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Product Characteristics of Titanium

Characteristics of Titanium

Introduction of Titanium
Properties of Titanium
Corrosion resistance data of Titanium
Titanium element
  • · Element symbol: Ti
  • · Atomic number: 22
  • · Atomic weight: 47.90
  • · Melting point: 1675℃
  • · Boiling point: 3260℃
  • · Specific gravity: 4.50 (20℃)
Titanium: In 1789, W. Greger of England extracted a new oxide from sand iron produced in Cornwall.
After that, in 1995, M.H. Claparrot of Germany discovered a new metal element in rutile from Hungary and named it Titanium after the god in Greek mythology.
M.A. Hunter first isolated the pure metal in 1910.
Reserves
In the past, it was considered a rare element, but it has a high presence in the earth's crust, ranking 9th with a Clark number of 0.46, followed by magnesium.
It is so widely distributed that about 0.6% of titanium oxide is usually present in the soil. A small amount of it is also contained in the igneous rock of the crust.
The main ores are rutile, titanite, pan-titanium, anatase, and perovskite.
Also, titanite is contained in iron sands.
Characteristic
A silvery-white metal, it is an industrially important metal because it is malleable and ductile when pure, can be tempered by heating and has corrosion resistance.
There are two types of crystals, α-type, and β-type, and α-type is stable at room temperature. The α-type belongs to the hexagonal system, and at 882 ° C or higher, it becomes the cubic system, the β-type. It has a hardness of 4.0 and is extremely fragile when cold, and can be made into powder or made into wire when heated.

The strength is almost the same as that of carbon steel, and the strength ratio to its own weight is about twice that of iron and about six times that of aluminum. In addition, the thermal conductivity and the thermal expansion coefficient are small, and the change in strength is small at 400°C or less. It is stable in air, but it becomes titanium oxide when highly heated in oxygen.
It reacts when heated with halogen and is less soluble in acid than iron. In seawater, it is highly corrosion resistant, following platinum. It makes a lot of metals and alloys.
Manufacturing method
It is industrially manufactured by the crawl method. The raw material is rutile containing about 94% of titanium oxide TiO2, or titanite containing about 60%. First, these are smelted to form titanium slag powder. These are sintered by adding charcoal or coke, and then titanium tetrachloride is produced in a chlorination furnace at about 900 ° C.

Titanium tetrachloride produced by TiO2 + 2C + 2CI2 → TiCI4 + 2CO contains chlorides such as iron, silicon, and vanadium as impurities, so these are purified by distillation. The purified titanium tetroxide is separated into metallic titanium by dropping it into magnesium dissolved in argon gas at 1 atmosphere.
TiCI4 + 2Mg → Ti + 2MgCI2: The reactant is heated again to evaporate impurities to form a titanium sponge, usually it produce about 1t in the first process.
The purity ranges from 99.6 to 99.85%. To purify it again, the iodine method is used.

Titanium iodide is made by reacting crude titanium metal with iodine at 250~300℃, and the steam is pyrolyzed at 1,100~1,500℃ to separate high-purity titanium and iodine. Pyrolysis is usually carried out on tungsten wire through an electric current. Titanium obtained by this method has a high purity of 99.96%, so it is called iodine method titanium.
In addition, a molten salt electrolysis method or the like may be used.
Where to use
As it has high strength, high corrosion resistance, and lightness, it is used as a structural material for aircraft and ships and is also used as a material for corrosion-resistant containers in the chemical industry.
Chemical mechanical properties
As it has high strength, high corrosion resistance, and lightness, it is used as a structural material for aircraft and ships and is also used as a material for corrosion-resistant containers in the chemical industry.
TITANIUM’S CHEMICAL & MECHANICAL PROPERTIES
Quality   Gr 1 Gr 2 Gr 4 Gr 5 Gr 7 Gr 9 Gr 11 Gr 12
Analysis % Fe max 0.20 0.30 0.50 0.40/td> 0.30 0.25 0.20 0.30
  O max 0.18 0.25 0.40 0.20 0.25 0.15 0.18 0.25
  N max 0.03 0.03 0.05 0.05 0.03 0.02 0.03 0.03
  C max 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10
  H max 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015
  Pd         0.12-0.25   0.12-0.25  
  Al       5.5-6.7   2.5-305    
  V       3.5-4.5   2.0-3.0    
  Mo               0.4-0.4
Yield strength N/mm² Rp 0.2 170-310 275-450 483-655 828- 275-450 483- 170-310 345-
Tensile Strength N/mm² Rm min 240 345 550 895 345 620 240 483
Hardness Vickers 140 170 310 330 170 250 140 170
Elongation 5 x d 24 20 15 10 20 15-17 24 18
COMPARATIVE VALUES
  Density Melting Point Thermal Expansion Thermal conductivity Electrical Resistance Elasticity Modulus
Material Kg/m³ oC Coefficient (x 10(-6)) W/(m.K) Ohm x n (x 10(-8)) MPa (x 10(-3))
Titanium 4505 1688 8.4 17 55 106.4
Iron 7900 1530 12 63 9.7 206.0
Aluminium 2700 660 23 205 2.7 69.2
Nickel 8900 1453 15 92 9.5 206.0
Copper 8900 1083 17 385 1.7 107.9
Stainless Steel 18-8 7900 1410 17 16 72 200
Brass 8400 970 18.5 100 7.5 107.9
Monel 8800 1325 14 26 48 179.5
Characteristics of Titanium

