Titanium Applications in The Auto Industry

Although titanium alloys have been widely used in aerospace, petrochemical and shipbuilding industries, their application in the automotive industry has developed slowly. Starting from the successful development of the first all-titanium car by General Motors in the United States in 1956, titanium auto parts did not reach the level of mass production until the 1980s. In the 1990s, as the demand for luxury cars, sports cars, and racing cars increased year by year, titanium auto parts Manufactured parts have developed rapidly. In 1990, the amount of titanium used in automobiles around the world was only 50t. In 1997, it reached 500t. In 2002, it reached 1,100t. In 2009, it reached 3,000t. It is expected that the amount of titanium used in automobiles around the world will exceed 5,000t in 2015. At present, the following types of titanium alloy parts are commonly used.

1. Engine connecting rod
Titanium alloy is an ideal material for connecting rods. Engine connecting rods made of titanium alloy can effectively reduce engine mass, improve fuel efficiency and reduce exhaust volume. Compared with steel connecting rods, titanium connecting rods can reduce the mass by 15% to 20%. The application of titanium alloy connecting rods was first reflected in Italy's new Ferrari sedan 3.5LV8 and Acura's NSX engine. The main materials used in titanium alloy connecting rods are Ti-6Al-4V, Ti-10V-2Fe-3Al, Ti-3Al-2.0V and Ti-4Al-4Mo-Sn-0.5Si. Other titanium alloy materials such as Ti-4Al The application of -2Si-4Mn and Ti-7M-4Mo in connecting rods is also under development.
2.Engine valve
Automotive engine valves made of titanium alloy can not only reduce mass and extend service life, but also reduce fuel consumption and improve vehicle reliability. Compared with steel valves, titanium valves can reduce mass by 30% to 40%, and the engine's limit speed can be increased by 20%. As far as current applications are concerned, the material of the intake valve is mainly Ti-6Al-4V, and the material of the exhaust valve is mainly Ti-6242S. Usually Sn and Al are added together to obtain lower brittleness and higher Strength; the addition of Mo can improve the heat treatment properties of titanium alloys, enhance the strength of quenching and aging titanium alloys, and increase the hardness. Other titanium alloys with development potential include:
1) The intake valve can be made of Ti-62S, which has properties equivalent to Ti-6Al-4V and is cheaper.
2) The exhaust valve can be made of Ti-6Al-2Sn-4.0Zr-0.4-Mo-0.45Si. Because of its lower Mo content, its creep resistance is better than Ti-6242S, and its oxidation resistance can reach 600°C. .
3) The exhaust valve can be made of γ-TiAl, which has the characteristics of high temperature resistance and light weight, but it is not suitable for traditional forging methods during processing. It is only suitable for casting and powder metallurgy processing.
3. Valve spring seat
High strength and fatigue resistance are necessary properties for the valve spring seat. Beta titanium alloy is a heat-treated alloy that can obtain high strength through solid solution aging treatment. The corresponding more suitable materials are Ti-15V-3Cr- 3Al-3Sn and Ti-15Mo-3Al-2.7Nb-0.2Si. Mitsubishi Motors uses Ti-22V-4Al titanium alloy valve spring seats in its large-scale production vehicles, which reduces the mass by 42% compared with the original steel locks, reduces the inertial mass of the valve mechanism by 6%, and increases the maximum engine speed. 300r/min.
4.Titanium alloy spring
Titanium and its alloys have lower elastic modulus and larger σs/E value than steel materials, making them suitable for manufacturing elastic components. Compared with steel automobile springs, under the premise of the same elastic work, the height of titanium springs is only 40% of steel springs, and the mass is only 30% to 40% of steel springs, which facilitates car body design. In addition, the excellent fatigue properties and corrosion resistance of titanium alloy can extend the service life of the spring. Currently, titanium alloy materials that can be used to make automobile springs include Ti-4.5Fe6.8Mo-1.5Al and Ti-13V11C-3Al.
5. Turbocharger
Turbochargers can improve engine combustion efficiency and enhance engine power and torque. The turbine rotor of the turbocharger needs to work in high-temperature exhaust gas above 850°C for a long time, so it requires good heat resistance. Traditional light metals such as aluminum alloys cannot be used due to their low melting points. Although ceramic materials are used in turbine rotors due to their light weight and good high temperature resistance, their application is limited due to their high cost and inability to optimize their shape. In order to solve these problems, Tetsui and others developed the TiAl turbine rotor. After many tests, it has been verified that it not only has good durability and efficiency, but also can improve the acceleration of the engine. This design has been successfully commercialized on the Mitsubishi Lancer Evolution series.
6. Exhaust system and muffler
Titanium is used extensively in automobile exhaust systems. Exhaust systems made of titanium and its alloys can not only improve reliability, extend life and improve appearance, but also reduce mass and improve fuel combustion efficiency. Compared with steel exhaust systems, titanium exhaust systems can reduce mass by approximately 40%. In Golf series cars, the mass of the titanium exhaust system can be reduced by 7 to 9 kg. Currently, the titanium material used in the exhaust system is mainly industrial pure titanium.
The titanium muffler weighs only 5 to 6 kg, which is lighter than stainless steel and other mufflers. The 2000 Chevrolet Corvette Z06 uses an 11.8kg titanium muffler and exhaust pipe system instead of the original 20kg stainless steel system, reducing the mass by 41%. The replaced system maintains its strength and makes the car faster, more flexible and more fuel efficient. The titanium material used in the muffler is also mainly industrial pure titanium.
7. Body frame part
In order to improve the safety and reliability of automobiles, it is necessary to consider the design and manufacturing aspects, especially the manufacturing materials. Titanium is a very good material used to make car body frames. It not only has high specific strength, but also has good toughness. In Japan, automobile manufacturers choose pure titanium welded pipes to make body frames. This kind of frame can make drivers feel safe when driving.
8. Other titanium alloy parts
In addition to the above components, titanium is also used in engine rocker arms, suspension springs, engine piston pins, automotive fasteners, lug nuts, automotive door protruding beams, automotive gear brackets, brake caliper pistons, pin bolts, pressure Auto parts such as plates, shift buttons and automobile clutch discs.

