Pure titanium is silver white metal, which has many excellent performances The density of titanium is 4.54g / cm3, 43% lighter than that of steel, slightly heavier than that of long - lasting light metal magnesium. The mechanical strength is almost the same as that of steel, two times larger than aluminum, five times larger than magnesium. Titanium high temperature, melting point 1942K, higher than gold nearly 1000K, higher than steel nearly 500K.
Titanium is a chemically active metal. It can be heated with O2, N2, H2, S and halogen and other non-metallic effects. But under normal temperature, the protective oxide film on titanium surface to produce a very thin layer of dense, can resist strong acid or aqua regia, showed strong corrosion resistance. Therefore, the general solution in acid, alkali, metal salt and titanium has become safe and sound in a disastrous state. The use of titanium alloy: titanium alloy has high strength and small density, good mechanical properties, toughness and corrosion resistance is very good.
(1) the specific strength is high. The density of titanium alloy is about 4.5g/cm3, only 60% of that of steel. The strength of pure titanium is close to that of ordinary steel. Some high-strength titanium alloys exceed the strength of many alloy structural steels. Therefore, the specific strength (strength / density) of the titanium alloy is much larger than that of other metal structural materials, and the zero strength parts with high unit strength, good rigidity and light quality can be produced. Titanium alloys are used in aircraft engines, components, skeletons, diaphragms, fasteners and landing gear.
(2) high thermal strength.
The use of temperature is higher than a few Baidu Aluminum Alloy, can still maintain the required strength at moderate temperatures at 450 ~ 500 DEG C under the long-term work of these two kinds of titanium alloy in the range of 150 to 500 DEG C still have high specific strength, and Aluminum Alloy at 150 DEG C than the strength decreased significantly. The working temperature of titanium alloy is up to 500, while aluminum alloy is below 200.
(3) good corrosion resistance
The titanium alloy work in the atmosphere and seawater wet, its corrosion resistance is much better than that of stainless steel; particularly strong on pitting corrosion, acid corrosion, stress corrosion resistance; the alkali, chlorides, organic substances, nitric acid and sulfuric acid have excellent corrosion resistance. But with titanium on corrosion resistance of chromium and oxygen reduction medium difference
(4) good low temperature performance
Titanium alloys can still maintain their mechanical properties at low temperature and ultra low temperature. The titanium alloy with very low temperature and extremely low interstitial elements, such as TA7, can maintain a certain plasticity at -253. Therefore, titanium alloy is also an important low temperature structural material.
(5) large chemical activity
The chemical activity of titanium is large, and it has a strong chemical reaction with O, N, H, CO, CO2, water vapor and ammonia gas in the atmosphere. The carbon content of more than 0.2%, will form a hard TiC in titanium alloy; high temperature, also can interact with N to form TiN hard surface; in 600 degrees above, titanium absorb oxygen to form hardened layer of high hardness; the hydrogen content increased, will be the formation of brittle layer. The surface of hard and brittle surface produced by absorbing gas can reach 0.1 ~ 0.15 mm, and the degree of hardening is from 20% to 30%. The chemical affinity of titanium is also large, which makes it easy to adhere to the friction surface.
(6) small thermal conductivity, low modulus of elasticity
The thermal conductivity of titanium is about =15.24W/ (m.K), which is about 1/4 of nickel, 1/5 of iron and 1/14 of aluminium. However, the thermal conductivity of various kinds of titanium alloy is about 50% lower than that of titanium. The elastic modulus of titanium alloy steel is about 1/2, so the poor rigidity, easy deformation, not suitable for slender rod and thin wall parts, springback cutting surface is large, about 2 ~ 3 times of stainless steel, which flank friction, adhesion and adhesion wear.
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