanced corrosion resistance).
JOW: Suffix code, specific meaning:
J: Impact toughness tested at -20°C (low-temperature performance).
O: Hot Rolled (O stands for "Hot Rolled").
W: Weathering.
3. Core Properties
Corrosion Resistance:
By adding alloying elements such as copper (Cu), chromium (Cr), and phosphorus (P), a stable rust-resistant layer is formed on the surface (no paint required).
Suitable for exposure to humid, industrial atmospheres, or mild salt spray environments (such as bridges and building facades).
Mechanical Properties:
Property Value
Yield Strength (Rp0.2) ≥355 MPa
Tensile Strength (Rm) 470-630 MPa
Elongation (A5) ≥22%
4. Typical Applications
Architecture: Curtain walls, sculptures, roofs (such as the Guggenheim Museum in Bilbao, Spain).
Bridge Engineering: Maintenance-free bridge structures (the rust layer is a protective layer).
Outdoor Facilities: Containers, railway carriages, power pylons.
5. Differences from Ordinary Steel (e.g., S355JR)
Comparison Items: S355JOW S355JR (Ordinary Structural Steel)
Weather Resistance: Exposed use, self-protective rust layer; anti-rust paint required
Alloy Composition: Contains Cu, Cr, and P; no special weathering elements
Cost: Higher (approximately +20%-30%) Lower
6. Processing and Construction Precautions
Welding: Requires compatible weathering steel electrodes (e.g., EN ISO 2560-A: E CrMo).
Cutting: Avoid contamination of carbon steel (to prevent uneven localized rusting).
Initial Rust: Rust-colored rainwater may drip during the first six months; drainage channels or temporary shelter may be required.
