The wider application of titanium tubing opens up new opportunities for the desalination and shipbuilding industries!

Titanium resistance to seawater corrosion than all other metals are better, both in the static or high-speed flow of seawater titanium has a special stability. Titanium is therefore an ideal material for desalination plants. The number of applications of titanium in this field will be increasing. Titanium seawater and ocean air corrosion resistance is very strong, and strong, light weight, is the shipbuilding industry's ideal structural materials, has been widely used in a variety of ships, deep-water submarines in many parts.
At present, desalination has spread to more than 60 countries and regions around the world, the world has more than 6 million desalination plants, desalination of seawater daily output of about 35 million tons or so, and with an annual rate of more than 10% in the increase. Desalination has become one of the best ways to solve the water shortage problem. At present, the world's mainstream desalination methods are mainly multi-stage flash (MSF), low-temperature multi-effect distillation (LT-MED) and reverse osmosis membrane (RO) method. Each of the three methods has its own advantages and disadvantages, and the conditions and scope of application are also different. China mainly applies LT-MED and RO methods, and several desalination projects will be launched in China in the next few years. In the next 3-5 years, seawater desalination will have a lot of space for development.
Depending on today's technology for large-scale application of seawater desalination has a cost advantage, compared with the South-to-North Water Diversion for tons of water cost is lower, the state has introduced a series of incentives, the next 10 years, the scale of seawater desalination will be 5 times as large as the present. Desalination equipment with titanium alloy instead of copper alloy is the future trend. Titanium multi-faceted advantages determine the future in the field of seawater desalination pipe widely used space, it is expected that the next ten years, China's seawater desalination titanium pipe demand is about 9500-23520 tons, the global demand is about 140.63-281.25 million tons. Although the preliminary domestic demand is not large, but the domestic demand only accounts for 1.6% of the total international demand, it can be said that the overall development space is very huge.

First, the main characteristics of titanium tubing for desalination:
1, low density, high specific strength (strength / specific gravity)
Titanium metal density of 4.51g/cm3, higher than aluminum and lower than steel, copper, nickel. But the specific strength is located in the top of the metal, is 3 times that of stainless steel, is 1.3 times that of aluminum alloy;
2, good corrosion resistance
Titanium is a very active metal, its equilibrium potential is very low, in the medium of thermodynamic corrosion tendency. But in fact, titanium is very stable in many media, such as titanium in the oxidizing, neutral and weak reducing medium is corrosion resistant. This is because titanium and oxygen have a great affinity, in the air or oxygen-containing media, titanium surface to generate a layer of dense, strong adhesion, large inert oxide film, protecting the titanium substrate from corrosion. Even due to mechanical wear and tear will soon be self-healing or regeneration. This shows that titanium is a metal with a strong passivation tendency. The oxide film of titanium at temperatures up to 315°C maintains this property.
3, good heat transfer performance
Although the thermal conductivity of titanium metal than carbon steel and copper, but because of titanium's excellent corrosion resistance, so the wall thickness can be greatly reduced, and the surface of the heat transfer with the steam for the drip condensation, reducing the heat group, too, the surface of the non-scaling can also reduce the thermal resistance, so that titanium's performance in the heat transfer is significantly improved.
4, good heat resistance
The new titanium alloy can be used for a long time at a temperature of 600 ℃ or higher.
5, good chemical resistance to low temperature performance
Titanium alloy TA7 (Ti-5Al-2.5Sn), TC4 (Ti-6Al-4V) and Ti-2.5Zr-1.5Mo and other low-temperature titanium alloys represented by its strength increases with the lowering of the temperature, but the plasticity change is not significant.
6, tensile strength and its yield strength
This property shows that the yield strength ratio (tensile strength / yield strength) is high, indicating that the titanium metal material in the molding of plastic deformation is poor. Due to the large ratio of yield limit to modulus of elasticity of titanium, so that titanium molding rebound capacity.
Second, the desalination equipment in the titanium tube will gradually replace the original copper alloy tube, compared with the two, titanium tube has the following advantages:
1, titanium pipe with less material. Under the same operating conditions, titanium tube wall thickness is thinner, less pipe dosage. In general, copper alloy tube wall thickness of 0.9mm-1.2mm; with titanium tube instead of corrosive small places, available wall thickness of 0.5mm thin-walled tube.

