The application prospects of titanium as a naval engineering material

Titanium is hailed as the "ocean metal" due to its excellent properties such as light weight, high strength-to-weight ratio, corrosion resistance, and non-magnetism. It is widely regarded as the most promising metal material for naval engineering and has been widely used in various fields such as surface ships, underwater submarines, deep submersibles, underwater weapons, communication equipment, etc. worldwide.

Research has shown that titanium has excellent resistance to seawater corrosion. A 5-year natural seawater corrosion test has demonstrated that titanium has no tendency for stress corrosion and does not experience crevice corrosion in natural seawater. Titanium also has strong resistance to erosion by water flow. Comparative tests have shown that nickel alloys have poor erosion resistance when the flow velocity exceeds 5 m/s, while titanium alloys remain intact under erosion by water flow at 7 m/s and above. Chloride ions in seawater are difficult to damage the passivation film on titanium, thus reducing the occurrence of pitting corrosion, intergranular corrosion, and stress corrosion. Moreover, unlike stainless steel, titanium alloys do not experience changes in corrosion resistance due to welding or cold processing. Regarding the problem of marine organism attachment, actual investigations on underwater submarine sea access systems have shown that marine organisms grow very little and no marine organisms grow on the main circulation water system.

The United States, Japan, and Russia have successfully used titanium in deep submersibles, achieving diving depths of 5,000, 6,000, and 6,500 meters respectively. Russia is the country that uses titanium most extensively in nuclear submarines, with the most typical example being the all-titanium nuclear submarine, which uses 9,000 tons of titanium per vessel. Other nuclear submarines use titanium for condensers, heat exchangers, sonar guide covers, sea access piping systems, and bellows. Titanium is also widely used in diesel engine gas exhaust systems, sonar guide covers, sea access piping systems, bellows, pumps, and valves in conventional submarines. The sonar guidance systems, sea access piping systems, bellows, pumps, and valves of Russian missile destroyers and aircraft carriers are also extensively used titanium. Their main ships have all passed tests in global sea areas such as the Arctic, Antarctic, equator, Pacific Ocean, Indian Ocean, and Atlantic Ocean, solving issues such as design allowable stress and safety factor selection. The United States and Japan have also used titanium in various ship propulsion systems, effectively overcoming the adverse effects of copper alloy cutting Earth's magnetic lines of force during navigation, which led to large induced currents. The British North Sea oil field used titanium alloy instead of Cr-Mo alloy steel for high-pressure pipelines, reducing weight and maintenance costs, and lowering oil extraction costs by 40%. They formed a 400-meter-long, 900-ton super oil pipeline using 30 tubes with a size of 609mm × 25mm × 1460mm to be used in an oil extraction system at a depth of 350 meters under the sea.

A large number of international application examples have fully proved that titanium and titanium alloys are undoubtedly the most suitable materials for use in seawater conditions. Russia's extensive use of titanium alloys in naval equipment and successful passage of tests in actual applications is a powerful example. Currently, China's titanium production level is comparable to that of foreign countries, and the development of China's titanium industry can meet the large-scale titanium demand of the navy. However, there is a considerable gap between China's titanium application level in naval engineering and the current situation in the international community. The research work in this field is still in a scattered and sporadic state. To build a powerful navy for our country, we should lead the coordination and cooperation of various departments with scientific development, improve the level, reduce costs, and quickly promote the application and popularization of titanium in naval engineering.