Titanium and aerospace have an inseparable relationship. In 1953, the 1st use of titanium in the engine pods and firewalls of the DC-T aircraft produced by the United States Douglas, thus opening the history of titanium used in the aerospace applications. Since then, titanium has been used in aviation for more than half a century.
Titanium is widely used in aviation because it has many valuable properties suitable for aircraft applications. Today we will talk about why do CNC Machining Aerospace Parts prefer to use Titanium Alloy materials?
The introduction of titanium
Only in 1948 the United States DuPont Company with magnesium method tons of production of titanium sponge -- this marks the beginning of industrial production of titanium sponge that is titanium.
And titanium alloy is widely used in various fields because of its high specific strength, good corrosion resistance, heat resistance and other characteristics.
Titanium is rich in the earth's crust, ranking 9th in content, much higher than copper, zinc, tin and other common metals. Titanium is widely found in many rocks, especially in sand and clay.
The characteristics of titanium
1.High strength: 1.3 times that of aluminum alloy, 1.6 times that of magnesium alloy, 3.5 times that of stainless steel, the champion of metal materials.
2.High thermal strength: the use temperature is several hundred degrees higher than aluminum alloy, and can work for a long time at a temperature of 450-500℃.
3.Good corrosion resistance: resistant to acid, alkali, atmospheric corrosion, and particularly strong resistance to pitting and stress corrosion.
4.Good low temperature performance: Titanium alloy TA7 with very low interstitial elements can still maintain a certain degree of plasticity at -253℃.
5.High chemical activity: High chemical activity at high temperature, easily reacts chemically with air impurities such as hydrogen and oxygen to generate a hardened layer.
6.Small thermal conductivity, small elastic modulus: the thermal conductivity is about 1/4 of nickel, 1/5 of iron, 1/14 of aluminum, and the thermal conductivity of various titanium alloys is about 50% lower than that of titanium. The modulus of elasticity of titanium alloy is about 1/2 of that of steel.
The classification and use of titanium alloys
Titanium alloys can be divided into: heat-resistant alloys, high-strength alloys, corrosion-resistant alloys (titanium-molybdenum, titanium-palladium alloys, etc.), low-temperature alloys and special functional alloys (titanium-iron hydrogen storage materials and titanium-nickel memory alloys).
Although titanium and its alloys have a short history of application, they have been awarded several honorable titles due to their outstanding performance. The first one is the "space metal". Its light weight, strength and high temperature resistance make it particularly suitable for the manufacture of aircraft and various spacecraft.
About 75% of the titanium and titanium alloys produced in the world are currently used in the aerospace industry. Many parts originally made of aluminum alloys have been replaced with titanium alloys.
The applications for Titanium in CNC Machining Aerospace Parts
Titanium alloy is mainly used in aircraft and engine manufacturing materials, such as forging titanium fans, compressor discs and blades, engine covers, exhaust devices and other parts, as well as the aircraft beam spacer and other structural framework parts.
Spacecraft mainly use titanium alloy's high specific strength, corrosion resistance and low temperature resistance to manufacture a variety of pressure vessels, fuel tanks, fasteners, instrument straps, frames and rocket shells. Artificial earth satellite, moon module, manned spacecraft and space shuttle also use titanium alloy plate welded parts.
The more advanced the aircraft, the more titanium is used. U.S. F-14A fighter aircraft use titanium, accounting for about 25% of the weight of the aircraft; F-15A fighter aircraft for 25.8%; U.S. fourth-generation fighter aircraft with 41% of the amount of titanium, its F119 engine with 39% of the amount of titanium, is currently the highest amount of titanium aircraft.
Reasons for titanium alloy being used in aviation
The maximum speed of modern aircraft navigation has reached more than 2.7 times the speed of sound. Such a fast supersonic flight will make the aircraft generate a lot of heat by friction with the air. When the flight speed reaches 2.2 times of the speed of sound, the aluminum alloy can't stand it anymore. High temperature resistant titanium alloy must be used.
When the aero-engine thrust-to-weight ratio from 4 ~ 6 to 8 ~ 10, the compressor outlet temperature correspondingly from 200 ~ 300 ℃ to 500 ~ 600 ℃, the original aluminum manufacturing of low-pressure compressor disc and blade must be changed to titanium alloy.
Titanium alloy instead of stainless steel manufacturing high-pressure compressor disc and blade, can reduce the weight of the structure. For every 10% weight reduction in aircraft, fuel savings of 4% can be achieved. For rockets, every 1kg of weight reduction can increase the range by 15km.
The CNC Machining characteristics for titanium
First of all, titanium alloy thermal conductivity is low, only 1/4 of steel, aluminum 1/13, copper 1/25. because of the slow heat dissipation in the cutting area, is not conducive to thermal balance, in the cutting process, heat dissipation and cooling effect is very poor, easy to form high temperature in the cutting area, after processing parts deformation rebound, resulting in increased cutting tool torque, edge wear fast, durability reduced.
Secondly, the low thermal conductivity of titanium alloy, so that cutting heat accumulates in the small area near the cutting tool is not easy to dissipate, the front tool surface friction increases, not easy to chip, cutting heat is not easy to dissipate, accelerating tool wear.
Finally, titanium alloy chemical activity is high, processing at high temperatures is easy to react with the tool material, the formation of soluble, diffusion, resulting in sticky knife, burning knife, broken knife and other phenomena.
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