Brief discussion on the development trend of lightweight automobile materials

With the rapid development of science and technology, great changes have taken place in the composition of modern automobile manufacturing materials. The proportion of high-density materials has decreased while the proportion of low-density materials has increased significantly. It can be said that since the 1990s, automobile materials have developed to the direction of lightweight, resource-saving, high-performance and high-function. This paper will focus on the development trend of automotive material lightweight.

First, automobile lightweight has become the development direction of automobile materials

With the rapid development of automobile industry, automobile material lightweight has become the inevitable trend of automobile development. Lightweight can not only reduce the body quality, save energy, reduce fuel consumption, reduce pollution, but also reduce costs, improve enterprise competitiveness, increase enterprise profits. The relevant information shows: the general quality of the car parts each reduce 1%, can save 1% fuel; For every 1% reduction in moving parts, fuel savings can be 2%. In recent years, automobile manufacturers all over the world are committed to exploring and applying new automobile materials to reduce the quality of automobiles on the premise of ensuring the comprehensive performance of automobiles. Therefore, automotive lightweight has become the main direction of automotive material development.

No matter from the quantity, quality or from the technical requirements of automobile parts, the use of metal materials in the automobile has a very important position. Although the number of non-metallic materials is increasing year by year, metal materials still occupy a high proportion in the usage, and the proportion of traditional automobile materials such as steel and iron is still relatively high.

One of the important means of automobile lightweight is to ensure the comprehensive performance of automobile, automobile materials to light materials, including aluminum alloy materials, high-strength steel, magnesium alloy materials, titanium alloy materials, plastics and composite materials.

Second, the application of lightweight materials in automobiles

1. Aluminum alloy

Aluminum relative to steel, iron, the quality of many light, and aluminum resources are rich, the market supply is sufficient. After adding alloy elements, aluminum has the characteristics of low density, light weight, high thermal conductivity, strong shock absorption ability, easy recovery and regeneration, and high corrosion resistance. The density of aluminum alloy is about 1/3 of steel, the ability to absorb impact is about 2 times that of steel, thermal conductivity is about 3 times higher than iron, so aluminum alloy is the preferred material for automobile lightweight, used earlier in the automobile, the technology is relatively mature. In the 1980s, the average amount of aluminum used in cars in the United States was 55kg, and in the 1990s it reached 130kg. Japan has made rapid progress in the use of aluminum alloy materials in automobiles. The most aluminum alloy is used in sports cars, which is up to 250kg per vehicle, accounting for 16.4% of the vehicle mass. The application of aluminum alloy in automobiles is mainly as follows:

Cast aluminum alloy. Casting aluminum alloy has excellent casting performance, casting methods are many, according to the purpose of use, parts shape, quantity, quality standards, mechanical properties and other requirements and economic benefits, choose the most appropriate alloy and casting method, the production efficiency is relatively high. Casting aluminum alloy is mainly used in automobile engine parts, clutch housing, transmission housing, rear axle housing, steering gear housing, timing gear housing and other housing parts; Can also be used to manufacture bumper, wheel, engine frame, steering knuckle hydraulic pump assembly, brake pliers and other parts.

Deformed aluminum alloy. Compared with cast aluminum alloy, deformation aluminum alloy has superior strength and toughness. Deformable aluminum alloy is mainly used in the manufacture of bumper, engine hood, brake assembly protective cover, muffler cover, anti-lock braking system, heat exchanger, body frame, seat, car bottom plate and other parts. The proportion of deformed aluminum alloy in American cars is higher.

Forged aluminum alloy. Because of the high price, forged aluminum alloy in the past only in Europe and the United States limousine has a small number of applications. Because the hot forging aluminum alloy is not oxidized, the surface is smooth, the machining allowance is small, no processing defects, so the application in the automobile is gradually increasing, mainly used in the automobile bracket and truck wheels.

2. High strength steel

Steel is still the main material for automobile manufacturing, although light materials such as aluminum are increasing. Light materials such as aluminum can only replace part of steel in automobile manufacturing due to their properties, process requirements and price constraints. Compared with ordinary steel, high strength steel has the characteristics of high strength, light weight, low cost, and can improve the safety performance, so high strength steel has become a very competitive automotive material lightweight raw material. By using high strength steel plate instead of ordinary steel plate to manufacture automobile body, the quality of automobile itself can be reduced by 30% ~ 40%. Instead of ordinary steel transmission shaft mass can be reduced by about 10%. The PNGV-Class sedan, developed in North America, has an all-strength steel body with a mass of only 218kg, comparable to an all-aluminum body. So high strength steel is one of the main development directions of automobile steel materials in the future. At present, automobile manufacturers use high-strength steel to replace ordinary steel and cast iron in automobile body, chassis, suspension, steering and other auto parts, which is not only conducive to the realization of automobile lightweight, reduce energy consumption and protect the environment, but also can greatly improve the corrosion resistance of vehicles, increase the service life of vehicles.

