Titanium alloys can be divided into three groups according to the ratio of the amount of b-phase (with a hexagonal crystal lattice) and b-phase (with a volume-centric cubic lattice); b-, (b + c)- and c-alloys are distinguished.
According to the influence on the temperature of polymorphic transformations, alloying elements ( Legimation (German legieren--"to fuse", from lat. ligare--"to bind")--addition to composition materials, impurities for change (improvement) physical and/or chemical properties of the base material) are divided into b-stabilizers, which increase the temperature of the polymorphic transformation, b-stabilizers, which lower it, and neutral hardeners, which have little effect on this temperature. B-stabilizers include Al, In and Ga; to β-stabilizers - eutectoid-forming (Cr, Mn, Fe, Co, Ni, Cu, Si) and isomorphic (V, Nb, Ta, Mo, W) elements, to neutral strengtheners - Zr, Hf, Sn, Ge.
Interstitial elements are harmful impurities (C, N, O), which reduce the ductility and manufacturability of metals, and H (hydrogen), which causes hydrogen embrittlement of alloys.
The formation of the structure and, consequently, the properties of titanium alloys is decisively influenced by phase transformations associated with the polymorphism of titanium. In Fig. Figure 17.1 presents diagrams of the titanium-alloying element state diagrams, reflecting the division of alloying elements into four groups according to the nature of their influence on the polymorphic transformations of titanium.
The polymorphic b ® a transformation can occur in two ways. With slow cooling and high atomic mobility, it occurs according to the usual diffusion mechanism with the formation of a polyhedral structure of a solid a-solution. During rapid cooling - according to a diffusion-free martensitic mechanism with the formation of a needle-shaped martensitic structure, designated a ў or with a higher degree of alloying - a ў ў. Crystal structure a, a ў, a ў ў are almost the same type (hcp), however, the lattice of a ў and a ў ў is more distorted, and the degree of distortion increases with increasing concentration of alloying elements. There is evidence [1] that the lattice of the a ў ў phase is more orthorhombic than hexagonal. During aging, the b-phase or intermetallic phase is released from the a ў and a ў ў phases.
Picture 1
Annealing carried out for all titanium alloys in order to complete the formation of the structure, level out structural and concentration heterogeneity, as well as mechanical properties. The annealing temperature should be higher than the recrysallization temperature, but lower than the transition temperature to the b-state ( T pp) to avoid grain growth. Apply normal annealing, double or isothermal(to stabilize the structure and properties), incomplete(to relieve internal stress).
Hardening and aging (hardening heat treatment) is applicable to titanium alloys with (a + b) structure. The principle of strengthening heat treatment is to obtain metastable phases b, a ў, a ў ў during hardening and their subsequent decomposition with the release of dispersed particles of a - and b - phases during artificial aging. In this case, the strengthening effect depends on the type, quantity and composition of metastable phases, as well as the dispersity of the a- and b-phase particles formed after aging.
Chemical-thermal treatment carried out to increase hardness and wear resistance, resistance to “seizing” when working under friction conditions, fatigue strength, as well as improve corrosion resistance, heat resistance and heat resistance. Nitriding, siliconizing and some types of diffusion metallization have practical applications.
b-alloys
Alloys with b-structure: VT1-0, VT1-00, VT5, VT5-1, OT4, OT4-0, OT4-1. They are alloyed with Al, Sn and Zr. They are characterized by increased heat resistance, high thermal stability, low tendency to cold brittleness, and good weldability. The main type of heat treatment is annealing at 590-740 °C. Used for the manufacture of parts operating at temperatures up to 400-450 °C; high purity Ti alloy (5% Al and 2.5% Sn) is one of the best materials for operation at cryogenic temperatures (up to 20 K).
VT1-0:
VT1-0 is a b-alloy that is saturated with stabilizers to increase the temperature of the polymorphic transformation of titanium:
At a temperature of 882.5 degrees Celsius, the structure of the alloy is hcp (hexagonal close-packed), that is, with the most dense packing of balls of atoms. In the temperature range from 882.5 degrees Celsius to the melting point, a bcc structure occurs, that is, a body-centered lattice.
Titanium VT1-0 is high-purity, lightweight, heat-resistant. Melting occurs at a temperature of 1668°C. The alloy is characterized by a low thermal expansion coefficient. It is low-density (density is only 4.505 g/cm3) and highly plastic (ductility can range from 20 to 80%). These qualities make it possible to obtain parts of any desired shape from the described alloy. The alloy is resistant to corrosion due to the presence of an oxide protective film on its surface.
Among the disadvantages is the need for high labor costs in its production. Melting of titanium occurs only in a vacuum or inert gas environment. This is due to the active interaction of liquid titanium with almost all atmospheric gases. In addition, the VT1-0 alloy is difficult to cut, although its strength is not so high compared to others. The less aluminum an alloy contains, the lower its strength and heat resistance, and the higher its hydrogen brittleness.
