13-05-2025
- Automotive
- Time Business News
Titanium Alloys in the Automobile Industry
In recent years, with the rapid development of the automobile industry, the fuel consumption, environmental protection and safety issues generated by automobiles have attracted increasing attention. Looking forward to the future development direction of the automobile industry, lightweight, low fuel consumption and low emissions are the themes of development. According to statistics from international authoritative departments, 60% of the energy of automobile fuel combustion is consumed by its own weight. Although high-strength thin steel plates, aluminum, magnesium, metal-based composite materials and plastic resin materials have played a role in reducing the weight of automobiles, the emergence of industrial titanium materials has made automobile manufacturing a better choice.
Titanium metal has the advantages of low density, high specific strength and good corrosion resistance. The use of titanium materials in automobiles can greatly reduce the weight of the car body, reduce fuel consumption, improve the working efficiency of the engine, improve the environment and reduce noise. However, the high price makes titanium alloys only have some applications in luxury models and sports cars in the automobile industry, and rarely in ordinary cars. Therefore, research and development of low-cost titanium alloys manufacturing that meet market needs is the key to promoting its application in ordinary household cars.
Although titanium alloys have been widely used in aerospace, petrochemical and shipbuilding industries, their application in the automotive industry has developed slowly. Since the successful development of the first all-titanium car by General Motors in the United States in 1956, titanium automotive parts did not reach the level of mass production until the 1980s. In the 1990s, with the increasing demand for luxury cars, sports cars and racing cars, titanium parts have developed rapidly. In 1990, the amount of titanium used in automobiles worldwide was only 50 tons, which reached 500 tons in 1997, 1100 tons in 2002, and 3000 tons in 2009. It is expected that the amount of titanium used in automobiles worldwide will exceed 5000 tons in 2015. At present, the following titanium alloy parts are commonly used.
Titanium alloy is an ideal choice for connecting rod materials. 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 mass by 15% to 20%. The application of titanium alloy connecting rods was first reflected in the new Italian Ferrari 3.5LV8 and Acura NSX engines. The materials used for titanium alloy connecting rods are mainly Ti-6Al-4V, Ti-10V-2Fe-3Al, Ti-3Al-2.0V and Ti-4Al-4Mo-Sn-0.5Si, and other titanium alloy materials such as Ti-4Al-2Si-4Mn and Ti-7M-4Mo are also being developed for use in connecting rods.
Automobile engine valves made of titanium alloy can not only reduce weight and extend service life, but also reduce fuel consumption and improve the reliability of the car. Compared with steel valves, titanium valves can reduce weight by 30% to 40%, and the engine limit speed can be increased by 20%. As far as current applications are concerned, the intake valve material is mainly Ti-6Al-4V, and the exhaust valve material 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 performance of titanium alloy, enhance the strength of quenched and aged titanium alloy, and increase hardness. Other titanium alloys with development potential are:
1) The intake valve can be made of Ti-62S, which has the same characteristics as Ti-6Al-4V and is cheaper.
2) The exhaust valve can be made of Ti-6Al-2Sn-4.0Zr-0.4-Mo-0.45Si. Due to the lower Mo content, its creep resistance is better than Ti-6242S, and the oxidation resistance temperature can reach 600℃.
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 processing by traditional forging methods, and is only suitable for casting and powder metallurgy.
High strength and fatigue resistance are the properties that valve spring seats must have. β-titanium alloy is a heat-treatable 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 seat on its mass-produced cars, which reduces the mass by 42% compared with the original steel lock, reduces the inertial mass of the valve mechanism by 6%, and increases the maximum engine speed by 300r/min.
Titanium and its alloys have a lower elastic modulus and a large σs/E value relative to steel materials, and are 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 that of steel springs, and the mass is only 30% to 40% of that of steel springs, which is convenient for body design. In addition, the excellent fatigue performance and corrosion resistance of titanium alloys can increase the service life of springs. At present, titanium alloy materials that can be used to manufacture automotive springs include Ti-4.5Fe6.8Mo-1.5Al and Ti-13V11C-3Al.
Turbochargers can improve the combustion efficiency of the engine and enhance the power and torque of the engine. The turbine rotor of the turbocharger needs to work in high-temperature exhaust gas above 850℃ 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 point. Although ceramic materials are used in turbine rotors because of their light weight and good high-temperature resistance, their application is limited due to high cost and the inability to optimize the shape. In order to solve these problems, Tetsui et al. developed the TiAl turbine rotor. After many tests and verifications, it not only has good durability and efficiency, but also can improve the acceleration of the engine. This design has been successfully commercialized in the Mitsubishi Lancer Evolution series.
Titanium is used in large quantities in the exhaust system of automobiles. Exhaust systems made of titanium and its alloys can not only improve reliability, extend life and improve appearance, but also reduce weight and improve fuel combustion efficiency. Compared with steel exhaust systems, titanium exhaust systems can reduce weight by about 40%. In the Golf series of cars, the weight of titanium exhaust systems can be reduced by 7 to 9 kg. At present, the titanium used in exhaust systems is mainly industrial pure titanium.
The weight of a titanium muffler is only 5 to 6 kg, which is lighter than mufflers such as stainless steel. The 2000 Chevrolet Corvette Z06 uses an 11.8 kg titanium muffler and tailpipe system to replace the original 20 kg stainless steel system, reducing the weight by 41%. The strength of the replaced system remains unchanged, and the car is faster, more flexible and fuel-efficient. The titanium used in the muffler is also mainly industrial pure titanium.
