Rules of Korean Register of Shipping

The Korean Register of Shipping (KR) is South Korea’s sole national classification society and a full member of the International Association of Classification Societies (IACS), holding significant influence in the global maritime and offshore industries. Its "Rules for the Classification of Steel Ships" provide comprehensive technical standards for ship design, construction, and survey, with systematic and stringent requirements for hull structural steel plates to ensure structural safety, durability, and fatigue resistance under various operational conditions.

In terms of steel plate specifications, KR 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 of the structural component, stress levels, and service temperature. Each grade has clearly defined requirements for chemical composition, mechanical properties, and impact toughness. To ensure good weldability and resistance to crack propagation, KR standards strictly control the carbon equivalent (Ceq) and limit harmful impurities such as sulfur (S) and phosphorus (P), with even stricter limits for high-strength steels and those intended for low-temperature service.

Mechanical properties are central to KR’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 vessels intended to operate in cold or polar waters, steel plates used in critical structural areas—such as the bow, side shell plating, and connections of the strength deck—must pass impact tests at -40°C or lower to verify their toughness and prevent brittle fracture in cold environments.

Additionally, KR 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 inspection by KR-authorized surveyors (WITNESS), who supervise the entire process, including steelmaking, rolling, heat treatment, and mechanical 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, the Korean Register ensures high reliability and long-term safety of marine steel plates through a scientific material grading system, rigorous performance verification, and comprehensive quality control, providing robust technical support for modern shipbuilding.

Official Website: https://www.krs.co.kr