Titanium - Performance
Titanium - Performance
Titanium is a new type of metal, and the performance of the carbon-containing titanium impurity content of nitrogen, hydrogen, oxygen and so on, the most pure titanium iodide impurities is not more than 0.1%, but its low strength, high ductility. 99.5% of the performance of commercially pure titanium: the density ρ = 4.5g / cm3, a melting point of 1800 ℃, thermal conductivity λ = 15.24W / (mK), tensile strength σb = 539MPa, elongation δ = 25%, necking ratio ψ = 25%, the modulus of elasticity E = 1.078 × 105MPa, the hardness HB195.
(1) high specific strength
The density of titanium is generally about 4.5g / cm3, only 60% of steel, titanium's strength close to the strength of ordinary steel, some high-strength titanium alloy strength than many structural steel. Therefore, the ratio of titanium strength (strength / density) is much larger than other metal structural materials can be prepared by a high specific strength, rigid, lightweight parts and components. Use of titanium in aircraft engine components, skeleton, skin, fasteners and landing gear and so on.
(2) high thermal strength
Temperature hundreds of degrees higher than aluminum, at moderate temperatures can still maintain the desired strength, long-term work at a temperature of 450-500 ℃ of these two types of titanium alloys in the range of 150 ℃ -500 ℃ still very high strength, and aluminum at 150 ℃ decreased significantly when compared strength. Titanium operating temperature up to 500 ℃, aluminum is below 200 ℃.
(3) good corrosion resistance
Titanium work in a humid atmosphere and seawater, the corrosion resistance is far better than that of stainless steel; for pitting, etching, stress corrosion resistance particularly strong; alkali, chloride, chlorine organic materials, nitric acid, sulfuric acid etc. have excellent corrosion resistance. But the corrosion resistance of titanium having reducing oxygen and chromium salts medium difference.
Good (4) low temperature performance
Titanium alloys at low and ultra-low temperature, retain their mechanical properties. Low temperature performance, low interstitial elements titanium, such as TA7, at -253 ℃ can maintain a certain degree of plasticity. Thus, titanium is also an important low-temperature structural materials.
Chemically active titanium is large, a strong chemical reaction with atmospheric O, N, H, CO, CO2, water vapor, ammonia and the like. Carbon content greater than 0.2%, it will form a hard TiC in the titanium alloy; at higher temperatures, and also the role of N forms TiN hard surface; above 600 ℃, the high hardness of hardened layer to absorb oxygen to form titanium ; the hydrogen content increased, brittle layer will form. Absorbing gas produced brittle surface layer depth of up 0.1-0.15mm, the degree of hardening of 20% to 30%. Titanium chemical affinity is also large, easy and sticking friction surface.
(6) thermal conductivity, small elastic modulus
Thermal conductivity of titanium λ = 15.24W / (m.K) approximately 1/4 of nickel, iron 1/5, 1/14 of aluminum, while the thermal conductivity of titanium decreased by 50% than the thermal conductivity of titanium. The elastic modulus of about 1/2 of titanium steel, so the poor rigidity, deformation, not making the elongated rod and thin-walled parts, cutting the amount of rebound machined surface is large, stainless steel is about 2 to 3 times, causing severe friction of tool flank, adhesion, adhesive wear.
Titanium has a high strength and small density, good mechanical properties, good toughness and corrosion resistance. In addition, technological properties of titanium alloys is poor, difficult machining, thermal processing, it is very easy to absorb nitrogen hydrogen carbon and other impurities. There are poor abrasion resistance, complex production process. Titanium industrial production began in 1948. It requires the development of the aviation industry, the titanium industry with an average annual growth rate of about 8% of the development. World titanium processing material production reached 40,000 tons, nearly 30 kinds of titanium alloys. The most widely used titanium alloy is Ti-6Al-4V (TC4), Ti-5Al-2.5Sn (TA7) and commercially pure titanium (TA1, TA2 and TA3).
Titanium is mainly used for the production of aircraft engine compressor components, followed by structures rockets, missiles and high-speed aircraft. The mid-1960s, titanium and its alloys have applications in general industry, manufacture of the electrode electrolysis industry for power plant condensers, oil refining and desalination heater and environmental pollution control devices. Titanium and its alloys have become a corrosion resistant structural materials. In addition, for the production of hydrogen storage materials and shape memory alloys. China began in 1956, titanium and titanium alloy study; the mid-1960s and the development of industrial production of titanium into TB2 alloy.