JIS G3125-2004 SPA-H Weather Resistant Steel Coil
JIS G3125 SPA-H Weathering Steel Coil | High Strength Structural Steel for Outdoor Use
Explore the properties, chemical composition, mechanical performance, thermal characteristics, equivalent grades, and applications of JIS G3125 SPA-H weather resistant steel coil, a high-strength structural steel designed for welded structures in outdoor environments.
Cutting, bending, forming, welding, drilling
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JIS G3125-2004 SPA-H Weather Resistant Steel Coil Introduction
JIS G3125 SPA-H is a high-strength, atmospheric corrosion-resistant hot-rolled steel intended for welded structural applications. The steel gains its weathering properties through the controlled addition of alloying elements such as copper, chromium, and nickel, which promote the formation of a dense, adherent protective patina when exposed to the atmosphere. This patina reduces the corrosion rate significantly compared to plain carbon steel, often eliminating the need for painting. SPA-H offers a minimum yield strength of 355 MPa and a tensile strength of at least 490 MPa, with good formability and weldability. It is commonly supplied in coil or sheet form and is widely used in bridges, building structures, containers, railway vehicles, and other outdoor steelworks where long service life and low maintenance are required.
JIS G3125-2004 SPA-H Weather Resistant Steel Coil Chemical Composition
The chemical composition of SPA-H is designed to provide enhanced resistance to atmospheric corrosion. Key alloying elements include copper, chromium, and phosphorus, which work synergistically to form a stable protective oxide layer. All values are in mass percent as specified in JIS G3125:2004.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.12 | Upper limit |
| Silicon (Si) | 0.25–0.75 | Alloying range |
| Manganese (Mn) | 0.20–0.50 | Alloying range |
| Phosphorus (P) | 0.070–0.150 | Enhances corrosion resistance |
| Sulfur (S) | ≤0.040 | Upper limit |
| Copper (Cu) | 0.25–0.60 | Critical for weathering performance |
| Chromium (Cr) | 0.30–1.25 | Contributes to patina formation |
| Nickel (Ni) | ≤0.65 | Optional element; improves toughness |
JIS G3125-2004 SPA-H Weather Resistant Steel Coil Thermal and Electrical Physical Properties
Typical physical properties for SPA-H weathering steel are based on general data for high-strength low-alloy steels. These values are not specified in JIS G3125 but are commonly used for design calculations. Values may vary slightly with actual composition and temperature.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20 °C |
| Elastic Modulus (E) | 200–210 | GPa | At 20 °C |
| Shear Modulus (G) | 80–81 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.29–0.30 | — | At 20 °C |
| Thermal Expansion Coefficient (α) | 11.7 × 10⁻⁶ | K⁻¹ | From 20 to 100 °C |
| Thermal Conductivity (λ) | 42–48 | W/(m·K) | At 20 °C |
| Specific Heat Capacity (c) | 460–470 | J/(kg·K) | At 20 °C |
| Electrical Resistivity (ρ_e) | 0.15–0.25 | µΩ·m | At 20 °C |
JIS G3125-2004 SPA-H Weather Resistant Steel Coil Mechanical Properties
The mechanical properties are determined from test pieces taken in the transverse direction. For hot-rolled coil, the yield strength and tensile strength are guaranteed for thickness up to 16 mm. Elongation values depend on thickness. Bend test is performed with a mandrel diameter of 1.5 times the specimen thickness for tensile strength ≥490 N/mm² class.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH / Rp0.2) | ≥355 | N/mm² (MPa) | Thickness ≤ 16 mm |
| Tensile Strength (Rm) | ≥490 | N/mm² (MPa) | Thickness ≤ 16 mm |
| Elongation (A) | ≥22 | % | Thickness ≤ 5 mm, gauge length 50 mm |
| Elongation (A) | ≥17 | % | Thickness > 5 and ≤ 16 mm, gauge length 50 mm |
| Elongation (A) | — | % | Thickness > 16 mm (not specified) |
| Bend Test (180°) | d = 1.5a | — | Thickness ≤ 16 mm; no cracks on outside of bent portion |
JIS G3125-2004 SPA-H Weather Resistant Steel Coil Completely Equivalent Material Standards and Recommended Substitutes
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3125 | SPA-H | Original standard grade |
| China | GB/T 4171 | Q355GNH | High weather resistance structural steel, closest match |
| Europe | EN 10025-5 | S355J2W | Symbolic designation includes improved atmospheric corrosion resistance |
| USA | ASTM A588 / A588M | Grade A or B | High-strength low-alloy structural steel with 50 ksi yield for weathering applications |
| International | ISO 4952 | Fe355W-1 | Corresponds to weathering structural steel with similar strength level |
JIS G3125-2004 SPA-H Weather Resistant Steel Coil Application Introduction
JIS G3125 SPA-H is engineered for outdoor structural applications where long-term atmospheric exposure occurs. It is frequently used without protective coatings, relying on its self-protecting rust layer after initial oxidation. Typical industries and products include:
Product Applications: Steel bridge decks and box girders, Unpainted weathering steel bridge structures, Cargo containers and ISO containers, Railway passenger car underframes and components, High-voltage transmission line towers, Weathering steel cladding and architectural panels, Sound barriers and guardrails along highways
Processed into products: Welded structural beams and columns exposed outdoors, Box-shaped bridge piers and abutments, Container corner castings and side panels, Railcar center sills and draft gear housings, Tower gusset plates and cross-arms, Facade support brackets and fasteners (when withstood by matching filler metals), Cut and bent plates for artistic sculptures
Application industries: Bridge construction and highway infrastructure, Building and civil engineering (exposed steel frames, facades), Container manufacturing (shipping containers, intermodal boxes), Railway vehicle and rolling stock fabrication, Transmission and telecommunication towers, Offshore and port structures (non-immersed parts), Architectural sculpture and outdoor decoration
JIS G3125-2004 SPA-H Weather Resistant Steel Coil Similar / Alternative Material Recommendations
| Country / Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3114 | SMA490AW/BW/CW | Welded structural steel with atmospheric corrosion resistance; higher tensile strength but similar applications |
| China | GB/T 4171 | Q355NH | Weathering structural steel; tighter phosphorus control may limit direct substitution |
| Europe | EN 10025-5 | S355J0W | Similar strength, but lower notch toughness at 0°C compared to J2 variant |
| USA | ASTM A242 | Type 1 | Older specification with comparable corrosion resistance, typically for thickness ≤ 4 in |
| India | IS 11587 | Fe 490W | Structural steel for atmospheric corrosion resistance, close to SPA-H strength level |
Notes:
Welding considerations: Use matching low-alloy weathering consumables (e.g., AWS A5.29 E81T1-W) to ensure similar corrosion resistance in the weld zone. Preheating is generally not required for thicknesses below 30 mm, but refer to the welding procedure specification.
Formability: SPA-H exhibits good cold forming properties, but the higher phosphorus content may require slightly larger bend radii compared to plain carbon steels.
Patina development: The stable protective rust layer forms after several cycles of wetting and drying. In very humid or continuously wet environments, painting may be advisable to avoid excessive initial corrosion.
Availability: Commonly supplied in hot-rolled coil from 1.6 mm to 16 mm thickness, with standard widths up to 2000 mm.
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