Improvement of the pressure riveting process of water temperature sensor housing

A few years ago, during the manufacturing of the water temperature sensor, frequent cracking and deformation of the housing became a major issue that was difficult to completely resolve. The primary cause of these cracks was the low elongation of the material used for the housing. When the elongation of the material fell below the minimum standard, cracks would occur in various sizes and proportions during the extrusion process. To address this problem, improving the material properties or annealing the housing with poor elongation was typically considered. However, these methods had their own limitations, such as surface discoloration and reduced structural integrity after annealing, which affected both aesthetics and functionality. In this paper, through multiple rounds of testing and verification, an alternative solution was proposed: modifying the riveting process. By altering the flange structure and the shape of the end button, the design of the housing was adjusted to reduce stress concentration and improve the overall structural integrity. This new approach opened up a fresh way to prevent cracking and deformation in the water temperature sensor housing. Currently, the sensor housing is made from Y15 free-cutting structural steel. Analysis revealed that the low elongation of Y15 was the main reason for the cracking. To maintain production and solve the cracking issue, an annealing treatment was often added to increase the material's elongation and reduce hardness. However, this process introduced two key problems: surface carbonization during annealing, which was hard to remove and affected appearance quality, and softening of the material, leading to dimensional issues during riveting. This made the annealing method less than ideal. Through detailed analysis of the deformation during the riveting process, it was found that certain areas—such as the right-angled support of the end button and the abrupt changes in wall thickness—were particularly prone to cracks. These findings guided the redesign of the housing and end button structures. The improvements included increasing the height of the flange by 0.3mm, changing the angle of the end button support from 90° to 30°, and adjusting the rivet fixture to better match the modified housing shape. These changes significantly reduced stress concentration and eliminated cracking in actual production. By optimizing the design and understanding the mechanical behavior of the riveting process, the problem of sensor housing cracking was effectively resolved. This approach not only improved product quality but also avoided the drawbacks of traditional annealing methods. The theoretical analysis provided strong support for the practical implementation of these improvements, making the solution both effective and sustainable.

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