[China Aluminum Network] The sprocket is a crucial component of the bicycle crank assembly. Its manufacturing process includes: material cutting, blanking, punching the center hole, forming, cutting the teeth, shaping the molars, punching 25 precise holes, and finally, solution treatment.
The solution treatment process requires a temperature range of 495 to 503°C, with a holding time of 15 to 20 minutes, and uses water at 25 to 35°C as the cooling medium. After stamping, the flatness of the sprocket meets the design specifications. However, after solution treatment, the flatness exceeds the allowable limits. To address this, the sprocket is mounted on a special fixture using bolts and pressure plates before the treatment. After the process, the bolts and pressure plates are removed, and the sprocket is taken out from the fixture. Despite this, the flatness still does not meet the required standards.
Using water as a quenching medium offers several advantages, such as simplicity, low cost, and fast cooling, which ensures the mechanical properties of aluminum alloys. However, from the perspective of minimizing deformation, water may not be the best choice. Its rapid cooling can create significant temperature differences between the surface and core of the part, especially in areas with varying thicknesses, leading to internal stresses. At high temperatures, aluminum alloys are soft and prone to distortion, while at lower temperatures, these stresses can cause cracks. In industry, to reduce deformation, methods like increasing the water temperature, oil quenching, isothermal quenching, or using polymer-based media are often employed. Oil quenching, however, requires an extra degreasing step, and isothermal quenching involves more complex procedures. Polymer quenchants offer flexibility in adjusting cooling rates by changing the concentration. Low-concentration solutions cool quickly, similar to cold water, while higher concentrations slow down the cooling rate, approaching that of oil or hot water. Although effective, polymer solutions are more expensive and harder to manage compared to water.
Based on the above analysis, it was decided to use 100°C hot water as the quenching medium. Following the updated solution treatment process—temperature 495–503°C, holding time 15–20 minutes—the flatness of the sprocket was reduced to less than 0.26 mm, meeting the required specifications. This adjustment significantly improved the quality and consistency of the final product, ensuring compliance with design standards and reducing rework. By optimizing the quenching method, the production process became more efficient and reliable, supporting better overall performance of the sprocket in its intended application.
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Kaiping Jenor Sanitary Ware Co., Ltd , https://www.jenorsanitary.com