Application and Development of Lightweight Material for Automobile
Car lightweight is an important means to achieve energy-saving emission reduction and methods, in improving the fuel economy and environmental protection has an important role. At present, the lightweight new material is the main way of the current body weight reduction, through the multi-material structure optimization, both to improve vehicle performance, but also significantly reduce the quality. This chapter discusses the performance and application of several lightweight materials, describes the development of lightweight materials in the automotive industry and the application of the trend
Key words: automotive i¼›lightweight i¼›lightweight materials
The study of lightweight car is a mainstream of modern car design and manufacturing. Car lightweight, is to ensure the strength and safety of the car under the premise of the car as much as possible to reduce the quality of the preparation, thereby enhancing the vehicle’s power, reduce fuel consumption and reduce exhaust pollution. Data show that if the car to reduce the quality of 10%, fuel efficiency can be increased by 6% to 8%, fuel consumption can be reduced by 6% to 10%. Fuel consumption decline, emissions also decreased, while resource utilization increased, extended life of the car, the use of performance has improved significantly. Car body quality accounts for about 50% of the quality of the vehicle, it is clear that the lightweight body for the vehicle lightweight play a pivotal role . At present, the car body weight reduction has two main research directions: First, the use of lightweight materials; Second, optimize the structure. Structural optimization potential space has been very small, the gradual use of lightweight new materials is the current body of one of the main means of lightweight.
1 New high strength steel
In recent years, with the progress of metallurgical technology, on the basis of high-strength steel, with ultra-low carbon as the basic characteristics, and gradually formed with deep drawing, high strength, baking hardening performance of new high-strength steel. At present, the use of high-strength automotive body is mainly sheet metal and pipe. Mainly: (1) BH steel (bake hardening steel). BH steel plate yield strength in the baking paint increased, without loss of formability under the premise of improving the anti-depression, can reduce the steel plate, mainly for high strength and difficult to form parts, such as roof, Doors, luggage and other components, the main use of tensile strength of 340 ~ 390MPa BH steel plate. (2) RIP steel (phase change induced plastic steel). Mainly used for the collision must absorb more energy when the high-strength structural parts, such as body frame. (3) MS steel (martensitic phase steel). Used to hit the high impact parts, that is, in a very short collision deformation stroke to absorb a lot of energy, such as side crash protection. (4) boron steel. Used to require high strength and high degree of molding of parts, can minimize the quality. Such as A, B column reinforcement, etc. .
Practice has proved that when the thickness of the steel were reduced 0.05,0.10,0.15 mm, the body weight loss were 6%, 12%, 18%. In terms of development trends, the use of new high-strength steel plate in the body is constantly thinning, while the body strength has increased, while increasing the safety of the car, reducing noise and vibration, improve fuel efficiency and reduce the overall quality of the car. The cost did not increase, while the acceleration, driving performance has improved. Whether from the cost point of view, or from the performance point of view, the new high-strength steel plate is to meet the lightweight body to improve the safety of the collision of the best materials. The proportion of new high-strength steel plates used in various automobile factories is increasing. Japan’s Mitsubishi Pajero (SPORT) for the company’s latest SUV car designed a new body structure, body 70% of the components made of high-strength steel plate, the vehicle’s torsional stiffness even higher than the Grand Cherokee 45% Body carrying capacity of up to 2t or more. Ford’s Windstar body frame 60% is high strength steel. Toyota’s new Vitz body structure in high-strength steel accounted for 48%, than the company’s Starlet car to reduce the quality of 17kg.
However, the high strength of the steel sheet is liable to cause a decrease in plasticity, a poor formability, and an increase in yield strength, which causes surface distortion and springback, and increases the shape’s instability. Thus, high strength steel sheets are a difficult to form material. Thermoforming technology is a new type of high-strength stamping parts for the advanced manufacturing technology, can be used to form a strength of up to 1500MPa stamping parts, including the thermoforming process is stamping The frontier technology of the field can be widely used in the production of front and rear bumper, A-pillar, B-pillar, C-pillar, roof structure, door interior plate, door anti-collision beam and other components.
