(1) The nature of titanium
The appearance of titanium is very similar to steel, with a density of 4.51 g/cm3, which is less than 60% of steel. It is the metal element with the lowest density among refractory metals.
Titanium is very stable in air at room temperature. When heated to 400-550°C, a firm oxide film is formed on the surface to protect it from further oxidation. Titanium has a strong ability to absorb oxygen, nitrogen, and hydrogen. This type of gas is a very harmful impurity to metallic titanium. Even a small amount (0.01% to 0.005%) can seriously affect its mechanical properties.
The mechanical properties of titanium, which are generally called mechanical properties, are closely related to purity. High-purity titanium has excellent machining properties, good elongation, and reduction of area, but low strength, which is not suitable for structural materials. Industrial pure titanium contains an appropriate amount of impurities, has high strength and plasticity, and is suitable for making structural materials.
Among titanium compounds, titanium dioxide (TiO2) has the most practical value. Ti02 is inert to the human body, non-toxic, and has a series of excellent optical properties. Ti02 is opaque, with high gloss and whiteness, high refractive index and scattering power, strong hiding power, and good dispersibility. The pigment made is a white powder, commonly known as titanium white, and is widely used.
(2) Application of titanium
1. Application of titanium and its alloys
The dense metal titanium is highly valued by the aviation industry because of its lighter weight, higher strength than aluminum alloy, and its ability to maintain higher strength than aluminum at high temperatures. In view of the density of titanium being 57% of steel, its specific strength (strength/weight ratio or strength/density ratio is called specific strength) is high, corrosion resistance, oxidation resistance, and fatigue resistance are all strong. 3/4 of titanium alloy is used as Structural materials represented by aviation structural alloys, one-fourth of them are mainly used as corrosion-resistant alloys.
Titanium alloys are divided into low strength and high plasticity, medium strength and high strength, ranging from 200 (low strength) to 1300 (high strength) MPa, but in general, titanium alloys can be regarded as high strength alloys. They are stronger than aluminum alloys that are considered to be medium-strength, and can completely replace certain types of steel in terms of strength. Compared with the rapid decline in the strength of aluminum alloys at temperatures above 150°C, some titanium alloys can still maintain good strength at 600°C.
In addition to strength, titanium alloys can be divided into heat resistance, corrosion resistance, low temperature, and special functions (such as TiNi shape memory alloy, TiFe hydrogen storage alloy) and other titanium alloys according to their uses. According to the phase composition, they can be divided into α, α + β, β and near α, Metastable, and other types. So far, more than 100 types of alloy grades have been put into production, and only more than 10 types are widely used in industry. Among them, Ti-6Al-4V used as structural alloy occupies 60% of the entire sales market of titanium alloys, occupying a dominant position, followed by Ti-5Al-2.5Sn, which has a long-term working temperature of up to 500°C (intensity of 780~ 980 MPa).
However, titanium has two main factors that prevent this resource-rich element from becoming a common metal. The first is cost. According to the US market price, per pound (1 pound = 0.45 kg) titanium ingot billet is 8 to 12 dollars, the aluminum ingot is 1.00 to 1.30 dollars per pound, and carbon steel is 0.20 to 0.40 dollars per pound. But the main factor is that titanium itself is extremely active and difficult to handle. The atmosphere in the furnace must be strictly controlled, and welding must be carried out in an inert atmosphere. Titanium metal has high activity, low thermal conductivity, large deformation resistance, and poor plasticity at room temperature. It is not only easy to bond with the mold during the deformation process, but also has the tendency of tools and abrasives to bond to the hot processing surface during machining. The manufacture of structural parts produces a large number of waste titanium scraps, the so-called residual titanium. Generally, forged titanium ingot processing can produce 70% residual titanium, and sometimes this figure can be as high as 90%.
In order to reduce the burden caused by excessively high costs, on the one hand, the residual titanium treatment process has been developed, and on the other hand, near-net forming, superplastic forming, precision casting, and powder metallurgy, hot isostatic pressing, and diffusion bonding have been developed. For example, powder metallurgy products processed by powdering, forming, sintering, or hot isostatic pressing consolidation methods are near-net-shaped parts, and the material utilization rate is as high as 80%, which not only reduces material consumption but also significantly reduces the amount of cutting processing. Another example is the application of large-scale thin-wall precision casting technology in titanium alloys, which makes the performance of titanium castings close to that of titanium forgings while reducing the cost by about 50%.
The main consumer of titanium and titanium alloys is the aviation industry first. In the 1980s, titanium used in the aviation industry in the United States accounted for 74.8% of the total titanium consumption, Russia, the United Kingdom, etc. were also mainly used in the aviation industry, and 90% of titanium was used in the civil industry in Japan. In recent years, the application of titanium in the non-aerospace industry has continued to increase, and aerospace is still the "main player". Since titanium was used as an engine nacelle and firewall on Douglas DC-7 flights in 1952, many aircraft structural parts have been made of titanium alloys. On the Boeing 757, the supersonic SR-71 Blackbird, the F-22 jet fighter, space satellites and missiles, titanium parts play an extremely critical role. For example, the fan discs and engine blades in the aircraft are all made of titanium castings and forgings.