Excellent corrosion resistance, high strength, low specific gravity

As a metal element, Titanium is a transition metal with atomic number 22 located in group IV-a, 4th period on the periodic table.
It has an allotropic transformation point Tc at 882°C. The crystal structure is formed into a hexagonal crystal packed (hcp) α phase at a lower temperature side, and it becomes a body-center cubic (bcc) h phase at a higher temperature side. Table 1 shows the main physical properties of pure Titanium in comparison with other materials.
[Table 1 Comparison of physical properties of Titanium with other materials]
Sortation Titanium Steel Stainless steel (304) Copper Aluminum
Density
(g/cm)		 4.5 7.9 8.0 8.9 2.7
Melting point
(℃)		 1668 1530 1400~1427 1083 660
Linear expansion
coefficient
(L/℃)		 8.4x10(-6) 12x10(-6) 17x10(-6) 17x10(-6) 23x10(-6)
Specific heat
(cal/g/℃)		 0.12 0.11 0.12 0.09 0.21
Thermal conductivity
(cal/sec °C)		 0.041 0.15 0.039 0.92 0.49
Thermal diffusion
coefficient
(cm2/sec)		 0.07 0.17 0.04 0.78 0.86
Resistivity
(μΩ-cm)		 47~55 9.7 72 1.7 2.7
Young’s modulus
(GPa)		 106 192 199 119.0 69
The characteristics of pure Titanium are that it has a high melting point, the specific gravity is middle of iron and aluminum, and the coefficients of thermal expansion and Young's modulus are smaller than those of steel. In addition, since corrosion resistance is excellent as a chemical property, efforts to develop new alloys based on Titanium as a lightweight structural material are continuing diligently.

When the alloy element is added to Titanium, the α/β transformation temperature changes depending on the type of element, and the width of the transformation temperature changes, resulting in an α+β abnormal region. Among them, an alloying element that increases the transformation point to expand the α-phase region on the equilibrium drawing is called an α-phase stabilizing element. Conversely, one that lowers the transformation point and expands the β-phase region is called a neutral stabilizing element. And one that does not belong to either is called a neutral element.

AI, C, O, N, etc., is known as α-phase stabilizing elements. As β-phase stabilizing elements, Mo, Nb, Ta V, which completely solid dissolve, and Ag, Co, Cr, Cu, Fe, Mn, Ni, Pb, Si, W, and the like, which cause a eutectoid reaction, are known. And as neutral elements, it is known Zr, Sn, etc. In addition, various alloys are being developed by combining these additive elements, which are roughly classified into α-titan alloys, α+β-titan alloys, and β-titan alloys depending on the type of constituent phase at room temperature.
Industrial pure titanium and α-titanium alloy
  • · Industrial pure titanium
    Pure Titanium is a hexagonal close-packed type(α) at room temperature. Still, its axial ratio (c/a=1.587) is smaller than other hexagonal close-packed structure metals (e.g., cla=1.623), so it has rich workability. The solid solubility of various elements in Titanium is generally high, but as impurities, the ones that have the strongest influence on the mechanical properties of pure Titanium are N, O, and Fe. Therefore, even in the Japanese Industrial Standard (JIS H 4600), the types of pure titanium plates for industrial use are classified according to the content of these impurities (mainly O and Fe).

    In addition, the tensile strength of pure Titanium containing 0.06% of O is about 3.5kgf/㎣, but the strength also increases with the increase of O, and when O becomes 0.3%, the tensile strength is about twice the value.

    α-titan is an hcp structure, and slips and twins are involved in plastic changes. With this limited number of sliding systems, the titanium polycrystalline material cannot be deformed by maintaining continuity at the crystal grain boundary (condition of von Mises). Still, the occurrence of the twin deformation compensates for it. However, their plastic behavior is influenced by impurities, alloy structure, and temperatures, causing changes in processing hardening, ductility, deformability, or the formation of collective texture, as described later.

