Manufacturing Process of Aluminum Alloy Forged Wheels

1. Preparation of Raw Materials

• Selection of Aluminum Alloy Materials: Aluminum alloy forged wheels usually adopt high-strength aluminum alloys, such as 6061 or 7075 aluminum alloys. The 6061 aluminum alloy has good machinability, corrosion resistance, and moderate strength, which is suitable for general high-performance wheels. The 7075 aluminum alloy has even higher strength, approaching that of many steels, but it is slightly more difficult to process. These aluminum alloy materials are purchased in the form of aluminum ingots, and the purity and quality of the aluminum ingots have a crucial impact on the final performance of the wheels.
• Material Inspection: Before use, the aluminum ingots need to be subjected to strict inspection. The inspection contents include chemical composition analysis to ensure that the contents of main alloy elements such as aluminum, magnesium, and silicon meet the standards. At the same time, the internal defects of the materials, such as pores and inclusions, also need to be checked. Ultrasonic flaw detection, radiographic flaw detection, and other means are used to guarantee the quality of the materials.

2. Forging Process

• Heating Treatment: Firstly, the aluminum ingots are heated to an appropriate forging temperature range, generally between 400 - 500 degrees Celsius. This temperature range enables the aluminum alloy materials to have good plasticity, facilitating subsequent forging processing. The heating process requires precise control of the temperature because if the temperature is too high, it may lead to overheating of the materials and grain growth, affecting the mechanical properties of the wheels; if the temperature is too low, the deformation resistance of the materials will increase, increasing the forging difficulty and even possibly resulting in forging defects.
• Initial Forging (Upsetting): The heated aluminum ingots are placed in the molds of the forging equipment for the initial forging, mainly the upsetting operation. Through the application of huge pressure by the press, the aluminum ingots are compressed in the axial direction in the molds, increasing their diameter and decreasing their height. This step can initially improve the organizational structure of the materials, making them more compact and laying the foundation for subsequent forming forging.
• Forming Forging: After upsetting, the forming forging is carried out. The billets that have undergone the initial forging are placed in the molds with the shape of the wheels, and through multiple stamping or die forging operations, the billets are gradually formed into the basic shape of the wheels. In this process, the design and precision of the molds are of vital importance. The cavity of the molds needs to be precisely machined according to the specific design requirements of the wheels, including the shape of the spokes and the size of the rims. During the forging process, the magnitude and direction of the pressure, the forging speed, and other parameters also need to be strictly controlled to ensure the dimensional accuracy and surface quality of the wheels.

3. Machining

• Turning Processing: The forged wheel blanks need to be subjected to turning processing to achieve precise dimensions and good surface finish. On the lathe, various cutting tools are used to turn the rims, spokes, and other parts of the wheels. For example, for the rim part, the precise dimensions for installing tires need to be turned to ensure a tight fit between the tires and the wheels; for the spokes part, the shape and thickness required by the design need to be turned. During the turning process, the selection of cutting parameters (such as cutting speed, feed rate, cutting depth) needs to be optimized according to the characteristics of the aluminum alloy materials and the machining accuracy requirements of the wheels to ensure the machining quality and improve the machining efficiency.
• Drilling and Milling: In order to install valve stems, bolts, and other components, drilling operations need to be carried out on the wheels. The positional accuracy and hole diameter accuracy of the drilling are very high, and usually, CNC drilling machines are used to complete it. In addition, for some complex spoke shapes or decorative surface textures, milling processing is also required. Milling can process various exquisite patterns or shapes on the surface of the wheels, increasing the aesthetics of the wheels.

4. Surface Treatment

• Cleaning and Pretreatment: Before surface treatment, the wheels need to be cleaned to remove impurities such as oil stains and metal chips left over from the machining process. After cleaning, pretreatment is carried out, such as chemical etching or anodic oxidation pretreatment. Chemical etching can make the wheel surface form a microscopic rough structure, increasing the adhesion of subsequent coatings; anodic oxidation pretreatment can form a dense oxide film on the wheel surface, improving its corrosion resistance.
• Painting or Electroplating: According to customer requirements and design requirements, the wheels can be painted or electroplated. Painting can provide a rich variety of color choices and can protect the wheel surface from corrosion and wear. During the painting process, primer painting is first carried out. The primer can enhance the bonding force between the coating and the wheel substrate; then the topcoat is painted, and the topcoat can provide a beautiful appearance and the required glossiness. Electroplating treatment is mainly used to obtain a metallic appearance effect, such as chrome plating, nickel plating, etc. The electroplating layer not only has good decorative properties but also can improve the corrosion resistance of the wheels to a certain extent.

5. Quality Inspection

• Dimensional Accuracy Inspection: Precision measuring equipment such as coordinate measuring machines is used to detect the various dimensions of the wheels, including the rim diameter, spoke thickness, and wheel width. Ensure that these dimensions meet the requirements of the design drawings, and the tolerances are controlled within the specified ranges. Any dimensional deviation may lead to compatibility problems between the wheels and the vehicles, affecting the driving safety of the vehicles.
• Mechanical Property Inspection: Mechanical property tests are carried out on the wheels, such as tensile tests, impact tests, and fatigue tests. The tensile test can detect the strength and ductility of the wheel materials; the impact test is used to evaluate the anti-destruction ability of the wheels when subjected to sudden impact forces; the fatigue test simulates the stress situation of the wheels during long-term use and checks whether there will be fatigue cracks and other defects. Only by passing these strict mechanical property inspections can the safety and reliability of the wheels in actual use be guaranteed.
• Appearance Quality Inspection: A comprehensive inspection of the appearance of the wheels is carried out, including surface flatness, coating quality, whether there are scratches or blemishes, etc. Surface flatness directly affects the aesthetics of the wheels and the aerodynamic performance during driving; coating quality is related to the corrosion resistance and appearance durability of the wheels; scratches or blemishes may become the starting points of corrosion, reducing the lifespan of the wheels.