Titanium Forgings

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Titanium alloy refers to various alloy metals made of titanium and other metals. Titanium is an important structural metal developed in the 1950s. Titanium alloys have high strength, good corrosion resistance, and high heat resistance. In the 1950s and 1960s, the main focus was on developing high-temperature titanium alloys for aircraft engines and structural titanium alloys for aircraft bodies.
A batch of corrosion-resistant titanium alloys were developed in the 1970s, and since the 1980s, corrosion-resistant titanium alloys and high-strength titanium alloys have been further developed. Titanium alloy is mainly used to make compressor components for aircraft engines, followed by structural components for rockets, missiles, and high-speed aircraft.
Titanium is a new type of metal, and its properties are related to the impurity content of carbon, nitrogen, hydrogen, oxygen, etc. Pure titanium iodide has an impurity content of no more than 0.1%, but its strength is low and its plasticity is high. The performance of 99.5% industrial pure titanium is as follows: density ρ=4.5g/cm3, melting point 1725 ℃, thermal conductivity λ=15.24W/(m.K), tensile strength σ B =539MPa, elongation δ=25%, cross-sectional shrinkage rate ψ=25%, elastic modulus E=1.078 × 105MPa, and hardness HB195.
High strength
The density of titanium alloy is generally around 4.51g/cm3, which is only 60% of that of steel. Some high-strength titanium alloys exceed the strength of many alloy structural steels. Therefore, the specific strength (strength/density) of titanium alloy is much higher than other metal structural materials, which can produce components with high unit strength, good rigidity, and light weight. The engine components, skeleton, skin, fasteners, and landing gear of the aircraft are all made of titanium alloy.
High thermal intensity
The use temperature is several hundred degrees higher than that of aluminum alloy, and it can still maintain the required strength at moderate temperatures. It can work for a long time at temperatures of 450-500 ℃. These two types of titanium alloys still have high specific strength in the range of 150 ℃ to 500 ℃, while aluminum alloy shows a significant decrease in specific strength at 150 ℃. The working temperature of titanium alloy can reach 500 ℃, while that of aluminum alloy is below 200 ℃.
Good corrosion resistance
Titanium alloys work in humid atmospheres and seawater media, and their corrosion resistance is much better than stainless steel; Has particularly strong resistance to pitting corrosion, acid corrosion, and stress corrosion; Has excellent corrosion resistance to alkali, chloride, organic substances such as chlorine, nitric acid, sulfuric acid, etc. However, titanium has poor corrosion resistance to reducing oxygen and chromium salt media.
Good low-temperature performance
Titanium alloys can maintain their mechanical properties at low and ultra-low temperatures. Titanium alloys with good low-temperature performance and extremely low interstitial elements, such as TA7, can maintain a certain degree of plasticity at -253 ℃. Therefore, titanium alloy is also an important low-temperature structural material.
High chemical activity
Titanium has high chemical activity and reacts with O2 in the atmosphere N2, H2, CO, CO2, Strong chemical reactions occur with water vapor, ammonia, and other substances. When the carbon content is greater than 0.2%, hard TiC will form in the titanium alloy; When the temperature is high, the interaction with N will also form a hard surface, titanium absorbs oxygen to form a hardened layer with high hardness; An increase in hydrogen content can also form a brittle layer. The hard and brittle surface layer generated by gas absorption can reach a depth of 0.1-0.15mm, with a hardening degree of 20% -30%. Titanium has a high chemical affinity and is prone to adhesion with friction surfaces.
Low thermal conductivity and elasticity
The thermal conductivity of titanium, λ=15.24W/(m · K), is about 1/4 that of nickel, 1/5 that of iron, and 1/14 that of aluminum. However, the thermal conductivity of various titanium alloys is about 50% lower than that of titanium. The elastic modulus of titanium alloy is about half of that of steel, so it has poor rigidity and is prone to deformation. It is not suitable for making slender rods and thin-walled parts. During cutting, the springback of the machined surface is large, about 2-3 times that of stainless steel, causing severe friction, adhesion, and bonding wear on the back surface of the tool.