Aluminum Casting at home and abroad in the Automobile Industry

Use of aluminum instead of cast iron to produce auto parts can be traced back the history of the 20th century, 40 years. At that time a small number of auto plants in Europe, such as Italy¡¯s Fiat developed the aluminum intake manifold and cylinder head, and began a small amount of production. 50 years in Australia to introduce a British company¡¯s low-pressure casting technology to produce automotive aluminum castings. At the same time, the former West Germany, a company of low-pressure casting technology was further improved to produce a structurally complex aluminum parts. U.S. General Motors Corporation began mass production of cars aluminum castings, such as air-cooled cylinder head, crankcase, engine rear cover and so on. 60 years, due to the high-pressure die-casting technology, with aluminum-based light metals in automotive application increased significantly, laid the extensive use of aluminum castings in modern automobile industry to reduce vehicle weight basis. The past 20 years, the world automobile industry in the application of Aluminum casting is increasing, according to statistics, the world¡¯s total production of aluminum castings by more than 3% per year rate of growth in the total production of aluminum castings, about 60% -- 70% of the aluminum castings used in automobile manufacturing, have made the world production and application of aluminum casting and the automotive industry¡¯s development, creating a close contact. Automotive Applications of Aluminum Casting And Japan¡¯s most prominent development. In the early 70s, many of Japan¡¯s auto companies and expand the application of aluminum in the automotive engine research, have been widely used to produce aluminum casting instead of cast iron intake manifold, cylinder head, and began a small production of aluminum engine. In recent years, the development of aluminum castings and plastic applications, Japan has been at the world advanced level, the Japanese cars are known for their compact, comfortable, light weight, the economy is good and safe and reliable and occupy the U.S. and European markets.

Aluminum alloy material in the application of domestic vehicles is also low, China and Europe and the United States, Japan and other developed countries are lagging far behind, so the expansion of China¡¯s automobile industry research and application of aluminum there is still great potential to be tapped.

A typical automotive castings and casting process

1. Cylinder Block

Is the heart of the engine cylinder block, so the casting quality is critical, control can prevent or reduce the car "hit the heart of" danger. The engine cylinder block is the largest and most complex parts. Use of aluminum instead of cast iron cylinder block of the biggest advantage is able to greatly reduce the weight of the engine.

Early aluminum cylinder block generally use the low-pressure casting process and metal casting process, but also a small amount of used sand casting process. From the trend of recent years, most manufacturers to adopt high-pressure die-casting process. Domestic aluminum alloy cylinder block casting method is still using low-pressure casting process. In the past a very long period of time, the aluminum cylinder block is not as aluminum cylinder heads, as has been widely adopted because of the cost of aluminum cylinder block cast iron cylinder block than the high cost, and the commonly used aluminum alloy material in a certain some performance aspects (such as wear-resistance) is not as good cast iron. However, with the energy demand and environmental requirements led to the pursuit of lighter vehicles, as a concept, people started to realize the use of aluminum instead of cast iron cylinder block is an inevitable trend. Meanwhile, the aluminum alloy materials research and manufacturing technology has been steadily progressing, a group of high performance aluminum alloy used in the production started. On the other hand, aluminum casting manufacturing technology advances enable high-volume production cost of aluminum cylinder block has also been declining. At present the application of cast aluminum cylinder block has been very wide application in modern cars has reached a universal stage.

Although China¡¯s automotive casting industry is still unable to reach the international advanced level, but also the construction of a number of well-known foundry, but for some commonly used automotive castings, such as the cylinder block and cylinder head, China is still mainly rely on imports. China cylinder block production yet to be fully made, though some of the major manufacturers have built a large cast of the die-casting production lines, and the development of aluminum castings.

2. Cylinder Head

Modern design of the car engine cylinder heads are manufactured using aluminum alloy. The cylinder head is both complex and importance of casting parts, the combustion chamber, the engine¡¯s intake manifold and exhaust pipes are installed inside the cylinder head. In the engine cylinder head is in a high-temperature mode of operation to bear a greater thermal shock and would result in stress concentration, therefore, aluminum has become a popular product. Manufactured using aluminum alloy cylinder head of the advantages of light weight, in addition, there is another outstanding advantage of excellent thermal conductivity. For cars, light motor vehicles, the use of aluminum cylinder head allows the engine thermal efficiency is better to avoid the combustion chamber within the cylinder head overheating of the parts produced. As the cylinder head is a complex structure cavity, wall thickness also uneven casting, and the cylinder head cavity there is pressure sealing requirements, to the casting process to bring certain difficulties. Traditionally, multi-cast aluminum cylinder head casting process using metal type and low-pressure casting process, since the 80¡¯s there were two new casting technology - gasification of low-pressure die casting and sand casting, particularly the former, it is suitable for cylinder head , into the tracheal lumen is complex and needs of these core molding sand casting. The process as compared with the traditional craft has many advantages: regardless of type, can not afford to die, do not use sand core, casting easy to clean, a good casting surface finish, size and high precision, suitable for mass production.

Cylinder head casting is the traditional end of injection, which is conducive to the aluminum melt evenly fill the mold, while the top note is now widely used in China as it will give shape casting and more conducive to better direct solidification cooling. The vast majority of Chinese manufacturers of aluminum cylinder head using low-pressure casting process, because it can improve the microstructure and mechanical properties.

