Technical Specifications and Certification Requirements for LR Grade DH36 Shipbuilding Steel Plates

1. Chemical Composition

LR Grade DH36 is a fully killed, fine-grained, low-alloy steel. Its chemical composition strictly complies with LR specifications, with typical control ranges as follows (wt%):

Compared to LR AH36, LR DH36 further tightens the limits for sulfur and phosphorus impurities. It also utilizes aluminum microalloying to refine the grain structure, eliminate the risk of low-temperature brittle fracture, and enhance microstructural density.

2. Carbon Equivalent (CEV)

* Calculation formula (IIW): CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

It balances high strength with cold formability and weldability.

3. Mechanical Properties

LR Grade DH36 shipbuilding steel plates must pass official LR inspection; the key mechanical properties are as follows:

4. Low-Temperature Toughness

LR Grade DH36 shipbuilding steel plates must meet the following low-temperature impact test requirements:

The key distinguishing factor from LR AH36 shipbuilding steel plates is the -20°C Charpy V-notch impact test, in which the impact energy must meet LR code requirements to ensure no brittle fracture occurs during service in waters with seasonal low temperatures.

This performance characteristic makes LR DH36 the mainstream low-temperature, high-strength steel grade for high-load vessels and offshore structures in cold climates.

5. Dimensions and Specifications

LR DH36 shipbuilding steel plates are available in a wide range of specifications to meet the demands of large ship hulls and offshore structures:

Thickness: 5 - 150 mm

Maximum width: 4,800 mm

Maximum length: 24,000 mm

6. Tolerance Standards

Dimensional tolerances comply with LR’s high-precision standards:

Thickness tolerance: ≤ ±0.20 mm

Flatness error: ≤ 1.5 mm/m

Edge flatness and perpendicularity: Meet zero-deviation requirements

Strict control of dimensional tolerances effectively prevents stress concentration during assembly, ensuring the structural safety and stability of heavy-duty offshore facilities in cold regions during long-term service at low temperatures.

7. Full-Process LR Certification Requirements

1) LR DH36 shipbuilding steel plates must undergo full-process quality control in accordance with LR regulations, covering processes such as converter smelting, LF refining, vacuum degassing, controlled rolling and cooling, microstructural homogenization, and precision machining.

2) Each batch of products must undergo comprehensive testing for chemical composition, mechanical properties, and impact toughness at -20°C; carbon equivalent control is a key acceptance criterion.

3) Qualified finished products must be accompanied by an EN 10204 Class 3.2 certificate and an official LR inspection report, which are mandatory certification documents for LR-classed seagoing vessels and heavy-duty offshore structures in cold regions worldwide.