Q345GNHJ Weather Resistant Steel Coil per GB/T 18982
Q345GNHJ Weather Resistant Steel Coil per GB/T 18982-2003 for Containers
Q345GNHJ is a high-strength weather resistant steel specifically developed for container manufacturing, offering excellent atmospheric corrosion resistance and mechanical properties in the as-rolled condition.
Cold bending, roll forming, shearing, welding, punching, cutting, stamping
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Q345GNHJ Weather Resistant Steel Coil per GB/T 18982 Introduction
Q345GNHJ is a structural weather resistant steel grade defined in Chinese standard GB/T 18982-2003 (Corrosion-resistant steel plates and strips for containers). It is a high atmospheric corrosion resistant (or 'weathering') steel, typically supplied in the as-rolled or skin-passed condition. The designation 'Q345' indicates a minimum yield strength of 345 MPa, 'GNH' stands for high weathering resistance, and 'J' denotes its principal application in containers. The steel forms a stable, protective rust patina under atmospheric exposure, eliminating the need for painting and reducing life-cycle costs. It contains deliberate additions of copper, chromium and nickel to enhance corrosion resistance. Typical thicknesses for container applications range from 1.6 mm to 6.0 mm, though the standard covers a wider range. This material is designed for excellent cold formability, weldability, and toughness, making it ideal for the demanding environments of intermodal freight containers and similar exposed structures.
Q345GNHJ Weather Resistant Steel Coil per GB/T 18982 Chemical Composition
The chemical composition of Q345GNHJ steel is in accordance with GB/T 18982-2003 Table 1. It is a Cu-Cr-Ni alloyed weathering steel. Phosphorus is intentionally added within the specified range to improve atmospheric corrosion resistance. The carbon equivalent is controlled to ensure good weldability.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤0.12 | Heat analysis |
| Silicon (Si) | 0.25 – 0.75 | Heat analysis |
| Manganese (Mn) | 0.20 – 0.50 | Heat analysis |
| Phosphorus (P) | 0.06 – 0.15 | Required for weathering resistance |
| Sulfur (S) | ≤0.030 | Heat analysis |
| Copper (Cu) | 0.25 – 0.50 | Corrosion resistance element |
| Chromium (Cr) | 0.30 – 1.25 | Corrosion resistance element |
| Nickel (Ni) | ≤0.65 | Corrosion resistance & toughness |
Q345GNHJ Weather Resistant Steel Coil per GB/T 18982 Thermal and Electrical Physical Properties
The following physical property values are typical for low-alloy weathering steels at room temperature unless otherwise noted. They are provided for design and engineering reference and are not mandatory requirements of the delivery standard.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20 °C |
| Modulus of elasticity (E) | 206 | GPa | Room temperature, dynamic |
| Shear modulus (G) | 79.3 | GPa | Calculated from E and Poisson's ratio |
| Poisson's ratio (ν) | 0.30 | - | Room temperature |
| Thermal expansion coefficient (α) | 11.5 × 10-6 | K-1 | 20 ℃ to 100 ℃ |
| Thermal conductivity (λ) | 45 | W/(m·K) | At 20 ℃ |
| Specific heat capacity (cp) | 460 | J/(kg·K) | At 20 ℃ |
| Electrical resistivity (ρe) | 0.15 × 10-6 | Ω·m | At 20 ℃ |
Q345GNHJ Weather Resistant Steel Coil per GB/T 18982 Mechanical Properties
Mechanical properties are determined on transverse specimens. The yield strength is specified as lower yield (ReL). The tensile test uses a gauge length of 50 mm (L0=50 mm) for thicknesses ≥3 mm, and 80 mm (L0=80 mm) for thicknesses <3 mm. The bend test is a 180° cold bend with a mandrel diameter equal to 2 times the specimen thickness.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReL) | ≥345 | MPa | All thicknesses covered by the standard |
| Tensile strength (Rm) | ≥480 | MPa | All thicknesses covered by the standard |
| Elongation after fracture (A80) | ≥19 | % | Thickness < 3 mm, L0 = 80 mm |
| Elongation after fracture (A) | ≥22 | % | 3 mm ≤ thickness ≤ 6 mm, L0 = 50 mm |
| Elongation after fracture (A) | ≥24 | % | Thickness > 6 mm, L0 = 50 mm |
| Bend test (180°) | d = 2a | - | Mandrel diameter equals 2 times the specimen thickness (a), no cracking |
Q345GNHJ Weather Resistant Steel Coil per GB/T 18982 Completely Equivalent Material Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3125 | SPA-H | Commonly used substitute in containers; minimum yield strength 355 MPa, similar weathering concept but chemical composition differs slightly |
| EU | EN 10025-5 | S355J2W+N | Structural weathering steel with comparable yield class; requires careful check of Cu, Cr, Ni contents for full compatibility |
| International | ISO 5952 | S355J0WP | Continuously hot-rolled steel sheet of structural quality with improved atmospheric corrosion resistance; similar strength level but composition is different |
Q345GNHJ Weather Resistant Steel Coil per GB/T 18982 Application Introduction
Q345GNHJ is purpose-designed for the rigorous operating conditions of freight containers and similar exposed transport structures. Its high yield strength enables thinner, lighter sections without sacrificing load capacity. The self-protecting rust layer eliminates the need for painting in many environments, reducing maintenance. Typical applications leverage its excellent cold formability for corrugated panels and its good weldability for assembly.
Product Applications: Dry cargo containers (20 ft, 40 ft, high-cube), Refrigerated containers (structural parts), Special purpose containers (tank, bulk), Offshore / onshore containerised units, Corrugated wall and roof panels for industrial buildings
Processed into products: Container corrugated panels (side and roof sheets), Corner posts, corner fittings, Roof bows and top side rails, Bottom side rails and cross members, Door header, sill, and stile reinforcements, Forklift pocket and tunnel components
Application industries: Container manufacturing (ISO containers, swap bodies), Transportation and logistics, Rolling stock and railway carriages, Architectural cladding and exposed steel structures, Agricultural equipment and silo construction
Q345GNHJ Weather Resistant Steel Coil per GB/T 18982 Similar / Alternative Weathering Steel Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 4171 | Q355GNH | High-strength atmospheric corrosion-resisting structural steel; slightly higher strength class, used in general welded structures |
| USA | ASTM A588/A588M | Grade B | High-strength low-alloy weathering steel for structural applications; similar atmospheric corrosion resistance |
| USA | ASTM A242/A242M | Type 1 | High-strength low-alloy structural steel with enhanced atmospheric corrosion resistance; slightly lower strength |
| EU | EN 10025-5 | S355K2W+N | Improved weathering steel with guaranteed impact properties at low temperature; composition differs from Q345GNHJ |
Notes:
Welding: Q345GNHJ has good weldability with standard processes (MAG, resistance spot welding). Low hydrogen practices and matching weathering filler metals (e.g., AWS ER80S-G) are recommended. Surface: The steel is usually supplied with a mill finish; pickled and oiled may be specified to facilitate further processing. The protective patina develops after alternate wetting and drying cycles; accelerated stabilisation treatments are available. Forming: Minimum bend radii of 1.5t to 2.0t are typical for cold forming of this grade depending on edge condition and thickness. Design: Joints and details should be designed to avoid moisture traps and ensure proper drainage in the exposed condition.
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