3. Piston

Automobile piston engine combustion chamber in one of the main components of their wall to accommodate the piston rings, as opposed to the formation of sealing the inside of the cylinder. Piston engine of the vehicle¡¯s energy plays a decisive role. While the piston material requirements are: a relatively low density, good thermal conductivity, thermal expansion coefficient is small, adequate high-temperature strength and dimensional stability, etc., and therefore they are primarily aluminum alloy or fiber-reinforced composite materials. Cast aluminum alloy can meet most of the above requirements, in particular, widely used abroad (and the country will also have been used) high silicon hypereutectic aluminum alloy pistons to better meet these requirements. At present almost 100% with the car engine piston aluminum alloy, aluminum piston molding process is mainly used in gravity die casting, low pressure casting and liquid die forging (also known as squeeze casting). Liquid die forging is a reference to pressure casting and forging process and developed a new metal forming technology, with this process of production of aluminum alloy pistons in the mechanical properties, microstructure and casting dense in terms of both superior to the traditional metal-based casting.

4. Shell Parts

Aluminum Shell Parts including gearbox shell. Clutch shell, shell oil pump, rocker cover, gear cover, the main brake cylinder shell and so on. These parts are almost always produced by using high-pressure die-casting process, using this process is the production of aluminum casting organizations, dense, good mechanical properties, surface smooth, dimensional precision machining allowance, compared with metal casting process and a small low-pressure casting process, although this process is Tooling costs are relatively high due to high productivity, aluminum castings for the automotive mass production, the total cost is not high relative terms. Gear box shell is typical of large complex castings, which require very thin wall thickness, most foundries use of die-casting technology to produce, in order to improve the quality of the casting, but also use some other methods, such as low-speed die-casting, double - Pressure - Injection molding and vacuum casting stamping.

5. Intake Manifold

Into the pore structure due to irregular cross-section, their production automobile intake manifold is always very difficult. Engine technical needs of electronic injection and injection into the trachea more complex production technology, which is why the EPC technology, more and more popular by the people¡¯s causes. In terms of the intake manifold, big trucks usually sand casting of gray cast iron components, while private cars are more like the aluminum alloy components. The vast majority of production methods are used casting process, including the EPC, gravity die casting and pressure die-casting.

6. Wheel

The wheel is a demanding security components. From a cost perspective to consider, at present is still relatively cheap steel wheels, which is currently used more steel wheels, one of the reasons. With the lightweight car product trends and the overall structure of the development trend of more and more people recognized the application of aluminum alloy wheels are also expanding as aluminum wheels with light weight, can reduce the vibration and beautiful shape and so on. According to tests, alloy wheels and steel wheels compared to the weight of the former reduces 30% ~ 40%, the vibration can be reduced by 10% -15%. Aluminum alloy wheel casting methods are mainly metallic casting, low pressure casting, pressure casting and centrifugal casting.

The prospect of China¡¯s automobile aluminum castings

At present China¡¯s automobile industry used in the aluminum parts is also relatively small, which is the development of China¡¯s automobile industry, especially with the current situation of the development of production cars is very co-ordination, therefore, speed up the aluminum alloy material in Chinese-made cars in the research, development and application of great significance. China¡¯s automobile aluminum castings are facing a global energy recovery, environmental protection and more demand for the challenges of a large number of private cars, while the aluminum castings will be more suited to the future of these trends, and to meet the growing needs:

First, the modern car is toward safety, energy saving, environmental protection and direction, while the car is a lightweight energy conservation, fuel-efficient and reduce pollution, one of the most effective ways. Aluminum castings to a large extent reduce the car¡¯s own weight, aluminum alloy as a typical lightweight materials used to make the advantages of auto parts has become increasingly recognized by people, and therefore non-ferrous castings from a more lightweight aluminum castings by instead has become a trend.

Secondly, the casting accuracy to produce a thin-walled structures, so that we can achieve close to finished aluminum casting shape, thus simplifying the production process. China has also developed a new casting technology, in the CAM numerical control processing based on the use of 3D CAD in casting technology, the production of new casting products.

Third, the excellent hardness and toughness help to ensure casting quality, thus enhancing the car¡¯s features. In the past these with casting compared to the size and size are not attractive enough. The quality of raw and auxiliary materials, smelting technology, casting process itself, casting equipment, temperature and so affect a large extent on the quality of the casting, and therefore strict control and supervision. Our foundry casting to more emphasis on the internal structure.

Fourth, the traditional liquid is converted to semi-solid die-casting to the die-casting process has injected new vitality, and combination of solid and liquid die casting advantages. China¡¯s casting companies casting process should be greater use of these fine technologies to bring these different technologies together can greatly enhance the quality of aluminum castings and broaden their applications.

Fifth, given China¡¯s demand for automotive aluminum castings annually increasing at a rate of 10%, some foreign companies have also taken a number of ways to grasp the aluminum foundry industry¡¯s market share is expected that this trend will become increasingly prominent in the future. A number of international auto accessories manufacturer has stepped up its investment in China to open centralized production to meet local needs.

Sixth, in addition to China is a participant in the global automotive foundry industry, China is still a low value-added products (such as brake components) suppliers. Chinese production of cylinder block and cylinder head has not yet been widely recognized by the international market, so Chinese manufacturers must continuously improve casting technology opened to improve product value-added. Only through the use of advanced technology to process casting products, China will gradually enter the auto accessories market for OEMs to open in the true sense, competitive.