2 light alloy material
2.1 aluminum and aluminum alloy
Aluminum is the ideal choice for lightweight car, the resource is wide, lightweight, recycling, saving resources, absorbing impact energy, corrosion resistance, is the best overall performance of the basic material. The aluminum alloy used in the body is mainly deformed aluminum alloy, mainly AI-Cu-Mg system (2000 series), AI-Mg system (5000 series), AI-Mg-Si series (6000 series), AI-Mg- Zn-Cu system. Which 2000 series and 6000 series is heat treatment can strengthen the alloy, while the 5000 series is heat treatment can not strengthen the alloy. The former through the coating drying process after the strength is improved, mainly for the body outside the board and other emphasis on strength, stiffness of the site, such as car cover, hood, lift rear door, front fender, etc .; the latter excellent shape, Mainly used in the body plate and other complex parts of the shape, such as car floor structure and so on. At present, low density, high strength, high elastic modulus and superplasticity of the AI-Li alloy and aluminum anti-vibration plate, etc. has been gradually applied to the body.
Aluminum alloy has good formability. Aluminum alloy body structure mainly used aluminum extrusion profiles as the main body of the space frame structure, generally with medium and strong aluminum can meet the requirements. Extrusion profiles are mainly hollow materials, in addition to light weight, high rigidity, high temperature strength, heat resistance, corrosion resistance is also very good, and can be welded, surface treatment and bending processing. The current aluminum body is made of thick-walled forged aluminum beams, and is more advantageous than stamping thin steel in terms of structural strength and stiffness, and the overall stability of the mechanism is better. Lightweight and high-strength aluminum body more solid than the traditional steel body, and do not worry about corrosion caused by the reduction of strength .
From the aluminum panel application development trend, high strength, good forming processability, excellent surface quality aluminum plate will replace the steel plate as the main material of the car cover. The late 90s of the 20th century, there have been from the hood, fender and other parts of the body aluminum plate gradually developed into the body all the use of aluminum panels of the car, compared to steel plate by 40% to 50% of the results. Europe and the United States more developed aluminum industry, so Europe and the United States in the aluminum car to go ahead Europe and the United States and Japan in the automotive industry competition and its domestic energy and environmental legislation to promote the acceleration of the car lightweight (aluminum) pace. Germany Audi A8 sedan body are made of aluminum, the framework of three-dimensional frame structure, the cover for the aluminum stamping, was rated as one of the world’s important scientific and technological achievements in 1994 one of the 100. This aluminum body compared with the steel body, the quality of 30% to 50%, fuel consumption reduced by 5% to 8%. Japan Honda’s car body with aluminum alloy up to 162kg, steel body weight loss of about 40%. And China’s aluminum production, prices, the comprehensive impact of the technical level of the automotive industry, making aluminum and its alloys still can not be used in a large number of cars. Increase the variety, improve quality and reduce costs, has become China’s aluminum processing industry and the automotive industry to the world’s advanced level of development research ‚
Specific strength and specific stiffness of aluminum metal-based composite materials research and development success for the further development of automotive lightweight provides a way. Germany’s Kaman company developed a laminated aluminum, the outer layer is aluminum, the middle is foam aluminum, used as body panels, stiffness increased by 10 times, while the quality of 50%. Hyundai is developing a high-performance, high-speed, safe, comfortable, energy-saving and low-pollution direction. The development of high-performance automotive aluminum alloy and the recycling of scrap automotive materials has become an imperative issue. Scientific research and investment will bring huge economic and social benefits. With the rapid solidification of aluminum alloy, powder metallurgy aluminum alloy, superplasticity aluminum alloy, aluminum composite materials and foam aluminum and other new materials development and application of the future aluminum in the automotive application will be further expanded, and will show castings, Profiles, plates simultaneously situation. Aluminum is expected to be the second largest automotive material after steel .
2.2 magnesium alloy
Magnesium alloy is a lighter weight material than aluminum alloy, heat, pressure, corrosion resistance and easy to use, is a typical green structural materials. At present, the deformation of the magnesium alloy material for the body structure of the United States developed high strength ZK60 deformation of magnesium alloy, developed by Japan ultra-high strength IM Mg – Y deformation of magnesium alloy, and can be cold processing of magnesium alloy sheet. Europe is using and developing more than 60 kinds of magnesium alloy auto parts. Germany to fly more cooperation with the German Volkswagen, ready to replace its patented product magnesium alloy Mn E21 a car car body parts, such as front and rear bumper, roof beams and door anti-collision rods and so on. If the success of the replacement, will greatly reduce the car’s body quality .