Thanks to its high technical specifications VT1-0 alloy is ideal for the manufacture of pipes, various stampings and cast elements in the rocket, aircraft and shipbuilding, chemical and energy industries. Thanks to its low thermal coefficient expansion material combines perfectly with others (glass, stone and others), which makes it effective in construction industry. The metal is non-magnetic and has high electrical resistance, which makes it different from many other metals. Due to these qualities, it is simply irreplaceable in such fields as radio electronics and electrical engineering. Biologically inert, that is, harmless to the human body, due to which it is used in many fields of medicine.
OT-4-0:
The OT4-0 alloy is included in the category of pseudo b-alloys. These alloys are not subject to thermal hardening and are classified as follows:
In percentage terms, their composition is as follows:
It is characterized by a medium degree of strength, which is increased by the addition of aluminum. The disadvantage is that this reduces the manufacturability of the material. Alloying with manganese helps improve the processability of the material under conditions hot processing pressure. In both hot and cold states, the alloy is easily subject to deformation. Stamping is possible even at room temperature; steel is easily welded. Significant disadvantages of this alloy include its low strength, as well as a predisposition to brittleness under conditions aggressive influence hydrogen.
The alloy is used to manufacture high-tech parts intended for cold stamping. Many types of rolled metal are made from it: pipes, wires, sheets and others. The high performance properties of the alloy, including resistance to corrosion and erosion, ballistic resistance, make it effective in the design of nuclear power plants, heat exchangers and pipelines, chimneys on ships, pumps and other similar structural elements. OT4-0 pipe is actively used in the nuclear energy and chemical industries.
(b+c)-alloys
Alloys with (b+c) structure: alloys VT14, VT9, VT8, VT6, VT6S, VT3-1, VT22, VT23. Due to the more ductile beta phase, these alloys are more technologically advanced and better workable under pressure than alpha alloys.
(a + b) structures are doped with A1, V, Zr, Cr, Fe, Mo, Si, W; in the annealed state they contain 5-50% b-phase. They are distinguished by the most favorable combination of mechanical and technological properties, high strength, and thermal properties. strengthening as a result of hardening and aging, satisfactory weldability, less tendency to hydrogen embrittlement compared to b-alloys. The strength properties of industrial (b + c) alloys in the annealed state increase with increasing content of b-stabilizers in them. Increasing the Al content in alloys increases their heat resistance, reduces ductility and manufacturability during pressure treatment.
VT3-1:
The alloy based on titanium grade VT3-1 belongs to the category of b + c-alloys. It is doped with the following elements:
Rolled metal VT3-1 is resistant to corrosion and chemical attack. It is characterized by such qualities as increased heat resistance, low thermal expansion coefficient, as well as lightness and ductility. The ability of a material to resist fatigue is influenced by external factors. Thus, in a vacuum environment the alloy is more durable than when exposed to air. Its surface, that is, the state in which it is located and its quality, also significantly affects its endurance. Is it rough, does it have irregularities, what properties do the surface layers have? The endurance of titanium semi-finished products depends on these factors.
Soft final mechanical processing contributes to increasing the endurance limit. This means the mandatory removal of a layer of thin shavings up to 0.1 mm thick, and then polishing by hand using copper sandpaper, the roughness of which is within class 8-9. If grinding with abrasives and forced cutting were carried out, then such an alloy will have poor fatigue resistance.
There are certain requirements for rolled titanium metal of this grade. So, it should be a light, pure color, and there should be no darkening or streaks on its surface. The waviness that appears after annealing is not defective. Among the disadvantages of the VT3-1 alloy are the need for large labor costs in its production and high cost. Such metals respond better to compression than to tension.
Rolled metal products VT3-1, including wire, rod, circle and others, due to their suitability for extreme conditions Used in shipbuilding, aircraft and rocketry. Due to its resistance to corrosion and the negative effects of acidic environments, the alloy is widely used in the chemical and oil and gas industries. Biological inertness, that is, safety for the body, ensures its active use in the food, agricultural and medical fields.
VT-6 has the following characteristics:
A wide range of rolled metal products are made from the alloy of the described brand: rod, pipe, stamping, plate, sheet and many other varieties.
They are welded using a number of traditional methods, including diffusion. As a result of using electron beam welding, the strength of the weld is comparable to the base material.
VT6 grade titanium is equally widely used both annealed and heat-treated, which means it is of higher quality.
Annealing of sheets, thin-walled pipes, profiles is carried out in the temperature range from 750 to 800 degrees Celsius. It is cooled either in the open air or in an oven.
Large rolled metal products such as rods, stampings, and forgings are annealed in the temperature range from 760 to 800 degrees Celsius. It is cooled in an oven, which protects large products from deformation, and small ones from partial hardening.
There is a theory that it is more rational to anneal in the temperature range from 900 to 950°C. This will increase fracture toughness, impact strength and, thanks to the mixed composition with a large percentage of the plastic component, will maintain the plasticity of the product. Also, this annealing method will increase the alloy’s resistance to corrosion.
