In the production of motor aluminum alloy end covers, porosity is a common and critical issue affecting product quality. Porosity not only reduces the mechanical properties of the motor aluminum alloy end cover, such as strength and toughness, but can also affect its sealing performance and appearance, thus adversely impacting the overall performance and lifespan of the motor. Therefore, taking effective measures to avoid porosity is crucial.
From the perspective of raw materials, the quality of the aluminum alloy raw materials used in the production of motor aluminum alloy end covers is one of the important factors affecting porosity. Reliable and uniformly composed aluminum alloy raw materials should be selected, avoiding the use of raw materials containing excessive impurities and gases. During the raw material procurement process, strict quality control is essential, with detailed inspection and testing of each batch of raw materials to ensure they meet production requirements. Simultaneously, during raw material storage, attention should be paid to moisture and oxidation prevention to prevent the raw materials from absorbing moisture and oxygen during storage, which would generate more gas during the melting process.
Controlling the melting process plays a key role in avoiding porosity defects in motor aluminum alloy end covers. During the melting process, the melting temperature and time must be reasonably controlled. Excessively high melting temperatures lead to increased gas absorption in the molten aluminum alloy, while excessively low temperatures reduce its fluidity, hindering gas expulsion. Therefore, it is crucial to determine the appropriate melting temperature range based on the type and properties of the aluminum alloy and strictly control the melting time to avoid prolonged high-temperature melting. Furthermore, effective degassing measures should be employed during the melting process, such as introducing inert gas or using degassing agents, to remove gases from the molten aluminum alloy. Introducing inert gas creates bubbles in the molten aluminum alloy, carrying the gas to the surface; degassing agents remove gases through chemical reactions, thus achieving the degassing purpose.
Mold design is also a significant factor affecting porosity defects in motor aluminum alloy end covers. A well-designed mold can improve the filling process of the molten aluminum alloy, facilitating gas expulsion. When designing the mold, the fluidity of the molten aluminum alloy and venting requirements should be fully considered, and the gating and venting systems should be rationally designed. The gating system design should ensure that the molten aluminum alloy fills the cavity smoothly and evenly, avoiding turbulence and jetting phenomena, thereby reducing gas entrapment. The design of the venting system must ensure that gas can be smoothly discharged from the mold, preventing gas accumulation and the formation of pores within the cavity. Venting structures such as venting grooves and plugs can be incorporated into the mold to increase gas discharge channels.
The setting of die-casting process parameters also significantly affects the occurrence of porosity defects in motor aluminum alloy end covers. Process parameters such as injection speed, injection pressure, and holding time need to be adjusted appropriately. Excessive injection speed will cause turbulence in the molten aluminum alloy, entraining a large amount of gas; insufficient injection speed will lead to inadequate filling of the cavity by the molten aluminum alloy, resulting in defects such as cold shuts. Insufficient injection pressure will fail to fully compact the molten aluminum alloy, easily leaving pores inside the product; while insufficient holding time will prevent the molten aluminum alloy from fully compressing during solidification, leading to pore formation. Therefore, the optimal die-casting process parameters need to be determined through experimentation and experience based on the product's structure and dimensions.
Operating procedures during production are equally crucial. Operators should strictly follow operating procedures to avoid the formation of porosity defects due to improper operation. For example, during mold installation and debugging, it is crucial to ensure good mold sealing to prevent leakage of molten aluminum alloy and gas entry into the mold cavity. During die casting, residues on the mold surface must be cleaned promptly to avoid affecting the filling of the molten aluminum alloy and the venting of gas.
Post-processing steps also have a certain effect on improving porosity defects in motor aluminum alloy end covers. For minor porosity defects, repair can be achieved through post-processing methods such as heat treatment and impregnation. Heat treatment can improve the microstructure of the aluminum alloy and increase its density; impregnation fills the pores with an impregnating agent, improving the product's sealing and strength. Through these post-processing steps, the impact of porosity defects on product quality can be effectively reduced.
