P355GH steel plate is a high-strength, non-alloy, fine-grain structural steel produced by hot rolling, specifically designed for high-temperature pressure equipment. It is widely used in medium- and high-pressure boilers, pressure vessels, and industrial piping systems. Its technical requirements are primarily governed by the European standard EN 10028-2:2022 "Flat products made of steels for pressure purposes – Part 2: Non-alloy and alloy steels with specified elevated temperature properties". This standard is the core international specification widely adopted for pressure equipment steel plates, clearly defining the chemical composition, mechanical properties, elevated temperature performance, impact toughness, dimensional tolerances, test methods, and quality assurance requirements for P355GH. As a key grade within the EN 10028-2 standard, P355GH is extensively used in Europe and in countries adopting the European Pressure Equipment Directive (PED), suitable for medium- and high-pressure equipment operating at temperatures up to 400°C. It is one of the most widely used high-temperature pressure steels in industrial applications.
The designation "P355GH" consists of four parts: "P" stands for "Pressure equipment", indicating the steel is intended for pressure vessels; "355" denotes the specified minimum yield strength at room temperature of 355 MPa, placing it in the medium-high strength category. This is significantly higher than grades like P235GH, P265GH, and P295GH, making it suitable for applications with higher load requirements; "G" means "Guaranteed impact test" (the supplier must perform impact testing); and "H" signifies "specified elevated temperature properties", meaning the steel not only meets room-temperature mechanical requirements but also possesses good high-temperature strength, microstructural stability, and creep resistance, ensuring safe long-term service at elevated temperatures. P355GH is a fine-grain non-alloy steel, with carbon content strictly controlled (typically between 0.16%–0.20%) and elements such as aluminum (Al), niobium (Nb), or vanadium (V) added for deoxidation and grain refinement. This results in a uniform microstructure, ensuring good weldability, toughness, and high-temperature stability.
The primary applications of P355GH steel plate are in the energy, chemical, power generation, and heavy industrial sectors, suitable for manufacturing medium- and high-pressure equipment with high demands for strength and reliability, including:
Boiler Manufacturing: Used for shells, headers, tube sheets, end caps, and other critical pressure-bearing components in large power station and industrial boilers.
Pressure Vessels: Used in oil and chemical industries for reactors, separators, heat exchanger shells, and high-pressure storage tanks.
Piping Systems: Used as tube billets or connecting parts for high-temperature steam or thermal fluid pipelines.
Heat Exchange Equipment: Used for manufacturing high-pressure, large-diameter heat exchanger shells and other structures.
Key characteristics include: high room-temperature and elevated-temperature strength (maintaining excellent mechanical properties at 400°C), good weldability (requiring preheating of 150–200°C, with post-weld heat treatment recommended for stress relief), excellent cold and hot formability, and high impact toughness (standard requires Charpy V-notch impact testing at 0°C or -20°C). As a high-performance, high-load-bearing pressure material, P355GH holds an irreplaceable position in modern industrial equipment and is a mainstream choice for the fabrication of medium- and high-pressure pressure vessels.
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.