China is a large resource of magnesium, magnesium ore products and more species, rich reserves, accounting for the world’s available magnesium reserves of about 70% of reserves. 2010 magnesium alloy production line in China’s Shanxi, Shaanxi, Tianjin, Ningxia, Chongqing and other places put into operation, including magnesium-based alloy auto parts project has been in the development and production. Magnesium alloy in the automotive application increased year by year, is expected in the next 20 years, the amount of magnesium on the car will be more than 100kg per vehicle, is the current use of 30 times. Magnesium will become a new material for most structural parts of the car.
3 engineering plastics and composite materials
Engineering plastics and composites are another important type of automotive lightweight material. Compared with the general plastic, engineering plastics have excellent mechanical properties, chemical resistance, heat resistance, wear resistance, dimensional stability and other characteristics, than the replacement of metal materials and light energy when molding less. At present, most of the engineering plastics used in the body inside and outside the trim, such as body fender, rear panel, dashboard, door panels, ceiling, side liner lining, door anti-collision, handrails, windows, heat Cover, and so on. Compared to metal can be reduced by 40%, and can withstand erosion and slight collision, in the case of low-speed collision without maintenance, from the manufacturing point of view compared to metal has greater freedom of modeling to enhance, but also facilitate the integration of parts, from the pedestrian protection Consider, is also ideal material. Ford developed the LTD test car, plastic body after the lightweight aspects of the obvious results, the vehicle weight loss of up to 300kg or more. The scope of application of engineering plastics in automobiles is expanding from interior parts to exterior parts, bodywork and structural parts. The future development direction is to develop structural parts, reinforced plastic composites for exterior parts, high performance resin materials and plastics, and Will pay more attention to the recyclability of materials.
Fiber reinforced plastic is a composite fiber and plastic composite materials. Commonly used is glass fiber and thermosetting resin composite material. This kind of composite material has the advantages of small density, flexible design, easy molding, corrosion resistance, heat insulation, impact resistance, anti-vibration, easy coating, high strength, high elastic modulus, mechanical properties similar to metal materials, Under certain conditions, there is a metal sheet can not match the advantages of quality reduction and strength to achieve even more than the aluminum, while the overall cost is lower. At present in the car body has been widely used in the useful glass fiber reinforced unsaturated polyester chip molding compound (SMC) manufacturing body air deflector, the front fender and the front fender extension parts, headlamps, hood, Decorative pieces, tail plate, etc .; with the transfer molding technology (RTM) manufacturing body plate stiffeners, etc.
Carbon fiber (CFRP) is a fibrous filamentous composite material, which needs to be woven into a sheet like a woven fabric during the molding process and is wetted and cured with an organic glue. Carbon fiber reinforced polymer matrix composites have excellent toughness and tensile strength, and the quality of steel only 1/4 . Lightweight, high-strength features are required for high-performance cars, the current Ferrari, Lamborghini and other sports car body made of carbon fiber. CFRP is expected to use the car body to reduce the quality of 40% to 60%, equivalent to the quality of steel 1/3 to 1/6. However, due to the high cost of carbon fiber reinforced composites, its use in the automotive industry is limited. In order to reduce the cost of carbon fiber reinforced composites and increase the amount of carbon fiber reinforced composites, the production methods and processes of carbon fiber reinforced composites have become important research topics in the research of lightweight materials.
The textile composite material is composed of the textile structure and the matrix material. The combination of the textile technology and the modern composite material forming technology effectively overcomes the shortcomings such as the orientation of the traditional composite material and the nonuniformity of the mechanical properties and the low damage tolerance, Specific strength and specific modulus, anti-fatigue performance, in the automotive industry more and more widely. Flexible textile composite materials are mainly used in the body inside and outside the decoration and automotive pipe, strip; rigid textile composite materials can be made body parts.
4 concluding remarks
The current body material is still high strength steel, aluminum, magnesium and plastic-based. With the new materials, new technology, new technology research and development, lightweight materials and automotive product design, manufacturing process will be more closely integrated, automotive body materials will tend to multi-material lightweight design direction. Through the optimization of multi-material structure, both to improve vehicle performance, but also significantly reduce the quality. To achieve multi-material lightweight structure design, we must emphasize that “the right materials used in the right parts.
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