3. Magnesium Alloy

There are more than 60 known magnesite-containing minerals in the world. Magnesium is the lightest metal among the materials used in industry at present, and it is also one of the elements abundant in the earth's crust. Magnesium alloy has the characteristics of low density, high specific strength and stiffness, good dimensional stability, good thermal and conductive performance, vibration absorption, and easy processing and forming, so it is one of the competitive lightweight materials for automobile. Magnesium alloys have been used in cars for at least 60 years. Louris Chevrolet first used magnesium alloy as a piston on a racing car back in 1930. In 1990, Japan and other countries also used magnesium alloy in automobile die casting. From the number of magnesium alloy parts used in automobiles, the average consumption is not high, far less than aluminum alloy. However, the application of magnesium alloy in automobile has been increasing rapidly in recent years. At present, most of the parts made of magnesium alloy in automobile are die-cast parts. Among all die-cast alloys, magnesium alloy die-cast parts are the lightest and have a longer service life than aluminum alloy. Magnesium alloy die casting mainly produces automobile instrument panel, seat skeleton, transmission shell, steering wheel control system components, engine parts, door frame, hub, bracket, clutch shell, body bracket, etc.

4. Titanium alloy

Titanium alloy is a new type of material, it has excellent comprehensive properties, low density, high specific strength and specific fracture toughness, low temperature toughness, fatigue strength and crack growth resistance ability. Titanium can reduce the quality of automobile engine, improve vehicle speed, reduce noise, reduce average fuel consumption, and has great advantages in improving engine performance. In addition, engine valves made of titanium alloy are 15 to 20 percent lighter than steel valves. So titanium alloy has become the material considered for automotive lightweight. The Japanese used titanium in engine parts for racing cars in 1968. At present, titanium alloy is mainly used in the manufacture of engine parts and body parts, while also considering the use of titanium alloy in the manufacture of automotive engine valve, valve spring, valve seat ring and connecting rod, exhaust pipe, wheels, high strength parts, etc. Although the application prospect of titanium is very broad, but the disadvantages of titanium are high cost, poor machining performance, cutting, welding and surface treatment are difficult.

Step 5: Plastic

Plastics and their composites can not only reduce the mass of parts by about 40%, but also reduce the cost by about 40%. According to relevant statistics, in 2000, the world's average plastic consumption on each vehicle has reached 105kg, accounting for about 8%-12% of the total mass of the vehicle. Plastic parts began to be used in the automobile field in the 1950s. In 1959, Ford first applied PVC sol to the automobile manufacturing industry. In recent years, the increase in the amount of plastic used in cars has continued, and the growth rate is very fast. The main applications of plastics in automobiles are as follows:

Plastic interior trim. The plastic instrument panel is the main interior trim. Due to the high surface temperature of the instrument panel, in order to adapt to the high temperature of the engine room and the sunlight, it is required that the plastic instrument panel does not deform at high temperature, and can withstand relatively large impact at low temperature. Common plastic interior parts are utility boxes, door handles, seats, ceilings, antifreeze boards, door handles, drainage boards, brackets, steering column sheathing, decorative boards, air conditioning system accessories, etc.

Plastic trim. The auto body parts are the exterior parts of the car with more plastic application: for example, the plastic bumper, the thermoplastic alloy to make the car fender, the PC coated with hard film to make the headlights of the car lighting system, the injection molding method to make the side collision strip, the plastic substrate board with the foam plastic layer to make the car roof material, etc. Other plastic exterior trim parts include radiator grille, wheel guards, sills, side moulded parts, rear deflector, choke plate, rear view mirror frame, door handles, rear trim baffle and plastic window glass.