1.Advantages

Titanium alloys have the advantages of light weight, high specific strength, and good corrosion resistance, so they are widely used in the automobile industry. The most common use of titanium alloys is in automobile engine systems. There are many benefits to using titanium alloys to manufacture engine parts, mainly in:
1) The low density of titanium alloy can reduce the inertial mass of moving parts. At the same time, titanium valve springs can increase free vibration, weaken the vibration of the car body, and increase the engine speed and output power.
2) Reduce the inertial mass of moving parts, thereby reducing friction and improving engine fuel efficiency.
3) Choosing titanium alloy can reduce the load stress of related parts and reduce the size of parts, thereby reducing the weight of the engine and the entire vehicle.
4) The reduction of the inertial mass of components reduces vibration and noise and improves engine performance.
The application of titanium alloys in other components can improve personnel comfort and the aesthetics of cars. In applications in the automotive industry, titanium alloys have played an immeasurable role in energy saving and consumption reduction.
2. Application restrictions
Although titanium alloy parts have such superior properties, there is still a long way to go before titanium and its alloys are widely used in the automotive industry. The reasons include high price, poor formability and poor welding performance.
With the development of titanium alloy near net shape technology and modern welding technologies such as electron beam welding, plasma arc welding, and laser welding in recent years, the forming and welding problems of titanium alloys are no longer the key factors restricting the application of titanium alloys. The main reason why it is widely used in the automotive industry is the high cost.
Whether it is the initial smelting of the metal or subsequent processing, the price of titanium alloys is much higher than that of other metals. The cost of titanium parts that the automobile industry can accept is 8 to 13 US dollars/kg for connecting rods, 13 to 20 US dollars for valves, and 8 for springs, engine exhaust systems, and fasteners. Below USD/kg. The current cost of parts produced with titanium materials is much higher than these prices. The production cost of titanium plates is mostly higher than 33 US dollars/kg, which is 6 to 15 times that of aluminum plates and 45 to 83 times that of steel plates.