GB/T 4171 Q355NH is a high-strength low-alloy weathering structural steel that integrates high strength, excellent weather resistance, good weldability, and favorable plasticity into a modern structural steel material. It is particularly suitable for various engineering structures that are exposed to atmospheric environments for extended periods. Its "maintenance-free or minimal painting" characteristic not only reduces construction costs but also minimizes the need for subsequent maintenance efforts, making it an ideal choice for modern bridges, buildings, towers, vehicle manufacturing, and other fields. It serves as an important material that balances structural strength, durability, and lifecycle costs.

The selection should be made by comprehensively considering the application environment, temperature requirements, and cost-effectiveness to reasonably choose the appropriate quality grade (A/B/C/D/E).

* Compared with Q355GNH, it has better weldability but slightly inferior atmospheric corrosion resistance.

Key Features and Advantages

1. Outstanding Weather Resistance

The atmospheric corrosion resistance is 2-8 times that of ordinary carbon steel: By adding elements such as Cu, P, Cr, and Ni, a dense and stable "protective rust layer" forms on the surface, preventing further corrosion. This eliminates the need for painting or requires minimal maintenance, extends service life, and reduces the total lifecycle cost.

2. Comprehensive Mechanical Properties

High Strength and Lightweight: Yield strength ≥355 MPa, tensile strength 490-630 MPa, reducing structural weight while maintaining high load-bearing capacity.

Excellent Weldability: Superior welding performance compared to high-weathering steel (Q355GNH), making it suitable for various welded structures.

Good Processing Performance: Excellent performance in cold bending, stamping, shearing, and other processes, suitable for manufacturing complex structural components.

3. Economic Efficiency

Thinner Plates Reduce Material Consumption: Thinner plates can be used for the same lifespan, reducing structural weight.

Labor and Energy Savings: Reduced frequency of anti-corrosion painting and maintenance, lowering labor and energy costs.

Carbon Equivalent (CEV) of Q355NH Weathering Steel Plate (Corten Steel Plate) : ≤ 0.42%.

* 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.

Due to its excellent weather resistance and sufficient strength, Q355NH Weathering Steel (Corten Steel) Plate is widely used in outdoor steel structures requiring corrosion resistance, especially in situations where maintenance is difficult or a natural aesthetic appeal is pursued:

1. Bridge Engineering:

Such as cross-sea bridges, urban viaducts, railway bridges, highway bridges, pedestrian landscape bridges, etc.

2. Architectural Structures:

Exterior walls, roofs, curtain walls, towers, station canopies of high-rise buildings;

Roofs and exposed frameworks of large public buildings such as railway stations, stadiums, exhibition centers, and airport terminals.

3. Transportation Equipment & Vehicle Manufacturing:

Railway vehicles, containers, freight car bodies;

Highway guardrails, subway and light rail vehicle structural components;

Construction machinery and mining equipment.

4. Energy Facilities:

Power transmission towers, wind turbine towers, communication signal towers, lighthouses;

Solar support structures, coastal power plant equipment.

5. Marine Engineering:

Offshore platforms, offshore structures, port facilities.

6. Art Installations & Landscaping:

Outdoor sculptures, cultural landmarks, landscape bridges, railings, municipal facilities.

7. Other Outdoor Structures:

Industrial plants, storage facilities.

Precautions for Processing and Usage

1. Surface Appearance:

During the initial period of use (approximately 1-3 years), the rust layer is unstable, and phenomena such as rust runoff and uneven color may occur, which is part of the normal process. Eventually, a uniform, dense, and stable reddish-brown rust layer will form.

2. Welding:

It exhibits good welding performance. Prior to welding, the oxide layer on the surface of the welding area must be removed, and preheating may be required if necessary. Matching welding materials specifically designed for weathering steel (typically containing alloy elements such as Cu and Cr) must be used to ensure that the weld metal possesses corrosion resistance similar to that of the base metal.

3. Cutting and Processing:

The processing techniques are similar to those for ordinary low-alloy high-strength steel. However, it should be noted that due to its higher strength, greater processing forces may be required.

4. Mixing with Ordinary Steel:

Direct contact with ordinary carbon steel should be avoided to prevent electrochemical corrosion caused by potential differences. If connection is necessary, adequate insulation treatment must be applied.

Differences from Q355GNH

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.