Plastic functional parts. It mainly refers to the engine components and the fuel intake system under the hood and the electrical system. While plastic engine parts are cheaper, lighter, and less noisy than metal parts, plastic parts must be able to withstand temperatures up to 175℉, have high rigidity, dimensional stability, and resist corrosion. Therefore, the main plastics used in engine parts are nylon 66, PPS, polyester, etc. So far, Rogcrs has made engine cylinders and oil pans out of fiberglass reinforced phenolic; BMW's new six - and four-cylinder engines use all-plastic intake; Mann&Hummel manufactures the intake device using 35% glass fiber reinforced nylon. Plastic functional parts also include fuel tank, steering wheel, window glass, windshield wiper, oil pipe, power valve, automotive window lift device and cylinder head cover.

6. Composite materials

Composite material is a material with strong vitality emerging in the development of modern science and technology. It is composed of matrix materials (including resin, metal, ceramics, etc.) and reinforcing agents (including fibers, whiskers, particles, etc.). It has high stiffness, high strength, heat resistance, wear resistance, light weight and other characteristics, can meet a variety of special uses, so it is also one of the selection of automotive lightweight materials. The mechanical properties and functions of composite materials can be obtained by proper material selection and optimal design according to actual needs. At present, the main applications of composite materials in automobile are metal matrix composites, ceramic matrix composites and polymer matrix composites.

Metal matrix composites. The most typical metal matrix composites are aluminum matrix composites. Aluminum material is a traditional and typical lightweight material, which has been widely used in automobiles. The composite material made of aluminum as matrix and the addition of needle-like reinforcing agent has the characteristics of wear resistance and high temperature resistance, etc. It is mainly used in automobile piston, cylinder liner, brake wheel, transmission shaft and tire bolt.

Ceramic matrix composites. Ceramic composite material made of ceramic matrix and reinforced agent has excellent mechanical properties and low density, so it is also used in automotive materials, but the price is much higher than that of metal parts. At present, all countries in the world are vigorously developing ceramic matrix composite materials, which are mainly used in the manufacture of automobile engine valve, tappet, turbocharger turbine, cylinder head, piston pin and exhaust pipe.

Polymer matrix composites. Polymer matrix composites are mainly glass fiber reinforced plastics, also known as glass steel, which can be used on the body instead of steel plate to achieve lightweight body.

Three, the development of automotive material lightweight problems to pay attention to

1. The lightweight of automobile materials should be scientific and rigorous, and improve safety awareness

The lightweight of automobile materials should not be carried out blindly. Only under the premise that the overall performance of the automobile is not affected can the quality of parts be reduced to the maximum extent. At the same time, the use of lightweight materials should first consider whether the application of materials can ensure the safety of the vehicle, which is a prerequisite for the lightweight of automotive materials.

2. Deal with the relationship between the lightweight of automobile materials and the increase of automobile configuration

As cars tend to be fast, advanced, luxurious, comfortable and safe, all kinds of accessory devices are used in large numbers, so that the total mass of cars has been greatly increased. On the one hand to increase the car configuration, on the other hand to carry out lightweight automotive materials, this is a very difficult to solve the problem. Therefore, the car lightweight, under the premise of ensuring driving stability, to reduce the use of low related car configuration, so as to achieve the purpose of car lightweight.

3. Handle the relationship between automotive material lightweight and raw material resources and cost

If the selection of low resources, high cost of lightweight raw materials, will inevitably increase the cost of the vehicle. Therefore, in the selection of raw materials, we must pay attention to the selection of materials with low cost and more resources, so as to achieve the purpose of improving the lightweight of automobile materials and reducing the manufacturing cost of automobile.

4. Develop lightweight specifications and standards for automotive materials

At present, there is no unified standard for automobile lightweight, which hindering the development of automobile lightweight. Therefore, it is hoped that the automobile management department can formulate technical standards and detection methods for automobile material lightweight.

5. Establishment of automotive material lightweight technical personnel training base and technical consulting service institutions

Talents are the foundation of an enterprise. Only by establishing the necessary training base and cultivating talents in this field can the lightweight of automobile materials be carried out scientifically. It is also very necessary to add technical consulting service institutions in this field.

To sum up, automotive material lightweight is the general trend, the world is committed to the research and development of automotive material lightweight. However, automobile manufacturers should not blindly follow the trend in automobile material lightweight, must be scientific and reasonable. The development of lightweight automobile materials in our country is behind the European and American countries, at present is in the stage of development, so the prospect of development is broad. Chinese automobile enterprises should seize the opportunity and vigorously develop automobile lightweight to contribute to the leapfrog development of China's automobile industry.

-- Content reprinted from Automotive Industry Research