Complete Technical Specifications for BV Grade AH32 Shipbuilding Steel Plates

1. Chemical Composition

BV AH32 is a fully killed, fine-grained, low-alloy structural steel for marine applications that strictly complies with BV marine specifications and features an optimized chemical composition that balances strength, toughness, and weldability. Its chemical composition (wt%) is specified as follows:

1) Compared to standard-strength marine steels, AH32 contains trace amounts of niobium (Nb) to refine the grain structure and enhance structural strength and fatigue resistance.

2) The carbon equivalent (CEV) is controlled at ≤0.40% across all thickness grades, ensuring excellent weldability and minimizing the risk of cold cracking during welding.

3) Ultra-low levels of harmful impurities eliminate the risk of microdefect propagation, ensuring structural stability under long-term seawater corrosion and alternating load conditions.

2. Mechanical Properties

The core mechanical properties of BV AH32 shipbuilding steel plates are as follows:

The above parameters fully meet the load-bearing, deformation resistance, and fatigue resistance requirements for conventional ship hulls, deck structures, and offshore auxiliary facilities.

3. Impact Properties

BV AH32 shipbuilding steel plates must pass the BV-approved 0°C low-temperature impact test, which is the basic low-temperature impact requirement. The impact performance parameters are as follows:

The key differentiating advantage lies in the mandatory 0°C Charpy V-notch impact test, in which the impact energy absorption must meet the values specified in the BV Code, effectively suppressing brittle fracture and crack propagation under mild low-temperature environments and alternating wave loads. This stable low-temperature toughness makes AH32 the preferred high-strength steel for projects in temperate waters, offering significant advantages over ordinary-strength steel grades in terms of structural durability and load-bearing capacity.

4. BV Ship Classification Certification Rules

BV AH32 shipbuilding steel plates are produced and inspected in accordance with BV’s standardized end-to-end production and inspection specifications and are suitable for conventional high-strength offshore engineering projects.

1) The entire production chain—including converter smelting, LF refining, continuous casting, controlled rolling, and normalizing heat treatment—must comply with BV standards for the construction of merchant ships and offshore structures.

2) Each batch must undergo 100% sampling inspection for chemical composition, room-temperature mechanical properties, and impact toughness at 0°C; dimensional accuracy, surface quality, and internal defect detection are classified as zero-tolerance core acceptance criteria.

3) Qualified finished products must obtain an EN 10204 3.2 certificate and an official BV classification survey report, which are mandatory qualification documents for conventional merchant ships and general offshore engineering projects classified by BV worldwide.

5. Specification and Dimension Range

BV AH32 shipbuilding steel plate specifications cover the diverse needs of bulk carriers, container ships, general cargo ships, and temperate offshore engineering projects:

Thickness range: 2 - 150 mm

Maximum width: 5,000 mm

Maximum length: 24,000 mm

The above specifications comprehensively cover conventional structural components such as hull plating, decks, bulkheads, and platforms.

6. Dimensional Tolerance Range

Dimensional tolerances comply with the stringent BV standards for high-strength marine steel:

Thickness tolerance: ≤ ±0.20 mm

Flatness error: ≤ 1.8 mm/m

Edge perpendicularity and flatness: Meet assembly requirements

High-precision dimensional control effectively eliminates stress concentrations during assembly, ensures structural tightness, and prevents the initiation of localized cracks under long-term, routine marine service conditions.

7. Delivery Conditions

1) Hot-Rolled (AR)

Suitable for standard plates with a thickness of ≤50 mm; Grade A room-temperature impact performance can be directly achieved through hot rolling.

2) Controlled Rolling (CR)

Refines the grain structure through the rolling process without the need for subsequent heat treatment; commonly used for medium-thickness plates.

3) TMCP (Thermomechanically Controlled Rolling)

A combined process of controlled rolling and accelerated cooling that yields the finest grain structure, excellent low-temperature toughness, lower carbon equivalent, and superior weldability; it is the mainstream process for thick plate production.

4) Normalizing (N)

The mandatory delivery condition for plates thicker than 50 mm. It produces a uniform microstructure and ensures stable room-temperature impact properties.

5) Quenching + Tempering (Q+T)

Suitable for ultra-thick plates and applications with specific requirements for high strength and high toughness.