It is used in production (for welding) large structures, for example, such as structural elements of aircraft. It is also the creation of cylinders capable of withstanding increased pressure inside them in the temperature range of -196 - 450 C. According to Western media, approximately half of all titanium used in the aviation industry is VT-6 titanium.
v-alloys
Alloys with b-structure. Some experienced VT15, TC6 with a high content of chromium and molybdenum. These alloys combine good technological ductility with very high strength and good weldability.
Semi-finished products from titanium and titanium alloys are produced in all possible forms and types: titanium ingots, titanium slabs, billets, titanium sheets and titanium plates, titanium strips and strips, titanium rods (or titanium circles), titanium wire, titanium pipes.
This group includes alloys whose structure is dominated by a solid solution based on the β-modification of titanium. The main alloying elements are β-stabilizers (elements that lower the temperature of the polymorphic transformation of titanium). β-alloys almost always include aluminum, which strengthens them.
Thanks to the cubic lattice, c-alloys are lighter than b- and (b+c) alloys, are subject to cold deformation, are well strengthened during heat treatment, which consists of hardening and aging, and are weldable satisfactorily; They have a fairly high heat resistance, however, when alloying them only with β-stabilizers, the heat resistance noticeably decreases with increasing temperature above 400°C. The creep resistance and thermal stability of alloys of this type are lower than those of a-solid solution alloys.
After aging, the strength of β-alloys can reach 1700 MPa (depending on the grade of the alloy and the type of semi-finished product). Despite the favorable combination of strength and plastic characteristics, b-alloys have a limited scope due to high cost and complexity production process, as well as the need for strict adherence to technological parameters.
The range of applications for β-alloys is still quite wide - from aircraft engine discs to various prosthetics for medical purposes. In industrial production conditions, it is possible to predict properties based on the microstructure of large-sized stampings. However, due to its complexity, difficulties may arise during ultrasound control.
The PerfectMetal company purchases titanium scrap, along with other metals. Any scrap metal collection points of the company will accept titanium, products made of titanium alloys, titanium shavings, etc. Where does titanium get to scrap yards? Everything is very simple, this metal has found very wide application both for industrial purposes and in human life. Today this metal is used in the construction of space and military rockets, and it is also used a lot in aircraft construction. Titanium is used to build strong and lightweight sea vessels. Chemical industry, jewelry, not to mention the very wide use of titanium in the medical industry. And all this is due to the fact that titanium and its alloys have a number of unique properties.
The earth's crust, as is known, is saturated with numerous chemical elements. A common one among them is titanium. We can say that it is in 10th place in the TOP of the most common chemical elements on Earth. Titanium is a silver-white metal, resistant to many aggressive environments, not susceptible to oxidation in a number of powerful acids, the only exceptions being hydrofluoric acid and phosphoric acid. sulfuric acid in high concentration. Titan in pure form relatively young, it was received only in 1925.
The oxide film that covers titanium in its pure form serves as a very reliable protection of this metal from corrosion. Titanium is also valued for its low thermal conductivity; for comparison, titanium conducts heat 13 times worse than aluminum, but with the conductivity of electricity the opposite is true - titanium has much greater resistance. Still the most important distinguishing feature titanium - its colossal strength. Again, if we compare it now with pure iron, then titanium is twice as strong as it is!
Titanium alloys also have outstanding properties, among which, as you might have guessed, strength comes first. As a structural material, titanium is second only to beryllium alloys in strength. However an undeniable advantage Titanium alloys are characterized by their high resistance to abrasion, wear and at the same time sufficient ductility.
Titanium alloys are resistant to a number of active acids, salts, and hydroxides. These alloys are not afraid of high-temperature influences, which is why jet engine turbines are made from titanium and its alloys, and in general are widely used in rocketry and the aviation industry.
Titanium is used where a very strong material is needed that has maximum resistance to various types negative impact. For example, in the chemical industry, titanium alloys are used to produce pumps, tanks and pipelines for transporting aggressive liquids. In medicine, titanium is used for prosthetics and has excellent biological compatibility with the human body. In addition, an alloy of titanium and nickel - nitinol - has a “memory”, which allows it to be used in orthopedic surgery. In metallurgy, titanium serves as an alloying element, which is added to some types of steel.
Due to the preservation of ductility and strength under the influence of low temperatures, the metal is used in cryogenic technology. In aircraft and rocket engineering, titanium is valued for its heat resistance, and its alloy with aluminum and vanadium is most widely used here: it is from it that parts for aircraft bodies and jet engines are made.
In turn, in shipbuilding, titanium alloys are used to manufacture metal products with increased corrosion resistance. But, in addition to industrial use, titanium serves as a raw material for the creation of jewelry and accessories, as it lends itself well to processing methods such as polishing or anodizing. In particular, housings are cast from it wristwatch and jewelry.
