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HomeNewsWhat are the manufacturing difficulties of magnesium alloy forged wheel hubs

What are the manufacturing difficulties of magnesium alloy forged wheel hubs

2024-11-26

The Manufacturing Difficulties of Magnesium Alloy Forged Wheels

I. Aspects of Material Characteristics

Magnesium alloys are chemically active. During the high-temperature forging process, they are prone to react with the oxygen in the air. For example, when the temperature rises, magnesium atoms will quickly combine with oxygen to form magnesium oxide (MgO). The presence of magnesium oxide will form an oxide film on the surface of the magnesium alloy. If not properly controlled, this oxide film will affect the subsequent forging process. Because the oxide film is relatively loose and cannot protect the substrate as well as the oxide film on the surface of aluminum alloys, and during the forging process, the oxide film may fall off and mix into the material, leading to a decline in material properties, such as a reduction in the strength and toughness of the material.

The fluidity of magnesium alloys is different from that of other commonly used metals (such as aluminum alloys). During the forging process, the fluidity of the magnesium alloy melt has a great impact on the filling effect of the mold. Due to the poor fluidity of magnesium alloys, when filling the molds of wheels with complex shapes, it may not be able to completely fill all corners of the mold cavity, resulting in product defects, such as the formation of pores and shrinkage cavities. Moreover, its fluidity is also affected by multiple factors such as temperature and pressure, which makes it difficult to accurately control its flow behavior.

Magnesium alloys have a high tendency to hot crack during the solidification process. During the cooling stage of forging wheels, due to the high thermal conductivity of magnesium alloys, heat dissipates quickly, resulting in a large temperature gradient inside the casting. When the casting solidifies and shrinks, this temperature gradient will cause thermal stress inside the casting. If the thermal stress exceeds the strength limit of the material, hot cracks will occur. The presence of hot cracks will seriously affect the quality and safety of the wheels, making them unusable.

II. Aspects of Forging Process

The forging temperature range of magnesium alloys is relatively narrow. For example, the appropriate forging temperature interval for some magnesium alloys may be only a few tens of degrees Celsius. If the forging temperature is too low, the plasticity of the material becomes poor and the deformation resistance increases, which will make the forging process difficult to carry out, requiring higher forging pressure and being prone to cracking. On the contrary, if the temperature is too high, in addition to being prone to oxidation, it will also cause the grains of the magnesium alloy to grow, thereby reducing the mechanical properties of the material, such as strength and hardness.

Magnesium alloys are sensitive to deformation speed. During the forging process, an appropriate deformation speed is one of the key factors to ensure product quality. If the deformation speed is too fast, the dislocation movement inside the magnesium alloy cannot be coordinated in time, resulting in local stress concentration and material cracking. If the deformation speed is too slow, the production efficiency will be greatly reduced. Meanwhile, at a lower deformation speed, the magnesium alloy may also have other quality problems due to being in a high-temperature environment for a long time, such as grain growth.

Due to the need for high pressure and special temperature conditions during the forging of magnesium alloys, higher requirements are placed on molds. First of all, the molds need to have good high-temperature resistance to withstand the high temperature during the forging of magnesium alloys. Secondly, the choice of mold materials should consider the compatibility with magnesium alloys to avoid chemical reactions during the forging process. In addition, the structural design of the molds is also crucial. Because of the poor fluidity of magnesium alloys, the gate, runner and other parts of the molds need to be carefully designed to ensure that the magnesium alloys can smoothly fill the mold cavity, and the exhaust problem of the molds should be considered to prevent the formation of pores and other defects during the forging process.

III. Aspects of Quality Control

The detection of internal defects (such as tiny cracks, pores, etc.) in magnesium alloy forged wheels is relatively difficult. Compared with some other metal materials, the density of magnesium alloys is lower, requiring higher precision of detection equipment. For example, when using non-destructive testing methods (such as ultrasonic testing, X-ray testing), due to the differences in acoustic and ray absorption properties of magnesium alloys from those of other metals, special detection parameter settings and more precise equipment are needed to effectively detect internal defects. Moreover, for some tiny defects, they may not be detected due to the insufficient resolution of the detection equipment, and these defects may gradually expand during the use of the wheels, leading to potential safety hazards.

It is difficult to ensure the performance consistency of magnesium alloy forged wheels. Due to the fact that the material characteristics of magnesium alloys are affected by multiple factors (such as the purity of raw materials, forging process parameters, etc.), even under the same process conditions, the performance of different batches of magnesium alloy forged wheels may also show significant differences. For example, the mechanical properties such as strength and hardness of the material may vary due to changes in trace impurities in the raw materials or small fluctuations in temperature and pressure during the forging process, which is a great challenge for the mass production of high-quality and stable-performance wheel products.