    Since pure Titanium has a bcc structure below the transformation point (Tc - 882 ° C), it is easily deformed, but it becomes chemically active because of the high temperature, and a non-protective oxide film grows.
    The foremost characteristic of pure Titanium is that it has excellent corrosion resistance. The fact that pure Titanium occupied most of Japan's titanium demand in the past was an inevitable result of the backwardness of the aircraft industry.

    These days, when water pollution is underway in condensers for power plants and ships, the use of thin-welded titanium tubes with a thickness of 0.3 to 1 mm is expanding, replacing aluminum brass or Cupro-Nickel. In addition, pure Titanium has also begun to be used in heat transfer pipes of seawater desalination equipment and plate-type heat exchangers that cool industrial water with seawater.

    Moreover, in soda electrolysis, pure Titanium is advancing even to the exclusive distributors in the anode substrate or copper electrolytic refining. Another characteristic of Titanium is that it is light but strong.
    A comparison of strength between industrial purity titanium and stainless steel, which are widely used as corrosion-resistant materials, is shown as a temperature change in the strength/density ratio. As seen from this, the titanium side is much better in specific strength at a lower temperature than 400°C.
  • · α-titanium alloy
    ① Interstitial α alloy
    Oxygen, nitrogen, and carbon are interstitially dissolved against Titanium to expand the α-phase region.
    The O. N. C. elements have a strong influence on the mechanical properties of Titanium.
    Pure Titanium of industrial purity has the strength suitable for the purpose of use by controlling the content of O, N, and C elements.
    In summary of the effects of various impurities, Brinell hardness is said to be given the following equation.
    H8=411O%+128Fe%+675N%+380C c%+ 65.6

    The relationship between various mechanical properties (yield strength, tensile strength, elongation, and Vickers hardness) of industrial pure titanium plates in Japan and the amount of impurities contained has been obtained by the Titanium Association Technical Committee.
    On the other hand, although it is not an α-phase stabilization element, it is also important to note the bromination of Titanium by hydrogen.
    For example, the impact value significantly decreases as hydrogen is absorbed.
    It is because hydrides are precipitated, and as a countermeasure against this, it is said that forming an oxide film of TiO2 on the titanium surface is effective.

    ② Substitutable α alloy
    Among the elements dissolved solidly in the substitution type, AI is the only α-phase stabilization element, and any solid dissolution enhancement is recognized due to the influence of the solid dissolution element in the α-phase region, but the effect of AI is particularly remarkable.
    Therefore, practical α alloys are being developed based on Ti-AI. The addition of AI expands the α-phase region and increases the room temperature strength.
    However, when the amount of AI is about 7wt% or more, Ti3Al (α 2 phases) appears upon the rule of DO19 type hcp, and the toughness deteriorates.

    To avoid this, in practical alloys, Sn and Zr, β-phase stabilizing elements and neutral elements are added more to contain AI as much as possible so that Ti-AI does not occur.

    A typical α-titanium alloy developed in this way is the Ti-5AI-2.5Sn alloy, which has excellent high-temperature creep characteristics.
    From the standpoint of oxidation resistance and structural stability at high temperatures, when a titanium alloy is used as a high-temperature material, an α titanium alloy based on Ti-AI is advantageous. Still, recently, more excessive heat resistance has been required.

    For this reason, an attempt is being made to develop a "near a alloy" that combines high strength exhibited by an α+β alloy and high-temperature characteristics exhibited by a simple α alloy by adding 1 to 2wt% of a β-phase stabilizing element.
    For examples, there are Ti-11Sn-2, 25AI-5Zr-1Mo-0.25Si (IMI679), Ti-6AI-2Sn-4Zr-2Mo-0.1Si (Ti-6242), Ti-6AI-5Zr-0.5Mo-0.3Si (IMI685), Ti-5,5AI-3.5Sn-3Zr-1N-0.3Si (IMI-829), etc. In addition, the α alloy has excellent ductility along with higher strength at low-temperature compared to the β or α+β alloy.

    ELI of Ti-5AI-2.5Sn ELI stands for Extra Low Interstitial, meaning an alloy in which elements such as O, Fe, C, and the like are suppressed to a very low level.
    The effect of the O amount on the tensile properties of the Ti-5AI-2.5Sn alloy is shown, and when the amount of O is 0.12% or less, it has excellent ductility and toughness even at -253°C.
    This ELI alloy exhibits high strength and excellent ductility even at a liquid He temperature (-269°C). Thus, it is considered to be used in magnetic levitation trains and superconducting generators.

