Application Of Titanium Alloy Materials On Ships
Titanium and titanium alloy materials are widely used on ships. Except for ship accessories and cabin facilities, all large equipment and parts may use titanium and titanium alloy materials, such as electronic information systems, power systems, auxiliary systems, hull structures, propulsion systems, etc. Foreign titanium alloy materials are mainly used in hull structural materials, ship pumps, valves, pipes and other accessories, power drive devices, heat exchangers, condensers, coolers, evaporators, acoustic devices, etc.; domestic titanium alloy materials are mainly used in submersibles, power drive devices, shipborne radars, electronic equipment, fasteners, etc.
1. Shell (pressure resistance)
In the field of ships, submersibles and submarines are mainly used for titanium alloy pressure shells. Titanium alloys have the characteristics of high specific strength, good corrosion resistance, and non-magnetic properties, making them high-quality materials for manufacturing pressure shells of deep-sea equipment.
Russia is the first country to use titanium alloy pressure shells on nuclear submarines, and it is also a world technology leader. Since the 1960s, Russia (the former Soviet Union) has manufactured a series of titanium alloy submarines. At first, Russia built the No. 661 titanium alloy cruise missile nuclear submarine, which was a test boat. Later, Russia successively built 7 "Alpha" class titanium alloy submarines, 1 "Mike" class submarine, and 4 "Sierra" class submarines. These nuclear submarines are all attack types, among which the "Alpha" class titanium alloy submarine uses 3,000 tons of titanium alloy. The "Typhoon" class nuclear submarine made by Russia is the largest submarine in the world in terms of volume and tonnage, and its titanium consumption reaches 9,000 tons.
At present, Russia's latest generation of "Borey" class nuclear submarines also use titanium alloy pressure hulls.
Another important application of titanium alloy pressure hulls is deep-sea submersibles. The "Jiaolong" manned submersible is a manned submersible independently developed by my country, with a designed maximum diving depth of more than 7,000 meters. The pressure hull of the "Jiaolong" manned submersible is made of titanium alloy. At present, most of the world's major deep-sea manned submersibles use titanium alloy materials as the preparation material for the pressure hull. For example, the shell materials of deep-sea manned submersibles such as the US Alvin and NewAlvin, China's Jiaolong, France's Nautile, and Japan's Shinkai 6500 are all titanium alloys [9]. Titanium alloy has become the preferred material for the pressure-resistant shell of deep-sea submersibles.
2. Power propulsion device
Due to the influence of seawater and marine climate, the propeller material of the ship needs to have higher corrosion fatigue strength and cavitation resistance. Compared with copper alloys and steel, titanium alloy has advantages in corrosion fatigue strength and cavitation resistance. In addition, due to the low density of titanium alloy, when making propellers of the same size, the mass of titanium alloy propellers is smaller than that of other commonly used materials. Therefore, the driving efficiency of ships using titanium alloy propellers is higher. Combined with the high corrosion fatigue strength and cavitation resistance of titanium alloy propellers, their maintenance and care will be easier, extending the service life of the propeller. Titanium alloy is an ideal material for ship propellers.
Russia, the United Kingdom and other countries began to try to use titanium alloy propellers on ships as early as the 1960s. For example, Russia uses titanium alloy propellers in its "Alpha" class and "Mike" class nuclear submarines. The United States has also used titanium alloy propellers on many ships. For example, the US Navy uses a three-blade, detachable, supercavitating titanium alloy propeller with a diameter of 812.8mm in its 50t research submarine chaser. The "Asheville" high-speed gunboat uses a four-blade variable pitch titanium alloy propeller. The large US military hydrofoil "Plainview" uses a four-blade, detachable, supercavitating titanium alloy propeller made of Ti-6Al-4V material with a diameter of 1.52m. my country has also successfully developed a variety of titanium alloy propellers and successfully used them on many ships. For example, the Ti-5Al-2.5Sn and Ti-6Al-4V titanium alloy hydrofoil propellers were successfully developed in 1972 and have been used on many ships so far. Years of use have shown that titanium alloy propellers have strong corrosion resistance and their service life is three times that of traditional copper alloy propellers.
In addition to ship propellers, titanium alloy materials are also used in ship engines. For example, the atomic-powered icebreakers made in Russia use steam engines containing titanium alloy materials. The use of titanium alloy propulsion devices can prevent ships from being affected by large induced currents generated by cutting the earth's magnetic lines when sailing. In addition, some ships' water jet propulsion devices also use titanium alloy materials, such as the US SES-100A test boat and Japan's "PT-10" torpedo boat. Their water jet propulsion devices use industrial pure titanium and titanium alloy forgings, which reduces the weight of the device and improves the efficiency of the water jet propulsion device.
3. Pumps, valves, pipes and their accessories
Russia's requirements for the operation of ship pipeline systems are that structural materials should be guaranteed to have a service life of 8 to 9 years before the first dock repair, and the service life before the system is completely replaced should not be less than 15 years. This requirement can ensure that all levels of ships can serve effectively for 25 to 30 years. Ships operate at sea, so pumps, valves, pipes and other accessories on ships face the test of severe marine environments.
Russian civilian ships' piping systems generally use M3C copper pipes and MH-5-1 copper alloy pipes according to the speed of the water flow, while valves, pumps, and heat exchangers use copper alloys. If the ship's pipes use copper alloy materials, they may have been corroded and damaged in the second year, making it difficult to meet the above-mentioned use requirements. In order to meet the use requirements, the thickness of the pipe may need to be thickened, and at the same time, the diameter of the pipe needs to be expanded to ensure the water flow speed. The weight and cost of the ship's overall piping system have increased.
However, Russian warships' pumps, valves, pipes, etc. use more titanium alloy materials. Warships have been in service for a long time, and their use practice has proved that titanium alloy pipes, valves, pumps, heat exchangers and other products have strong resistance to seawater corrosion and have a long service life. If all titanium materials are used to manufacture the ship's water intake system, the system life can be significantly extended and the reliability of use can be improved.
The U.S. Navy uses titanium alloy piping systems on ships. Compared with traditional copper-nickel alloy pipes, titanium alloy has strong corrosion resistance. Even in high-speed flowing seawater (at a flow rate of 13m/s), it will not be washed and corroded by seawater. It is particularly suitable for pipelines with moving seawater, high flow rate and high pressure as the working medium. Therefore, under the condition of ensuring the same seawater flow rate, the high corrosion resistance of titanium alloy allows the pipeline to be designed to be thinner, the diameter of the pipeline becomes smaller, the space occupied by the ship becomes smaller, the flexibility of layout is enhanced, and the maintenance cost is also reduced. In addition, the density of titanium alloy is small, about half of that of copper-nickel alloy, and the quality of the pipeline manufactured by it is small, which reduces the equipment used to assist in supporting the pipeline. The load of the ship is reduced and the fuel consumption is reduced.
4. Ship acoustic device
Titanium alloy materials can also be used for acoustic devices on ships, such as sonar domes, hydroacoustic transducer components, microphones, telephone parts, etc. Sonar is the most effective equipment for ships to detect targets underwater. my country mostly uses stainless steel and fiber-reinforced fiberglass, but compared with titanium alloy materials, its sound permeability and collision resistance are relatively weak. Russia has applied titanium alloy sonar domes to the Kursk nuclear submarine, Minsk aircraft carrier, Kiev aircraft carrier, etc., and the actual sonar detection effect is good.
