The key technology of automobile aluminum alloy wheel casting can be introduced from the perspective of its casting process to clarify the final application, further promote the development of technology and provide more reliable guarantee for the automobile manufacturing industry.
1. Strengthen pressure holding analysis
Pressure holding is an important stage of specific casting process, and the duration of pressure holding depends on the solidification state of the casting. If the continuous pressure can not further solidify, pressure relief treatment is required. The time at this time is related to the cavity volume, which is usually fixed. The punching pressure loading is generally linear to further improve the stability of the hub structure and increase the cost rate. However, due to the complex shape of some castings, the quality of the actual cast hub failed to meet the expected standard, and the yield was also less than 70%. Therefore, in order to effectively ensure that the casting production quality and yield can be improved, it is necessary to further analyze the pressure holding process, strengthen the analysis of temperature field and flow field, and improve the relevant process flow under the condition of ensuring the current stability.
2. Key material and aluminum alloy parameters
The most critical material of aluminum alloy casting is aluminum profile. Reasonable selection of aluminum profile and determination of final alloy ratio parameters can largely ensure the subsequent casting quality. It is also necessary to specify the casting method. On the basis of determining the method, complete the parameter design, profile selection and processing and casting according to the corresponding process. The proportion of casting main materials and auxiliary materials should be scientific and fully presented in the form of material list. In order to neutralize the soft foundation of aluminum profiles, alloy auxiliary materials with high hardness, such as magnesium (Mg), copper (Cu) or zinc (Zn), are usually selected, and the details should be determined according to the actual performance advantages of each metal material. During the process, the chemical composition and element form of aluminum alloy shall be inspected to reasonably optimize the alloy ratio and ensure the strength and mechanical properties of aluminum alloy hub.
3. Casting
Casting is one of the most critical links. It is necessary to clarify the casting dimension standard and select the correct casting method. For example, during the casting process of 16-inch aluminum alloy wheel hub, it is necessary to select according to the relevant national regulations and the Class III standard in HB963. The part acceptance standard is Class II, and the final wheel hub size acceptance should be based on the CT12 standard. The casting method shall be reasonably compared according to various casting processes, such as gravity casting, low pressure casting and forging, which have different requirements for casting, and the specific requirements shall be determined according to the actual process selection.
4. Casting dimensions
The determination of casting size of aluminum alloy wheel hub is very important, including the determination, processing and manufacturing of model size, cavity size, wall thickness and exhaust system. The casting mould for aluminum alloy wheel hub is divided into three parts: upper, lower and side moulds. Generally, the upper and lower moulds are hot-working die steel, and the side moulds are 35CrMo or QT400 die steel. The cavity size shall be determined according to the machining allowance and cooling sequence. The thickness of the upper part of the cavity shall be reasonable, and the upper and lower thickening deviation shall be less than 1mm. The casting wall thickness is the key to control the cooling intensity. For example, the final cooling part should be the middle casting mouth part, which is the thinnest hub edge part and can play a good role in cooling and solidification. In the design of exhaust system, the most important thing is the quality of exhaust slot and exhaust plug. V-shaped exhaust slot should be set around the mold core, with a depth of about 0.9 mm (the upper and lower deviation should not exceed 0.1 mm), and the spacing should be controlled within 5 mm. The design of mold core components, splitter cones, etc. should be scientific. The exhaust slot can be added by 0.4 mm, and the clearance of push rod is set between 0.1 mm and 0.2 mm, so as to ensure that the exhaust plug can work properly and ensure the exhaust effect and orderly casting.
5. Heating treatment
In the actual heating treatment of aluminum alloy, it is necessary to effectively analyze its deformation causes according to the characteristics of the alloy material, so as to take more targeted measures to prevent quenching deformation and improve the casting quality. Effectively analyze the heating process to ensure its scientificity and effectiveness. First of all, pay attention to the solution temperature to ensure the smooth development of subsequent processes. Secondly, control the cost of the alloy, effectively control the solution temperature (generally maintained at 535 ℃), maximize the alloy performance and avoid oxidation reaction caused by high temperature. Finally, the control of quenching time is the most critical. Generally, it is kept at about 30 seconds, which can avoid the problem of alloy shrinkage caused by low temperature. The quenching water temperature should be controlled at about 60 ℃ to ensure the structure and performance of the material and the quality of the alloy.