Why is titanium suitable for marine engineering?
1. Low density, high strength and high specific strength.
Titanium has a density of 4.51g/cm3, 57% of steel, less than twice the proportion of titanium to aluminium, and three times the strength of aluminium. The specific strength of titanium is the largest in common industrial alloys. High specific strength can promote the miniaturization and lightweight of marine equipment, increase the speed, buoyancy and maneuverability of submarines, and increase the depth and payload of deep submarines. Therefore, titanium is an indispensable key structural material for marine engineering.
2. Excellent corrosion resistance
Titanium is the best corrosion resistant material known at present, even in polluted seawater, hot seawater (below 120 C), sea mud and flowing seawater, it has good corrosion resistance. Its excellent corrosion resistance is due to its good self-passivation. When damaged to some extent, the surface oxide film or passivation film can be repaired and restored quickly by itself. That is to say, in the ocean, titanium is almost non-corrosive. There is a strong and tough oxide film on the surface of titanium, so its corrosion resistance is better than that of other metals.
In the design of anti-corrosion equipment, it can greatly reduce the corrosion margin in the thickness direction of bearing structural parts and save construction materials; anti-corrosion equipment can be designed with the same life as the main body, reduce maintenance frequency, greatly reduce maintenance costs, and enhance the service capacity of equipment; titanium equipment does not need coating when used in the ocean. The protection simplifies the manufacturing process, shortens the construction period and reduces the manufacturing cost.
3. Resistance to seawater erosion and cavitation
Most materials have a critical velocity, beyond which the oxide film on the surface will be washed away and corrosion will accelerate. This accelerated corrosion is erosion corrosion. The erosion and corrosion resistance of titanium tubes is much higher than that of copper and copper alloy tubes, and the critical velocity of titanium in seawater is more than 27 m/s. Various erosion corrosion tests show that titanium is very resistant to this corrosion. Titanium permits the manufacture of pipeline systems with smaller diameter, thinner wall and higher flow rate to achieve miniaturization and lightweight equipment. At the same time, the anti-cavitation experiment shows that titanium is one of the most anti-cavitation metals.
4. High impact resistance
Titanium and titanium alloys have the best impact resistance, which is conducive to the ability of marine equipment to withstand the periodic impact of sea waves and improve the safety and reliability of equipment.
5 nonmagnetic
Titanium is nonmagnetic and is very suitable for minimizing electromagnetic interference. For submarines, it can greatly reduce the magnetic physical field effect of submarines, thus reducing the possibility of their detection by anti-submarine aircraft magnetic detectors; for titanium ships and naval vessels, it can increase concealment and avoid being attacked by magnetic mines. For submarine hull, it will not cause mine explosion. At the same time, it is also conducive to improving the anti-magnetic interference ability of detection instruments and tools and ensuring the accuracy of signals.
6. High Permeability
Titanium is used as sonar dome material for submarines and aircraft carriers, which can improve the sonar detection sensitivity and detection distance of equipment, and improve the efficiency and safety reliability of equipment.
7. Excellent Processing Performance
Titanium metal has good machinability and can be made into practical engineering materials of various shapes and specifications, including plates, rods, pipes, wires, strips, foils, forgings, castings, weldments, etc. Most titanium and its alloys have good weldability, and the strength coefficient of welds can reach more than 0.9. There are few delayed cracks after welding of titanium metal. Its equipment generally does not need post-weld heat treatment, which is conducive to the construction of large-scale engineering equipment such as ships and marine engineering.
8. Green recycling
Titanium metal products have a long service life in marine environment. After being discarded, they can be processed into lower-grade titanium alloy materials for use, with little weight loss and high recovery rate.