In order to improve the safety and reliability of the car, it is necessary to consider the design and manufacturing aspects, especially the manufacturing materials. Titanium is a good material for making body frames. It not only has high specific strength, but also has good toughness. In Japan, automobile manufacturers choose pure titanium metal welded tubes to make body frames, which can make drivers feel safe enough when driving.
In addition to the above parts, titanium is also used in engine rocker arms, suspension springs, engine piston pins, automotive fasteners, lug nuts, car door protrusion beams, car stop brackets, brake caliper pistons, pin bolts, pressure plates, shift buttons and car clutch discs and other automotive parts.
Titanium alloys have the advantages of lightweight, high specific strength, and good corrosion resistance, so they are widely used in the automotive industry. The most widely used titanium alloy is the automotive engine system. There are many benefits to using titanium alloys to manufacture engine parts, mainly manifested in:
1) The low density of titanium alloys can reduce the inertial mass of moving parts. At the same time, titanium valve springs can increase free vibration, reduce 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 the fuel efficiency of the engine.
3) The choice of 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 whole vehicle.
4) The reduction of the inertial mass of parts reduces vibration and noise, and improves the performance of the engine.
The application of titanium alloy in other parts can improve the comfort of personnel and the beauty of the car. In the application of the automotive industry, titanium alloy plays an immeasurable role in energy saving and consumption reduction.
Although titanium alloy parts have such superior performance, there is still a long way to go before titanium and its alloys are widely used in the automotive industry. The reasons include expensive prices, poor formability and poor welding performance.
With the development of titanium alloy near-net forming 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 hindering the widespread application of titanium alloys in the automotive industry is still the high cost.
Whether it is the initial smelting of the metal or the subsequent processing, the price of titanium alloys is much higher than that of other metals. The acceptable cost of titanium parts for the automotive industry is 8 to 13 US dollars/kg for titanium connecting rods, 13 to 20 US dollars/kg for titanium valves, and less than 8 US dollars/kg for titanium springs, engine exhaust systems and fasteners. However, the 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.
At present, reducing costs is the main research direction of titanium alloys for the automotive industry. In view of the characteristics of the cost distribution of titanium alloys for the automotive industry, material research and development workers mainly achieve the purpose of reducing costs from the following two aspects: developing new low-cost alloy systems and using new processing and preparation technologies.
Workers from various countries have developed new low-cost titanium alloy systems, mainly focusing on the following aspects: alloy design using cheap alloy elements and alloy design to improve processing characteristics. Among them, Japan and the United States are representatives, and China has also successfully developed two low-cost titanium alloys, namely Ti8LC and Ti12LC. In the design of low-cost titanium alloy components for automobiles, the commonly used cheap alloy elements are Fe, Cr, Si, Al, etc.
The processing cost of titanium alloy materials accounts for more than 60% of the total cost during the production process. Therefore, in terms of reducing costs, how to reduce the processing cost of titanium alloys has become a key research direction. The research in this area is mainly divided into two aspects: one is to improve the traditional casting and forging process, and the other is to use powder metallurgy near-net forming technology.
In the research and development of new forging processes, cold forging is currently one of the most promising methods for titanium alloys to manufacture automotive parts. β-titanium alloy has low deformation resistance at room temperature and good cutting processing and forming. It is a material that can be cold forged. At present, Japan has developed three cold-deformed β-titanium alloys. β-titanium alloy also has some shortcomings. It is easy to produce uneven deformation during cold forging and is easy to adhere to the mold. Therefore, the mass production of β-titanium alloy parts using cold forging technology requires further exploration and development.
In terms of reducing the processing cost of titanium alloys, powder metallurgy is a very important technology. In the manufacturing of powder metallurgy automotive parts, the traditional pressing-sintering method is still dominant, mainly including the element powder method (BE) and the pre-alloyed powder method (PA). At present, the element powder method is the most widely used in the field of low-cost automotive titanium alloy powder metallurgy because of its simple process and lower cost. In recent years, other powder metallurgy technologies have also been emerging, including laser forming technology, metal powder injection molding (MIM) and other technologies, which have been widely used in the trial production and production of complex automotive parts, which can greatly shorten the product development and production cycle and further reduce costs.
The new generation of automobile design pays more attention to the lightweight body, low fuel consumption, low noise and light vibration of the engine to meet the increasingly stringent environmental requirements. In this context, light metal titanium will become a major application material for future automobiles.
Taking into account the current status of low-cost titanium alloy research for automobiles, it can be found that in order to further reduce the cost of titanium alloy for automobiles, the following aspects should be mainly focused on:
1) In the development of low-cost alloy systems, try to develop alloy systems that do not use or use less expensive alloy elements without affecting performance, and at the same time, fully develop and utilize recycled titanium alloys.
2) In the development of casting and forging technology, develop in the direction of developing β titanium alloys and cold-deformed titanium alloys, and conduct feasibility studies on their mass production.
3) In powder metallurgy, while ensuring a low-cost advantage, it is necessary to further improve the performance of titanium parts.
With the development of the economy and the reduction of titanium costs, more engineering designers will choose titanium parts as automotive parts. Titanium alloys will eventually occupy an important position in the production of the automotive industry.
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