Titanium is widely used in the composition various connections. For example, titanium dioxide is part of paints, used in the production of paper and plastic, and titanium nitride acts as protective coating tools. Despite the fact that titanium is called the metal of the future, at this stage its scope of application is seriously limited high cost receiving.
Table 1
| Chemical composition of industrial titanium alloys. | ||||||||
| Alloy type | Alloy grade | Chemical composition, % (rest Ti) | ||||||
| Al | V | Mo | Mn | Cr | Si | Other elements | ||
| a | VT5 VT5-1 |
4,3-6,2 4,5-6,0 |
— — |
— — |
— — |
— — |
— — |
— 2-3Sn |
| Pseudo-a | OT4-0 OT4-1 OT4 VT20 VT18 |
0,2-1,4 1,0-2,5 3,5-5,0 6,0-7,5 7,2-8,2 |
— — — 0,8-1,8 — |
— — — 0,5-2,0 0,2-1,0 |
0,2-1,3 0,7-2,0 0,8-2,0 — — |
— — — — — |
— — — — 0,18-0,5 |
— — — 1.5-2.5Zr 0.5-1.5Nb 10-12Zr |
| a+b | VT6S VT6 VT8 VT9 VT3-1 VT14 VT16 VT22 |
5,0-6,5 5,5-7,0 6,0-7,3 5,8-7,0 5,5-7,0 4,5-6,3 1,6-3,0 4,0-5,7 |
3,5-4,5 4,2-6,0 — — — 0,9-1,9 4,0-5,0 4,0-5,5 |
— — 2,8-3,8 2,8-3,8 2,0-3,0 2,5-3,8 4,5-5,5 4,5-5,0 |
— — — — — — — — |
— — — — 1,0-2,5 — — 0,5-2,0 |
— — 0,20-0,40 0,20-0,36 0,15-0,40 — — — |
— — — 0.8-2.5Zr 0.2-0.7Fe — — 0.5-1.5Fe |
| b | VT15 | 2,3-3,6 | — | 6,8-8,0 | — | 9,5-11,0 | — | 1.0Zr |
Everything you need to know about titanium, plus chromium and tungsten
Many people are interested in the question: what is the hardest metal in the world? This is titanium. This solid and will be the focus of the article. Let's also get acquainted a little with such hard metals as chromium and tungsten.
9 interesting facts about titanium
1. There are several versions of why the metal got its name. One theory is that he was named after the Titans, fearless supernatural creatures. According to another version, the name comes from Titania, the queen of fairies.
2. Titanium was discovered at the end of the 18th century by a German and English chemist.
3. Titanium has not been used in industry for a long time due to its natural fragility.
4. At the beginning of 1925, after a series of experiments, chemists obtained titanium in its pure form.
5. Titanium shavings are highly flammable.
6. It is one of the lightest metals.
7. Titanium can only melt at temperatures above 3200 degrees.
8. Boils at a temperature of 3300 degrees.
9. Titanium has a silver color.
History of the discovery of titanium
The metal, which was later named titanium, was discovered by two scientists - the Englishman William Gregor and the German Martin Gregor Klaproth. The scientists worked in parallel and did not intersect with each other. The difference between discoveries is 6 years.
William Gregor gave his discovery a name: manakin.
More than 30 years later, the first titanium alloy was obtained, which turned out to be extremely brittle and could not be used anywhere. It is believed that only in 1925 titanium was isolated in its pure form, which became one of the most popular metals in industry.
It has been proven that the Russian scientist Kirillov managed to extract pure titanium in 1875. He published a brochure detailing his work. However, the research of a little-known Russian went unnoticed.
General information about titanium
Titanium alloys are a salvation for mechanics and engineers. For example, the body of an airplane is made of titanium. During flight, it reaches speeds several times greater than the speed of sound. The titanium case heats up to temperatures above 300 degrees and does not melt.
The metal closes the top ten of “The most common metals in nature.” Large deposits have been discovered in South Africa, China and a lot of titanium in Japan, India, and Ukraine.
The total world reserve of titans amounts to more than 700 million tons. If production rates remain the same, there will be enough titanium for another 150-160 years.
The largest producer of the hardest metal in the world is the Russian enterprise VSMPO-Avisma, which satisfies a third of the world's needs.
Properties of titanium
1. Corrosion resistance.
2. High mechanical strength.
3. Low density.
The atomic weight of titanium is 47.88 amu, the serial number in the chemical periodic table is 22. Outwardly, it is very similar to steel.
The mechanical density of the metal is 6 times greater than that of aluminum, 2 times higher than that of iron. It can combine with oxygen, hydrogen, nitrogen. When paired with carbon, the metal forms incredibly hard carbides.
The thermal conductivity of titanium is 4 times less than that of iron, and 13 times less than that of aluminum.
