GB/T 4171 Q355GNH High Weathering Steel Plate

GB/T 4171 Q355GNH high weathering steel (corten steel) is a high-performance steel that combines high strength, high toughness, excellent atmospheric corrosion resistance, good weldability, and good workability. Commonly known as "weathering steel," it is based on ordinary steel with the addition of small amounts of alloying elements such as copper, phosphorus, chromium, and nickel. This enables it to form a dense and stable rust protective layer in the atmosphere, significantly enhancing its resistance to atmospheric corrosion.

By forming a protective rust layer through its alloy composition, it achieves long-term corrosion resistance and a unique visual effect. This makes it an ideal material solution for outdoor steel structure projects that pursue long service life, low maintenance, and natural aesthetic appeal. It is an important material in modern architecture, bridges, and engineering structures, combining both functionality and aesthetics.

Scope of application: structural components such as vehicles, bridges, containers, buildings, and towers that are exposed to the atmospheric environment for extended periods. It can be used to create structures connected by bolts, rivets, and welding. It not only extends service life and reduces maintenance costs but also enables reductions in thickness and material consumption, making it an economical and environmentally friendly green building material.

When selecting for specific projects, comprehensive consideration should be given to environmental conditions, design life, and aesthetic requirements. The appropriate quality grade (A/B/C/D/E) should be chosen based on the operating environmental temperature and the importance of the application to ensure structural safety and service life.

* Compared with Q355NH, it has better atmospheric corrosion resistance but slightly inferior weldability.

Key Features and Advantages

1. Superior Weather Resistance

Weathering resistance is 2-8 times higher than that of ordinary carbon steel

Coating performance is 1.5-10 times better than that of ordinary carbon steel

Requires no painting or minimal maintenance, significantly extending service life

2. Comprehensive Mechanical Properties

High strength: Meets the load-bearing requirements of engineering structures

Good plasticity and toughness: Adapts to complex stress environments

Excellent weldability: Low susceptibility to hot and cold cracking, ensuring reliable welding quality

3. Economic Advantages

No painting or simplified painting: Lowers initial and long-term maintenance costs.

Cost-effective: Components lifespan extended, with lower total lifecycle cost.

Environmentally friendly and energy-saving: Reduces pollution from anti-corrosion treatments, aligning with sustainable development.

Carbon Equivalent (CEV) of Q355GNH Weathering Steel Plate (Corten Steel Plate) : ≤ 0.43%.

* Calculate using the standard formula recommended by the International Institute of Welding (IIW): CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15.

Note: "a" is the thickness of the steel material.

Impact Energy

* The main difference lies in the varying impact test temperature requirements, ranging from Grade A (no requirement) to Grade E (-40°C), with progressively increasing demands for low-temperature toughness.

Thanks to its features of "no painting or minimal maintenance, high strength, and long lifespan," Q355GNH High Weathering Steel (Corten Steel) Plate is widely used in outdoor steel structures that require durability and aesthetic appeal:

1. Bridge Engineering:

Especially for landscape bridges, pedestrian bridges, highway guardrails, etc., taking advantage of its naturally formed dense rust-red appearance that blends seamlessly with the natural environment.

2. Building Exteriors and Structures:

High-rise building frameworks, roof structures, curtain wall support structures, decorative panels, large-scale venues, bus shelters, etc., aiming for industrial aesthetic effects.

3. Vehicle Manufacturing:

Railway freight carriages, containers, etc., to reduce structural weight and minimize maintenance.

4. Tower Structures:

Power transmission towers, communication towers, lighthouses, outdoor billboards, etc.

5. Marine Engineering:

Port facilities, oil drilling platforms, oil derricks, etc.

6. Energy and Chemical Industries:

Storage tanks, pipeline supports, etc., in environments containing H₂S.

7. Landscape Architecture and Artistic Installations:

Outdoor sculptures, garden facilities, etc.

8. Others:

Steel structures that require long-term exposure to the atmosphere, are difficult to maintain, or aim for a specific appearance.

Precautions for Processing and Usage

1. Environmental Adaptability:

Its excellent weather resistance performs outstandingly in dry, clean atmospheric conditions and rural environments. In heavily polluted settings with high humidity, high chloride ion levels (e.g., coastal areas), or high sulfide concentrations (e.g., heavy industrial zones), its corrosion-resistant advantages may diminish. Careful evaluation or additional protective measures are required under such conditions.

2. Initial Rust Flow:

During the initial stage of rust layer stabilization (typically lasting 1-3 years), rainwater runoff may cause yellowish-brown rust stains to flow and contaminate adjacent walls or ground surfaces. Drainage or temporary diversion measures should be considered in the design phase to address this issue.

3. Welding and Processing:

Welding techniques are similar to those for ordinary low-alloy steels, but heat input must be controlled to avoid the loss of alloying elements around the weld area, which could reduce corrosion resistance.

When welding, specialized weathering steel electrodes should be used to ensure the weld seam exhibits corrosion resistance comparable to that of the base metal.

Remove scale promptly after cutting, and control the deformation rate during cold bending processes.

4. Surface Conditions:

Options such as "hot-rolled" or "pickled" surface finishes are available. For exposed applications, a pickled surface offers a more uniform and aesthetically pleasing appearance, aiding in the formation of a consistent and stable rust layer.

5. Avoid Direct Contact with Ordinary Steel:

Prevent electrochemical corrosion by avoiding direct contact between weathering steel and ordinary steel.

Differences from Q355NH

Q355NH: Ordinary weather-resistant steel, suitable for general outdoor environments. "NH" stands for "weather-resistant."

Q355GNH: High weather-resistant steel. "GNH" stands for "high weather-resistant." It has higher alloy element content, stronger corrosion resistance, and a higher price. It is suitable for harsh corrosive environments (e.g., marine, industrial polluted areas).

Quality Grade Selection Guide

Comparison with Similar Steel Grades

Note: The same series of "GNH" grades (e.g., Q355GNH) are high weather resistance grades, offering better weather resistance but slightly poor weldability.