Technical Specifications for S355J0WP Weathering Steel Plate

1. Basic Grade Information

2. Grade Designation Meaning

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3. Chemical Composition

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Among these, P, Cu, and Cr are key alloying elements for the weathering resistance of S355J0WP. In particular, the WP grade has a relatively high phosphorus content, which aids in the formation of a protective rust layer.

4. Mechanical Properties

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5. Impact Properties

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6. Weathering Performance

The core advantage of S355J0WP lies in its resistance to atmospheric corrosion. When exposed to air and moisture, a stable oxide protective layer—commonly known as a patina—gradually forms on the steel’s surface. This patina effectively slows the rate at which oxygen and moisture penetrate the steel matrix.

The typical evolution of the patina on weathering steel surfaces is as follows:

New steel surface → Yellow/orange → Reddish-brown → Dark brown protective rust layer

The rate at which the protective rust layer forms is influenced by factors such as the frequency of dry-wet cycles, air pollutants, salt content, rainfall conditions, and structural drainage; therefore, it cannot be simply assumed that the steel requires no maintenance under all environmental conditions.

7. Delivery Condition

S355J0WP is a hot-rolled weathering steel specified in EN 10025-5 and is typically supplied in the delivery condition required by the standard.

EN 10025-5:2019 also specifies that steels covered by this standard are not, in principle, intended for routine use as heat-treated products; if the contract requires delivery in the +N condition, the corresponding technical requirements for normalizing or normalize-rolled steel must be met.

Common ordering requirements include:

Delivery condition: Hot-rolled (AR) or +N (normalized/normalize-rolled, as specified in the contract)

Surface quality: Compliant with relevant standards such as EN 10163

Material certificate: EN 10204 Type 3.1 certificate

Third-party inspection: May be added as specified in the contract

8. Welding and Machining

S355J0WP possesses good machinability and can undergo conventional machining operations such as cutting, drilling, bending, and welding. Welding procedures must comprehensively consider factors such as plate thickness, carbon equivalent, preheating temperature, heat input, and welding consumable compatibility; welding parameters for standard S355J2 must not be directly applied based solely on the “S355” grade designation.

Actual welding operations must be performed in strict accordance with the relevant WPS (Welding Procedure Specification) and PQR (Welding Procedure Qualification Record), in conjunction with the material manufacturer’s process recommendations.

9. Main Applications

S355J0WP is suitable for engineering applications involving long-term exposure to the atmosphere that require both structural strength and weather resistance. Typical applications include:

1) Bridges and bridge components

2) Railway rolling stock and freight car bodies

3) Building facades

4) Outdoor steel structures

5) Industrial plants

6) Landscape architecture

7) Port facilities and outdoor engineering structures

Precautions for Use:

Weathering steel is not suitable for all corrosive environments. In areas subject to prolonged submersion, persistent high humidity, high-chloride marine environments, or poor drainage, a stable and dense protective rust layer may not form. Under such conditions, a coating or other additional corrosion protection measures are typically required.