EH40 is a high-strength steel plate used for ship hull structures, with its designation following the steel grading system of the American Bureau of Shipping (ABS) and other major international classification societies (such as DNV, LR, and NK). It is widely used in the construction of ships and offshore engineering structures. The letter "E" stands for "Quality Grade E," indicating that the steel is a fully killed, fine-grain steel with guaranteed impact toughness at extremely low temperatures. Specifically, it must meet a minimum average absorbed energy of 27 J in Charpy V-notch impact testing at -40°C, making it suitable for vessels operating in polar or subarctic regions. "H" denotes "High-strength steel," distinguishing it from ordinary-strength steels (e.g., Grades A or B) and indicating its use in critical hull areas requiring higher load-bearing capacity. The number "40" refers to the specified minimum yield strength of 40 ksi (approximately 275 MPa) at room temperature. Therefore, EH40 is a high-strength structural steel for shipbuilding with a yield strength of no less than 275 MPa and reliable toughness at -40°C. It is one of the highest-grade conventional strength levels within the ABS high-strength series (AH40, DH40, EH40, FH40), specifically designed for vessels operating in polar or high-latitude regions during winter.
The main characteristics of EH40 steel plate include high strength, exceptional low-temperature toughness, and good weldability. Its chemical composition is strictly controlled, with a low carbon content (typically ≤0.18%) to ensure a low carbon equivalent (CEV) and good weldability. It also contains moderate amounts of microalloying elements such as manganese, niobium, and vanadium, which significantly enhance both strength and toughness through solid-solution strengthening, grain refinement, and precipitation hardening. The tensile strength ranges from 78 to 94 ksi (540–650 MPa), with elongation meeting specification requirements, offering excellent fatigue resistance and the ability to withstand dynamic loads. Due to its ability to maintain sufficient toughness at -40°C, EH40 is particularly suitable for icebreakers, polar research vessels, liquefied natural gas (LNG) carriers, and various other ships operating in extreme cold environments such as the Arctic and Antarctic, effectively preventing brittle fracture under severe low-temperature conditions.
EH40 steel plate exhibits excellent weldability and is compatible with various welding processes such as submerged arc welding (SAW) and gas metal arc welding (GMAW). Welded joints are stable and high-quality, but due to its higher alloy content and strength, preheating (with temperature determined by plate thickness and ambient conditions) is typically required to prevent cold cracking.
EH40 steel plate is widely used in primary hull structures of commercial and specialized vessels operating in frigid waters, including large cargo ships, tankers, container ships, bulk carriers, icebreakers, and offshore vessels. It is commonly applied to critical load-bearing components such as decks, side shell plating, keels, frames, bulkheads, and girders. Compared to ordinary-strength steels or AH40 steel, EH40 not only offers higher strength but also superior low-temperature toughness, allowing for reduced hull weight while maintaining structural integrity, thereby improving vessel payload capacity and economic efficiency.
The current standard for EH40 steel plate is the Rules for Materials and Welding published by the American Bureau of Shipping, specifically Part 2: "Steels" and Part 3: "Hull Structures." The latest edition is the 2025 version, which provides detailed technical requirements for chemical composition, mechanical properties, impact toughness (-40°C), manufacturing processes, inspection methods, and classification approval. It is an authoritative and internationally recognized technical standard widely adopted in the global shipbuilding industry. Due to its excellent overall performance, EH40 has become an indispensable key material in modern shipbuilding.
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.