2, titanium tube of good thermal conductivity. Titanium thermal conductivity of 17W / (m - k), aluminum brass for lOOW / (m - k), 70 / 30 copper for 29W / (m - k), titanium thermal conductivity of the smallest. But the use of thin-walled titanium tubes, thermal conductivity, although worse than aluminum brass, but comparable to 90/10 copper, than 70/30 copper.
3, titanium tube is more cost-effective. Titanium tube prices can compete with copper alloy tube, due to the low density of titanium, the same wall thickness, the same length of the titanium tube quality is only 50% of the copper alloy tube, when the titanium tube wall thickness of 50% of the copper alloy tube, the same heat transfer area of the titanium tube quality of the copper alloy tube is only 1 / 4 can be seen, the titanium tube is competitive in terms of price.
4, the service life of the titanium tube is longer. As seawater is often mixed with sediment, sea life, they are attached to the heat transfer tube and tube ends, will erode the copper alloy tube, copper alloy will also be subject to seawater corrosion of Br-. Titanium tube will not appear this problem, especially in order to kill bacteria in seawater, have to inject oxygen, more need to use good corrosion resistance of titanium tube.
Third, the development and application of foreign titanium materials
Hitachi, Mitsubishi and Toshiba production of power station condenser, the use of a thick 0.5mm titanium welded tubes, Mitsubishi, Kawasaki, Hitachi, Mitsui and Kobe Steel and other companies to produce seawater desalination devices, the use of a thick 0.5mm - 0.7mm titanium welded tubes. To 1983, in 16 years, Japan has produced 4038t of thin-walled titanium welded tubes used in desalination equipment around the world, and so far there has been no damage due to seawater corrosion.
(1) Ventilation condenser and jet pressurizer
The real seawater desalination equipment in Japan is 2650t/ d seawater desalination equipment built by Matsushima Carbon Mining Co. in 1967. The heat transfer tubes and tube plates of the ventilation condenser and the jet compressor of the plant could not be made of copper alloy due to corrosion by Br- in seawater, and after replacing them with titanium, no failure due to corrosion has occurred.
(2) Heat release section condenser
Multi-stage flash condenser is seawater as cooling water, cooling water vapor generated at all levels of the flash chamber, due to seawater is often mixed with sediment, sea life, they are attached to the heat transfer tube and tube ends, erosion of copper alloy tube. Therefore, nowadays almost all MSF type desalination equipment use titanium tubes on the heat transfer condenser. Especially when oxygen has to be injected in order to kill bacteria in seawater, it is necessary to use titanium tubes with good corrosion resistance.
(3) Heat recovery section condenser
Heat recovery department condenser heat transfer area is large, due to economic reasons, now usually use copper alloy tube, only in special occasions to use titanium tube, such as containing ammonia or hydrogen sulfide and other pollutants of the medium on the copper alloy corrosion is intense. 1977, exported to Germany's 3600t/ d MSF desalination device, because it is ammonia accessory equipment, can not use copper alloy, but the use of titanium; due to the corrosion of sulfuric acid and oxygen. Due to the corrosion of oxygen sulfide, 3120t/ dMSP desalination equipment in Peru, the corrosion of aluminum and brass tubes occurred after 1 year of use, and finally all the heat transfer tubes were replaced with titanium tubes.
It is reported that the daily output of 100 tons of desalination equipment with titanium tubes up to 60,000. From 1967 to 1994, in nearly 30 years, a total of 52 sets of production in the energy level of thermal power generation condenser and 7 sets of desalination equipment, a total of 11,000t of titanium welded tubes.
Fourth, shipbuilding industry
With the development of society, mankind's demand for natural resources, the development and application of marine resources is increasingly important, it is said that the 21st century is the century of marine development.
Development of the ocean needs a variety of equipment, and any equipment to achieve the function depends on material technology. Titanium has characteristics adapted to the marine environment, such as corrosion resistance, non-magnetic, high comprehensive mechanical properties and machinability, etc., is a natural structural material for marine equipment. These characteristics of titanium, to the research and development of new ship products, marine engineering machinery and equipment provides an important material technology platform, so from the late 1950s, titanium in the ship and marine engineering applications, not only the field of gradual broadening, but also the amount of increased.

With the development of science and technology, China's shipbuilding industry has formed a technical system of titanium alloy materials for shipbuilding after long-term applied research. In this industry, the use of titanium metallurgical semi-finished products are mainly a variety of different specifications of the plate, forgings, castings, wire and pipe, of which the largest amount of plate, accounting for more than 70%, followed by forgings, about 15%, castings 12%, and the rest of the wire and pipe. To ensure the construction quality of ships and marine engineering equipment, various types of different specifications of titanium isotropy, tissue morphology and grain size moderate, plate production, bending, stamping, welding, forging and casting preparation, manufacturing process technology is the key, in addition, the domestic marine titanium alloy R & D experience also shows that a new titanium alloy material for ship products, must be carried out large-scale structural simulation of the validation test to examine its usability, to establish the corresponding titanium alloy material, the structure of the ship, the structure of the titanium alloy material for the ship products, must be used in the construction of the ship. In order to examine its usability and establish the corresponding experimental technology.
Marine titanium due to a wide range of applications, in addition to the requirements of corrosion resistance in the marine environment, other research priorities are: ① high performance (high strength, impact toughness, fatigue resistance), high functionality (high sound transmission), and adapt to the use of environmental conditions; ② material construction process adaptability, the use of safety and reliability; ③ varieties / specifications series, the material's supporting (such as the corresponding wire material), practicality; low cost. Low cost. Ships and marine engineering is to rely on its performance and quality, but also to see whether its price is acceptable, low cost is the current marine titanium alloy materials and manufacturing process is an important goal of the research, the domestic and foreign low-cost research on titanium alloys is quite active.