Technical Specifications for LR Grade E Shipbuilding Steel Plates

LR Grade E shipbuilding steel plate is a ordinary-strength hull structural steel certified by Lloyd’s Register (LR). It is the steel grade with the highest low-temperature toughness in the LR Grade A/B/D/E series and is specifically designed for polar and cryogenic marine environments. Compared to LR Grade A/B/D, this steel grade offers significant improvements in low-temperature toughness, metallurgical purity, and microstructural stability. Its production and inspection strictly adhere to LR shipbuilding codes, and it is widely used in polar-class vessels, cryogenic offshore engineering equipment, and critical load-bearing structures in extremely cold regions.

1. Chemical Composition

LR Grade E is a fully quenched, ultra-low-carbon marine steel with strictly controlled impurities, optimized for low-temperature toughness and structural stability at -40°C. Its chemical composition complies with the LR Rules for Marine Steels:

The content of impurities such as carbon, sulfur, and phosphorus has been further reduced to eliminate internal microstructural defects that cause low-temperature brittle fracture.

The carbon equivalent (CEV) is strictly controlled below 0.40% to ensure excellent weldability, cold formability, and the ability to maintain low-temperature toughness.

2. Mechanical Properties

All LR Grade E shipbuilding steel plates have undergone authoritative testing by LR and possess stable mechanical properties suitable for polar marine environments:

3. Low-Temperature Impact Toughness

The core performance indicator is the -40°C Charpy V-notch impact test, which ensures stable low-temperature toughness and resistance to brittle fracture in polar waters, making it an indispensable key material for marine structures in extremely cold environments.

4. Dimensional Range

LR Grade E shipbuilding steel plates cover a wide range of specifications to meet various polar shipbuilding and construction needs:

Thickness: 5 - 150 mm

Maximum width: 4,000 mm

Maximum length: 18,000 mm

5. Tolerance Standards

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

Thickness tolerance: ±0.20 mm

Flatness error: ≤ 1.5 mm/m

Edge straightness and perpendicularity: near-zero deviation

Strict dimensional control effectively eliminates low-temperature stress concentrations caused by assembly errors, enhancing the overall structural safety and in-service reliability of polar engineering projects.

6. Full-Process LR Certification Requirements

LR Grade E shipbuilding steel plates are subject to the most stringent full-process production and inspection specifications among LR ordinary-strength marine steels. These specifications cover processes such as ultra-pure smelting, controlled rolling and cooling, low-temperature microstructural stabilization heat treatment, and high-precision machining, all of which must comply with the LR Polar Shipbuilding Rules.

Each batch must undergo 100% sampling inspection for chemical composition and mechanical properties, with impact toughness at -40°C serving as the core acceptance criterion; qualified products are issued an EN 10204 Type 3.2 certificate.