DQ56 Ship Plate: Low-Temperature Resistant Alloy for Cold Marine Operations​

DQ56 is a high-strength, low-alloy ship plate grade meeting global marine standards (e.g., EN 10225, GB/T 712), distinguished by its exceptional low-temperature toughness and enhanced structural reliability. A defining characteristic of DQ56 is its ability to maintain ductility and impact resistance at temperatures as low as -40°C, a trait achieved through its refined microstructure and precise alloying (including 0.16% max carbon, 1.60% max manganese, and niobium for grain refinement). It retains the same high strength as AQ56—minimum yield strength of 355 MPa, tensile strength of 490-630 MPa—while adding cold-weather performance, making it ideal for ships operating in sub-polar regions. It also undergoes rigorous quality testing, including Charpy V-notch impact tests at -40°C, to ensure it meets strict toughness criteria.​
The main function of DQ56 is to provide safe, reliable structural support in ships and offshore structures operating in cold marine environments, where low temperatures could cause brittle fracture in standard ship plates. Its advantages are centered on low-temperature resilience: unlike AQ56, DQ56 resists cracking even in freezing conditions, reducing the risk of catastrophic structural failure. It also offers excellent weld integrity—when welded with appropriate techniques, the heat-affected zone retains its low-temperature toughness, eliminating weak points. Additionally, DQ56 has good formability, allowing it to be shaped into complex components like curved hull sections without compromising performance.​
DQ56 is extensively used in the construction of ice-class cargo ships, offshore supply vessels, and research vessels operating in sub-polar regions (e.g., the North Sea or Southern Ocean). Key applications include bow sections (exposed to ice impact), hull plating in cold-water zones, and load-bearing bulkheads that must withstand both heavy loads and low temperatures. It is also a preferred material for offshore oil platforms in cold coastal areas, as it resists both freezing temperatures and seawater corrosion. Furthermore, DQ56 is used in naval vessels designed for cold-water missions, where structural integrity in extreme weather is a strategic priority.​