The second application area of titanium is related to the use of its corrosion resistance. Among them, the largest amount is used as electrode material for Chlor-alkali production. The service life of titanium anodes is 10 times that of graphite anodes, which doubles the production capacity and saves electricity by 15%. With an annual output of 10,000 tons of caustic soda, about 5 tons of titanium are required.
In shipbuilding in the maritime industry, titanium had its past glory. Each of the 6 to 7 3000-ton nuclear submarines manufactured by the former Soviet Union uses up to 560 tons of titanium (the Alpha-class submarine uses more than 908 tons of titanium). In recent years, titanium has shown great power in offshore oil and gas exploration and development. During the period from 1997 to 1999 alone, Europe invested 15 billion US dollars in the North Sea oil and gas development for the construction of 21 suspended production vessels and 64 platforms. . The life safety system of a new platform requires 50 to 500 tons of titanium, the wedge stress joint requires 50 to 100 tons of titanium, the retractable lifter requires 400 to 1,200 tons of titanium, and the fixed lifter requires 1,400 to 4200 tons of titanium.
In the energy industry, it is known to use titanium as the condenser and heat exchanger of the power generation device. For example, the generator sets of Taizhou Power Plant, Shanghai Jinshan Thermal Power Plant, and Zhenhai Power Plant all use titanium tube condensers, and the amount of titanium used is about 700 tons. Both Qinshan and Daya Bay nuclear power plants have selected all-titanium condensers. In recent years, in the field of geothermal wells and geothermal development, titanium has also shown great demeanor, fully demonstrating its anti-corrosion ability. It is used as a power steam turbine in the high temperature and corrosive environment of geothermal brine. Other materials have to be replaced by titanium due to their short life. The advantage of using titanium is that it can increase the productivity of heat recovery and the life of geothermal wells. Since the 1990s, the United States has drilled a geothermal well with a temperature of up to 300°C in the Salton Sea area of Southern California, and 227 tons of Ti-6Al-4V-0.1Ru alloy hot-rolled seamless pipes have been used. It is estimated that the amount of titanium used in geothermal development around the world may reach 2,400 tons in the next ten years. If titanium is used for the Yangbajing Power Station in Tibet, its appearance will be greatly improved.
Offshore oil and gas drilling and geothermal development mainly use Ti-6Al-4VELI, Ti-3Al-2.5V, Ti-6Al-4V-0.1Ru, Ti-3Al-2.5V-0.1Ru, and molybdenum-containing Ti-38644 (Ti-3Al- 8V-6Cr-4Zr-4Mo) and other alloys. The marine fastener uses Ti-5111 (Ti-5Al-1Sn-1Zr-1V-0.8Mo) alloy. In order to meet the needs of ocean engineering, our country has also developed Ti75, Ti31, and Ti631 alloys.
According to statistics, a 200,000-kilowatt thermal power generating unit uses 90 tons of titanium, and a nuclear power plant uses 80 to 100 tons of titanium. It can be seen that the amount of titanium used in energy and corrosion should not be ignored.
Golf, biomaterials, and automobile manufacturing are three very promising new application areas for titanium.
In the field of sports and leisure, the increase in the amount of golf equipment is quite dramatic. In 1993, titanium had not entered this field. In 1997, the amount of titanium used increased to 4,000 tons. The reason is that the use of titanium as a bat has high strength, light texture, and average hitting distance increased by 20-30 yards (1 yard = 0.9144 meters) or 15%. The appearance of titanium bats allowed the United States to add 448 new stadiums in 1998. The number of players reached 25 million (close to half of the world). In 1994, only 500 bats were sold. In 1995, the number increased to 190,000, but in 1997, the number soared to 1.72 million. Titanium is very useful in the field of leisure sports, such as snowboards, sleds, ice axes, crampons, and other mountain-climbing facilities.
Titanium has excellent biocompatibility, low expansion coefficient, high durability, and non-magnetic properties. It is an excellent bone support material. The weight of the implanted hip joint is about half that of stainless steel, and the bone tissue can directly adhere to the titanium implant body when it grows. Titanium alloys are also used in knee joints and denture reconstructions. According to statistics, the annual amount of titanium used in medical implants in the world is between 600-1000 tons. In addition to Ti-6Al--4VELI (ultra-low interstitial oxygen), the titanium material used has also been developed without aluminum (to avoid the toxicity to the kidney and lung) Ti metal 21SRx (Ti-2.75Nb-15.2Mo-0.34Fe-0.18Si-0.250) ), And Ti metal 21S (Ti-2.9Nb-14-9Mo-0.09Fe-2.9Al-0.22Si-0.140), Ti-6Al-7Nb and other titanium alloys.
