First, caused by the extrusion process
In order to improve the hardness of the aluminum enclosure and maintain the stability of other mechanical properties, the aluminum profile should be taken out after extrusion, and then quenched to cool it. At this time, the selected coolant is very important and requires water or other Oily coolant, which will get a completely different effect.
If water is used for cooling, because aluminum is a chemically very active metal element, it will easily combine with oxygen in the air to form aluminum oxide (Al₂O₃), and aluminum oxide will react with other impurities or gases in the air. Chemical reaction, the generated chemical products will make the surface of aluminum profile yellow, causing surface defects, thereby affecting the appearance quality of aluminum enclosure.
If it is cooled with oil-based lubricant, the aluminum profile extruded at high temperature will not be oxidized, and the surface will be covered by the oil-based coolant, thus forming a uniform protective film layer, which will let the aluminum profile inside Performance and appearance color are extremely stable and uniform, and will not cause color difference or yellowing. However, it should be noted that the coolant must not contain water.
In order to prevent the yellowing of the surface of the aluminum enclosure and the occurrence of bubble defects, several issues should be paid attention to during extrusion:
1. Control the temperature and extrusion speed of the extrusion equipment.
2. Use the correct coolant and cooling method.
3. Keep the inside of the extrusion barrel clean and dry. If the size of the extrusion tool is deviated, check and repair it in time.
4. When extruding different alloys, the extrusion barrel should be completely removed to prevent the mixing of different alloy materials, which may cause color difference.
5. Regularly check the extrusion equipment, check whether the various index parameters are within the normal working range, and strictly follow the process standard.
Second, the surface treatment process caused
The oxide film on the surface of the extruded aluminum enclosure is very thin and soft, its performance is also unstable, and the corrosion resistance is not strong. It needs to be anodized to form a dense oxide film on the surface of the aluminum profile, thereby enhancing the aluminum profile Mechanical properties and appearance properties. Before the anodizing treatment, the surface pretreatment must be performed first to remove the oil stains and oxide film on the surface of the profile, especially when washing thoroughly, so as not to affect the later anodization and the oxide film can not be well colored.
There are many surface treatment methods, such as anodizing, electrophoretic coating and electrostatic powder spraying. When dealing with various surfaces, there are many details that need to be paid attention to. Any mistake in any link may cause different defects on the surface of the aluminum profile. For example, when anodic oxidation, pay attention to the pH value, neutralizer and various parameters of the bath solution during pickling, alkali cleaning and acid-base neutralization are within the specified range, and wash thoroughly when washing. Otherwise it is easy to cause the surface of the aluminum profile to turn yellow.
