Difference between LR DH50 and LR DH62 steel plate

LR DH50 and LR DH62 are high-strength shipbuilding steel plates certified by Lloyd's Register (LR). The "D" designates their delivery condition (Normalized or Normalized Rolled), while "H" indicates High strength. These normalized plates are primarily used in key structural members of ships and offshore platforms, such as deck plates and hull structures, where a combination of good strength, reliable low-temperature toughness, and excellent weldability is required for safe operation in various marine environments.

Key Differences:

The core difference is their strength level. LR DH50 has a minimum yield strength of 390 MPa (the '50' denotes a tensile strength of 500 MPa or 50 kgf/mm²), while LR DH62 offers a higher yield strength of 460 MPa (with a minimum tensile strength of 620 MPa). DH62 is the stronger grade, allowing for weight reduction in structural design.

To achieve this higher strength, DH62 requires a more carefully balanced chemical composition, typically involving micro-alloying elements like Niobium and Vanadium. While both grades are supplied in a normalized condition which ensures a uniform microstructure and generally good weldability, the higher alloy content of DH62 results in a higher carbon equivalent. Consequently, welding DH62 may require slightly more stringent procedures-such as stricter control of preheating temperatures and heat input-compared to DH50 to effectively manage the risk of cold cracking. Overall, the selection between DH50 and DH62 involves balancing the required structural strength with fabrication considerations and material cost.

Chemical Composition

Mechanical Property