The production of low-cost titanium and the development of titanium powder processing technology have made it possible to extend the application of titanium to the automotive industry. Springs made of titanium have begun to be used in Formula One racing cars, racing motorcycles, and the most advanced Ferrari cars. It is estimated that it will be used in engine valves, connecting rods, suspension springs, exhaust systems, and fasteners of light vehicles in the near future. It is estimated that the large-scale entry of titanium into the automotive market will start from Japan and the United States. The United States is capable of producing 16 million cars and light trucks each year, and Japan's Honda Company used titanium valves in Altezza family cars in the second half of 1998.
2. Application of Titanium Dioxide
Titanium dioxide is mainly used in coatings, plastics, papermaking, synthetic fibers, printing inks, rubber, enamel, etc., which is inferior to other white coatings. Titanium sol composed of ultrafine titanium dioxide, water, and organic solvents has become an independent new variety, which is used in cosmetics, lens surface finishing agents, inks, and coating additives, and its application fields are still expanding. The United States is the world's largest producer and consumer of titanium dioxide. The output in 1998 was 1.36 million tons, the apparent consumption was 1.13 million tons, and the output value was as high as 3 billion US dollars. my country's output and consumption are much smaller. In the United States, 50% of the consumption of titanium dioxide is for pigments, paints, and varnishes, 23% for papermaking, 23% for plastics, and 9% for other uses.
other apps
Titanium iron (TiFe) made from ilmenite concentrate is a deoxidizer and stabilizer used in the manufacture of stainless steel. Titanium iron hydrogen storage anodes and rare earth hydrogen storage materials have their own merits in the production of hydrogen storage batteries, but the cost is lower Relatively low, it will have a fight with rare earth in terms of hydrogen storage, transportation, catalysis, and fuel cells. Ti-Ni shape memory alloy is an indispensable high-tech material for medical and military industries. As for electronic ceramic functional materials, barium titanate, strontium titanate, titanium compound catalyst, and organic titanium is inert metals. Its chemical symbol is ti, its atomic number is 22, and it is silver metal. The specific gravity is 4.51, and the melting point is 1668°C. It has very rich reserves in the earth's crust. It is second only to iron, aluminum, and magnesium, ranking fourth, and more than ten times more than the sum of commonly used metals such as copper, nickel, lead, and zinc. Industrially used to produce titanium ores are rutile, ilmenite, and titanomagnetite. Due to the difficulty of separation and extraction, the industrially significant metal titanium was not produced until the 1940s. Therefore, titanium is generally called a rare light metal. Because different products in different fields require different titanium and titanium alloy products, people process them into plates, rods, tubes, ribbons, wires, and other shapes that can be deep-processed to meet the needs of different fields. Titanium plates, titanium rods, and titanium tubes are the most widely used. The following is an introduction to the performance of commonly used titanium plates in the chemical industry: 1. Titanium plate and titanium alloy plate executive standard: GB/T3621-2007
three. Mechanical properties of titanium plate
4. Surface quality
The surface of the titanium plate should be bright and clean, showing the natural color of the metal. Plates are allowed to be delivered with a sandblasted surface.
The surface of the titanium plate is allowed to have slight darkening and local watermarks; local defects, scratches, indentations, pits, and other defects that do not exceed half of the thickness tolerance are allowed, but the minimum thickness should be guaranteed.
The surface of the titanium plate is not allowed to have cracks, peeling, oxide scale, crushing, metal and non-metal inclusions, and other macro defects and traces of alkaline washing. The titanium plate is allowed to clear the local defects along the rolling direction, but the thickness of the plate after removal is not less than the minimum allowable thickness. In addition, there should be no delamination of the titanium plate.
five. Application of Titanium Plate
Titanium and titanium alloys have low density and high tensile strength. In the range of -253-600 degrees Celsius, its specific strength is almost the highest among metal materials. It can form a thin and hard oxide in a suitable oxidizing environment. The film has excellent corrosion resistance. In addition, it is non-magnetic and has a small linear expansion coefficient. This made titanium and its alloys first known as important aerospace structural materials, and then extended to shipbuilding, chemical industry, and other fields, and has been rapidly developed. Especially in the chemical industry, titanium and titanium alloy products are used in more and more products, such as petrochemical, fiber, pulp, fertilizer, electrochemistry, and seawater desalination industries, as exchangers, reaction towers, and synthesizers. Autoclave etc. Among them, the titanium plate is used as an electrolytic plate, an electrolytic cell in electrolysis and sewage desalination, and is used as a tower body and a kettle body in the reaction tower and the reaction kettle.
With the development of science and technology, the application fields of titanium materials are becoming wider and wider, such as medical treatment, automobile, sports, etc. It also truly reflects that titanium, as light metal, has more and more excellent characteristics. It is recognized and determined by people, and will replace other metals into our production and application fields, and even our bodies at the fastest speed. The applications of heat-resistant paint and titanium epoxy paint are even more numerous.