Titanium mining process
There is a large amount of titanium in the earth, however, extracting it from the depths costs a lot of money. For production, the iodide method is used, the author of which is considered to be Van Arkel de Boer.
The method is based on the ability of the metal to combine with iodine; after decomposition of this compound, pure titanium, free of foreign impurities, can be obtained.
The most interesting things made of titanium:
Areas of application of titanium
Titanium is actively used in the military sphere, medicine, and jewelry. It was given the unofficial name “metal of the future.” Many say that it helps turn dreams into reality.
The hardest metal in the world was initially used in the military and defense sphere. Today, the main consumer of titanium products is the aircraft industry.
Titanium is a universal construction material. For many years it was used to create aircraft turbines. In aircraft engines, fan elements, compressors, and disks are made from titanium.
The design of a modern aircraft can contain up to 20 tons of titanium alloy.
The main areas of application of titanium in aircraft construction:
Thanks to titanium, man was able to pass through the sound barrier and break into space. It was used to create manned missile systems. Titan can withstand cosmic radiation, temperature changes, and movement speed.
This metal has a low density, which is important in the shipbuilding industry. Products made of titanium are lightweight, which means the weight is reduced and its maneuverability, speed, and range are increased. If the hull of a ship is sheathed with titanium, it will not need to be painted for many years - titanium does not rust sea water(corrosion resistance).
Most often, this metal is used in shipbuilding for the manufacture of turbine engines, steam boilers, and condenser pipes.
Oil industry and titanium
Ultra-deep drilling is considered a promising area for the use of titanium alloys. To study and extract underground resources, it is necessary to penetrate deep underground - over 15 thousand meters. Aluminum drill pipes, for example, will rupture due to their own gravity, and only titanium alloys can reach truly great depths.
Not so long ago, titanium began to be actively used to create wells on the sea shelves. Specialists use titanium alloys as equipment:
Titanium in sports, medicine
Titanium is extremely popular in the sports field due to its strength and lightness. Several decades ago, a bicycle was made from titanium alloys, the first sports equipment made from the hardest material in the world. A modern bicycle consists of a titanium body, the same brake and seat springs.
Titanium golf clubs have been created in Japan. These devices are lightweight and durable, but extremely expensive.
Most of the items that are in the backpack of climbers and travelers are made from titanium - tableware, cooking sets, racks for strengthening tents. Titanium ice axes are very popular sports equipment.
This metal is in great demand in the medical industry. Most surgical instruments are made from titanium - lightweight and convenient.
Another area of application of metal of the future is the creation of prosthetics. Titanium “combines” perfectly with the human body. Doctors called this process “real kinship.” Titanium structures are safe for muscles and bones and rarely cause allergic reaction, are not destroyed by fluid in the body. Titanium prostheses are durable and can withstand enormous physical loads.
Titanium is an amazing metal. It helps a person achieve unprecedented heights in various areas of life. It is loved and revered for its strength, lightness and long years of service.
Chromium is one of the hardest metals.
Interesting facts about chromium
1. The name of the metal comes from the Greek word “chroma”, which means paint.
2. In the natural environment, chromium is not found in its pure form, but only in the form of chromium iron ore, double oxide.
3. The largest deposits of the metal are located in South Africa, Russia, Kazakhstan and Zimbabwe.
4. Metal density – 7200 kg/m3.
5. Chrome melts at a temperature of 1907 degrees.
6. Boils at a temperature of 2671 degrees.
7. Absolutely pure chromium without impurities is characterized by ductility and viscosity. When combined with oxygen, nitrogen or hydrogen, the metal becomes brittle and very hard.
8. This silvery-white metal was discovered by the Frenchman Louis Nicolas Vauquelin at the end of the 18th century.
Properties of chromium metal
Chromium has very high hardness and can cut glass. It is not oxidized by air or moisture. If the metal is heated, oxidation will occur only on the surface.
More than 15,000 tons of pure chromium are consumed per year. The English company Bell Metals is considered the leader in the production of pure chromium.
The United States consumes the most chromium. Western countries Europe and Japan. The chrome market is volatile and prices span a wide range.
Areas of use of chromium
Most often used to create alloys and galvanic coatings(chrome plating for transport).
Chromium is added to steel, which improves physical properties metal These alloys are most in demand in ferrous metallurgy.
The most popular grade of steel consists of chromium (18%) and nickel (8%). Such alloys perfectly resist oxidation, corrosion, and are durable even at high temperatures Oh.
Heating furnaces are made from steel, which contains a third of chromium.
What else is made from chromium?
1. Firearm barrels.
2. Submarine hull.
3. Bricks, which are used in metallurgy.
Another extremely hard metal is tungsten.
