"Marine metal" titanium and titanium alloy are widely used in shipbuilding
Shipping service environment for harsh oceanic climate, due to the long time contact with seawater, hull and equipment, components, such as high temperature exhaust pipe, the water valve and pump, screw, etc.) are easy to corrode, the protective measures and extremely complicated and difficult, so the ship with material put forward special technical requirements: (1) seawater corrosion resistance.(2) good stability under high and low temperature environment.(3) safe and reliable, large bearing, less maintenance or convenient maintenance, bending, welding and other machinability.
1. Advantages of titanium and titanium alloy as Marine materials
Titanium and titanium alloy with its own excellent characteristics, almost meet all the requirements of ship materials, can be called a near-perfect ship materials. Its advantages are as follows:
(1) light weight, higher than strength. Titanium has a density of 4.5g/cm3, higher than aluminum at 2.7g/cm3, and lower than iron at 7.9g/cm3, only 57% of iron. Titanium is less than twice as dense as aluminum but three times as strong. In industrial engineering application, titanium alloy can be used as the preferred material when metal with high specific strength is selected. Under the same conditions, titanium submersibles can reach depths of up to 10,000 meters, while steel submersibles can go much deeper. In addition, titanium magnetic field is zero, in any intensity of the magnetic field will not be disturbed, so in the sea battle, the use of mines, torpedoes and other magnetic mine attack weapons, the hull of the titanium alloy is not offensive, has a good anti-monitoring role, this feature is favored by military engineering applications.
(2) good corrosion resistance in Marine climate. When titanium alloy is in the air and some oxygen-containing media, because titanium and oxygen have a strong affinity, the surface can quickly form a layer of dense, strong adhesion and good stability of the oxide film, in many media is not easy to be destroyed, so as to protect the titanium matrix. Studies have shown that the corrosion rates of titanium and titanium alloys in the south China sea, north China sea and east China sea in the past 16 years are almost zero, no matter in the full immersion zone, tidal range zone, splash zone or Marine climate. Therefore, the ship using titanium alloy manufacturing on the one hand can extend the service life, on the other hand can reduce the late because of the surface corrosion and take protective treatment costs.
(3) excellent comprehensive performance. Titanium alloy can be cold and hot forming, free forging, extrusion and welding and other processing, with good processing adaptability. Research shows that the titanium alloy within 60 ~ 20 ℃ impact toughness test of itself does not exist brittle transition point. In addition, compared with aluminum alloy and steel, titanium alloy has the best heat resistance, low temperature resistance and fracture toughness.
2. Application status of titanium alloys in ships
At present, Russia, the United States, Japan and China are the main countries that research and develop Marine titanium alloys. Russia is the first country in the world to study the application of titanium alloy in ships. It has a complete set of system documents for engineering application reference (related design, material selection and process, etc.).Experts from the former Soviet union demonstrated to the world the feasibility of building attack nuclear submarines with titanium alloy through the "papa" class all-titanium cruise missile test ship. Since then, Russia has developed the "barracuda" class and "condor" class titanium alloy submarines. Carding Russian Marine titanium alloy found: Russian Marine titanium alloy brand, simple composition, pay more attention to the alloy series and application design of the overall study.
The United States first studied the titanium alloy for aviation, and then based on the titanium alloy for aviation, formed the Marine titanium alloy system according to the service environment of the ship, and successfully applied the titanium alloy to various power submarines, seawater pipeline systems and the pressure-resistant shell of deep-sea submersible, such as Ai vin number, sea-cliff number deep-sea submersible. American Marine titanium alloy brand is less than Russia, more attention to the application of such as the improvement of corrosion resistance.
The research and application of Marine titanium alloy in Japan has developed rapidly. At present, the main brands used are pure titanium, Ti-6AL-4V and Ti-6AL-4V ELI, which are mainly used in the pressure-resistant shell and piping of deep-diving vehicle.
With the rapid development of science and technology, the cost of titanium alloy is gradually reduced, and the application of titanium and titanium alloy in ships shows many advantages such as the lightness, high speed and high safety and reliability of equipment. Marine titanium alloy is bound to usher in rapid development.