How to solve corrosion spots during aluminum alloy cutting process?
April 17, 2023
Characteristics of aluminum alloy processing 1. Aluminum alloy has a lower melting point, and as the temperature increases, its plasticity increases. Under the action of high temperature and pressure, the cutting interface friction force is high, making it easy for the tool to stick; Especially for aluminum alloys in the annealed state, it is not easy to obtain low surface roughness. 2. Compared with steel and brass, aluminum alloy has the characteristics of soft material and poor rigidity, and low elastic modulus. These two factors significantly affect the machinability of aluminum alloy. 3. In order to obtain a smooth surface of the workpiece, a combination of rough cutting and precision cutting should be used as much as possible, as various qualified workpiece blanks will always have some oxidation layers, causing considerable wear on the tool. If the final cutting process uses polished sharp tools for fine cutting, the above requirements can be achieved.
Causes of Spot Formation in Aluminum Alloy Cutting A layer of oxide film is formed on the surface of aluminum parts to provide protection. If the oxide film is not dense, such as there is a gap in the middle of the film, or there are compounds of other elements in the film that cause cracks, or foreign chemicals that cause damage to the film, corrosive gases or media are easily invaded along this gap, causing corrosion. After corrosion, the oxide of aluminum appears in a powder like or fibrous form, which contrasts with the surrounding background color, as if it is moldy. Essentially, it is not moldy, but rather a surface oxidation phenomenon. Therefore, the essence of spots should be oxidation corrosion on the surface of aluminum parts.
Source of surface oxidation spots 1. Strong corrosive cleaning agents are used in the surface treatment process of aluminum and its alloys. During the surface treatment process of aluminum and aluminum alloys, highly corrosive industrial cleaning agents are used, causing corrosion to the substrate surface of aluminum and aluminum alloys, resulting in blackening of the aluminum surface. 2. The storage environment for aluminum and aluminum alloys is unreasonable. Aluminum and aluminum alloys are stored in environments with high temperatures, salinity, and humidity. In such environments, aluminum and aluminum alloys are prone to oxidation and blackening. 3. The cleaning of aluminum and aluminum alloy surfaces is not in place or not cleaned. After die casting and mechanical processing, the cutting fluid, release agents, other corrosive components, stains, etc. on the surface of aluminum and aluminum alloys were not thoroughly cleaned. These components remained on the surface of aluminum and aluminum alloys for a long time, resulting in mold spots and local blackening of the aluminum and aluminum alloys. 4. The treatment process design of aluminum and aluminum alloys is unreasonable. After surface treatment such as cleaning and polishing, aluminum and its alloys were not promptly treated for oxidation and passivation, resulting in corrosion, oxidation, and localized blackening of the aluminum and its alloys. Solution From the analysis of the causes of mold formation in aluminum parts, it can be concluded that the oxidation problem of aluminum parts is not caused by a single factor, but also involves multiple aspects such as internal and external factors, processes, and warehousing. At the same time, antioxidant issues need to be considered in various processes such as cleaning, machining, storage, and transportation. Any link with problems may cause mold spots to occur. Therefore, this is a comprehensive problem that requires the development of an overall solution. Some people believe that if the cutting fluid (oil) used in machining contains corrosive components to aluminum, failure to thoroughly clean after machining can cause mold spots on the surface of aluminum parts.