Interesting facts about tungsten
1. The name of the metal translated from German (“Wolf Rahm”) means “wolf foam.”
2. It is the most refractory metal in the world.
3. Tungsten has a light gray tint.
4. The metal was discovered at the end of the 18th century (1781) by the Swede Karl Scheele.
5. Tungsten melts at a temperature of 3422 degrees, boils at 5900.
6. Metal has a density of 19.3 g/cm³.
7. Atomic mass– 183.85, element of group VI c periodic table Mendeleev (serial number – 74).
Tungsten Mining Process
Tungsten belongs to a large group of rare metals. It also includes rubidium and molybdenum. This group is characterized by a low prevalence of metals in nature and a small scale of consumption.
The production of tungsten consists of 3 stages:
Applications of tungsten
Tungsten is the basis of most strong alloys. It is used to make aircraft engines, parts of electric vacuum devices, and incandescent filaments.
The high density of the metal makes it possible to use tungsten to create ballistic missiles, bullets, counterweights, and artillery shells.
Tungsten-based compounds are used for processing other metals, in the mining industry (well drilling), paint and varnish, and textiles (as a catalyst for organic synthesis).
From complex tungsten compounds they make:
Titanium, chromium and tungsten top the list of "The Hardest Metals in the World." They are used in many areas of human activity - aviation and rocketry, military, construction, and at the same time, this is not the full range of applications of metals.
Titanium ranks 4th in terms of distribution in production, but effective technology for its extraction was developed only in the 40s of the last century. It is a silver-colored metal characterized by a low specific gravity and unique characteristics. To analyze the extent of distribution in industry and other areas, it is necessary to announce the properties of titanium and the areas of application of its alloys.
The metal has a low specific gravity - only 4.5 g/cm³. Anti-corrosion qualities are due to the stable oxide film formed on the surface. Thanks to this quality, titanium does not change its properties when kept in water or hydrochloric acid for a long time. There are no damaged areas due to stress, which is a major problem with steel.
In its pure form, titanium has the following qualities and characteristics:
For comparison, the strength of this material is 2 times greater than that of pure iron and 4 times that of aluminum. Titanium also has two polymorphic phases - low temperature and high temperature.
Pure titanium is not used for production needs due to its high cost and required performance qualities. To increase rigidity, oxides, hybrids and nitrides are added to the composition. It is less common to change material characteristics to improve corrosion resistance. The main types of additives for producing alloys: steel, nickel, aluminum. In some cases, it functions as an additional component.
Due to its low specific gravity and strength parameters, titanium is widely used in the aviation and space industries. It is used as the main structural material in its pure form. IN special cases By reducing the heat resistance, cheaper alloys are made. At the same time, its corrosion resistance and mechanical strength remain unchanged.
In addition, material with titanium additives has found application in the following areas:
In most cases, the material is processed in a factory. But there are a number of exceptions - knowing the properties of this material, some of the work to change the appearance of the product and its characteristics can be done in a home workshop.
To give the product the desired shape, it is necessary to use special equipment - lathe and milling machine. Hand cutting or milling of titanium is not possible due to its hardness. In addition to choosing the power and other characteristics of the equipment, it is necessary to select the right cutting tools: cutters, cutters, reamers, drills, etc.
The following nuances are taken into account:
Titanium is a unique material with good performance and technical qualities. But to process it, you need to know the specifics of the technology, and most importantly, safety precautions.
Titanium in the form of oxide (IV) was discovered by the English amateur mineralogist W. Gregor in 1791 in the magnetic ferruginous sands of the town of Menacan (England); in 1795, the German chemist M. G. Klaproth established that the mineral rutile is a natural oxide of the same metal, which he called “titanium” [in Greek mythology, the titans are the children of Uranus (Heaven) and Gaia (Earth)]. It was not possible for a long time to isolate Titanium in its pure form; only in 1910, the American scientist M.A. Hunter obtained the metal Titan by heating its chloride with sodium in a sealed steel bomb; the metal he obtained was ductile only at elevated temperatures and brittle at room temperature due to the high content of impurities. The opportunity to study the properties of pure Titanium appeared only in 1925, when the Dutch scientists A. Van Arkel and I. de Boer obtained a high-purity metal, plastic at low temperatures, using the thermal dissociation of titanium iodide.
Distribution of Titan in nature. Titanium is one of the common elements, its average content in earth's crust(clark) is 0.57% by weight (among structural metals it ranks 4th in prevalence, behind iron, aluminum and magnesium). Most of Titan is in the basic rocks of the so-called “basalt shell” (0.9%), less in the rocks of the “granite shell” (0.23%) and even less in ultrabasic rocks (0.03%), etc. rocks, enriched in Titanium, include pegmatites of basic rocks, alkaline rocks, syenites and associated pegmatites and others. There are 67 known Titanium minerals, mostly of igneous origin; the most important are rutile and ilmenite.
Titan is mostly scattered in the biosphere. Sea water contains 10 -7% of it; Titan is a weak migrant.
Physical properties of Titan. Titanium exists in the form of two allotropic modifications: below a temperature of 882.5 °C, the α-form with a hexagonal close-packed lattice (a = 2.951 Å, c = 4.679 Å) is stable, and above this temperature - the β-form with a cubic body-centered lattice a = 3.269 Å. Impurities and alloying additives can significantly change the α/β transformation temperature.
