The naming of Q295GNHA carries clear performance indicators:
"Q" stands for yield strength (the first letter of the Chinese character "Qu", meaning yield);
"295" indicates that the minimum yield strength is 295 MPa;
"GNH" is the abbreviation of "Gāo Nài Hòu" (High Weathering Resistance in Chinese), highlighting its excellent atmospheric corrosion resistance;
"A" represents the quality grade, corresponding to basic impact toughness requirements, suitable for non-extreme low-temperature environments.
Core Characteristics: Balance Between Strength and Corrosion Resistance
Superior Weathering Resistance: Through the synergistic effect of alloying elements such as Cu, Cr, and Ni, a dense α-FeOOH rust layer is formed on the surface. The corrosion rate is only 1/2 to 1/8 that of ordinary carbon steel, achieving the effect of "rust preventing rust".
Excellent Mechanical Properties: The tensile strength reaches 430-580 MPa, the elongation after fracture is ≥22%, and the cold bending performance meets the standards, combining load-bearing capacity with plastic toughness.
Reliable Weldability: The carbon equivalent is strictly controlled. By matching suitable welding materials and processes, crack-free joints can be obtained, meeting the requirements of structural connection.
Main Applications: Preferred Material for Outdoor Engineering
Relying on its weathering resistance advantages, it is widely used in open-air structural fields:
Bridge Engineering: Load-bearing components such as main girders and piers, which have been applied in projects like the Hong Kong-Zhuhai-Macau Bridge;
Construction Field: Decorative and structural components such as exterior wall panels and roofs;
Transportation: Railway carriages and container frames;
Tower Mast Structures: Long-term exposed facilities such as power transmission towers and wind turbine towers.
Executive Standard: GB/T 4171-2008
Currently, it adopts the standard "Weathering Resistant Structural Steels" (GB/T 4171-2008). This standard clearly specifies its chemical composition, mechanical properties, and inspection methods, serving as the core basis for production and material selection.
Ultrasonic Testing (UT)
A key non-destructive testing technique that uses high-frequency sound waves to detect internal flaws in steel plates. The probe emits sound waves, which reflect when encountering defects such as cracks or inclusions. The receiver captures the echoes, enabling precise determination of defect location and size. With high sensitivity, strong penetration, and fast inspection speed, UT effectively ensures internal quality, widely used in the production of heavy plates, pressure vessel plates, and other high-end products to guarantee safety and reliability.
Magnetic Particle Testing (MT)
A common surface inspection method that magnetizes the workpiece, causing leakage magnetic fields at surface or near-surface defects like cracks or inclusions, which attract magnetic particles to form visible indications. Simple to operate and highly sensitive, MT is suitable for rapid inspection of surface and near-surface flaws in ferromagnetic materials, widely used for online or offline inspection of plate edges, ends, and welds, ensuring product quality and safety.
Penetrant Testing (PT)
A non-destructive method for detecting surface-breaking flaws. A penetrant liquid is applied to the cleaned steel surface, allowing it to seep into defects such as cracks or pores. After removing excess penetrant, a developer is applied, causing the trapped penetrant to bleed out and form visible indications. Simple and cost-effective, PT is suitable for inspecting surface defects in various non-porous materials, commonly used for welds, castings, and complex components, effectively ensuring surface quality of steel plates.
