Lloyd’s Register (LR) is one of the world's oldest and most influential classification societies, and a founding member of the International Association of Classification Societies (IACS). Its "Rules and Regulations for the Classification of Ships" provide authoritative technical standards for global ship design and construction, with particularly systematic and stringent requirements for hull structural steel plates, ensuring structural safety and seaworthiness throughout a vessel’s lifecycle.

In terms of steel plate specifications, LR classifies hull steel into ordinary strength grades (A, B, D, E) and higher strength grades (such as AH32, AH36, AH40, DH32, DH36, DH40, EH32, EH36, EH40), based on the importance, stress levels, and service environment of the structural components. Each grade has clearly defined requirements for chemical composition, mechanical properties, and toughness. To ensure weldability and resistance to cracking, LR standards strictly control carbon equivalent (Ceq) and limit impurities such as sulfur (S) and phosphorus (P), with even stricter limits for high-strength and low-temperature service steels.

Mechanical properties are central to LR’s plate requirements. The rules specify yield strength, tensile strength, elongation, and Charpy V-notch impact energy (KV2) at ambient and low temperatures (e.g., 0°C, -20°C, -40°C). For ships operating in cold regions, plates used in critical structural areas—such as the bow, side shell, and connections to superstructures—must pass impact tests at -40°C to prevent brittle fracture in low-temperature environments.

Furthermore, LR sets detailed requirements for manufacturing processes, surface quality, dimensional tolerances, non-destructive testing (e.g., ultrasonic testing), and traceability. Steel production must be subject to LR surveyor inspection (WITNESS), with supervision throughout the entire process, including steelmaking, rolling, heat treatment, and testing. All plates used in primary load-bearing structures must be accompanied by complete material certification and maintain full traceability from slab to final product.

In summary, Lloyd’s Register ensures high reliability and safety of marine steel plates in demanding maritime environments through scientific material grading, rigorous performance verification, and comprehensive quality control, setting a benchmark for technical excellence in the global shipbuilding industry.

Official Website:?https://www.lr.org