    As described above, α titanium has an hcp structure, and slip and twin deformation are involved in plastic deformation. The deformation behavior of hcp metal is strongly influenced by the axial ratio c/a of the hcp crystal, impurities contained, and alloying elements.
Corrosion Resistance Data of Titanium
Corrosion resistance data
Sortation Sortation Medium of corrosion Composition Temperature Corrosion resistance Composition Temperature Corrosion resistance
(%) (ºC) Pure titanium Pure zirconium SUS304 SUS316 HASTELLOY-C
Inorganic acid Hydrochloric acid (HCI) 1 25 A A B A A
  Boiling D A D D C
10 25 B A D D C
  Boiling D A D D D
Sulfuric acid (H2 SO 4) 1 25 A A A A A
  Boiling D A D C B
10 25 B A B B A
  Boiling D A D D B
Nitric acid (HNO3) 10 25 A A A A A
  Boiling A A A A B
65 25 A A A A B
  Boiling A A B B D
Organic acid Acetic acid (CH3 COOH) 10 Boiling A A A A A
60 Boiling A A B B A
Oxalic acid ((COOH)2) 10 25 A A C B A
30 Boiling D A D D A
Formic acid (HCOOH) 10 25 B A B B B
30 Boiling D A C B B
Lactic acid (CH3 CH(OH)COOH) 10 25 A A B B B
30 Boiling A A D D B
Alkali Caustic soda (Na OH) 10 100 A A A A A
40 Boiling D B B B B
Potassium carbonate (K2 CO 3 ) 5 Boiling A A A A A
20 Boiling A A A A A
Inorganic chloride Sodium chloride 25 25 A+ A B+ B+ B
  Boiling A B B+ B+ B+
Ammonium chloride 40 25 A+ A B+ B+ A
  Boiling A+ A C+ B+ A+
Zinc Chloride 20 Boiling A+ A D D D
50 Boiling A A D D D
Magnesium chloride 42 25 A+ A A+ A+ A
  Boiling A A A+ A+ A+
Ferric chloride 30 25 A+ D D D C
  Boiling A D D D D
Inorganic salts Sodium sulfate 20 25 A A A A A
  Boiling A A A A A
Sodium sulfate 10 25 A A A A A
  Boiling A A B B A
Sodium hypochlorite 5 25 A A C C C
15 25 A A C C C
Sodium carbonate 30 25 A A A A A
  Boiling A A A A A
Inorganic salts Methyl alcohol 95 25 A A A A A
Carbon tetrachloride 100 Boiling A A B B B
Phenol Saturation 25 A A A A B
Formaldehyde 37 Boiling A A A A B
Gas Chlorine Dry 25 D A A A A
Wet 25 A+ D+ D+ D+ D+
황하수소 Dry 25 A A C B A
Wet 25 A A B A B
Ammonia 100 40 A A A A A
  100 A A A A A
Others Sea water - 25 A A A+ A+ A
  100 A+ A B+ B+ A+
Fresh water - 80 A A A+ A+ A
  180 A A A+ A+ A
A: 0.125 mm/year or less, B: 0.125-0.5 mm/year, C: 0.5-1.25 mm/year, D: 1.25 mm/year or more
* Local corrosion may occur, such as corrosion in pitting or gaps.
Comparison of physical properties of other metallic materials
Atomic number Atomic weight Specific gravity (g/cm) Melting point (℃) Linear expansion coefficient (/1℃) Specific heat (cal/gr/℃) Thermal conductivity (cal/㎠/sec/℃/cm) Resistivity
Pure Titanium 22 47.9 4.51 1,668 8.4x10(-6) 0.124 0.041 55
Ti alloyTi-6AI-4V 22(Ti) - 4.42 1,540~1,650 8.8x10(-6) 0.13 0.018 171
Zirconium 40 91.22 6.52 1,852 5.8x10(-6) 0.17 0.04 40~54
Hastelloy C - - 8.9 1,305 11.3x10(-6) 0.092 0.03 130
Nickel 28 58.69 8.9 1,453 15x10(-6) 0.11 0.22 9.5
Nickel Alloy
(Monel)		 - - 8.8 1,300~1,350 14x10(-6) 0.13 0.062 48
Aluminium 13 26.97 2.7 660 23x10(-6) 0.21 0.49 2.7
AluminiumAlloy
(75S-T6)		 - - 2.8 476~638 23x10(-6) 0.23 0.29 5.8
AluminiumBrass
(BSTF-2)		 - - 8.4 970 18.5x10(-6) 0.09 0.24 7.5
18-8 Stainless- Steel(SUS304) - - 7.9 1,400~1,420 17x10(-6) 0.12 0.039 72
Iron 26 55.85 7.9 1,530 12x10(-6) 0.11 0.15 9.7
Copper 29 63.57 8.9 1,083 17x10(-6) 0.092 0.92 1.724
Magnesium 12 24.32 1.7 650 25x10(-6) 0.24 0.38 4.3

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