The density of the α-form at 20°C is 4.505 g/cm 3 , and at 870°C 4.35 g/cm 3 ; β-form at 900°C 4.32 g/cm 3 ; atomic radius Ti 1.46 Å, ionic radii Ti + 0.94 Å, Ti 2+ 0.78 Å, Ti 3+ 0.69 Å, Ti 4+ 0.64 Å; Melting point 1668 °C, boiling point 3227 °C; thermal conductivity in the range 20-25°C 22.065 W/(m K); temperature coefficient of linear expansion at 20°C 8.5·10 -6, in the range 20-700°C 9.7·10 -6; heat capacity 0.523 kJ/(kg K); electrical resistivity 42.1·10 -6 ohm·cm at 20 °C; temperature coefficient of electrical resistance 0.0035 at 20 °C; has superconductivity below 0.38 K. Titanium is paramagnetic, specific magnetic susceptibility 3.2·10 -6 at 20 °C. Tensile strength 256 MN/m2 (25.6 kgf/mm2), relative elongation 72%, Brinell hardness less than 1000 MN/m2 (100 kgf/mm2). Normal elastic modulus 108,000 MN/m2 (10,800 kgf/mm2). Metal of high purity is malleable at ordinary temperatures.
Technical Titanium used in industry contains impurities of oxygen, nitrogen, iron, silicon and carbon, which increase its strength, reduce ductility and affect the temperature of the polymorphic transformation, which occurs in the range of 865-920 °C. For technical Titanium grades VT1-00 and VT1-0, the density is about 4.32 g/cm 3 , tensile strength 300-550 MN/m 2 (30-55 kgf/mm 2), elongation not lower than 25%, Brinell hardness 1150 -1650 Mn/m 2 (115-165 kgf/mm 2). The configuration of the outer electron shell of the Ti atom is 3d 2 4s 2.
Chemical properties of Titan. Pure Titanium is a chemically active transition element; in compounds it has an oxidation state of +4, less often +3 and +2. At ordinary temperatures and up to 500-550 °C it is corrosion resistant, which is explained by the presence of a thin but durable oxide film on its surface.
It reacts noticeably with atmospheric oxygen at temperatures above 600 °C to form TiO 2 . If there is insufficient lubrication, thin titanium shavings can catch fire during the process. machining. If there is a sufficient oxygen concentration in the environment and the oxide film is damaged by impact or friction, the metal may ignite when room temperature and in relatively large pieces.
The oxide film does not protect titanium in the liquid state from further interaction with oxygen (unlike, for example, aluminum), and therefore its melting and welding must be carried out in a vacuum, in a neutral gas atmosphere or submerged arc. Titanium has the ability to absorb atmospheric gases and hydrogen, forming brittle alloys unsuitable for practical use; in the presence of an activated surface, hydrogen absorption occurs already at room temperature at a low rate, which increases significantly at 400 °C and above. The solubility of hydrogen in Titan is reversible, and this gas can be removed almost completely by annealing in a vacuum. Titanium reacts with nitrogen at temperatures above 700 °C, and nitrides of the TiN type are obtained; in the form of a fine powder or wire, titanium can burn in a nitrogen atmosphere. The diffusion rate of nitrogen and oxygen in Titan is much lower than that of hydrogen. The layer resulting from interaction with these gases is characterized by increased hardness and brittleness and must be removed from the surface of titanium products by etching or mechanical treatment. Titanium interacts vigorously with dry halogens and is stable against wet halogens, since moisture plays the role of an inhibitor.
The metal is resistant to nitric acid all concentrations (with the exception of red fuming, which causes corrosion cracking of Titan, and the reaction sometimes occurs with an explosion), in weak solutions of sulfuric acid (up to 5% by weight). Hydrochloric, hydrofluoric, concentrated sulfuric, as well as hot organic acids: oxalic, formic and trichloroacetic react with Titan.
