Aluminum Steel Sheet for Shipbuilding
In shipbuilding, material selection has always been crucial in balancing safety, efficiency, and cost. In the past, while pure steel met strength standards, its heavy weight increased fuel consumption. Pure aluminum, while lightweight, struggled to withstand the loads and corrosion of complex marine environments. The emergence of aluminum steel sheets fills this gap.
Why is it needed?
A pure steel hull (especially the superstructure and deck areas) significantly increases the ship's weight, leading to a deeper draft, reduced speed, and an increase in fuel consumption of 10%-15% annually. Aluminum-steel composite panels, with their "steel base (load-bearing) and aluminum cladding (protective)" structure, maintain strength similar to pure steel while being 30%-40% lighter than the same volume of pure steel, directly reducing ship energy consumption.
Salt spray and seawater immersion in marine environments can cause significant corrosion of pure steel within 3-5 years, requiring frequent rust removal and painting. While marine grade aluminum sheet is highly corrosion-resistant, its tensile strength is only one-third that of mild steel, making it unable to withstand the loads of critical hull components. The aluminum cladding of aluminum-steel composite panels isolates the steel substrate from seawater, resulting in a corrosion rate that is only one-tenth that of pure steel. At the same time, the steel substrate provides structural strength, achieving a two-in-one solution of "protection and load-bearing."
If aluminum and steel are directly joined together on a ship, the two metals will form a galvanic cell in seawater, accelerating corrosion of the aluminum components (thickness loss can reach 0.5mm per year). However, aluminum-steel composite panels utilize metallurgical bonding technology to create a seamless interface between the aluminum and steel, eliminating galvanic corrosion at the root and eliminating the cost and process of installing additional insulating gaskets.
Three Core Benefits
1. Optimizing the hull structure and improving navigation stability
Using aluminum-steel composite panels in non-load-bearing areas such as the superstructure (wheelhouse, accommodation) and deck platforms can lower the hull's center of gravity and reduce rolling amplitude during navigation (measured roll angle reduction of 8%-12%). This is particularly suitable for ships with high stability requirements, such as container ships and ro-ro passenger ferries.
2. Extending the lifespan of key components and reducing maintenance costs
Cargo holds, ballast water tanks, and seawater cooling system piping, areas in direct contact with seawater, are particularly susceptible to corrosion. Using aluminum-steel composite panels extends the maintenance interval for these areas from 1-2 years to 5-8 years, saving 100,000 to 300,000 yuan in annual maintenance costs per ship.
3. Adapting to modular shipbuilding improves construction efficiency
Aluminum-steel composite panels can be prefabricated to designed dimensions, eliminating the need for on-site joining of aluminum and steel, reducing welding steps (increasing welding efficiency by 40%). For example, when a shipyard was building a 50,000-ton bulk carrier, the use of composite panels reduced the superstructure construction period by 15 days.
To ensure ship safety, aluminum-steel composite panels must meet strict industry standards. Key indicators include:
Interface bonding strength
This is the lifeline of the composite panel and must meet the requirements of GB/T 16957, "Multi-layer Metal Composite Panels": Delamination at the composite interface must be eliminated during the tensile test, and the bonding strength must be ≥150 MPa (equivalent to withstanding a tensile force of 15 kg per square centimeter). After the bending test (180° cold bending), the interface must be free of cracks.
Dimensional and Appearance Accuracy
Aluminum cladding sheet size like thickness deviation must be controlled within ±0.1mm (especially for the aluminum cladding, which must evenly cover the steel substrate and within 5% of the design value). The surface must be free of scale and pitting, and scratch depth must be ≤0.05mm to prevent coating peeling during subsequent painting. Corrosion Resistance
It must pass the neutral salt spray test (GB/T 10125): After 1000 hours of continuous spraying, the aluminum coating corrosion rate is ≤ 0.005mm/year, with no exposed steel substrate. Furthermore, the panels must pass a seawater immersion test (6 months), with no signs of electrochemical corrosion on the interface.
Classification Society Certification
Composite panels used on ocean-going vessels must also be certified by international classification societies (such as CCS and Lloyd's Register). Each batch of products must provide material certification, mechanical properties test reports, and corrosion test reports to ensure traceability.
Original Source:https://www.marinealu.com/a/aluminum-steel-sheet-for-shipbuilding.html
Tags: marine grade aluminum sheet ,