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Ningbo Haishu YinLian Machinery Co.,Ltd

Aluminum Piston Material Requirements

(Summary description)In modern internal combustion engines, especially diesel engines, in order to greatly improve their thermal efficiency, the degree of supercharging is constantly increasing, which makes the thermal load inside the cylinder significantly increase.

Aluminum Piston Material Requirements

(Summary description)In modern internal combustion engines, especially diesel engines, in order to greatly improve their thermal efficiency, the degree of supercharging is constantly increasing, which makes the thermal load inside the cylinder significantly increase.

Information

In modern internal combustion engines, especially diesel engines, in order to greatly improve their thermal efficiency, the degree of supercharging is constantly increasing, which makes the thermal load inside the cylinder significantly increase. This makes the inherent shortcomings of aluminum alloy pistons with low thermal strength and large linear expansion coefficient more and more serious, and the application range of aluminum alloy pistons in diesel engines is obviously limited. For this reason, in some heavy-load diesel engines, cast iron pistons with higher thermal strength and wear resistance and lower coefficient of linear expansion are used. The density of cast iron is about 3 times that of aluminum alloy.

Copeland Discus type Piston

The outstanding advantage of aluminum alloy is its low density, which can greatly reduce the mass of the piston and the inertial force of reciprocating motion. Therefore, aluminum alloy pistons are often used in medium and high-speed internal combustion engines with medium and small bores, especially in automobile engines. It is much lighter than steel for the same strength. Therefore, the inertia generated by the piston made of aluminum alloy is small during the working process, which is of great significance to the vibration reduction of the high-speed internal combustion engine and the reduction of the specific mass of the internal combustion engine. In addition, when the aluminum alloy piston with lower mass moves, the side pressure and impact force on the cylinder wall are also smaller, which can reduce the friction between the piston group and the cylinder wall and the piston pin, and reduce their wear amount. Another advantage of aluminum alloy is that it has good thermal conductivity. When working, the surface temperature of the piston is lower than that of cast iron, and there is less carbon deposition on the top of the piston. There are roughly four types of aluminum piston materials that have been used so far: Al-Cu-Ni-Mg, A1-Cu-Si, eutectic A1-Si-Cu-Mg and hypereutectic AI-Si-Cu -Mg series, the first two types have long been eliminated due to the shortcomings of large linear expansion coefficient, large specific gravity and unstable volume. At present, the aluminum piston materials used in China are mainly eutectic aluminum-silicon alloys, such as ZLi08 (ZAlSil2Cu2Mg), ZLl09 ( ZAlSil2Cul MglNil). With the continuous improvement of engine performance, eutectic aluminum-silicon alloys have become more and more difficult to meet the performance requirements. In gasoline and natural gas engines, hypereutectic aluminum-silicon alloys are used more and more. The content of silicon in the hypereutectic Al-Si alloy is as high as 17%~26%, the specific gravity of the alloy is reduced, the coefficient of linear expansion is reduced, and the wear resistance and volume stability are correspondingly improved. It is an ideal piston material. This material has been widely used in piston production abroad. With the emergence of high-power and supercharged internal combustion engines, a few domestic units have begun to apply it.

However, the hypereutectic Al-Si alloy also has its shortcomings. In the hyper-eutectic Al-Si alloy that has not undergone modification treatment, there are coarse bulk primary silicon and coarse and long needle-like eutectic silicon structures, which cause the matrix to be severely split and deteriorate the mechanical properties. At the same time, the machinability is also poor, which is the main reason for the limited application of this alloy in the past. The key to solving this problem is how to modify and refine the alloy, which is the focus of research on this type of material in recent years. Another disadvantage is the reduced thermal conductivity of the piston, which has a greater impact on gasoline engines. It can be improved with proper heat treatment, but heat treatment will increase the cost of the piston.
 

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