Titanium is corrosion resistant in atmospheric air, sea water and sea atmosphere, in wet chlorine, chlorine water, hot and cold chloride solutions, in various technological solutions and reagents used in chemical, oil, paper-making and other industries, as well as in hydrometallurgy. Titanium forms metal-like compounds with C, B, Se, Si, characterized by refractoriness and high hardness. TiC carbide (mp 3140 °C) is obtained by heating a mixture of TiO 2 with soot at 1900-2000 °C in a hydrogen atmosphere; TiN nitride (mp 2950 °C) - by heating Titanium powder in nitrogen at temperatures above 700 °C. Silicides TiSi 2, TiSi and borides TiB, Ti 2 B 5, TiB 2 are known. At temperatures of 400-600 °C Titanium absorbs hydrogen to form solid solutions and hydrides (TiH, TiH 2). When TiO 2 is fused with alkalis, titanic acid salts are formed: meta- and ortho-titanates (for example, Na 2 TiO 3 and Na 4 TiO 4), as well as polytitanates (for example, Na 2 Ti 2 O 5 and Na 2 Ti 3 O 7). Titanates include the most important minerals of Titan, for example, ilmenite FeTiO 3, perovskite CaTiO 3. All titanates are slightly soluble in water. Titanium (IV) oxide, titanic acids (precipitates), and titanates dissolve in sulfuric acid to form solutions containing titanyl sulfate TiOSO 4 . When diluting and heating solutions, H 2 TiO 3 is deposited as a result of hydrolysis, from which Titanium (IV) oxide is obtained. When hydrogen peroxide is added to acidic solutions containing Ti (IV) compounds, peroxide (supratitanic) acids of the composition H 4 TiO 5 and H 4 TiO 8 and their corresponding salts are formed; these compounds are colored yellow or orange-red (depending on the concentration of Titanium), which is used for the analytical determination of Titanium.
Getting Titan. The most common method for producing titanium metal is the magnesium-thermal method, that is, the reduction of Titanium tetrachloride with magnesium metal (less commonly, sodium):
TiCl 4 + 2Mg = Ti + 2MgCl 2.
In both cases feedstock Titanium oxide ores - rutile, ilmenite and others - are used. In the case of ilmenite type ores, Titanium in the form of slag is separated from the iron by smelting in electric furnaces. The slag (as well as rutile) is chlorinated in the presence of carbon to form Titanium tetrachloride, which, after purification, enters a reduction reactor with a neutral atmosphere.
Titanium in this process is obtained in sponge form and, after grinding, is melted in vacuum arc furnaces into ingots with the introduction of alloying additives, if an alloy is required. The magnesium-thermal method makes it possible to create large-scale industrial production of Titanium with a closed technological cycle, since the by-product formed during reduction - magnesium chloride - is sent for electrolysis to produce magnesium and chlorine.
In some cases, it is advantageous to use powder metallurgy methods for the production of products from Titanium and its alloys. To obtain particularly fine powders (for example, for radio electronics), reduction of Titanium (IV) oxide with calcium hydride can be used.
Application of Titan. The main advantages of Titan over other structural metals: a combination of lightness, strength and corrosion resistance. Titanium alloys in absolute, and even more so in specific strength (i.e., strength related to density) are superior to most alloys based on other metals (for example, iron or nickel) at temperatures from -250 to 550 ° C, and in terms of corrosion they comparable to alloys of noble metals. However, Titanium began to be used as an independent structural material only in the 50s of the 20th century due to the great technical difficulties of its extraction from ores and processing (which is why Titanium was conventionally classified as a rare metal). The main part of Titan is spent on the needs of aviation and rocket technology and marine shipbuilding. Alloys of Titanium with iron, known as “ferrotitanium” (20-50% Titanium), serve as an alloying additive and deoxidizing agent in the metallurgy of high-quality steels and special alloys.
Technical Titanium is used for the manufacture of containers, chemical reactors, pipelines, fittings, pumps and other products operating in aggressive environments, for example, in chemical engineering. In the hydrometallurgy of non-ferrous metals, equipment made of Titanium is used. It is used to coat steel products. The use of Titanium in many cases provides a great technical and economic effect not only due to increased service life of equipment, but also the possibility of intensifying processes (as, for example, in nickel hydrometallurgy). The biological safety of Titanium makes it an excellent material for the manufacture of equipment for Food Industry and in reconstructive surgery. In deep cold conditions, the strength of Titan increases while maintaining good ductility, which makes it possible to use it as a structural material for cryogenic technology. Titanium lends itself well to polishing, color anodizing and other surface finishing methods and therefore is used for the manufacture of various artistic products, including monumental sculpture. An example is the monument in Moscow, built in honor of the launch of the first artificial Earth satellite. Among Titanium compounds, oxides, halides, and also silicides used in high-temperature technology are of practical importance; borides and their alloys used as moderators in nuclear power plants due to their refractoriness and large neutron capture cross section. Titanium carbide, which has high hardness, is part of the tool carbide alloys used for manufacturing cutting tools and as an abrasive material.
Titanium (IV) oxide and barium titanate form the basis of titanium ceramics, and barium titanate is the most important ferroelectric.
Titanium in the body. Titanium is constantly present in the tissues of plants and animals. In terrestrial plants its concentration is about 10 -4%, in marine plants - from 1.2 10 -3 to 8 10 -2%, in the tissues of terrestrial animals - less than 2 10 -4%, in marine ones - from 2 10 -4 to 2·10 -2%. Accumulates in vertebrates mainly in horn formations, spleen, adrenal glands, thyroid gland, placenta; poorly absorbed from the gastrointestinal tract. In humans, the daily intake of Titanium from food and water is 0.85 mg; excreted in urine and feces (0.33 and 0.52 mg, respectively).
